The properties of flame-cut edges, Nederlands Institute of Welding, Working Group 1931, Final Report 1973

NETHERLANDS

INSTITUTE

_OF

WELDING

WORKING GROUP

₁₉₁₃

The

properties

_of

_{flame cut}

edges

FInal

_report

May

₁₉₇₃

Technical

_report

on research

complementary

_{to the first}

programme

_{of the}

CECA

Committee "Fatigue et

NETHERLANDS INSTITUTE OF WELDING

WORKING GROUP 1913

The properties of flame cut edges

Final report May 1973

SSL 163a

Technical report on research complementary to the first programme of the CECA Committee "Fatigue et Constructions Types"

Institute of Welding by Working Group 1913.

This Working Group is composed of the following representatives of laboratories and industries.

H. Thomas president J. de Back T. Muller J.J.W. Nibbering C.J.J.N. Verwey R. Vonk T.J. Bos

- Laboratory of the Dutch-Railways (N.S.)

- Stevin Laboratory

Deift University of Technology.

- Kon. Ned. Hoogovens en Staalfahrieken (KNHS) - IJmuiden

- Ship Structures Laboratory Deift University of Technology

- Nedf Instituut voor Autogene Metaalbewerking (AVAL)

- Ship Structures Laboratory Delft University of Technology

Contents

Page

Object of the research 2

Lay-out of the research ₂

Steel used for the tests 3

14. Equipment used for cutting ₃

Tests ₅ 5.1. Heating tests ₅ 5.2. Temperature measurements 5 5.3. Cutting tests 6 5.14. Hardness measurements 7 5.5. Roughness measurements 8 5.6. Cold deformation 8 5.7. Microscopy 8 5.8. Fatigue tests g 5.9. Residual stresses _io Results ₁₀ 6.1. General ₁₀ 6.2. Measuring of temperature _io 6.3. Measuring of hardness ₁₂

6.14. Measuring of the roughness i3

6.5 Cold deformation

6.6. Fatigue tests 114

6.7. Microscopic investigation ₁₈

6.8. Residual stresses ₂₁

Summary of results 27

Comparison between the results of this investigation and Goldberg's

resulta (see 11W Doc nr. I-'483-72)

₂₈

Conclusions ₂₈

Object of the research

Flame cutting of parts of steel structures is frequently used in the fields of ship structures, bridges., cranes, etc. Up to now, it is often stipulated that the flame cut edges of important parts must be machined off. As a rule 2or 3 mm of the faces of the cuts have to be removed. This machining is time-consuming and expensive.. Instead of machining, in ship building use of a better steel grade is sometimes stipulated. The object of this research

is, therefore, to find a flame cutting method which can be used in practice at low costs and will enable us to use the cut parts without machining, in fatigue loaded structures.

Lay-out of the research

The main factors, interfering with the fatigue strength of flame cut edges, will be

- effects of the heat-input during the cutting i.e. hardness, structure and residual stresses

- the roughness of the faces of the cuts.

Both factors will depend on a number of variables, viz.:

a. steel grade

the steel used for the tests was Fe 52 C3 according to Euronorm 25-67, some preliminary tests were done with Fe '42 A, Fe 1+2 D and Fe 52 B

b.. plate thickness

-most tests were done with 25 min plate, some tests were done with 35 mm and 20 mm plate

running speed

mOst testspecimens were cut with a running speed of Circ.250 mm/mm; the influence of higher speeds i.e. 350 mm/min and '450 mm/min was checked plate temperature

the cuts were made in non.preheated and locally preheated material gases

the cuts were made with propane, the preheating flames were also fed with propane. A few testspecimens were cut and preheated with acetylene flames..

The testprogram was started by the search for the optimal conditions to obtain as low a hardness as possible. of the cut edge and as smooth a surface as possible. It appeared that preheatirig of the plate material had a favourable influence

-3-improved.

Therefore, an economic and practicable preheating method had to be found. Preheating with one or more preheating flames,, running ahead of the cutting nozzle at the same speed as the nozzle appeared to be an acceptable method,. Research into the number and size of the preheating flames, their position with respect to the nozzle as well as their influence on the plate temperature at the cutting spot required further experiments.

Some tests were done with two cutting nozzles,, one nozzle placed a bit ahead of the other. In this way, the heat input of the first nozzle will preheat the material at the second (final) cut. Two types were tested: one with two separate nozzles and one with a dual jet nozzle. The influence of the running speed

with the various set-ups was also checked.

After finding a usable preheating/cutting combination, giving acceptable results

with regard to hardness, micro-structure and roughness of the faces of the cuts, the influence of flame cutting on the fatigue strength was tested. Some fatigue tests were done on testspecimens, made under less favourable cutting conditions. A preliminary investigation was made into the influence of cold deformation

(straightening) and the influence of losing a cut on the fatigue strength of flame cut edges.

Throughout the research program, much attention was paid to microscopic inspec-tion of the faces of the cuts in order to get a better insight into the trans-formations' of'the microstructure in the heat affected zone of the edges.

Aresearch was also done into the. magnitude and the influence of residual stresses in the HAZ of the edges.

3. Steel used for the tests

Most of the research was done with steel plate Fe 52 C3 according to Euronorm 25-67. Initially, all tests were done with 25 mm plate., afterwards some tests were done with 35 mm and 20 mm plate.

The mechanical and chemical properties of the materials are assembled in appendix

1.

'4. Equipment used for cutting

Oxygen cutting machines

- for the manufacture of the fatigue test bars:

a single cantilever cutting machine guided by electronic line tracer (1:1); Griesheim type SMWF 1500.

- for all other cuts:

a portable motor driven cutting machine; Messer Griesheim type tiSecator S" (railguided).

Cutting blowpipes and preheating flames (heating blowpipes).

- cutting blowpipe

three-hose cutting blowpipe propane, manufactured by Hoek/Loos.

- preheating flames

one or two hand cutting blowpipes propane, 1-loek/Loos, type "Caliber".

one heating blowpipe propane, capacity about 900 1/h (propane), Hoek/Loos.

Nozzles

- cutting blowpipe

two-piece cutting nozzle propane with 8 slots for heating orifices size 20-5.0 mm, manufacture Hoek/Loos.

two-pieces cutting-nozzle propane with 16 slots for heating orifices size 20-50 mm, manufacture Hoek/Loos.

- preheating flames (heating blowpipes)

two-pieces cutting nozzle propane with 8 slots for heating orifices size 200-250 mm, manufacture Hoek/Loos.

two-pieces cutting nozzle propane with 16 slots for heating orifices size 200-250 mm, manufacture Hoek/Loos.

heating nozzle propane with multiple slots for heating orifices, pitchdiaineter: 6.2 mm., manufacture Hoek/Loos.

5. Tests

5.1. Heating tests

Heating tests have been carried ot with:

- two preheating flames side by side ahead of the cutting blowpipe - two preheat ing flames tandem wise ahead of the cutting blowpipe - one preheating flame, low capacity, ahead of the cutting blowpipe - one preheating flame, high capacity, ahead of the cutting blowpipe.

5.1.1 Two preheating flames side by side

Two preheating flames (cutting blowpipes with nozzle 200-250 mm, supply closed) preheat the plate on either side of the imaginary The distance between the two flames was ranged from 32 mm to 100

in figure 1, appendix 2.

5.1.2 Two preheating flames tandem wise

Two preheating flames as mentioned under 5.1.1 preheat the plate imaginary cut path.

The' distance between both flames, distance a, could not be taken 30 mm owing to the'dimensijon of the biowpipes.

The arrangement is shown in figure 2, appendix 2.

5.1.3 One preheating flame, low capacity

One, preheating flame as mentioned under 5.1.1 preheats the plate surface at the imaginary line of cut.

5.l.1. One preheating flame, high capacity

Instead of two preheating flames as mentioned under 5.1.1 only one preheating flame (from heating blowpipe) precedes the cutting blowpipe.

The gas and oxygen consumption of this flame is equal to the gas and oxygen consumption in case two preheating flames are used.

5.2. Temperature measurements cutting oxygen line of cut. mm, as shown surface at the smaller than

To determine the optimum distance a, a number of temperature measurements have been made. at various running speeds.

-5-For the plate thickness of 25 min these measurements have been made in accordance with the arrangement of the flames as mentioned under 5.1.1; 5.1.2 and 5.1.3.

in case of plate of 35 mm thickness the relationship between the influence of the preheating flame and the temperature reached in the material has been deter-mined only in accordance witI the arrangement as mentioned under 5.1.1+.

For the heating test as described under 5.l.l,a number of thermocouples are inserted at 2.5 mm from the underside of the test specimens.

Appendix 3 shows the arrangement of these thermocouples, which are connected with previously calibrated milli-ampere meters.

Each second a film shot has been taken of the dials of these meters together with a running stopwatch..

From these film shots a temperature - time diagram has been prepared. Vertical lines were then drawn in the diagram; these lines correspond with the different distances between cutting blowpipe and preheati.ng flames.

Further on in the report.,the distance between cutting blowpipe and preheating

flame(s) will be called -a-measure.

At the intersection of each of the a-lines with the temperature lines,the diagram gives the temperature reached at the underside of the plate at the moment at which the imaginary cutting blowpipe crosses the measuring-line.

An example of such a diagram is shown in appendix 1+; this diagram is prepared from the measuring results of an arrangement in accordance with 5.1.1. In this case the -b-measure. was 16 mm.

5.3. Cutting tests

5.3.1 Cutting tests, without preheating

With a cutting nozzle of suitable capacity for thickness of plate, several cuts have been made at a cutting speed of 250, 350 and 1450 mm/min.

5.3.2 Two cuts method

Two cuts were made simultaneously at a short distance behind one another.

When making the first cut, the material of the second (final) cut is preheated. The arrangement of the blowpipes is shown in figure 3, appendix 6.

5.3.3 The dual jet nozzle

Likewise two cuts were made simultaneously.

The distance between the cuts is smaller than in the preceding case, because the inner nozzle is provided with two cutting oxygen nozzle bores.

Figure , appendix 5 shows the arrangement, of the dual jet nozzle.

.3»4 Two preheating flames side by side and one cutting nozzle (blowpipe)

The tests were carried out at cutting speeds of .250, 350 and 1450 mm/min. varying the -a- and -b-measures in several combinations.

An example of the arrangement of cutting blowpipe and preheat ing flames is shown in figure 5, appendix 5..

3.5 Two preheating flames tandem wise and one cutting nozzle (blowpipe)

The tests were carried out at several cutting speeds. The distance between

cutting blowpipe and - looking in direction of cut - the first preheating flame,

-a-measure, depends on the cutting speed.

In figure 6, appendix 5, the arrangement is shown.

5.3.6 One preheating flame and one cutting nozzle (blowpipe)

These tests were carried out with a preheating flame of low or high capacity, during which the, cutting speed, was varied,.

Likewise, in this ärrangement of preheating flame and cutting nozzle, the -a-measure depends upon the cutting speed.

All above mentioned tests were carried out in material of 25 mm thickness.

Material of 20 mm and 35 mm thickness was only cut in accordance with the methods mentioned under 5.3.1 and 5.3.6 (preheating flame high capacity).

5.1-k Hardness measurements

Vickers hardness measurements were carried out on a sizable number of flame-cut edges.

The measurements were made on a surface with a 60-inclina.tion(l : 10.) with

res-pect to the length direction of the edge,

Each flame-cut edge specimen was investigated at the upper edge and lower edge

(1 mm under the plate surface) and in the middle, see . Appendix 6.

-7-At first an indentation load of 300 N was used; later this was reduced to 50 N when it was recognized that the hard surface layer was only very thin.

5.5. Roughness measurements

Roughness survey was made of many specimens, using conventional apparatus. At first only the R-values were recorded, later on both Ra and R-values were recorded, It soon became apparent that the Ri_value readings did not conform to

Ra: a14a2sa5.---a

n

the recorded roughness profile of the surface, owing to an inappropriate time-constant of the electronic memory of the apparatus. The values taken from the profile recordings are identified as Rn-values.

5.6. Cold deformation

-A number of -specimens were prepared -in order to investigate the tendency of the flame-cut edge to promote fissuring during -the straightening of as-cut strips and plates.

The speoimens were made both with and without preheating, and subsequently stret-ched. A microscopic investigation was made of the area 1 mm- under the plate

sur-face at the lower edge in order to establish the maximum strain at which no fissuring occured.

The paragraph 6.8.-5, deals with the influence of prestraining on the residual stresses in the edge, as evidenced by the fatigue behaviour.

5.7. Microscopy

The microscopic investigation of the flame-out edges was primarily intended to

gain some understanding of the complex micros-tructural system that

originates-from trans-formations at very hi-gh cooling rates in arather- thin zone along

the-flame cut edge

-9-Both conventional and electron-microscopic techniques were used.

5.8. Fatigue tests

After completing th preparatory test3 to get information abOut hardness,

rough-ness and micro structure, testspecimens for fatigue tests were made.

Initially, prismatic testspecimens were used. In viêw of the situation of the fracture in some of these specimens, it was decided to continúe with waisted specimens. Appendix 7 gives the shape and dimensions of these waisted specimens. Altogether, 13 series of testspecimens for fatigue tests were made, 12 series of 25 mm plate and 1 series of 35 mm plate. Table i gives a review of the series, some relevant data on the fabrication and the object of the testing.

Table i Review of fatigue testprogram

series plate thickness mm relevant data on fabrication object of testing NS 56 25 & V = 250; smooth

influence of two preheating flames on fatigue strength NS 62 25 machined edges fatigue strength material

NS 101 25 influence of one preheating

flame compared with 2 pr.fl. 250;

smooth

NS 110 H 25 250; rough influence of roughness NS 122 25 -- V 350; smooth influence of running speed

NS 129 25 -e V 250; extra rough influence of roughness NS 136 25 no preheating; V 250 smooth; prestretched

±nfJkience of cold working

NS 139 25 -e.v V 250;

smooth; prestret--ched

influence of cold working

NS

itl

25 -- V 250; smooth

losinga cut

influence of loaig a cut

NS 150 25 'no preheating;

V 250 smooth

influence non-preheated edges

NS 158 25

i

no preheating; V 250 smooth; bent 2%; rebent

influence of old working

z 2 preheating flames tandem-wise (200 - 250mm)

z 1 preheating flame (720 i/h) smooth z R ca 30 (mean value)

p

rough z R ca 60 ( " 't )

extra

1, z R ca 120( " " )

roughJ

V z running speed in mm/min

As mentioned before., initially an introductory research was performed. The results were used to check the influence of residual stresses on the fatigue strength. Therefore, the results are only given in 6.8.

5.9. Residual stresses

Residual stresses have been measured with the aid of strain gauges. The method as well as the results are given in section 6.8.

6. Results

6.1. General

In appendix 8, a review is given of the conditions of fabrication of the testspecimens as well as a summary of the results of various tests.

6.2. Measuring of temperature

Table 2 gives a brief summary of the r.esults of temperature measurements at the bottom face of the plates..

The length of time between passing of the preheating flame(j) and the maximum temperature at the bottom face of the plate, being reached js appr. 25 sec for 25 mth plate and appr. 35 sec for 35 mm plate, irrespective of the preheating flames used.

To make an optimal use of the preheating temperature, the cutting _{burner has}

series plate thickness .

mm relevant data on fabrication object of testing NS 166 25 V z 250; smooth bent 2%, rebent

influence of cold working (stretching)

ll

-to pass when the temperature is at its maximum. With the plate thickness tested, this requirement is met if

afj V

(mm)

in which

a distance in mm between preheating flame(s) and cutting nozzle

d plate thickness

V running speed in mm/min.

Table 2 Summary of results of temperature measuring

plate gauge in mm preheating method running speed mm/min maximum temp in 0C at bottom face of plate at piace of cut

spacing bin mm (with two preheat ing flames side by side only)

25 250 350 '450 230 not measured " " 16 16 16 two preheating flames (200-25 0 mm) side by. side 25 idem 250 350 '450 160 not measured " 25 25 25 -25 idem 250 350 so 110 . not measured " II 50 50 50 25 two 250 350 '450 330 250 180 -preheating flames (200-250) tandem wise 25

-- one

preheating flame (200-25.0 mm) 250 350 '450 180 150 130 -. -25

:-one

preheating flame(heating blowpipe) not measured . -.

-6.3. Measuring of the hardness

Table 3 gives a summary of the hardness of the faces of the cuts. For each

cutting method, some typical values are given.. Each value is the highest hardness, measured at one face of a cut. The values for each testspecimen can be found in appendix 8.

Table 3 Summary of the results of hardness measuring

plate gauge in mm preheating method running speed min/min maximum temp. in 0C at bottom face of plate at place of cut spacing b in mm (with two preheat ing flames side by side only)

35 1 250 350 450 128 102 82

-

e-preheating flame (heating blowpipe) plate gauge in mm cutting and preheating method running speed mm/min

maximum hardness of the face of the cut HV 5

(each number represents one specimen)

25 non prehea- 250 423-435-'441-524

ted-

350 593

450

781-546

25

_S.f-

300 460-420-460 method w.2 350 487 cuts 450 478

8550648954,0

25 300 390-407 aual jet 450 524-450 nozzle 630 460-574 25 2-preh.fl.

bi6

250 250

b=25

250 343

b50

250 403

6.4. Measuring of the roughness

The Ra_values of the testspecimens as far as measured, are given in appendix 8. The R-value, if not mentioned in appendix 8, can be calculated roughly, by multiplying the Ra values with 4.

The R-values, as far as' known, are given in table 8. Besides, the Rvalue per series of testspecimens for fatigue tests, are also given in table 4.

A picture was made of some typical faces of cuts. These photo's are reproduced,

together with a roughness diagram and the Ra Rt and R values, in the appendices

9 and lO.

N.B. Irregularities due to losing a cut were kept out of the measuring of the hardness.

Appendix 11 gives a review of the roughness of a number of faces of cuts, made without preheating in works of various firms.

-13-plate gauge in mm cutting and preheating method running speed mm/min

maximum hardness of the face of the cut HV 5

(-each number represents one specimen)

25 $G-. 2 25-0 245-265-296-283--371-293 preheating 350 409-353 flames tandem wise 450 401-386 25

-1

260 396

preheating 360 not measured

flame 450 " n (low capa-city) 25 1 250 310-325-381-317-306 preheating 350 310-441-353-454-412 flame 450 593-454-460 (high capa-city) 35 non prehea-ted 250 5,16 35 -Gø- _{250 381} 20 non prehea-ted 250 516 20 250 286

6.5. Cold deformation

Table 4 gives the strains due to an applied tension, at which cracks only just

failed to occur in the faces of the cuts. Cracks were only found in the

marten-site layers, if present, along the face of the cut. The depth of the cracks was

equal to the thickness of the martensite layer.

Table L _{Results of strain tests}

Prior to fatigue loading four series of testspecimens (NS 136, NS 139, NS 158 and NS 166) were bent in the direction of the width to a strain of 2% and then bent back.

As part of the introductory research, some specimens were stretched to a plas-tic strain of 1%, 3% and 5%, to check the effect of eliminating the favourable residual compression stresses on the the fatigue strength.

6.6. Fatigue tests

The results of the fatigue tests, done in the final program, have been summarized in table 5.

More details about fabrication, hardness etc. can be found in appendix 8. cutting method running speed mm/min total strain just before cracking martensite thickness mm layer height mm % not preheated 250 1,5 °' 0,02 ".. 19 O-.- 1 prehea- 250 2,5 ' 0,01 2 ting flame (high capaci-ty)

Table 5 Results of fatigue tests -15-serial nr; type test-specimen nr. plate gauge mm face of cut stress at fatigue tests -number of cycles lO6 starting point of crack amin2 _{at failure no failure}

N/mm

NS 56 NS 56 220 - 2,0

-NS 56A 300 0,35 - central part

NS 57 300 0,65 - Id NS 58 25 smooth 300 1,25 - clamps NS 59 300 0,18 - stamped number NS 60 260 1,1 - clamps NS 61 260 0,65 - id NS 62 NS 62 300 0,70 -. central part NS 63 260 1,50 - id machi- NS, 64 machined 180 - 5,0 -ned NS 64A 25 260 2,05 - id NS 65 300 0,60 - id

ÑS66

220 - 2,04 -NS 67 260 0,18 stamped number NS 101 NS 101 200 - 2,2,6 -NS 101A 246 - 2,00 -NS 102 246 - 2,19

NS 103 25 smooth 280 0,74 - central part

NS 104 260 0,98 - id NS 105 250 0,80 - transition NS 106 247 1,29 - id NS 110 NS 110

25

2,02 - transition NS 111 243 1,06 - id

NS112

223 - 2,0 -' NS 113 25 rough 243 0,26 - irregularity NS 114 234 - 4,1

-NS115

245 - 2,9 -NS 116

24

0,23 - irregularity NS 122 NS 122 245 0,54 - transition NS 123 245 0,61 - íd NS 124 225 - 2,0 -NS 125 25 smooth 235 1,02 - clamp

Table 5 continued serial nr; type test-specimen nr. plate gauge mm face of cut stress at fatigue tests

asmax_

number of cyclus io6 starting point of crack at failure no failure N/mm NS 126 235 1,52 - hole in lug NS 126A 235 - 2,0 -

-e.-NS127

-NS 129 NS 129 249

l03

- irregularity NS 130 229 0,92 - id NS 131 NS 132 25 extra rough NS 133 NS 134 NS 136 NS 136 225 0'40 - central part

no pre_

NS 137 200 0,'46 - irregularity

heating

NS 138 25 smooth 160 - 2,02 -NS l38A 180 - 2,16 -NS 138B 200 - 2,27 -NS 139 NS 139 25 smooth 200 - 2,0

-NS 10

180 - 2,2 -NS 140A 25 '' smooth

200'

- 2,0 -NS 1LI.OB 220 ' 1,28 - irregularity NS 141 NS 1h41 2i'. 0,17 -NS 142 204 0,48 -NS 143 164 0,51

-NS144

124

-

2,0 NS 144A 25 irregular- 144 1,36 -NS 145 ities due 154 - 2,01 -e.--NS 1146 to losing a 1144 - 0,7 NS 147 NS 148 cut 134 134 -2,15 2,0 NS 1L48A 154 1,79 -NS 150 NS 150 220 - 2,95

-nopre-

NS 151 240 - 2,55

-heating

_{NS 152} ' 250 1,07

-

clamps

Table 5 continued

oo

2 preheating flames, tandem wise (200 - 250 mm)

i preheating flames (720 ./h)

Clamps : crack in a lug of the testspecirnen (between clamps of testing machine)

transition : crack in transition curvé of specimen (see appendix 7)

irregularity : crack started at irregularity due to losing a cut.

-.17-serial nr; type test-specimen nr. plate gauge mm face of cut stress at fatigue tests o -max number of cyclus 10 starting point of crack

min2 at failure no failure

N/mm

no NS 153 25 smooth 260 - 2,60

-prehea- NS 15'4 ₂₈₀ 0,94 - central part

ting NS 155 270 - 2,90

-NS156

- - -

-NS157

- - - -NS 158 NS 163 243 - 2,1 -no prehe a -ting NS 164 25 smooth 228 - 2,2 -NS 166 .ÑS 166 228 1,6 - hole in lug NS 167 25 smooth 237 - 2,7 -NS 169 223 2,1 - idem NS 203 NS 203 270 0,32 - transition NS 204 240 3,2 2,0 clamp NS 206 35 smooth 270 0,32 - transition

NS207

- - - -NS 208 240 2,4 2,0 _clamp NS 210 250 0,88 - transition

Table 6 gives the fatigue strength for 2,0 x io6 _{cyclesper series.}

Table 6 Review of fatigue strength per series

6.7. Microscopic investigation

Owing to the 'high transient temperature of the flame-cut edge, microsiructural changes will occur in a thin layer along the cut surface. Although the cooling

rate is a decisive factor in these changes it is not sufficient to explain all the

features observed.

Apparently, the final micro-structures are determined by more than one important factor only.

For instance, it was shown by Goldberg (1) that carbon, originating from the material thát has been burned away in the cut,, diffuses into the flame-cut edge material.

A thin layer is formed, about 0,03 to 0.07 mm thick', consisting of hard

non-etching mar-tensite, accompanied at times by some retained austenite, and troostite of a relatively low hardness.

The martensite hardness amounts to 800-900 HV, the hardness of the troostite phase is about 300 to 1+50 HV.

The approximate size of the martensite and troostite zone is given in the follo-wing sketches.

(i.) "Welding in the Wor],d" 7(8-1971 serial nr. plate gauge mm roughness Rp m V mth/min min. fatigue strength in N/mm2 remarks preheating method

N2x106

cycles NS 56 - 250 appr 250 smooth NS 62 - - appr 220 machined

NS 101 appr 135 250 appr 240 smooth

NS 110 appr 150 250 appr 230 rough

NS 122 80-140 350 2140 smooth

NS 129 appr 160 250

< 230

extra

roug-NS 136 NS 139 25 -250 250 appr 200 appr 200 lsmooth, J stretched 2% not preheated'

NS 141 - 250 appr 135 losing a cut,

NS 150 ' - 250 270 smooth. not preheated

NS 158 - 250 240 240 smooth bent 2% u NS 166 - 250 )rebent NS 203 35 5Ó-110 250 21+0 _smooth'

WITHOUT PREHEATING

25

WITH PREHEAT:INÒ

The amount of troostite is dependent on the plate temperature before cutting. A .face of a cut that has been preheated possesses a surface layer consisting almost entirely of troostite, except for a small ridge of martensite at the bottom edge. The maximal height of this small ridge is 2 mm for all the plate thickness that were investigated. The height of the martensite zone in flame-cut edges that were not preheated amounts to approximately 19 mm for the 25 mm-plate and to approximately 29 mm for the 35 mm-mm-plate.

The photographs 1, 2 and 3 (Appendix 12) show how the structure of a flame-cut edge depends on preheating. The cutting speed was 250 mm/min. On these photographs the layer of non-etching martensite is clearly visible. Photograph 2 shows that the preheated flame-cut edge consists primarily of troostite. This photograph was taken 2 mm from the bottom edge where some martensite is still present. Nearer the bottom edge the martensite increases, see photograph 3, taken QL mm from the bottom edge. Photograph 2 clearly distinguishes two layers of troostite, a light one and a darker one, separated by a straight boundary. Electron microscopy re-vealed that the carbide.morphology. in these two layers is different.

Photograph i and 3 also sflow a straight boundary. It is believed that this boun-dary divides the material that has not been molten in any stage from molten and solidified material because:

a. _{the straight boundary often lies between two different phases (photögraph 1,}

martensite and troostite, photograph 2, two different forms of troostite and 29 -19-- -19--. _{fusion line} ledeburite =martensite/troostite martensite 3 _ferrite

low carbon martensite or Widmannstätten-ferrite

= Troostite I 35 Troostite II

photograph 3, martensite and troostite)

b. the non-metallic inclusions suddenly cease to exist beyond this boundary,

going from plate to edge.

In the subjoined sketch the percentage is given of a number of elements in the surface layer of a preheated flame-cut edge which correspond with the structure of photograph 2, as found with a röntgen micro-probe analyser.

Percentage C,Mn and Si of the plate material

-- Mn+Sj

WIDMANN

STÄTTEN

-FERRITE

M AR

-TEN

SITE

TROOST IT E

_n

1.25-1,5% C

o% Mn+Si

T ROOST IlE

I

43% C

LEDEBURIT

The width of the martensite/troostite zone corresponds neatly with the carburized layer at the surface. The fusion line is characterized by the transition of a zone with a constant amount of C, Mn and Si (the "molten" layer) to a zone were the percentages of these elements vary, thus a layer that has been subjected to a certain degree of diffusion of these elements towards (C) or from (Mn and Si) the "molten" layer..

From the schematic sketches of the edge-structure given earlier, and also from the photographs i to 3 the existence of small zones of ledeburite òn the as-cut

surface became evident. Cementite needles sometimes protrude from these zones

into the underlying material, see photograph 2.

It must be noted that the ledeburite always is contiguous with troostite and never with martensite.

Progressing further into the material, going from the martensite/troostite _layer,

pre-

-21-heating was applied,, this zone cooled öff to a well-etching martensite/bain.ite structure.

At times, however, depending on the structure and chemistry of the plate as

well as on the location on theflame-cut edge Widmannsttten-ferrite was

for-med.

Invariably when no preheating was applied, a Widmannsttten-feriite was formed.

Usually the structure at the top edge consists mainly of ferrite. Goldberg (2)

attributes the formation of this structure to the decarburatation of the steel caüsed by the heating flame of the cutting torch.

The out line, of the microstructural features as given above is typical for this investigation.

However, sorne deviations did occur among the great number of specimens that were investigated, especially at the extremity of the bottom edge, where the martensite/troostite layer is very thin. Small differences (grain size, banded

structure) may have a sizable effect in this area.

The upper boundary of the martensite/troostite region, nearthe transition to the ferrite zone, is. also difficult to incorporate into a single scheme.

The presence of troostite in the martensite/troos-tite layer (the carburized layer) was investigated with special interest. The co-existence of adjoining regions of hard martensite and "soft" troostite still remains particularly difficult to explain as both have the same high carbon cöntent and have been subjected t the same high cooling rate. The formation of troostite is clearly favoUred by preheat ing.

Moreover, it may be said that the formation of troostite proceeds in a direction

away from the flame-out edge, whereas the martensite most frequently occurs on the plate side. of the martensite/troosti-te zone. This may indicate the diffusion

of an element with diffusjoi characteristics different to that of carbon that

exerts a great influence on th transformation behaviour.

6.8. Residual stresses

6.8.1. The measurement of residual stresses due to flame-cutting

One of the important factors determining the fatigue behaviour' of flame-cut specimens is the residual stress-pattern.

The Ship Structtres Laboratory has developed a 'simple method, with which the stresses below 0,1 mm distance from the surface can be estimated.

The reproducibility of the results obta.ned _{p tó this moment is very}

satisfac-tory. But extrapolation to a depth of 0 mm (flame-cut surface) in order to

of magnitude of the edge stresses.

Basically the method consists of applying small length strain-gauges to the

flame-cut edge and gradually sawing ä notch as close as possible. to the end

of the gauges, (fig. 1)

Strain gauges

No ti

fig. 1.

Due to the notching, the stresses are able to relax; gauges of 2, 3 and 5 mm length were used.

For the conversion of the measured strains, _{- at various notch depths -, into the}

actual residual stresses, calibration curves are needed, representing gauge

output as a function of notch depth for a known stress-field. They were obtained by gradually sawing a notch near applied strain gauges, in a tensile stressed prismatica]. bar.

The before-mentioned curves,, obtained from gauges _{on flame-cut specimens, could} then be corrected as illustrated with the following example..

Let the output of a gauge on a flame-cut specimen diminIsh by 70 micro-strain while the notch is deepefled from 0,2 to O, _{mm, and let the output of a similar}

gauge on the prismatical bar by the same process diminish by loo micro-strain.

Then the average residual stress in the flame-cut bar between 0,2 and

_{04 mm}

distance from the edge will be 70/100 times the noindthal _{stress in the prismatical} bar; this value is plotted at. a notch depth of 0,3 _{mm, being the average of 0,2}

and 0,14 mm. .

Of course the gradients of stresses in the flame-cut bar and the calibration bar are quite different, and this will influence the accuracy of the estimates. But

influence will be of second order.

Figures 2a to 2d show directly recorded values for 3 steels '42, flame-cut by the Dutch Steelworks (Hoogovens) and one. st. 52,, flame-cut by Aval under care-fully controlled conditions..

Figures 3a-b are calibration curves for 2, 3 and 5 mm strain gauges near the notch and one 5 mm gauge situated at 10 mm from the notch.

It has become standard practice to use 3 mm gauges for cases where especially

information concerning the outer layers is needed. A 5 mm gauge near a notch is

used for the residual stresses in a layer of about 5 mm deep.

A gauge situated at 10 mm from the notch is used in order to obtain an idea about the whole residual stress pa.ttern, (up to 15 mm from the surface).

Figures 4-7 finally show the obtained residual stress patterns..

It can be seen that for material Fe 52 (Hoogovens-cut) appreciable compressive

stresses (up to 90 N/mm2) in a layer of _{max. 0,4 mm deep., seem to be present.}

The "A".rait'-cut bars (St. 52 NS '47,) have been provided with gauges at the upper and lower edge. It is evident that when the average stresses (.at half plate thickness) are small., nevertheless appreciable edge stresses can be present. At

the upper edge, where the temperature during cutting was hthghet, the compressive stresses are very pronounced.

The figures .2-7 mainly serve the. purpose of illustrating the procedure of evalu-' ation of the strain gauge measurements and.of showing characteristic results. All other data about residual stresses have been summarized in figures 1'4 A-I. The measuring points have been left out for convenience.

6.8.2. The influence of the residual stresses on the fatigue behaviourt

In table 7 and fig. 8 the endurance limit, the hardness and various flame-cut parameters are' given of those bars for which the residual stresses were measured. The most important aspect, viz. the relation between residual stresses and fatigue.

strength., is visualized in fig. 9. . . . .

The figure strongly suggests that the more compressive the residual stresses, the

higher the fatigue-strength is. On the other hand residual tensile stresses

reduce the fatigue-strength. . . .

-23-6.8.3. Residual stresses and hardness.

Figure 10 shows the relation between the extent of the zone in which the residual stresses are compressive., and the hardness,, in fig.. 11 the stresses themselves and hardness are combined. Both figures show a tendency of lowering hardness at increasing compressive stresses.

This is contrary to what was expected. The presence of residual compressive stresses is generally associated with the presence of martensite in the region concerned, because the volume of martensite is greater than that of ferrite-perlite.

The depth of the compressed region is up to 0,5 mm thick; this differs from the values mentioned by Goldberg, viz. 1-2 mm. But these were probably printed by mistake, because Goldberg's figure 18, from a paper by Ruge and Schim6iler, shows a compressed zone of a few tenths of millimeters.

6.8.4 Comparison between residual stresses measured with the aid of strain gauges and sawcutting and with the aid of R6ntgen-diffraction.

Table 8 shows results of measurements of residual stresses at the outside of a flame-cut bar measured with the aid of Rt5ntgen diffraction. Figure 12 compares some of these results with those obtained with the aid of strain gauges. It is

quite remarkable that both results are opposite in either case The only possible

explanation seems to lie in the fact that with the R6ntgen diffraction method stresses are measured at extremely small spots, while the other method gives

average values over regions of afew mm in magnitude. For that reason the latter

results are certainly of greater practical value than the former. This has been substantiated by the results of the fatigue experiments mentioned in 6.8.2., (fig. 9).

Also the results of some experiments with prestressed bars (see. 6.8.5) are only, comprehensible when the residual stresses measured with the strain gauge method are the relial5le and real ones.

6.8.5. The influence of prestraining on the effect of residual stresses from a

fatigue-point of view.

Some specimens were prestrained 0,5%, 1% or 3% at temperatures of -10CC or -30°C.

Such treatment eleminates the residual stresses, and may give rise to small cracks in the hard flame-cut surface.

When in the.outer-layer compressive residual stresses are present,, the effect of prestraining may be expected to be unfavourable.

When tensile stresses are present it may be beneficial, although this may be counterbalanced by the development of smàll cracks..

The latter will manifest themselves more clearly in the case of larger strains (larger probability of cracking) although., if cracks should initiate' at low strains (f.i. 05%), prolonged plastic straining up'to 3% may be more or less

beneficial (overstressing influence). . ,

Material Fe 52 suffered clearly from the prestraining as is in line with the presence of large compressive residual stresses at the, edges (fig. 13a)

But it is remarkable that prestraining at 1% and 3% reduced' the strength far more

than at 0,5% because in no case had cracking been observed after the prestraining.

For St. 42 grade A, (fig. lSb) the straining had little effect, which conforms with the fact that only small compressive residual stresses were present at the edges.

Table 7

-25-Bar no. thick-ness mm endurance limit 6 (2.10 ) (N/mm2) ' res, stresses at 0,1 mm below surface (lower edge of bar),, . (N/mm) speed of . . cut ting (mm/min...) . pre-heated . . . hard-ness HV 30' NS 2 NS 15 NS 60 NS 62 NS 103 NS 117 NS 122 NS 205 NS 209 25 25 ' 25 25 25 25 25 35 . 35 '200 -230 ' 230 24:0' 230 230 240 240 + 100 + 173 - 78 ' - 22 - 184 ' - 55 .- 29 - 272 , 455 413 ' 250 . plane 250 250 350 25ó 250 n'o no ' yes -yes ' .yes yes ' yes yes 425 481 296 - . 3i7 306 396 380 .380

Table 8

Results of measurements of residual stresses by R3ntgen-diffraction.

Test piece HV stress

N/mm2

interval ± N/nim2

observation

30 5

Ns-lS A - 200 50 A upper side of edge

Ns-ls A 277 - 230 50 B half plate thicknéss

NS-15 A - 190 30

NS-15 A - 190 20 + tensile

NS15 B

8l - 90 30 - compressive

NS-15 B - 70 20

NS-23 A n.m. + 80 50 The intervals are based on

NS-23 B 311 + 370 20 1 a (standard deviation)

NS-7 B

236 + 230 10

NS-60 B 25L + 220 20

3 -c

u

.4-I

o

z

0.5

0,4

0.2 0

Material: Fe.52

Hoogovens cut

5-Strain gauges

2mm

+60 +40 20

Material: Fe.42grade.A

Hoogovenscut

Strain gauges

2mm

Material: FOE 42grade. D

Hoogovenscut

Strain gauges

2mm

20+140 +120 +100 +80 +60 +40 +20

0

+160 +140 +120 +100 +80 +60 +40 +20

a

Stress relaxation (N/mm2)

FIG. 2a-2d STRESS RELAXATION DUE TO NOTCHING IN FLAMECUT SPECIMENS.

Material: FOE52(NS47)

AVAL cut

Strain gauges

5mm

I

I Strain

gauges

\

3mm

s £

t

¿À

I.'

+60 +40 -i-20

0

20

0,4 0,2

o I I

+10

+20

+30

+40

+50

+60

+70

+80

+90

+100

Stress relaxation (N/mm2)

2 1,5

i

02

O

r.

u -. .. .

.

/

/

-

070 0

-

0

/000

'.0 0

.1.

+10

+20

+30

+40

50

+60

+70.

Stress retaxation (N/mm2)

/

000/0

/

/

CN

/

J

e

z

-X T-1I

-,

I

1

10

Strain gauge N! i

113

fl/V

3mm 5mm

10 9 8 7

FIG.3b STRESS RELAXATION FOR STRAIN GAUGES, DUE TO NOTCHING OF Â STRESSED BAR.

0

+90

+100

+110 +120

(

2

1;5

E E w -c

o

4-,

o

z

0,5

0,2 I I I I

.

+200

+150 +100

+50

0

-50

-100

ResiduaL stress (N/mm2)

FIG.4 RESIDUAL STRESSES AT VARIOUS DISTANCES FROM FLAME-CUT EDGE

+250

+200

150

100

50

0 20 40

Residual stress ('N/mm2)

FIG.5 RESIDUAL STRESSES AT VARIOUS DISTANCES FROM FLAMECUT

EDGE IN Fe.42 GRADE.A MATERIAL.

1,5

0,2

o

I I I _0,1

250

+200

+150

100

0

ResiduL stress (N/mm2)

ur

FIG.6 RESIDUAL STRESSES AT VARIOUS DISTANCES FROM

FLAME-ÒUT EDGE IN Fe.42 GRADE. D

MATERIAL.

(MEASURED IN TWO DIFFERENT SPECIMENS)

t

0,5w

E

04

I Q. .c

o

.4-,

o.

z

.s.

Lower edge

(. £

x)

115

upper edge

(o

a +)

1e

i

+200 +180 160 +140 +120 100 80 60 +40 +20

0

-20 -40 -60

-

Stress (N/mm2)

FIG.7 RESIDUAL STRESSES IN A FLAME-CUT BAR AS MEASURED WITH

THE AID OF STRAIN

UGES NEAR GRADUALLY DEEPENED NOTCHES.

Fe.52 (NS 47) AVAL-CLJT(MEASURED IN FOUR DIFFERENT SPECIMENS.)

e-

-E

z

-C .4-a

a-

-100--V -C

u

.4-'

o

C E E O

D

.4-J

fi

n

'n w

+100--

_'i.

0

'n a'

+200-

250-NS-2

NS-15

NS-60

pLaned

NS-62

n

NS-103

FIG. 8

RESIDUAL STRESSES OF DIFFERENT TESTBARS.

pLaned

'N-62

NS-hl

NS-103

NS-209

NS NS

NS-2

i 122 117

E200

-E

z

-C -I-'

150-a' -o-'

fi

u-O I I

+200

+100 0

-100

-200

-300

ResiduaL stress at 0,1 mm notch depth (N/mm2)

FlOE 9

_{RESIDUAL STRESS VERSUS FATIGUE-STRENGTH}

NS-205

NS-209

500

400

300

100

=

200

I I I

+200

+100

0

-100

-200

-300

Residual stress at 0,1mm underside (N/mm2)

FIG. 11

-

NS-15

o

0M NS- 122

o

NS-209 NS- 205 NS-103

o

NS-ui

o

o

NS-60

o

>

I

-e

(A VI C

L-I'

0,1

500

400

FIG.

0,2 0,3 0,4 0,5 0,6

Area of compression stress (mm)

10

- NS-ls

o

NS-2

o

NS-122

IO

I _NS-103 NS-117

_o

o

o

NS-60 0,7 NS-205

o

NS- 47

NS-60

-200 -100 0 E +200 .eJ _C. +100m

I'

mOE

w'-100

. +200

300

Residual tstress:(SCL (N/mm2 )(Strain gauges

NS-15

-100

-200

FIG.12

RESIDUAL STRESS .(tN.O.) VERSUS

300

260

220

180

MateriaL: Fe.52

PRESTRESSED BARS

O AS DELIVERED

00

3% eLongation -1O

eLongation _100

3% eLongation

_í7

%eÌongation 30°

1% eLongation

1O0

Number of cyctes(N)

FIG.133

_{FATIGUE RESULTS OF FLAMECÚT AND PRESTRESSED BARS. (COMPLETE FRACTURE)}

Material: Fe.42 grade A

PRESTRESSED BARS

O AS DELIVERED

I I 106

Number of cycies(N)

FIG.13

FATIGUE RESULTS 0F FLAME-CUT AND PRESTRESSED BARS. (COMPLETE FRACTURE)

0,5% elongation

'ici,

elongation -10°

o

1% elongation

E015%

elongatión -30°

260

220

180

156

NS-60 Gauges 3,4,7 an flame side FIG. +300 +250 200 +150 +100 +50 ResiduaL stress (N/mm2) FIG.

fLamey notch notch

side _I

_il

5

41

3 4.

\ I5

'

notch notch

I

U 5 4 GaugeS 12,5and 6 dG

_____

₁

;II

NS-103 I I _i

i

'1 +200 +150 +100 +50 0 -50 -100 -150 ResiduaL stress (N/mm2) E V u 4.

fLame_V notch notch

cide

_I

I

NS- 117

fLame notch notch side

I

3E FIG. 14F câ. 9e

.

-j,0,

6-5 NS- 15 FIG. 14B +250 +200 150 +100 +50 0 ResiduaL stress( N/mm2) Gauges 5and6 Ga

notch notch

I

3E +250 +200 +150 +100 +50 0 -50 -100 ResiduaL str.ss( N/mm2) FIG. I

11

.2s

+250 i200 +150 +100 +50 0 ResiduaL stress(N/mm2)

5-4E

-C 2 -C u I 4 o

z

- 5

-

0 -100 -150 250 +200 +150 100 +50 ResiduaL stressCN/mm2) FIG.

l4

0 -50 -100

FIG. 14G +300 +250 +200 +150 +100 +50 0 -50 -100 Residual stress ( N/mm2) 5 3 2

ri

flame y notch notch

side

i

_ii

f tame

side notch notch

r

n

au95

i-200 +150 -i-100 -i-50 0 -50 -100 -150

ResiduaL stress( N/mm2)

FIG. 14H

25

NS- 209

200 150 100 50 0 50 100 150

ResiduaL stress (Nimm2)

FIG. 141

5.

4 E -c

2 ..

_Q' ills --C

i

_J

u e

z

0,5

7. Summary of results

- The presence of hard transformation structures in the HAZ of flame-cut edges

is limited to a thin layer (<0.1 mm).

- Preheating before cutting of Fe 510 steeiplate has favourable influence on

the hardness and the structure of the HAZ of the flame-cut edge.

The hardness will not exceed 350 HV, providing the temperature at the bottom o

face side of the plate reaches at least 120 C.

it is quite feasible to apply a preheat by means of a buvner that precedes and is coupled to the actual cutting torch. The optimal distance between

the preheating flame and the cutting torch is dependent on the plate thickness and the cutting speed and is determined by the requirement that the temperature at the bottomface of the plate should have reached a certain value (e.g. 120°C) before the cutting torch arrives. Within the range of thickness inthis in-vestigation this requirement is met if

a- V

mm

whereby a is the distance between the preheating flame and the cutting torch,

d the plate-thickness in mm, and V the cutting speed in mm/min.

The microstructure of the HAZ of a flame-cut edge is influenced to a great extent by the changed chemistry of the material in this zone, and by the cooling rate.

The change in chemistry is caused by selective oxydation of some elements. At the surface there exists a layer, the outer part of which was in a molten

state during cutting. During that period an increase in carbon content and a decrease of the manganese and silicon contents are observed.

The fatigue strength of plate material with flame-cut edges is not lower as compared with plate material with machined edges.

Irregularities in the cut appearance greatly diminish the fatigue strength, depending on the naturé of the irr.egulariy.

- _{Within the range of roughness covered in this investigation only a slight}

difference in fatigue strength was observed.

Specimens that were cut without preheating exhibit a fatigue strength that is

slightly higher as compared to that of preheated specimens, providing _the

specimens were nöt subjected to cold stráightening prior to testing. If the

latter applies, the fatigue strength is practically the _{same in either case.}

-27-Conclusions

The results of the fatigue tests are The nunther of specimens and the fact strength, quite frequently fracture sectional changes of the specimens.,

6

fatigue strength at 2.10 cycles.

Fatigue strength in N/mm2 at 2.106 cycles

summarized in the subjoined survey. that, because of the high fatigue occurred in the grips and on cross-allow only for a rough estimate of the

Comparison between the results of this investigation and Goldberg's results (see 11W Doc. nr. I-'483-72)

- Preheating the material prior to flame-cutting results in a HAZwith

considerable léss martensite as compared with the HAZ of specimens where no

preheat was applied.

The martensite if any, in preheated edges is relatively easy ánd cheap to

remove.

- The fatigue strength of flame-cut Fe 5i0-C3 plate is rernak'kably high, providing there are no irregularities inthe cut appearance.

- To avoid a 30 to 0% decrease of the fatigue strength it: is necessary to

prevent., respectively to remove, all irregularities in the cut appearance.

- Without preheating prior to cutting,, the fatigue strength is.slightly higher

as compared with preheated specimens.

However, the deterioration caused by cold straightening is greater. in the case of non-preheated edges.

After straightening there is hardly any difference left between preheated

and non-preheated specimens. The explanation of these phenomena is _{that high}

machined flame-cut

non preheated preheated

smooth prestrained smooth normal prestrained with irregularities

200 ca.270 ca!200 ca.2'l-O ca.230 ca.200

<150

Surface condition of the flame-cut edge

Fatigue strength in N/mm2 at 2.10 cycles:

Goldberg NIL WG 1913 noi preheated non preheated preheated

machined smooth cut normal cut 300 290 250 200 270

-20

230

residual compressive stresses exist in non-,rehea-ted iùim-cut edge sdeii. Both preheating and straightening diminish these stresses, and thus the fatigue strength.

Mechanical properties and chemical composition of the steel used. plate thickness (mm) 25 20 35 lot I II III IV KNHS NS I tensile strength (N/mm2) 555 561+ 562 596 583 561 yield stress (N/mm2) 371 385 383 1+12 380 351+ elongation (L 5,65VT) (%) 21+,9 29,7 28,5 28,3 27,3 2'+,6

notch impact fracture

-o energy (190-V; transv; O C (J) 76 61 71+ 88 51 75 C (%) 0,16 0,20 -0,18 0,21 0,20 0,16 Mn (%) 1,30 1,31+ 1,33 1,49 1,+7 1,40 Si (%) 0,50 -0,37 :0,37 0,33 0,'+O 0,33 P (%) 0,025 0,O6 '0,021 0,015 0,017 0,017 S (%) 0,020 0,019 0,019 0,013 0,017 0,025 N (%) 0,007 -0,005 0,005 0,0060,005 0,005

IMAG [NARY

- - - - -

_{LINE OF CUT}

IPEHE

ATINO FLES

IM AGI NARY

LINE OFCUT

DIRECTION OF C

- DIRECTION OF CUT

PREHEATING FLAMES

APPENDIX 2

/

a

h4.

f2,5

O POSiTONOP

THERMO-COUPLES

PRENEATING FLAME

1wtROCOuPLE8

AT THE SOTTOM

£DGEÓF THE

PLATE

b

mm x mm y mm

16

50

25.15

8

25

8

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f direction . Pii.4 b L direction st prebeating f 1... dir.ctio of e t

pr. nomi.

j £11.3

FACE OF CUT

APPENDIX I

POSITION OF HANONESS

(90) WIDTH OP THE SPECIMENS

WHICH WERE PRESTUTC.HED 2%

J.. SESIS NL 130 and 139

TMANSITIONCUVE ACCORDINO T0 SALIT

PLATE THICKNESS 25 or 35mm

1000

225 225

APPENDIX 8

Review of cutting conditions and test results

non preheat. ut without preheating

cut with two blowpipes

cut with dual jet nozzle -: cut with preheating by one preheating flame (low capacity)

r cut with preheating by two preheating flames side by side (low capacity)

inentification cutting conditions results of the tests

type object plate number cutting preh. kind cutting preheating gas supply rUnning a/b temperature maximum roughness

of of gauge of nozzle flame(s) of oxygen oxygen supply £/h speed measure at hardness of

test test. mm specimen type type gas ress. supply £/h preh. cutting mm/min mm place of HV 5 face of

ato L/h preh. cutting flae nozzle Cut the cut

flame nozzle -R um -a NS 48 5 2940 _f 600 4 150 250 -52Ö 4,5-7,Ö

ÑS 91 LOOSCO not propane 3 ¿45 3590 not 600 150 257 - 524 5-7

non pre- 25 NS 94 NS 119 20-25 used I 3 45 3,'45 3590 3590 used i 600 600 not used I 150 150 246 250 not measured 423 um heat. NS 92 NS 93 mm 4,4 4,4 4400 4400 600 600 I 150 l5b 358 463 -I 781 7-17 NS 9 MÇ3 0.25 acetylene 5,8 3657 702 611 '458 - 526 5-9 NS 1 4 - - - - 257 f - 324 55 32/6 - 478 4,5 NS 2 I I 4. - 32/8 485 2,7-4,5 NS 3 I I I 32/10 '496 4,3-5,0 NS 4 I I I 32/12 526 '4,5-5,5

NS 5 Messer not not I 42,5/5 456 7

NS 6 Gries- used - used I 42,5/8 478 7

NS 7 heim I not 42,5/10 not 489 6-10 25 N 8 10- - 3257 373 used 42,5/12 measured 489 6 NS 10 25 - acetylene 4 8 2900 370 - 455 32.?5 526 5,5 NS 11 min I 370 324 310 32/5 '462 3,3 e e NS 12 II I 460 400 296 32/5 '427 3,7-6,5 w NS 13 I I 370 324 310 32/6 '480 4-6,5 C NS 14 J I 370 324 353 32/6 487 4-5 O o NS 15 NS 16 I ¿ eJ_{' 2900} 370 460 324 f400 413 458 32/6 32/6 561 520 5-11 5-6 e NS 17 25-40 --, 4,5 2855 460 40 455 /6 540 4,5 4-,_u

INS

28 NS 91 ESAB notf 6,35 5,9 9810 5725 notf 750 750 4 I 5Ô 600 3O 308 6,6/6,6 8,8/2,3 -

f

390 407 11-25 6 e o 25 NS 29 NS 40 15-25 mm used - acetylene 6,35 6,0 9810 6000 used 1125 1250 flOt used j 900 1000 463 465 6,6/6,6 8,8/2,3 sJred 574 442 8-10,5 6-8 o '-i E I NS 30 NS 39 type Sch6nherr -j 6,35 6,5 9810 6550 1500 1500 I 1200 1200 619 644 6,6/6,6 8,8/2,3 -574 '460 18 14-19 NS31T ESAB ESAB 4,5 -240 100/6 not 368 10-12 Ql s w I NS 32 T 20-44mm 200-500 t -s--not neasured 240 100/6 measured 23 10-15 LOOSCO LOOSCO 25 NS 50 propane 3,45 2900 1440 500 360 150 260 100/0 180 395 6-10 e NS 54 NS 55 20-50 min 200-250 inn, 3,8 4,3 3065 3410 1440 1440 600 600 360 360 150 150 360 460 125/16 150/16 not measured 25 520 5-10 6-17 23 f 2940 L - - 50/25 120 371 7,5-11,5

INS NS 24

I 75/25 135 335 - 7,5-8,5 - NS 42 100/25 155 320 6-7 a NS 43 LOOSCO I 125/25 160 345 6-10 LOOSCO 2940 J 50/50 70 480 14 NS 25 20-50 mm 200-250 propane 3 45 2900 1440 75150 80 453 7,5-9 u -w 25 NS 26 NS44 NS45 NS mm I I I I i T I I 600 J -360 -150 250 100/50 125/50 75/16 105 110 212 460 395 320 5-5,5 6,5-9 11-15 I I I J $ -46 NS 47 NS 35 NS 36 NS 37 NS 38 -I ¡ - - L _100/16 50/25 75/25 50/50 75/50 225 f not measured 250 300 320 470 468 9-14 10-13 6-11 10-18 -590 t 300 - 20 260 260 260 AGA X-302 12-7g mm ÀGA X-302 6-12 mm f acetylene -f 2,95 3640 3640 650 i 6JO f 300

type of test non pre-heat. i I LOOSCO 200-250 mth 'L t LOO SC O heating blowpipe high capacity non pre-heat. n .p .h. o.p.h.

object plate nuùiber cutti preh.

óf gauge of nozzle flame()

test mm specimen type type

-i hard-ness ientificatIon I 25

I

t

25 2t i hard- 35 ness 35 microst 20 roughness2o NS 49 NS 51 NS 52 NS 56 -NS 60 -NS 64 -NS 65 NS 66 -NS 67 -NS 88 NS 89 NS.85. NS 69 NS 71 NS 86 NS.77 ÑS 70 NS 87 NS 84 NS 95 NS 96 NS 97 NS 98 NS 99 NS 1J,8 NS 119 NS 120 NS 121 NS 175 NS 176 NS 177 NS 178 NS 179. NS 201 NS 202 NS 301 NS 302 I LOOSCO 20-50 mm LOOSCO 2Ö-50 mm

non preheat. cut without preheating

flott used $ not used 'LÒOSCO h. cap. LOOSCO h cap. kind of gas I propäne I

i

propane' propane cutti cutting oxygen réss. uply atô ' i/h 3 ,45 3,8 4,3 3,45 3,45 4,4 3,45 4,4 4,4 3,145 3,45

t

3,45 t 3,145 I 5,0 5,0 3.,45 3,45 2900 3065 3410 3590 3590 4400 3590 4400 4400 3590. 3590 t 3590

f

3590 i 5225 5225 3590 3590 ng conditions

preheatin gas supply

oxygen suppl i/h

i/h preh. cutting

preh. cuttin flame nozzle flame nozzle I 1440 ¡ 2880 irr. I, irr. 2880 2880 irr. 2880 irr. 2880

= cut with preheating by 2 preh. flames tandemwise (low capacityY cut with preheating by i. preh. flàme (high capacity)

irr. irrelevant ¡ 600 I I 00 t 600 600 600 results temperature at place of cut oc 150 50

t

360 720 irr.

I

irr. 720 720 t 150 i irr. 720 irr. 720 150 Ir f

ie

running speed ¿sn/mm 240 350 450 266 262 2149 255 256 255 252 352 451 246 248 345 359 342 354 457 460 460 247 250 250 250+10 Ir

t

250+10 Ir 250 250 249 246 a/b measure mm 100/0 125/O 15 0/O 100/0 100/O 12 5/0 150/0 100/0 100/O 125/0 5/0 12 5/0 125/0 150/0 150/0 150/0 100/0 t lOO/O irr. Ir irr. 10 /0 100/O irr. 145/0 irr. 85/0 315 245 180 not. measured not -measured n.m. 128 n.m. n.m. of the te maximum hardness NV 5 245 409 402 265 296 283 283 371 293 321 353 386 310 325 310 353 441 454 350 460 593 341 n.m. 381 n.m. n.m. n.m. 435 n.m. n.m. 466 480 516 367 345 516 381 516 286 sts roughness of face of the cut R lis 'a 4-8 5-7 6-20 15-16 7-16 6 -17 6-17 8-10 8-13 6-10 ¿4-7 5-8 6.5-16 6-8 7-14 n.m. 4-8 6-11 9-20 5-9 8,5-13

:t:

n

L.

t

n.m. 6-12 7-11 See táble 5 on page 15 for fatigue results n.m. = not measured

AJPENDIX 8c

non preheat. = cut without preheating

= cut with preheating by lpreh. flame (high capacity) central p. central 'pt-:of'tetspecimen.

irregular. irregularity due to losing a cut

} repeated testing of same specimen

identification LuLL.Lllg

rrnMtnn

_{results of the tests}

type of test, number of specimen cutting oxygen maximum 'hardnesE roughness of face of the cut

um fatigue stress number cycles of 6 xlO

no

stärting point of press supply

ato I/h HV 5 R _R R N/mm2 fract. fract. crack

NS 1011

3,45

3590

200

-

2,26

-;NS 1015 _2Li6

_-

_2,0

-NS 102 _2'4.6

_-

_2,19

-NS 103

280

0,74

-

centra.p. NS

₁₀₄

mean 260

0,98

-

'central p.

NS 105

60 250

0,80

-

transition

'NS 106

317

6-17 32-50an

2147

1,29

-

transition NS 110

_I7->

_{60-90 "120}

_24S -

2,02

NS 111

243

_1,06

_-

transition

NS 112

₂₂₃

_-

_2,0

-NS 113

243 '

0,26

-

irregular. NS 1114 2314

_-

4,1

-NS 115

₂₄₅

_-

_2,9

'NS 116

' 2'+4

0,23

-

_irregular. NS. 117

!3,5

3590

306

-

-

-- not testd NS 122

'4,3

1400 396 245

0,54

transition

NS 123

2145

0,61

-

transition 'NS

124

12-2240-80 80-' 225

_2,0

_---

-.. NS 125 : 140, 235

:1,02

-

clamps NS

₁₂₆₁

₂₃₅

1,52

_-

_{hole in cl.} 'NS

126j

4,3

4400

₂₃₅

-

_2,0

-NS 129

3,45

3590

321 249

1,03

-

irregular.

NS 130

-: 229

0,92

-

irregular.

NS'131

-

-

-NS132

-

:

-

-

-ÑS133H

--

-NS134

-

:

-

-non

NS 136

« ' 225

0,40

-

_{central p.} pre-

NS 137

₂₀₀

_0,46

_-

_irregular.

ÑS 1387

₁₆₀

_-

_2,02

-heat

NS i38.

_180.

_2,16

-NS 138J

200

-

:2,27

.

-NS 139

3,45

3590

₂₀₀

_-

_2,0

-NS 1401

I . 180

-

2,2

-NS l40'

- 200

-

2,0

-...NS 140J

220 ,

1,28

-

. central p.

General data fàr all specimens object of tests: fatigue strength

plate thickness: 25 mm

cutting nozzle type: Loosco

20 - 50

mm

preheating flames type Loosco heating blowpipe, high capacity

kind of gas: propane

preheàting oxygen supply:

2880

i/h prehéà.ting flame (if relèvánt)

600

i/h cutting nozzle

gas supply : 720 i/h prehéating flame (if relevant)

150 1/h cutting nozzle

running speed

_{350 +}

_{10 mm/min}

_{(NS 122 - NS 126 mcl)}

250 110 mm/min (other specimens)

-a- measure

125 nú. (NS 122 -

NS

126 md.)

object of tests: fatigue strength

plate thickness: 35 mm (NS 203 - NS 210 mcl.) 25 mm (other specimens) cutting nozzle type: Looseo 20 - 50 mm

preheating flame type: Looseo heating blowpipe, high capacity kind of gas: propane

preheating oxygen supply: 2880 1/h preheating flame (if relevant.) 600 1/h cutting nozzle

gas supply: _{720 1/h preheating flame (if relevant.)} 150 1/h cutting nozzle

running speed; 250 + 10 mm/min

-a- measure : 145 mm (NS 203 - NS 210 mcl)

100 mm (other specimens if relevant)

- 'U L WL LIIIJU L pL11eUJLi

cut with preheating by i prehèating flame (high ôapacity)

central p central part of testspecimen

irregular irregularity due to losing a cut

} repeated testing of saine specimen

APPENDIX

identification. _{results of the tests}

type number cutting maximum roughness of fatigue number of starting

of of oxygen hardness face of the cut stress cycles xlO6 point

test specimen press supply _{um no of}

ato 1/h HV 5 _{Ra Rt} R N/mm2 fract. fract. crack

NS 141 A _{244 0,17 - irregular.} NS 142 204 ,0,'48 - irregular. NS 143 164 0,51 - irregular. -e NS 144\ 124 - 2:,0 -NS i'-i.4J . 144 1,36 i -NS 145 ₁₅₄ - H_2,01 NS 146 not measured 144 - 0,7 NS 147 . 134 - 2,15 NS 148 134 - . 2,0 NS 148 1 154 1,79 -NS 150 . 220 - 2,95 clamps NS 151 _{24.0 - 2,55 clamps} non pre-NS 152 NS 153 . 250 260 1,07 -2,60 clamps heat NS 154 . 280 0,94 - central p. NS 155 _{270 - 2,90} NS 156 - - -

..-NSÏ57

. - - -n. NS 163 . . 243 - 2,1 p. NS 16'3 228 - 2,2 h. NS 165 240 NS 166 228 - 2,1 o- NS 167 227 - 2,7 ÑS 169 3,45 3590 223 - 2,1 NS 203 5,0 5225 270 0,32 transition NS 204.1 . 240 3,2 clamps NS 2041 24.0 - 2,0 -NS 206 270 0,32 - transition NS 207 _{not tested} --e

NS 208i 7-17 30-60mean 24.0 2,4. - . clamps

60 ..

NS 208. - . 24.0.

. 2,0 .

Smoothly cut

Extra rougly cut

¿

1a = circ. 7

Ra. circ. 11 Rt. circ. 45 Rp. circ. 60

& -a

V-Rt = circ. 27 Rp = circ. 30

Roughly cut