US2378992A - Articles for use at low temperatures - Google Patents

Description

Patented June 26, 1945 Russell Franks, Niagara Falls, N. Y.,- assignor to Electro Metallurgical Company, a corporation of West Virginia No Drawing. Application January 16, 1943,

Serial N0. 472,597

9 Claims. (01. 75-123) This invention relates to'steel articles for use at low temperatures.

A demand exists in industry for steels forl'use in the fabrication of apparatus for use at lowtemperatures, for example for refrigerating equipment or for apparatus used in the handling of liquefied gases such as oxygen, nitrogen, or

air. Many steelswhich have excellent strength and toughness at normal atmospheric temperatures become brittle when exposed to temperatures below zero on the centigrade scale, and few ferrous materials have the requisite toughness to withstand shock at the exceedingly low temperatures encountered in handling liquefied air or oxygen. Stainless steels of the type containing about 18% chromium anrk8% nickel have excellent toughness even at temperatures in the neighborhood of l83 C., and have been widely used in liquid oxygen equipment, but these steels are relatively expensive. Although nonferrous metals 'and alloys are not as susceptible as ferrous materials to loss of toughness at low temperatures, in general, their strength is not great.

It is the chief object of'this invention to provide articles for use at low temperatures which articles -are composed of steel which possesses the gbility to withstand shock at Very low temperaures.

Th invention by means of which this object is achieved is based on the discovery that austeniti'c manganese steels which contain substantial proportions of manganese within certain narrow, critical limits and a minor proportion of at least one austenite-stabilizing element selected from the group consisting of nickel and copper, with or without chromium in a proportion up to 16%. have the ability to withstand shock at sub-zero temperatures The invention comprises articles for use at low. temperatures composed of such steels.

More specifically, the invention comprises articles for use at low temperatures, which articles are composed of steel containing about 15% to 20% manganese, 0.2% to 8% of at least one austenite-stabilizing element selected from the group 45 consisting of nickel and copper, up to about 16% chromium and the remainder chiefly iron. Preferably, the steel contains both nickel and copper. Ii nickel alone is used, the steelshould contain about 0.5% to (preferably 1% to 5%) of this element. If copper alone is used, the steel, should contain about 0.25% to 2% of this element, but if both copper and nickel are used, the copper content may be as high as 3%. Ordinarily, the presence of more than 3% of copper should be avoided because of the detrimental effect of copper on the hot working properties of the steel.

, The presence of chromium in the steel not only improves its toughness at low temperatures but also enhances its resistance to corrosion. Where corrosion-resistance is not important, chromium may be omitted altogether, but in such case the sum of the nickel and copper content should be at least 4%, and preferably at least 5%, of the steel tosecure the desired low temperature toughness. Where resistance merely to progressive rusting is desired, the steel should contain about 0.25% to 8%, preferably 1% to 4%, chromium. In steels containing chromium in this range, the sum of the nickel and copper contents need not be as high as when chromium is not present in the steel. Where a high degree of resistance to corrosion is required of the articles of the invention in addition to low temperature toughness, the

steel of which they are composed should contain about 8% to 16% chromium, and in such case for the greatest degree of toughness at low tempera- 20 ture, the steel shouldcontain about 012% to 3% nickel or about 0.2% to 2.25% copper or both nickel and copper. A preferred lower limit for nickel or copper or both is about 0.25%. Generally, best results are obtained in all of these steels if nickel or both nickel and copper are present, but in the higher chromium steels a small proportion of either will suflice.

The carbon content of the steel of which the articles of the invention are composed should not exceed about 0.5% and is preferably about 0.01%

to 0.35%. Nitrogen in a proportion up to about 0.15% and phosphorus up'to about 0.4% (pref erably not more than about 0.2%) may be present in the steel, nitrogen in particular having a beneficial effect on its toughness. There will also ordinarily be normal percentages of residual deoxidizers, scavengers and grain refiners such as silicon and calcium present in the steel.

The articles of the invention should be an-' I .nealed before-exposure to low temperatures, suitably by heating them at a temperature above about 900 C. and then rapidly cooling them in water or air. r

The toughness atlow temperature of aus'tenitic man anese steels containin various amountsof nickel, copper, and chromium is illustrated by the test data set forth in Table I. Inrthis table the impact resistance at room temperature and w at 183 C. of the steels as determined in the standard Izod impact test is given in foot pounds. The specimens tested at l83 C. were cooled to that temperature by immersing them in liquid air for one-half to one hour and then were quickly transferred to the impact machine and tested.

Before testing, all specimens were annealed by heating them for ten to twenty minutes at 1000 C. to 1050 C(and then cooling them in air.

Table I Composition (remainder iron) Impact resistance Percent Percent Percent Percent Percent Room Mn Ni Cu Cr C temp.

14 Nil Nil Nil 0. 30 8 0. 75 16.5 Nil Nil Nil 0.20 32 '3 18 Nil Nil Nil 0.30 65 2 17 2.0 Nil Nil 0.29 96 16 16 4.6 Nil Nil 0.30 94 30 17 2 1 Ni] 0.20 103 20 16.5 2 2 Nil 0.10 90 46 16 2 2 Nil 0.40 70 32 17 3 1 Ni] 0.10 107 41 16 2 1 3 0.2) 102 28 17 2 2 3 0.10 97 63 17. 5 2 Nil 5. 07 0. 2) 93 42 16. a 0. 54 Nil 12. 9 0. 15 105) 60 16.6 1.10 Nil 13.2 0.15 100 07 16. 2 2. 10 N 11 13. 2 0. 14 100 90 16.5 Nil 0.75 12.8 0.13 100 67 I 16.6 0.58 0.64 12.9 0.13 100 64 16.3 1.10 0.60 13.0 0.12 98 78 The data in Table I show the drop in toughness of the plain high manganese steel at low temperature and that the addition of copper or nickel or both markedly improves the toughness of high manganese steel at low temperature. Even further improvement is shown by steels containing chromium inaddition to nickel or copper or both.

Tensile test data set forth in Table II below demonstrate that the ducitility or high manganese steel, as measured by the percentage elongation in a two inch gauge length, is enhanced by the presence of one or both of the elements nickel and copper, with or without chromium.

Table II Composition (remainder iron) Yield Tensile 5:; Per- Per- Per- Per Perg g g ei. in cent cent cent cent cent 2" Mn Ni Cu Cr C 14 N11 N11 N11 0. 30 38, 500 110, 300 14 16. 5 N11 N11 N i] 20 36, 100 127, 300 24 17 2 Nil Ni] 0.29 35,000 ,000 60 17 4. 5 N11 N11 0. 28 31, 800 112, 900 62 10. 5 2 1 N11 0. 500 111, 300 59 16. 5 2 2 N11 0. 10 28, 000 100, 700 62 16 2 2 N11 0. 40 37, 100 1 000 69 16 2 1 3 0. 35, 100 120, 400 I 61 16 2 2 3 0. 13 600 136, 500 65 17. 5 2 N11 5. 07 0. 20 40, 700 120, 000 53 16. 5 N11 0. 75 12. 8 0. 13 1110 123, 000 63 16. 5 0. 54 N11 12. 9 0.12 36, 000 120, 500 63 16. 5 1. 1 N11 13. 2 0. 15 38, 500 124, 500 67 10. 3 1. 1 0. 6 l3 0. 12 35, 000 08, 000 63 16. 2 2. 1 N11 13. 2 0. 14 v 36, 000 110, 000 63 1 6. 5 2 1. 5 12 0.10 000 101, 500 58 The test data shown in Table II were obtained on standard tensile'test specimens at room temperature, the yield strength at 0.2% offset being determined in accordance with United States Navy Department specification No. 47521. Inthe table yield strength p. s. i. represents the yield strength in tension measured at 0.2% permanent,

set in pounds per square inch; "tensile strength less steel weldingrods containing about 5% to 30% chromium and 5% to 30% nickel, for instance, using rods containing 18% chromium and 8% nickel or 24% chromium and 12% nickel or 25% chromium and 20% nickel.

.which article is composed of a steel containing about 15% to 20% manganese to render said steel austenitic, about 0.2% to 8% of at least one austenite-stabilizing element selected from the group consisting of nickel and copper, thecopper content not exceeding about 3% of the steel, 0.01% to 0.5% carbon and the remainder iron and incidental elements having to substantial adverse eflect on the low temperature toughness of said steel.

2. A steel article foruse at low temperatures, which article is composed of a steel containing about 15% to 20% manganese to render said steel austenitic, about 0.2% to 8% of at least one austenite-stabilizing element selected from the group consisting of nickel and copper, the copper content not exceeding about 3% of the steel, up to about 16% chromium, 0.01% to 0.5% carbon and the remainder substantially all iron.

3. A steel article for use at low temperatures,

which article is composed of a steel containing about 15% to 20% manganese, about 0.5% to 5% nickel, 0.01% to 0.5% carbon and the remainder substantially all iron.

4. A steel article for use at low temperatures. which article is composed of a steel containing about 15% to 20% manganese, about 0.2% to 8% of at least one austenite-stabilizing element selected from the group consisting of nickel and copper, the copper content not exceeding 3% of the steel, about 0.25% to 8% chromium, 0.01% to 0.5% carbon and the remainder substantially all iron.

5. A steel article for use at low temperatures, which article is composed of a steel containing about15% to 20% manganese, 1% to 5% nickel,

0.25% to 2% copper, 0.25% to 8% chromium, 0.01% to 0.5% carbon and the remainder substantially all iron.

6. A steel article for use at low temperatures, which article is composed of a steel containing about 15% to 20% manganese, 1% to 5% nickel, 0.25% to 2% copper, 1% to 4% chromium, 0.01% to 0.35% carbon and the remainder substantially all iron.

'7. A steel article for use at low temperatures, which article is composed of a steel containing about 15% to 20% manganese, 0.2% to 3% nickel, 0.2% to 2.25% copper, 8% to 16% chromium, 0.01% to 0.5% carbon and the remainder sub.-

- stantially all iron.

8. A steel article resistant to progressive rusting which in its normal use is required to withstand shock at temperatures below zero on the centigrade scale, which article is composed of a steel containing about 15% to 20% manganese, 0.25% to 5% nickel, 0.25% to 2% copper, 0.25% to 8% chromium, 0.01% to 0.5% carbon, the remainder substantially all iron.

9. A corrosion-resistant steel article which in its normal use is required to withstand shock at temperatures below zero on the centrigrade scale, which article is composed of a steel containing about to 20% manganese, 0.25% to 3% nickel, 0.25% to 2.25% copper,- 8% to 16% chromium, 0.01% to 0.5% carbon, the remainder substantially all iron.

- RUSSELL FRANKS.

CERTIFICATE OF CORRECTION. Patent No. 2,578,992. June 26, 19h5.

RUSSELL FRANKS.

It is hereby certified that error appears in the printed specification of the above numb ered patent requiring correction as follows: Page 2, first column, line 51 for "d i ti lity" read "ductility"; line 6'5, for "pound" read -pounds-; and second column, line 15, for "having to" read -'-having no-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21d day of October, A. D. 1914.5.

Leslie Frazer (Seal) First Assistant Commissioner of Patents.