JPH06285641A - Arc welding method for galvanized steel sheet and blow hole prevention agent for welding - Google Patents

Abstract

PURPOSE:To provide a arc welding method of galvanized steel sheet and a blow hole prevention agent for welding capable of greatly improving the blow hole generated in bead at arc welding. CONSTITUTION:The metal powder consisting of either or both of Cr, V is supplied at a rate of 0.1-50g per 1m along the weld line before welding and the metal powder consisting of either or both of Cr, V, which is kneaded to a uniform suspended solid with a binder and inorganic solvent, is coated and dried.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc welding method for galvanized steel sheets and a blowhole inhibitor for welding.

[0002]

2. Description of the Related Art The joining strength of a bead portion formed by arc welding is greatly reduced by a blowhole formed in the bead. This kind of blowhole is rarely formed when welding non-plated materials such as cold rolled steel sheets and hot rolled steel sheets, but when welding galvanized steel sheets, it is difficult to suppress the occurrence of these blowholes. There is a situation. The cause of the occurrence of bloholes in the joining of galvanized steel sheets is that the zinc component in the plating layer existing near the joining interface is gasified and blown into the molten steel composed of the steel plate and the wire component forming the beads. As a method to solve this problem, a special paint is applied on the welding line that becomes the joining interface,
Fe-P having a high melting point due to the P component contained in the paint
A method of forming a Zn alloy to render zinc harmless is disclosed in Japanese Patent Laid-Open No.
3-108995, and Te, S
JP-A-63-56 discloses a method in which the viscosity of molten steel is reduced by applying e, REM, or Sb alone or an oxide on the welding line before welding, and the zinc gas vaporized in the molten steel is discharged.
Although it is disclosed in Japanese Patent No. 395, it is difficult to completely avoid the brohole in the actual arc welding even by such a method, and there are great expectations for the development of industrially more effective means. Also, JP-A-64-31596
The publication discloses that the activation of molten steel and the decrease in viscosity of the molten steel occur due to the regulation of the carbon content and the oxygen content in the welding wire, which suppresses the generation of brohol. The blowholes have not been solved by the actual arc welding, and there is a demand for an industrial technology that can reliably suppress the occurrence of blowholes.

[0003]

DISCLOSURE OF THE INVENTION The present invention advantageously solves such a requirement, and can greatly improve the blowholes generated in the bead during arc welding. There is an attempt to provide a blowhole inhibitor.

[0004]

According to the present invention, which has solved the above-mentioned problems, a metal powder containing one or both of Cr and V is added in an amount of 0.1 to 50 per 1 m before welding.
A first invention is an arc welding method for galvanized steel sheet, which is characterized in that it is supplied along the welding line at a rate of g.
A second invention is a blowhole-preventing agent for welding, which is obtained by applying and drying a uniform suspension prepared by kneading a metal powder of either r or V together with a binder and an organic solvent.

In the present invention, in order to make the zinc gas blown into the molten steel harmless, it is necessary to prevent the invasion of the zinc gas which penetrates into the molten steel. It has been found that it is effective to make a metal composed of one or both of Cr and V to be enhanced exist. Then, in order to suppress the generation of blowholes, it is concluded that a certain amount of metal powder consisting of one or both of Cr and V should be supplied along the welding line before welding, and the present invention is achieved. It has been completed.

The characteristic of galvanized steel plate joining by arc welding is that the low melting point and low boiling point zinc present at the joining interface is gasified and taken into the molten pool, and remains as bubbles even after the outer wall of the molten pool solidifies, To form innumerable broholes in the bead. Therefore, in a non-plated steel sheet that does not contain a low boiling point component in the joint, it is impossible to reliably suppress the generation of this type of blowhole. From this point of view, considering the measures against blowholes during arc welding of galvanized steel, either prevent the penetration of zinc gas into the molten pool or replace the penetrated zinc gas with a reaction product with a high boiling point. As far as possible, it can be said that it is difficult to reliably suppress the generation of brohol.

Therefore, detailed analysis was conducted on the existence state of the zinc gas that penetrated into the molten steel, and it was found that the amount of the zinc gas that penetrated into the bead was related to the viscosity of the molten steel. That is, AL and S, which are components that greatly reduce the viscosity of molten steel, have many pits and promote the floatation of zinc gas, but the zinc content in the bead is large and the number of blowholes does not decrease. On the other hand, Cr and V that increase the viscosity of molten steel
In the case of, the characteristic that the zinc content in the bead was remarkably reduced was observed. Then, when the Cr content in the molten steel or the content ratio is above a certain level, the zinc content in the bead as well as the pit decreases,
I found the fact that Brohol decreased.

As a means for introducing Cr or V into the molten steel, for example, a method of incorporating it into a steel plate, a plating layer or a wire can be considered. However, since it is difficult to satisfy the mechanical properties of these means in any case, the method of supplying metal particles onto the welding line and incorporating them into the molten steel by utilizing welding heat is technically and economically. It was found to be the most effective means. In addition, the condition as metal particles to be supplied in order to suppress the blowholes by such a method requires that the coating amount be 0.1 g or more per 1 m of welding line. If this condition is satisfied, brohol hardly occurs. In addition, even if the coating amount is higher than this, the blohole does not recur, but excessive addition in the bead causes a decrease in the bonding strength and toughness of the bead part, and the bonding strength and toughness of the bead part are practically used. As a condition for achieving a quality level having no problem, it is necessary to supply 50 g or less per 1 m of welding line.

The anti-brohol agent as described above is composed of metal particles of either or both of Cr and V. These metal particles may be directly supplied onto the welding line, or appropriate additives such as water, solvent, adhesive and dispersant may be added to the metal particles and kneaded to form a uniform suspension, which is then applied onto the welding line. Alternatively, it may be supplied by a method of drying. As these metal particles, not only Cr and V metal simple substances but also alloys with various metals such as Fe—Cr and Fe—V may be used, and the method for producing metal particles is not particularly limited.

The welding method to which the present invention is applied is not particularly limited as long as it is arc welding. For example, it can be applied to carbon dioxide gas arc welding, MAG arc welding method and submerged arc welding. is there. Of course,
This effect is not limited to only a particular galvanized steel sheet, electrogalvanized steel sheet, hot dip galvanized steel sheet,
It becomes an effective technical means for various galvanized steel sheets containing zinc such as galvannealed steel sheets and various galvanized steel sheets.

[0011]

EXAMPLES Examples of the present invention are shown in Table 1 and comparative examples are shown in Table 2.

[Table 1]

[0012]

[Table 2] Note 1) Preparation of metal particles: A predetermined metal piece was crushed with a ball mill and used. The size of the particles is about 500 ~
It is distributed in 20 μm. Note 2) Method of supplying metal particles Spraying method: A predetermined amount was sprayed on the welding line before welding. Coating method: Ethyl silicate binder and isopropyl alcohol were added to the metal particles to form a uniform suspension, which was coated and dried on the welding line before welding.

The details of the materials to be welded in the above [Table 1] and [Table 2] are as shown in [Table 3].

[Table 3] However, E plating: iron 85%, residual zinc (plating adhesion amount 3 g /
m ² ) electroplating

The method for evaluating the generation of brohol is as follows. Main arc welding conditions Two layers of fillet welding are used, and a welding current is used so that the penetration on the lower plate side of the stack is 35% of the plate thickness. The welding speed is 1000 mm / min, the wire is 1.2 mm in diameter, and Nittetsu Welding Industry YM24S is used. Shield gas is Ar 80% e + CO ₂ 20
% And CO ₂ , and the flow rate was 25 l / min for both. As shown in FIG. 1, the welding position was horizontal, the torch (3) angle (θ) was 60 ° from horizontal, and the torch (3) advance angle (β) was 0 °. Evaluation of the Number of Defects All the weld beads were subjected to an X-ray transmission test to detect all the blowholes and evaluated by the number of blowholes per 100 mm length. Next, the bead joining strength is evaluated by cutting out the test piece so that the joining portion is at right angles to the pulling direction, obtaining the pulling strength, and the ratio with the pulling strength in the absence of metal particles under the same conditions. It was evaluated by. A bead bond strength of 100% means base material fracture and 100% or less means bead fracture.

[0015]

As is apparent from the above description, the present invention can significantly reduce the generation of blowholes during arc welding of galvanized steel sheet and can greatly improve the reliability of the joint. Moreover, since it is not necessary to satisfy the mechanical characteristics as in the case where Cr or V is contained in the steel plate, the plating layer or the wire, the cost and the use are far superior. Therefore, the present invention greatly contributes to the industrial development as an arc welding method for galvanized steel sheet and a blowhole inhibitor for welding, which eliminates the conventional problems.

[Brief description of drawings]

FIG. 1 is an explanatory view of a state where a galvanized steel sheet is welded using the present invention, where A is a front view and B is a side view.

Claims (2)

[Claims] 1. Metal powder consisting of either or both of Cr and V is 0.1 to 50 per 1 m before welding.
An arc welding method for a galvanized steel sheet, characterized in that it is supplied along the welding line at a rate of g. 2. A blowhole-preventing agent for welding, which is obtained by applying and drying a uniform suspension obtained by kneading a metal powder of either or both of Cr and V together with a binder and an organic solvent.