US2021781A - Alloy steel and articles made therefrom - Google Patents

Description

Patented Nov. 19 1935 I ALLOY STEEL AND ARTICLES MADE THEREFROM Walter G. Hildorf, Canton, Ohio, and Albert E. White and Claude L. Clark, Ann Arbor, Micin, assignors to The Timkcn Roller Bearing Company, Canton, Ohio, a corporation of Ohio, as

trustee No Drawing.

' 5 Claims.

Our invention relates to alloy steels and to articles made therefromwhich are adapted for use at high temperatures, particularly temperatures above 750 F.

The invention has for its principal object an alloy steel and articles made therefrom which will be capable of resisting oxidation at elevated temperatures, that-is, above 750 R, which are extremely resistant to shock at such temperatures, which have a high degree of strength, which are easily workable and thus capable of being fabricated into intricate shapes and which will be considerably lower in cost than the austenitic steels or the high chromium steels ordinarily used at such high temperatures.

The invention consists principally in an alloy steel containing chromium, tungsten and silicon as its principal alloying ingredients with or without vanadium and having substantially the following composition:

' Percent Carbon 0.01 to 0.20 Manganese 0.20 to 1.0 Silicon 0.50 to 1.0 Chromium 0.75 to 1.50 Tungsten 0.50 to 1.50. Vanadium 0.01 to 0.50

with the usual percentages of sulphur and phosphorous.

The invention further consists in the alloy steel and articles made therefrom hereinafter described and claimed.

Our alloy steel is suitable for such uses as high temperature steam lines for power plants, superheater tubes, oil still tubes in which sweet crude oil is used and in which corrosion is not a serious factor, for heat exchangers andcondensers.

It is recognized that chromium-tungstensilicon steels have heretofore been known but they have been used as tool steels, particularly in the manufacture of tools, such as drills, taps, reamers and chlsels, and they have not been regarded as satisfactory for the high temperature uses hereinbefore set forth. I

The general range of several ingredie ts of our alloy steel is as follows: 1

' Per cent Carbon 0.01 to 0.20 Manganese 0.20 to 1.0 Silicon 0.50 to 1.0 Chromium 0.75 to 1.50 Tungsten 0.50 to 1.50 Vanadium 0.01 to 0.50

Application November 20, 1931, Serial No. 576,428

A preferred narrower range of ingredients is as follows:

- Per cent Carbon 0.01 to 0.10 Manganese 0.20 to 0.60 5 Silicon 0.60 to 1.0 Chromium 0.75 to 1.25 Tungsten 0.75 to 1.20

The tungsten content of our steel preferably 10 approximates fairly closely the chromium content thereof, but should not appreciably exceed the chromium content; whereas in prior chromium-tungsten-silicon steels, the tungsten con- 15 tent has been about twice the chromium content. The tungsten content of our steel will ordinarily be somewhat less than the chromium content, so as to avoid the possibility of its appreciably exceeding the chromium content.

The preferred narrow range is based upon the results of tests of numerous alloy steels within the broad range of ingredients hereinbefore set forth, including tests of the short time proportional limit at 1000 F. (which is commonly ac- 25 cepted as the best measure of the metals high temperature creep resistance) load carrying abil ity, ductility and impact resistance.

Our alloy steel has an actual creep resistance. and load carrying ability at 1000 F. far in excess 30 of what was to be expected of chromium-tungsten-silicon alloys; and it has a good combination of strength and ductility at 1000 F.

Said alloy has an excellent combination of strength, ductility and resistance of impact re- 35 sistance at 75 F. and hence is very well adapted for low temperature use as well as high temperature use. The steel has a good resistance to oxidation at temperatures from 1000 to 1200 F.

Following are the results of tests of a typical steel embodying our invention and having the following composition: .025% C, 23% Mn, .46%,Si, 1.13% W, 1.20% Cr.

Physical properties at 75' r.

Tensile strength lbs. per sq. in.

Proportional limit lbs. per sq. m.

Brlnell hardnosa Percent Percent do. Rod.

as, zoo-15.500 same-46.000 7a 7-11.15 138 153 Percent loss of weight by oxidation in. 150 hours V 1000* r. 1100" F. 1200* r.

The qualities and characteristic features of our alloy steel and articles made therefrom as herein brought out constitute important advantages and satisfy a long existing demand for a low priced steel having such qualities. L

The addition of vanadium in amounts from 0.01 to 0.50% is helpful in improving the properties of the steel. athigh temperatures.

What I claim is:

1; An article, such as a boiler tube or the like, for use at high temperatures the article being formed from a steel alloy characterized by maintained high creep strength under continuous exposure to operating stress at temperatures in excess of 750 F., by substantial resistance to oxidation at operating temperatures, and by containing from about 0.01 to 0.2 per cent of carbon, about 0.75 to 1.5 per cent of chromium, about 0.2 to 1.0

3 per cent of manganese, about 0.5 to 1.0 per cent posure to operating stress at temperatures in excess of 750 F., by substantial resistance to oxidation at operating temperatures, and by containing irom about 0.01 to 0.1 per cent of carbon, about 0.75 to 1.25 per cent of chromium, about 0.2 to 0.6

per cent of manganese, about 0.6 to 1.0 per cent of silicon, about 0.75 to 1.2 per cent of tungsten,

impact ,stantially iron.

the tungsten content being less than the content of chromium, and the remainder of the steel being substantially iron. I

3. An article, such as a boiler tube or the like, for use at high temperatures the article being formed from a steel alloy characterized by maintained high creep strength under continuous exposure to operating stress at temperatures in excess of 750 F., by substantial resistance to oxidation at operating temperatures, and by containing about 0.025 per cent of carbon, about 1.2 per cent of chromium, about 0.23 per cent of manganese, about 0.5 per cent of silicon, about 1.13 per cent of tungsten, and the remainder of the steel being substantially iron.

4. An article, such as a' boiler tube or the like, for use at high temperatures the article being formed from a steel alloy characterized by maintained high creep strength under continuous exposure to operating stress at temperatures in excess of 750 by substantial resistance to oxidation at operating temperatures, and by containing from about 0.01 to 0.2 per cent of carbon, about 0.75 to 1.5 per cent of chromium, about 0.2 to 1.0 per cent of manganese, about 0.5 to 1.0 per cent 01 silicon, about 0.5 to 1.5 per cent of tungsten, about 0.01 to 0.5 per cent of vanadium, the tungsten content being less than the content of chromium, and the remainder of thesteel being substantially iron.

5. An article, such as a boiler tube or the like, for-use at high temperatures the article being formed from a steel .alloy characterized-by maintained high creep strength under continuous exposure to operating stress at temperatures in excess of 750 F., by substantial resistance to oxidation at operating temperatures, and by containing irom about 0.01 to 0.1 per cent of carbon, about 0.75 to 1.25 per cent of. chromium, about 0.2 to 0.6 per cent of manganese, about 0.6 to 1.0 per cent of silicon, about 0.75 to 1.2 per cent of tungsten, about 0.01 to 0.5 per cent of vanadium, the tungsten content being less than the content of chromium, and the remainder of the steel being sub- WALTER G. HILDORF. I ALBERT E. WHITE. CLAUDE L. CLARK.