Metal treatment – Compositions – Heat treating
Patent
1975-09-29
1977-05-17
Stallard, W.
Metal treatment
Compositions
Heat treating
75 5BA, 75 5C, 148 36, B22D 2308
Patent
active
040239853
ABSTRACT:
Disclosed is a method of producing a versatile as-cast steel shot having a substantially fully martensitic structure and corresponding full hardness which permits eliminating intermediate steps of heat treating to harden and subsequent drying in producing steel shot having a tempered martensitic structure or in producing steel grit.
The method includes steps of charging, melting, refining, and pouring. The pouring step is accomplished by directing a stream of the refined molten steel through a stream of water under pressure and into a fluid quenching bath. The refined steel comprises: carbon in about the range of from 0.6 to 1.20 per cent by weight; manganese in about the range of from 0.50 to 2.26 per cent by weight; silicon in about the range of from 0.3 to 1.80 per cent by weight; sulphur in about the range of from 0.0 to 0.1 per cent by weight; phosphorous in about the range of from 0.0 to 0.1 per cent by weight; boron in about the range of from 0.0 to 0.01 per cent by weight; with the remainder of the metal being substantially all iron and trace elements and impurities commonly found therein. The boron, when present, is the result of an alloy-adding step which includes the addition of ferro-boron to the melted metal.
The method yields an as-cast shot hardness in the full hard Rockwell C (Rc) range of 65+ to 67+ in a significantly increased per cent of heats over what is normal in as-cast steel shot having comparable carbon per cent by weight and having generally the same chemistry. The control of carbon in the preferred range and/or the use of boron as an alloying element to produce substantially fully martensitic or full hard as-cast shot permits elimination of both the hardening furnace and drying operation following hardening. The as-cast product goes directly into a tempering operation to make tempered martensitic shot or to a crushing operation to make grit.
REFERENCES:
patent: 224858 (1880-02-01), Winterlich et al.
patent: 2863790 (1958-12-01), Chen
patent: 2867554 (1959-01-01), Wilson et al.
patent: 2974031 (1961-03-01), Wilson et al.
patent: 3649370 (1972-03-01), Dorn et al.
Dunkerley Fred J.
Gaudino Albert J.
Vilyus Robert P.
Cleveland Metal Abrasive, Inc.
Mulholland John H.
Stallard W.
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