JPS60133996A - Welding material having excellent creep rupture ductility - Google Patents

Abstract

PURPOSE:To obtain a welding material having excellent creep rupture ductility and good weldability with a specifically composed welding mterial for a super heat resistant alloy for an intermediate heat exchanger of a multi-purpose high- temp. gas experimenting furnace by limiting the copper in unavoidable impurities. CONSTITUTION:A welding material of the above-described super heat resistan alloy (''Hastelloy X'') is formed of the compsn. contg., by weight %, 0.04-0.15 C, 20.0-25.0 Cr, 17.0-20.0 Fe, 8.0-10.0 Mo, 0.2-1.0 W, 0.4-1.5 Mn, 0.05-0.5 Si and 0.5-2.5 Co, contg. >=1 kind among <=0.02 B, <=0.05 Zr, <=0.02 Mg, <=0.02 Ca and <=0.02 rare earth elements and consisting of the balance ni and unavoidable impurities. The contents of Al, Ti, Cu as unavoidable impurities are limited to <=0.1 Al, <=0.02 Ti and <=0.05 Cn. If the content of Cu is limited to <=0.05wt% in such a way, the creep rupture ductility is improved and the deterioration in weldability owing to addition of B, Zr and rare earth elements is obviated as well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welding material with excellent creep rupture ductility, and particularly to a welding material suitable for welding an intermediate heat exchanger in a multi-purpose high-temperature gas experimental reactor.

Currently, the development of a multipurpose high-temperature gas experimental reactor is being carried out mainly at the Japan Atomic Energy Research Institute. This experimental reactor is equipped with an intermediate heat exchanger (hereinafter referred to as IHX) that transfers heat from high-temperature helium gas (approximately 100°C) circulating in the primary system to another heat medium, and the high-temperature section of the IHX It is planned to use a super heat-resistant alloy (hereinafter abbreviated as Hastelloy X) represented by the trade name "Hastelloy X" as the material.

The main reason why Hastelloy
2. It exhibits excellent corrosion resistance in a helium gas atmosphere containing a large amount of impurity residue such as CH4. That is,
Since Hastelloy As a result, it has been confirmed that grain boundary corrosion does not occur even in the helium gas atmosphere, which has a very low oxidation potential, and that a stable spinel-based oxide film of MnCr2O+ is formed on the surface. In addition, regarding Hastelloy

However, the welding materials that are essential for manufacturing IHX have a fairly serious problem in terms of creep ductility, but the reality is that improvements have not been successful and there have not been many studies. Under these circumstances, reports have been attracting attention that the creep rupture ductility, which is a drawback of conventional welding materials, can be significantly improved by adding B, Zr, Y, etc. singly or in combination, but weldability (e.g. (hot cracking resistance)
Conventional welding materials were far superior in this respect.

The present invention was made in view of the above-mentioned circumstances, and was made in an attempt to obtain a welding material for Hastelloy X that has excellent creep rupture ductility and good weldability.

That is, in the present invention, C: O, 04 to 0.15% by weight, Cr: 20. O~25.0% by weight, Fe: 17
．． O~20.0% by weight, Mo: 8. O~10.0% by weight
, W:O, 2-1.0% by weight, Mn:O, 4-1.5% by weight, Si:O, 05-0.5% by weight, CO:O, 5-2.5% by weight. and contains: B: O, 0.02% by weight or less, Zr: O, 0.05% by weight or less, MU: O, 0.02% by weight or less, Ca: 0.02% by weight or less, rare earth elements: O, 0.2% by weight or less. This is a welding material with excellent creep rupture ductility, characterized by the following:

In order to investigate the cause of the low creep rupture ductility of conventional welding materials for Hastelloy .

When each element was investigated by line analysis, paying attention to the presence or absence of enrichment of 5ietc), enrichment at the dendrite boundary was observed only for Cu.

Therefore, we decided to change the GO content to the conventional welding material (0.1% by weight).
) As a result of manufacturing and considering welding material with less than
By setting Cul to 0.05% by weight, the creep rupture ductility is improved by more than one order of magnitude, and by further increasing it to 0.01% by weight, the creep rupture ductility is improved to 2/3 of that of the base material (Hastelloy X). This discovery led to the above-mentioned present invention.

In the present invention, the reason why the range of components other than Cu is limited is as follows.

[C]: 0.04 to 0.15% by weight 0°04% from the viewpoint of strengthening the alloy matrix and stabilizing the structure
On the other hand, if it exceeds 0.15%, difficulties arise in plastic working.

[Cr]: 20. O ~ 25.0% by weight If it is less than 20%, stable oxidation resistance at high temperatures cannot be ensured;
This is because if it exceeds 5%, mechanical strength and workability deteriorate.

[Fe]: 17.0 to 20.0% by weight To improve hot workability and cold workability, a content of 17% or more is required, and on the other hand, if it exceeds 20%, oxidation resistance deteriorates. It is.

[Mo]:8. O to 10% by weight This is because it is necessary to limit the content to the above range in order to achieve both high temperature strength and plastic workability.

[W]: O, 2 to i, o-type mouth% W improves high temperature strength like MO, but its effect is not sufficient when it is less than 0°2%, and even more so when it exceeds 1%. This is because there is no effect.

[Mn]: The content necessary to generate MnCr204, which contributes to corrosion resistance in a low oxidation potential atmosphere, is 0.4% or more, and if it exceeds 1.5%, high temperature workability will deteriorate. be.

[31]: O, 0.05~0.5% by weight It is known that when S1 coexists with Mn, peeling of the oxide film is suppressed, and its optimum content is 0.05~0.5% by weight.
%.

[CO'l: 0.5 to 2.5% by weight CO improves high temperature strength like Mo, but 0.5%
This is because if the content is less than 2.5%, the effect will not be sufficient, and if the content exceeds 2.5%, no further effect will be obtained.

[B, Zr, Mu, Ca, rare earth elements] Some of these components have the effect of improving various properties in trace amounts, but in any case, B:O,02%, This is because if the content exceeds Zr: O, 05% by weight, fvlg: O, 02% by weight, Ca: 0.02% by weight, and rare earth element: 0.02% by weight, hot workability and weldability are impaired.

[AI]: O, 1ii 1% or less It is effective as a deoxidizing agent, but if it remains, there is a concern about intergranular corrosion.

[Ti]:O, 0.2% by weight or less The reason for the limitation is the same as in the case of A1, but it is because a stricter limitation is required.

The present invention will be explained in detail below.

Examples 1 to 3 Raw materials were blended to have the final chemical components shown in Table 1, and melted in a vacuum high-frequency induction furnace.

1. After homogenizing the crushed ingot, the ingot was forged and rolled into a plate with a thickness of 1.5#l, which was further cut into 1.5M square pieces to form a welding rod. Manufactured.

Comparative Example Raw materials were mixed to have the final chemical composition (same as conventional welding materials) shown in Table 1, and then a 1.5M welding rod was produced in the same manner as in Examples 1 to 3. did.

The following same tests were conducted on each of the welding rods produced in Examples 1 to 3 and Comparative Example.

First, using the above welding rod, a steel piece of Hastelloy X was manually TIG welded (Tungusten Inert Qas
Welding) by welding 14#IφX 90 gun l
A full weld test piece was fabricated. A creep rupture test was conducted on these test pieces under the conditions of 950°C The results shown are as follows.From these results, even in the welding material of Example 1 with a Cu content of 0.05% by weight,
It can be seen that the creep rupture elongation is improved by more than one order of magnitude compared to conventional weld metal.

In addition, even better results were obtained in Example 2 and Example 3 where the Cu content was 0.03% and 0.01%, respectively. In particular, in Example 3, 2/3 of the creep rupture ductility of the base metal It can be seen that it has been improved.

As detailed above, according to the present invention, it is possible to provide a welding material with excellent creep rupture ductility, particularly a welding material suitable for welding an intermediate heat exchanger in a multi-purpose high-temperature gas experimental reactor.

[Brief explanation of the drawing]

The accompanying drawings are diagrams showing the results of comparative tests conducted on welding materials according to embodiments of the present invention and conventional welding materials. Applicant Sub-Agent Patent Attorney Takehiko Suzue

Claims (1)

[Claims] C: O, 04 to 0.15% by weight, Cr: 20. O~25.0% by weight, Fe: 17
．． O~20.0% by weight, Mo: 8. O~10.0% by weight
, W: O, 2-1.0% by weight, Mn: O, 4-1.5% by weight, Si: O, 05-0.5% by weight, CO: O, 5-2.5% by weight Contains the following components: B: 0.02% by weight or less, Zr: O, 05% by weight or less, Mu: 0.02% by weight or less, Ca: 0.02% by weight or less, Rare earth element: 0.02% by weight % or less, with the remainder consisting of Nb and unavoidable impurities. A welding material having excellent creep rupture ductility, characterized in that O: 1% by weight or less, Ti: O: less than 0.02% by weight, and Cu: O: 0.5% by weight or less.