JP2009214148A - Consumable-electrode type pulse arc welding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a consumable-electrode type pulse arc welding method capable of sufficiently reducing the generation amount of spatter. <P>SOLUTION: In the consumable-electrode type pulse arc welding method for generating the arc discharge at each pulse by supplying the periodic pulse current between a fore end of an electrode wire and a base material, the current changing rate in a pulse fall area of the pulse current is set to be ≥700 A/ms, and the content of potassium in vegetable oil coated on a surface of the electrode wire is set to be ≥5 mg and ≤50 mg per 10 kg of the wire weight. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a melting electrode type pulse arc welding method, and more particularly to a pulse arc welding method capable of sufficiently reducing the occurrence of spatter.

  There are various types of welding methods such as coated arc welding, gas shielded arc welding, and self-shielded arc welding, and in any case, reducing spatter generation is an important theme. Among such weldings, pulse arc welding classified as gas shielded arc welding has been attracting attention as a welding method that can reduce the heat input to the base material and cause less spattering. That is, by changing the welding current repeatedly in a pulse shape, the average current is low, but a high current can be periodically flowed to obtain sufficient penetration, and by making a special pulse waveform, Attempts have been made to prevent defects and control the penetration shape. For example, Patent Document 1 discloses a pulse that gradually reduces the rising and falling slopes of the current pulse while the welding current is set to the value at the time of main welding from the start of welding, thereby preventing the occurrence of magnetic blowing. An arc welding method is disclosed. According to this welding method, it is said that arc breakage and spatter can be prevented and the arc can be stabilized.

In addition to adjusting the pulse current, as a method of reducing spatter, Patent Document 2 discloses a technique that uses a wire component of a solid wire for arc welding and a lubricant applied to the surface of the wire as a predetermined component. It is disclosed.
JP 2000-670 JP 2006-175451 A

   However, there is a problem that the spatter reduction is still insufficient in the conventional molten electrode type pulse arc welding.

  SUMMARY OF THE INVENTION The present invention solves such a problem, and an object of the present invention is to provide a melting electrode type pulse arc welding method capable of sufficiently reducing the amount of spatter generated.

  In order to achieve the above object, according to the first aspect of the present invention, in the melting electrode type pulse arc welding method of generating an arc discharge for each pulse by supplying a periodic pulse current between the tip of the electrode wire and the base material, The current change rate b in the pulse falling region of the pulse current is set to 700 A / ms or more, and the potassium content a in the vegetable oil applied to the surface of the electrode wire is 5 mg or more and 50 mg or less per 10 kg of the wire. Set.

  As in the first aspect of the present invention, setting the current change rate to a high value of 700 A / ms or more corresponds to making the slope of the pulse fall steep. If the slope of the fall of the pulse is steep and the fall time of the pulse is shortened, the pulse frequency becomes high, resulting in a high frequency current. As a result, the skin effect is enhanced, the current concentrates on the wire surface, and the pinch force that separates the droplet from the wire tip works effectively. Therefore, the detachment of the droplets can be performed smoothly, and the generation of spatter can be reduced. In addition, by setting the potassium content in the vegetable oil applied to the surface of the electrode wire to 5 mg or more and 50 mg or less per 10 kg of the wire, the arc concentrates on the tip of the wire and the arc creeps up. The constriction start position moves from the wire tip to the position above it. As a result, the detachability of the droplets is improved and the spatter can be reduced. The spatter generation amount can be suppressed to 0.3 g / min or less by a synergistic effect by optimization of the current change rate and the potassium content in the vegetable oil applied to the wire surface.

In the second invention, the current change rate b (A / ms) and the potassium content a (mg) are selected from the values in the X region defined by the following equation.
b = 0.014a ⁴ −0.195a ³ +9.659 ² −204.4a + 2300
b-100 ≦ X ≦ b + 100

  As in the second invention, when the current change rate in the pulse falling region of the pulse current and the potassium content in the vegetable oil applied to the surface of the electrode wire are selected from the values in the X region, the amount of spatter generated is 0. .2 g / min or less. The relationship between the current change rate and the potassium content in the vegetable oil applied to the wire surface is not technically clear, but there is a correlation between the spatter generation amount. By performing welding using the value in the X region, the amount of spatter generated can be further reduced than in the first invention.

  As described above, according to the melting electrode type pulse arc welding method of the present invention, the amount of spatter generated can be sufficiently reduced.

  In the melting electrode type pulse arc welding, a welding current is supplied in a pulse shape as shown in FIG. 1 at a repetition frequency of 150 to 200 Hz and supplied to the welded portion. In the figure, Ib is a base current, Ip is a peak current, Zu is a pulse rising region, Zp is a peak region, and Zd is a pulse falling region. While the current pulse rises and maintains a peak, arc discharge occurs between the tip of the electrode wire and the base material, and when the current pulse falls, droplets separate and fall from the tip of the electrode wire into the molten pool of the base material. Then, after arc discharge occurs again at the next current pulse, the droplets are separated and dropped, and this is repeated thereafter. A higher arc voltage at this time can increase the torch height, which is advantageous for reducing spatter. However, in order to prevent the occurrence of an undercut, the arc voltage is usually set in a range that allows a short-circuit transition. In the voltage range thus set, the amount of spatter generated in conventional pulsed electrode arc welding is usually about 1.0 g / min. Therefore, the present invention reduces the amount of spatter generated to 0.3 g / min or less, preferably 0.2 g / min or less in the above voltage range.

  In order to reduce the amount of spatter generated to 0.3 g / min or less, the current change rate in the pulse falling region Zd is set to 700 A / ms or more. This is because if it is less than 700 A / ms, the arc becomes unstable. Specifically, when the current change rate is less than 700 A / ms, the slope of the falling edge of the pulse becomes gentle and the pulse frequency becomes low. As a result, the skin effect is weakened, the pinch force is lowered, the detachment of the droplets becomes irregular, and a lot of spatter is generated. Although there is no restriction | limiting in particular about the upper limit of an electric current change speed, About 1500 A / ms is a limit in the commercially available pulse welding power supply. And simultaneously with making the said current change rate into 700 A / ms or more, vegetable oil is apply | coated to the surface of an electrode wire, and potassium content in the said vegetable oil is set to 5 mg or more per 10 kg of wires. If it is less than 5 mg, the arc becomes unstable. The upper limit of the potassium content is preferably 50 mg or less per 10 kg of wire. If the potassium content exceeds 50 mg, the fatty acid alkali salt separates from the vegetable oil and precipitates. This is because the solubility limit is exceeded. The solid matter thus precipitated adheres to the wire surface. When welding is performed with the welding wire in this state, solids may aggregate in the conduit cable or welding torch on the wire feeding path, which may cause a wire feeding failure. When the potassium content is in the range of 5 mg to 50 mg, the detachability of the droplets is improved and the spatter is reduced. In addition, as an electrode wire, those for mild steel and high-tensile steel, for example, YGW15 (JIS Z3312), those for stainless steel, etc. can be used, and rapeseed oil etc. can be used as vegetable oil.

After all, the current change rate in the pulse falling region Zd and the value of potassium content in the vegetable oil are shown in the region Y surrounded by the square in FIG. 2, that is, the current change rate is 700 A / ms or more and 1500 A / ms or less, and the potassium content When the amount is set within the range of 5 mg or more and 50 mg or less, the spatter generation amount can be greatly reduced to 0.3 g / min or less. At this time, if the current change rate and the potassium content are selected and set from the values in the region X represented by the following formula in the region Y, the amount of generated spatter is further suppressed to 0.2 g / min or less. Can do. In the following formula, a is the potassium content (mg), and b is the current change rate (A / ms).
b = 0.014a ⁴ −0.195a ³ + 9.659a ² −204.4a + 2300
b-100 ≦ X ≦ b + 100

  The end edges of two cold-rolled steel plates (SPCC) 1 and 2 for welding having a thickness of 2 mm were overlapped as shown in FIG. 3, and overlapped fillet welding by mag pulse arc welding was performed on the portion indicated by the arrow. The electrode wire used was JIS Z3312 YGW15 or equivalent, and Ar + 20% CO2 shielding gas was supplied to the weld at a flow rate of 20 L / min. The arc voltage was 25 V, the repetition frequency of the welding pulse current was 200 Hz, the average current was 200 A, the base current Ib was 45 A, and the peak current Ip was 450 A. The welding speed was 100 cm / min, and the tip-base metal distance was 15 mm.

  Various changes were made in the rate of current change in the pulse falling region and the potassium content in the vegetable oil, and pulse arc welding for 14 seconds was repeated three times inside the copper enclosure for each. This copper enclosure is a jig for collecting spatter. Spatter generated during welding was collected by brushing and converted to a spatter generation amount per minute. The results are shown in Tables 1 and 2. In the table, the double circles in the “Evaluation” column indicate that the spatter generation amount is 0.2 g / min or less, and the single circles indicate that the spatter generation amount is 0.3 g / min or less. The symbols indicate the cases where the amount of spatter generated is greater than 0.3 g / min.

(Example)
In Examples 1 to 6 in Table 1, the potassium content in the vegetable oil per 10 kg of wire is 5.0 mg, and the current change rate in the pulse falling region Zd (FIG. 1) is 6 to 700 A / ms to 1500 A / ms. Changed in stages. In this case, the amount of spatter generated was 0.3 g / min or less, and good results were obtained. In particular, when the potassium content and the current change rate were set to the values in Example 6, the amount of spatter generated was 0.2 g / min or less. The values of potassium content and current change rate are values in the X region of FIG.

  In Examples 7 to 12 in Table 1, the potassium content in the vegetable oil per 10 kg of wire is 12.3 mg, and the current change rate in the pulse falling region Zd is changed in six steps from 700 A / ms to 1500 A / ms. It was. In this case, the amount of spatter generated was 0.3 g / min or less, and good results were obtained. In particular, when the potassium content and the current change rate were the values of Examples 9 and 10, the amount of spatter generated was 0.2 g / min or less. The values of potassium content and current change rate are values in the X region of FIG.

  In Examples 13 to 18 in Table 1, the potassium content in the vegetable oil per 10 kg of wire is 20.7 mg, and the current change rate in the pulse falling region Zd is changed in six steps from 700 A / ms to 1500 A / ms. It was. In this case, the amount of spatter generated was 0.3 g / min or less, and good results were obtained. In particular, when the potassium content and the current change rate were the values of Examples 13 and 14, the amount of spatter generated was 0.2 g / min or less. The values of potassium content and current change rate are values in the X region of FIG.

  In Examples 19 to 23 in Table 1, the potassium content in the vegetable oil per 10 kg of the wire is 33.6 mg, and the current change rate in the pulse falling region Zd is changed in five steps from 700 A / ms to 1500 A / ms. It was. In this case, the amount of spatter generated was 0.3 g / min or less, and good results were obtained. In particular, when the potassium content and the current change rate were the values of Examples 19 and 20, the amount of spatter generated was 0.2 g / min or less. The values of potassium content and current change rate are values in the X region of FIG.

  In Examples 24-28 of Table 1, the potassium content in the vegetable oil per 10 kg of wire is 50.0 mg, and the current change rate in the pulse falling region Zd is changed in five steps from 700 A / ms to 1500 A / ms. It was. In this case, the amount of spatter generated was 0.3 g / min or less, and good results were obtained. In particular, when the potassium content and current change rate were set to the values in Example 24, the amount of spatter generated was 0.2 g / min or less. The values of potassium content and current change rate are values in the X region of FIG.

(Comparative example)
On the other hand, as shown in Comparative Examples 1 to 3, when the potassium content in the vegetable oil per 10 kg of wire is set to 0, the amount of spatter generated even if the current change rate in the pulse falling region Zd is 700 A / ms or more. Is 0.54 g / min or more, and good results cannot be obtained.

  Further, as shown in Comparative Examples 4 to 6, when the potassium content in the vegetable oil per 10 kg of the wire is 3.6 mg, the amount of spatter generated is not limited even if the current change rate in the pulse falling region Zd is 700 A / ms or more. It becomes 0.39 g / min or more, and good results cannot be obtained.

  On the other hand, as shown in Comparative Examples 7 to 9, even when the potassium content in the vegetable oil per 10 kg of the wire is 5.0 mg, the current change rate in the pulse falling region is in the range of 300 A / ms to 670 A / ms. The amount of spatter generated is 0.61 g / min or more, and good results cannot be obtained.

  Further, as shown in Comparative Examples 10 to 12, even when the potassium content in the vegetable oil per 10 kg of the wire is 12.3 mg, the current change rate in the pulse falling region Zd is in the range of 300 A / ms to 670 A / ms. Then, the spatter generation amount is 0.49 g / min or more, and a good result cannot be obtained.

  As shown in Comparative Examples 13 to 15, even when the potassium content in the vegetable oil per 10 kg of the wire is 20.7 mg, sputtering is performed when the current change rate in the pulse falling region Zd ranges from 300 A / ms to 670 A / ms. The amount generated is 0.33 g / min or more, and good results cannot be obtained.

  Furthermore, as shown in Comparative Examples 16 to 18, even if the potassium content in the vegetable oil per 10 kg of wire is 33.6 mg, the current change rate in the pulse falling region is in the range of 300 A / ms to 670 A / ms. The amount of spatter generated is 0.32 g / min or more, and good results cannot be obtained.

  As shown in Comparative Examples 19 to 21, even when the potassium content in the vegetable oil per 10 kg of wire is 50.0 mg, spatter is generated when the current change rate in the pulse falling region is in the range of 300 A / ms to 670 A / ms. The amount is 0.33 g / min or more, and good results cannot be obtained.

  In addition, as shown in Comparative Examples 22 to 24, when the potassium content in the vegetable oil per 10 kg of the wire is 53.4 mg exceeding 50.0 mg, the current change rate in the pulse falling region Zd is 700 A / When the range is from ms to 1000 A / ms, a good result is obtained with a sputter generation amount of 0.24 g / min or less, but precipitation of potassium that may block the wire feeding portion occurs.

  Similarly, as shown in Comparative Examples 25 to 27, when the potassium content in the vegetable oil per 10 kg of the wire is 62.8 mg exceeding 50.0 mg, the current change rate in the pulse falling region Zd is 700 A. When the range is from / ms to 1000 A / ms, the sputter generation amount is 0.26 g / min or less, and a good result is obtained, but precipitation of potassium that may block the wire feeding portion occurs.

  As described above, according to the molten electrode type pulse arc welding method of the present invention, the current change rate in the pulse falling region of the pulse current and the potassium content in the vegetable oil applied to the surface of the electrode wire are adjusted. Thus, the pinch force and the creeping of the arc can be optimized. As a result, the detachability of the droplet from the tip of the welding wire can be improved, and the occurrence of spatter can be reduced. Moreover, it is possible to realize further reduction of spatter by performing welding using the value in the X region as in the second aspect of the invention, instead of simply increasing the current change rate and increasing the content. Can do.

It is a figure which shows a pulse current waveform. It is a figure which shows the relationship between potassium content and electric current change speed. It is sectional drawing of a welding part.

Claims (2)

In a melting electrode type pulse arc welding method in which an arc discharge is generated for each pulse by supplying a periodic pulse current between the tip of an electrode wire and a base material, a current change rate b in a pulse falling region of the pulse current is set to In addition to being set to 700 A / ms or more, the content a of potassium in the vegetable oil applied to the surface of the electrode wire is set to 5 mg or more and 50 mg or less per 10 kg of the wire. Method. 2. The electrode type pulsed arc welding method according to claim 1, wherein the current change rate b (A / ms) and the potassium content a (mg) are set to values in the X region defined by the following equation.
b = 0.014a ⁴ −0.195a ³ +9.659 ² −204.4a + 2300
b-100 ≦ X ≦ b + 100

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