JPS605668B2 - Non-magnetic steel with good electron beam weldability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-magnetic steel that has good weldability, and particularly to a non-magnetic steel that can maintain low magnetic permeability even when subjected to electron beam welding.

Non-magnetic steel with low magnetic permeability is used for structural members placed in high magnetic fields such as nuclear fusion reactors, but these steel plates have a thickness of about 60 to 180 mm, and welding requires coating. This can be done by arc welding, TIG welding, MIG welding, or submerged arc welding.

However, these welding methods are not only time consuming and economically problematic as they require a large amount of welding material, but with conventional non-magnetic steel, a large amount of ferrite is generated in the weld.
Magnetic permeability increases significantly. As an alternative to the above-mentioned welding method, an electron beam welding method (hereinafter referred to as TEBW method) is known, which has a high welding speed and does not require a welding material. However, when this is applied to conventional non-magnetic steel, the E
Since the BW method is carried out in a high vacuum atmosphere, N in the steel is released, blowholes are generated in the weld, the N content of the weld decreases, and a large amount of ferrite is generated, resulting in a decrease in magnetic permeability. will rise. Also, a large amount of spatter is generated during welding, resulting in defects in the bead shape. This invention is
In order to eliminate the above-mentioned drawbacks of conventional non-magnetic steel, the chemical composition of the steel was adjusted so that the magnetic permeability of the base metal was 1.0 or less and the E
We propose a non-magnetic steel that has a welded area of 1.20 or less when welded using the BW method.

This invention is based on CO. 15% or less, Sil. 00% or less,
Mn 2.00% or less, Nj 9.0-13.0%, Crl
o. 0-20.0%, NO. 05% or less, SoIAIO
．． 03 to 0.10%, the balance substantially consisting of Fe, or in addition to the above components, 0.1 to 0.6% of Ti,
Nb0.2-0.9%, VO. Non-magnetic steel containing one or more of 1 to 0.6%, with magnetic permeability of 1.04 or less at the base and 1.20 or less at the welded part, and electron beam welded. It is characterized by good sex.

The reason for limiting the chemical components in this invention is as follows.

C is an austenite stabilizing element and is effective in lowering magnetic permeability, but if it exceeds 0.15%, carbides tend to precipitate at grain boundaries and deteriorate mechanical properties.

Further, after melting, it combines with oxygen in the steel to generate CO gas, which causes welding defects, and also causes hot cracking due to the effects of welding heat, so it must be kept at 0.15% or less. Si
is necessary for deoxidizing steel, but adding more than 1.00% saturates the deoxidizing effect and is not economical.

Mn is an austenite stabilizing element and is effective in lowering magnetic permeability, but if added in large amounts, it becomes difficult to melt and also significantly deteriorates machinability and drilling properties, so 2.0%
It is desirable to do the following.

Ni is an austenite stabilizing element and is effective in lowering magnetic permeability, but if it is less than 9.0%, the magnetic permeability cannot be reduced below the required range. Furthermore, even if the content exceeds 13%, the magnetic permeability will no longer decrease. Although Cr has a small stabilizing force on austenite, it reduces magnetic permeability, but this effect is not sufficient at 10.0%.

If it exceeds 20.0%, ferrite is generated and magnetic permeability increases.

N' is an austenite stabilizing element and is very effective in lowering magnetic permeability, but if it is contained in a large amount, N2 in EBW.
The content should be 0.05% or less because gas is generated and causes spatter, blowholes, and bead defects.

AI is necessary for deoxidizing steel and is effective in preventing blowholes caused by 02 gas or deterioration of EBW properties such as poor bead shape, but if it is less than 0.03%, deoxidation is insufficient. Since this cannot be done, the EBW properties will not improve.

Moreover, when it exceeds 0.10%, the deoxidizing effect is saturated and the number of inclusions in the steel increases significantly. Ti, Nb, and V have strong bonding strength with 02 and N2 in steel, fixing 02 and N2 and forming E
Although it is effective for improving BW properties, Tio. 6%, N
bo. 9%, VO. Above the upper limit of 6%, the effect is saturation and the permeability of the base metal and weld increases.

In addition, if Ti, Nb, and V are all below the lower limit, O2, N in steel
2 cannot be fixed sufficiently, resulting in blowholes and spatter. Furthermore, if Nb exceeds the upper limit of 0.9%, cracks will occur during hot working, and if V exceeds the upper limit of 0.6%, low melting point compounds will be produced, reducing hot workability. Moreover, the reason why the magnetic permeability of the mother village is set to 1.0 S or less is to make the base material completely austenite since it will be used in a high magnetic field.

However, if the weld is made completely austenite, hot cracking will occur.In order to prevent hot cracking and lower the magnetic permeability of the weld, the amount of ferrite in the weld should be 5% or less, and the magnetic permeability should be 1.20 or less. It is better to suppress it.Next,
Examples of this invention will be described. Steels A to F according to the present invention and conventional steels G to 1 for comparison, whose chemical compositions are shown in Table 1, were melted and tested for mechanical properties and magnetic permeability. Shown in the table. We also show the results of making thick plates of each type of steel with a thickness of 6 ridges, welding them using the EBW method, and investigating the magnetic permeability and EBW weldability of the welded parts. The cross sections of the welded parts of steels A, C, J, and K are shown in Figure 1 a, b, c, and d, respectively. Table 1 Chemical Composition Association Table 2 From the above results, it can be seen that the steel according to the present invention has a magnetic permeability of 1.20 or less at the welded portion, and the magnetic permeability does not increase significantly due to welding.

Also, as can be seen from Fig. 1, steels A and C according to the present invention
(Fig. 1 a, b) have sufficient penetration and a clean weld, whereas conventional steels J and K (Fig. 1 c, d) have blowholes and cannot be completely welded. I understand that. Similarly, all other conventional steels had poor EBW weldability.

[Brief explanation of drawings]

FIG. 1 is a drawing showing a cross section of a welded portion of this invention steel and a conventional steel. Figure 1

Claims (1)

[Claims] 1 C0.15% or less, Si 1.00% or less, Mn2.
00% or less, Ni9.0~13.0%, Cr10.0~
20.0%, N0.05% or less, solAl0.03~
0.10%, the remainder substantially consists of Fe, and the magnetic permeability is 1.
Non-magnetic steel with good electron beam weldability at 02 or less. 2 C0.15% or less, Si1.00% or less, Mn2.
00% or less, Ni9.0~13.0%, Cr10.0~
20.0%, N0.05% or less, solAl0.03~
0.10%, further Ti0.1-0.6%, Nb0.2
~0.9%, V0.1~0.6%, the remainder is substantially Fe, and the magnetic permeability is 1.
Non-magnetic steel with good electron beam weldability at 02 or less.