US2382273A - Copper bearing stainless steel - Google Patents

Description

Aug. 14, 1945. R. THIELEMANN ,38 ,273

COPPER BEARING s'rAINfiEss STEEL Filed April 28, 1944 Inventor:

Rudolf" H.Thie| e ann,

His Attorney.

Patented Aug. 14, 1945 COPPER BEARING STAINLESS STEEL Rudolf H. Thielemann, Portland, reg., asslgnor to General Electric Company, a corporation of New York Application April 28,1944, Serial No. 533,163

(cut-P125) 1 claims.

The present invention relates to stainless steel and more particularly to a modified stainless steel alloy containing copper and adapted for use in gas turbines, axial flow compressors, jet propulsion apparatus and the like.

Heretofore the production ofsatisfactory compressor blades has been one of the serious problems in connection with the manufacture of axial flow compressors for gas turbines and jet-propulsion equipment. The number of such blades employed in a compressor depends of course upon the size and capacity of the compressor and may vary from about 500 to 2000 blades, one half of which are stationary and the other half rotary.

The shape and dimension of the blades tend to make them very difllcult to machine. In cross section the blades have an air foil shape and they Carbon .12 max.

' Chromium 12-14 Tungsten 2.5-3.5 Manganese .50 max. Nickel 1.8-2.2 Silicon .50 max. Phosphorus .025 max, Sulphur .025 max. Iron Balance are usually twisted about their longitudinal axis.

A dovetail structure is providedon one end of the blades so that they maybe secured to a supporting member such asa rotary wheel or the like. The length or the blades vary from about one to eight or ten inches while the width may vary from something less than one inch up to about two or three inches depending upon the design. The trailing'edge of the blade is very thin and for design reasons it is desirable to make that edge less than .010" thick. Because or the complex shape and thin section, it is desirable to make the blades by the lost wax or precision casting technique commonly employed in the manufacture of dentures and the like.

The single figure of the drawing is a'perspective view of a compressor blade and support adapted for use in a gas turbine or jet propulsion apparatus. It comprises a blade I having an enlarged end 2 comprising a dovetailed portion I whereby the blade may be secured to a suitable supporting member 4. I

From a metallurgical point of view the blade material should be at least semi-stainless to resist rusting and corrosion. It should also have a high tensile strength, high elastic limit, good ductility, high fatigue strength, high internal damping capacity, and should be readily mebut because of the high chinable. A steel having such properties may have the following composition:

This steel composition is primarily a forging alloy and has desirable properties in the forged and heat treated condition. However, it does not possess good casting properties; for example it has a high melting point. is very sluggish and the thin edged blades can be cast only if the metal is preheated to temperatures of about 150 to 200 F. above its normal casting temperature. when this is done complete blades may be cast, temperature employed the shrinkage is excessive. Also. the hot shrink causes defects in the castings and the percentage or rejected casting as a result of X-ray examination is very high. It maybe stated therefore that it is practically impossible to successfully cast blades having the above noted composition and employing precision casting technique.

In carrying out the present invention I employ a modified stainless alloy having the following composition:

Carbon .10-.20 Chromium 12-14 Tungsten 2.5-3.5 Manganese -100 Silicon .20-.80 Nickel 1.8-2.2 Copper 5-8 Iron Balance except for normal impurities.

' The preferred composition contains not more than .12% carbon. about 13% chromium. about 3% tungsten, not more than .5 70 manganese, not more than silicon, 2% nickel and 1% copper. Phosphorus and sulphur may be present in the alloy but should be kept as low as possible. For example, the alloy preferably should not con- .tain more than 025% phosphorus and not more than 025% sulphur. My improved alloy has desirable fluidity and casting properties and is particularly adaptedfor use in the precision casting process. One per cent of copper greatly increases the fluidity of the alloy and after a heat treatment at about 700 C. the alloy has unusually high ductility and physical properties. While the useful percentage e of copper employed may vary from .5 to 3% an addition of 1% provides most satisfactory results. Additions above 1.5%

produces some precipitation hardening accom-. panied-by a reduction in ductility. The follow-- lng table represents the physical properties of the alloy in the as-cast condition and after a heat treatment for two hours at 700 C.

After having been heat treated as indicated the cast blades are so ductile that they can be sharply bent 90 or 120 without cracking.-

What I claim as new anddesire to secure by Letters Patent of the United States, is:

1. An alloy containing about .10 to .20% carbon, about 12 to 14% chromium, about 2.5 to 3.5% tungsten, about .20 to 1.00 manganese, .20 to .80% silicon, about 1.8 to 2.2% nickel, about .5 to 3% copper, with the remainder substantially all iron.

iron.

aseaers 2. An alloy containing about 13% chromium, about 3% tungsten. about 2% nickel and about 1%. copper and containing fractional percentages but not more than .12% carbon, not more than manganese, not more than .50% silicon, not more than 025% phosphorus, and not more than 025% sulphur, the remainder of the alloy being substantially all iron.

3. An alloyconsistinz of about .10 to 20% carbon, about 12 to 14% chromium, about 2.5 to

3.5% tungsten, about .20 to 1.00% manganese,

about .20 to 00% silicon. about 1.8 to 2.2% nickel, about .5 to 3% copper, the remainder being substantially all iron, said alloy having been heat treated at a temperature of about 700 C. and slowly cooled therefrom.

51. A process for heat treating an alloy consisting'oi about .10 to 20% carbon, about 12 to 14% chromium, about 2.5 to 3.5% tungsten, about .20 to 1.00% manganese, about .20 to .80% silicon, about 1.3 to 2.2% nickel, about .5 to 3% copper, the remainder being substantially all iron, said process comprising heating the alloy for about two hours at a temperature of about 700 C. and thereafter slowly cling the alloy.

5. A compressor blade for gas turbines. aui flow compressors, Jet propulsion apparatus or the like, said blade comprising an alloy containins .10 to 20% carbon, about 12 to 14% chromium, about 2.5 to 3.5% tungsten, about .20 to 1.00% manganese, about .20 to silicon, about 1.8 to 2.2% nickel, about .5 to 3% copper, the remainder being substantially all iron.

0. A precision casting having the following composition: about .10io.20% carbon, about 12 .to 14% chromium, about 2.5 to 3.5% tungsten, about .20 to 1.00% manganese, about .20 to .80%

silicon, about 1.8 to 2.2% nickel, about .5 to 3% copper, the remainder being substantially all '7. A precision cast alloy having the following composition, about .10 to-.20% carbon, about 12 to 14% chromium, about 2.5 to 3.5% tungsten, about .20 to 1.00% manganese, about .20 to .80%

' silicon, about 1.8 to 2.2% nickel, about'.5 to 3% copper, the remainder being substantially all iron,

, said casting having been heat treated at 700 C.

' RUDOLF H. THIELEMANN.

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