US 2871557 A
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PROCESS oF MAKING DROP-FORGINGS No Drawing. Application July 12, 1954 Serial No. 442,934
Claims priority, application Austria July 24, 1953 2 Claims. (Ci. 29-528) In order to achieve forming-properties, which make specimens most fit for deformation in dies, specimens have to be prepared for drop-forging and to be worked at least twice in either direction. Thus forming both in strain-direction and cross-direction has to be repeated several times in order to impart a favourable texture to the specimen. From these reasons steel specimens before being drop-forged usually are submitted to a rolling or forging-process. After casting the material, it is rough-forged, then heated again in order to prepare it for further working in the die. Both, this repeated heating of the specimen and the forging-process itself do not only require plenty of time, but also involve a great consumption of caloric energy. In order to avoid those drawbacks and to save energy, attempts were made to change the texture of the cast steel by admixtures and thus make preliminary forging or rolling dispensible for final working in the die. Those attempts however, have not been successful hitherto.
In order to achieve the necessary changes of the texture of cast specimens attempts have been made as well to influence the texture of the steel by mechanical, electrodynamical or magnetic oscillations during solidification. The effect of those oscillations however could not adequately replace preliminary working.
Steels, which show fine texture are especially fit for being worked in dies. This fine texture, which makes specimens fit for being Worked in dies without preliminary forging or rolling, can be achieved by continuous control of the process of solidification when dealing with steels produced by continuous-casting-process, as in this process the molten metal in passing several zones of cooling, which can be controlled individually.
Additional improvements of the fine texture can be achieved by exposing cast billets to the elfect of me- 50 chanical, electric or magnetic oscillations, such as rotating field or ultrasonic vibrations, during solidification.
Drop-forging experiments, carried out with specimens, which were made by continuous-casting-process, not only have verified above considerations, which induced direct 55 use of cast billet-sections in dies, but also have shown, that those continuously cast sections were far more fit for being drop-forged without any preliminary procedure than cast ingots after the usual preliminary forging or rolling treatment. The reason, why continuous-cast specimens .60 are preferable is, that their cross-resistance, designed as cross-resilience, is superior in continuous-cast specimens, as no preliminary treatment is necessary prior to working Stts Patent 0 2,871,557 Patented Feb. 3, 1959 in dies and it is this very property, that has most favourable elfect on working in dies.
Even after a perfect continuous casting plant has been successfully developed and billets free of defects had been produced, the generally prevailing opinion, that cast iron or its alloys respectively are not fit for dropforging unless they are pre-treated by forging or rolling, could not be abandoned. Especially experts do not even dare to think of drop-foring cast metal as it comes out of the mouldnot even billets produced by continuous casting process.
The achieved effect can be increased if specimens are submitted to a longer annealing treatment before they are submitted to drop-forging, whereas annealing is extended until difiusion takes place. This effects equalizing of segregations, that might have been formed during continuous-casting. For specimens, which are tempered immediately after drop-forging, from the forging-temperature, this procedure is especially economizing, as those specimens can be finished by one single heattreatment. And even this heat-treatment gets dispensible, if the heat of fusion, that has remained in the specimen after casting gets evaluated for the drop-forgingprocess, i. e. if drop-forging is carried out before the cast billet has cooled.
1. A process of making drop forgings, which comprises forming a steel ingot by continuous casting in the absence of mechanical pressure while passing said ingot through several zones of cooling which are individually controlled to effect a slow cooling of the ingot during solidification in order to obtain a fine-grained solid structure suitable for drop-forging, and drop-forging the ingot thus obtained between dies causing the material of the ingot to flow in all directions under pressure, without any intermediate working of the steel.
2. A process of making drop'forgings, which comprises forming a steel ingot by continuous casting in the absence of mechanical pressure While passing said ingot through several zones of cooling whichare individually controlled to elfect a slow cooling of the ingot during solidification in order to obtain a fine-grained solid structure suitable for drop forging, drop-forging said ingot between dies causing the material of the ingot to flow in all directions under pressure, Without any intermediate working of the steel, and subjecting the drop-forged steel to a diffusion annealing treatment to effect equalization of any segregations formed during the casting operation.
References Cited in the file of this patent UNITED STATES PATENTS 356,974 Bagaley Feb. 1, 1887 395,684 Baker Jan. 8, 1889 406,946 Norton July 16, 1889 441,375 Norton Nov. 25, 1890 2,235,243 Adelson Mar. 18, 1941 2,301,027 Ennor Nov. 3, 1942 2,334,929 Hone Nov. 23, 1943 2,462,851 Fawcett Mar. 11, 1949 2,705,353 Zeigler 2 Apr. 5, 1955