JP3525191B2 - CO2 gas welding steel wire and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire for CO ₂ gas welding and a method for manufacturing the same, and particularly in so-called carbon dioxide shielded arc welding using CO ₂ as a shielding gas, arc stabilization and reduction of spatter generation amount. Not only is it intended to achieve excellent bead shape and slag peelability.

[0002]

_2. Description of the Related Art The welding method using CO ₂ gas as a shielding gas is widely used in various fields such as automobiles, shipbuilding and construction due to the rapid spread of automatic welding, and its productivity depends largely on the welding speed. To be done. However, the actual welding process is currently performed at a low speed in order to secure a good bead shape and prevent frequent occurrence of spatter, and there is a great need for a welding wire capable of performing sound welding at a high speed.

Conventionally, Japanese Patent Application Laid-Open No. 62-296993 proposes a technique for reducing spatter of a thin plate and securing a bead shape by adjusting a pulse welding method and a wire composition. It was hard to say. Further, a method of reducing the amount of spatter generated by adding potassium is proposed in Japanese Patent Laid-Open No. 6-218574. This method is effective for reducing spatter, but the bead shape is convex, , Left a problem in this regard.

[0004]

As described above, in the welding of thin plates, although the productivity can be improved by increasing the welding speed, increasing the welding speed only increases the amount of spatter generated. However, there was a problem that it was difficult to secure the bead shape. Especially in fillet welding,
In many cases, a smooth and wide weld bead is required, and at the same time, ensuring slag peelability is also an important factor.

The present invention was developed in view of the above situation, and in CO ₂ gas shielded arc welding, not to mention stabilization of the arc and reduction of spatter, as well as ensuring excellent bead shape and slag peeling property. The aim is to propose a possible welding steel wire together with its advantageous manufacturing method.

[0006]

[Means for Solving the Problems] Now, the inventors
CO ₂ achieves low spatter by addition of (potassium)
With respect to the gas welding wire, the following findings were obtained as a result of intensive studies for the purpose of obtaining a bead shape having a spread and an excellent slag peeling property while securing the effect of reducing spatter.

(1) In a wire having K, in order to obtain an excellent bead shape, Si is 0.85 wt% or more and Mn is 1.0
wt% to 2.0 wt%, (K × 9000) / Si 1.0
It is necessary to adjust the amounts of K, Si and Mn so as to be the above. (2) Next, in order to obtain excellent slag peelability, Si is
0.85wt% or more, Mn 2.0wt% or less, (Si + Mn) /
It is necessary to adjust the amounts of Si, Mn, and O so that (O × 230) becomes 1.0 or more. (3) Further, the effect of lowering the spatter by adding K is (K × 9000) / Si is 1.0 wt% or more and 9.0 wt% or less,
Si, so that (Si + Mn) / (O x 230) is 4.0 or less,
The effect can be maintained by adjusting the amounts of K, Mn, and O. (4) Furthermore, when Ca is added in an amount of 0.0020 wt% or less, the arc is stabilized and further reduction of spatter is achieved. (5) Note that suppressing Ti to 0.03 wt% or less is advantageous for high-speed welding of thin plates, and if 0.003 wt% or more of Se is contained, even lower spattering and a wide bead shape are achieved. Also, excellent characteristics are obtained with respect to the peeling property of the slag. (6) Regarding the addition of K, an internal oxide layer is formed on the surface layer of the wire in an inert gas atmosphere during annealing during the wire drawing step, and K is diffused in this to stably hold it as an oxide. Is preferred. (7) Thus, it is possible to overcome the adverse effect that the bead shape becomes convex while having the effect of reducing spatter by adding K, and also to obtain excellent scale peelability, improving workability and welding. It is possible to achieve both high quality. The present invention is based on the above findings.

That is, according to the present invention, C: 0.15 wt% or less, Si: 0.85-2.50 wt%, Mn: 1.0-2.0 wt%, O: 0.
020 wt% or less, K: 0.0001 to 0.0030 wt%, the following formulas (1) and (2) 9.0 ≧ (K × 9000) / Si ≧ 1.0 --- (1) 4.0 ≧ (Si + Mn) / (O × 230 ) ≧ 1.0 --- It is a steel wire for CO ₂ gas welding, characterized in that it is contained in a range satisfying (2), and the balance is substantially Fe composition.

In the present invention, in the wire,
It is preferable to contain Ca: 0.0020 wt% or less.

Further, according to the present invention, C: 0.15 wt% or less, S
i: 0.85 to 2.50 wt%, Mn: 1.0 to 2.0 wt% The surface of the steel wire having a composition is coated with an aqueous solution of potassium salt and then annealed to give K and O of K: 0.0001.
~ 0.0030 wt%, O: 0.020 wt% or less, and the following formulas (1) and (2) 9.0 ≧ (K × 9000) / Si ≧ 1.0 --- (1) 4.0 ≧ (Si + Mn) / (O × 230 ) ≧ 1.0 --- After forming the internal oxide layer containing in the range satisfying (2),
It is a method for producing a steel wire for CO ₂ gas welding, which comprises pickling, copper plating, and then wire drawing.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION First, the reason for limiting the wire composition to the above range in the present invention will be explained. C: 0.15 wt% or less C is an element necessary to secure the strength of the weld metal, but if it exceeds 0.15 wt%, toughness cannot be secured.
The amount was 0.15 wt% or less.

Si: 0.85 to 2.50 wt% Si is an essential element mainly as a deoxidizing agent, but the addition thereof increases spatter, and if it exceeds 2.50 wt%, workability cannot be secured. On the other hand, half of Si turns into slag during welding, but it has the function of being bound to K in this process and preventing it from forming a convex bead due to K. It also has the function of forming a glassy slag and improving the peelability. However, if it is less than 0.85 wt%, good slag peeling property and smooth bead shape cannot be obtained. Therefore, the Si content is limited to the range of 0.85 to 2.50 wt%.

Mn: 1.0 to 2.0 wt% Mn is an essential element as a deoxidizer and for obtaining high strength and high toughness. Like Si, Mn binds to K in the deoxidation process and acts to prevent the formation of convex beads due to K, but if it is less than 1.0 wt%, a smooth bead shape cannot be secured. On the other hand, excessive addition not only hinders the vitrification of the slag, but also increases the viscosity of the droplets and the deposited metal to facilitate the formation of convex beads, and when it exceeds 2.0 wt%, sufficient slag peeling properties and bead shape are obtained. Cannot be secured. Therefore, the Mn content is limited to the range of 1.0 to 2.0 wt%.

O: 0.020 wt% or less O reduces the amount of spatter generation, but on the other hand, it tends to increase the oxidation of Fe and Ti and hinder the peeling property of slag.
If it exceeds 20 wt%, sufficient slag peelability cannot be secured. Therefore, O is limited to 0.020 wt% or less.

K: 0.0001 to 0.0030 wt% K reduces spatter, but tends to form thin and convex beads by increasing the energy at the center of the arc. If the content is less than 0.0001 wt%, the effect of reducing spatter is poor, while if it exceeds 0.0030 wt%, smooth and satisfactory beads cannot be obtained. Therefore,
The amount of K was limited to the range of 0.0001 to 0.0030 wt%. In addition, K
Since it has a low boiling point of about 760 ° C and the yield in the molten steel stage is extremely low, it is very difficult to allow K to exist in the wire. However, it is effective by utilizing the thermal diffusion in the wire drawing process described later. Can be given to.

Although the reasons for limiting the composition range of each component have been described above, in order to achieve the intended object of the present invention, it is not sufficient to individually define the composition range of each component as described above. In order to achieve low spatter and excellent bead shape and slag peelability,
(1) and (2) 9.0 ≧ (K × 9000) /Si≧1.0 --- (1) 4.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 --- (2) is important. That is, various investigations were conducted to obtain an excellent bead shape in high-speed welding in addition to low spattering due to K. As a result, 0.85 wt% of Si was obtained.
It is extremely effective to add K so as to satisfy the formula (1) after containing the above, in order to reduce spatter and obtain a good bead shape, and Si and Mn in relation to O, (2)
It has been determined that the addition so as to satisfy the formula is extremely effective in reducing spatter and improving slag peeling property.

9.0 ≧ (K × 9000) /Si≧1.0 --- (1) K has a strong bond with Si oxide, and K increases the amount of Si in steel and lowers the electrode voltage to expand the arc. The arc stabilizing effect tends to be canceled out. (K × 9000) / Si
If it is less than 1.0, spatter is often generated. On the other hand, if it exceeds 9.0, the influence of K on the arc is large, the arc length becomes long, the droplet transfer becomes unstable, and large spatters increase, resulting in a convex bead. Are easily formed. Therefore (K x 90
The value of (00) / Si is limited to the range of 1.0 or more and 9.0 or less.

When the value of 4.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 --- (2) (Si + Mn) / (O × 230) is less than 1.0, the slag peeling property is poor, while it exceeds 4.0. And the occurrence of spatter increases. This is because when Si and Mn are small with respect to the amount of O
It is considered that it becomes a slag mainly composed of Fe and Ti, has a strong bonding force with the deposited metal, and deteriorates the peeling property. On the other hand, if Si and Mn are large relative to O, it is considered that a thin oxide centering on Si and Mn is formed in the droplet, which causes the arc to become unstable and spatter to increase.
Therefore, the value of (Si + Mn) / (O × 230) is 1.0 or more, 4.0
Below.

Although the essential components have been described above, the following components may be contained in the present invention, if necessary. Ca: 0.0020 wt% or less Ca is a useful element that stabilizes the arc and reduces the generation of spatter, but if the content exceeds 0.0020 wt%, not only the slag peeling property is impaired, but also spatter is generated. Since Ca tends to increase, the content of Ca is set to 0.0020 wt% or less.

Se: 0.003 to 0.200 wt% Se effectively contributes to the improvement of bead shape and slag peeling property with lower spattering and spread,
If the content is less than 0.003 wt%, the effect of addition is poor, while if it exceeds 0.200 wt%, the effects on low spattering, formation of beads with spread and slag delamination reach saturation, rather on the human body and crack resistance. Since Se has a great adverse effect on sex, Se is limited to the range of 0.003 to 0.200 wt%.

Cr: 0.60 wt% or less, Ni: 3.0 wt% or less, M
o: 0.50 wt% or less, Cu: 3.00 wt% or less, B: 0.005 wt%
Below, Cr, Ni, Mo, Cu and B are added as necessary for the purpose of securing strength and weather resistance of the weld metal. However, excessive addition causes a decrease in toughness, so the respective contents were made to fall within the above ranges.

At least one selected from Ti, Zr, Al, Nb and V: 0.30 wt% or less Ti, Zr, Al, Nb and V are necessary for the purpose of securing the strength and the weather resistance of the weld metal. Add according to.
However, since excessive addition leads to a decrease in toughness, the content is set to 0.30 wt% or less in either case of single addition or composite addition. Especially when welding at high speed,
An excellent bead shape can be obtained by adjusting the amount of Ti to 0.03 wt% or less and decreasing the viscosity of the droplet and the deposited metal.

P: 0.030 wt% or less, S: 0.035 wt% or less, N: 0.010 wt% or less P, S and N reduce the toughness of the weld metal,
It is desirable to reduce as much as possible, but P: 0.030 wt
% Or less, S: 0.035 wt% or less, and N: 0.010 wt% or less are acceptable.

The molten steel prepared to have the above-mentioned suitable composition is preferably continuously cast into a billet and then hot-rolled into a steel wire. Then, after annealing, the product is subjected to pickling, copper plating and wire drawing, but in the present invention, in the above annealing step, an internal oxide layer is formed on the surface layer of the steel wire, It is important to include K in this internal oxide layer. Because K
Since it has a boiling point of about 760 ° C and the yield in the molten steel stage is extremely low, it is extremely difficult to allow K to exist in the wire. However, if thermal diffusion during the wire drawing process is used, it is effective. This is because K can be contained.

The atmosphere in the above annealing treatment is as follows.
An inert atmosphere such as nitrogen gas is preferable, and in this inert gas atmosphere, the water content of the wire, the oxide film on the surface, or a trace amount of oxidizing gas (CO ₂ , H ₂ O, O ₂ ) contained in the atmosphere
As a result, as shown in FIG. 1, an internal oxide layer is formed on the surface layer of the steel wire, and K is diffused in the internal oxide layer to stably maintain it as an oxide. Regarding the application of K, the means for applying it to the final product or applying it from a wire drawing lubricant is also
It is an effective means although the stability and uniformity of K are somewhat lacking. After that, the product may be subjected to pickling, copper plating and wire drawing according to a conventional method.

[0026]

[Example] Steel blooms (Cu
(Including the amount deposited by subsequent plating) was made into a steel wire of 5.5 to 7.0 mmφ by hot rolling, and the wire diameter was made to be 2.0 to 2.8 mmφ by cold drawing. Then, 2-30
% 3 potassium citrate aqueous solution and then O ₂ : 20
0 ppm or less, CO ₂ : 0.1% or less in N ₂ atmosphere (dew point:-
(2 ℃ or less) to 750 to 950 ℃, and adjust the wire diameter, potassium salt concentration and heating temperature and time to adjust the amount of oxygen and potassium due to internal oxidation of the wire, followed by pickling, Cu plating and cooling. A 1.2 mmφ steel wire for welding was manufactured by performing hot wire drawing.

Using the steel wire for welding thus obtained, the result of investigation on the amount of spatter generated, slag peeling property and bead shape when lap fillet welding was performed,
It shows in Table 3. For welding, 100% CO ₂ was used as a shielding gas at a rate of 20 l / min, and a thyristor power supply was used to weld current: 210 A, voltage: 22 V, welding speed: 80 cm / mi.
Overlap fillet welding of 3.2 mm thin steel plates was performed under the condition of n.

The target amount of spatter generation was set to 0.80 g / min or less. And, in particular, 0.60 g / min or less was evaluated as good (○), 0.60 g / min or more and 0.80 g / min or less was acceptable (△), and 0.80 g / min or more was not acceptable (x). Regarding the slag release property, the target value of the natural release rate was set to 40% or more. In particular, 60% or more was rated as good (◯), less than 60% was rated as 40% or more as acceptable (△), and less than 40% was rated as unacceptable (x).
The bead shape was evaluated by the ratio of the throat thickness (T) to the bead leg length (W) as shown in FIG. 2, and the target value of T / W was set to 0.6 or less. In particular, 0.4 or less was evaluated as good (◯), 0.4 or more and 0.6 or less was acceptable (△), and 0.6 or more was not acceptable (x).

Further, in FIGS. 3 and 4, (K × 90
The relationship between (00) / Si and T / W and the amount of spatter generated is shown in FIGS. 5 and 6, respectively, (Si + Mn) / (O × 23
0) with the natural slag release rate and the amount of spatter generated.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

As shown in Table 3, controlling the wire composition within the proper range of the present invention is effective in reducing spatter as shown in FIGS. 4 and 6, and as shown in FIGS. 3 and 5. Excellent bead shape and slag peelability were obtained even at high speed welding. Further, as shown in the conforming examples 29, 30, 31, 32, the addition of Se was effective in further reducing the spatter, and the excellent bead shape and slag peeling property could be obtained. The amount of spatter increases with the addition of Ti, and the bead shape and slag peeling property both tend to deteriorate.
% Or less is desirable.

On the other hand, (K × 9000) / Si <of Comparative Examples 33 and 34
In the case of 1.0, spatter frequently occurred, and in Comparative Examples 35 and 36 (Si
In the case of + Mn) / (O × 230) <1.0, satisfactory slag peeling property was not obtained. (K × of Comparative Examples 41 and 42)
In 9000) / Si> 9.0, spatter frequently occurred and a satisfactory bead shape could not be obtained. In Comparative Examples 43 and 44, (Si + Mn) / (O × 230)> 4.0, spatter frequently occurred. Further, in Comparative Example 37, since the Si content was less than 0.85 wt%, satisfactory slag peeling property and bead shape could not be obtained. In Comparative Example 38, since the Mn amount was less than 1.00 wt%, a satisfactory bead shape could not be obtained.
In Comparative Example 39, the Mn content exceeded 2.0 wt%, so that satisfactory slag peelability and bead shape could not be obtained. In Comparative Example 40, the amount of Ca exceeded 0.0020 wt%, so that it was not possible to obtain satisfactory slag peeling properties and spatter reduction effects.

[0035]

As described above, according to the present invention, in CO ₂ gas welding, it is possible to obtain a flat and excellent bead shape with excellent arc stability, extremely small amount of spatter generation, and excellent slag peeling property. .

[Brief description of drawings]

FIG. 1 is a diagram showing an internal oxide layer in a surface layer of a wire.

FIG. 2 is an explanatory diagram of T / W which is a bead shape evaluation index.

FIG. 3 is a diagram showing a relationship between (K × 9000) / Si and T / W.

FIG. 4 is a diagram showing the relationship between (K × 9000) / Si and the amount of spatter generated.

FIG. 5 is a diagram showing the relationship between (Si + Mn) / (O × 230) and the natural slag release rate.

FIG. 6 is a diagram showing the relationship between (Si + Mn) / (O × 230) and the amount of spatter generated.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-218574 (JP, A) JP-A-7-314179 (JP, A) JP-A-7-251292 (JP, A) JP-A-63- 149093 (JP, A) JP 8-132280 (JP, A) JP 7-303995 (JP, A) JP 7-299583 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 35/02 B23K 35/36 B23K 35/40

Claims (3)

(57) [Claims] 1. C: 0.15 wt% or less, Si: 0.85 to 2.50 wt%, Mn: 1.0 to 2.0 wt%, O: 0.020 wt% or less, K: 0.0001 to 0.0030 wt% by the following formula (1) and (2) 9.0 ≧ (K × 9000) /Si≧1.0 --- (1) 4.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 --- Contains in the range satisfying (2), the rest is substantially A steel wire for CO ₂ gas welding, which is characterized by having a Fe composition as a rule. 2. The wire according to claim 1, further comprising C
a: CO ₂ gas welding steel wire having a composition containing 0.0020 wt% or less. 3. An aqueous solution of potassium salt is applied to the surface of a steel wire having a composition containing C: 0.15 wt% or less, Si: 0.85 to 2.50 wt%, and Mn: 1.0 to 2.0 wt%, followed by annealing. Give,
K and O are K: 0.0001 to 0.0030 wt% and O: 0.020 wt% or less, respectively, and the following equations (1) and (2) 9.0 ≧ (K × 9000) / Si ≧ 1.0 --- (1) 4.0 ≧ After forming an internal oxide layer containing (Si + Mn) / (O × 230) ≧ 1.0 --- (2),
A method for producing a steel wire for CO ₂ gas welding, which comprises pickling, copper plating, and then wire drawing.