DE1608222C - Use of a heat-resistant, hardening cobalt nickel chromium iron alloy as material for springs - Google Patents

Description

The invention relates to the use of a heat-resistant, precipitation-hardening cobalt-nickel-chromium-iron alloy as a material for springs which can be used up to temperatures of 600 ^° C. and more.

For objects and parts that are exposed to mechanical loads at high temperatures, materials are required that are characterized by their high temperature strength and corrosion resistance. In addition, materials for the manufacture of heavily stressed springs have spring systems and vibration elements the demand for favorable elastic properties and sufficient fatigue strength to be sufficient up to the highest possible temperatures. Spring alloys should also be as possible have low elastic after-effects, are not subject to aging and are wear-resistant. In the end is, especially in precision engineering, the condition that the spring material to be used is not ferromagnetic.

In order to meet the requirement for high temperature strength, there are already numerous precipitation hardening Nickel-based alloys have been proposed (materials handbook »Non-ferrous metals«, 2nd edition, 1960, Section III Ni / 5, pp. 1 to 7). These materials usually contain nickel, chromium and iron as main components, hardness-increasing additives such as molybdenum, tungsten or niobium and also one the hardening component such as titanium. The demand for cheap elastic Properties under static and dynamic stress as well as after low mechanical hysteresis However, these materials are not sufficient even at high application temperatures. .

From the German patent specification 723 911 is also already known, for workpieces, which must have a low elongation rate and a high creep strength at high temperatures, to use alloys consisting of 50 to 70 7o cobalt and nickel, but at least 15 ° / ₀ cobalt , 12 to 25% chromium, 2.5 to 15% molybdenum or tungsten, individually or together, 0 to 30% iron and one or more of the elements titanium (0.3 to 12%, in particular up to 5%), tantalum (up to 15%), niobium (up to 15%), thorium (up to 8 7o> in particular up to 5%) and optionally up to 1% of customary deoxidation and processing additives, namely silicon, magnesium, manganese, beryllium, aluminum, alkali and alkaline earth metals, exist.

In order to achieve the desired high-temperature strength, hardening by cold deformation or high-temperature preheating is used intended. However, this document does not indicate that the aforementioned Alloys also remain elastic up to temperatures of 600 ° C and above, so that they up to these temperatures can be used as spring material.

The prior art also includes non-ferromagnetic heat-resistant spring alloys based on cobalt with a cobalt content of 38 to 45 70> a nickel content of 16 to 26%. a chromium content of 12 to 21 ⁰ I ₀ , an iron content of 5 to 16 ° / ₀ and a molybdenum and tungsten content of 6 to 10 ° / _{0 together} ; These materials contain titanium or titanium and beryllium as a hardening additive, namely around 1 ⁰ J ₀ titanium and possibly a few tenths of a percent beryllium ("Zeitschrift für Metallkunde", vol. 57, year 1966, p. 635).

In the highly cured state, the tensile strength and the modulus of elasticity fall of such cobalt alloys with titanium and beryllium addition to the continuous use temperature of 450 ⁰ C by only about 157o relative to the value that these material characteristics comprise at room temperature (Table 1; F i g 1 and 2: alloy A). The spring force of a spring made of this material, which is continuously exposed to a temperature of 450 ° C., only decreases by around ¹ I _{1 of} its value at room temperature at this temperature, and this change is reversible.

Although spring alloys of this type already meet high mechanical-thermal loads, But they are not sufficient if the spring properties are favorable up to temperatures of 600 ° C and more and high corrosion resistance are required.

According to the invention, these requirements are met through the use of a heat-resistant precipitation-hardening cobalt-nickel-chromium-iron alloy, from

38 until 45% Cobalt, 22nd until 28% Nickel, 10 until 14% Chrome, 5 until 10% Iron, 3 until 5% Molybdenum, 3 until 5% Tungsten, 1.6 until 4% Titanium, 0.4 until 2% Aluminum, 0.3 until 1.5% Manganese, 0.2 until 1.5% Silicon and less than 0.1% carbon

δο exists.

The table below shows a heat-resistant spring alloy belonging to the state of the art Cobalt base with beryllium addition (alloy A), three alloys containing only one titanium addition (alloys B to D) and eight alloys to be used according to the invention with the addition of titanium and aluminum (Alloys E to M) are listed. These alloys have been subjected to a homogenization annealing

1 mm thick sheet metal strips were produced at 1100 or 1150 ^° C., the final degree of deformation being 80 or 60%. The curing was carried out at 550, 600 and 700 ⁰ C, the annealing time was in each case a few hours, especially 2 to 4 hours. In a number of samples, curing was also carried out from the homogenized state, i.e. without prior cold deformation.

table

Heat-resistant spring alloys based on cobalt Composition in percent by weight

alloy

Co Ni Cr Fe Mon W. Be Ti Al Mn Si 41.50 25.80 12.0 10.0 4.0 3.9 0.25 1.0 0.90 0.50 41.80 26.00 12.05 9.95 4.11 3.84 - 0.83 - 0.57 0.60 41.60 25.95 12.05 9.75 4.19 3.87 - 1.02 - 0.71 0.56 41.60 25.95 12.15 9.20 4.42 3.87 - 1.55 - 0.77 0.56 41.45 25.95 12.15 8.20 4.19 3.92 - 1.95 0.73 - 41.00 26.50 12.05 8.70 3.95 3.90 .— 2.00 0.63 0.90 0.53 41.40 26.95 11.50 7.35 4.18 4.00 - 2.24 0.68 0.98 0.82 41.70 26.10 12.10 8.10 4.10 3.74 - 1.9 1.10 0.83 0.64 41.60 26.10 12.10 7.30 4.07 3.74 2.28 1.28 0.83 0.58 41.60 26.0 12.10 6.65 4.13 3.77 -. 2.84 1.40 0.84 0.57 41.8 25.9 12.2 5.9 4.12 3.77 - 3.24 1.68 0.85 0.57 41.8 26.1 12.1 5.25 3.92 3.77 - 3.8 1.77 0.83 0.58

A.
B.
C.
D.
E.
F.
G.
H.
J.
K.
L.
M.

<0.05
0.01
0.007
0.01

0.02

Surprisingly, the investigation has technological, physical and physico-chemical material-characteristics showed that by increasing the titanium content of about 1 ° / o ^o f 1.6 to 4 ° / ₀ and the use of aluminum in a concentration of 0, 4 remain to 2 ° / o obtained ⁱⁿ place of the conventionally used in high quality spring alloys, beryllium aushärtungsbestimmenden element not only the elastic properties of these materials, but their continuous use temperature increases considerably.

The hardening process in the titanium and aluminum-containing spring alloys to be used according to the invention based on cobalt (alloys E to M) is compared to that of the spring alloy containing beryilium (Alloy A) completely changed: Instead of Guinier-Preston zones and those causing hardening thin precipitations parallel to {100] planes ("Zeitschrift für Metallkunde", vol. 57, year 1966, P. 635 to 641) precipitates occur in the cobalt alloys with aluminum and increased titanium additions the face-centered cubic y'-phase and - mainly after curing from the cold-formed State - primary precipitations of the hexagonal planes arranged parallel to {III} planes ? 7-phase on.

Beryllium- and aluminum-free spring alloys based on cobalt with a titanium content between 0.8 and 1.55 percent by weight (alloys B, C and D) harden only slightly from the soft state out.

F i g. 1 shows the short-term hot tensile strength of the previously known alloy A and the alloy F to be used according to the invention in the hard, maximally tempered state. For comparison, their standardized tensile strength is plotted as a function of temperature. The curve it can be seen that the tensile strength of the inventive alloy itself to be used at 600 ⁰ C / o by only about 2O ° decreases its value at room temperature.

The yield point of the alloys to be used according to the invention reaches in the maximum quenched and tempered state up to more than 99% of the respective tensile strength value. For example, the yield strength of a 7.5 mm thick rod of alloy M in the hard-hardened state was 236 kp / mm ² and the associated tensile strength was 238 kp / mm ² .

The spring bending limit σ ^ ε according to DIN 50 151 was determined on a hard-hardened sample of alloy G to be GbE = 160 kp / mm ² . In the fatigue test on 0.8 mm thick, hard-hardened samples of alloy G with 3 · 10 load cycles, a flexural fatigue strength of Obxv = ± 38 kp / mm ^{2 was found} .

The modulus of elasticity of the alloys to be used according to the invention decreases approximately linearly with increasing temperature. In the case of alloys F and G, it is around 18,500 kp / mm ² at 600 ° C compared to 22,000 kp / mm ² at room temperature, so that the force of a spring made using this alloy is only about Ve less at 600 ° C than at room temperature; this change has also proven to be reversible.

F i g. 2 shows the Vickers hardness determined on hard and soft hardened samples of alloy A and the alloys L and M to be used according to the invention after various annealing times (1 and 100 hours) as a function of temperature. The course of the "softening curves" illustrates the significant improvement that is achieved by a specific titanium and aluminum addition: Opposite the beryiliumhaltigen spring alloy A, the softening temperature increases by more than 200 ⁰ C. Surprisingly, according to the invention to be used alloys, in particular the Alloys with increased titanium and aluminum content, also a significantly more favorable hardening behavior from the soft state. While alloy A only achieves a Vickers hardness of 275 kp / mm ² in the soft hardened state, the Vickers hardness of the soft hardened alloys L and M is 375 kp / mm ² . The hardening from the soft state also leads to a higher resistance to tempering of the alloys containing Ti and Al. The hardness is not yet covered soft cured samples of alloys L and M, even with 160stündiger heating at 800 ⁰ C from.

All of the alloys to be used according to the invention are not ferromagnetic and have high corrosion resistance. Because of the elastic properties, which are still favorable even at temperatures up to at least 600 ^° C., they are particularly suitable for the production of springs, spring systems and vibration elements that are subject to strong mechanical and thermal loads, such as leaf, snap, helical and spiral springs or tensioning straps, tensioning wires, membranes and Bourdon systems.

1 sheet of drawings

Claims (1)

Claim: Use of a heat-resistant precipitation hardening cobalt-nickel-chromium-iron alloy, consisting of 38 until 45 7o Cobalt, 22nd until 28% Nickel, 10 until 14% Chrome, 5 until 10% Iron, 3 until 5% Molybdenum, 3 until 5% Tungsten, 1.6 until 4% Titanium, 0.4 until 2% Aluminum, 0.3 until 1.5% Manganese, 0.2 until 1.5% Silicon, less than 0.17o Carbon, as a material for springs that can be used up to temperatures of 600 ^° C. and more.