US2015991A - Alloy steel for internal combustion engine valves and associated parts - Google Patents

Description

ALLOY STEEL FOR INTERNAL COMBUSTION ENGINE VALVES AND ASSOCIATED PARTS Oct. 1, 1935. w. R. BREELER Filed Jan. 4, 1955 d R m ,m, a W m/ M P W 6 mm W 0 M w 6 V w 7/0 YL v 2 y Wm w 0 Y Z 0 0 E ,0 5 \%\\\\.u %w\\ S WWQ A u/ v, m F L m 6 W2 w 42m L z y a a w w\\\\\m\\ a 0 E a 7 \%\\\\M RQQ ham 1 ,0,

Patented a. 1, 1935 UNITED STATES ALLOY FOR INTERNAL COMBUSTION ENGINE VALVES AND ASSOCIATED PARTS Walter R. Breeler, Troy, N. Y., assignor to Ludlum Steel 00., Watervliet, N. Y., a corporation of New Jersey Application January 4, 1935, Serial No. 411

Claims.

My invention relates to alloy steels and particularly to valves, valve seat inserts and other parts of internal combustion engines coming in contact with the exhaust gases.

,5 Since the advent, a few years ago, of gasolines containing additions oflead compounds'for the purpose of reducing the detonation of the fuel, valve and valve steel manufacturers have sought an alloy having, in addition to the characteristics theretofore demanded in steel for this purpose, high resistance to the corrosive and erosive attack of exhaust gases resulting from the combustion of these anti-knock compounds in the gasoline, and particularly compounds containing lead, bromine and chlorine or otherhalogenmetal combinations. I I

Progress along this line has been greatly handicapped by the lack of any suitable laboratory test whereby alloy steels might'be subjected to conditions simulating the actual conditionsunder which valves, valve seat inserts and the like operate in an internal combustion engine using gasoline containing such anti-knock compounds as a fuel, and it is only within the past year that such a test has been developed.

It is well known that steel for use in-the exhaust valves of internal combustion engines should have good resistance to scaling at temperatures in excess of 1600 F. It-should preferably have a critical point in excess of 1400 F., it should not warp after repeated heating and cooling, and it should also have good resistance to corrosion when cold.

Except for their susceptibility to attack by the exhaust products of anti-knock gasoline, the chromium-silicon steels disclosed by Armstrong in his United States Letters Patent No. 1,322,511

make very excellent valve steels, and for many years the majority of the exhaust valves used in internal combustion engines both here and abroad have been made of this composition.

With the development of the high compresalon type of engine which requires for its satisfactory operation a non-detonating fuel, came the demand for exhaust valves capable of long sustained operation under the attack of corrosive exhaust gases containing compounds of lead, oxygen and bromine, and it is quite generally accepted that the best valve steels now known are the high alloy austenitic types containing chromium, nickel and silicon in which the nickel content is 6% or more. Such steels while showing substantial resistance to chemical attack are expensive, difficult to machine, have a low Brinell hardness which introducesvalve stem diiliculties, have a large coeflicient of expansion when heated to valve operating temperatures and have relatively poor heat conductivity.

By utilizing a laboratory test which comprises heating the samples of the steel to be tested in 5 a specially prepared inert crucible containing v lead oxy bromide at a temperature of 1560 F. for a period of six hours or more, I have discovered the rather unexpected fact that steels containing fairly high chromium and substantial l0 amounts of siliconbut with relative small quantitles of nickel show a very much greater resistance to attack than do the straightchromesilicon steels or the chrome-nickel-silioon steels with nickel in the higher ranges.

A very large number'of samples containing chromium and silicon'in various amounts, both without nickel and with nickel in quantities varying by small percentages up to 23% have been tested in this wayand theresults clearly 20 indicate that the optimum quantity of nickel insofar as providing resistance to attack by lead oxy bromide is concerned is in the neighborhood of 2% by weight of the chrome-silicon alloy. It is also indicated that of the chromenickel-silicon alloys containing chromium from 10% to 25%, silicon from 1% to 6% and nickel from 0% up to 23%, those containing nickel under about 4.0% are by far the most resistant of the entire series. Moreover, these alloys, in the soft annealed condition have, a substantially sub-martensitic microstructure which renders them easily machinable as distinguished from alloys having a normally substantially martensitic or austenitic structure. As a matter of fact, the microstructure of my alloy in the soft annealed condition is usually carbides in a ferrite matrix.

In the accompanying drawing. Fig. 1 shows the effect of various percentages of nickel, up to about 8%, on.the loss in milligrams per square centimeter per-hour of the chrome-hickel-silicon alloys described herein when subjected to the above tests at 1340 F.; and Fig. 2 shows the same effect when tested at 1560. F. In each figure the upper curve shows the loss with the specimens 60% submerged in the lead oxy bromide, and the lower curve the loss when totally submerged. Between about 7% and 23% of nickel it may be said that the losses decrease slightly up to about 12% of nickel and thereafter increase.

Increased quantities of chromium in a. chromium-silicon alloy do not appreciably affect the large losses which alloys of this type sustain when Sample 100% submerged Mann n 1660 F. 1340" F. 1560" F.

mmuuman Loss in wgt. mgQ/sq. cm/hr.

Sample 60% submerged mmmmmum mlwv l ml While analysis number 5 in the above table, and the charts shown in the drawing, indicate that alloys containing chromium and silicon subjected to the above test, but with additions of the small quantities of nickel contemplated herein increasing the chromium content while keeping the nickel content substantially the same 5 renders the alloy appreciably more resistant to the corrosive action or the lead oxy bromide test. The essential elements of my composition are Additions up to a total of 10% of tungsten, molybdenum, tantalum, copper or vanadium, or

as much as 4% total of aluminum, titanium or 35 zirconium may be to develop particulajl' within the ranges set forth above and also concharacteristics desirable under certain conditaming nickel somewhat in excess of 4.0% 0561. tionsexample additmns of tungsten or excellent resistance to the attack of lead oxy bromide, I prefer, for the particular uses for With nickel more 40 will be too low or ab-' This results in an unstable comwhich my alloy is intended, to keep the nickel content under about 4.0%.

than this the critical point sent altogether and the alloy will be in or veryclose to the transition zone between martensite and austenite.

conditions and austenitic under others.

In order to indicate the non-warping characteristics of some of my alloys, and particularly to show that the warping is non-cumulative, a

Sample 100% submerged Loss in wgt. mg./sq. cm/hr.

Sample 60% submerged Mmummmmm .This will be apparent from a con- Analysis 006844 00 &&0 0 3 3 2 Z It is quite essential that silicon be present in molybdenum, evenin small amounts, say up to 2%, will enhance the resistance of the alloy to hot lead oxy bromide and increase the tensile l 40 strength at high temperature.

the alloy in quantities somewhat in excess of 1% in all cases in order to provide ample resistance to scaling at high temperature and to supple- 45 t t nickel in providing resistance t lead position which will be martensitic under some 4 oxy bromide. sideration of the following analyses and the relative losses therein when subjected to the lead 50 oxy bromide test.

uare containing 0. o;

and Ni. 1.75% was 7 .From the above table itwill be noted that with 7 silicon under 1%, as in analyses 3 and 4, the

addition of as much as 1.4% of nickel has practically no effect in increasing the resistance of the alloy to lead oxy bromide. In'Iact sample I 4 with 14% c shows greater loss n was cooled muchmore rapidly than the other. sample 3 having no nickel, thus indicating that The deflection at the center after each such 75 quenching was then measured. The results are tabulated below- Deflection First heat 0.0015" Second heat 0.0018" Third heat 0.0000" Fourth heat 0.0012" Fifth heat 0.0015" C 0.50- 1.0 Cr 15.0025.0 S1 A 2.00- 3.0 N 1.00- 3.0

Insofar as merely endowing the composition with resistance to attack by lead oxy bromide is concerned, cobalt might be substituted in whole or in part for the nickel, but in addition to being more expensive, its effect on the tpughness and hardenability of the alloy is much less pronounced.

From the foregoing it will be apparent that making a small allowance for impurities the quantity of iron in my alloy may be as low as about 52% or as high as 87% by weight of the total.

The word valve as used in the claims is to be understood as including in its meaning seat inserts for valves and other parts associated with valves and inserts which are subjected in use to contact with the exhaust gases of an internal combustion engine.

What I claim is:

1. An alloy steel for use in valves of internal combustion engines having in its soft annealed condition a substantially sub-martensitic micro structure and characterized by its high resistance to corrosive loss when subjected to attack by lead oxy bromide at valve operating temperatures; said steel containing carbon from 0.20% to 2.0%, chromium from 10% to 25%, silicon from more than 1% to 6%, nickel from 0.65% to under 4%, and iron from 52% to about 87%.

2. A valve for an internal combustion engine comprising the alloy set forth in claim 1.

3. An alloy steel for use in valves of internal combustion engines having in its soft annealed condition a substantially sub-martensitic micro structure and characterized by its resistance to corrosive loss when subjected to prolonged attack by lead oxy bromide at valve operating temperatures; said steel containing carbon from about 0.50% to about 1.0%, chromium from about 15% to about 25%, silicon from about 2% to about 3%, nickel from about 1% to about 3%, and iron from about to about 4. An exhaust valve for an internal combus- 10 tion engine comprising the alloy set forth in claim 3.

5. An alloy steel for use in valves of internal combustion engines having in its soft annealed condition a substantially sub-martensitic micro 15 structure and characterized by its high resistance to corrosive loss when subjected to attack by lead oxy bromide at valve operating temperatures; said steel containing carbon from 0.20 to 2%, chromium from 10% to 25%. silicon from more 20 than 1% to 6%, nickel from 0.65% to under about 4%, and iron from about 52% to about 87%; the silicon being in excess of about 2.5% when the chromium is in the lower portions of its range.

6. A valve for an internal combustion engine 25 comprising the alloy set forth in claim 5.

7. An alloy steel for use in exhaust valves of internal combustion engines having in its soft annealed condition a substantially sub-martensitic micro structure and characterized by its high 30 resistance to corrosive loss when subjected to attack by lead oxy bromide at valve operating temperatures; said steel comprising carbon from 0.20% to 2%, chromium from 10% to 25%, silicon from 2% to 4%, nickel from 1% to under 35 about 4% but not in excess of about one-fifth of the chromium and silicon taken together, and iron from about 55% to about 86%.

8. An exhaust valve for an internal combustion engine comprising the alloy set forth in claim 7. 40 9. An alloy steel for use in valves of internal combustion engines having in its soft annealed condition a substantially sub-martensitic microstructure and characterized by its high resistance to corrosive loss when subjected to attack 45 by lead oxy bromide at valve operating temperatures; said steel containing carbon more than 0.20% to 2%, chromium from 10% to 25%, silicon from more than 2% to 6%, nickel from 0.65% to under 4% and iron from 52% to about 87%.

10. A valve for an internal combustion engine comprising the alloy set forth in claim 9.

WALTER R. BREELER.

CERTIFICATE OF CORRECTI ON.

Patent No. 2, 015,991. October 1, 1935.

WALTER R. BREELER.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, second column, line 69, strike out the capital letter "0."; and line 70, for "58%" read 0.58%; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

' Signed and sealed this 5th day of November, A. D. 1935.

Leslie Frazer

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