DE2051609A1 - Austenitic, stainless steel - Google Patents

Description

Austenitic, stainless steel

The invention relates to austenitic, stainless, chromium, manganese, nickel and nitrogen containing Steels with relatively low nickel and high nitrogen contents. These steels stand out due to a unique combination of properties that make them suitable for use in cryogenic applications enable. These areas of application require good low temperature toughness and long Fatigue life in chloride-containing, corrosive Media in which good stress corrosion resistance is required. According to the invention achievable combination of properties also allows the use of such steels for production string-like objects which - if they are rapidly cold-reduced - have a high tensile strength exhibit. The steel alloys according to the invention are particularly suitable, inter alia, for production welded pressure vessels for cryogenic operation, with high strength at low temperatures

rature

100819/1220

temperature is required in addition to good toughness and stability at cryogenic temperatures. Further the steel alloys according to the invention can be used for the production of spring wire, which can be achieved by one-step drawing with an approx. 40 to 50% cold reduction up to one Harden tensile strength of about 1515 to 1725 MN / m leaves.

A temporary shortage of nickel and its relatively high costs had encouraged the experts to to develop nickel-free or low-nickel austenitic alloys. Numerous such alloys have been investigated in recent years.

For example, in a publication by R. Franks, W. Binder and J. Thompson in "ASM Preprint 29", Volume 47, 1954, the structure of steels with about 0.1 % carbon and about 0.15% nitrogen with chromium contents of 12 to 18 %, manganese contents of 0 to 22% and nickel contents of 0 to 14% are described. The authors of the above-mentioned publication came to the conclusion that with chromium contents above 15% a fully austenitic structure cannot be achieved with manganese alone, despite the fact that carbon and nitrogen expand the austenitic region in steels of this composition and in are better than wraps in this regard.

From U.S. Patent 2,778,731 there is one Austenitic steel alloy with low nickel content

109819/1220

known content consisting of 17 to 18.5 % chromium, 14 to 20% manganese, 0.05 to 1.00% nickel, 0.06 to 0.15% carbon, 0.25 to 1.0% nitrogen, 0 25 "to 1.0% silicon and the remainder of iron. It is claimed that the steel known from the cited patent specification has high strength and a high work hardening rate and that its mechanical properties match the AISI types 301 and 302. Such a steel of the composition: Chromium 17.0 to 19> 0%,

Manganese 14.5 to 16%, nickel maximum 0.75%, i

Carbon 0.08 to 0.12%, nitrogen at least 0.35%, silicon at most 0.75 %, the remainder iron is currently sold by US Steel Corporation under the trade name TENELOE.

A publication by J. Heger in "ASTM Special Technical Publication 369" in 1963 summarized the earlier literature. It was found that prior to the development of the products marketed under the trade designation "Tenelon" nitrogen solubility of the steel, the material is exceeded geweiligen g th is when 18% chromium, 6% manganese, and nickel containing 4% Stänlen nitrogen in amounts greater than 0.25% was incorporated. Carney's experiments are reported in the cited publication, from which it emerges that nitrogen contents of up to 0.50% can be achieved in steels containing 18% chromium, 15% manganese and the remainder nickel without exceeding the nitrogen solubility. In other words, another 0.25 % nitrogen can be kept in solution

will.

109819/1220

by replacing the 4% nickel with 9% more manganese. This increased nitrogen uptake is not only attributed to the additional manganese; rather the conclusion is drawn that the combination of chromium and manganese increase nitrogen solubility more than either of the two elements alone.

Other recently developed, high-strength, austenitic alloys with a low nickel content are, for example, Type 16-16-1 and Allegheny-Ludlum Type 205. Type 16-16-1 contains 15 to 16% chromium, 16 to 17.5% Manganese, less than 1% nickel, 0.10 % carbon, a maximum of 0.20% nitrogen, 0.20 to 0.70 % silicon and the remainder essentially iron. Allegheney Type 205 contains 16 to 18% chromium, 14.0 to 16.0% manganese, 1.1 to 2.0% nickel, 0.12 to 0.25% carbon, 0.32 to 0.40 % nitrogen , 0.2 to 0.7% silicon and the remainder essentially iron.

So far it has been assumed that if manganese is used as austenite former instead of nickel, the substitution would have to take place in a ratio of 2: 1, as shown by A. Schaeffler in "Metal Progress Data Sheet", February 1960, page 100-B , Manganese is said to be only half as effective as nickel as an austenite former in alloys with a high chromium content and around 0.10 % nitrogen. The revised section of the Schaeffler state diagram contained in the publication "Metal Progress Data Sheet" shows that with a chromium content of 18% a nickel equivalent of

approximately

109819/1220

about 13% is required to achieve O% ferrite. If the winding content of the alloy is 3 % , the remaining 10% nickel equivalent must obviously come from carbon, nitrogen and manganese. In this revised section of the Schaeffler phase diagram, a certain factor is taken into account for nitrogen, so that nitrogen is not used in the calculation of the remaining nickel equivalent Assuming a maximum carbon content of 0.10% and also assuming that the effectiveness of carbon as an austenite former is 30 times that of nickel, 7% nickel equivalent remains to be replaced by manganese. Thus, according to the previous considerations of the experts, at least 14 % manganese would be required.

It has generally been believed that every 1% chromium can hold about 0.01% nitrogen in solution. Thus, with a chromium content of 18 %, it would be expected that only about 0.18% nitrogen would be kept in solution. Although manganese is known as a nitrogen carrier, no precise relationship has yet been established; from the results contained in a paper by D. Carney in "Blast Furnace and Steel Plant", December 1955, it is concluded that are required 14.5 to 15 ₅ O% manganese, in order at a chromium content of 15% and a nickel content of 0% nitrogen in amounts greater than 0.4 % in solution.

At the present time for a cryogenic

operation

109819/1220

Common austenitic stainless steels are for example AlSI types 304- * 304-N, 316, Armco 21-6-9 and, more recently, U.S. Steel Cryogenic TlKELON.

Although the Type 304 is at cryogenic temperatures has good toughness, it turns into martensite when it is deformed, and hence has a poor fatigue life. Your smelting regulations require nickel contents of 8.00 to 10.50%; consequently Type 304 is relatively expensive. In addition, it has relatively low tensile and yield strength values at room temperature (about 85 or, in the annealed state, 35 ksi), so that the structures or structures made from it may only be burdened very little.

Type 304-N is somewhat stronger than type 304 at room temperature. However, it is subject to cryo-. at temperatures still a transformation into martensite and thus still has a relative poor fatigue life.

Due to its high nickel content (10 to 14%), Type 316 is against conversion to martensite. more stable at cryogenic temperatures; this property is conducive to fatigue life, however, the use of this alloy limits the load-bearing capacity of the structure made from it or the construction made from it quite considerably, since it only has one at room temperature has low strength.

The Armco Type 21-6-9 is at cryogenic temperatures

1098 19/1220

Although they are stable against conversion to martensite, they have the disadvantage that they expensive due to a relatively high Kiekel content is.

The alloy sold under the name "Cryogenic TENELON" with a nominal composition of 0.08% carbon, 16% manganese, 18% chromium, 5.5 % nickel, 0.38% nitrogen, the remainder essentially iron, has good strength values at room temperature , good stability against transformation to martensite at low temperatures and good weldability, but it has the disadvantage that it also has a relatively high nickel content. Furthermore, it has considerably lower impact strength values than type 304 at cryogenic temperatures. Various values of the alloy "Cryogenic TENELON" can be found Iu. a reprint of a publication by CE Spaeder Jr. et al. in Metals Engineering Quarterly, ASM, August 1969, pages 1-5.

Another essential property of stainless steels in numerous fields of application, for example for shaped and / or welded vessels used in the chemical industry, is their resistance to stress corrosion. The residual stresses in such vessels or other objects cannot be eliminated by annealing; these stresses are often large enough to cause cracking under certain circumstances. All of the alloys mentioned with nickel contents of about 5 to about 15 % suffer stress

corrosion cracks

10 & 819/1220

corrosion cracks, if they are hot under load, exposed to media containing chloride.

The invention was based on the object of specifying a relatively low-alloy, fully austenitic, stainless steel with in particular a maximum of 4 % nickel and 15 % manganese, which, due to its critical composition, has a unique combination of properties, namely the ability to be cold-hardened to a very high strength have high strength at room temperature, good (long) fatigue life, good toughness and stability against transformation to martensite at cryogenic temperatures, good general corrosion resistance, good stress corrosion resistance and excellent vision-welding properties.

It has now been found that sbh complies with the task at hand. can dissolve a stainless steel, which consists essentially of 15 _t 5 "to 20 % chromium, 11 to 15% manganese, 1.1 to 4% nickel, less than 0.01 to 0.11% carbon, 0.28 to 0 , 38 % nitrogen, best iron, together with impurities caused by the mineralization, which do not impair the properties of the respective alloy, The ea? - inventive steel - can contain up to a maximum of 0.040 % phosphorus, up to a maximum of 0.0 % sulfur and up to a maximum of 1.0% silicon. Preferably, the steels according to the ErfinduüLg essentially of about 1? to about 1'9% chromium, about 11 to about 13.5% Mäagan, about 1.4 to about 3, 5% nickel, about, £) 5 to about 0.1% carbon, about 0.3-0 Ms, about 0.34 % Stieist # ff 'and

to the

the rest practically made of iron. In contrast to the known teachings, the nitrogen solubility of the steel alloys according to the invention is not exceeded with the preferred maximum manganese content of 13.5% and the preferred maximum chromium content of 19%. Surprisingly, even at the maximum chromium content of 20 % , the alloy is practically free of delta-Iferrite, despite the fact that the preferred maximum manganese content is 13.5% and the preferred maximum Mckel content is 3-5%.

When it comes to a higher general corrosion resistance and high temperature resistance, can have a ratio of up to a maximum of 3> 5% chromium 1: 1 can be replaced by molybdenum. However, the molybdenum obviously lowers the toughness at cryogenic temperatures.

The presence of copper in the steels according to the invention is impractical because copper is in combination with manganese causes hot brittleness in the metal.

Mob and / or <J

Vanadium can be added in amounts of 0.1 to 0.5 % each. Titanium apparently has the same effect, but the addition of titanium is likely to reduce toughness at cryogenic temperatures.

If the heat hardenability is to be increased, boron can be added in amounts up to 0.010%.

the

109819/1220

The elements carbon, manganese, chromium, nickel and nitrogen as well as their chemical equivalents. are critical in any case. If one of these elements is left out or if the critical percentage ranges are not adhered to, one or more of the new property combinations will be lost. The carbon content of the steels according to the invention is preferably at least about 0.03% in order to give the metal the required strength and to act as an austenite former. In certain areas of application, the carbon content can be 0.03% and even 0.01% Tint he steps because you can rely on nitrogen to have a corresponding influence on the properties of the steel. A maximum carbon content of 0.10 % is preferred. Carbon contents higher than 0.11 % are inexpedient since this impairs the general corrosion resistance and weldability as well as the toughness at cryogenic temperatures.

To ensure a completely austenitic structure and to keep the nitrogen in solution, at least 11 % manganese is required. Manganese contents higher than 15% and preferably more than 13.5% are unsuitable since the costs increase as a result of manganese losses during melting and since manganese tends to cause hot brittleness.

Chromium is required in amounts of at least 15.5%, in order to give the alloy the required corrosion resistance and in. Combi- ''

nation

1Ö9819 / 122Ö

nation with manganese to keep the nitrogen in solution. More than 20% chromium can be used with the specified Carbon, manganese, nickel and nitrogen are not tolerated as chromium is a ferrite former and a greater than about 2% ferrite content for reasons of good Toughness at cryogenic temperatures must be avoided. For these reasons it becomes a maximum Chromium content of about 18% is preferred.

The presence of nickel in amounts of at least 1.1% is of essential importance both because of its function as an austenite former and because of its toughness-increasing effect at cryogenic temperatures. Nickel contents higher than 4-.0 % no longer lead to an increase in toughness in an alloy of the specified strength and are consequently unsuitable for the alloys according to the invention. In addition, nickel contents greater than .4 % make such alloys susceptible to stress corrosion fractures. In most industrial applications, an alloy with no more than 3.5 % nickel is preferred. Furthermore, because of the high price of nickel, it is advisable to keep the nickel content as low as the interaction of the other elements with nickel allows without impairing the desired properties.

To achieve high strength at room temperature, at least 0.28% nitrogen is used needed. In addition, nitrogen is a strong austenite former; thus the specified Carbon, manganese and nickel contents

at least

109819/1220

requires at least about 0.28 % nickel. More than about 0.38 % nickel cannot be tolerated, since this reduces the toughness at cryogenic temperatures, melts with gas inclusions are obtained and the weld seams become porous.

The previous explanations show clearly that a balance must be maintained with respect to the amounts of the essential elements and that the interaction of the individual components within given limits results in the presence W to a new combination of properties. It can also be seen from the previous statements that certain changes within the specified limits lead to an alloy with optimal properties for cryogenic use, while other changes lead to an alloy with optimal general-purpose properties, for example for the production of high-strength spring wires.

A preferred alloy for cryogenic areas of application has the unge-B) specified below ferry composition;

0.05% carbon, 13% manganese, 18 ° / o chromium, 3.0% nickel, 0.32% nitrogen, erschmelzungsbe-,-related amounts of phosphorus, sulfur and silicon and the balance iron.

Another preferred alloy for cryogenic use with a particularly favorable combination of high strength at room temperature,

goods

109819/1220

good stability against conversion to martensite and good toughness at 78 ^° K as well as excellent weldability has the approximate composition given below:

0.05 % carbon, 13.5% manganese, 18% chromium, 3.5% nickel, 0.35% nitrogen, up to 0.50 % of an element consisting of vanadium and / or niobium, quantities of phosphorus due to the melting process, Sulfur and silicon and the remainder bisene.

When the alloy according to the invention for production

of objects that are intended to be used as a result of ™

Its size or its complicated shape cannot be relaxed, it should preferably contain less than 4% nickel, namely a maximum of about 3.75% nickel.

A preferred alloy for the production of cold drawn Peder wires with a tensile strength of over 220 ksi has the following composition:

About 0.10 % carbon, about 12 % manganese, about

18.5 % chromium, about 1.5 % nickel, about 0.35 % nitrogen i

substance, quantities of phosphorus, sulfur and silicon due to the melting process and the remainder iron.

The permissible under cryogenic operating conditions loads based on the tensile and yield strength values at room temperature, the percent elongation and reduction at room temperature, impact strength at 78 ⁰ C and the degree of conversion to martensite, measured as magnetic transformation.

With

109819/1220

With alloys according to the invention were compared to known cryogenic. Alloys and to alloys with chromium contents above and below the chromium content of the alloys according to the invention and with manganese contents below the manganese contents of the alloys according to the invention, however with the other components within the for the steels according to the invention specified limits, such Tests carried out. The compositions the various alloys examined are given in Table I below; the properties mentioned are those given in Table I. Alloys are listed in Table II below.

In addition to the investigations into the mechanical and metallurgical properties of the Alloys were samples 1 to 14 and 17 to 22 in boiling magnesium chloride (MgClo) 'on it Stress corrosion behavior investigated. The examinees were made by attaching fusion welds to opposite sides of 25.4 mm round bars. Here were in the outer Fibers of the test specimens caused tensile stresses. While all test subjects in the first group (1 to 14) showed no signs within 24 hours showed cracking was in all of the specimens of the second group (1? to 22) to observe cracking within this time. Of the the main difference in the chemistry of the two groups is the nickel content. From the results These experiments clearly show that with a nickel content of over about 3.75% the Stress corrosion resistance suffers.

All

1098 197 1220

All melts were melted in an induction furnace, thermoformed and at 1340 ° K Annealed for half an hour and then quenched with water.

The results contained in Table II show that the room temperature strength of the alloys according to the invention is considerably higher than that of AISI types 304 and 316 and considerable higher than that of Type 304-N. The toughness of the steels according to the invention at 78 ° K is not as high as the toughness of the

Types 304, 316 and 3O4-U. In this context %

however, it should be noted that the toughness of the steels according to the invention for cryogenic operating conditions completely sufficient, since a minimum value of 20.3 joules in the Charpy impact strength test with a test piece having a V-shaped notch at a temperature of 78 K is considered sufficient.

The table also shows that 5 alloys according to the invention show a slight magnetic conversion when deformed at a temperature of 78 ° K, while the remaining Λ alloys according to the invention show only an extremely low magnetic conversion. In contrast, types 304 and 304-N showed strong magnetism due to conversion to martensite; Type 316 showed (only) a slight conversion.

The U.S. Owns steel cryogenic TENELON alloy despite their considerably higher content of alloy components

109819/1220

gierungsbestandteilen, in particular nickel manganese, room temperature properties and toughness values at 78 ⁰ K ₁ can be compared with the corresponding values of the inventive alloys.

Samples 10 and 11, which contain less manganese than are required for the alloys according to the invention, had an unusually low toughness at 78 ^° K and changed to martensite at room temperature. These results demonstrate the need for a manganese content of at least 11.0 %.

High chromium contents (samples 12 and 13) 'led to a two-phase structure with a large percentage of ferrite and an unusually low impact strength at 78 ⁰ E.

Finally, a chromium content below the required minimum amount showed von'15 "5% sample having a 14 unusable low impact strength at 78 ⁰ K.

109819/1220

Tabel I. O C. Mn 17th Cr 1 , 97 Steels ⁴ " melt 0 i
, 046 11.88 17th , 76 1 , 75 N R7602 sample O , 10 12.07 17th , 86 2 , 74 0.30 R7603 1 O , 054 12.16 17th , 84 2 , 94 0.38 E7891 2 Composition of the various 0 , 056 12.54 17th , 46 3 , 71 0.33 R7892 3 Alloy
type O, , 057 12.79 18th , 46 2 , 05 0.33 R7893 4th according to the
invention O. , 041 14.8 17 · , 05 1 , 87 0.33 R7821 5 according to the
invention O, , 015 15.12 17, , 37 2 , 11 0.31 R7368 6th according to the
invention O, , 110 15.04 17, , 99 1, , 38 0.32 R7822 7th according to the
invention O, , 043 14.52 17, M. 1, , 98 0.30 R7740 8th according to the
invention O, 045 7.96 18 »18th 1, »94 0.33 0.21V
0.14 cb R7601 9 according to the
invention O, 052 5.64 25, 07 2, , 29 0.29 R7604 10 according to the
invention O, 06 14.54 25, 31 2, 23 0.29 R7768 11 according to the
invention O, 12th 14.52 12, 30th 1, 71 0.32 R7769 12th according to the
invention 10 11.80 86 0.32 R7804 13th low
Mn content 0.30 14th low
Mn content high
Cr content high
Cr content low
Cr content

109 8 19/1220

sample Alloy
type σ Mn Cr Ni N melt 15th 304-N
(AISI) 0.052 1.74 18.29 9.6 0.16 E7800 16 304-N 0.06 1.66 18.63 10.7 0.12 R7801 17th 304-N 0.060 1.48 18.70 8.36 0.25 E7802 18th 304-N 0.052 1.69 1ö, 94 9.59 0.22 R78O3 19th USSteel
cryogenic
Tenelon 0.066 16.08 18.11 5.81 0.30 R7823 20th 304 0.05 ^ 0.77 18.19 8.81 0.031 17105 21st 316 0.064 1.80 17.58 13.38 0.025 2.66 Mo 382497 22nd 21-6-9 0.045 8.95 20.46 6.67 0.29 55711

In samples 1 to 14, the phosphorus content was 0.007 to 0.027%, the sulfur content 0.010 to 0.029% and the silicon content 0.21 to 0.54%.

109819/1225

egg Tabel Stretch
firm
at
Room temperature
temperature
(0.2 %
Bend)
MN / m II from Table I. 28 Magne
tables
Conversion
lung
(78-K) Alloy
type .properties of 442 Steels Blow
firm
at the
Charpy -
Impact
% -ual attempt
One on one
; Schnü-V-shaped
α tion notched
(Room test item
tempe- in joules
temperature) (78 ⁰ K) 23 small amount sample according to the
invention Zugfe
stig
speed
at
Space-
tempe-
rature
in ο
(MN / m 510 % -ual
strain
at 5 egg
(Space
tempe
rature) 70 49 very
small amount 1 according to the
invention 755 455 54 70 58 small amount 2 according to the
invention 828 435 52 71 72 small amount 3 according to the
invention 755 428 49 70 54 small amount 4th according to the
invention 755 407 51 70 46 very
small amount 5 according to the
invention 755 372 49 70 53 small amount 6th according to the
invention 745 420 54 70 27 very
small amount 7th according to the
invention 718 538 50 70 8th very
small amount 8th according to the
invention 765 455 54 62 7th conversion
at space
temperature 9 lower
Mn content 828 448 42 67 conversion
at space
temperature 10 lower
Mn content 795 53 51 11 870 52

109819/1220

-SO-

Impact resistance "at

sample Alloy
type Zugfe
stig
speed
at
space
tempe
rature
in ρ
(ΜΝ / πι Stretch
firm
at
Room temperature
temperature
(0.2%
Bend)
MN / m Charpy
Impact
% -ual attempt
% -u.ale one on one
Stretching in a V-shape
notched at 5 cm
(Room (room test object
tempe- tempe- in joules
rature) rature) (78 ⁰ E) 68 5 Magne
tables
Conversion
lung
(78 ^§ K) 12th higher
Cr content 765 510 39 63 8th 35 %
ferrite 13th higher
Cr content 785 538 40 68 12th 20 %
ferrite 14th lower
Cr content 820 455 51 70 106 small amount 15th 304-N
(AISI) 640 318 53 71 138 conversion 16 304-N 613 270 54 70 87 conversion 17th 304-N 725 372 51 70 137 conversion 18th 304-N 695 338 48 . 69 54- conversion 19th USSteel
cryogenic
Tenelon 780 420 49 69 149 20th 304 593 '314 59 69 135 conversion 21st 316 613 310 51 70 102 small amount 22nd 21-6-9 710 400 50 very
small amount

The impact strength values at room temperature exceeded all samples 135 joules.

109819/12 20

The stainless steels previously used to manufacture cold-drawn wires with high tensile strength are AISI types 301 and 302 as well as US Steel TEKELON. The steel according to the invention was found to be high strength; it can be drawn with a final pass of slightly greater than an AO% reduction up to a tensile strength of 1515 to 1725 MN / m ² and a yield strength (0.2 % bending) of at least 1240 MH / m. The cold hardening capacity of the alloys according to the invention is considerably greater than that of the three known alloys mentioned. With regard to Ä

of the other physical properties, the steels according to the invention can easily be compare with the three steels mentioned. The higher cold hardenability of the steels according to the invention enables a steel to be processed in a single pass at around 45% cold reduction, up to to draw the basic thickness, whereas the Type 302 requires an overall cold reduction in the order of 60% in order to achieve a tensile strength of 1515 MN / m can be reached.

A melt of the composition: 18.6 % chromium,

11.9 % manganese, 1.6% nickel, 0.11 % carbon, "

0.38% nitrogen, 0.015% phosphorus, 0.010% sulfur, 0.60% silicon, balance essentially iron _t was examined for its mechanical Kaitzieheigenschaften. The at room temperature (received) results are shown in the following Table III, they were with a nichtp; quenched Erich ended wire of an initial size of 6.35 mm Rundsfcab, the annealed half an hour long at 1340 ⁰ K and then MIB V / ater

been

0981 9 / 122CT

was received. The tempering hardness was Rockwell B.98.

Table III

% -ual
Cold processing
reduction Zugfe
sturdiness
in MN / m Stretch
sturdiness
(0.2 %
Bending angle
in MM / m % -ual
strain
at 5 cm % -ual
A
lacing Rockwell
Hardness C 10 1020 760 40 63. ■ ;. ,, .... 24 20th 1170 953 25th 58 ^{; i} 28 30th 1-310 1090 17th 53. 32 40 1480 1240 12 · . ^ 8. ·. ,, .- - 37 50 1640 1400 10 ■ 43 40 60 1830 1640 10 40 44

109819/1220

-Her 6.55mm round bar, which was assumed to be was made from a four-inch square Ingots produced. The 10.2 cm square

2 bars had a tensile strength of 800 MN / m, a tensile strength (0.2% bending) of 448 MN / m, a percentage elongation "at 5 cm of 53? a percentage Neck of 73j 5 "and a Rockwell hardness B of 96.

The 10.2 cm round billet possessed after appropriate tempering and after quenching

2 water has a tensile strength of 825 MN / m, one,

Yield strength (0.2 % bending) of 442 MN / m ² , *

a percentage elongation at 5 cm of 63 »a percentage constriction of 69 and a Rockwell hardness B of 98.

A 6.35 mm bar hot rolled from a 4 inch rectangular billet (Tierkantbarbar)

ό a tensile strength of 1140 MN / m, a yield strength

strength (0.2% bending) of 895 MN / m, a percentage elongation at 5 cm of 38, a percentage Constriction of 60 and a Rockwell hardness C of 36.

A steel winding according to the invention was processed into a 2.5 mm rod raw annealed at 131O ⁰ C, and stained with a speed of 30.5 meters per minute at a Plachenverminderung of 43% in a single pass a 1.9 mm Round bar processed. The tensile strength obtained is

carried 1515 MN / m. In comparison, when trying from a steel of the AISI type 302 a wire pulling the same thickness, an overall reduction

from

109819/1220

of 58% required to achieve a tensile strength of

ρ
1515 ΛΠί / m to reach. This required two passes, the first at a speed of 30.5 meters per minute and the second at a speed of 18.3 meters per minute to avoid scratching the wire.

The steel according to the invention can be melted in an electric furnace, either under Provide access to air or in a vacuum. He can be remunerated further, "for example by degassing in a vacuum and cast into ingots or continuously cast into slabs. On that the steel according to the invention usually becomes plates, sheets, strips, rods, rods or wire, e.g. spring wire or welding wire, hot and cold formed. In some! Cases the steel is used in the cast or forged state or processed into molded bodies, which are then welded.

109819/1220

Claims (10)

11 :; . ■■■: ■ '■■■. ■■ »■" ■ »Κ .I :. \ ψν-! '' 1HS! Patent claims 1. Austenitic, stainless steel with high strength at room temperature, high cold hardening ability, good welding properties as well as good stability and toughness at cryogenic temperatures, consisting of 15 »5 to 20 % chromium, 11 to 15% manganese, 1.1 to 4 % Nickel, less than about 0.01 to 0.11% carbon, 0.28 to 0.38% nitrogen, balance Iron together with Yerunrei- | inclinations. 2. The austenitic stainless steel of claim 1 consisting of 15.5 to 20 % chromium, 11 to 15% manganese, 1.1 to 4 % nickel, less than about 0.01 to 0.11 % carbon, 0.28 up to 0.38% nitrogen, up to 0.040 % phosphorus, up to 0.030 % sulfur, up to 1.0% silicon, the remainder iron and impurities caused by the melting process. 3. Austenitic stainless steel according to claim 1, λ consisting of 17 to 19 % chromium, 11 to 13.5% manganese, 1.1 to 3.5% nickel, 0.03 to 0.10% carbon, 0.30 up to 0.34% nitrogen, up to 0.040 % phosphorus, up to 0.030% sulfur, up to 1.0 % silicon, the remainder iron and impurities caused by the melting process. 4. Austenitic stainless steel according to claim 1, characterized in that it has a manganese content from 11 to 13.5%. 109810/1220 5. Austenitic stainless steel according to claim 1, characterized in that it has a nickel content of 1.1 to 3.5 % . 6. Austenitic stainless steel according to claim 1, characterized in that it has a carbon content from 0.03 to 0.10% and a nitrogen content from 0.30 to 0.34%. 7. Austenitic stainless steel according to claim 1, characterized in that it has a chromium content from 17 to 19%. 8. Austenitic stainless steel according to claim 1, characterized in that it contains 0.1 to 0.5% an element consisting of vanadium and / or mob. 9. Austenitic, stainless steel according to claim 1, characterized in that up to about 3 »5% Chromium are replaced by molybdenum in a ratio of 1: 1. 10. Austenitic, stainless steel according to claim 1, characterized in that it is up to 0.010% Contains boron. 109819/1220