JPS5823837B2 - Flux for arc welding rods - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flux for arc welding rods used as a coating agent for surface hardening coated arc welding rods, particularly for use in surface hardening coated arc welding rods suitable for wear-resistant weld overlay of mild steel. Regarding flux.

As a countermeasure, the screw blades of the screw conveyor, the impeller of the impeller breaker, the blades of the induction fan, etc., which are subject to severe wear due to contact with the treated materials such as cement clinker 1 slag, earth and sand, and their dust, etc. Wear-resistant overlay welding has been applied to the surface.

This involves overlay welding onto the base metal using a welding rod that produces a weld metal with high hardness.

Conventionally, as welding rods for hardfacing to prevent earth and sand abrasion, W-based welding rods in which the weight ratio of W as an alloy component in flux is about 70 to 80% have often been used.

However, although the above-mentioned conventional product has good wear resistance, it has a drawback that cracks are likely to form between the mild steel base material and the built-up part because of the large amount of W.

Furthermore, since the content of W is large, it is very expensive.

The present invention improves these drawbacks of conventional products and provides an inexpensive flux for arc welding rods that has high wear resistance, is less prone to cracking at the boundary between the base material and the built-up part, and is less likely to cause cracks.

As a result of research into various alloy component combinations, the present inventors found that
Compared to the above-mentioned conventional W-based welding rod, the amount of W is greatly reduced and welding rods are made of Mo, Cr, and Mn.

By using a small amount of B in combination, it was possible to obtain a flux for arc welding rods that has high wear resistance against cement clinker-1 slag, sand, etc., and is less likely to cause cracks at the boundary between the base material and the built-up part.

That is, according to the present invention, the alloying element components in the flux are 0.3 to 5% (as graphite), W 2 to 8% (as WC and W2C), Mo 6 to 1% by weight.
0% (as Fe-Mo) Cr 6-12% (as Fe-Cr) Mn 2-4% (as Fe-Mn) B 1.
The alloy components are blended so that Fe is 15.3 to 23% (as Fe-B) (total content in the ferroalloy), and the remainder consists of a slag agent, and the high hardness weld metal is A flux for an arc welding rod is provided.

The target chemical components in the weld metal obtained by the above combination of flux and core wire are as follows.

CO96-1.2 ratio W 0.7-2.8 ratio Mo 2.5-3.8% Cr 2.5-5.0% Mn 0.7-2.0% BO, 1-0.35 % Fe 81.4-92.0% However, among the alloy components in the flux to obtain the chemical composition of the weld metal, the most important element for increasing hardness is W, which is extremely Since they are expensive, Mo, Cr, and B were used in combination as metal elements to replace them.

If the amount of W is less than 2%, sufficient hardness cannot be obtained;
Even if it is more than that, there is little increase in hardness.

Mo is preferably in the range of 6 to 10%, and when W is large, it is desirable to use a small amount of Mo, and when W is small, it is desirable to use a large amount of Mo.

B exhibits hardness in the range of 1.8 to 3, and in this range there is little risk of cracking at the interface between the base material and the built-up portion.

Furthermore, if the Cr content is less than 6, there will be insufficient CrC in the weld metal and the hardness will not increase, and if it is more than 12, hair cracks may occur in the weld metal.

Also, if Mn is less than 2, the weld metal will be insufficiently deoxidized, and 40
If the temperature exceeds I), decarburization of the weld metal is promoted, resulting in a decrease in the hardness of the weld metal.

When using the flux for arc welding rods of the present invention configured as described above, although the W content is lower than that of conventional products, hard alloys are scattered in the weld metal. Therefore, the wear resistance is excellent, and the low W content makes it difficult for cracks to form at the boundary between the base material and the weld metal.
Furthermore, it has a low melting point and is easy to weld.

W as a wear-resistant measure for the main plate and side plate of the blade wheel of conventional fans.
It has been difficult to form a bead on the welding rod of the present invention because cracks occur at the boundary between the main plate and side plates and the bead area, which seriously affects the strength of the main plate and side plates.However, with the welding rod of the present invention, No cracks were observed even after applying the bead, and there were no problems with strength, so it became possible to add wear-resistant beads to the main and side plates of the fan wheel.

The present invention will be explained in more detail below with reference to Examples.

Example 1 The first
Chemistry of weld metal when bead welding is carried out at ℃ on a welding rod fixed to the flux with the mixing ratio shown in the table so that the outer diameter is 8.5 mm (55% core wire, weight ratio of 45% flux) The components and Shore hardness are shown in Table 2.

As mentioned above, the flux for arc welding rods of the present invention has a small amount of W, and the average Shore hardness of the weld metal is about 80 to 84, but it has hardened parts with a maximum Shore hardness of 92 to 94, so it has poor wear resistance. is noticeably dog-like.

Example 2 Using the welding rod of Example 1, welded a 5S41 steel plate 3 with a thickness of 9 mm as shown in Fig. 1, and then bent it at right angles. No cracks were generated between the steel plate 3 and the built-up portion 4.

Comparative Example A commercially available W-based wear-resistant overlay welding rod containing 7 to 80% WCC powder in flux (the chemical composition of the weld metal shown in Table 3 below).

) was used to perform bead welding in the same manner as in Example 2. As shown in Figure 2, cracks 1 were generated at the boundaries between the base metal steel plate 3 and the overlay 4, and the welds became more perpendicular. When bending was performed in the same manner, crack 2 expanded due to the bending effect.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing a welding location when welding using the flux for arc welding rods of the present invention, and FIG. 2 is a schematic cross-sectional view showing a welding location when welding using a known welding rod. In the figure, 1 represents a crack, 2 represents an enlarged crack, 3 represents a steel plate, and 4 represents an internal filling part.

Claims (1)

[Scope of Claims] 1. A flux for a coated arc welding rod used for overlay welding by arc welding using mild steel as the welding rod core wire, wherein the alloying element composition in the flux is C3 to C3 by weight. Section 5 (as graphite) W Section 2-8 (as WC and W2C) Mo 6-
10% (as Fe-Mo) Cr 6-12% (Fe-
(as Cr) Mn 2-4% (as Fe-Mn) B 1
．． 8~3% (as Fe-B) Fe 15.3~
23 (total content in the ferroalloy) A flux for arc welding rods, characterized in that alloy components are blended so that the remaining content is a slag agent.