DE1295850B - Use of a nickel-chromium-tungsten alloy - Google Patents

Description

The invention relates to the use of a nickel-chromium-tungsten alloy which contains up to 1.0% carbon, 26 to 38% chromium, up to 0.2% manganese, up to 0.2% silicon and 10 to 25% tungsten contains, the remainder of nickel with impurities in the usual amounts, for the 'production of objects that at temperatures up to 1370 ⁰ C a high tensile strength, a high thermal shock resistance and a creep limit for a strain rate of 1 · ΙΟ " ⁴ % / h in the 1000-hour test at a temperature of 1320 ¹ C of more than 20 kg / cm- must have.

The need for alloys with high heat resistance, high creep resistance, high resistance to corrosion and thermal shock loads of up to 1370 ° C has existed for a long time. Such alloys are particularly desirable in place of ceramic, refractory materials for rotary kilns and slab furnaces and radiant tubes that operate at temperatures up to 1370 "C. Conventional alloys have been used in this temperature range have been found to be unsatisfactory for most uses, and because of the high creep, corrosion and strength loss at temperatures of about 1200 to 1370 ^'1 C.

It has now been found that an alloy of the composition below has a high tensile strength, high creep resistance and high thermal shock resistance at temperatures up to 1370 C owns. The surprising properties of this alloy seem primarily from the setting the carbon, iron and tungsten content in a nickel-chromium-based alloy to hang out. This alloy includes the following range: C up to 1.0%, Cr 26% to 38%, W 10% up to 25%, Mn 0.2% maximum, Si 0.2% maximum, Ni remainder with the usual impurities in the usual amounts.

The following alloy range is appropriate for continuous operation at or above 1150 "C: C 0.2% to 0.75%, Cr 28% to 35%, W 13% to 19%, remainder Ni 40% to 60%.

A suitable composition is also: C 0.5%, Cr 31%, Ni 51%, W 17%. The rest exists from impurities in the usual amounts.

The ranges given above must be adhered to if the desired high tensile strength, the high creep resistance, the corrosion resistance and the high thermal shock resistance at temperatures up to 1370 ° C should be. As the operating temperature rises, the carbon content is expediently at lower end of the specified carbon range, and the manganese and silicon contents should be be as low as the impurities usually occurring together with nickel, e.g. B. iron.

Alloys, which among other things can also have the composition given above, are although known per se, however, only in connection with a heat treatment process for production of objects with high rigidity and spring force made of such alloys.

The invention is explained further with reference to the following examples and figures.

F i g. 1 shows the tendency of the alloy's creep speed depending on the tungsten content at ratio of nickel to chromium kept approximately constant;

F i g. Fig. 2 shows the creep rate tendency of the alloy with a tungsten content of about 14%, depending on the carbon content;

F i g. 3 shows the tendency of the creep speed of the alloy, depending on the tungsten content, the chromium content is kept constant and the sum of the nickel and tungsten components in each case accounts for approximately 70%;

F i g. 4 shows the tendency of the creep speed of the alloy, depending on the tungsten content, the nickel content is kept constant and the sum of the chromium and tungsten components is approximately Accounts for 50%;

F i g. 5 shows the relationship between the creep rupture strength of the alloy and the temperature with the duration of the experiment as a parameter.

example 1

To determine the effectiveness of various combinations within the wide range of alloys with regard to creep speed at 1320 C a number of alloys are melted. The alloys are made by Casting and subsequent machining test specimens produced in general have a gauge length of 25.4 mm and a diameter of 3.7 mm. The respective sample is in an electrically heated oven brought to the set temperature and then a permanent one Subjected to bending stress exerted by a weighted lever. the The sample is on one side in a steel block and on the other side on the lever, each held in a loose sliding fit.

The creep speed is measured at the end of the lever as angular deflection per time in 7 hours in relation to a standard horizontal. The test values determined by this method, here referred to as the "tendency of the creep speed" (Creep Testing by a Cantilever-Bending Method, GT H arris et al., Journal of the Iron and Steel Institute, June 1950, pp. 139 to 144), correspond to some extent to those that occur under tensile stress (material handbook steel and iron, 3rd edition, 1953, p. C 44-4). The bending load exerted by the lever arm is 17.6 kg / cm ² . The compositions of a number of these alloys and the creep rate tendency determined in each case after the test described are listed in Table I:

Table I.

Composition (%) C. W. Tendency of Cr 0.02 9.95 Creep
swiftly
speed Ni 37.1 0.02 14.44 (7h) 48.2 31.7 0.02 • 13.77 0.012 49.0 34.3 0.27 14.38 0.008 45.0 33.7 0.41 14.11 0.020 47.7 33.0 0.012 48.5 0.006

continuation

Composition (%) C. W. Tendency of 0.52 14.52 Creeping
speed- ^s Cr 0.67 14.76 speed Ni 33.3 1.01 14.20 (7h) 48.4 33.7 0.59 14.35 0.006 48.1 33.5 0.59 18.75 0.001 48.0 33.3 0.61 24.16 0.013 47.8 29.1 0.56 29.67 0.023 47.5 24.2 0.57 14.82 0.007 47.7 19.2 0.61 14.17 0.026 47.3 28.7 0.01 19.4 fast 51.5 24.5 0.31 17.2 0.097 57.4 29.5 0.01 19.92 fast 46.8 29.8 0.04 ■ 18.8 0.006 47.7 30.0 0.10 19.4 Ό, ΟΙΟ 48.4 30.5 0.15 19.12 0.308 48.8 - 30.8 0.19 20.2 0.069 47.7 30.4 0.31 18.8 0.155 49.6 30.3 0.37 19.4 0.070 47.9 30.7 0.38 9.12 0.038 48.5 29.9 0.37 13.6 0.275 48.2 29.9 0.40 14.8 0.080 59.1 29.7 0.41 17.36 1,140 55.5 28.9 0.40 19.76 0.230 52.8 28.6 0.40 20.96 0.143 50.7 30.1 0.40 22.72 0.149 49.0 29.6 0.05 14.7 0.275 ΑΊΑ 29.0 0.04 15.4 0.350 45.7 31.8 0.03 16.4 1.030 53.5 30.6 0.05 17.6 0.021 55.1 30.8 0.01 17.3 0.155 52.7 31.1 0.097 53.0 30.7 0.155 50.0 0.030

70 ° / ü. The in these alloys after The tendency of the creep speed determined in Example 1 depends on the method Tungsten content in FIG. 3 applied.

The tendency of the creep speed resulting from the same procedure, depending on the varied tungsten content with a constant nickel content of about 48% and a constant one Sum of chromium and tungsten components in the amount

ίο of 50% is shown in FIG. 4 shown.

Example 4

For the alloys listed in Table II below, the stress exerted on the test rod, the time until fracture occurs and the tendency for the creep rate are given in Table III, depending on the temperature and carbon content.

20th C. Mn Table II Si Ni Cr W. (%) (%) (%) (%) (%) (%) 25 ° ^'01 0.02 0.06 47.5 30.7 20.0 0.05 0.01 0.06 49.5 30.6 19.8 0.01 0.01 0.07 50.0 28.6 20.0 0.01 0.01 0.02 49.8 28.2 20.0 0.01 0.02 0.18 47.7 30.7 19.8 ³⁰ 0.38 0.02 0.02 48.5 29.5 20.0 0.66 0.02 0.10 46.1 27.3 20.5 0.48 0.02 0.04 32.3 49.0 16.4 0.23 0.01 0.01 44.6 31.7 19.0 ³⁵ 0.38 0.02 0.02 48.5 29.5 20.0 0.31 0.01 0.01 45.8 31.6 19.0 0.41 0.01 0.01 45.8 31.7 19.0 0.55 0.01 0.01 50.5 29.7 19.0 4 ° 0.10 0.01 0.01 45.8 31.6 19.0

For some of the alloys given in Table I, the creep rate tendency depending on the tungsten content with an approximately constant ratio of the proportions of Nickel and chromium determined and together with corresponding ones and not listed in the table Values in the in FIG. 1 plotted the diagram shown.

Example 2

A number of alloys with 14% tungsten and various carbon contents are used Determination of the influence of carbon melted. Which is with that described in Example 1 The tendency of the creep speed resulting from the test arrangement depends on the particular Carbon content in Fig. 2 shown.

Example 3

A number of alloys with 0.6% and 0.4% carbon and varying tungsten contents are used manufactured. The chromium content is 30% and the nickel content varies with the tungsten content, so that the sum of the nickel and tungsten content approximately

C. Tabel III tendency time to the creep to break Tempe tension swiftly rature '' (%) speed (H) 0.00 (7h) 153 ( ⁰ C) 0.05 (kg / cm ² ) 0.104 18th 1320 0.00 25th 1.43 158 0.00 25th 0.057 350 0.00 25th 0.069 1520 28 0.037 184 19th 0.73 67 1260 47 1.07 552 0.38 70 0.057 663 0.66 21 0.017 300 0.66 35 0.014 76 0.48 46 0.344 496 .0.66 70 0.75 30th 0.66 35 5.05 190 1200 0.48 105 0.63 1830 70 0.011 c a break 53

continuation

Tempe
rature (%) tension tendency
the creep
swiftly
speed time to
to break ( ⁰ C) 0.66 (kg / cm ² ) (7h) (H) 1150 0.66 123 21.8 83 1090 0.66 211 2.98 125 0.66 136 0.62 212 0.45 141 0.55 595 1070 0.35 141 0.109 1870 0.55 141 0.121 1260 0.23 112 0.016 1681
no break 0.38 112 0.126 2378 1010 0.35 352 0.527 350 0.45 281 0.264 850 0.10 281 0.252 825 0.55 281 330 211 0.051 1685
no break

end elongation is achieved in 10,000 hours and the resistance to oxidation by values for the oxidation given in mm / year, converted from a 100-hour test in air. The creep rupture strength is above the temperature in the one shown in FIG. 5 plotted the diagram shown.

Table IV

IO

20th

Example 5

For the alloy identified above as being suitable, which consists of 0.5% C, 31% Cr, 51% Ni, 17% W, the remainder being normal impurities, the creep rupture strength for test times of 100 and 1000 hours are shown in Table IV as a function of temperature to rupture the specimen, the creep for a strain rate of 1 x 10- ^4% / h, ie the voltage at which 1% of lead

Creep strength 1000 hours Creep limit oxidation temperature in kg / cm ² the for a stretch
speed 152 1 x 10 "*% / h 100 hours 95 (mm / year) ( ⁰ C) the 61 (kg / cm ² ) 1100 253 39 88 1150 162 25th 67 0.46 1200 106 51 1260 68 32 1.14 1320 44 20th

Claims (1)

Claim Use of a nickel-chromium-tungsten alloy containing up to 1.0% carbon, 26 to 38% chromium, up to 0.2% manganese, up to 0.2% silicon and 10 to 25% tungsten, the The remainder consists of nickel with impurities in the usual amounts for the production of objects that have high tensile strength, high thermal shock resistance and a creep limit for a strain rate of 1 · 10 ⁴ % / h in a 100-hour test at temperatures of up to 1370 C must have at a temperature of 1320 C of more than 20 kg / cm ² . 1 sheet of drawings