US2513935A - Alloy steels - Google Patents

Description

Patented July 4, 1950 ALLOY? ZSTEELS Geoffrey Thomas Harris, Sheffield, England, as-

signor, by mesne assignments, to William Jessop & SonsLimited, Sheffield, England, a British company N Drawing. Application December 10, 1948, Se-.

rial No. 64,703. In Great Britain December 13,

4 Claims. (Cl. 75-126) This invention relates to alloy steels and has for its object the provision of an alloy steel having good creep strength and. resistance to scaling at temperatures in the region of 600 C.

placement of niobium in whole or in part by tantalum.

The following is an example of a particular alloy in accordance with the invention:

The invention is particularly concerned with improving the creep strength and resistance to Per cent scaling of alloy steels of the kind frequently re- Carbon 0.16 ferred to as stainless irons. The creep Manganese 0.27 strength of such stainless irons, which do not Silicon 0.32 normally contain molybdenum or tungsten can, c r m 1 as is known, be improved to a limited extent by Molybdenu M3 the addition of molybdenum or tungsten. For vanadium 0374 example the following table shows three alloys Niobium 0 and the stress required to produce a minimum creep rate of 10- per hour at a temperature of the remainder being iron and usual impurities. 550 c, Tests on this alloy gave the following results. Stress required Bar material was forged and heat treated by 1 chmmiumamn 24 q enchin in oil from 1200" C. followed by tem- 12% chromium iron+0 5% molybdenum 7 2 pering at 720 C. creep test under a stress of 12% chromium-iron+3% tungsten 6.3 5 tons per s u Inch at a e un e 50 gave a minimum creep ra e, a s e con- Howevternsteelgorrlnadse hgi eialfsa g ggg ggg :2 stant rate of creep attained in the stage of secpl'esen 1 Ven a o dar cree of a roximatel 1.9 10- er quire E of 15 tons per square inch t0 h gur. This zreep rag produced under a str ess duce mmlmum croeep rate of 10-6 per hour at a of 10 tons per square inch is produced in pretemperatllre of 550 viously known non-austenitic teels by stresses in Accordlpg 9 my inventiim an alloy compnses the range of 2 to 8 tons per square inch. A fur- P followmg mgredlents within the ranges ther creep test on the alloy under a stress of 15 honed: tons per square inch at a temperature of 550 C. P cent 39 gave a minimum creep rate of approximately Carbon 10- per hour. The alloy also possesses superior Ma a 0-0541) scaling resistance properties to those shown by Silicon 4 the stronger type of non-austenitic alloy, and the Chrommm 9-0451) alloy therefore combines high scaling resistance Molybiienum with high creep strength. The heat treatment Vanadmm 02-2-0 can be varied to suit requirements and even Niobium and/0r tantalum higher creep strengths can be attained by quenching from a temperature higher than g ffig zg fig 2: g g gg gg g azg o 1200" 0., whilst a somewhat lower creep strength since in niobium ores tantalum is usually combined with greater ductility and toughness present and as it is difilcult to separate niobium can be obtamed by quenching from lower and tantalum, in practice small amounts of tanperature' u talum are usually present in association with H Steels accordmg to this mventlon 841:9 niobium. For example, commercial fen- 1 particularly useful for the manufacture of artibium contains roughly 5% bi d up t cles in which a good creep strength and resist- 5 tantalum. Thus my invention, so far as t ance to scaling at high temperatures is required. addition of niobium is concerned includes the Such articles are, for example, rotors and blades presence of small amount of tantalum usually o as urbines. found with niobium. It also includes the re- Having thus described my invention, what I 3 claim as new and desire to secure by Letters Patent is:

1. Alloy steels comprising the following ingredients in the proportions specified the remainder being iron and usual impurities.

2. An alloy steel comprising the following in-* gredients within the ranges specified: carbon .05

to .5%, manganese and ilicon each within the.

range of .05% to 1.0%, chromium 9 to 15%, molybdenum 0.2% to 1.2%, vanadium 0.2 to 2%, and at leastone element selected from the group consisting of niobium and tantalum .05 to not over 1.5%, substantially all of the remainder being iron and usual impurities, said composi- 4 tion having a high creep strength and. resistance to scaling at temperatures of the order of 600 C.

3. An alloy steel as defined in claim 2 containing tungsten up to one per cent.

4. An alloy steel of good creep strength and resistance to scaling at high temperatures comprising the following ingredients in approximately the following proportions: carbon .16%, manganese andsilicon each .3%,..chromium 11%, molybdenum 53%, vanadium 375% and at least one element selected from the group consisting of niobium and tantalum 17%, substantially all the remainder being iron and usual impurities.

GEOFFREY THOMAS HARRIS.

REFERENCES CITED "The following references are of record in the file of this patent:

Claims (1)

1. ALLOY STEELS COMPRISING THE FOLLOWING INTGREDIENTS IN THE PROPORTIONS SPECIFIED