JPS60130475A - Mig welding method - Google Patents

Abstract

PURPOSE:To prevent low-temp. cracking owing to hydrogen in a weld zone by separating and removing the vapor of the adsorbed moisture and evaporating hydrogen molecules resulting from external heating or self-resistance heating of a fed wire by the gas flowing along the wire thereby preventing the inflow thereof to the welding arc part. CONSTITUTION:A welding wire 1 is heated by a heat source 9 and receives electricity from an electrode chip 12, by which air shielded arc welding is accomplished in a gaseous argon 8 atmosphere. The vapor of the moisture adsorbed on the wire 1 and the evaporating hydrogen molecules generated as a result of heating by the heat source 9 are delivered to an outside part 8 by the gaseous argon 11 admitted into the introducing part of the chip 12, by which the intrusion thereof into the arc weld zone is prevented. The generation of low temp. brittle cracking owing to the hydrogen in the weld zone is prevented.

Description

[Detailed description of the invention] The present invention relates to improvements in the M-G welding method.

A conceptual diagram of conventional M-G welding is shown in Fig. 1.

The welding wire 1 wound into a coil is automatically fed to the welding torch 3 by a feeding roller 7, and is energized by a DC welding power source 4 to create an arc between the base metal 5 and the welding wire 1. The base material 5 and the welding wire 1 themselves are melted and joined. At this time, a shielding gas 8 such as Ar is flowed from the nozzle 7 in order to shield the molten metal 6 from the atmosphere. However, in the conventional M/G welding method, when welding high-strength steel, cold cracking occurs due to atmospheric moisture adhering to the welding wire and hydrogen absorbed during wire manufacturing. To prevent this, it is necessary to perform intermediate annealing or sufficient immediate heating of the welded part to diffuse and release the diffusible hydrogen in the weld metal into the base metal and the atmosphere, and prevent it from accumulating in the weld metal. be. However, such dehydrogenation heat treatment poses major problems in terms of construction period and cost.

In recent years, as structures have become larger, high-strength steel has been increasingly used to reduce their weight.

However, cold cracking caused by hydrogen is a problem in welded joints made of thick high-strength steel. Therefore, the present invention efficiently (prevents) cold cracking caused by hydrogen.

The present invention heats the welding wire in the wire feeding section of the M/G welding machine by an external heat source or by the resistance heat generation of the welding wire itself, and evaporates and removes moisture and hydrogen molecules adsorbed on the surface of the welding wire. , relates to an M-G welding method characterized in that the amount of hydrogen entering the weld metal is reduced by removing removed moisture and hydrogen molecules to the outside by a carrier gas flowing along a welding wire.

According to the method of the present invention, it is possible not only to reduce the amount of hydrogen entering the weld metal, but also to improve the welding speed due to the preheating effect. 5. The present invention is applicable to all high-strength, thick-plate welded structures such as chemical machines, prime movers, and offshore structures.

FIG. 2 and FIG. 3 show conceptual diagrams of the M/G welding machine used in the present invention.

First, 8 in FIG. 2 is different from the conventional one shown in FIG. and a nozzle 10 for flowing a carrier gas 11 such as Ar along the two welding wires. Note that 12 indicates an electrode tip.

3, which is different from the conventional one shown in FIG. 1, is that a ceramic tip 13 is attached to the tip of the electrode tip 12, and a carrier gas (
(Ar, etc.) 11.

In the case of Figure 2, the welding wire is heated by a heat source such as a high frequency coil or nichrome wire, and in the case of Figure 3, the welding wire is heated by the resistance heat generation of the welding wire itself, and the water and hydrogen molecules adsorbed on the surface of the welding wire are heated. evaporates and removes. The moisture and hydrogen molecules thus removed are removed to the outside by the carrier gas 11. In addition, the wire preheating effect increases welding speed and improves welding efficiency.

Thus, according to the method of the present invention, the amount of hydrogen that enters the weld metal can be reduced, making it possible to shorten or omit intermediate annealing and immediate heating time, and thus shorten the construction period and reduce costs.

Examples of the present invention are shown below.

Example A plate with a thickness of 200 mm and a cross-sectional shape shown in Figure 4.

HT100 steel plates having a length of 400 m were welded using a narrow gap MI+l) welding machine under the conditions shown in Table 1.

After 48 hours, a cross-sectional macroscopic investigation was conducted, and it was found that many low-temperature cracks occurred in the conventional method, but no cracks occurred in the welding wire heated according to the method shown in FIG. 2 of the present invention.

Further, a bead-on plate was prepared under the conditions shown in Table 1 according to J Engineering 8Z 3113 K, and the amount of diffusible hydrogen in the weld metal was measured. The results are shown in Table 1.

Table 1 shows that the amount of hydrogen in the weld metal can be reduced to about A by using the method according to the invention.

Table 1: Diffusible hydrogen amount measurement results and presence or absence of cracks

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of conventional M-work G welding, and FIGS. 2 and 3 are conceptual diagrams of a M-work G welding machine used in the present invention. FIG. 4 shows the cross-sectional shape of the HT10G steel plate welded in the example. Sub-agents 1) Meifuku agent Ryo Hagiwara - Tokukai Sho GO-130475 (3)

Claims (1)

[Claims] In the wire feed section of the MIG welding machine, the welding wire is heated by an external heat source or the welding wire's own resistance heat generation, and the moisture and hydrogen molecules adsorbed on the surface of the welding wire are evaporated and removed, and the removed moisture difference is A MIG welding method characterized in that the amount of hydrogen entering the weld metal is reduced by removing hydrogen molecules to the outside by a carrier gas flowing along the welding wire.