JPH0521674B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a welding wire used in semi-automatic welding such as MIG welding, MAG welding (including CO ₂ welding), or automatic welding, and particularly relates to a welding wire used in semi-automatic welding such as MIG welding, MAG welding (including CO 2 welding), or automatic welding. Regarding good wire. [Prior art] Generally, welding wire used for MIG welding, MAG welding (including CO ₂ welding), etc. is wound around a spool made of synthetic resin or the like in units of 10 kg or 20 kg, or is used in large quantities. As,
Stored in a pail can weighing over 200Kg. This welding wire is fed to the welding part through the conduit tube by a feed motor so as to meet predetermined welding conditions. In recent years, in the welding field, due to demands for higher efficiency and labor savings, locations where covered arm welding rods were conventionally used are also being replaced by semi-automated or automated welding. Particularly in the fields of industrial machinery and automobiles, the amount of automatic welding wire used is increasing due to advances in welding robots. Furthermore, in the field of shipbuilding, the proportion of semi-automatic welding has increased, leading to an increase in the amount of welding wire used. When welding wire is used in the shipbuilding process, the welding area is spread over a wide area, so the welding wire has to pass through a long conduit tube. It is appearing. In order to perform good welding even in such cases, it is essential to feed the welding wire smoothly. If the smooth feeding of the welding wire is hindered due to friction with the conduit tube, sound welding becomes difficult, resulting in poor penetration of the welded part,
Welding defects such as meandering of the weld bead and increased spatter occur. Conventionally, in order to improve the feedability of welding wire, recesses and cracks are formed on the surface of welding wire and lubricating oil is applied, as disclosed in Japanese Patent Application Laid-open Nos. 54-141349 and 1982-128294. something is proposed. However, the feedability was not sufficiently improved and the surface condition was non-uniform, making it impossible to obtain a product of satisfactory quality. Furthermore, in JP-A-59-61592, the wire surface has a hexagonal crack, which limits the effective oxygen content of the wire. Even in this case, it is effective for short-time welding, but when used for a long time, such as at a welding work site, residues such as copper powder accumulate inside the conduit tube, which obstructs wire feeding and It was discovered that there were problems leading to poor pay. The present inventors conducted a detailed investigation into clogging caused by residual copper powder, and found that the crystal grains and grain boundary oxidation layer in the surface layer of the copper-plated base, that is, the iron base of the wire, have a large influence. I found out that there is. In other words, if the value obtained by dividing the average grain boundary oxidation layer on the wire surface by the average crystal grain size on the wire surface (hereinafter referred to as A value) is large, the grain boundaries will be completely oxidized and the conduit tube will be damaged when the wire is fed. It was found that the copper plating peeled off due to rubbing against the inner wall. Here, the average grain boundary oxidation layer refers to the average of the intergranular oxidation layer obtained by taking samples randomly from five locations within the same charge of a wire that has undergone intermediate annealing, and measuring the grain boundary oxidation layer seen from the cross section of each wire. and
The average crystal grain size is obtained by taking samples in the same manner as above, measuring the surface grain size in the cross-sectional direction of the wire, and averaging the results. Furthermore, JP-A-58-3797 attempts to improve welding workability by attaching activating elements, that is, alkali metals and alkaline earth metals, to the wire surface, but the application method is not clear.
When actually manufactured, the welding arc was unstable and unstable due to non-uniform adhesion on the surface of a normal wire. That is, in such cases, it has been found that the wire base is greatly affected and it is necessary to have a wire base that can be coated uniformly. [Problems to be Solved by the Invention] The present invention has been proposed in order to solve the problem of copper powder and other residues accumulating in a conduit tube and causing poor wire feeding, and to further improve arc stability. This allows for smooth feeding even when the conduit tube is long during semi-automated or automated welding, and there is less copper powder generated in the conduit tube and less clogging even during long welding. The object of the present invention is to provide a welding wire with good feedability and excellent welding workability. [Means for Solving the Problems] The present invention limits the amount of C and Ti in the wire components, and appropriately selects the annealing conditions during intermediate annealing in the wire manufacturing process, thereby improving the surface layer of the wire. The crystal grain size and grain boundary oxidation layer are formed within appropriate ranges. That is, C is 0.02 ~
In a welding wire containing 0.06% by weight and 0.03 to 0.30% by weight of Ti, the ratio A of the grain boundary oxidation layer generated on the wire surface layer during intermediate annealing to the crystal grains is as follows: A = average grain boundary oxidation layer thickness (μm )/average grain size (μ
m), characterized in that A is 0.4 or more and 1.8 or less,
The product diameter has fine grooves uniformly distributed on the surface, and the inside of the grooves and the wire surface contain lubricating oil and an arc stabilizer such as an alkali metal or alkaline earth metal. This is a welding wire with excellent welding properties and good welding workability. Such a welding wire can be obtained by appropriately selecting intermediate annealing conditions. [Operation] In order to solve the above problems, after continuous welding 100 kg of wire before improvement under the conditions shown in Table 1 below,
Analysis and investigation of the residual copper powder in the conduit tube revealed that it was approximately 40% by weight copper and 60% iron. In other words, the residue inside the tube was a mixture of iron powder and copper powder, and upon closer observation, it was found that the iron and copper existed in a combined state. This indicates that when the wire is rubbed in the conduit tube, the iron substrate is peeled off from the wire substrate along with the copper plating layer. Table 1 Wire: YGW11 Wire diameter: 1.2mmφ Welding position: downward Welding current: 300A Welding voltage: 30V Welding speed: 20cm/min Shielding gas: CO ₂ 20/min Conduit tube status Tube length: 3m Loop diameter: 200mmφ1 Circle Figure 2 shows the relationship between the amount of carbon in the wire and the crystal grains on the surface of the wire, and the crystal grains increase as the amount of carbon decreases. This means that when the amount of carbon in the wire is low, the crystal grains become large. In other words, the amount of carbon in the wire component is
If it is 0.06% by weight or less, the crystal grains are large, so even if grain boundary oxidation occurs, the amount of Cu powder falling off will be reduced, and the A value will be easily controlled. FIG. 3 shows the relationship between the amount of carbon and the amount of copper powder generated, and the above-mentioned circumstances are clear. Note that FIG. 3 shows the relationship between the amount of carbon and the amount of copper powder generated. As the carbon content decreases, the crystal grain size increases, so the occurrence of grain boundary oxidation changes, and the 0.06%
Below, the occurrence of copper powder is decreasing. By the way, the reason why the lower limit of the C value is limited to 0.02% by weight is that if it is less than 0.02% by weight, the performance of the welded metal part will deteriorate. This is because the grains become too large, resulting in frequent occurrence of wire surface flaws during wire drawing. Next, Figure 1 shows the A value after intermediate annealing with atmosphere control, and the amount of copper powder generated in the conduit tube when this wire is copper plated, drawn to the product diameter, and then welded. This shows the relationship between As is clear from Figure 1, the A value is 0.4~
Copper powder generation is reduced within the range of 1.8. The reason for this will be explained with reference to FIG. FIG. 4 schematically shows the state of crystals in a cross section in the depth direction of the wire surface layer. Diagrams a to d are respectively Diagram a: Schematic diagram of crystal with A value = 0.7 after intermediate annealing Diagram b: Schematic diagram of crystal after cold wire drawing of the one in Diagram A Diagram c: Crystal with A value = 2.1 after intermediate annealing Schematic diagram d: This is a schematic diagram of crystalline crystals after cold wire drawing of the one shown in diagram c. In the figure, 1 indicates copper plating, and 2 indicates grain boundary oxidation. As shown in the schematic diagram of Figure 4, the A value of the surface layer is
If it exceeds 1.8, grain boundary oxidation occurs on the entire grain boundary,
This grain boundary oxidation part is easy to peel off, so when welding using wire drawn to the product diameter after copper plating,
It is thought that when the wire rubs inside the conduit tube, the copper plating and the iron base attached to it will peel off at the same time. However, when the A value is between 0.4 and 1.8, grain boundary oxidation does not extend over the entire surface of the crystal grains, so it is considered that peeling is difficult. If the A value is less than 0.4, the lubricating oil retaining function on the wire surface does not work sufficiently, so it is thought that the oil film will run out during feeding, resulting in poor feeding and increased generation of copper powder. In this way, it was confirmed that the A value greatly affects the generation of Cu powder, wire feedability, and arc stability, but as is clear from Figure 2, it is important to control the A value within the range. As a result of the study, it has become clear that it is effective to make the crystal grains coarser, that is, to reduce C, in order to simplify the process and reduce the amount of copper powder generated. When C is reduced, if the atmosphere is controlled such as by adjusting the dew point, it is easier to control the progress of grain boundary oxidation, the range of atmosphere adjustment becomes wider, and because the crystal grains are large, grain loss is reduced and copper An example of this is a reduction in powder generation. That is, when C is high, crystal grains become small and, conversely, more copper powder is generated. This is considered to be the effect of grain loss, and is supported by Fig. 3. The A value is specified to ensure uniform oil application to the wire surface, but in normal processes,
The wire is first drawn from a 5.5φ original wire to an intermediate diameter of 2.0φ, annealed to soften the work-hardened wire, and then copper plated and drawn to the product diameter. In the method of the present invention, the atmosphere is controlled in the softening annealing process during wire drawing, and after controlling the A value range, the wire is drawn, so that the grain boundary area is Cracks occur. This provides a base that sufficiently retains lubricating oil. Next, the reason for limiting the amount of Ti will be described. When welding using a welding wire, especially when welding with a welding robot, it is sufficient to withstand use even if the A value is satisfied in the short circuit transition region, but
In the droplet transfer region at high currents, variations in arc stability and arc length greatly affect the generation of spatter, which becomes a problem during long-term welding. In this case, it has been confirmed that Ti has a large effect on reducing spatter. A good range is 0.03% by weight to 0.30% by weight. If it is less than 0.03% by weight, the effect of reducing the arc force will be small and the separation from the molten end of the wire will be large and irregular. this is,
This is due to the fact that the semiconductor effect due to TiO ₂ on the droplet surface is reduced and the arc force is concentrated in a small part of the droplet. If Ti exceeds 0.30% by weight, the viscosity of the molten metal becomes too high and the bead shape becomes convex, so the upper limit is set to 0.30% by weight. Next, adding arc stabilizers such as alkali metals or alkaline earth metals to the lubricating oil that is applied on the wire surface or penetrated into the grooves on the wire surface is recommended to improve welding workability. In addition to the effect of improving wire feedability due to the reduction of copper powder and the effect of reducing arc force due to the addition of Ti, we also considered the conditions of arc occurrence. That is, on the wire surface, these elements, that is, elements with low ionization voltage, such as K ⁺ (K ₂ CO ₃ ), Cs ⁺
(Cs ₂ CO ₃ ) or the like has a low ionization energy, making it easier to ionize electrons and generate arcs more smoothly. In other words, it is thought that since the tendency of the arc to creep up to the wire surface increases, the concentration of the arc on the wire end is reduced, and the scattering of spatter is reduced. The amount of coating is preferably 100 ppm or less since too much will cause problems with wire feedability and rust prevention properties of the wire. The coating method may be skin pass wire drawing using a mixed liquid of lubricating oil and arc stabilizer during finishing wire drawing. Next, Table 2 shows the results of investigating the effect on welding workability when welding was performed under the conditions shown in Table 1 above using 100 kg of wire having various conditions. The amount of spatter generated was determined by placing a stringer bead on a 300 mm x 200 mm test piece using a bead-on plate, and measuring the number of spatters of 0.5 mm or more. Wire components are C: 0.02 to 0.06% by weight, Ti: 0.03
~0.30% by weight, with an A value between 0.4 and 1.8, the fine particles uniformly distributed on the wire surface contain lubricating oil with rust prevention properties and arc stabilizers such as alkali metals or alkaline earth metals in the grooves. In the wire,
Wire knotting phenomenon is reduced, arc length fluctuations are eliminated, and spatter is reduced.
It was found that sound welding was possible.

【table】

〔Example〕

Examples of the present invention will be described below. Chemical component C: 0.03% by weight Si: 0.75% by weight Mn: 1.60% by weight Ti: 0.09% by weight A welding wire rod with a raw wire diameter of 5.5 mmφ was drawn to 2.0 mmφ using a cold wire drawing die, _N2 with dew point 10℃
After annealing with gas at 700℃ for 3 hours,
A uniform wire with little variation in crystal grain size in the wire surface layer was obtained. The average crystal grain size of this wire surface layer was 55 μm, the crystal grains were larger than those of the grain boundary oxidation layer, and the A value was 0.7. After applying copper plating to this wire, it is drawn to a diameter of 12 mm to create grooves on the surface. Skin-pass wire drawing was performed using a lubricating oil containing K ₂ CO ₃ and Cs ₂ CO ₃ , and welding tests were performed under the conditions shown in Table 1. Good results were obtained with good feedability and arc stability. showed that. [Effects of the Invention] As explained above, by appropriately selecting the heat treatment conditions for welding wire with specified C and Ti, uniform fine grooves are generated on the wire surface, and the grooves are coated with lubrication containing an arc stabilizer. By impregnating the welding wire with oil, the welding wire of the present invention generates less copper powder into the conduit tube even during long-time welding, has excellent feedability, and has less spatter. Stable weldability can be obtained from beginning to end. Therefore, the welding wire of the present invention has extremely high utility value in recent robot welding and the like.

[Brief explanation of the drawing]

Figure 1 is a graph showing the A value (ratio of average grain boundary oxidation layer to average grain size) and the amount of copper powder generated in the conduit tube, and Figure 2 is a graph showing the relationship between carbon content and average grain size. 3 is a graph showing the amount of carbon and the amount of copper powder generated. FIG. 4 is a schematic cross section in the depth direction of the wire surface layer showing the grain boundary oxidation state after intermediate annealing and at the cold drawing diameter. It is a diagram. 1...Copper plating, 2...Grain boundary oxidation part.

Claims (1)

[Claims] 1 A welding wire containing C: 0.02 to 0.06% by weight Ti: 0.03 to 0.30% by weight, in which the ratio A of the grain boundary oxidation layer of the wire surface layer to the crystal grains is 0.4≦A≦ 1.8 However, A=average grain boundary oxidation layer thickness (μm)/average grain size (μm)
m) A welding wire with excellent feedability and welding workability, which is obtained by coating the wire surface with a lubricating oil having arc stability and rust prevention properties.