DE1957421A1 - Corrosion-resistant stainless steel alloy - Google Patents

Description

Dr. F. To the stone εοη. - Dr. E. A ^ srrrarn *

Dr. R. Koenlgsberger - Dlpl.-Phys. R. Holzbauer - Dr. F. Zumsteln jun,

Patent attorneys;

TKtEFON: βΑΜΜΕΙ.-NO. aaeam 'BMONOHENP, TELEX S2OB7O BRAUHAU38TRA8S! I - »/ III

TELEGRAMS: ZUMPAT POeTOOHECK ACCOUNT; MONOHY BITE

BANK ACCOUNT: BAf) KHAUa H. AUFHXUSER

52 / zö

Case O.L.P. 784 E.

Carpenter Technology Corporation, 101 Y / est Bern Street, Reading, Pennsylvania 19603, U.S.A.

Corrosion-resistant stainless steel alloy,

The present invention relates to a stainless steel alloy, especially a stainless steel with a unique combination of high strength and corrosion resistance, which is still relatively inexpensive.

There are many instances in the chemical and petroleum industries where the combination of strength and corrosion resistance required cannot be met by currently available alloys without resorting to alloys which are so expensive and prohibitive to use. As far as is known, a useful combination of high strength with good corrosion resistance to oxidizing and reducing acidic media is currently only available in alloys such as AISI Type 660, which are very expensive compared to the 300 and 400 series alloys. Of the cheaper alloys, the AISI 410 type can have a yield strength of at least 0.2% of about 7030 kg / cm (100,000 pai), but has practically no resistance to attack by acids. Although only a little more expensive than type 410, AISI type 304 has excellent resistance to oxidizing acids such as nitric acid, imglüekliehorveiae makes it, however, a ^{0.2 ^ yield point below 3520 kg / cm 2} (bO 000 pol) completely un-

009835/1271 Bad or / q, _Nal

-z-

Suitable for uses where high strength and corrosion resistance are required. Even though AISI Type 316 is significantly more expensive than Type 304 (about $ 20 or more), it does not have any greater strength, but it can withstand attack by a reducing acidic medium such as sulfuric acid. In view of the above, a stainless steel alloy is provided hereby that a 0.2 $ in the tempered state - has yield strength of about 6680 kg / cm (95 000 psi) or more at room temperature. The present alloy loses no more than 0.254 cm per year (100 mils), and preferably no more than 0.127 cm per year (50 mils) in boiling 65 wt.% Nitric acid, loses virtually no * metal in 5 wt Sulfuric acid at maximum temperature, has good resistance to 5% strength by weight sulfuric acid at 50 ⁰ C and has good resistance to embrittlement by fiber material »

As a precautionary measure, if the alloy has never cooled down from its tempering temperature, the g ^. Ims elite strength and corrosion resistance and is also sufficiently pliable and ductile that it can be easily shaped and machined.

It has been found that the composition with which the above-mentioned results can be achieved, according to metallurgical practice, is composed as follows in weight-yes, but only if it is balanced that a substantial cardaneity microstructure, which is no longer contains 1 to 2 fs delta ferrite, creates:

Carbon manganese

Silicon phosphorus sulfur chromium

area Preferred
area BADOBIGlNAt 0.2 max. 0.1 max. 2 max. 0.75 max. 2.5 max. 0.5 max. 0.05 max. 0.0? Max. 0.05 max. 0.03 max « 3.5-17 14.75-16.25 35/1271 ■ ·

Area Preferred area

Nickel '4-9 5-7

MolybdKn ** 0.5-3 0.75-2

Copper 0.75-3 1-2

Niobium up to 1OxC up to 1OxC

Titanium up to 5xC up to 5xC cobalt 6 max.
Boron 0.01 max.

*) = For good machinability, it may contain 3 _f 5 $> manganese and / or 0.5 # sulfur. For this purpose, some or all of the sulfur can be replaced with selenium on a 1: 1 basis.

**) = Or an equivalent amount of tungsten.

The remainder of the present composition is preferably essentially iron, excluding impurities associated with good engineering metallurgical processing. For example, when the present alloy is made using an electric arc furnace, lyso-oxidizing agents can be used in place of manganese and silicon such as aluminum, zirconium, magnesium, or the rare earths, with the result that a small amount of about 0.01 $> to 1 # one or more of these elements can be present as an associated impurity. Nitrogen can normally be present as an impurity, but since it is a strong auatenite former (about 30 times as effective as an equal weight £ amount of nickel) and also because of its hardening effect, it is preferably not added and should not be added in an amount greater than this be present as $ 0.1. Other elements can be present in the present composition which do not affect its desired properties.

If a stainless steel alloy is produced with the composition range given above, it does not lose less than 65% in boiling nitric acid

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BATH

0.254 cm (100 nils) of metal per year and is externally resistant to embrittlement from hydrogen. It also loses praktiech no metal in 5 wt .- ^ sulfuric acid at room temperature and has a good resistance to 5 Gew.obiger sulfuric acid at 50 ⁰ C.

Will be a stainless steel alloy with the above preferred range, it does not lose more than X in 65 units of boiling nitric acid, 127 cm (50 mils) metal per year.

The elements chromium, nickel, molybdenum (or an equivalent amount of tungsten) and copper are the only indispensable alloying elements in the present steel. When carefully balanced within the stated ranges so as to provide substantial Marteoeit microstructure, they will provide the corrosion resistance characteristics of the present alloy and the martensite reaction will provide the strength. Therefore, when balancing the alloy, the effect of all the elements present on the microstructure is taken into account, whether or not they were intentionally added. Residual austenite, which is usually the corrosion resistance is not detrimental, should not be present preferably in an amount greater than about 10 i "to 15%, since the martensite reaction is consistently not able ale with more 10 £ residual to 15 $ austenite to deliver the desired strength. On the other hand, the presence of small amounts of delta ferrite does not adversely affect the strength of the present alloy, but more than 1 to 2 % results in a significant loss in acid resistance. Delta ferrite should therefore be kept to a minimum and no more than 1 to 2 i "should be present in this alloy. For best results the alloy should be completely free of delta ferrite.

Like nitrogen, carbon is a strong austenite former and if not stabilized, preferably by an appropriate amount of niobium or titanium, it should be as effective as 30 times

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how nickel are taken into account. Carbon is usually not intentionally added to the present composition, however, it is considered tolerable in amounts up to a maximum of about 0.2 #.

Preferably, carbon is maintained at no more than about 0.1 9δ, if it is present in an amount of more than about 0.03 #, it should in wt. $> About five times of the ~ about ten times its weight of Job or from the be accompanied by its weight in litan. Niobium and titanium have a stabilizing effect on the carbon in the specified proportions, so that it is no longer effective under austenite formation. Other carbon stabilizers that can be used include zircon, vanadium and tantalum in a total of up to 1 # either individually or together, being used in 5 to 10 times the amount of carbon. If the carbon is not stabilized, when balancing the present composition, its weight percentage should be multiplied by 30 when calculating the nickel equivalent. Also, if the carbon present in the present composition is not stabilized, it tends to harden the martensite formed when the alloy is quenched from its tempering temperature. This hardening can to a certain extent reduce the weakening effect

- 15 W.

balance that will accompany the preservation of more than $ 10 / austenite can, but the hardening effect is not desirable if it interferes with the fabrication of the alloy. When this hardening effect is not regarded as a hindrance and the proportions of the remaining elements are such that the carbon need not be stabilized in order to maintain the martensite equilibrium To ensure the present alloy, the addition of a "carbon stabilizer" can be dispensed with.

Neither manganese nor silicon is a desirable alloy additive in the present alloy, although manganese can be tolerated up to a maximum of about 2% , and where good machining properties (good machinability) compared to a certain

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sen loss of corrosion resistance to oxidizing acids are preferred, the manganese content can be increased to about 3.5 fo. Manganese is about half as effective as nickel as an austenite former. When calculating the nickel equivalent, the manganese content should therefore be multiplied by 0.5. Silicon does not appear to add or detract from the chemical and physical properties of the present alloy, with the understanding that it may add to the ability of the present alloy to do so. Resist oxidation. However, so long as it does not adversely affect the martensite balance of the present alloy, silicon can be present in an amount in the range of I) Ie to a maximum of about 2.5 % . As a ferrite parent, silicon is 1.5 times more effective than chromium. When calculating the chromium equivalent content of the present alloy, the silicon content in wt .- ^ should be multiplied by 1.5.

Phosphorus and sulfur are, respectively to a maximum of no more than about 0.05%, preferably 0.03 confined i> with the exception that when good Zerspannungseigenachaften are desired (good machinability) and 1st tolerable concomitant reduction in corrosion resistance, then 0.5 l * sulfur can be added. Anate portions of all or P of a portion of the sulfur can also be used selenium to obtain the desired good tensile properties .

In order to impart rustproof properties and meet the other requirement that the maximum loss is less than 0.254 cm (100 mils) per year in an oxidizing acid such as nitric acid, there must be at least about 13.5 # of chromium in the present alloy . Chromium is a ferrite-forming element; the maximum amount of chromium that can be tolerated in the present composition is therefore determined by this effect and is approximately 17 r>. Because of its effect on the resistance of the composition to oxidizing acids, preferably at least about 14.75 # chromium is incorporated here, so that a maximum metal loss in a boiling 65 wt .- ^ i-

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BATH ORIGINAL

nitric acid of less than 0.127 cn (50 mils) per year is guaranteed, better still, with a minimum of 15 $> Chromium, the maximum rate at which metal of the present composition is lost in boiling nitric acid is less than 0.076 cm (30 mils) per year. Because of the ferrite-forming effect of chromium, it is preferred here to limit the maximum amount of chromium to no more than about 16.25 #, as will be explained in more detail below, but care must be taken with the nickel and chromium content in each case that the Marteneit equilibrium weight of the alloy is maintained.

Nickel is essential for the corrosion resistance of the present Zueammensetaung, and for this purpose a minimum of 4 i> Nickel 1st required. Nickel also has a balancing effect on the microstructure and acts as a builder of auetenite. For this purpose, 4 bi · 9% and preferably 5 to 7 incorporated in 1 »Nlokel the present composition. In balancing the alloy, the greater Kengen accompany nickel or nickel equivalent smaller amounts of chromium or chromium equivalent so that the presence of more than 10 i "residual austenite is avoided. While the corrosion resistance effect of nickel in the present composition, imparted by the required minimum of 4 #, finds no equivalent in other elements, other austenite-forming elements can be used in place of nickel in greater than about 4 #, so long as the properties desired not be affected. Manganese is therefore not a desirable substitute, but cobalt is a substitute as will be fully described.

Like chromium, molybdenum is a ferrite-forming element and its effect is such that "when calculating the chromium equivalent content of the present composition 1 i> molybdenum such as 1 i ° chromium should be taken into account. Molybdenum contributes to the corrosion resistance of the present alloy and is a guarantee the desired resistance to a reducing acid medium such as sulfuric acid is extremely important ..

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BATH

For this purpose, a minimum of about 0.5 % molybdenum is required. Molybdenum is also effective against water embrittlement, in particular when products formed from the present alloy have to be exposed to a hydrogenous medium in an aged state. Molybdenum-rich delta ferrite even seems to be more easily attacked than chromium-rich delta ferrite, so care must be taken that, for a given equilibrium, there is not so much molybdenum present that it causes the formation of ferrite. Therefore , in the present composition, molybdenum is limited to 5 $> . PUr best results are preferably used 0.75 to 2 i 'molybdenum.

Molybdenum and tungsten can be used as substitutes for each other in the present alloy. In order to replace molybdenum with an equivalent effect, tungsten in a proportion of about 1.2 # to 1.6 » tungsten for 1 » molybdenum can replace all or part of the molybdenum content of the present alloy. It is therefore self-evident that when reference is made to molybdenum in the present application, it is intended to mean that molybdenum and tungsten are to be included either together or individually, with tungsten also being able to replace all or part of the molybdenum in the specified ratio.

Copper and molybdenum (or the equivalent amount of tungsten) work together in the present composition to provide increased resistance to sulfuric acid. For example, it has been found that $ 1.5> copper with $ 0.75 molybdenum provides an effect equal to or greater than either 3 # copper or 3 1 ° molybdenum in the absence of the other. Copper also helps to provide the necessary corrosion resistance, especially resistance to attack by reducing acidic media such as sulfuric acid. Copper also provides a hardening effect if the alloy is too soft in the quenched and tempered state or greater strength is required. When present in amounts below about 0.75 #, copper is ineffective and the corrosion resistance of the present alloy cannot be achieved. More than about 3 fo copper

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- Q -

Additives can have a detrimental effect on the alloy. Preferably copper is limited to about 2 » . As an austenite former, copper is half as effective as nickel, so the percentage by weight of copper is multiplied by 0.5 when calculating the nickel equivalent content of the alloy in question.

As can be seen, cobalt can replace some, but not all, of the nickel content of the present alloy. Up to about 6 # cobalt can be used in the ratio of 3 % cobalt for every 1 i * nickel of the nickel present in greater than 4% in the present alloy. Cobalt is about 1/3 as effective as nickel as an austenite former in the present alloy and thus provides a way to increase the alloy content without upsetting the composition. When cobalt is present in the present composition, only 1/3 of its weight percentage is used in calculating the nickel equivalent content of the present composition.

Because of the effect it has on the properties in the present case Alloy at elevated temperature, up to about 0.01 # boron can be incorporated into the present alloy, however, if the best corrosion resistance to acidic medium, such as nitric acid, which attacks the grain boundaries, is desired boron should not be added on purpose.

In summary, it should be noted that nickel, copper, carbon, Nitrogen and manganese act as austenite formers. you relative effect is roughly represented as:

Eq. Β #Ni + #Cu +% Mn

But carbon that has been paralyzed by a stabilizer is not counted as an austenite former. The elements chrome, Molybdenum and silicon tend to contain delta ferrite in the present

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195742t

• 6

form the following composition eu. Their relative effect is roughly represented as:

Eq. S

The elements that make up ferrite also tend to be austenite too stabilize. For a given amount of nickel equivalent, the amount of remaining austenite can be calculated with increasing chromium equivalent content increase in the alloy.

It can be seen from the foregoing that the minimum nickel equivalent content possible in the present composition is about 4> 37 i> and the possible minimum chromium equivalent content is about 14 i> . This relationship makes for a complete martensite microstructure. As a guideline for balancing the present alloy, it may be mentioned that at a nickel equivalent content of 4 | 37 i> the available data show that up to about 16 $> chromium equivalent can be present without leading to more than 1 to 2 i » delta ferrite . If the chromium equivalent content in the present alloy is increased from about 16 # to about 18.5 #, then the nickel equivalent content should be increased from 4.37 ° to about 8.6. As such, while the relationship may not be linear, it is appropriate to use it as a guide in balancing the alloy. It should also be noted that the nickel equivalent content of the present alloy may contain up to about 10 $> or one or two tenths of a percent constitute less in chromium equivalent content of 14 i>. If the chromium equivalent content of 14 i "increased to about 18.5 ^ 5, the nickel equivalent content must be more fo reduced from about $ 10 for something than 1 to about 8.6 £. This is also not a strictly linear relationship, but it is useful to treat it as such as a guideline for balancing the alloy in order to avoid the presence of more than about 10 ° retained austenite.

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The present alloy is easy to manufacture and process according to standard technical methods. The heat treatment is not critical and it can be compensated for by heating for about 1/2 to 1 hour at about 927 to 115O ⁰ C (1700 to 210O ⁰ P) '. Preferably is annealed at about 982-1066 ⁰ C (1800 to 195o ⁰ P). If a strength greater than at least about a 0.2 ^ yield strength of 7030 kg / cm (100,000 psi) is required, the present alloy can be produced by heating the present alloy to about 427 to 538 ^° C. (800 to 100O ⁰ P).

The following examples of the present alloy were melted and poured into test bars which were forged, tempered and formed into test bars. Unless otherwise specified, for half an hour be "i 982 ⁰ C (1800 ⁰ P) treated and then quenched in water. The Probestükke i \ ir the tensile strength at room temperature have a calibrated diameter of 0.640 cm (0.252 inch) a calibrated length of 2.54 cm (1 inch) The corrosion resistance samples were 1.81 cm by 1.27 cm by 3.175 mm (1 1/2 1/2 χ 1/8 inch) and were carefully weighed to 0.0001 g before and after exposure to the test medium and the rate of corrosion in centimeters per year was calculated 0.635 cm (0.25 ") diameter and 0.318 cm (0.125") calibrated diameter In all examples the phosphorus and sulfur content was less than 0.01 Ji.

example 1

As a specific example of the present composition a batch was melted and an ingot was cast containing? 5 by weight:

Carbon 0.010

Manganese 0.38

Silicon 0.32

Chromium 14.83

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Nickel '5.77

Molybdenum "1.49

Copper 0.75

Nitrogen 0.023

Iron remainder except accompanying damage

cleanings

In the quenched and tempered condition, the alloy had a Rockwell hardness of C 31 and a room temperature tensile strength of about 7975 kg / cm ² (113,500 psi) for the 0.2? U yield point, a specific tensile strength of about 10 050 kg / cm ² (14th century) -3,000 psi) with an elongation of about 16.5 # and a reduction in cross-sectional area of about 63 #. To test their resistance to hydrogen embrittlement, two samples were subjected to a tension of 5620 kg / cm (80,000 psi) in a 5 wt% acetic acid solution saturated with hydrogen sulfide at room temperature. After 263 hours, neither sample had failed and the test was no longer continued. Two other samples were tested in the same hydrogen-containing medium after they had been annealed and were then aged for 4 hours at 454 ⁰ C (850 ⁰ P) and cooled in air. After 289 hours under a tension of 5620 kg / cm (80,000 psi), neither sample had failed and the test was terminated. After testing them in boiling 65 wt% nitric acid for five periods of 48 hours each, the average rate at which the metal was lost was calculated and found to be about 0.84 mm to 0.86 mm (33 to 34 mils) per year. Test pieces were also immersed in test solutions of 5% strength by weight sulfuric acid at room temperature; no metal was lost. X-ray diffraction analysis of the microstructure of the alloy showed no retained austenite and the alloy had no delta ferrite.

Example 2

As another specific example of the present alloy, a batch was melted and an ingot was cast, which in

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Weight-jC contained: Carbon 0.016

Manganese O ₁ 30

Silicon 0.26

Chrome 15.58

Nickel x 5.94

Copper 1.42

Molybdenum. 0.80

Sioto 0.16

Nitrogen 0.024 Iron. Leftovers other than accompanying damage

cleanings

In the quenched and tempered state , the alloy had a Rockwell hardness of 0 29 and a room temperature tensile strength of about 7975 kg / cm (113 500 psi) at the 0.2 96 yield point, a specific tensile strength of about 10435 kg / cm (148 500 psi) psi) with an elongation of about 16.5 # and a reduction in cross-sectional area of about 67 #. Test pieces of this alloy were immersed in 65 wt ) found per year. Four test pieces of this alloy were immersed in 5 wt .- #: sulfuric acid at 50 ⁰ C was dipped and subjected to these conditions for 3 periods of each 48 hours. The rate at which the metal is lost was then calculated and found to average 0.218 cm (86 mils) per year for two test pieces and 0.282 cm and 0.295 cm (111 and 116 mils) per year for two other test pieces. In 5% by weight sulfuric acid at room temperature, the test pieces did not lose any metal. As a test for hydrogen embrittlement, test pieces were subjected to a tension of 5620 kg / cm ² (80,000 psi) in 5 wt% acetic acid which had been saturated with hydrogen sulfide at room temperature. After 260 hours the samples did not fail, indicating that the alloy was not sensitive to hydrogen embrittlement, so the test was

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completed. X-ray diffraction analysis of the microstructure of the alloy in the quenched and tempered state showed that it contained about 3 % auetenite.

Example 3

As a further ospecific example of the present composition a batch was melted and an ingot cast containing ^ by weight;

Carbon 0.062

Manganese 0.33

Chrome 15.60

Nickel '5.87

Copper 1.40

Molybdenum 0.80

Job 0.53

Iron remainder except accompanying damage

cleanings

In this example, the elements silicon and nitrogen were represented almost equally as in the example

In the quenched and tempered condition, this alloy had a Rockwell hardness of C 32, a 0.256 yield strength of about 8475 kg / cm (120,500 psi) and a specific tensile strength of about 10,675 kg / cm (152,500 psi) with a Elongation of about 18.5 fi and a cross-sectional area reduction of about 65.5 %. Test pieces of this alloy were immersed in test solutions of 65% strength by weight boiling nitric acid. After five periods of 48 hours each, the average rate at which the metal is lost was calculated and found to be 0.61 mm (24 mils) per year. Test pieces of this alloy were immersed in 5 G ew .- ^ sulfuric acid at a temperature of 50 ⁰ C. After three periods of 48 hours each, the average rate at which the metal is lost was calculated and found to be 2.5 10 ™ 'mm (0.1 mils) per year. They are subjected to a tension of 5620 kg / cm ² (80,000 psi) in 5 wt

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Acetic acid, which is saturated with hydrogen sulfide at room temperature is, bo did not fail after 260 hours, indicating that the alloy was resistant to hydrogen embrittlement Was not sensitive, the test was terminated. The microstructure was subjected to an X-ray diffraction analysis, it was found to have retained 8 # austenite.

Vague their excellent resistance to attack by acids, such as boiling, 65 wt .-% nitric acid and 5 wt .-% sulfuric acid at room temperature and also at a temperature up to 50 ⁰ C or higher, combined with high strength and without any The present alloy is particularly suitable for the manufacture of parts that are to be used in the chemical and petroleum industries.

Also because of the unique combination of corrosion resistance and strength, and in view of its relatively low price, the alloy of the present invention is particularly good for uses such as pump rods, valve rods and housings, pipelines, closure devices, and manufacturing honeycomb structural elements suitable for the aircraft industry.

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In addition, the alloy according to the invention can also be used as follows • ugammengeeetet eelns

up to Weight -j> a) carbon up to 0.02-0.2 0.35-3.5 · ■ "· ■ ©" * "■
silicon 0.25 - 2.5 phosphorus 0.005-0.05 selenium • 0.05-0.5 sulfur 0.05-0.5 chrome 13.5 - 17 Niokel 4 - 9 molybdenum 0.5 - 3 copper 0.75 - 3 niobium 10x # C titanium 5x £ C cobalt 0.6-6 boron 0.001-0.01 Zircon ") Vanadium V 0.001-0.01 Tantalum) up to b) carbon up to 0.002-0.2 amounts 0.035-3.5 silicon 0.025-2.5 phosphorus 0.001-0.05 selenium 0.005-0.5 sulfur 0.005-0.5 chrome 13.5 - 17 nickel 4-9 molybdenum 0.5 - 3 copper 0.75 - 3 niobium 1OxJiC titanium 5x # C cobalt 0.06 - 6 boron 0.001-0.01 Zircon ") Vanadium r 0.01-1 Tantalum J 009835/1271

Weight »^

c) Carbon ° » ⁰¹ * ° ' ¹

Mangen ° ' ⁰⁷⁵ ~ °' ⁷⁵

SiliEiua 0.05-0.5

Phosphorus ° ' ⁰ ° 5 - °' ⁰⁵

Soh sulfur 0.005-0.03

ChroB H.75 - 16.25

⁵ " ⁷

Hiokel

KolyMän 0.75-2

¹ " ²

lupfer

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Claims (2)

Claims 1. Corrosion-resistant stainless steel alloy which is tempered and tempered and the quenched condition has a 0.2 ^ yield strength at room temperature of at least 6680 kg / cm (95,000 psi) and has good resistance to corrosion in nitric acid and sulfuric acid and to hydrogen embrittlement, characterized in that it consists essentially in wt .- ^ the end: Carbon manganese silicon phosphorus sulfur selenium chrome Nickel Molybdenum Copper Hlob titanium Cobalt boron Zircon ") Vanadium > Tantalum J and the remainder are essentially iron and impurities in which tungsten in the ratio of 1.2 to 1.6 # tungsten to 1 $> molybdenum is the equivalent of molybdenum and can replace all or part of the molybdenum, and the Elements are balanced in such a way that the alloy in the tempered and quenched state has essentially a martensite microstructure which no longer contains 1 to 2 # of delta ferrite. 0.2 "maximum Il 5.5 Il 2.5. It 0.05 Il 0.5 Il 0.5 1 5.5-17 4-9 0.5-5 0.75-5 up to 1 0x # C up to 5x # C 6 maximum 0.01 - 1 up to 009835/1271 2. Alloy according to claim 1, characterized in that it contains up to 2 fo manganese and up to 0.05 # sulfur, and this alloy in 65 wt .- ^ iger, boiling nitric acid no more than about 0.254 cm (100 mils) per year lose metal and is very resistant to hydrogen embrittlement, virtually no metal dissolved in 5 wt .- ^ sulfuric acid loses at room temperature and good resistance to 5-wt .- # sulfuric acid at 50 ⁰ C possesses. 3. The alloy of claim 1, characterized in that they are no longer lost in 65 parts by weight Jtiger, boiling nitric acid than about 0.127 cm (50 mils) per year of metal and consists essentially of: carbon 1 essentially iron and 0.1 maximum - Mftnr * n 0.75 η silicon 0.5 It phosphorus 0.03 n sulfur 0.03 Il chrome 4.75 - 16.25 nickel 5-7 molybdenum 0.75 - 2 copper 1 - 2 and the rest Accompanying impurities is. A alloy according to any of the preceding claims, characterized in that it is balanced such that it in the tempered and quenched condition no more than about 10 ^c _t O containing retained austenite. 5. Alloy according to one of the preceding claims, in which Nickel, copper, carbon, nitrogen and manganese act as austenite formers and form chromium, molybdenum and silicon delta ferrite and stabilize austenite, characterized in that the minimum nickel equivalent in the alloy composition is 4.37 / j is and is defined as: 009835/1271 bad original Eq. = FSNi + 2
the minimum chrome equivalent is 14 # and is defined as: Eq. = #Cr + g Mo 6. An alloy according to claim 1, characterized in that it consists essentially in Qew.-Jt is composed of: 0.02 - 0.2 3 0.35 - 3.5 - 3 0.25 - 2.5 0.005 - 0.05 0.05 - 0.5 6th 0.05 - 0.5 - 0.01 13.5 - 17th 4 - 9 0.5 - 0.75 up to 1OxJiO see below 5xJ * C 0.6 - 0.001 0.1 - 1 7. Alloy according to claim 1, characterized in that it consists essentially in weight-Ji of: Carbon 0.002-0.2 Manganese 0.035-3.5 Silicon 0.025 - 2.5 Phosphorus 0.001-0.05 009835/1271 selenium up to 0.005 - 0.5 6th sulfur up to 0.005 - 0.5 chrome • 13.5 - 17th nickel 4th - 9 1 molybdenum 0.5 - 3 copper 0.75 - 3 niobium 10x # C !Titanium 5x # C cobalt 0.06 - boron 0.01 Zircon "v Vanadium ( 0.01 - Tantalum J • 8. Alloy according to claim 3, characterized in that it essentially consists of: Wt .- ^ Carbon 0.01-0.1 Manganese 0.075-0.75 Silicon 0.05-0.5 Phosphorus 0.003-0.03 Sulfur 0.003-0.03 Chromium 14.75 - 16.25 Nickel 5-7 Molybdenum 0.75 - 2 Copper 1 - 2 and the remainder essentially represents iron and accompanying impurities. 009835/1271 Carpenter Technology Corp. 23.2.197ο 1 / Sc Claim Use of a corrosion-resistant, non-rotting steel alloy, in the tempered and quenched condition, a 0.2% yield strength at room temperature of at least 668o kg / cm ' (95,000 psi) and has good resistance to corrosion in nitric acid and sulfuric acid and against Hydrogen embrittlement possesses that it is essentially in % By weight consists of: carbon o, 2 maximum manganese 3.5 " silicon 2.5 " phosphorus o, o5 " sulfur o, 5 " selenium o, 5 " chrome 13.5-17 nickel 4-9 molybdenum o, 5-3 copper o, 75-3 niobium up to lox% C titanium up to 5x% C cobalt 6 maximum boron * jf ■.> j. " Zircon ") Vanadium L. up to 1 Tantalum J 009835/1271 and the remainder essentially iron and accompanying impurities are in which tungsten in the ratio of 1.2 to 1.6% tungsten to 1% molybdenum is the equivalent of molybdenum and all or can replace some of the molybdenum, and the elements are balanced so that the alloy in the quenched and tempered State essentially has a martensite microstructure that does not contain more than 1 to 2% delta ferrite as material for the production of objects resistant to nitric and sulfuric acid as well as hydrogen embrittlement, which " at the 0.2 limit at room temperature at least one stretching 2
has a strength of at least 65oo kg / cm. 009835/1271