US2319250A - Heat treated copper-nickel-molybdenum steel article and process of making the same - Google Patents

Description

, ma s 18, 1943 UNITED STATES fPATENT OFFICE HEAT TREATED COPPERHNICKEL-MOLYB- DENUM STEEL ARTICLE AND rnocnss OF MAKING THE SAME John Mitchell, Chicago, Ill.

No Drawing. Application July 17, 1941, Serial No. 402,850 7 '7 Claims.

ties together with higher ultimate strength .without loss of ductility.

Further objects and advantages of the present invention will become apparent as the description proceeds-and the features of novelty will be pointed out in detail in the appended claims.

loys. It is adapted particularlyto applications where the maximum corrosion resistance is, required when the parts are subject to tensile stresses, compressive stresses, torsional stresses,

bending stresses, and/or alternations of each, in

the presence of corrosive media; existing'individually as salt or saline waters, sulphuric or hydrochloric acids or existing as combinations of such mineral acids and/or in the presence of hydrogen sulphide gas, and/or crude petroleum oils, and the present alloy possesses highly improved corrosion fatigue, together with the requisite high strength and ductility.

The alloy of the present invention contains carbon from about 0.03% to about 0.40%; manganese 0.21% to about 4.00%; phosphorus from the usual amounts present in all steels, i. e., from In its specific aspects, the present invention pertains to a copper-mckel-molybdenum steel; and while sucker rods may be regarded as a specific adaptation of the invention, it will be apparent that it is adapted for many uses which require high strength combined with high ductility and res stance to corrosion under stress.

Taking sucker rods as a specific example, it

y e note that ordinarily corrosion-fatigue-.

resisting sucker rods are made from steels of approximately 0.20% carbon, 0.70%, manganese, .7 nickel, 0.20%-0.30% molybdenum, the al- 10y being normalized to produce 85,000-90,000 psi ultimate strength with high ductility or normalized and drawn to produce approximately 80,000-85,000 psi ultimate strength with high ductility. These sucker rods are produced also from steels called low metalloid steels or irons containing low carbon (approximately 0.07%),-

manganese 0.20% maximum, ickel I 3.50%. molybdenum 0.25%, quenched an tempered to approximately 65,000 psi with accompanying high ductility. Both of these steels function well in corrosive media under stress, the former permitting the smallest possible rod size due to its strength with fair corrosion resistant results.

The latter alloy is superior in corrosion resist-- ance, but is .not always feasible or economical to use in pumping of deep wells due to the low strength which necessitates increased rod size. 4 i The steel of the present invention constitutes a definite improvement over the foregoing alabout 0.005% to about 0.20%; silicon up to about 0.50%; nickel from about 0.50% to about 5.00%; copper from about 0.50% to about 2.00%;

and molybdenum up to 0.5%, the balance being v substantially all iron.

'A typical analysis and physical properties of the present improved steel are as follows:

Carbon 0.08%; manganese 0.32%; silicon 0.24%; phosphorus p nickel 3.22% copper 1.15%; molybdenum 0.28%, balance substantially iron.

This compositon has the following as-rolled properties:

Yield point, psi 70,000 Ultimate strength, psi 93,000 Elongation in 2 inches per cent-.. 38 Elongation in 4 inches do.... 25 Elongation in 8 inches do 19 Reduction of area do.. 65 Charpy impacts "ft. lbs 55 Izod imp cfs 100 The tensile tests were pulled in full section round.

The desired physical properties of the improved alloy are obtained by heating the steel to a temperature in excess of the Ac: point, followed by cooling in air to approximately 700 F. or less, followed by reheating to approximately 825 F. to 1200? F., followed by cooling in air. This reheating operation to'825" F. to 1200 F. ordinarily reduces the strength of the steel so treated whereas in the improved alloy of this invention the steel or iron actually increases in strength with no appreciable decrease in ductility. Where steels or irons increase in strength in this operation, theterm accelerated age hardening or precipitation hardening applies, either of which is referred to hereinafter as normalizing and drawing, or where the hot-rolled bar is drawn.

Typical properties of-the improved composition as normalized from 1650 F. are as follows:

Yield point, psi 62,000 Ultimate strength, psi 86,900 Elongation in 2 inches per cent 40 Elongation in 4 inches do 28 Elongation in 8 inches do 21 Reduction of area do 65 Charpy impacts ft. lbs 56 Izod impacts 'do 111 Typical physical properties when normalized at 1650 F. and drawn at 1000" F., or asrolled,

air-cooled and drawn .at 1000 F. are as follows:

Yield point, psi 70,000 Ultimate strength, psi- 94,000 Elongation in 2 inches per cent 33 Elongation in 4 inches do 21 Elongation in 8 inches do 15 Reduction of area do 62 Charpy impacts ft. lbs 54 Izod impacts do 104 All the above tensile properties were determined on the full section of A" round bar. The Izod tests were machined to standard dimensions after treatment.

In the foregoing, the term normalized refers to heating above the A03 point and cooling in air; the term normalized and drawing referring to heating above the A03 point, cooling in air followedby reheating to any temperature below the A01 point, followed by cooling in air; the term quenching and tempering as used herein referring to heating to a temperature in excess of the AC3 point, followed by sud-dent cooling in a liquid medium, followed by reheating to any temperature below the A01 point, followed by cooling in air.

In accordance with the present invention, the desired physical properties are obtained by heating the improved alloy to a temperature in excess of the A03 point, followed by cooling in air to approximately 700 F. or less-followed by reheating to approximately 825 F. to approximately 1200" F., followed by cooling in air. While in the case of the steels of this type of the prior art, this reheating to 825 F.-1200 F. ordinarily reduces the strength of the steel so treated, in the case of the steels of the present invention the reheating actually increases their strength with no appreciable decrease in ductility.

The proper balance of the alloying elements of the present invention when normalized and drawn, produces in sizes up to about one inch cross section an ultimate strength of about 95,000 psi. This is 30,000 psi in excess of the values obtainable with low metalloid irons and also is in excess of the normalized steels commonly used for the purposes for which the present improved alloy is suitable. As to corrosion fatigue, the actual comparison of the present improved alloy in corrosion fatigue tests subjected to an outer fiber stress of 30,000 psi in the presence of a corrosive medium simulating the composition of natural occurring oil well liquids and hydrogen sulphide gas, with air excluded, has run 2,000,000

cycles of stress to failure as compared with 1,000,000 cycles ordinarily obtained with the said standard alloys.

As has been indicated above herein, the present improved steel is adapted particularly to applications where the maximum corrosion resistance is required. when the parts are subject to tension, compression, torsoin, bending stresses, and/oralternation's of each; in the presence of corrosive mediaexisting individually as salt or saline waters, sulphuric or hydrochloric acids, or existing as combinations of such mineral acids and/or in the presence of hydrogen sulphide gas.

The present improved alloy also is adapted to chain steel or similar applications where the parts come in contact with hot metal, reaching temperatures up to 1000 F. which reduce the strength of quenched and tempered chain steels of commonly used compositions, but which, on theother hand, do not afiect the strength of the present improved steel.

It will be seen from the foregoing that the specific heat treatment to obtain the maximum properties of the improved alloy consists in normalizing by heating to any temperature above the A03 point, and cooling in air, this normalizing being followed by reheating to a temperature between about 800 F. to about 1200 F., and cooling in air, or by using the single treatment of drawing, between 800 F. to 1200 F. Without any prior treatment, when hot-rolled material is hot-finished above the A3 point.

Thus, for example, in accordance with the present invention there are produced heat treated steel articles having excellent corrosion resistance as indicated above, such articles being composed of carbon approximately 0.1%, manganese approximately 0.4%, copper approximately 1%, nickel approximately 3.5%, and molybdenum approximately 0.2%, the balance being iron except for normally present impurities, the articles being characterized by a normalized structure produced by normalizing the steelfrom a temperature above its Aca point, then reheated to between approximately 800 F. to approximately 1200 F. and then cooled in air.

,As illustrative of such articles, there are pro- I temperature between 800 F. and 1200 F., cooled drawn structure imparted by being normalized from above the A03 point of the steel, reheated to a temperaturebetween 800 F. and 1200 F., cooled again in air and drawn at a temperature between 800 F. and 1200 F.

. approximately 3.5%, and molybdenum approximately 0.2%, the balance being iron except for normally present impurities, the said article being characterized by a normalized structure produced by normalizing the steel from a temperature above its Aca point, then reheated to between approximately 800 F. toapproximately 1200 F'., and then cooled in air.

4. A method of producing a steel article which is highly resistant to corrosion in the presence of salt water, hydrogen sulphide gas, and mineral acids, the said article'being composed of a steel consisting of not more than approximately 0.30% carbon, from approximately 0.5% to approximately 1% of manganese, from approximately 0.5% to approximately 1.25% copper,-- from approximately 1.5% to approximately 3.5% nickel, from approximately 0.2% to approximately 0.5% molybdenum, balance substantially all iron, which method comprises heating the steel in "asis highly resistant to corrosion in the presence of salt water, hydrogen sulphide gas, and mineral acids, the said article being composed of a steel consisting of not more than approximately 0.30% carbon, from approximately 0.5% to approximately 1% of -manganese, from approximately 0.5% to approximately 1.25%.. copper, from approximately 1.5% to approximately 3.5% nickel, from approximately 0.2% to approximatey 0.5% molybdenum, balance substantially all iron, which method comprises hot rolling and hot finishing the steel above its Ac: point. and drawing the steel at between 800 F. to 1200 F.

6. A heat treated steel article composed of not more '-than 0.3% carbon, 'from approximately 0.5% to approximately 1% manganese, from aprolled or as-iorged condition to temperatures proximately 1200 F., and drawing within this temperature range.

5. A method of producing a steel article which proximately 0.5% to approximately 1.25% copper, from approximately 1.5% to approximately 3.5% nickel and from approximately 0.2% to approximately 0.3% molybdenum, remainder iron except for normal impurities, the article being characterized by having a normalized structure imparted by being normalized from above the Ac: point of the steel, reheated to a temperature between 900 F. and 1200 F., and cooled.

7. The method .of producing a heat treated steel article composed of not more than 0.3% car bon, from approximately 0.5% to approximately 1% manganese, from approximately 0.5% to approximately 1.25% copper, from approximately 1.5% to approidmately 3.5% nickel, and from approximately 0.2% to approximately 0.3% molybdenum, remainder iron except for normal impurities, which method consists in heating the steel in excess of the Ac: point, cooling to 700 F. r

or lower, reheating .to between approximately 800 F. to approximately 1200 F. and then 0001- ing.

JOHN MITCHELL.