PL195127B1 - Iron-nickel alloy with creep resistance and low thermal expansion - Google Patents

Abstract

The invention relates to iron-nickel alloys with creep resistance and low thermal expansion, which contain ( % by mass) no more than about 0.2 % C, no more than 0.3 % Mn, no more than 0,3 % Si, from 0.05 to 3.0 % Al, 0.1 to 3.0 % Ti, no more than 1.0 % Nb, from 39.0 to 45.0 % Ni, wherein the rest is composed of iron and impurities that can be generated during the fabrication process. The inventive alloys have a thermal expansion coefficient <6.0 x 10<-6>/K in a temperature range between 20 and 100 DEG C.

Description

The invention relates to the use of a creep-resistant nickel-iron alloy with low thermal expansion.

It is known that iron-based alloys containing about 36% nickel exhibit low thermal expansion coefficients in the temperature range between 20 and 100 ° C. For this reason, these alloys have been used for several decades in applications where constant lengths are required even with temperature changes, in devices such as precision instruments, clocks or bimetals. Along with the development of color television receivers and computer monitors towards higher resolution, color fidelity and contrast strength, also in unfavorable lighting conditions, especially due to the trend towards flatter and larger screens, materials from iron-nickel alloys. Technical iron-nickel alloys with a nickel content of about 36% have, in the temperature range of 20 to 100 ° C, as found in ordinary glow tube tubes, thermal expansion coefficients of between 1.2 and 1.8 x 10 ⁶ / K, as was given in Stahl-Eisen-Werkstoffblatt (Data for Steel-Ferrous Materials; SEW-385, 1991 edition). Especially for shadow masks, in use, is advanced materials containing about 36% nickel, which obtain lower coefficients of thermal expansion in the temperature range of ^{d 20 d 100} ° ^{C ± y} bearing which m ^{IEDs 0.6} and ^{1 s, 2} x ^{10 6} K.

For frame-tensioned shadow masks, a material with a low elongation is required, with improved creep resistance compared to previously used alloys. Shadow masks and frame housing parts for shade masks are subjected to a so-called blackout burnout at temperatures up to about 580 ° C. A dark iron oxide layer is thereby obtained, with which a better visual image quality is achieved.

Previously used iron base alloys containing about 36% nickel obtain the creep limit of about ₈₀ A 2.6% under the following test conditions: one hour at 580 ° C with a load of 138 MPa.

The pre-tension of the shadow masks in the vertical direction is achieved by means of the vertical parts of the frame housings. Previously, iron-nickel alloys containing about 41% nickel were used as material, these alloys being known as materials for e.g. glass-to-metal alloys or lead frames. Technological properties are as follows: A ₈₀ creep limit is about 0.5% measured under the test conditions as described above for the alloy containing 36% nickel, ie. One hour at 580 ° C with a load of 138 MPa. The vertical parts of the frame casing made of this alloy, according to the thermal expansion coefficient of about 4.8 x 106 / K in the temperature range from 20 to 100 ° C, extend stronger than the shadow mask, which is made of an iron-nickel alloy with a content of 36% nickel.

The horizontal parts of the casing should exhibit the same thermal expansion properties as the shadow masks, so that the same iron-nickel alloy with about 36% nickel is used for the horizontal parts of the frame casing and for the shadow masks.

As for shadow masks, materials are required for parts of the frame housing that exhibit improved creep resistance at temperatures up to 580 ° C over the alloys used previously. The size and course of changes in the thermal expansion coefficient with temperature should approximately correspond to the values for the materials used previously.

Moreover, it is known that suitable additives to ferro-nickel alloys can lead to the formation of precipitates. Examples of such additives are titanium and aluminum in combinations with one another. The formation of the γ phase (Ni ₈ Ti / Ni ₈ Al) increases the yield point and strength.

Too high the total contents of the elements titanium and aluminum may, however, excessively increase the coefficient of thermal expansion.

Due to DE-C 29 40 532, a hardenable nickel-iron foundry alloy with a linear thermal expansion coefficient <5 x 106 / ° C in the range of 20 to 300 ° C and a yield point above 350 N / mm at 20 is disclosed. ° C, consisting of 35-45 wt.% Nickel, less than 4 wt.% Free titanium, 0-1 wt.% Niobium, 1.5-2.5 wt.% Cobalt, the balance being iron and smelting impurities . This alloy is suitable for mechanically and thermally highly stressed machine parts, for example rotors in a gas dynamic shockwave charger (in superchargers).

The object of the present invention is to optimize the creep-resistant and low expansion iron-nickel alloys to the extent that they do not already exhibit the drawbacks of the known art, are cost-effective in their manufacture, and in particular those that can be used on frame shell parts. for shadow masks.

This goal was achieved by using a creep-resistant and low expansion iron-nickel alloy containing in% by mass not more than 0.02% C, maximum 0.05% Mn and maximum 0.05% Si, Al content from 0.05 to 3 , 0%, Ti content from 1.5 to 2.5%, 0.2-1.0% Nb, and Ni content from 39.0 to 45.0% Ni, Co <0.5% as a component of choice, the remainder being iron and impurities due to production and having a thermal expansion coefficient of < 6.0 x 10 ⁶ / K in the temperature range of 20 to 100 ° C, on parts of the housings for shadow masks of screens or monitors.

It has surprisingly been found that ferro-nickel alloys to which only defined contents of separate aluminum or titanium alloying elements have been incorporated, achieve the required improvement in creep resistance at 580 ° C under a load of 138 MPa in the cold-rolled condition.

The required technological properties for use as a material, in particular for the vertical parts of the frame housing for shadow masks, can be set in the iron-nickel alloys according to the invention, with a nickel content between 42.0 and 45.0% by mass.

The alloy used according to the invention is particularly workable and requires no additional processing steps. Moreover, it is characterized by long-lasting stability of thermal properties, corresponding to the needs.

The alloy used according to the invention E1, which can be dispersion-hardened thanks to the aluminum content in it, achieves a significantly improved creep resistance of A80 = 0.17% at the test temperature of 580 ° C, at a load of 138 MPa for 1 hour, compared to the conventional alloy T2-iron nickel with 41% nickel, corresponding to the state of the art.

Table 1 shows the mechanical properties determined after hot drawing at 580 ° C, both without and under load, and the magnetic coercive field strength, as well as the thermal expansion coefficients for the alloy used according to the invention E1, compared to the properties of the alloys. T1 and T2, corresponding to the known art.

T a b e l a 1

Mechanical properties: yield point, tear strength, elongation at break at 580 ° C determined after hot drawing experiments and yield point for 1 hour at 580 ° C under a load of 138 MPa, coercive field strength and thermal expansion coefficients of the alloy used according to the invention E1 , compared to the alloys T1 and T2 corresponding to the known art. The test pieces were made of a 1.4 mm thick cold-rolled strip

Stop E1 E2 T1 T2 1 2 3 4 5 Hot drawing test at 580 ° C Physical yield strength R ^p o, oo5 ( ^{N /} mm ² ) R ^p o, ² ( ^{N /} mm ² ) 369 574 206 261 322 189 312 Breaking strength ^Rm ( ^{N /} mm ² ) 613 566 381 411 Elongation A80 (%) 4.3 18 6.4 7.5 Yield point (load 138 N / mm2) A80 (580 ° C / 1h) (%) 0.17 0.06 2.61 0.54 The intensity of the coercive field Hc (580 ° C / 15 min) (A / m) Hc (580 ° C / 1 h) (A / m) 433 327 424 154 405 170

PL 195 127 B1 cont. table 1

1 2 3 4 5 Thermal expansion coefficients (from 20 ° C to test temperature T in 10'6 / K) T (° C) 50 4.78 4.11 0.63 4.98 100 4.81 3.99 1.26 4.88 150 4.83 3.95 1.76 4.62 200 4.95 4.04 2.45 4.49 250 5.09 4.28 3.69 4.42 300 5.74 5.15 5.47 4.52 350 6.94 6.38 7.01 5.18 400 8.01 7.49 8.28 6.31 450 8.92 9.43 9.34 7.28 500 9.60 9.22 10.23 8.14 550 10.30 9.89 10.98 8.91 600 11.09 10.47 11.61 9.69

In the case of alloy E2, the fittings were softened and hardened before testing (load 200 MPa during the yield stress test).

The coercive field strength H _{c of the} alloy used according to the invention E1 and the alloys T1 and T2 corresponding to the prior art are approximately the same after a heat treatment at 580 ° C for 15 minutes. After heat treatment for one hour at 580 ° C, the coercive field strengths Hc of the inventive alloy E1 are sufficiently low for its use as a material for frame housing parts for shadow masks.

Thermal expansion coefficients in the temperature range from 20 to 100 ° C, for the alloy used according to the invention E1, about 4.8 x 10 ⁶ / K, are sufficient to meet the requirements for its use as a material for vertical parts of the frame casings. The course of changes in the thermal expansion coefficient as a function of temperature for the alloy used according to the invention E1 is similar to the course of changes in the thermal expansion coefficient of the alloy T2, corresponding to the known art. This is shown in the figure, but it should also be noted that the thermal curves of the course of changes in the expansion coefficients of alloys E1 and T2 from temperature, in the temperature range between 270 ° C and 320 ° C, intersect with the curve of the expansion coefficient for alloy T1, so The thermal expansion of alloys with a lower nickel content below the intersection temperature are lower than the thermal expansion coefficients of alloys with a higher nickel content. Above the crossover temperature, the ratios reverse. The temperature of the inflection point for the coefficients of thermal expansion approximately corresponds to the Curie temperature Tc of the respective alloy.

The figure of the drawing shows the expansion coefficients of the alloys E1 and E2 used in the invention, and of the alloys T1 and T2, corresponding to the prior art, as a function of temperature.

Exemplary chemical compositions of the alloys used according to the invention E1 and E2 compared to the compositions of the alloys T1 and T2 corresponding to the prior art are given in Table 2.

T a b e l a 2

Exemplary chemical compositions of the alloys used according to the invention E1 and E2 compared to the compositions of the alloys T1 and T2 corresponding to the prior art.

Element (% by mass) E1 E2 T1 T2 1 2 3 4 5 C. 0.002 0.020 0.003 0.007 S. 0.0014 0.0006 0.0002 0.0030 N 0.001 0.001 0.0025 0.002 Cr 0.01 0.06 0.03 0.03

PL 195 127 B1 cont. table 2

1 2 3 4 5 Ni 42.95 42.2 36.15 40.80 Me 0.01 0.12 0.24 0.55 Si 0.01 0.16 0.06 0.17 Mo 0.05 0.01 Ti <0.01 1.85 <0.01 0.005 Nb 0.52 0.01 <0.01 Cu 0.02 0.05 0.04 Fe rest rest 63.3 58.30 P. 0.002 0.009 0.002 0.003 Al 1.88 0.13 0.007 0.002 Mg 0.0002 0.002 <0.001 Pb <0.001 0.001 0.001 Ca 0.0007 Zr <0.01 <0.01 What 0.01 0.02 0.04 0.04 ABOUT 0.001 0.002 0.002 0.002

The limit values for the chemical composition of the inventive alloy E1 are given in the following table.

Table 3

Limits of the chemical composition of the alloy used in the invention E1

Element (% by mass) E1 slightly maximum C. 0.2 S. 0.005 Cr 0.2 Ni 39.0 45.0 Me 0.3 Si 0.3 Mo 0.1 Ti 0.1 Nb 0.01 Cu 0.1 Fe addition to 100.0 P. 0.005 Al 0.1 3.0 Mg 0.005 Zr 0.10 What 0.3 ABOUT 0.001

PL 195 127 B1

A further embodiment of the alloy used according to the invention is represented by variant E2. The preferred recipe according to Table 4 contains in addition to 39.0-45.0% Ni, 1.5-2.5% Ti, 0.05-0.3% Al and 0.21.0% Nb, as well as iron and admixtures from production.

In the following table, the chemical composition limits of the alloy used according to the invention E2 are given.

T a b e l a 4

Limits of the chemical composition of the alloy used in the invention E2

Element (% by mass) E2 slightly maximum C. 0.2 S. 0.005 Cr 0.2 Ni 39.0 45.0 Me 0.3 Si 0.3 Mo 0.3 Al 0.05 0.3 Nb 0.2 1.0 Cu 0.3 Fe addition to 100.0 P. 0.01 Ti 0.5 2.5 Mg 0.005 Zr 0.10 What 0.5 ABOUT 0.003

The E2 alloy can first be formed into frame guard parts in the annealed condition. In the cured condition (e.g. 30 minutes at 750 ° C), showing A _8O values <0.1% in a creep test at 580 ° C for 1 hour under a load of 200 MPa, it then meets the high creep limit requirements. The values of the mechanical, magnetic properties and the coefficient of thermal expansion are given in Table 1. A typical composition of the alloy used in the invention E1 is known from Table 2.

Claims (1)

Use of a creep-resistant and low expansion iron-nickel alloy containing, in% by mass, not more than 0.02% C, maximum 0.05% Mn and maximum 0.05% Si, Al content from 0.05 to 3.0% , Ti content from 1.5 to 2.5%, 0.2-1.0% Nb and Ni content from 39.0 to 45.0% Ni, Co in the amount of <0.5% as a component of choice, with the remainder being iron and the admixtures due to production and having a thermal expansion coefficient of <6.0 x 10 ⁶ / K in the temperature range of 20 to 100 ° C, on some of the housings for shadow masks of screens or monitors.