JPH1119794A - Steel wire for mag welding and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure a superior bead shape and slag releasability, in addition to arc stability and spatter reduction, in MAG welding. SOLUTION: The elements of 0.15 wt.% or less C, 0.83-2.50 wt.% Si, 0.80-2.0 wt.% Mn, 0.020 wt.% or less O, and 0.0001-0.0030 wt.% K are contained in a range satisfying the formulas, 8.0>=(K×9000)/Si>=1.0 and 3.0>=(Si+ Mn)/(O×230)>=1.0, with the balance essentially consisting of Fe.

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 MAG welding and a method for producing the same, and more particularly to Ar-CO ₂ , Ar-O ₂
So-called MAG using Ar and CO ₂ -O ₂ as shielding gas
In welding, it is intended not only to stabilize the arc and reduce the amount of spatter generated, but also to realize excellent bead shape and slag peelability.

[0002]

_2. Description of the Related Art A welding method using Ar-CO ₂ , Ar-O ₂ and Ar-CO ₂ -O ₂ as a shielding gas has been widely used in various fields such as automobiles, shipbuilding and construction due to the rapid spread of automatic welding. It is used, and its productivity greatly depends on the welding speed. However, the actual welding operation is currently performed at a low speed in order to secure a good bead shape and prevent frequent spatters, and there is a high need for a welding wire capable of performing sound welding even at a high speed.

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

[0004]

As described above, in the welding of thin plates, although 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 a bead shape. In particular, in fillet welding,
In many cases, a smooth and wide weld bead is required, and at the same time, ensuring the slag removability is also an important factor.

The present invention has been developed in view of the above situation. In MAG welding, not to mention stabilization of an arc and reduction of spatters, it is possible to secure an excellent bead shape and a slag peeling property. The aim is to propose a wire together with its advantageous production method.

[0006]

Means for Solving the Problems Now, the inventors have proposed K
MA that achieves low spatter by adding (potassium)
As a result of intensive studies on the purpose of obtaining a wide bead shape and excellent slag peelability while securing the spatter reduction effect of the G welding wire,
The following findings were obtained.

(1) In a wire having K, in order to obtain an excellent bead shape, Si must be 0.83% by weight or more and Mn must be 0.80% or more.
wt% or more and 2.0 wt% or less, (K × 9000) / Si is 1.0
As described above, it is necessary to adjust the amounts of K, Si, and Mn. (2) To obtain excellent slag releasability, Si should be 0.83wt
% Or more and Mn to 2.0 wt% or less, (Si + Mn) / (O × 23
It is necessary to adjust the amounts of Si, Mn, and O so that (0) becomes 1.0 or more. (3) The effect of reducing spatter by adding K is as follows.
(K × 9000) / Si is 1.0 or more and 8.0 or less and (Si +
K, Si, M so that (Mn) / (O × 230) is 3.0 or less.
The effect can be maintained by adjusting the n and O amounts. (4) If Ca is added in an amount of 0.0020 wt% or less, the arc is stabilized, and the spatter is further reduced. (5) When the content of Ti is suppressed to 0.03 wt% or less, high-speed weldability of a thin plate is improved. (6) Regarding the addition of K, an internal oxide layer is formed on the surface of the wire in an inert gas atmosphere during annealing during the wire drawing step, and K is diffused in this layer to stably maintain it as an oxide. Is preferred. (7) Thus, while giving the effect of reducing spatter by the addition of K, it is possible to overcome the adverse effect of the bead shape being convex, and in addition to obtain excellent scale peelability, to improve workability and improve welding performance. High quality can be achieved at the same time. The present invention is based on the above findings.

That is, according to the present invention, C: 0.15 wt% or less, Si: 0.83 to 2.50 wt%, Mn: 0.80 to 2.0 wt%, O: 0.
The following formulas (1) and (2) 8.0 ≧ (K × 9000) /Si≧1.0 --- (1) 3.0 ≧ (Si + Mn) / (O × 230) ) ≧ 1.0 --- (2) The steel wire for MAG welding characterized in that it is contained in a range satisfying (2), and the remainder substantially has a Fe composition, and has a copper plating layer on the surface.

[0009] In the present invention, further in the wire
It is preferable to contain Ca: 0.0020 wt% or less.

[0010] Further, the present invention relates to a method for producing C: 0.15 wt% or less,
An aqueous potassium salt solution is applied to the surface of a steel wire having a composition containing i: 0.83 to 2.50 wt% and Mn: 0.80 to 2.0 wt%, and then annealed to make K and O respectively 0.000 to 0.0001.
-0.0030 wt%, O: 0.020 wt% or less, and the following formulas (1) and (2) 8.0 ≧ (K × 9000) /Si≧1.0 --- (1) 3.0 ≧ (Si + Mn) / (O × 230 ) ≧ 1.0 --- After forming an internal oxide layer containing a range satisfying (2),
This is a method for producing a MAG welding steel wire, which comprises performing pickling, copper plating, and then wire drawing.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reason for limiting the wire composition to the above range in the present invention will be described. C: 0.15 wt% or less C is an element necessary for securing the strength of the weld metal, but if it exceeds 0.15 wt%, the toughness cannot be secured.
The amount was 0.15 wt% or less.

Si: 0.83 to 2.50 wt% Si is an indispensable element mainly as a deoxidizing agent, but spatter increases by its addition, and if it exceeds 2.50 wt%, workability cannot be ensured. On the other hand, Si becomes a slag by welding, and one half of the Si is connected to K in this process, and has a function of preventing a convex bead caused by K. In addition, it has a function of forming a vitreous slag and improving peelability. However, if the content is less than 0.83% by weight, good slag releasability and a smooth bead shape cannot be obtained. Therefore, the amount of Si was limited to the range of 0.83 to 2.50 wt%.

Mn: 0.80 to 2.0 wt% Mn is an element indispensable as a deoxidizing agent and for obtaining high strength and high toughness. Mn, like Si, binds to K in the deoxidation process and has a function of preventing the formation of a convex bead due to K. However, if it is less than 0.80 wt%, a smooth bead shape cannot be secured. On the other hand, excessive addition not only hinders slag vitrification, but also increases the viscosity of the droplets and deposited metal, making it easier to form a convex bead. If it exceeds 2.0 wt%, sufficient slag release and bead shape are required. Can not be secured. Therefore, the amount of Mn was limited to the range of 0.80 to 2.0 wt%.

O: 0.020 wt% or less O, while reducing the amount of spatters generated, tends to increase the oxidation of Fe and Ti and hinder the slag releasability.
If it exceeds 20 wt%, sufficient slag peeling property cannot be secured. Therefore, O was limited to 0.020 wt% or less.

K: 0.0001 to 0.0030 wt% K reduces spatter, but tends to form a thin and convex bead 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%, a sufficiently smooth bead cannot be obtained. Therefore, the amount of K was limited to the range of 0.0001 to 0.0030 wt%. Since K 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 make K exist in the wire. However, it is necessary to use thermal diffusion in the wire drawing process described later. Can be provided effectively.

Although the reasons for limiting the composition range of each component have been described above, it is not sufficient to simply define the composition range of each component as described above in order to achieve the intended object of the present invention. In order to achieve excellent bead shape and slag peelability after realizing low spatter, the following formula
(1) and (2) 8.0 ≧ (K × 9000) /Si≧1.0 --- (1) It is possible to satisfy the relationship of 3.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 --- (2) is important. That is, as a result of various investigations to obtain an excellent bead shape even in high-speed welding in addition to the reduction of spatter by K, 0.83 wt% of Si was obtained.
It is extremely effective to add K so as to satisfy the expression (1) in order to reduce the spatter and obtain a good bead shape, and to add Si and Mn in relation to O, (2)
It has been found that the addition so as to satisfy the formula is extremely effective in reducing spatter and improving slag peelability.

8.0 ≧ (K × 9000) /Si≧1.0 (1) K has a strong bond with the Si oxide, and increases the amount of Si in the steel, and decreases the electrode voltage to increase the arc. The arc stabilizing effect tends to be negated. (K × 9000) / Si
If it is less than 1.0, spatter will increase.If it exceeds 9.0, the effect of K on the arc will be large, the arc length will be long, droplet transfer will be unstable, large spatter will increase, and a convex bead will be formed. Is easy to form. Therefore (K × 90
The value of (00) / Si was limited to the range of 1.0 or more and 8.0 or less.

3.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 (2) When the value of (Si + Mn) / (O × 230) is less than 1.0, the slag peeling property is poor, while the value exceeds 3.0. And the occurrence of sputtering increases. This is because when the amount of Si and Mn is smaller than the amount of O,
This is considered to be because the slag is mainly composed of Fe and Ti, has a strong bonding force with the deposited metal, and has a reduced peelability. On the other hand, if there is much Si and Mn relative to O, a thin oxide centering on Si and Mn is formed in the droplet, which makes the arc unstable and increases the occurrence of spatter.
Therefore, the value of (Si + Mn) / (O × 230) is 1.0 or more and 3.0 or more.
It was as follows.

Although the essential components have been described above, other components described below can be optionally contained in the present invention as needed. Ca: 0.0020 wt% or less Ca is a useful element that stabilizes the arc and reduces the occurrence of spatter. However, if the content exceeds 0.0020 wt%, not only the slag peeling property is impaired, but also the occurrence of spatter Therefore, the content of Ca is set to 0.0020 wt% or less.

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%
Hereinafter, Cr, Ni, Mo, Cu and B are added as necessary for the purpose of securing the strength and the weather resistance of the weld metal. However, since excessive addition causes a decrease in toughness, the content is set in the above range.

At least one selected from Ti, Zr, Al, Nb and V: 0.30 wt% or less Ti, Zr, Al, Nb and V are required for the purpose of securing the strength of the weld metal and securing the weather resistance. Add according to.
However, since excessive addition causes a decrease in toughness, the content is set to 0.30 wt% or less in either case of single addition or composite addition. Especially in welding at high speed,
An excellent bead shape can be obtained by setting the Ti content to 0.03 wt% or less and reducing the viscosity of the droplets 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 each P: 0.030 wt
%, S: 0.035 wt% or less, N: 0.010 wt% or less.

The molten steel prepared to have the above-mentioned preferred composition is preferably made into a billet by continuous casting, and then into a steel wire by hot rolling. Then, after annealing, pickling, copper plating and wire drawing are performed to obtain a product.In the present invention, in the above-described annealing step, an internal oxide layer is formed on the surface layer of the steel strand, It is important that K be contained in this internal oxide layer. Because K
It is extremely difficult to make K exist in the wire because the boiling point is as low as about 760 ° C and the yield in the molten steel stage is extremely low. This is because K can be contained.

As the potassium salt applied to the surface of the steel wire, potassium carbonate, potassium citrate, potassium sulfate, potassium iodide and the like are advantageously suitable. The atmosphere in the annealing treatment is preferably an inert atmosphere such as nitrogen gas. In this inert gas atmosphere, the moisture of the wire, the oxide film on the surface, or a trace amount of oxidizing gas (CO ₂ , H ₂ O, O ₂ ), an internal oxide layer is formed on the surface of the steel wire as shown in FIG. 1, and K is diffused into the internal oxide layer to stably maintain the oxide.

The application of K to the final product or a means of applying K from a wire drawing lubricant is an effective means, although the stability and uniformity of K are somewhat poor. Thereafter, the product may be subjected to pickling, copper plating, and wire drawing according to a conventional method to obtain a product.

[0026]

EXAMPLE A steel bloom (Cu) having the composition shown in Tables 1 and 2 was used.
(Including the adhesion amount by subsequent plating) was made into a steel wire of 5.5 to 7.0 mmφ by hot rolling, and then the wire diameter was set to 2.0 to 2.8 mmφ by cold drawing. Then 2-30
% Aqueous solution of 3 potassium citrate, then O ₂ : 20
0 ppm or less, CO ₂ : 0.1% or less in N ₂ atmosphere (dew point: −
(2 ° C or less) to 750 to 950 ° C, and adjust the wire diameter, potassium salt concentration, and the heating temperature and time to adjust the amount of oxygen and potassium due to the internal oxidation of the wire. Cold drawing was performed, and 0.2 to 1.8 g of lubricating oil was applied per 10 kg of the wire to produce a 1.2 mmφ welding steel wire.

The results of investigations on the amount of spatter generated, the slag peeling property and the bead shape when lap fillet welding was performed using the welding steel wire thus obtained were as follows.
It is shown in Table 3. Incidentally, welding, every minute Ar-20% C0 ₂ as a shielding gas: 20 l flowed at a rate of a pulse power supply (peak current Ip = 460 A, the base current Ib = 60 A, the pulse peak width Tp = 1.1 ms) Using, average current: 260A, voltage: 28V
Under a condition of welding speed: 80 cm / min, lap fillet welding of a 3.2 mm thin steel plate was performed.

The target value of the amount of spatter was set at 0.40 g / min or less. In particular, good (○) was rated at 0.25 g / min or less, acceptable (△) was over 0.25 g / min and 0.40 g / min or less, and unacceptable (×) was over 0.40 g / min. Regarding the slag release property, the target value of the natural release rate was set at 55% or more. Particularly, 70% or more was evaluated as good (良), less than 70% was evaluated as 55% or more (可), and less than 55% was evaluated 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 0.62 or less. In particular, a value of 0.5 or less was rated as good (○), a value exceeding 0.5 and 0.62 or less was rated as good (△), and a value exceeding 0.62 was rated as poor (×).

FIGS. 3 and 4 show (K × 90
FIG. 5 and FIG. 6 show the relationship between (00) / Si and T / W and the amount of spatters generated, respectively, and (Si + Mn) / (O × 23).
0) and the relationship between the slag spontaneous peeling rate and the spatter generation amount.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

As shown in Tables 3 and 4, by controlling the wire composition within the appropriate range of the present invention, the wire composition shown in FIGS.
3 and 5, the bead shape and the slag peeling property were excellent even in high-speed welding as shown in FIGS. Note that Ti
Addition not only causes an increase in the amount of spatter, but also tends to degrade the bead shape and slag peelability.
It is desirable that the content be 0.03 wt% or less.

On the other hand, as in Comparative Examples 33 and 34 (K × 9000)
In the case of /Si<1.0, spattering occurred frequently, and Comparative Example 35,
When (Si + Mn) / (O × 230) <1.0, such as 36, 45, and 49, satisfactory slag release properties could not be obtained. In Comparative Example 37, since the amount of Si was less than 0.83 wt%, satisfactory slag peeling properties and bead shapes could not be obtained. In Comparative Example 38, since the Mn content was less than 0.80 wt%, a satisfactory bead shape could not be obtained. Comparative example
In No. 39, since the Mn content exceeded 2.0 wt%, satisfactory slag release properties and bead shapes could not be obtained. In Comparative Example 40, since the Ca content exceeded 0.0020 wt%, satisfactory slag peeling properties and spatter reduction effects could not be obtained. Further, when (K × 9000) / Si> 8.0 as in Comparative Examples 41 to 42, 46 to 48, and 50 to 52, a satisfactory bead shape cannot be obtained, and in particular, Comparative Examples 41 to 42, 51 In ~ 52,
The amount of spatter generated also increased. When (Si + Mn) / (O × 230)> 3.0 as in Comparative Examples 43 and 44, spattering occurred frequently.

It has been confirmed that the same effect can be obtained with this welding steel wire also in short-circuit transfer welding in a thyristor power supply.

[0037]

As described above, according to the present invention, in MAG welding, an excellent bead shape having excellent arc stability and an extremely small amount of spatter, excellent slag peeling property, and excellent flatness can be obtained.

[Brief description of the drawings]

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

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

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 sputter generation.

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

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

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 38/04 C22C 38/04

Claims (3)

[Claims] C: 0.15% by weight or less, Si: 0.83 to 2.50% by weight, Mn: 0.80 to 2.0% by weight, O: 0.020% by weight or less, K: 0.0001 to 0.0030% by weight, (2) 8.0 ≧ (K × 9000) /Si≧1.0 --- (1) 3.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 --- (2) A steel wire for MAG welding, characterized in that it has a composition of Fe and has a copper plating layer on the surface. 2. The method of claim 1, wherein the wire further comprises C
a: MAG welding steel wire characterized by having a composition containing 0.0020 wt% or less. 3. A potassium salt aqueous solution is applied to the surface of a steel wire having a composition containing C: 0.15% by weight or less, Si: 0.83 to 2.50% by weight, and Mn: 0.80 to 2.0% by weight, followed by annealing. K and O are K: 0.0001 to 0.0030 wt% and O: 0.020 wt% or less, respectively, and the following formulas (1) and (2) 8.0 ≧ (K × 9000) /Si≧1.0 --- (1 ) 3.0 ≧ (Si + Mn) / (O × 230) ≧ 1.0 --- After forming an internal oxide layer containing in a range satisfying (2),
A method for producing a MAG welding steel wire, which comprises performing pickling, copper plating, and then drawing.