alternating current and direct current.
There also have been developed elec
trodes for many newer higher tensile steels and those with air hardenable prop
erties which will make welds without the use of preheating and without any under- bead cracking. It is expected that these electrodes will increase in popularity after the war because of the larger uses for these quenched and drawn steels.
“There has been continued improve
ment in the quality of thermit welds both in the ‘as-welded’ and the ‘post-heated’
condition and developed for emergencies the use of thermit in making castings.
Their use in welding stern frames and similar heavy parts for the Maritime Commission has grown enormously.”
» techniques; welding machines and elec
trode materials are being developed for the development of silver-cadmium-oxide compositions has been an outstanding contribution.
“In the field of high strength, high conductivity copper alloys, advances have been made to produce alloys with high fatigue and low drift characteristics and the use of precipitation hardened copper base materials is increasing rap
idly.
“The difficulties in machining high strength, high conductivity copper-chro- mium base alloys have been overcome by the development of a new
copper-chromium-tellurium alloy which retains an electrical conductivity of 80 per cent IACS or better, combined with a tensile strength of approximately 75,000 pounds per square inch,
“In the field of powder metallurgy, a new bearing alloy was developed, con
sisting of an age-hardening copper base material. Ingredients are silicides and phosphides, and tensile strength values of 50,000 pounds per square inch, to
gether with fatigue strength values ex
ceeding 15,000 pounds per square inch, are obtainable. The alloys are lead-free but give antifriction characteristics sim
ilar to copper-lead alloys containing 20 to 30 per cent lead. Researches in the field of silver base bearing materials have resulted in the development of a silver- thallium alloy of superior antifriction characteristics.”
Hydrofluosilicic Acid Clears 24ST Surface for Spotw elding
F. M. Morris, process surface preparation of alclad 24ST alumi
num alloy for spotwelding which con hydrofluosilicic acid quite successfully.
Briefly, the procedure for the surface preparation of alclad 24ST parts consists of the following: hydrofluosilicic acid follows. Thorough rinsing in cold running tap water for
about 4 minutes and drying prior to spotwelding is the final step in the pro
cedure.
“We have been using hydrofluosilicic acid for the surface preparation of al its important increase in thermal effi
ciency, was made possible by the devel
opment of suitable welding procedure for pressure vessels and pipe. It would bolted or screwed connections resulting in constant maintaining. approximately three times the calculated average stress in the ligaments between the holes. At these pressures and tem
peratures such conditions invite trouble while the uniformly distributed stress at a properly made weld allows relatively trouble-free service.”
Centralized Control System N eed ed for Production W elding
erating their welding departments on any of the standard methods of com
pensation, plant management has been without the complete control that is nec
essary. The systems do not go far enough in the case of welding because of the complexity of the problems involved.
“Any practical system must provide a complete control of all phases of welded fabrication which, in general, means control of (1) costs, (2) procedure, (3) production, and (4) quality. Final at-
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290 / ■ T E E L
HEAT TREATING
Induction H eating Big Industry Requiring 300,000 Kilowatts installations are smaller than during the period when war production equipment was more urgently needed.
“There has been a gradual shifting comparatively recently, with installa
tions made largely for war production,
stallations throughout the world sub
stantially double each four years since complete with cover, legs and lifting ings, can now be readily obtained. H eating Holds "Great Promise"
C. L. Ipsen, manager, heating for forging, hardening, brazing, and soldering. Heat is generated in only that portion of the work that requires processing. There is practically no waste heat. The time of heating is of ex
ceedingly short duration.
“Capacity of induction-forging fur
naces now in use heating shells for forging and nosing and for nosing bombs totals more than 50,000 kilowatts. Im
proved working conditions, speed of heating, reduced floor space required for the furnaces, and absence of scale are advantages that have brought the overall cost of induction forging well within that of former forging methods.
“Selective hardening of such parts as gear teeth, crankshaft bearings, and pis
ton pins, as well as localized heating such installation, the process eliminates time-consuming and expensive handling inherent in former hardening methods.
“In many cases these processes can be mechanized for full automatic op
eration with controls that insure a
uni-lormly high-quality product. This is another factor which makes the induc tank-track bodies, bombs, and machine parts. By demonstrating its effective
ness and low cost in bonding these highly-stressed parts, tire electric-fumace brazing process has paved the way for much more extensive use in the manu
facture of peacetime products.”
Buying S teel "On Performance"
Stops Low-Hardenability H eats steel guaranteed to fall within published hardenability bands, means are at hand to prevent low hardenability heats where they are unwanted.
“Additional information alio has been, published on isothermal annealing as a result of further studies by various investigators. Many advantages have accrued thereby, especially in saving furnace time, with a simultaneous im
provement in machinability. The iso
thermal diagrams have also been helpful to the steel treater by giving a clearer insight into the hardening characteris
tics of the steel and particularly in re manner. This ever increasing interest was clearly revealed by the attention given the induction hardening displays at the recent Metal Congress.”
W artime Progress in Furnace Building Tops All Olher Periods Harry Dobrin, vice president. Furnace Engineers Inc., 1551 West Liberty av
enue, Pittsburgh: “The fumace manu
facturing industry has had a very impor
H E A T T R E A T I N G
steel manufacturer or processor is willing to pay more for scientifically designed burners, instrumentation and accessories alone than previously was considered suf
ficient for the cost of an entire furnace world leadership in mechanical and com
bustion skill as applied to the metallurgi heating and heat treating. Additional manufacturers of equipment have entered the field and new designs have been prominently mentioned recently as well as new uses.
“Among the most interesting has been increased use of induction equipment for brazing purposes, generally using silver solders as brazing medium. Braz
ing of carbide tips on tools has been an excellent example. Producers of brazed assemblies, especially of hydrau
lic equipment type, have found induc particular job rather than established de
signs sold by dealers.
“Increased attention is being paid to hardening to various depths. The high frequency machines that give very shal
low depths have found some specialized
“Induction hardening, after prelimi
nary furnace hardening and tempering, has solved many tricky jobs. Alloy steel gears, for example, are sometimes hard
ened all over to 34-38 rockwell C, finish machined, then teeth are induction hard
ened to a higher hardness. Less distor
tion often makes this preferable to car- burizing.
“Localized induction tempering, al
though tricky and far from being fool possible when special control methods are employed.
ing—such as upsetting bolt heads.”
Isothermal Diagram s S a v e Lost achievement has been the clarification and the publication of isothermal trans
formation diagrams, thereby enabling the heat treater to choose a heat treatment which can reduce to a minimum the movement of intricate parts during the process of hardening and tempering.
“Hardenability has also come in for considerable study and, with the publica
tion of various bands, should enable the least one significant result, namely: Con
tinuous heat treatment (annealing or hardening) of bar stock and tubing. Suf
ficiently high treating rates have been applied to make the continuous single line heat-treating process practical and economical with apparent beneficial effects upon uniformity and surface con
dition of the stock. It seems safe to expect and predict expanding applica
tion of this heat-treating method in the future in the ferrous as well as non- ferrous industry.
“Controlled radiant gas heating fur
thermore has proven practical and eco possibilities in continuous strip heating.
“Radiant gas heating also has been the eutectoid composition the greatest hardness can be developed in the steel, it is only of comparatively recent date that the great influence of carbon con
centrations above eutectoid compositions has been realized. As a single illus diffuse inwardly during the carburizing cycle, which is readily accomplished, when gas is used as a carburizing me