JP2929515B2 - Solid wire for gas shielded arc welding - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low spatter solid wire for gas-shielded arc welding in which the surface layer is enriched with oxygen.

[0002]

_2. Description of the Related Art A single gas such as Ar, CO ₂ , He, or A
Ar-CO ₂ , Ar-O consisting of mixed gas of r, He, CO ₂ , O ₂ etc.
_2, Ar-He-CO ₂ shielding gas -O ₂ or the like is used in gas shielded arc welding. In order to reduce spatter during gas shielded arc welding using these shielding gases, several techniques for generating an oxygen-enriched layer made of an oxide on the surface of a solid wire have been proposed. The oxide present in the surface layer of the wire lowers the surface tension of the droplet during welding, and makes the droplet finer. Also,
Oxide has the function of smoothing the transfer of droplets to the base material by the arc stabilizing action of oxygen itself, thereby reducing the amount of spatter generated.

The following methods have been proposed as a method for enriching oxygen. For example, as disclosed in JP-A-60-40685, a method in which an oxide is mixed in advance with a lubricating oil at a wire drawing stage. As disclosed in JP-A-59-110496, JP-A-60-40685, etc., a method of plating while leaving one part of the scale formed on the surface layer by annealing or the like. As disclosed in JP-A-58-187298 and JP-A-60-40685, a method of enriching oxides on the surface by performing a heat treatment after plating. JP-A-58-128294, 59-61592, 59-66996, 60
As disclosed in US Pat.
A method of performing grain boundary oxidation at a temperature between ℃ and 950 ℃.

[0004]

However, according to the above-mentioned method, it is difficult to make a uniform and sufficient amount adhere to the surface layer of the wire. In other words, it is difficult to uniformly mix oxides in the lubricating oil with the method described above, and the amount of the lubricating oil in the final product is only about 0.1% of the wire weight, and it is sufficient for low spatter There is a problem that it is difficult to uniformly attach an object.

In the method (1), it is difficult to apply sound plating in a state where the scale is uniformly and evenly attached to the wire surface. Therefore, it is necessary to partially leave the scale. However, there is a problem that it is difficult to control the residual amount of the scale at that time. With regard to the method (1), if a heat treatment is applied after plating, it is inevitable that the plating layer is oxidized. The amount of oxide on the surface of the wire and the conductivity through the power supply nozzle tip are contradictory.If a sufficient amount of oxide is secured to reduce the spatter, the conductivity deteriorates and the arc becomes unstable and becomes insufficient. Low spatter cannot be measured. In addition, depending on the amount of the enriched oxide, spatter may be increased.

As for plating, since plating is performed after heat treatment and pickling, the plating layer is sound and the effect of reducing spatter can be expected to some extent due to the oxide at the grain boundaries inside the plating layer. However, since the occurrence of grain boundary oxidation depends on the grain boundary pitch of the surface layer, the occurrence is generally coarser at 5 μm or more in the C direction and 100 μm or more in the L direction, making droplet transfer finer and reducing spatter. There is a problem that is not enough to achieve.

[0007]

Means for Solving the Problems As a result of intensive studies, the inventors have found that the oxides can be enriched in a finer and more uniform form than in the grain boundary oxidation method and in a form more concentrated in the surface layer, thereby achieving the target. As a result of examining whether or not the sputtering can be reduced, it was found that the target sputtering can be reduced by providing the intragranular oxide layer by the intragranular oxidation on the surface layer of the wire.

That is, in the present invention, C is 0.15% by weight.
In the following, Si should be 0.1% or more and 1.5% or less, Mn should be 0.80% or more and 2.5% or less, Cr should be 0.15% or more and 2.0% or less, Ni should be
0.3% or less, Mo 0.3% or less, Ti 0.3% or less, Al 0.
3% or less, Nb is 0.05% or less, B is 0.01% or less, and the balance is composed of iron and unavoidable impurities, and the intragranular oxide layer has a depth of 2.5 μm or more in the surface layer of the wire. The layer is a solid wire for gas shielded arc welding characterized in that it has at least 10 intragranular oxides per 100 μm ² in cross-sectional area, and in terms of weight ratio C is 0.05% or less, Si is 0.1% or more, 0.4% A solid wire for gas shielded arc welding characterized by the following.

[0009]

The reasons for limiting the wire composition of the present invention as described above are as follows. In order to cause intragranular oxidation in a wire with a commonly used composition, a heating temperature of around 750 ° C, which is generally used for annealing in the production of solid wires, requires a prolonged soaking heat treatment of 10 hours or more. It is. In consideration of performing annealing in a continuous furnace in order to increase productivity, it is desirable to suppress the annealing time to several tens of seconds or less, but for that purpose, the annealing temperature must be increased to a high temperature of 1000 ° C. or more. In that case, equipment must be drastically changed to enable heat treatment at a high temperature, which causes a problem in equipment cost.

In the present invention, an oxygen-enriched layer, ie, an intragranular oxide layer, formed by intragranular oxidation on the surface layer can be obtained by adding Cr to a heat treatment at about 750 ° C. for about 3 hours. In order to form an intragranular oxide layer, the addition of Cr is effective as described above, but it is necessary to further define Si and C. Also, Ni, Mo, Al, Ti, Nb, and B are regulated as necessary to secure the toughness of the weld metal. In addition to these elements, Cu and N are added as necessary to ensure corrosion resistance, toughness, strength, and the like.

If the depth of the intragranular oxide layer in the surface layer portion is less than 2.5 μm, it is not possible to achieve a sufficiently low sputtering due to an insufficient amount of the oxide. In the present invention, the intragranular oxide layer has a cross-sectional area of 100 μm.
A layer having 10 or more intragranular oxides per m ² . In the present invention, an intragranular oxide means a granular oxide precipitated in a crystal grain. If the number of intragranular oxides in the intragranular oxide layer is less than 10 per 100 μm ^{2 in} cross-sectional area, the pitch of the oxide is coarse and sufficient sputtering cannot be achieved as in the case of grain boundary oxidation. The number of intragranular oxides was measured with a microscope for the intragranular oxide layer in a cross section perpendicular to the wire longitudinal direction.
The value converted to the number per μm ² is used. Regarding the Cr content, it is necessary to add 0.15% or more in order to cause intragranular oxidation. However, if it exceeds 2.0 %, the toughness is deteriorated. Therefore, the Cr content is 0.15% or more, 2.0 %
It was as follows.

C is an indispensable element for securing the strength. However, if C is added in excess of 0.15%, the toughness extremely decreases, so the amount of C added is set to 0.15% or less. Si is an indispensable element mainly for obtaining a deoxidizing agent and high toughness. However, if Si is added in excess of 1.5%, the toughness is extremely reduced.
% And 1.5% or less.

The intragranular oxide layer can be more easily obtained by setting the C content to 0.05% or less and the Si content to 0.1% or more and 0.4% or less. About Mn
It must be mainly contained in order to obtain a deoxidizing agent and high toughness. If it is less than 0.8%, there is a risk that hot cracks may occur due to O and S. On the other hand, if it exceeds 2.5%, cold workability decreases and toughness cannot be secured. Therefore, the Mn content is set to 0.80% or more and 2.5% or less.

Ni and Mo are elements that suppress intragranular oxidation, and when contained in 0.3% or more, the tendency becomes remarkable and the strength is remarkably improved. Therefore, it is preferable to add a large amount as a general welding material. Absent. Therefore, Ni
The content was set to 0.3% or less for both the amounts of Mo and Mo. When Al exceeds 0.3% or more, toughness at low temperatures is observed to be deteriorated. Therefore, the amount of Al is set to 0.3% or less.

[0015] Ti is an effective component for preventing the coarsening of the crystal grains of the weld metal and increasing the strength.
However, when Ti is contained in excess of 0.3%, deterioration of toughness is remarkably observed. Therefore, the Ti content was set to 0.3% or less. Like Nb, Nb is an effective component for preventing coarsening of the crystal of the weld metal and increasing the strength. However, when the content exceeds 0.05%, deterioration of toughness is remarkably observed. Therefore, the Nb content is set to 0.05% or less.

B, like Nb and Ti, is an effective component for preventing the crystal grains of the weld metal from becoming coarse and increasing the strength. However, when the content exceeds 0.01%, deterioration of toughness is remarkably observed. Therefore, the B content is
0.01% or less. The production process is generally a process of hot rolling → intermediate drawing → intermediate annealing → pickling → plating → finish drawing. The application of the intragranular oxide layer is performed in this intermediate annealing stage. When grain boundary oxides are formed, they are always connected to the surface, so that they are partially peeled off by pickling and cause plating unevenness. When the grain boundary oxide is formed, a pine-skinned horizontal plating crack is generated by the finish drawing. On the other hand, since the intragranular oxide of the present invention has no connection with the surface, the oxide of the intragranular oxide layer is not removed by pickling, and there is no adverse effect on the plating treatment, and the pine-skinned plating No cracks occur. In the wire composition of the present invention, by adding Cr as described above, it is possible to generate intragranular oxides under the same heat treatment conditions as the annealing of general materials.

Further, spatter can be reduced as compared with a conventional wire regardless of the shielding gas during welding and welding conditions.

[0018]

[Example] Hot-rolled finished wire diameter was intermediately drawn from 5.5mmφ to 2.6mmφ, heat treatment described below was performed, pickling, plating, finish drawing to 1.2mmφ, and the amount of spatter generated was measured. . For the heat treatment, the 2.6 mm φ wire after intermediate drawing was heated in a nitrogen-free atmosphere furnace at 720 ° C for 3 hours.
In addition, in order to cause intragranular oxidation, the annealing atmosphere should be 50 l / min of nitrogen gas containing 0.01% to 1.5% of water vapor.
100 liters have been delivered.

Table 1 shows the chemical composition of the steel wire used.
As shown in Table 2, the welding conditions at the time of measuring the amount of spatter generation were 2 conditions for each of the shielding gas of CO ₂ and Ar-CO ₂ , and a total of 4 conditions were used. The cross section (C cross section) perpendicular to the longitudinal direction of the wire is observed with a microscope (optical microscope or electron microscope), and the depth of the intragranular oxide layer where the intragranular oxide exists and the intragranular in the intragranular oxide layer The number of oxides was measured and converted to the number per 100 μm ^{2 of} cross-sectional area. All generated spatters were collected. Table 3
The results of Examples and Comparative Examples are shown in FIG. 5, but in Examples Nos. 1 to 44 of the present invention, a sufficiently low spatter was achieved.

[0020]

[Table 1]

[0021]

[Table 2]

The amount of spatter generated under welding condition No. 1 using Ar-20% CO ₂ as a shielding gas, the intragranular oxide layer depth (μm), and the cross-sectional area in the intragranular oxide layer per 100 μm ² 1 and 2 show the relationship with the number of oxides in the granular particles having a diameter of 0.1 to 1 μm. If the intragranular oxide layer depth is less than 2.5 μm and the number of intragranular oxides in the intragranular oxide layer 100 μm ² is less than 10, the target sputtering amount of 0.25 g / min or less cannot be achieved.

Further, as shown in Table 3, the test results show that a wire with a C content of 0.05% or less and a Si content of 0.4% or less was used.
Examples using Nos. 4, 7, 9, 12, 13, 14, 15, 16, 18, No. 3, 6, 7, 9, 10, 11, 12, 14, 18, 27, 28,
29, 32, 35, 36, 41, 42, 43, and 44 showed particularly excellent characteristics among the examples. The evaluation method followed Table 4. Comparative Example N
In o.45, 46, 47, 48, 49, and 50, the Cr content is less than 0.15%, so that the intragranular oxide layer depth is 2 μm or less, and the cross-sectional area is 1
The number of intragranular oxides in 00 μm ² is as small as 8 or less, and the amount of sputtering greatly exceeds the target value.

[0024]

[Table 3]

[0025]

[Table 4]

FIG. 3 shows a micrograph of a cross section in the C direction after the heat treatment of the comparative example . Grain boundary oxidation occurs to a depth of about 15 μm, but the pitch is coarse. In contrast, the embodiment shown in FIG. 4
In the cross-section after the heat treatment, granular intragranular oxides of 0.1 to 1 μm are uniformly generated in the surface layer.

[0027]

According to the method of the present invention, it is possible to form a fine, uniform and high-density intragranular oxide layer on the very surface portion of a steel solid wire under heat treatment conditions close to ordinary heat treatment conditions. Productivity has increased significantly. If this wire is used for gas shielded arc welding, generation of spatter can be significantly reduced. As a result, the work of removing spatter adhered to the work or the nozzle of the welding torch was remarkably reduced, and significant effects such as reduction in the number of maintenance steps and improvement in the work environment were obtained.

[Brief description of the drawings]

FIG. 1 shows the relationship between spatter generation and intragranular oxide layer depth when a steel solid wire having the chemical composition shown in Table 1 is welded under welding conditions No. 1 using CO ₂ as a shielding gas. It is a characteristic diagram.

Fig. 2 The amount of spatter generated and the intragranular oxide per 100 μm ² cross section when a steel solid wire having the chemical composition shown in Table 1 was welded under welding conditions No. 1 using CO ₂ as a shielding gas. FIG. 4 is a characteristic diagram showing a relationship with numbers.

FIG. 3 is a micrograph showing a metal structure in a C-direction cross section after heat treatment of a comparative example .

FIG. 4 is a micrograph showing a metal structure in a C-direction cross section after heat treatment of an example .

Claims (2)

(57) [Claims] 1. A solid wire used for gas shielded arc welding, wherein the weight ratio of C is 0.15% or less, and the content of Si is 0.15% or less.
% Or more, 1.5% or less, Mn 0.80% or more, 2.5% or less, Cr
0.15% or more, 2.0% or less, Ni 0.3% or less, Mo 0.3
%, Ti 0.3% or less, Al 0.3% or less, Nb 0.05%
In the following, B is set to 0.01% or less, and the balance consists of iron and unavoidable impurities, and the depth of the intragranular oxide layer in the surface layer of the wire is reduced.
2.5 μm or more, and the intragranular oxide layer has a cross-sectional area of 100 μm ²
A solid wire for gas shielded arc welding, wherein the solid wire has at least 10 intragranular oxides. 2. The method according to claim 1, wherein C is 0.05% by weight.
A solid wire for gas shielded arc welding, wherein the content of Si is 0.1% or more and 0.4% or less.