CA1073321A - Alloy steel - Google Patents

Abstract

ALLOY STEEL
Abstract of the Disclosure There is provided a high strength alloy steel comprising a vanadium alloyed steel normalized at a temperature above 927°C.

Description

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~ ALLOY STEEL

; This invention relates to high strength alloy steels and more particularly to a high strength alloy steel suitable for casting into railroad car wheels and the ,~ !
like.
There has been a long felt need ~or steel alloy -~
having a greater strength and suitable properties for cast- :
i~g into railroad car wheels and the li~e. Heretofore, experiments with vanadium alloy steels have not been entirely satis~actory, in that the results have not been uniformly consistent. Likewise, normalizing o standard carbon alloy steels without the vanadium at temperatures above 927C has not produced significantly better results.
The primary object of the present invention is to provide an improved method of forming a high strength vanadium alloyed steel normalized in an optim~n range. :
In accordance with the present invention, it has .
been ~ound that a superior high strength alloy steel is formed when a vanadium alloyed steel is normalized at a temperature above 927C.
It has been discovered according to the present invention that a steel alloy treated in the molten state with vanadium and normalized at a temperature above , , . . ..

- ^ RMF:sa 10-4-76 Case 5495 10733Z~

927C provides an alloy suitable for the manufacture of castings and other wrought articles having excellen~
yield strength and other characteristics w~lich make it desirable for the casting of railroad car wheels and the like.
The alloy steel of this invention may comprise broadly the following composition:
Component Precent by Weight Carbon abou~ 0.50 to 0.80%
Manganese about 0.60 to 0.85%
Phosphorous nil to about 0.050%
Sul~ur nil to about 0~050%
Silicon about 0.15 to 0.50%
Vanadium 0.06 to about 0.25%
Iron Balance wlth residual im~
purities in ordinary amounts The presence o~ vanadium coupled with normalizing is critical and must be maintained substantially within the range set out above. The alloy must have had su~-ficient vanadium added to the molten metal to provide a residue of at least 0.06% vanadium in the alloy thereby producing the desirable characteristics of high resis-tance to fatigue and thermal cracking. While this mini-mum must be maintained, we prefer to use a somewhat higher minimum~ and preferably not less than about 0.14%
of vanadium in the alloy. Greater amounts than 0.25%

M~:sa 10-4-76 Case 5495 ~3733Zl of vanadium in the alloy do not produce any improvement in results and excessive amounts will have a deleterious effect.
It has been found that in manufacturing the steel alloy of this inventîon, the alloy elements are placed in the ladle or added to the molten metal at the begin-ning of the tap. Silico-manganese, ferro-manganese and ferro-silicon are preferably placed in the ladle beore the heat is tapped. When the ladle is partly full, the vanadium is added, and then aluminum is added as a de-o~idizer. The vanadium and aluminum are preferably drop-ped into the stream of molten steel. flowing into the ladle.
Specific examples are disclosed as follows:

Example Number 1 An electric furnace heat was poured and ~ast lnto railroad car wheels having the following analysis:
Component Percent-by Wei~h~

Carbon 0.63 Manganese 0.74 Phosphorous 0.021 Sulfur 0.027 ~ Silicon o.~o ; Vanadium 0.18 Iron Balance with residual im-purities in ordinary amounts - 3 ~

RMF:sa 10-4~76 Case 5495 ~L~733Z~L

Two samples of cast wheels were normaLi.zed at dif-ferent temperatures with the fol.lowing results:

Normalizing Yield Strength Temperature, C ~cg/sq. cm_ Sample A 843 3584 Sample B 982 4507 Example Number 2 An electric furnace heat having the alloy composi~
tion of Example Number 1 but with the carbon content in- ;
creased to 0.73~/0 by weight was poured and cast into railroad car wheels, and three samples were normalized at different temperatures, with the following results:

Normalizing Yield Strength Temperature, C kz/sq. cm Sample C 843 3826 Sample D 982 4763 Sample E 1121 5347 From the above examples~ it can be seen that the normalizing of a vanadium steel in the temperature range of 927C to 1149C produces a superior alloy steel.
Specifically a vanadium steel normalized at 982C to 1121C has been ~ound to produce optimum results.
It should be understood that the arrangement des- -cribed above constitutes the preferred embodiment and that many adaptations and modifications may be made without departing from the spirit o~ the invention.

I

Claims (2)

RMF:sa 10-4-76 Case 5495 The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of forming a high strength, high carbon, alloy steel comprising the steps of alloying a vanadium steel consisting of about 0.50 to 0.80% carbon, about 0.60 to 0.85% manganese, nil to about 0.050% phosphorous, nil to about 0.050% sulfur, about 0.15 to 0.50% silicon, about 0.06 to about 0.25% vanadium, and the balance iron with residual impurities in ordinary amounts; and nor-malizing said steel at above 927°C.

2. A method of forming a high strength alloy steel as set forth in Claim 1 wherein said normalizing is in the range of 982°C to 1149°C.