JPS6216747B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a flux-cored wire for gas-shielded arc welding, which provides high welding efficiency not only in a downward direction but also in a horizontal fillet and vertical position. Various techniques have been known for wires for gas-shielded arc welding, but these can be roughly divided into those using solid wire as typified by Patent No. 236948, and those using solid wire as typified by Patent No. 299057 and Patent No.
There are some that use flux-cored wire, such as No. 288405. Among these, those that use solid wire have a relatively small diameter of 2.0 mm or less, and can be used in an extremely wide current range by combining a power source with DC constant voltage characteristics and a wire feeding device.
Furthermore, the generation of slag is minute, and highly efficient welding with a high welding rate is possible. In addition, in terms of productivity, it only requires melting and wire drawing, and it requires few man-hours and can be mass-produced with a certain quality, so it is widely used for low-cost, high-efficiency automatic and semi-automatic welding. It is becoming popular. On the other hand, since almost no slag is generated, it has poor bead surface condition and poor adhesion to the base material, which limits its application to bridges, vehicles, and other welded structures that require high fatigue strength. This is particularly problematic given the recent trend toward the use of higher strength steels. Furthermore, since the purification effect of slag is poor in the molten metal state, the incidence of macro and micro defects is high, especially in multilayer welding of thick plates. Furthermore, since the use of arc-stabilizing substances is extremely limited in this type of wire, shield welding using inexpensive carbon dioxide gas produces strong arc noise and light, creates a large amount of spatter, and requires a welder's attention. It has become clear that there are various problems, including a tendency to increase fatigue. On the other hand, the gas-shielded arc welding method using flux-cored wire, as typified by Patent No. 299057 and Patent No. 288405, does not have the disadvantages of using solid wire, such as welding workability, bead appearance, shape, and internal defects. , can be ideally solved due to the slug action effect produced. Particularly recently, these conventional techniques have been significantly improved in terms of welding workability, bead shape, and posture weldability. However, when we compare these flux-cored wires and solid wires in terms of welding efficiency, even the flux-cored wires published in Japanese Patent Publication No. 48-23776, which aimed to improve welding efficiency, are only slightly superior in welding speed and remove slag. Due to the increase in man-hours and decrease in welding rate, overall efficiency cannot be improved. Furthermore, in order to increase the melting efficiency and increase the melting speed, more than 60% of the slag agent in the flux core is melted and pulverized in advance to adjust the particle size, which increases the number of man-hours and makes the flux raw materials even more expensive. Therefore, the price of the entire wire will be higher. For this reason, there is little merit in terms of overall welding costs, and at present it has not been used in large quantities.Therefore, it is desired to provide a flux-cored wire that is inexpensive and has high welding efficiency. As mentioned above, the solid wire represented by Patent No. 236948 has problems in terms of welding workability, bead shape, and internal defects, and the conventional flux-cored wire has problems in welding efficiency and wire cost. The present invention aims to improve welding efficiency, which is unsatisfactory with conventional techniques, and to provide an inexpensive flux-cored wire for gas-shielded arc welding. It was newly constructed. That is, the gist of the present invention is to provide a flux-cored wire consisting of an outer skin made of carbon steel and a flux core enclosed in the outer skin, in which the ratio t/D of the thickness of the outer skin to the wire diameter is 0.10 to 0.23, and the ratio of the outer skin thickness to the wire diameter is 0.10 to 0.23. The eye has a structure with a protrusion of less than 1/4 of the wire diameter inward, and the flux core is made of 2 to 10% slag agent, 1.5 to 8% deoxidizing metal, and the balance iron powder based on the total weight of the wire. A flux-cored wire for gas shield welding is characterized in that 30% by weight or more of the iron powder is electrically insulated. The present invention will be explained in detail below. FIG. 1 shows a cross-sectional structure of a flux-cored wire according to the present invention. That is, the wire is composed of an outer shell H made of carbon steel and a flux core F enclosed therein, and the diameter D of the wire in this case is the arithmetic mean of D ₁ and D ₂ (D = D ₁ + D _{2 )} as shown in the figure. /2), and the thickness t of the outer skin is also the arithmetic mean of t ₁ , t ₂ , t ₃ , t ₄ (t =
t ₁ + t ₂ + t ₃ + t ₄ /4). Of course, it is desirable to measure these dimensions using a vernier caliper, micrometer, or other appropriate equipment as many times as necessary to obtain sufficient reliability. Next, in order to increase welding efficiency in automatic welding, firstly, increase the amount of wire melted per unit time, and then reduce the amount of slag, fume, and spatter generated by reactions during welding. rate needs to be increased the most. The amount of wire melting during arc welding is almost constant when the polarity is wire (+) without being affected by the components of the wire itself, but it can be changed by changing the electrical resistance of the wire. Therefore, based on the total weight of the wire, 5.2% TiO ₂ and 0.8%
_SiO2 , 1.2% _Al2O3 , _0.3 %MgO, 0.4% _ZrO2 , 0.2
%NaF and Fe―Si―Mn, Fe―
Deoxidizing metal consisting of Mn, Al-Mg is 2.1%Mn, 0.6%
By maintaining a constant ratio of %Si, 0.1%Al, and 0.2%Mg and adjusting the amount of iron powder, we created a 1.6mm diameter wire with a varying ratio of outer skin thickness to wire diameter, which is related to the electrical resistance of the wire. Produced experimentally, using carbon dioxide as a shielding gas, wire (+)
The relationship between welding efficiency and welding efficiency was investigated when welding was performed under conditions of a constant distance between base metal and chip of 25 mm, welding current of 400 A, and arc voltage of 34 V. The results are shown in FIG. In the figure, the horizontal axis shows the ratio t/D of the outer skin thickness t to the wire diameter D, and the vertical axis shows the melting rate and welding rate of the wire in grams per minute. Curve A shows the melting rate and curve B shows the welding rate when welding is performed under the above-mentioned conditions. Straight line C shows the welding speed (in the same publication, the welding speed) level in the case of 400A as shown in Figure 7 of Japanese Patent Publication No. 48-23776. C-2 is C to facilitate comparative study.
This is an estimated value of the welding rate when the value of is the same as the welding conditions of the present inventors. S is patent number
This shows the welding speed when a solid wire with a diameter of 1.6 mm, typified by No. 236948, is welded under the same conditions. As can be seen from the figure, by changing t/D, the melting rate and welding rate change as shown by curves A and B. In this case, if t/D is greater than 0.23, C
The welding speed is lower than the welding speed of flux-cored wire by the conventional method shown by the straight line 2. (The Y region indicates a zone with low welding efficiency.) Also, as t/D decreases, the melting rate and welding rate increase according to curves A and B, but as t/D becomes smaller and smaller, The rate of increase gradually decreases, and when t/D becomes smaller than 0.1, the melting rate and welding rate hardly increase. (The Z region indicates the region where welding workability deteriorates.) Therefore, as a result of various studies to further improve welding efficiency, we found that by forming an oxide film on the surface of the iron powder particles in the flux core of the prototype wire, we decided to It has been found that when the iron powder is replaced with iron powder that is insulated, the melting rate increases even when t/D is small, and the welding rate also increases. Therefore, in order to clarify the relationship between the amount of insulated iron powder in the iron powder and welding efficiency, the ratio t/D of the outer skin thickness to the wire diameter was set to 0.15, and
5.2% _TiO2 , 0.8% _SiO2 , 1.2% _{Al2O3 ,} 0.4%
Slag agent consisting of ZrO ₂ , 0.3% MgO, 0.2% NaF,
Deoxidizing metals consisting of Fe-Si-Mn, Fe-Mn, Al-Mg, 2.1%Mn, 0.6%Si, 0.1%Al, 0.2%Mg,
Using 29% iron powder, we made prototype wires with a diameter of 1.6 mm in which the iron powder was replaced with electrically insulated iron powder at various ratios, and determined the relationship with welding efficiency under the same conditions as in Figure 2. . The results are shown in FIG. In the figure, A is the melting rate and B is the welding rate. That is, it was found that when the blending ratio of the insulated iron powder exceeds 30% by weight, the welding efficiency increases. Therefore, in the present invention, it is necessary to use at least 30% by weight of iron powder that has been electrically insulated. In this case, the treatment may be the above-mentioned oxidation, coating with non-metallic powder, or any other method as long as it maintains the electrical insulation properties of the commonly used iron powder. Curves A-2 and B-2 in Figure 2 are obtained by replacing 60% of the iron powder in the flux core of the wire for which A and B were determined with iron powder that has been electrically insulated by forming an oxide film. Melting rate and welding rate by wire. As is clear from the figure, the wire of the present invention can significantly improve welding efficiency over the conventional wire. However, if t/D is less than 0.1, the arc becomes unstable and the amount of spatter increases no matter how the properties of the flux core are changed. On the other hand, if t/D exceeds 0.23, no merit will be recognized for improving welding efficiency, which is the objective of the present invention. Therefore, in the present invention, the ratio t/D of the outer skin thickness to the wire diameter is in the range of 0.10 to 0.23. On the other hand, as t/D is reduced in terms of wire manufacturing, the outer skin thickness becomes smaller, making it difficult to butt the two ends together when forming the steel strip into a tubular shape. Furthermore, even if the wires are butted, the flux tends to spill out from the seams of the outer skins, making it difficult to form and draw the wire. In the present invention, in order to make it possible to manufacture wires stably and easily even in such cases, the butt part of the outer skin is processed to protrude inward to a length of 1/4 or less of the wire diameter, as shown in Figure 1. do. If the protruding length a of the seam is made larger than 1/4 of the wire diameter, not only will it be difficult to fill with flux, but the effect of reducing the outer skin thickness will be small, and the rate of increase in welding efficiency will be reduced. . Next, in order to maximize the welding rate, we considered the amount of slag agent within a range that does not impair the bead appearance and shape, taking into account the slag composition, the type and amount of deoxidizing metal, and the amount of iron powder. However, it was found that it could be reduced by up to 2%. On the other hand, since slag agents exceeding 10% are not necessary for the purpose of improving the welding rate, they are excluded from the present invention. The slag agent in this case does not need to be melted or pulverized, and by selecting enough ordinary raw materials and combining them appropriately, the melting rate does not decrease and it is possible to make a wire with less spatter loss. The slag agents mentioned here include TiO ₂ , SiO ₂ , Al ₂ O ₃ , which melts into slag due to arc heat.
Refers to one or more of ZrO ₂ , MgO, NaF, etc. Furthermore, the present invention requires 1.5 to 8% of deoxidizing metal based on the weight of the wire. The deoxidizing metal in this case may be any metal that exhibits a deoxidizing effect during welding, and may be used in the form of a single substance, an alloy, or an iron alloy, such as Mn, Si, Al, Ti, Zr, and Mg. If the amount is less than 1.5%, a sufficient deoxidizing reaction will not take place, resulting in a decrease in the X-ray performance of the weld and failure to obtain sufficient mechanical properties. Moreover, if it exceeds 8%, the hardness of the weld metal will increase more than necessary, and the bending performance, fragility resistance, and impact toughness will decrease. As explained above, the present invention allows various factors to be organically and
By comprehensively adjusting the combination, it is possible to significantly improve welding efficiency without impairing conventional productivity and welding workability. Next, the effects of the present invention will be explained in more detail with reference to Examples. Example Table 1 shows the configuration of the prototype wire and the test results. In the same table, Nos. 1 to 11 are the wires of the present invention,
Nos. 12 to 21 are comparative examples. In addition, No. 21 is a commercially available 1.6
mm diameter solid wire. Each wire No. 1 to No. 20 was formed and drawn to a diameter of 1.6 mm by adjusting the dimensions of the outer steel band and the flux core composition according to the respective configuration. Using these wires, we made mild steel 16mm thick and 70mm wide.
mm, using a flat plate base material with a length of 380 mm, DC wire (+), welding current: 200 to 500 A, arc voltage: appropriate value for each welding current, wire protrusion length: 25 mm, welding speed: 30 cm/min, Welding efficiency was calculated by performing downward automatic welding under the conditions of shielding gas: welding carbon dioxide gas of 20 liters/min, and measuring the melted weight of the wire per unit time and the welded weight to the base metal at that time. At the same time, welding workability in the case of single-layer welding was also investigated. The welding efficiency was determined as described above with reference to the JISZ3182 method for measuring the deposition rate of coated arc welding rods, taking into consideration welding conditions, measurement accuracy, and reproducibility. Furthermore, welding workability of horizontal fillets was investigated using 20 mm thick mild steel and 50 kg high tensile strength steel with black scale still attached, while varying the welding speed and welding current. The workability of each wire in vertical position welding is as follows:
A comparison was made when the 20 mm thick steel plates were butted with a 60° V groove and moved upward at a constant welding current of 220 A. In addition, using 20mm thick mild steel, the bevel angle is 45°,
Welding a groove with a backing metal with a root gap of 12 mm using a welding current
400A, arc voltage 34V, welding heat input 25JK/cm, wire protrusion length 25mm, shielding gas carbon dioxide 20l/
Multi-layer welding is carried out at min.
Tensile properties and impact toughness were investigated using JISZ3111 No. A1 and JISZ3112 No. 4 test pieces. The above test results for each wire are summarized in Table 1. From the same table, it can be seen that wires Nos. 1 to 11 of the present invention are all comprehensively excellent in terms of welding efficiency, workability, mechanical properties, and soundness of the welded part.

【table】

[Table] On the other hand, No. 12 wire with t/D and protrusion length a exceeding the range specified in the present invention is generally good in terms of workability and mechanical properties, but welding Efficiency is low. No. 13 wire has a too small t/D, so the arc during welding is unstable, a large amount of spatter is generated, workability is poor, and slag is likely to be caught. No. 14 wire has good welding efficiency like No. 13 wire, but because the protruding length a of the outer skin seam is long, the filling flux does not enter stably, pits occur, and welding workability is extremely unstable. It was hot. No. where the amount of iron powder for insulation treatment does not reach the lower limit of the present invention.
Wires 15 and 16 exhibit almost the same performance as the wire of the present invention in terms of welding workability and mechanical properties, but they have lower welding efficiency and tend to have a slightly higher incidence of pitting in horizontal fillets than other wires. No. 17 wire had no slag agent added at all, but the arc was rough and unstable, and workability in horizontal fillet and vertical welding was extremely poor. On the other hand, in No. 18, which had an extremely large amount of slag, the slag was significantly advanced, the arc was unstable, and internal defects such as poor penetration and slag entrainment were observed in the weld. Wire No. 19 had insufficient deoxidation, and wire No. 20 had too many pits due to excessive deoxidation, making welding virtually impossible. The No. 21 solid wire had better impact toughness than the No. 1 to 11 wires, but the welding efficiency and
It was found that the workability was poor. Furthermore, in order to clarify the difference in welding efficiency, Fig. 4 shows the relationship between welding current and welding efficiency for the wire of the present invention.
A comparison is shown between No. 8 and wires No. 15 and No. 21, which are outside the scope of the present invention. In the same figure, A shows the melting speed of No. 8 wire, B shows the welding speed of the same wire, C shows the welding speed of No. 15 wire, and D shows the welding speed of No. 15 wire.
21 shows the welding speed of wire. Both wire diameter:
1.6mm, distance between base metal chips: 25mm. As is clear from the figure, the welding efficiency of the wire of the present invention is significantly improved over the conventional wire across all currents. As detailed above, the wire of the present invention does not deteriorate the welding workability, bead shape, appearance, and mechanical properties of the flux-cored wire of the prior art, and is made from molten and pulverized raw materials that increase man-hours and become expensive as a slag agent. without the need for
This can greatly improve welding efficiency. This is expected to improve welding efficiency and yield, increase the added value of flux-cored wire for automatic and semi-automatic welding, and greatly increase the industrial value in this field.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the cross-sectional structure of the flux-cored wire of the present invention, Fig. 2 is a diagram showing the relationship between the ratio t/D of the outer skin thickness to the wire diameter and welding efficiency, and Fig. 3 is a diagram showing the insulation treatment in the metal iron. FIG. 4 is a diagram showing the relationship between the amount of iron powder and welding efficiency, and is a diagram comparing the welding efficiency of the wire of the present invention and the conventional wire at each welding current.

Claims (1)

[Claims] 1. In a flux-cored wire consisting of a carbon steel outer shell and a flux core enclosed in the outer shell, the ratio t/D of the outer shell thickness to the wire diameter is
0.10 to 0.23, the seam of the outer skin has a structure in which a protrusion of 1/4 or less of the wire diameter is inward, and the flux core is made of a slag agent of 2 to 10% and 1.5 to 8% of the total weight of the wire. A flux-cored wire for gas-shielded arc welding, characterized in that the iron powder is electrically insulated by at least 30% by weight, and the remainder is iron powder.