DE2436487A1 - HEAT RESISTANT NICKEL-CHROMOLYBDAEN ALLOY - Google Patents

Description

Dipl.-Ing. H. Sauerland · Dr.-Ing R. König · Dipl.-lng. K. Bergen

Patent Attorneys 4ooq Düsseldorf 30 - Cecilienallee 76 Telephone 432732

July 26, 1974 29,573K

International Nickel Limited, Thames House, Millbank, London . SW »1 , Great Britain

"Heat-resistant Niokel-Chromium-Molvbden-Alloy"

The invention relates to a heat-resistant one Nickel-chromium cast alloy with excellent castability, weldability and resistance to oxidation.

Heat-resistant parts are required for numerous uses, the intricate shape of which makes use requires an alloy with excellent castability and weldability to entangle individual castings Connect shapes to each other and perform repair welding while in use. This applies, for example, to stationary parts of vehicle turbines such as blades, stiffening strips, peaks and storage chambers. These parts will usually at high cost by special casting processes or made of sheet metal, which is achieved by a heat-resistant alloy with correspondingly good castability and weldability could be avoided, the usual casting in sand molds even with thin-walled Castings and, in addition, welding are permitted.

In the case of the heat-resistant nickel alloys, however, there are extraordinary difficulties in terms of equally good castability and weldability

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ORIGINAL INSPECTED

availability. For example, it is known that weldable, heat-resistant nickel alloys with a high chromium content have poor castability and consequently lead to wrinkles, cold welds and faulty casting in particular incline when pouring thin cross-sections.

All attempts to improve the casting behavior have so far been at the expense of weldability. For example found that the castability of stainless steels is improved by silicon and boron leaves, but this affects the weldability so much that only soldering is possible. the inadequate weldability is by no means surprising, since silicon and boron are among those elements that affect the weldability of chromium-containing nickel alloys most of all.

The invention is now based on the object of a heat-resistant Nickel-chromium cast alloy with excellent castability, weldability and resistance to oxidation to accomplish. The solution to this problem is based on the finding that even in the presence of Boron and silicon can then achieve good weldability within certain content limits if the contents of certain alloy components are matched to one another in a certain way. In detail there is the invention in a nickel-chromium-cast alloy with 0 to 1.4% carbon, 0 to 8,596 molybdenum a total content of molybdenum and six times the carbon content below 8.5%, 1.5 to 4% silicon, 0.1 to 1% boron, 16 to 30% chromium, 0 to 4.5% manganese, 0 to 50% iron and 0 to 2.2% niobium, the remainder including smelting-related impurities at least 30% nickel, in the absence of molybdenum a maximum of 0.5% boron and a maximum of 49% nickel and with a carbon content contains more than 0.05% at most 0.5% boron.

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The carbon improves the heat resistance, while the molybdenum improves the fatigue strength and ductility the alloy increases. However, both elements impair the weldability in such a way that they are affected by heat Zone weld cracks form and the alloy can no longer be described as weldable, if the total content of molybdenum and six times the carbon content exceeds 8.5%, at a total content below 8.5% the alloy is weldable, although with a total content below 4.5% It may be necessary to use special filler metals to avoid weld cracks. Is the total salary on the other hand between 5.4 and 8.5%, then welding can be carried out with a filler material of the same type. Optimum creep strength and weldability are obtained when the alloy is at least 3% i preferably contains at least 6% molybdenum.

Because of their favorable effect on castability, silicon and boron are among the decisive alloy components; they lower the melting point of the alloy and thus increase its fluidity. About that In addition, silicon and boron also cause a change in the chemical composition of the oxide film on the Bath surface and thus counteract the occurrence of casting defects such as wrinkles. In the end Silicon and boron also increase the alloy's resistance to oxidation.

In order to have good castability, the alloy must contain at least 1.5% silicon; however, the silicon content is preferably 2% or also 2.5%. Alloys with more than 4% silicon, on the other hand, are extremely brittle, so that the silicon content is preferred

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wise does not exceed 3.596.

The boron content of the alloy must be related to the carbon and molybdenum content. In the case of molybdenum-free alloys, boron contents affect below 0.196 or over 0.596 the weldability, which is why the In such cases the alloy preferably contains at most 0.496 boron. Alloys containing molybdenum with carbon content below 0.0596, on the other hand, can be welded with boron contents of 0.1 to 196. High boron levels affect on the other hand, the ductility of the alloy, which is why the boron content preferably does not exceed 0.596. With regard to for good castability, the alloy therefore preferably contains at least 0.296, advantageously at least 0.396 boron.

The nickel contributes to the oxidation resistance at high temperatures and acts through silicon, manganese and chromium caused sigma embrittlement. Alloys with too low a nickel content therefore tend to a certain brittleness in the as-cast state and are also subject to severe cracking in the heat-affected Zone. For this reason, the nickel content must be at least 3096, preferably at least 3596. The upper limit of the nickel content depends on its effect on weldability. With molybdenum-free alloys must, for alloys with up to 296 molybdenum, the nickel content should not exceed 4996 », preferably not more than 4596. Alloys with over 296 molybdenum can on the other hand contain up to 6596 nickel, although the nickel content is preferably at most 5596.

Chromium plays a crucial role in terms of resistance to oxidation, which is why the alloy is used at least 1696, preferably 19 to 2496 chromium

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contains. Chromium contents that are too low impair the weldability and involve the risk of cracking in the weld metal and in the heat-affected zone. The alloy can contain up to 30% chromiumf higher chromium contents can lead to intermetallic compounds or sigma phase and thus to embrittlement of the alloy.

The alloy can contain up to 50% iron without impairing the technological properties. In this way, the alloy can be produced using inexpensive raw materials such as ferrochrome instead of electrolyte chrome. Manganese also helps improve castability and also counteracts the harmful effects of sulfur. Manganese contents above 4,596, however, impair the weldability. Alloys containing molybdenum preferably contain 0.2 to 0.8 # manganese and molybdenum-free alloys 0.5 to 396 manganese.

The alloy can also contain up to 2.296 niobium to improve its high-temperature strength. On the other hand, it seems Niobium to impair the ductility, so that in each individual case the advantages and disadvantages of adding niobium are weighed Need to become.

Contaminants include aluminum and other deoxidation residues · To degrade To rule out castability, the aluminum content should not exceed Ο.59ί. Finally, the alloy can also contain other common additives such as desulphurising agents. Phosphorus and sulfur however, they can increase hot cracks and impair weldability, which is why the alloy is at most

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Contains 0.0496 of these elements.

Preferably the alloy contains 0.005 to 0.04 # or 0.0596 carbon, 5 to 8% molybdenum, 2 to 496 silicon, 0.2 to 0.8 # manganese, 19 to 2496 chromium, up to 3096 iron and 0.1 to 0.596 boron.

Another preferred alloy, on the other hand, contains no molybdenum and 0.8 to 1.296 carbon, 2.5 to 3.596 Silicon, 0.5 to 3.096 manganese, 19 to 2396 chromium, 30 to 4796 iron, and 0.2 to 0.496 boron.

The invention is illustrated below with the aid of exemplary embodiments explained in more detail.

example 1

Ten alloys 1 to 10 falling under the invention and two alloys A and B outside the invention, each with the composition shown in Table I, were melted in air in an induction furnace using a magnesium oxide crucible. After a deoxidation with aluminum 0.196, the melts at 1454 ⁰ C in green-sand molds puzzle and green sand molds were poured out for Gießkeile. ^ In this case, 1 was a form of dimensions 10 x χ 44.5 317.5 2 and a mold of dimensions 13 x 51 x 305 mm for use. The puzzle sand mold had several partially connected rectangular cavities with a depth of 5 mm and is particularly suitable for determining whether molten metal is able to flow through passages of intricate shapes with sudden, turbulence-causing changes in direction and without errors to unite with a partial flow and to fill in a multitude of corners and flat cross-sections.

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Alloys 1 to 10 had excellent castability and filled the puzzle sand mold without Wrinkles and cold welds. In contrast, the conventional alloy B casting had numerous ones Wrinkles and poorly formed corners and edges.

Table I.

Alloy C Si Mn Cr Mo Fe B Al Nb tion (Jt) (90 (Ji) (Ji) (Ji) (Ji) (Ji) (Ji) (Ji)

0.014 3.5 0.5 23.9 6.0 30.15 0.35 0.087 *

0.014 2.05 0.27 20.8 7.9 0.089 0.27 0.09

0.002 3.2 0.27 24.1 6.0 19.3 0.32

0.55 2.8 0.57 20.3 3.0 19.0 0.31 -

0.02 2.05 - 20.8 7.9 0.089 0.27 0.080 2.2

0.017 2.6 0.53 21.9 3.0 19.0 0.31

0.010 2.8 0.57 21.9 1.0 19.0 0.31

0.015 2.9 1.85 20.9 6.2 19.9 0.30 -

0.011 2.9 4.3 20.7 6.3 19.6 0.30 0.028 2.9 0.6 21.2 6.2 19.9 0.90

A 0.55 3.0 0.48 20.0 7.0 19.0 0.31

B 0.005 1.2 0.29 22.9 9.2 18.9 - 0.09

Samples of alloys 1, 2, 5 and B from molds 1 and 2 were subjected to tensile tests at room temperature and elevated temperatures. The values obtained during the tests were determined and are listed in Table II below. The data in Table II show that steels 1, 2 and 5 have excellent tensile properties both as cast and after heat treatment. The room temperature ductility is also completely sufficient for many purposes, although it is lower than in the case of

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Alloy B. The relatively low ductility of alloy 5 is presumably due to its niobium content .

State Jemp. Table II Tensile strength
speed
(N / mnr) Deh
tion
(90 A
Schnü
tion Legie
tion Cast +.
1 h / 1204 ⁰ C,
air 21 Stretch
border
(Ν / mnr) 531 18.0 26.0 1 Molding
State 21 258 591
543 15.0
11.0 ¹ 7'S
14.0 2 Molding
State 21 274
274 575
578 16.6
16.5 22.0
13.0 2 Molding
State 21 264
277 501
517 4.0
5.0 7.0
5.5 5 Cast + _
1 h / i204 ° C,
air 21 323
319 586
638 10.0
15.0 13.0
17.5 5 Molding
State 649 441
309 489 13.0 12.0 VJl Molding
State 760 221 466 19.0 15.0 VJl Molding
State 871 216 445 30.0 37.5 5 Molding
State 21 206 500
515 38.0
40.0 39.0
34.5 B. Molding
State 21 243
248 475
555 32.5
45.5 35.0
51.0 B. 250
264

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The oxidation resistance was investigated on samples of alloys 1, 2 and B as well as two commercially available alloys 310 SS and HK-40 in flowing air containing 5% by volume of steam at 538 ^° C. and a 24-hour cycle. After 500 hours the samples were cooled in air, lightly descaled and weighed. The relevant data are given in Table III below and show the excellent oxidation resistance of alloys 1 and 2 in relation to the three conventional comparison alloys.

Table III

Alloy condition w

taking (mg / cm)

1 as cast condition 7.31

8.04

2 as cast condition 8.59

9.14

+ 1 h / 1204 ^° C., air 8.72

8.71

B as cast 6.73

6.87

+ 1 h / 1204 ^° C., air 6.44

6.58

Type 310 SS hot formed .. 11.7

HK-40 as cast 9.76

In order to examine the weldability, welding tests and other welding tests were carried out according to the TIG process performed in which a prestressed

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13 mm butt weld was produced. While it is If the welding test is primarily a tactile test, butt welding is very suitable, to test the weldability of a material. In the welding tests, samples of the alloys 1 up to 7, 9 and 10 no welding cracks at ten times magnification, while those of the above voting rule for the Comparison alloy with insufficient carbon and molybdenum content A had an extremely cracked heat affected zone. Alloy 8 showed in one case a very slight crack in the heat-affected one Zone, but was also completely free of cracks. Thus, this alloy is particularly suitable as Base material. Alloys 6 and 7, their total molybdenum content and six times the carbon content was below 5.496, were just like alloy 9 with a relatively high manganese content of 4.396 severely cracked.

The butt welding tests were carried out using Filler materials according to Table IV carried out in the manner shown in Table V.

Table IV

Addition- C Si Mn Ni Cr Mo Fe B

factory- 00 (96) (90 (96) (96) (96) (96) (96) (96)

0.007 0.32 0.26 remainder 21.8 6.0 19.4 0.13

C 0.05 0.40 0.3 61.0 21.5 9.0 4.0 Nb + Ta

3.65

D 0.10 0.50 0.50 remainder 22.0 9.0 18.5 - W 0.6

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The filler material is the welding electrode known under the trademark "Inconel" 112, while the filler material D is known under the trademark "Hastelloy X" Welding electrode.

Table V alloy _; Filler material

4 D

6 D

7 D 3 3 3 11

1 1

2 D 2 C

The welded connections were visualized using eight etched cross sections and magnified ten times examined. It was found that all welded joints according to Table V were excellent and practically no cracks in the heat affected zone, although the samples of alloys 2, 4 and 7 showed a very slight crack of less than one crack per cross section. However, that comes to mind the requirements of official quality regulations are irrelevant. In addition, the tests have shown that the alloy can be welded with similar filler materials, but also with other filler metals.

The creep rupture strength of the alloys was measured at 871 ⁰ C using samples derived from cross-

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Samples of 13 mm butt welds worked out and both the weld metal with 50 to 75% as also included the heat affected zone and base material. The data of the creep tests are given in the table VI and show excellent creep behavior with healthy welded joints without changing the creep rupture strength compared to the base material.

A comparison of alloys 6 and 7 with 3% or Λ% molybdenum shows the beneficial effect of molybdenum on the fatigue strength.

additive
material Table VI 23.1
139.9
496.6 strain
{%)
25.4 mm A
Schnü
tion
(90 fracture
Job Legie
tion 3 Load standing
(N / mnr) time 56.5
692.5 30.0
20.0
7.0 52.5
51.7
2.5 Base
Base
Welding 3 11 69
55
41.5 21.0
106.0
378.3 26.0
24.0 54.3
53.0 Base
Base 3 C. 55
41.5 10.7
66.2
317.6 26.0
23.0
29.0 61.5
61.0
52.8 Basic
Basic
Basic 2 D. 69
55
41.5 52.1
154.3
456+
17.6
48 5 19.0
18.0
8.0 47.3
25.5
17.0 Base
Basic
Basic 4th D. 69
55
41.5 12.0
8.0 29.0
24.4 Basic
Basic 6th D. 69
55 21.0
18.0 37.8
40.3 Base
Base 7th 55
41.5

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Example 2

In Table VII are the compositions of another fourteen alloys 12 to 12 of the invention 25 as well as from nine comparison alloys E to M lying outside the invention, all of which in the manner mentioned in connection with Example 1 without the addition of molybdenum became. The remainder of the alloy consisted of iron in each case. Alloy 21 was made into a shape 3 of dimension 25 x 38 χ 181 mm potted to a double wedge specimen to manufacture.

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C. Si Tabel Ni VII Cr B. Al alloy (96) 00 Mn (96) (96) (96) (96) 0.95 3.17 (96) 39.7 19.5 0.27 0.055 12th 0.97 2.8 2.09 39.7 21.5 0.34 0.040 13th 0.98 3.02 2.15 38.5 20.1 0.32 0.086 14th 0.9 2.76 0.74. 40.5 20.0 0.13 0.01 15th 0.70 3.10 2.28 39.7 20.7 0.24 0.005 16 1.04 4.10 1.80 40.0 20.1 0.26 0.005 17th 0.91 2.90 1.90 38.8 20.1 0.14 0.063 18th 0.90 3.07 1.86 39.9 19.4 0.3 0.08 19th 0.80 1.99 1.48 39.9 20.4 0.14 0.04 20th 0.98 2.77 2.32 39.7 21.3 0.24 0.13 21 1.03 2.90 2.34 41.9 18.6 0.29 0.11 22nd 1.08 3.20 1.90 29.5 21.1 0.24 0.005 23 1.01 3.10 1.80 38.5 19.6 0.28 0.12 24 1.00 3.12 1.39 38.4 20.0 0.32 0.11 25th 1.50 3.10 1.00 39.7 20.7 '0.26 0.005 E. 1.08 3.00 1.90 39.7 20.6 0.27 0.005 F. 0.97 2.97 4.60 $ 0.4 20.5 0.53 0.10 G 1.05 2.90 2.36 49.0 19.8 0.26 0.005 H 1.10 2.90 2.00 38.8 15.7 0.24 0.005 I. 1.09 0.93 1.90 39.8 20.6 0.27 0.039 J 1.12 3.20 1.80 19.9 21.1 0.26 0.005 K 0.87 2.90 1.80 39.1 19.7 - 0.068 L. 0.46 1.1 1.80 20.8 27.4 - M. 1.2

The melts of alloys 12 to 25 had excellent castability; they completely filled the puzzle shapes and gave cast specimens with no wrinkles
and cold welds. In contrast, with

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a conventional alloy HU made of 0.4596 carbon, 1.6% manganese, 1.6% silicon, 20.7% chromium and 38.8% nickel, Remaining iron only cast specimens are produced which fold at the same casting temperature and when a higher one is used Casting temperature to avoid wrinkling had other defects such as hot cracks and shrinkage cracks.

In Table VIII below are the tensile properties of alloys 12, 14 and the comparative alloy HU as listed in "American Casting Institute Data Sheet "is mentioned.

Alloys 12 and 14 coupons were made from Samples of forms 1 and 2 worked out and examined in the as-cast state, while the tensile properties of the alloy 21 was examined on transverse samples from a butt weld produced with a filler material of the same type became.

Tempe
rature
( ⁶ C) Table VIII Tensile strength
speed _o
(N / mnr) strain A
Schnü
tion Legie
tion 21 Stretch
border 537 3.5 3.5 14th 21 331 504 2.0 1.5 649 321 343 2.0 4.0 12th 760 209 291 11.0 14.5 871 160 158 20.0 28.0 982 87 91 16.0 37.0 21 53 440 1.0 1.0 * 21 871 378 152 19.0 16.5 21 102 483 9.0 "- HU 871 276 138 16.0 - 982 - 69 28.0 —_ 43

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With regard to alloy 21, it should be pointed out that its slight elongation and constriction outside the weld was in the base material.

In the following Table IX the results of a cyclic oxidation are summarized, which in the in connection with Example 1 described manner were carried out. The were in the welded state examined samples from 13mm butt welds worked out and included both the base material and the heat-affected zone and the weld metal with 5o to 75%.

The data in Table IX show that the molybdenum-free alloys compared to the four conventional alloys have excellent resistance to oxidation both as cast and after welding. The relatively low resistance to oxidation of alloy 20 can be reduced to below the preferred Minimum content of 2.5% lying silicon content, while the low resistance to oxidation of alloy L results from the lack of boron explained.

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Table IX Weight loss
(mg / cnr alloy State 5.95
5.46 12th As-cast state 7.04 13th welded 18.10
25.72 20th As-cast state 8.42 22nd welded 6.50 23 welded 5.79 24 welded 4.77 25th welded 18.38
18.28 L. As-cast state 9.76 M. As-cast state 5.21 Hastelloy X deformed, annealed 11.7 Type 310 SS deformed, annealed

In the case of welding tests carried out according to Example 1, with the exception of alloys 16 and 17 none of the samples from alloys 12-25 showed weld cracks in the heat affected zone. The weld cracks of alloy 16 can be attributed to its carbon content, which is below the preferred value, while the weld cracks of alloy 17 due to its silicon content, which is below the preferred value are justified. Alloys E through J were both in the heat affected zone and in the welding

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well cracked even to a large extent and are therefore not suitable as a base material.

In contrast, alloy L was only cracked in the weld metal.

Samples of alloys 13, 18, 19 and K were used under Use of a filler material of the same type, butt-welded connections are made. The weld samples Alloys 13, 18 and 19 were completely free of cracks, while Alloy K was severely cracked exhibited heat affected zone. This is likely due to their low nickel content of 19,996.

Alloys 13 and 19 were tested in terms of their long-term stability in the as-cast state with those from the Examined results apparent from Table X below. The short service life of alloy 13 in a Load of 55 N / mm is possibly due to casting defects and is not significant.

Creep tests on transverse specimens made from 13 mm butt welds of alloy 18 using a filler material with 22 # chromium, 19% iron, 6% molybdenum and 0.1396 boron, the remainder being nickel, showed the excellent results shown in Table X below.

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Bela Tabel X Service life Legie stung strain Snug tion (N / mm ² ) tion (H) 69 (Ji) (%) . 6.1 13th 55 24.0 26.3 5.0 41.5 8.5 8.5 88.6 20.7 7.0 7.0 824.0 41.5 6.0 7.3 308.2 18th 38.0 8.0 12.5 725.3 69 7.0 15.4 9.3 19th 55 11.0 18.1 57.3 41.5 23.0 19.2 203.8 16.0 21.7

The nickel-chromium alloy in question is particularly suitable as a material for parts that are used in exposed to high temperatures in an oxidizing atmosphere. The alloy is also suitable but also for all uses that require high corrosion resistance, creep resistance and Require creep rupture strength at high temperatures.

Castings made from the alloy are particularly suitable for use in vehicle turbines and for the manufacture of Welded joints.

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Claims (8)

International Nickel Limited, Thames House, Millbank, Londont S.W. 1, UK claims t 1. Nickel-chromium alloy, consisting of 0 to 1.4% carbon, 0 to 8.5% molybdenum with a total content of molybdenum and six times the carbon content of at most 8.5%, 1.5 to 4% silicon, 0.1 to 1% boron, 16 to 30% chromium, 0 to 4.5% manganese, 0 to 50% Iron and 0 to 2.2% niobium, the remainder including impurities from the smelting process at least 30% Nickel that is molybdenum-free at most 0.5% boron and at most 49% nickel and with a carbon content contains more than 0.05% at most 0.5% boron. 2. Alloy according to claim 1, but whose nickel content is at least 35%. 3. Alloy according to claim 1 or 2, the total content of which of molybdenum and six times the carbon content is at least 5.4%. 4. Alloy according to one or more of claims 1 to 3, which, however, ο, 005 to 0.05% carbon, 5 to 8% Molybdenum contains 2 to 4% silicon, 0.2 to 0.8% manganese, 19 to 24% chromium, up to 30% iron and 0.1 to 0.5% boron. 5. Alloy according to claim 4, but the carbon content of which is at most 0.04%. 6. Alloy according to one or more of claims 1 to 3, 509809/0744 but which are 0.8 to 1.296 carbon, 2.5 to 3.596 silicon, 0.5 to 3.096 manganese, 19 to 23% chromium, 30 to Contains 47% iron and 0.2-0.4% boron. 7. Process for producing a nickel-chromium alloy with good castability, weldability and oxidation resistance, consisting of 0 to 1.4% carbon, 0 to 8.5% molybdenum, 1.5 to 4% silicon, 0.1 to 1% boron, 16 to 30% chromium, 0 to 4.5% manganese, 0 to 50% iron and 0 to 2.2% niobium, the remainder including impurities caused by the smelting at least 30% nickel, characterized in that the total content of molybdenum and six times the carbon content to a maximum of 8.5% and in the absence of Molybdenum the boron content to a maximum of 0.5% and the nickel content to a maximum of 49% and with a carbon content above 0.05% of the boron content can be adjusted to a maximum of 0.5%. 8. Use of an alloy according to claims 1 to 6 as a material for the production of cast parts with high resistance to oxidation and creep rupture strength as well good weldability. 509809/0744