JP2001058283A - Laser beam welding method for stainless steel to carbon steel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To implement the constantly excellent welding without generating any martensitic transformation and incomplete fusion of a weld metal. SOLUTION: In a method for welding a stainless steel to a surface of a carbon steel using the YAG laser, the welding heat input Q (kJ/cm) is equal to P/Vt×60 [where, P is the laser beam output (kW), and Vt is the welding speed (cm/min)], and when the wire feed length W (cm/min) per unit welding length is equal to Vw/Vt, [where, Vw is the wire feed quantity (cm/min), and Vt is the welding speed (cm/min)], the welding is implemented with the wire feed length W per unit welding length in a range S between W≈0.22Q+0.75 and W≈0.40Q+0.50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laser welding stainless steel to carbon steel.

[0002]

2. Description of the Related Art As a means of surface modification of carbon steel, there is clad welding of stainless steel welding material (hereinafter referred to as stainless steel material). The clad welding method includes electroslag welding and explosion welding, but when used for on-site repair welding, TIG welding or laser welding using a wire feed type combined with a YAG laser oscillator is effective. .

[0003] When a stainless steel material is welded to carbon steel, it is a dissimilar material welding, so the following two problems arise. That is, a continuous and smooth weld bead without defective fusion can be formed, and the weld metal does not undergo martensitic transformation due to dilution with the base material.

[0004]

For example, considering the case where a 316 type austenitic stainless steel material having excellent corrosion resistance against local corrosion is clad-welded to carbon steel, in TIG welding where the dilution with the base metal is large, The first layer is welded using a 309 type stainless material, and then a multi-layer welding is performed on the first layer using a 316 type stainless material.

[0005] However, in the case of TIG welding, a large welding heat input is applied to the portion concerned. Therefore, when this technique is applied to a flange sealing surface or the like, the flange is deformed and the bolt cannot be tightened. There is a possibility that a problem that impairs the performance of the device may occur.

[0006] On the other hand, laser welding is a very effective method since the welding heat input is small and the deformation of the base material is small.

However, even in laser welding, unless the laser output, welding speed, and wire feed rate are properly controlled,
The weld metal is diluted to cause martensitic transformation,
Alternatively, there is a problem that poor fusion occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is directed to a method for laser welding stainless steel to carbon steel so that good welding can always be performed without causing martensitic transformation or poor fusion of the weld metal. It is intended to provide.

[0009]

According to the first aspect of the present invention,
A method of welding a stainless steel material to a carbon steel surface using a YAG laser, wherein a welding heat input Q (kJ / cm) is obtained.

## EQU3 ## Q = P / Vt × 60 P: laser output (kW) Vt: welding speed (cm / min), and wire feed length W (cm) per unit welding length
/ Min)

W = Vw / Vt Vw: Wire feed amount (cm / min) Vt: Welding speed (cm / min), and the wire feed length W per unit welding length
Is greater than W ≒ 0.22Q + 0.75 and W ≒ 0.4
Laser welding of stainless steel to carbon steel, characterized in that welding is performed in an appropriate range smaller than 0Q + 0.50,
It is related to.

The invention according to claim 2 is the first layer first layer.
The wire feed length W per welding unit length of the pass is expressed as W ≒
Larger than 0.55Q-0.34, W ≒ 0.65Q-
2. The method according to claim 1, wherein the welding is performed in an appropriate range smaller than 0.34.
Welding is performed within the appropriate range described.

According to the present invention, by specifying an appropriate range in the relationship between the welding heat input and the wire feed length per unit length of the welding, the welding heat input and the welding input can be performed in an appropriate range. When the relationship of the wire feed length per unit welding length is automatically controlled, a stainless steel material can be satisfactorily welded to carbon steel without causing martensitic transformation or poor melting.

Further, by performing welding under an appropriate range of welding conditions, the dilution ratio of the weld metal can be controlled to be low, so that even a single layer can form a clad layer having sufficient corrosion resistance. Therefore, deformation due to welding of the base material can be reduced, and welding material can be saved and the construction period can be shortened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

The present inventors conducted various experiments and investigated the relationship between laser output, welding speed, and wire feed rate in the case where a stainless steel material was clad-welded to carbon steel using the YAG laser welding method. Was done.

From the relationship between the laser output P and the welding speed Vt,
The welding heat input Q (kJ / cm) is

Q = P / Vt × 60 P: laser output (kW) Vt: welding speed (cm / min)

Further, based on the relationship between the wire feed amount Vw and the welding speed Vt, the wire feed length W (cm) per unit welding length.
/ Min) is

W = Vw / Vt Vw: wire feed rate (cm / min) Vt: welding speed (cm / min)

When the relationship between the welding heat input Q and the wire feed length W per unit welding length was examined, the results shown in FIG. 1 were obtained. FIG. 1 shows a case where a 316 type stainless material is clad-welded to carbon steel.
Line A shows W = 0.216Q + 0.750;
Line B indicates W = 0.401Q + 0.501.

When the 304 type stainless material was clad-welded to carbon steel, substantially the same results as above were obtained.

The line A in FIG. 1 shows the lower limit at which the martensitic transformation occurs when the value of the wire feed length W per welding unit length is smaller than the line A, and the line B shows the line B When the value of the wire feed length W per unit length of welding is larger, the upper limit value at which poor melting occurs is shown.

Therefore, between the line A and the line B in FIG.
= 0.216Q + 0.750 and W = 0.401Q +
The range between 0.501 and 0.501 is the appropriate range S. For example, if welding is performed under the standard condition of the point X within the appropriate range S, good clad welding without martensite transformation or poor melting can be performed.

Thus, in the relationship between the welding heat input Q and the wire feed length W per unit welding length, the appropriate range S
When the relationship between the welding heat input Q and the wire feed length W per welding unit length is automatically controlled so that welding is performed within the appropriate range S, the stainless steel material for carbon steel is Good clad welding can be stably performed.

Further, the relationship between the welding heat input Q and the wire feeding length W per unit welding length during the welding of the first layer and the first pass to the flat plate was investigated. As shown, different results from FIG. 1 were obtained.

The line C in FIG. 2 indicates that W = 0.545Q-0.3
38, and line D is W = 0.645Q-0.3
38 is shown.

The line C in FIG. 2 shows the lower limit at which martensitic transformation occurs when the value of the wire feed length W per unit welding length is smaller than that of the line C, and the line D shows the line D When the value of the wire feed length W per unit length of welding is larger, the upper limit value at which poor melting occurs is shown.

Therefore, between the line C and the line D in FIG.
= 0.545Q-0.338 and W = 0.645Q-
The appropriate range S ′ is between 0.338. Therefore, when performing the first-layer first-pass welding, for example, if the welding is performed under the standard condition of the point Y within the appropriate range S ′, the martensitic transformation is performed. And good clad welding without causing poor melting.

Further, one layer 1 in the appropriate range S 'shown in FIG.
After the welding of the pass is performed, the welding may be continued under the welding conditions in the appropriate range S shown in FIG.

As described above, by performing welding under the welding conditions in the appropriate ranges S and S 'shown in FIGS. 1 and 2, the dilution ratio of the weld metal can be controlled to be low. For this reason,
Even a single layer can form a clad layer having sufficient corrosion resistance, and sound welding can be performed even when carbon steel is used with a 316 type stainless steel material from the first layer.

As described above, the clad layer can be formed by one-layer welding, so that deformation of the base material due to welding can be reduced. In addition, it is possible to save welding materials and shorten the construction period.

[0029]

According to the present invention, the proper range is specified in the relationship between the heat input of the welding and the wire feed length per unit length of the welding so that the welding input can be performed in the proper range. When the relationship between the heat and the wire feed length per welding unit length is automatically controlled, there is an effect that a stainless steel material can be satisfactorily welded to carbon steel without causing martensitic transformation or poor melting.

Further, by performing welding under an appropriate range of welding conditions, the dilution ratio of the weld metal can be controlled to be low, so that even one layer can form a clad layer having sufficient corrosion resistance. Therefore, there is an effect that deformation due to welding of the base material can be reduced, and welding material can be saved and a construction period can be shortened.

[Brief description of the drawings]

FIG. 1 is a diagram showing an appropriate range of a laser welding method for stainless steel to carbon steel according to the present invention.

FIG. 2 is a diagram showing an appropriate range when welding the first pass of the first layer.

[Explanation of symbols]

 S, S 'proper range

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4E068 BA06 BB02 CA02 CA13 CA15 CB05 DB01

Claims (2)

[Claims] 1. A method for welding a stainless steel material to a carbon steel surface using a YAG laser, comprising the steps of:
Q = P / Vt × 60 P: laser output (kW) Vt: welding speed (cm / min), and wire feed length W (cm) per unit welding length
/ Min) is: W = Vw / Vt Vw: wire feed rate (cm / min) Vt: welding speed (cm / min), wire feed length W per welding unit length
Is greater than W ≒ 0.22Q + 0.75 and W ≒ 0.4
A method for laser welding stainless steel to carbon steel, characterized in that welding is performed in an appropriate range smaller than 0Q + 0.50. 2. An appropriate wire feed length W per unit welding length of the first pass of the first layer is larger than WＱ0.55Q-0.34 and smaller than W ≒ 0.65Q-0.34. A method for laser welding stainless steel to carbon steel, characterized in that welding is performed within a range, and thereafter, welding is performed within an appropriate range.