JP7606945B2 - Welding method - Google Patents

Description

The present invention relates to a welding method used for welding low thermal expansion members that are applied to ultra-precision equipment such as semiconductor manufacturing equipment.

Conventionally, in order to maintain and improve the accuracy of ultra-precision equipment, rolled materials, forged materials and cast materials such as 36% Ni-balance Fe alloys and 32% Ni-5% Co-balance Fe alloys, which have extremely low thermal expansion coefficients around room temperature, and 42% Ni-balance Fe alloys, which exhibit low thermal expansion properties at high temperatures (hereinafter referred to as Fe-Ni low thermal expansion alloys), have been commercialized and sold commercially and used as components of the equipment (for example, Non-Patent Document 1).

In the manufacturing process of components made from these Fe-Ni low thermal expansion alloys, welding may be performed for the purpose of assembly or repair. In such cases, if the thermal expansion coefficient of the weld is not equivalent to that of the base material, the properties of the low thermal expansion component cannot be fully demonstrated.

In addition, since Fe-Ni low thermal expansion alloys are prone to hot cracking when solidified and reheated during additional processing, the filler material must be an alloy material that is free of hot cracking.

Conventionally, as alloy materials suitable for welding Fe-Ni based low thermal expansion alloys, proposals have been made regarding welding processing as shown in the following Patent Documents 1 to 3. Patent Document 1 discloses a welding material based on Fe and Ni, containing 0.12 to 0.50% C, 0.5 to 3% Nb, and further containing Mn, Cu, Ti, Al, Mg, Ce, Zr, S, Si, and P at or below a prescribed amount. Patent Document 2 discloses a welding material based on Fe and Ni, containing 0.03 to 0.5% C, 0.7% or less Mn, and 0.05 to 4% [Nb + Zr], and further containing the amounts of Si and S regulated to prescribed amounts or below by the relational expression [Nb + Zr], with P, S, and Al regulated to prescribed amounts or below. Patent Document 3 discloses a welding material based on Fe and Ni, containing 0.08 to 0.30% C,
This document discloses a welding material containing 0.01 to 0.30% Si, 0.10 to 1.0% Mn, 0.05 to 0.50% Ti, and 0.10 to 1.50% Ta, with the contents of P, S, Nb, Cu, Cr, Mo, Al, and O (oxygen) restricted to not more than specified amounts.

All of the above patent documents 1 to 3 aim to prevent high-temperature cracking that occurs during welding by using an Fe-Ni alloy as a base to impart low thermal expansion, and further adding multiple elements from among Nb, Ti, Ta, and Zr and utilizing the action of their carbides.

Japanese Patent Application Publication No. 4-231194 International Publication No. 2000/20160 JP 2003-19593 A

Materia, Vol. 36, No. 11 (1997) Internet <URL: https://www.jstage.jst.go.jp/article/materia1994/36/11/36_11_1080/_pdf Internet: URL: https://www.jstage.jst.go.jp/article/tetsutohagane1955/80/12/80_12_944/_pdf/-char/ja PHYSICS AND APPLICATIONS OF INVAR ALLOYS, P518-537, Maruzen, 1978

As mentioned above, Patent Documents 1 to 3 provide low thermal expansion by using an Fe-Ni alloy as a base, and Patent Documents 2 and 3 state that "it is desirable to use a welding material with a linear expansion coefficient equivalent to that of the base material." However, none of the examples describe the α of the joint including the weld metal. As seen in Non-Patent Documents 2 and 3, it is known that the α of an Fe-Ni low thermal expansion alloy increases when an element other than an Fe-Ni alloy is added to the base. Therefore, in Patent Documents 1 to 3, elements such as C, Nb, Zr, Ti, and Ta are added for the purpose of improving hot cracking resistance, so it is self-evident that the α of the joint is larger than that of the base material, and it is theoretically impossible to achieve the α of the joint with a low thermal expansion equivalent to that of the base material.

Patent Document 1, paragraphs 0023-0025, lists the thermal expansion coefficients of heats No. 13 and No. 14 in the examples, and indicates that they have low thermal expansion close to that of the low thermal expansion alloy of the base material. However, the total amount of C, Mn, and Nb is 2.78% for heat No. 13 and 2.56% for heat No. 14. If we refer to Non-Patent Documents 2 and 3, it is clear that the actual thermal expansion coefficients of heats No. 13 and No. 14 are larger than the values listed in the examples.

An object of the present invention is to provide a welding method that can, when welding an Fe-Ni low thermal expansion alloy as a base metal with a low thermal expansion alloy for welding, extremely reduce the difference in thermal expansion coefficient between the low thermal expansion alloy for welding and the Fe-Ni low thermal expansion alloy as a base metal for welding, even if a required amount of alloying elements for preventing high-temperature cracking during welding is added to the low thermal expansion alloy for welding.

After much research to solve the above problems, the inventors have discovered the following: When the composition of a low thermal expansion alloy for welding used as a filler metal is made by adding the necessary amount of alloy elements effective in preventing hot cracking to the composition of the base metal (e.g., Invar, Super Invar, 42Ni, etc.), the thermal expansion coefficient increases according to the type and amount of alloy elements added. However, by adjusting the alloy composition based on a certain relationship according to the type and amount of alloy elements effective in preventing hot cracking, it is possible to prevent the increase in the thermal expansion coefficient.

The present invention was completed based on the above findings and provides the following means:

A welding method for welding a base material made of an Fe-Ni low thermal expansion alloy with a low thermal expansion alloy for welding , comprising:
The welding base material is Invar, Super Invar, or 42Ni alloy;
The low thermal expansion alloy for welding is
In mass percent,
C: 0.05-0.14%,
Si: 0.1 to 0.3%,
Mn: 0.2 to 0.4%,
Ni: 30 to 40%
Contains
moreover,
When the C content (mass%) is represented as [C], the Nb content (mass%) is represented as [Nb], the Co content (mass%) is represented as [Co], the Co content (mass%) of the welding base metal is represented as [CoM], the Ni content (mass%) is represented as [Ni], and the upper limit temperature T (°C) showing the low thermal expansion of the welding base metal, Invar, Super Invar, or 42Ni alloy, is represented as [T],
Contains Nb so as to satisfy 7.74×[C]≦[Nb]≦1.1%;
Co is contained so as to satisfy [CoM] + (0.8 x [Nb] - 4.494 x [C] + 0.1) / (0.25 - 0.0004 x [T]) ≦ [Co] ≦ [CoM] + (0.8 x [Nb] - 4.494 x [C] + 0.1) / (0.25 - 0.0004 x [T]) + 0.5%;
The Ni equivalent represented by [Ni] + 0.8 × [Co] is in the range of 35.945-0.00025 × [T] + 0.0000375 × [T] ^2.026 -0.5 to 35.945-0.00025 × [T] + 0.0000375 × [T] ^2.026 +0.5%,
The balance is Fe and unavoidable impurities ,
A welding method characterized in that the [T] is 40°C when the welding base metal is Invar, 40°C when the welding base metal is Super Invar, and 375°C when the welding base metal is 42Ni alloy .

According to the present invention, there is provided a welding method which, when welding an Fe-Ni-based low thermal expansion alloy as a base metal with a low thermal expansion alloy for welding, can extremely reduce the difference in thermal expansion coefficient between the low thermal expansion alloy for welding and the Fe-Ni-based low thermal expansion alloy as a base metal for welding, even if a required amount of alloying element for preventing hot cracking during welding is added to the low thermal expansion alloy for welding .

FIG. 4 is a schematic diagram showing a groove shape in an embodiment. FIG. 4 is a diagram showing welding conditions in the examples. FIG. 2 is a diagram showing how to collect evaluation test pieces in the examples.

This embodiment will be described in detail below.
Unless otherwise specified, percentages for components are mass %, and the thermal expansion coefficient (α) is the average thermal expansion coefficient (ppm/°C) between 10°C and T°C.

The low thermal expansion alloy for welding of the present invention is used to weld a welding base material made of a Ni-Fe low thermal expansion alloy. Examples of the Ni-Fe low thermal expansion alloy that constitutes the welding base material include Invar, Super Invar, and 42Ni alloy, which can obtain the desired low thermal expansion characteristics within a specified temperature range. The low thermal expansion alloy for welding of the present invention is specified corresponding to the Ni-Fe low thermal expansion alloy of these welding base materials.

Next, the reason for the limitation will be explained.
・C: 0.05-0.14%
As described later, C is an element that, when added together with Nb, forms an appropriate amount of NbC to prevent hot cracking during welding by adjusting the amount added. However, if the C content is less than 0.05%, the effect is insufficient, and if it exceeds 0.14%, the decrease in weldability cannot be ignored. Therefore, the C content is set to the range of 0.05 to 0.14%.

・Si: 0.1-0.3%
Silicon is an element added for the purpose of deoxidizing the low thermal expansion alloy for welding of the present invention, which is manufactured as a filler metal, and improving the fluidity of the alloy. However, if the content is less than 0.1%, the effect is insufficient. If the content exceeds 0.3%, the increase in the thermal expansion coefficient cannot be ignored, similar to the case of C. Therefore, the Si content is set to 0.1 to 0.3%.

・Mn: 0.2-0.4%
Mn is an element effective in deoxidizing the low thermal expansion alloy for welding of the present invention, which is manufactured as a filler metal. However, if the Mn content is less than 0.2%, the effect is small, and if the Mn content exceeds 0.4%, Therefore, the Mn content is set in the range of 0.2 to 0.4%.

・Ni: 30-40%
Ni, together with Co, is an important element that determines α. By adjusting the Ni equivalent and Co amount described later, the increase in α caused by alloy additions for the purpose of preventing cracking during welding can be compensated for, and Fe - It is possible to make α equivalent to that of the welding base material (hereinafter simply referred to as base material) made of Ni-based low thermal expansion alloy. However, when Ni is less than 30% or exceeds 40%, α cannot be made equivalent to that of the base material. Therefore, the Ni content is set in the range of 30 to 40%.

・Nb: 7.74×[C] ~ 1.1%
As mentioned above, Nb is an element that forms NbC together with C to prevent hot cracking during welding. However, if Nb is dissolved in the base, the effect of preventing weld cracking cannot be obtained, and instead, α increases. Therefore, it is necessary to disperse Nb in the structure in the form of NbC. When the content of C is expressed as [C], if the content of Nb is less than 7.74 × [C], the solid-solubilized Nb If the Nb content is too high, α will increase, and if it exceeds 1.1%, the NbC content will become excessive and the deterioration of weldability will become unnegligible. Therefore, the Nb content is set to the range of 7.74 × [C] to 1.1%. do.

・Co: [CoM] + (0.8 x [Nb] - 4.494 x [C] + 0.1) / (0.25 - 0.0004 x [T]) ~ [CoM] + (0.8 ×[Nb]-4.494×[C]+0.1)/(0.25-0.0004×[T])+0.5%
Co, along with Ni, is an important element that determines α. It is an essential element for compensating for the increase in α that accompanies alloy additions to prevent cracking during welding, and for making α equivalent to that of the base material. That is, in order to prevent cracking, the Co/Ni ratio in the Ni equivalent, which will be described later, is increased according to the type and amount of the alloy added, thereby making the α value of the alloy low. However, the Co content is related to the Co content of the base material and the temperature range in which the alloy exhibits low thermal expansion, and the Co content (mass%) of the base material is defined as [CoM] and the C content as [C]. The content of Nb is [Nb], and the upper limit temperature T (°C) at which the Fe-Ni low thermal expansion alloy of the welding base metal exhibits the desired low thermal expansion property is [T]. Less than (0.8 × [Nb] - 4.494 × [C] + 0.1) / (0.25 - 0.0004 × [T]), or [CoM] + (0.8 × [Nb] - If it exceeds 4.494 × [C] + 0.1)/(0.25-0.0004 × [T]) + 0.5, α cannot be made equal to that of the base material. Therefore, the Co content is [CoM] + (0.8 × [Nb] - 4.494 × [C] + 0.1) / (0.25 - 0.0004 × [T]) ~ [CoM] + ( The range is 0.8 x [Nb] - 4.494 x [C] + 0.1) / (0.25 - 0.0004 x [T]) + 0.5%.

・Ni equivalent: 35.945-0.00025×[T]+0.0000375×[T] ^2.026 -0.5 to 35.945-0.00025×[T]+0.0000375×[T] ^{2. 026} +0.5%
When the Ni content (mass%) is [Ni] and the Co content (mass%) is [Co], the Ni equivalent is expressed as [Ni] + 0.8 × [Co]. The alloy has low thermal expansion coefficient. There is a certain relationship with the temperature range in which the alloy shows its properties, and the Ni equivalent can be adjusted to reduce the alpha of the alloy. The Ni equivalent is 35.945 - 0.00025 x [T] + 0.0000375 x [T] ^{2 ． 026} -0.5～35.945-0.00025×[T]+0.0000375×[T] ^2.026 +0.5% (where [T] is the Fe- content of the weld base metal as above) In the range of the upper limit temperature T (℃) at which the Ni-based low thermal expansion alloy exhibits the desired low thermal expansion property, α between 10 and T℃ becomes significantly small. However, when the Ni equivalent is outside this range, Therefore, it becomes difficult to obtain the desired low thermal expansion. Therefore, the Ni equivalent is 35.945-0.00025 x [T] + 0.0000375 x [T] ^2.026 -0.5 to 35.945-0.00025 x [T] + 0.0000375 x [T] ² The range shall be ^.026 +0.5%.

In the present invention, the remainder other than C, Si, Mn, Ni, Co, and Nb is Fe and unavoidable impurities.

The following describes an embodiment of the present invention.

Alloys having the chemical compositions shown in Table 1 were melted in air in a high-frequency induction furnace and cast at 1600°C into _CO2 silica sand molds to produce ingots measuring φ127 mm x 270 mm.

The ingot was heated in a 1200°C heating furnace and then hot forged with an air drop hammer to produce a rolled material measuring 40 mm x 1400 mm.

The rolled material was heated in a 1150°C heating furnace and first rolled to 22 mm square, then second rolled to produce a 9.6 mm diameter wire, which was then cold drawn to produce a 1.6 mm diameter wire.

The base metals No. 31 (Invar), No. 32 (Super Invar), and No. 33 (42Ni alloy) in Table 1 were processed with a U-shaped groove as shown in Figure 1, and welded under the welding conditions shown in Figure 2 using wires No. 1 to 7 of the alloys of the present invention corresponding to each base metal and wires No. 11 to 21 of the comparative alloys as filler metals to produce welded joints. Thermal expansion measurement test pieces of φ6 mm x 50 mm and welding defect observation test pieces of 3 mm x 10 mm were cut out from the joints as shown in Figure 3, and evaluation tests were performed.

The evaluation test was carried out as follows. The thermal expansion coefficient was measured using a thermal dilatometer (DIL402C manufactured by NETZSCH) to measure the thermal expansion between 10 and T°C, and the average thermal expansion coefficient α was calculated. When the base material was Invar or 42Ni alloy, the absolute value of the difference between [α of the welded part] and [α of the base material] was ±10% or less of [α of the base material], which was deemed to be acceptable. When the base material was Super Invar alloy, α was extremely small and there was also negative expansion, so the absolute value of [α of the welded part] was 0.15 ppm/°C or less, which was deemed to be acceptable. For weld defects, the test pieces were observed at 50x magnification using an optical stereo microscope to check for the presence or absence of cracks. The evaluation criteria were that no cracks were present and that even one crack was present and deemed to be unacceptable.

As shown in Table 1, the average thermal expansion coefficient α between 10 and T°C of the alloys of the present invention Nos. 1 to 7 all had values equivalent to those of the corresponding base metals Nos. 31 to 33, and no welding defects were observed.

On the other hand, in the comparative alloys No. 11, 12, 14 to 17, and 19, the necessary amount of C and Nb was added to prevent welding defects, as in the alloys of the present invention, and no welding defects were observed. However, in No. 11 and 16, the Ni equivalent was above the upper limit and the Co equivalent was below the lower limit, in No. 12 and 17, the Ni equivalent was below the lower limit and the Co equivalent was above the upper limit, in No. 15, the Si and Mn equivalents were above the upper limit, and in No. 14 and 19, the Nb content relative to the C content was outside the range of the present invention, so that α increased compared to the base material, and none of them met the judgment criteria. In addition, in the comparative alloys No. 13, 18, and 20, C or both C and Nb were below the lower limit, and in No. 21, Nb was above the upper limit, so hot cracking occurred. Furthermore, in No. 21, the difference with the α of the target base material exceeded 10%.

Claims (1)

A welding method for welding a base material made of an Fe-Ni low thermal expansion alloy with a low thermal expansion alloy for welding , comprising:
The welding base material is Invar, Super Invar, or 42Ni alloy;
The low thermal expansion alloy for welding is
In mass percent,
C: 0.05-0.14%,
Si: 0.1 to 0.3%,
Mn: 0.2 to 0.4%,
Ni: 30 to 40%
Contains
moreover,
When the C content (mass%) is represented as [C], the Nb content (mass%) is represented as [Nb], the Co content (mass%) is represented as [Co], the Co content (mass%) of the welding base metal is represented as [CoM], the Ni content (mass%) is represented as [Ni], and the upper limit temperature T (°C) showing the low thermal expansion of the welding base metal, Invar, Super Invar, or 42Ni alloy, is represented as [T],
Contains Nb so as to satisfy 7.74×[C]≦[Nb]≦1.1%;
Co is contained so as to satisfy [CoM] + (0.8 x [Nb] - 4.494 x [C] + 0.1) / (0.25 - 0.0004 x [T]) ≦ [Co] ≦ [CoM] + (0.8 x [Nb] - 4.494 x [C] + 0.1) / (0.25 - 0.0004 x [T]) + 0.5%;
The Ni equivalent represented by [Ni] + 0.8 × [Co] is in the range of 35.945-0.00025 × [T] + 0.0000375 × [T] ^2.026 -0.5 to 35.945-0.00025 × [T] + 0.0000375 × [T] ^2.026 +0.5%,
The balance is Fe and unavoidable impurities ,
A welding method characterized in that the [T] is 40°C when the welding base metal is Invar, 40°C when the welding base metal is Super Invar, and 375°C when the welding base metal is 42Ni alloy .

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