JPH0451274B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a steel wire for arc welding that has good feedability and excellent welding workability with less spatter. Copper-plated welding wire with a diameter of 0.8 to 2.4 mm is generally used for CO ₂ gas shield welding, MIG welding, etc. These welding wires are usually used for welding with a spool wound around a bobbin or loaded into a cylindrical container called a pail pack. When these wires are used, the wires in the above condition are attached to the feeder, which is an accessory attachment of the welding machine, and passed through the feed roller to the flexible conduit tube, welding torch, and contact tip, which are 3 to 20 meters long. In many cases, it is used for welding. In this type of welding, the wire is required to be fed at a constant speed, but the wire is susceptible to contact resistance with the guide tube of the flexible conduit, such as the liner, torch, and tip. Resistance forces act on the welding wire as it passes through the bent portions of the tube, so if these resistance forces become large, the feeding speed of the welding wire becomes uneven, and eventually the feeding stops. As a result, various welding defects such as unstable welding arc, irregular bead shapes, poor fusion, and undercuts occur. Recently, as welding work has become more complex, faster, and wider, welding wire that has low frictional resistance with the flexible conduit liner, is smooth and stable, and is always fed at a constant speed. There has been an increasing demand for welding wires with good properties. Conventionally, in order to improve wire feeding performance, efforts have been made to increase the feeding power of a feeder or to improve the feeding performance of the wire itself.
For example, in order to improve the feeding performance of the wire itself, methods are being used to apply liquid lubricant to the wire surface to increase the lubrication ability of the wire surface and reduce feeding resistance. No evidence of feedability was obtained. The reason for this is that it is difficult to apply liquid lubricant uniformly and stably to the surface of the copper-plated wire, and in order to achieve the desired performance,
This is because a large amount of lubricating oil had to be applied. In addition, lubricating oil applied to the wire surface in an excessive amount than necessary may cause changes in the material of the welded part,
Alternatively, it is known to have an adverse effect on welding workability. There is also a method of forcibly pressurizing the wire surface to change the surface roughness and reduce contact resistance, but the effect is similar to the effect of improving feedability by applying lubricating oil as described above. , still not satisfactory. On the other hand, carbon dioxide gas shield welding (hereinafter referred to as CO ₂ welding) has the advantages of high efficiency and low cost, but on the other hand, the welding efficiency decreases due to the phenomenon of frequent scattering of molten droplets called spatter during welding, and they adhere to the gas nozzle. This has caused major problems, such as the occurrence of welding defects due to the impediment of gas shielding properties, and furthermore, the removal of spatter requires labor. This sputtering phenomenon is particularly noticeable under welding conditions in a relatively large current range of 250 A or more, and the conventional techniques to reduce it include 1) improving the welding power source characteristics, 2) changing the shielding gas composition, and 3) Additions of alloying elements have been made. 1) is intended to improve the output characteristics, rectification method, power supply, wire feeder control method, etc. of the CO ₂ welding machine. However, since the generation of spatter is essentially caused by the arc phenomenon of CO ₂ welding, it has its own limitations. 2) is an effective method, in which the shielding gas is changed from CO ₂ to mainly Ar gas, which is an inert gas, to stabilize the arc and reduce the occurrence of spatter. Although it is an effective method, it has the drawback of high cost. There is. 3) is carried out by adding an alloying element to the wire; for example, the effect of adding Ti is disclosed in Japanese Patent Publication No. 3256/1983. Also as is well known
It is standardized as YCW1 in JISZ3312 and is widely used. However, none of the conventional wires described above is sufficient to solve the problem of spatter generation as described above. As mentioned above, the wire feedability in CO ₂ welding and MIG welding, and especially the reduction of spatter under high current range welding conditions in CO ₂ welding, are
Both conventional techniques had problems, and new techniques were needed. The present inventors have been conducting research for a long time to solve the problem from various viewpoints, and found that by forming an internal oxidation layer on the welding wire, not only the wire feedability but also CO ₂ welding can be improved. We have succeeded in developing a welding wire that does not generate spatter even when welding in a large current range. As is well known, by controlling the material composition and oxidation conditions, internal oxidation of a metal material can be carried out without external oxidation. That is, after internally oxidizing the welding wire, there is an advantage that copper plating can be applied to the wire surface by simple pickling. Moreover, when wire is drawn after copper plating, tortoiseshell-like cracks occur on the copper plating surface.
This allows the lubricating oil to accumulate appropriately and dramatically improves feeding performance. Furthermore, when the amount of effective oxygen in the welding wire brought about by internal oxidation is 40 to 300 ppm, the occurrence of spatter is significantly suppressed. The effective oxygen amount referred to here is the value obtained by subtracting the oxygen amount of the wire material from the oxygen amount (total oxygen amount) obtained by oxygen analysis after copper plating the internally oxidized welding wire. . Effective oxygen amount = (total oxygen amount in the welding wire) - (oxygen amount in the wire material) In other words, the present invention solves the problem of improving welding wire feedability and reducing the amount of spatter by changing the oxygen existence form of the wire and the oxygen This problem was solved by a new technical idea that is different from the conventional technology of intentionally adjusting and regulating the amount. That is, the gist of the present invention is that in weight %, C:
0.06~0.15%, Mn: 1.0~2.5%, Si: 0.5~3.0%
or further contains Ti: 0.05 to 0.40
%, Cr: 0.5-1.0%, Al: 0.05-0.5%, however, the total of two or more of Ti, Cr, and Al is 2.0% or less, and the remainder is Fe and unavoidable in steelmaking. It consists of impurity elements, has tortoise shell-like or scratch-like cracks on the copper plating surface, and has an effective oxygen amount of 40 to 300 ppm as defined by the following formula, and the effective oxygen amount is provided by the internal oxidation layer. This is a steel wire for arc welding that has excellent welding workability. Effective oxygen amount = (total oxygen amount of welding wire) - (oxygen amount of wire material) The present invention will be explained in detail below. Figure 1 shows the state of the internal oxidation layer of the wire of the present invention.
A sketch of a 1.2 mm diameter wire polished diagonally and observed with a metallurgical microscope at 400x magnification (tilt angle
6°). A is a conventional wire without an internal oxidation layer, and b is a wire of the present invention in which an internal oxidation layer can be seen from the wire surface toward the inside. Here, the reason for specifying the effective oxygen amount is
This is because if it exceeds 300 ppm, the oxide concentration in the internal oxidation layer on the wire surface becomes excessive, the copper plating properties deteriorate, and the copper plating peels off during wire drawing. Also
If it is less than 40 ppm, the hexagonal cracks necessary for retaining lubricating oil on the plating surface will be insufficient, and at the same time, the effect against spatter will not be observed. FIG. 2 is a sketch (magnification x 100) showing the aforementioned tortoise-shell-shaped crack observed under a metallurgical microscope. a
b is the surface of a conventional wire with an effective oxygen amount of 20 ppm, and b is the surface of the wire of the present invention, where the internal oxidation layer provides an effective oxygen amount of 150 ppm. Next, alloying elements C, Si, Mn and Cr, Al,
The reason for specifying the Ti content will be explained. Originally, an internal oxidation layer is ideally formed in a welding wire that contains a specific amount of an alloying element that has a stronger affinity for oxygen than iron. These elements include Si, Mn, Al,
There are Cr, Ti, etc., and each needs to be contained in an appropriate amount depending on the purpose. When C is less than 0.06%, the total amount of spatter does not change, but large spatter occurs.
Large particles of spatter adhere strongly to the nozzle and near the welding area, and problems with spatter removal occur frequently. Therefore, the C content is set at 0.06 to prevent this.
% or more. When the temperature was 0.06%C or higher, droplet transfer in the large current range became smoother, and spatter was slightly reduced. This is thought to be because the CO reaction in the droplets and molten pool becomes active during the CO ₂ welding arc. However, if the C content of the wire exceeds 0.15%, the C content of the weld metal will increase, the tensile strength will be high, the elongation will decrease, and the impact toughness will decrease, so C
Limited to the following. Si is an essential element for forming an internal oxidation layer on the steel wire surface. When Si is less than 0.5%, the oxygen potential of the controlled atmosphere is increased by ₁ × with Po2.
Even when heated within the range of 10 ^-16 atm to 1 x 10 ^-23 atm, the formation of an internal oxidation layer is extremely weak, the amount of effective oxygen is less than 40 ppm, the wire feedability is deteriorated, and large particles are formed. Not only will spatter occur, but
The Si content in the CO ₂ weld metal decreases, and pits begin to appear on the weld bead surface. Si is 0.5
% or more, especially 0.7% or more, the formation of an internal oxidation layer becomes noticeable, the amount of effective oxygen increases, and tortoise shell-like cracks are formed on the wire surface, which not only improves wire feedability but also reduces spatter. significantly reduced. However, when Si exceeds 3.0%, the formation of an internal oxide layer is rather suppressed, and the formation of an external oxide layer becomes significant, resulting in a marked decrease in plating adhesion and an increase in wire feeding resistance. Therefore, welding workability deteriorates. Therefore, Si was set at 0.5 to 3.0%, preferably 0.7 to 2.0%. When Mn exceeds 1.0%, Si exceeds 0.5%, especially 0.7%.
% or more, it promotes the formation of an internal oxide layer, but
When Mn exceeds 2.5%, the amount of Mn in the weld metal increases,
As a result, hardness increases. Therefore, the elongation is reduced and the impact toughness is also reduced. Moreover, when Si exceeds 3.0%, Mn exceeding 2.5% forms MnSiO ₃ on the steel wire surface.
and promotes the formation of an external oxide layer.
The range of Mn was 1.0 to 2.5%, preferably 1.5 to 2.5%. Next, while satisfying the above-mentioned ranges of C, Si, and Mn, one of Ti, Cr, and Al is added to Ti:
0.05-0.40%, Cr: 0.5-1.0%, Al: 0.05-0.5%
Contains, however, the total of two or more of Ti, Cr, and Al
When it is set to 2.0%, it has the effect of making the formation of an internal oxidation layer more pronounced. Below this range, there is almost no effect on the internal oxide layer, and above the upper limit of the above range, the formation of the external oxide layer is promoted rather than the internal oxide layer, and as a result, the adhesion of plating is significantly reduced. It deteriorated and the feedability decreased significantly. Next, the effects of the present invention will be explained in more detail with reference to Examples. Example 1 A sample having a chemical composition of C, Si, Mn, Cr, Al, and Ti as shown in Table 1 was melted and finished into a 2.2 mm wire through forging and wire drawing processes. . These wires were annealed in a CO-CO ₂ controlled atmosphere furnace shown in Table 2 to form an internal oxide layer, then pickled (HCl 10%, 60°C), copper plated, and drawn to 1.2 mm. The welding workability was evaluated using the following wire. Table 3 shows CO/CO ₂ = 2.5/1 atmosphere at 800℃ x 120
The thickness of the internal oxidation layer, the amount of effective oxygen, the feedability, and the amount of spatter generated in the annealed wire are shown. The amount of spatter generated was collected using a spatter collection box, and the feedability was determined by measuring the armature current value of the wire feed motor.The feedability was judged to be acceptable if the current value was 2A or less. Table 4 shows the measurement conditions. FIG. 3 is an explanatory diagram showing the relationship between the amount of effective oxygen and the amount of spatter in Table 3. In the figure, a broken line a indicates a copper plating defect. First, as shown in Figure 3, the amount of effective oxygen is
Below 40ppm and above 300ppm, the amount of spatter increases rapidly to over 4gr/min (Table 3 No.
28, No. 31, No. 33, No. 36), less than 40 ppm, the third
As shown in Tables No. 3, No. 4, and No. 8, no cracks were observed on the wire surface, and the feeding performance deteriorated. On the other hand, even if the amount of effective oxygen is 40 to 300 ppm and there is hexagonal cracking, if the chemical composition of the wire is outside the range of the present invention, a decrease in workability is observed. (Table 3 No. 1, No. 2, No. 12, No. 16, No. 21) Example 2 Using sample No. 6, CO/CO ₂ was 2.5/1, 4/1
Evaluate the effective oxygen amount, plating adhesion, surface cracking, feedability, and spatter amount of wires annealed at 700°C, 800°C, and 900°C for 8 minutes, 60 minutes, and 120 minutes in a 6/1 atmosphere. did. (The welding conditions are the same as in Table 4.) Table 5 shows the results obtained. By adjusting the CO/CO ₂ ratio to 2.5/1 to 6/1 and controlling the temperature and time within a specific range, we can improve feedability.
It can be seen that excellent results can be obtained in both the amount of spatter.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】 [Brief explanation of the drawing]

Fig. 1 is a sketch (magnification x 400) showing the cross-sectional state of the wire of the present invention, where a is a conventional wire, b is a wire of the invention, and Fig. 2 is a sketch showing the surface state of the wire of the invention (magnification x 100). ), a is the conventional wire, b is the inventive wire, and FIG. 3 shows the effective oxygen amount (ppm) and spatter amount (gr/
This is a chart showing the relationship between

Claims (1)

[Claims] 1 C: 0.06 to 0.15% (same below weight%), Mn:
Contains 1.0 to 2.5%, Si: 0.5 to 3.0%, and the remainder is
It is composed of Fe and unavoidable impurity elements, has hexagonal or scratch-like cracks on the copper plating surface, and has an effective oxygen amount of 40 to 300 ppm as defined by the following formula, and the effective oxygen amount is within the internal oxidation layer. A steel wire for arc welding that has excellent welding workability and is characterized by: Effective oxygen amount = (total oxygen amount in welding wire) - (oxygen amount in wire material) 2 C: 0.06 to 0.15% (same below weight%), Mn:
Contains 1.0 to 2.5%, Si: 0.5 to 3.0%, and further
Ti: 0.05~0.40%, Cr: 0.5~1.0%, Al: 0.05~
Contains 0.5% of any one or more of Ti,
The total of two or more of Cr and Al is 2.0% or less, the remainder is Fe and unavoidable impurity elements, the copper plating surface has hexagonal or scratch-like cracks, and the effective oxygen content is defined by the following formula. The amount is 40~300ppm
A steel wire for arc welding which has excellent welding workability and is characterized in that the effective oxygen amount is provided by an internal oxidation layer. Effective oxygen amount = (total oxygen amount in welding wire) - (oxygen amount in wire material)