JP2017148858A - Laser welded section steel made of stainless steel and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser welded section steel made of stainless steel which comprises a corner joint part, suppresses occurrence of temper color on a flange material surface, and has a high corrosion resistance and an excellent appearance.SOLUTION: A corner welded section steel made of stainless steel comprises: a laser welded joint part between a web material and a flange material, among surfaces of flange material of which a rear surface with respect to the welded part has a color difference ΔEbased on JIS Z 8730 equal to or less than 50 measured immediately after welding, and a maximum strain amount in a height direction of the flange material equal to or less than 0.2 mm. The welded section steel is made using a laser welding method with a laser beam emission as a welding method to be applied thereto, in which a temperature of the surface of the flange material being the rear surface of the welded part is controlled to be lower than 200°C during a period from the start to the end of welding.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a welded shape steel in which a corner joint portion or a T-shaped joint portion is formed by laser welding using stainless steel as a material and laser light as a heat source.

In recent years, as a method of manufacturing a shape steel such as a C-shaped steel used for a beam or the like constituting a building frame, a laser for irradiating a laser beam to a corner joint formed by two members of a flange material and a web material Welding methods are being considered.
For example, as can be seen in Patent Document 1, a groove having a certain angle is provided between the flange material and the web material, and the laser beam is irradiated at an angle parallel to the abutting surface.
In this method, the penetrating laser beam does not damage the surface of the member, but it is efficient because heating forms an oxide film on the surface of the flange material and web material around the weld and it is necessary to remove it. Cannot be manufactured.

In addition, among these welded steels, stainless steel with extremely high corrosion resistance is used as a bridge, road material, and building member in the beach area as seen in Patent Document 2 so that it is maintenance-free. Are considered.
In Patent Document 2, laser welding is applied for the purpose of suppressing deformation that occurs when welding stainless steel and requiring little correction.
However, when laser welding is performed on stainless steel in the atmosphere, an oxide film called a temper color is generated on the surface of the plate material corresponding to the vicinity of the weld or the back surface of the weld.

Japanese Utility Model Laid-Open No. 5-18783 Japanese Patent Laid-Open No. 11-123575

Since this temper color is a chromium oxide, the amount of chromium in the stainless steel is reduced, so that the corrosion resistance is lowered and the appearance is also deteriorated, and it is necessary to remove the temper color after welding.
Since the vicinity of the weld is rarely exposed to the appearance, removing the temper color with a brush or the like is not a problem, but the flange material surface exposed to the appearance is a polishing process that further reduces the polishing eyes from which the temper color has been removed. Is required, and productivity becomes very low.

In addition, laser welding has a relatively small heating area, so thermal deformation is relatively small, but the flange material and web material are fixed and welded so as not to cause positional displacement, so the surface of the flange material is likely to be distorted, This deteriorates the appearance of the flange material surface.
The problem of distortion of these temper collars and member surfaces occurs in any shape steel having a corner joint portion, shape steel having a T-shaped joint portion, and shape steel having both a corner joint portion and a T-shaped joint portion. Is.

  The present invention has been devised to solve such problems, and a laser comprising a stainless steel as a raw material and having a corner joint portion or a T-shaped joint portion, and both a corner joint portion and a T-shaped joint portion. An object of the present invention is to provide a laser welded shape steel which is a welded shape steel and has excellent corrosion resistance and appearance by suppressing the temper color and distortion on the surface of the flange material generated during welding.

In order to achieve the object, the laser welded shape steel of the present invention has a flange joint and a web material made of stainless steel plates as a corner joint portion or a T-joint portion, and both a corner joint portion and a T-joint portion. The color difference ΔE ^* based on JIS Z 8730 at the position corresponding to the back surface of the welded portion of the surface of each flange material is 50 or less immediately after welding, and the maximum strain is 0.2 mm or less. It is characterized by being. Here, ΔE ^* is calculated according to the following equation (1).
ΔE ^* = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 (1)
The ΔE ^* color difference components ΔL ^* , Δa ^* , Δb ^* are based on a white standard plate (L ^* = 96, a ^* = − 0.2, b ^* = 0.4).

Moreover, as stainless steel, it is set as ferritic stainless steel, The component of the ferritic stainless steel is C: 0.025 mass% or less, Si: 0.60 mass% or less, Mn: 1.00 mass% or less, P: 0.040 mass% or less, S: 0.020 mass% or less, Ni: 0.60 mass% or less, Cr: 16.00 to 35.00 mass%, Mo: 0.30 to 6.00 mass% N: 0.025% by mass or less is also included.
Furthermore, one or two of Nb: 0.10 to 1.00% by mass, Ti: 0.05 to 0.30% by mass, and Al: 0.01 to 0.50% by mass are added to the stainless steel. Ferritic stainless steel including the above can also be used.

  As a method of manufacturing the above-mentioned stainless steel laser welded shape steel, a flange member and a web material made of stainless steel plate are used as a corner joint portion or a T-shaped joint portion, and further, both a corner joint portion and a T-shaped joint portion are used. When manufacturing the welded shape steel provided, laser welding method that irradiates laser light as a welding method is used, and the temperature at the position corresponding to the back surface of the welded portion of the surface of each flange material is measured from the start of welding to the end of welding. It is characterized by being less than 200 ° C.

  The laser welded shape steel according to the present invention is excellent in corrosion resistance and appearance because it suppresses generation of a temper collar during welding and the maximum strain after correction at a position corresponding to the back surface of the welded portion of the surface of the flange material. In addition, when using ferritic stainless steel with a relatively low linear expansion coefficient and high thermal conductivity for the web and flange material, the maximum strain on the flange material surface is greater than when using austenitic stainless steel. Can be reduced. Furthermore, in order to suppress the occurrence of temper collar, the surface temperature during welding at the position corresponding to the back of the welded portion of the surface of the flange material is controlled, so the stainless steel laser welded steel can be used without sacrificing productivity. It is possible to manufacture.

The figure explaining the method of laser welding a corner joint part by one-pass irradiation from one side The figure explaining the method of carrying out the laser welding of the laser welded shape steel provided with the corner joint part and the T-shaped joint part Diagram explaining how to measure the maximum amount of strain in the height direction of the flange material

  As shown in FIG. 1, the laser-welded section 1 made of stainless steel according to the present invention has one pass from one side to a corner joint formed by pressing the end of the web material 3 vertically against the flange material 2. It is manufactured by irradiating the laser beam 4 according to, melting the end of the web material 3 to the side opposite to the side irradiated with the laser beam 4 and welding. At this time, the irradiation angle θ of the laser beam 4 to the flange material 2 is set to 30 degrees or less. The reason for irradiating the laser beam 4 with an inclination is to increase the penetration into the flange material 2 in order to ensure a certain bonding strength when the thickness of the flange material 2 is thicker than the thickness of the web material 3. is there.

When a stainless steel shape steel is manufactured by such a method, a temper color is generated at a position 5 corresponding to the back surface of the welded portion of the surface of the flange member 2 according to the surface temperature of the flange member 2. The inventors of the present invention have found that the occurrence of temper color can be grasped by using the color difference as an index, paying attention to the fact that the color of the surface of the flange member 2 changes due to the occurrence of temper color.
With the method shown in FIG. 1, SUS304 having a plate thickness of 2.3 mm is used as a raw material, laser welding is performed while changing the welding speed, and the color difference ΔE ^* of the position 5 corresponding to the back surface of the welded portion on the surface of the flange material 2 is determined according to JIS. Measured based on Z 8730. As a result, when the color difference ΔE ^* was 50 or less, the occurrence of temper color was not visually confirmed. Therefore, the color difference ΔE ^* of 50 or less was used as an indicator that no temper color was generated.

Further, when the temperature at the position 5 corresponding to the back surface of the welded portion of the surface of the flange member 2 was measured during welding, no temper color was generated and the color difference ΔE ^* was 50 or less if it was less than 200 ° C. I found it. Therefore, as a method for manufacturing the stainless steel laser welded shape steel of the present invention, the surface temperature of the position 5 corresponding to the back surface of the welded part during welding is made less than 200 ° C. among the surfaces of the flange member 2.
Specifically, a state of less than 200 ° C. can be realized by adjusting the welding conditions such as the welding speed or cooling the surface of the flange member 2 during welding. Although it does not specifically limit as a cooling method, The method of making a roll contact the surface of the flange material 2, or injecting a liquid or gas can be used.

  When the web material and the flange material are welded with a square joint, strain is generated on the surface of the flange material 2, and the maximum strain amount was confirmed under the same conditions as in the experiment of the temper collar generation condition. It was found that there is no problem in appearance if the maximum strain amount in the height direction of 2 is 0.2 mm or less.

As for the relationship between the temper color and the color difference ΔE ^* and the situation of the maximum strain amount on the surface of the flange material 2, the corner joint was implemented as described above, but both phenomena are caused by the temperature of the surface of the flange material 2. A similar index can be used for a T-shaped joint.

As a raw material in this invention, if it is stainless steel, it will not specifically limit, Austenitic stainless steel, ferritic stainless steel, martensitic stainless steel, etc. can be used.
Among these, when ferritic stainless steel is used, the maximum strain amount on the surface of the flange member 2 can be further reduced. This is due to the fact that ferritic stainless steel has a lower coefficient of linear expansion and higher thermal conductivity than other stainless steels. That is, since the coefficient of thermal expansion is low because the coefficient of thermal expansion is high and the cooling effect is high at the time of manufacture, the amount of thermal deformation is relatively small, which makes it easy to correct the flange material 2 after welding. For this reason, the stainless steel laser welded shape steel which has the surface of the flange material 2 of a favorable external appearance is realizable.

In particular, when it is necessary to secure product cost and corrosion resistance, ferritic stainless steel including the following component ranges can be used.
C: 0.025% by mass or less C is an element useful for obtaining the strength of steel, but when it is contained in a large amount, it tends to lower the corrosion resistance. The C content is preferably 0.025% by mass or less.
Si: 0.60% by mass or less Si is an element useful as a deoxidizer and a heat source in the steel making process, but when it is contained in a large amount, it tends to harden the steel. The content of Si is preferably 0.60% by mass or less.
Mn: 1.00% by mass or less Mn is an element useful as a deoxidizing agent in the steel making process, but when included in a large amount, Mn tends to form an austenite phase. The Mn content is preferably 1.00% by mass or less.
P: 0.040% by mass or less P tends to lower the corrosion resistance. The P content is preferably 0.040% by mass or less.
S: 0.020% by mass or less S tends to lower the corrosion resistance. The content of S is preferably 0.020% by mass or less.
Ni: 0.60% by mass or less Ni is preferable in terms of the effect of suppressing the progress of corrosion and the effect of improving the toughness of ferritic stainless steel. The Ni content is preferably 0.60% by mass or less.
Cr: 16.00-35.00 mass%
Cr is an element useful for ensuring corrosion resistance. However, when it is contained in a large amount, Cr tends to decrease not only in high cost but also in workability. The content of Cr is preferably 16.00 to 35.00% by mass.
Mo: 0.30 to 6.00 mass%
Mo is an element useful for improving the corrosion resistance of stainless steel in the presence of Cr, but if it is contained in a large amount, it tends to reduce not only the cost but also the workability. The content of Mo is preferably 0.30 to 6.00 mass%.
N: 0.025% by mass or less N, when contained in a large amount like C, tends to lower the corrosion resistance. The N content is preferably 0.025% by mass or less.

The stainless steel laser welded shape steel of the present invention further includes Nb: 0.10 to 1.00% by mass, Ti: 0.05 to 0.30% by mass, Al: 0.01 to 0.50% by mass. Among them, ferritic stainless steel containing one or more types can be used for further improving the corrosion resistance.
Nb: 0.10 to 1.00% by mass
Nb has a strong affinity with C and N and is preferable in terms of suppressing the intergranular corrosion of ferritic stainless steel, but a large amount of Nb tends to inhibit toughness. The content of Nb is preferably 0.10 to 1.00% by mass.
Ti: 0.05-0.30 mass%
Ti is preferable because it has a strong affinity with C and N and suppresses intergranular corrosion of ferritic stainless steel, but a large amount of Ti tends to deteriorate the surface quality of the steel. As for content of Ti, 0.05-0.30 mass% is more preferable.
Al: 0.01 to 0.50 mass%
Al is an effective element for refining and casting as a deoxidizer, but if it is added excessively, it degrades the surface quality and lowers the weldability and low temperature toughness of steel. As for Al content, 0.01-0.50 mass% is more preferable.

Using SUS304 having a plate thickness of 2.3 mm, 3.2 mm, and 4.5 mm as the flange material 2 and the web material 3, the laser welded shape steel 1 was manufactured by the method shown in FIG. 1 under the laser welding conditions shown in Table 1. The irradiation angle θ of the laser 4 light was 20 °.
After welding, the color difference ΔE ^* at position 5 corresponding to the back surface of the welded portion of the flange member 2 was measured based on JIS Z 8730. Further, the maximum strain amount of the flange material 2 was measured.
Table 2 shows the measured color difference ΔE ^* and the maximum temperature.

The maximum strain amount in the height direction of the flange member 2 was measured by the method shown in FIG. That is, the ruler 6 is pressed against the flange material 2 and the gap generated between the flange material 2 and the ruler 6 is measured using a gap gauge. And the value calculated _| required by the following formula _| equation using the measured largest gap _| interval amount _Amax and minimum gap _| interval amount _Amin was made into the largest distortion amount.
Maximum strain = A _max −A _min

As shown in Table 2, under the condition that the maximum temperature at the position 5 corresponding to the back surface of the welded portion of the flange material 2 is 200 ° C. or higher, the color difference ΔE ^* exceeds 50 for any plate thickness, and the temper color is visually observed. Was confirmed.
Moreover, as a result of correcting by pressing a roll against the front and back surfaces of the flange material 2, the maximum strain amount was 0.2 mm or less under the condition where the maximum temperature was less than 200 ° C.
(Example 2)

As the flange material 2 and the web material 3, a ferritic stainless steel plate having Cr: 30%, Mo: 2%, Ti: 0.15%, Nb: 0.15%, Al: 0.09%, and the balance Fe is used. The other conditions were the same as in Example 1 to produce a laser welded section steel.
Table 3 shows the results of measuring the maximum temperature and the color difference ΔE ^* at the position 5 corresponding to the back surface of the welded portion of the surface of the flange material 2 of the manufactured laser welded steel.

As shown in Table 3, also in Example 2, the color difference ΔE ^* in any plate thickness under the condition that the maximum temperature at the position 5 corresponding to the back surface of the welded portion of the surface of the flange member 2 is 200 ° C. or higher ^. Was over 50, and temper color was confirmed by visual observation.
Moreover, as a result of pressing the roll against the front and back surfaces of the flange material 2 and performing correction, the maximum strain amount was 0.1 mm or less under the condition where the maximum temperature was less than 200 ° C.
(Example 3)

  The same material as Example 2 was used as the flange material 2 and the web material 3, and the stainless steel laser welded shape steel 1 having the corner joint portion and the T-shaped joint portion shown in FIG. 2 was manufactured. The manufacturing conditions were the same as in Example 1.

About the manufactured laser welded shape steel, the color difference ΔE ^* and the maximum temperature at the position corresponding to the back surface of the welded portion of the surface of the flange member 2 were measured. Of the surface of the flange material 2A on the T-joint portion side, the relationship between the color difference at the position 5A corresponding to the back surface of the welded portion and the maximum temperature is shown in Table 4, and among the surfaces of the flange material 2B on the corner joint portion side, the back surface of the welded portion Table 5 shows the relationship between the color difference at the corresponding position 5B and the maximum temperature.

As shown in Tables 4 and 5, on the surface of the flange material 2A or 2B, the maximum temperature at the position 5A or 5B corresponding to the back surface of the welded portion is 200 ° C. or higher. The color difference ΔE ^* exceeded 50, and the temper color was confirmed by visual observation.
Moreover, as a result of pressing the roll against the front and back surfaces of the flange material 2 and performing correction, the maximum strain amount was 0.1 mm or less under the condition where the maximum temperature was less than 200 ° C.

DESCRIPTION OF SYMBOLS 1 Stainless steel laser welding shape steel 2 Flange material 3 Web material 4 Laser beam 5 Position which hits a welding part back surface 6 Ruler (theta) Irradiation angle of laser beam 4

Claims (6)

Using a stainless steel plate, it is a shape steel having a square laser welded joint composed of a web material and a flange material,
The color difference ΔE ^* based on JIS Z 8730 on the flange material surface which is the back surface position of the welded portion is 50 or less immediately after welding,
A stainless steel laser welded shape steel, wherein the maximum strain in the height direction of the flange material is 0.2 mm or less.
Here, the color difference ΔE ^* is calculated according to the following equation (1).
ΔE ^* = [(ΔL ^* ) ² + (Δa ^* ) ² + (Δb ^* ) ² ] ^1/2 (1)
Delta] E [Delta] L ^* of the color difference components of ^{*, Δa *, Δb *} is a white standard plate ^{(L * = 96, a *} = -0.2, b * = 0.4) to a reference. Using a stainless steel plate, as a laser weld joint composed of a web material and a flange material, it is a shape steel having a square joint and a T-shaped joint,
The stainless steel laser welded shape steel according to claim 1. As the stainless steel plate, using a ferritic stainless steel plate,
The stainless steel laser welded shape steel according to claim 1 and 2. The ferritic stainless steel sheet is C: 0.025 mass% or less, Si: 0.60 mass% or less, Mn: 1.00 mass% or less, P: 0.040 mass% or less, S: 0.020 mass% Hereinafter, Ni: 0.60 mass% or less, Cr: 16.00-35.00 mass%, Mo: 0.30-6.00 mass%, N: 0.025 mass% or less are included. ,
The stainless steel laser welded shape steel according to claim 3. The ferritic stainless steel sheet may further include one or two of Nb: 0.10 to 1.00% by mass, Ti: 0.05 to 0.30% by mass, and Al: 0.01 to 0.50% by mass. Including more than species,
The laser-welded section made of stainless steel according to claim 4. It is a method of manufacturing a welded shape steel formed with a square welded joint composed of a web material and a flange material using a stainless steel plate,
Using a laser welding method of irradiating laser light as a welding method,
The temperature of the flange material surface which is the back surface position of the welded portion is less than 200 ° C. from the start of welding to the end of welding,
Stainless steel laser welded shape manufacturing method.

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