EP1206588B1 - Iron-nickel alloy with creep resistance and low thermal expansion - Google Patents

Description

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

It is known that iron-based alloys with about 36% nickel have low coefficients of thermal expansion in the temperature range between 20 and 100 ° C. For some decades now, these alloys have been used where constant lengths are required, even with temperature changes, such as precision instruments, watches, bimetals. With the development of color television sets and computer monitors in the direction of higher resolution, color fidelity and contrast strength even under unfavorable lighting conditions and especially in view of the trend towards ever flatter and larger screens, iron-nickel materials are increasingly being used for shadow masks. Technical iron-nickel alloys with about 36% nickel have a thermal expansion coefficient between 1.2 and 1.8 x 10 ^-6 / K in the temperature range from 20 to 100 ° C, as they prevail in conventional display tubes, in the soft-annealed state, such as this is referred to in the steel-iron material sheet (SEW-385, 1991 edition). For shadow masks in particular, further developed materials with around 36% nickel are used, which achieve lower thermal expansion coefficients in the temperature range from 20 to 100 ° C between 0.6 and 1.2 x 10 ^-6 / K.

For shadow masks pre-stressed in frames, a low-expansion is used Material with an improved compared to the previously used alloy Creep resistance required. The shadow masks and the frame parts for the Shadow masks become a so-called at temperatures up to about 580 ° C Blackening annealing. This creates a dark iron oxide layer with which a better visual image quality is achieved.

The previously used iron-based alloy with approximately 36% nickel achieved a creep resistance A ₈₀ of approximately 2.6% under the following test conditions: 1 hour at 580 ° C under a load of 138 MPa.

The prestressing of the shadow masks in the vertical direction is generated with the vertical frame parts. Up to now, iron-nickel alloys with approximately 41% nickel have been used as the material, these alloys being known as materials for, for example, metal glass melting or for lead frames. The technological properties are as follows: The creep resistance A ₈₀ is about 0.5%, measured under the same test conditions as previously described for the 36% nickel-containing alloy, ie 1 hour at 580 ° C under a load of 138 MPa. The vertical frame parts made of this alloy expand according to a thermal expansion coefficient of about 4.8 x 10 ^-6 / K in the temperature range of 20 to 100 ° C more than the shadow mask made of the iron-nickel alloy with about 36% nickel is made.

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

Just like for the shadow masks, materials are also used for the frame parts required an improved compared to the previously used alloys Have creep resistance at temperatures up to 580 ° C. The size and the temperature-dependent course of the expansion coefficients should that of materials used so far almost correspond.

It is also known that suitable additives to iron-nickel alloys can lead to the formation of precipitates. As such additives, for example
Titanium and aluminum used in combination. The formation of a γ (Ni ₃ Ti / Ni ₃ Al) phase increases the yield strength and strength.

However, the total contents of the elements titanium and aluminum can be too high Too much increase in coefficient of thermal expansion.

From DE-C 29 40 532 a hardenable nickel-iron casting alloy with a linear expansion coefficient <5 x 10 ^-6 / ° C at 20 to 300 ° C and a yield strength of over 350 N / mm ² at 20 ° C is known has become, consisting of 35-45% by weight of nickel, less than 4% by weight of free titanium, 0-1% by weight of niobium, 1.5-2.5% by weight of cobalt, the remainder iron and melting-related impurities , This alloy is suitable for mechanically and thermally highly stressed machine parts, for example rotors of gas-dynamic pressure wave machines.

JP 10310845 is a high strength alloy with low Thermal expansion coefficients, the following (in mass%) Composition has: ≤ 0.15% C, ≤ 0.5% Si, ≤ 0.5% Mn, 0.5-4% Ti, ≤ 0.2% Al, 30.7 - 43.0% Ni and ≤ 14% Co. The following can be used within limits of ≤ 1.0% Elements are alloyed, namely V, W, Nb and Mo and further within limits ≤ 0.5% S, Pb, Ca, Se, balance iron. This alloy is said to be preferred for tools and machine fixtures, such as lathe beds.

JP 09268348 discloses an iron-nickel alloy which is suitable for electronic Components to be used and the following composition (in mass%) has: 30 - 55% Ni, ≤ 1.2% Si, ≤ 1.5% Mn, balance Fe. The C content within the Impurities should be ≤ 0.02%. The alloy can also ≤ 12% Co include. A preferred alloy also has the following Elements on: 1.0-3.0% of one or ≥ 2 of the elements W, Mo, V, Al, Ti, Nb as well 0.05 - 1.0% Zr and / or Be on.

JP 04202642 describes an Fe-Ni alloy of high strength and low thermal expansion coefficient used for plating and soldering can be. The alloy has the following composition (in mass%): 39-45% Ni, ≤ 1% Co, 0.1-07% Mn, ≤ 0.30% Si, 0.1-0.2% Al, ≤ 0.01% P, ≤ 0.003% S, ≤ 0.004% O, ≤ 0.003% N, ≤ 0.001% C, 1.0-3.0% Ti, balance Fe.

An austenitic alloy has become known from US Pat. No. 4,006,012 can preferably be used for composite materials and (in mass%) has the following elements: 36-54% Ni, up to 12% Co, up to 15% Cr, up to 10% Mo, 1.0-3.75% Ti, up to 2% Al, up to 0.1% C, up to 2% Mn, up to 1% Si, up to 0.05% B, balance Fe, whereby the Fe content should be at least 24%.

Finally, an austenitic alloy is described in DE-A 2162596, which a composition similar to that shown in US Pat. No. 4,006,012, having. Fastening and connecting means are used as areas of application specified.

All of the alloys described above have large ones Spreading ranges in particular for the element Ni, with high Co contents should be possible. Specific information on thermal expansion coefficients are not made so that a variety of combinations are possible to develop suitable compositions for the respective application.

The object of the invention is to provide a creep-resistant and low-expansion iron-nickel alloy to optimize the no longer has disadvantages mentioned in the prior art, inexpensive in Manufacturing is and also for components of television sets and monitors can be used.

This goal is achieved by using a creep-resistant and low-expansion iron-nickel alloy, which (in mass%) in addition to max. 0.02% C, max. 0.05% Mn, and max. 0.05% Si has an Al content of 0.05 to 0.3%, a Ti content of 1.5 to 2.5%, 0.2-1.0% Nb, and a Ni content of 39.0 to 45 , 0%, Co as optional component ≤ 0.5%, rest iron and manufacturing-related admixtures and has a thermal expansion coefficient <6.0 x 10 ^-6 / K in the temperature range from 20 to 100 ° C for frame parts for screen and monitor shadow masks.

Surprisingly, it has now been found that the iron-nickel alloys to which only defined contents of the element aluminum or titanium alone are alloyed be, the required improvement in creep resistance at 580 ° C below the Load of 138 MPa in the hard-rolled state reached.

The required technological properties for the application as Material, especially for vertical frame parts for shadow masks, can be used with the iron-nickel alloys according to the invention are adjusted, the one Contain nickel content between 42.0 and 45.0 mass percent.

The alloy used according to the invention is characterized by an excellent Processability and does not require any additional during production Process steps. It also shows one that meets your needs Long-term stability of their thermal properties.

An alloy E1, which can be hardened by its aluminum content, achieves with A ₈₀ = 0.17% at the test temperature 580 ° C, whereby the load of 138 MPa is effective for 1 hour, an iron compared to the normal state of the art. Nickel alloy T2 with 41% nickel, significantly improved creep resistance.

The mechanical properties, which were determined in the hot tensile test with and without load at the test temperature 580 ° C, as well as the magnetic coercive field strength and the thermal expansion coefficients, are for alloy E1 compared to the properties of alloys T1 and T2, which are state of the art correspond, listed in Table 1. Mechanical properties Yield strength, tensile strength, elongation at break at 580 ° C, determined in the hot tensile test, as well as the creep strength at 1 hour at 580 ° C under a load of 138 MPa, the coercive field strength and the thermal expansion coefficients of alloy E1 compared to alloys T1 and T2, which correspond to the state of the art. The test specimens were made from 1.4 mm cold-rolled strip. alloy E1 E2 T1 T2 Warm tensile test at 580 ° C yield strength R _p0.005 (N / mm ² ) 369 261 189 R _p0.2 (N / mm ² ) 574 206 322 312 tensile strenght R _m (N / mm ² ) 613 566 381 411 elongation A ₈₀ (%) 4.3 18 6.4 7.5 creep (Load 138 N / mm ² )
A ₈₀ (580 ° C / 1h) (%) 0.17 00:06 2.61 0.54 coercivity H _c (580 ° C / 15min) (A / m) 433 424 405 H _c (580 ° C / 1h) (A / m) 327 154 170 Thermal expansion coefficient (from 20 ° C to the 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 test specimens were soft-annealed and cured (load 200 MPa when testing creep resistance).

The coercive field strengths H _{c of} the alloy E1 and the alloys T1 and T2, which correspond to the prior art, are almost the same after a heat treatment of 15 minutes at 580 ° C. After a one-hour heat treatment at 580 ° C, the coercive field strengths H _c of alloy E1 are sufficiently low for use as a material for the frame parts for the shadow mask.

The thermal expansion coefficients in the temperature range of 20 to 100 ° C with about 4.8 x 10 ^-6 / K in the case of alloy E1 meet the requirements for use as materials for the vertical frame parts. The temperature-dependent course of the expansion coefficients of the alloy E1 according to the invention is similar to the course of the expansion coefficients of the alloy T2, which corresponds to the prior art. This is shown in Figure 1, whereby it can also be seen that the expansion coefficients of the alloys E1 and T2 intersect with the expansion coefficient of the alloy T1 in the temperature profile between 270 ° C and 320 ° C, so that the thermal expansion coefficients of the alloy with the lower nickel content below the crossing temperature are lower than that of the thermal expansion coefficient of the alloys with the higher nickel contents. Behavior reverses above the crossing temperature. The break point temperature of the thermal expansion coefficient corresponds approximately to the Curie temperature T _{c of} the corresponding alloy.

Figure 1: Temperature-dependent expansion coefficients. the Alloys E1 and E2 and those of alloys T1 and T2, which the State of the art.

Exemplary chemical compositions of the alloys E1 and E2 are listed in Table 2 in comparison to the compositions of the alloys T1 and T2, which correspond to the prior art. Exemplary chemical compositions of alloys E1 and E2 compared to exemplary compositions of alloys T1 and T2 which correspond to the prior art. element E1 E2 T1 T2 (Dimensions-%) 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 Ni 42,95 42.2 36.15 40,80 Mn 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 Co 0.01 0.02 0.04 0.04 O 0.001 0,002 0,002 0,002

The limit values for the chemical compositions of alloy E1 are described in the following table. Limit values for the chemical composition of alloy E1. Element (mass%) E1 minimal maximum C 0.2 S 0.005 Cr 0.2 Ni 39.0 45.0 Mn 0.3 Si 0.3 Mo 0.1 Ti 0.1 Nb 0.01 Cu 0.1 Fe R100,0 P 0.005 al 0.1 3.0 mg 0.005 Zr 0.10 Co 0.3 O 0.001

Another embodiment of the alloy is variant E _2. The preferred composition contains 39.0-45.0% Ni, 1.5-2.5% Ti, 0.05-0.3% Al and 0.2 - 1.0% Nb as well as the rest iron and manufacturing-related admixtures according to Table 4.

The following table describes the limit values of the chemical compositions of the alloy E2 used according to the invention. Limit values for the chemical composition of the alloy E2 used according to the invention. Element (mass%) E2 minimal maximum C 0.2 S 0.005 Cr 0.2 Ni 39.0 45.0 Mn 0.3 Si 0.3 Mo 0.3 al 0.05 0.3 Nb 0.2 1.0 Cu 0.3 Fe R100,0 P 0.01 Ti 0.5 2.5 mg 0.005 Zr 0.10 Co 0.5 O 0,003

Alloy E2 can first be formed into frame parts in the soft annealed condition. It then meets the high requirements in the hardened state (eg 30 min at 750 ° C) with A ₈₀ <0.1% in the creep resistance test at 580 ° C for 1 hour with the increased load of 200 MPa. Values for the mechanical, magnetic and thermal expansion properties are listed in Table 1. A typical composition of alloy E1 is known in Table 2.

Claims (1)

1. Use of a creep resistant and low expansive iron-nickel alloy, which contains (in % by mass), besides max. 0.02% C, max. 0.05% Mn and max. 0.05% Si, also an Al content of 0.05 to 0.3%, a Ti content of 1.5 to 2.5%, 0.2-1.0% Nb as well as a Ni content of 39.0 to 45.0%, ≤ 0.5% cobalt as optional component, rest iron and manufacture dependent impurities, wherein the alloy has a thermal coefficient of expansion of < 6.0 x 10^-6/K in the temperature range comprised between 20 and 100°C, for frame parts of screen and monitor shadow masks.

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