JPS6142499A - Flux cored wire for welding - Google Patents

Abstract

PURPOSE:To improve an impact toughness of an weld metal obtd. by using a steel sheath contg. a prescribed ratio each of B and C and incorporating the B source which is heretofore added into the flux to be packed into the sheath of a wire into the steel sheath as well. CONSTITUTION:This flux cored wire for welding is formed by packing the flux around the steel sheath of the wire contg. 0.001-0.01wt% B and <=0.04wt% C. A suitable amt. of B is incorporated into the weld metal by such wire, by which the common use effect of Ti-B is provided and the weld metal having the excellent impact toughness is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a flux-cored wire for welding, and more particularly to a slack-cored wire for welding (hereinafter referred to as wire) from which weld metal with excellent impact toughness can be obtained.

(Prior art) A wide variety of wires are currently manufactured, but wires with rutile as the main component of the flux have an extremely stable arc even in a CO2 atmosphere, so they generate less spatter and can produce excellent bead shapes. It has many advantages such as giving. Therefore, the development of a wire that takes advantage of such good welding workability and welding efficiency and also has the low-temperature toughness of weld metal has been strongly desired in recent years as energy resources are being developed in colder regions and offshore. However, wires in which rutile is the main component of the flux generally have the disadvantage that the impact toughness of the weld metal is low. As a countermeasure to this problem, as seen in Japanese Patent Application Laid-Open No. 116351/1983, TI,
A method has been proposed to refine the structure by retaining an appropriate amount of B in the weld metal.

The mechanism of microstructural refinement by TI and B is thought to be as follows. That is, T10 forms a yield in the weld metal, becomes a nucleus for the production of acicular ferrite, and refines the structure. In addition, KB segregates at austenite grain boundaries and the free energy of the grain boundaries decreases, which suppresses the formation of pro-eutectoid ferrite and refines the structure.

TIO and B, which bring about the refinement mechanism of the weld metal structure in this way, are produced by the following method. To generate TIO, rutile (TiO2), which is the main component of the wire, must be replaced with At, 'M, which has a lower energy for oxide formation than TI.
Either partially reduce it with a deoxidizing agent such as G to generate TlO, or directly add it to the flux as a metal TI.
There is a method to generate O.

It is considered that TiO can be easily generated in a rutile-based wire in this manner. On the other hand, in order to maintain a suitable amount of B in the weld metal, a small amount of B is added to the flux in the form of a B alloy like Fe-H or in the form of an oxide like B2O3. However, since the proportion of B in the flux is very small, B segregates in the flux, and in some cases, the filling rate of the flux fluctuates, which tends to make the yield of OB in the weld metal unstable.

Also, one type of wire is used for downward, vertical, horizontal, and upward welding, but since the current used differs in each position, the yield of B becomes unstable. In this way, adding a B source to the flux in the form of powder or granules makes the yield of OB in the weld metal unstable, and the joint effect of p, TI, and B is not fully exerted, and the impact toughness at low temperatures is improved. cannot be secured.

(Problems to be Solved by the Invention) In view of the above-mentioned problems, the present invention provides an appropriate amount of B in the weld metal.
TI by achieving stable yield.

The purpose of the present invention is to provide a wire that fully exhibits the combined effects of B and provides good impact toughness.

(Means for Solving the Problems) The present invention solves all of the above problems by incorporating a B source, which was conventionally added to flux, into the steel sheath.The gist of the present invention is to add flux to the wire sheath. In the flux-cored wire formed by filling, the amount of B is 0.
The flux-cored wire for welding is characterized by using a steel outer skin having a content of 0.001% to 0.01%.

(Action of invention) The operation of the present invention will be explained below.

Wire (,) with B2O5 added to the 016 flux as a B source and 0.007% B in the steel sheath.

A prototype wire (b) containing 0.03 g of C was produced, and welding was carried out semi-automatically in each position to investigate the impact toughness of the weld metal. Table 1 shows the prototype wires (a) l (b), Table 2 shows the welding conditions in each welding position, and Table 3 shows the impact value of the weld metal in each welding position.

The test steel plates were 5M-50B (45° V groove, 12 root gaps) with a thickness of 16 mm and were laminated in multiple layers with the same number of layers in each orientation.

Table 3 As shown in Table 3, the shear wire (b) has higher impact values in each posture than the wire (,). This confirms that by incorporating B into the steel sheath, an appropriate amount of B can be incorporated into the weld metal to further enhance the joint effect of yield TI. Further, the impact value of the wire (,) in the upward position is lower than in other positions. B
This is thought to be because the yield was unstable. According to the research conducted by the present inventors, when the amount of B in the steel outer skin exceeds 0.010%, a large amount of solid solution B remains in the weld metal, resulting in hardening and a decrease in impact toughness. It was found that when the ratio is less than 0,0014, no effect of refining the structure of the weld metal due to solid solution BIC can be expected.

In addition, when B is included in the steel sheath, the steel sheath hardens, making it difficult to draw the wire to a diameter as small as 1 or 2φ, which is generally used as a wire.However, in the present invention, the amount of C is reduced. The above problem was solved by making it 0.04 inch or less. Special KO, below 03%, there was almost no disconnection.

(Example) Next, the effects of the present invention will be explained in more detail with reference to Examples.

Example 1 Table 4 shows a wire (c) in which 2.0 g of Fe-B (2% B) was added to the flux as a B source and a wire (c) in which 2.0 g of Fe-B (2% B) was added to the steel jacket.
．． Wires (d), (e), and (f) containing 0.002, 0.006, and 0.011 are shown. Further, the C content of the steel outer skin of wires (d), (6), and (f) was 0.03%.

Wires (e), (d), (a) shown in Table 4
, (f) was semi-automatically downward welded by changing the welding current, and the yield p ratio and impact toughness of OB in the weld metal were investigated. Table 5 shows the welding conditions, Table 6 shows the yield rate of B, and Figure 1 shows the impact value. The sample steel plate is 5M-5 with a plate thickness of 201H.
0B material (45° V groove, root gap 12 sm) was stacked in multiple layers with the same number of layers under each welding condition.

Table 6 As shown in Table 6, wire (c) has a low yield shear rate of B at each welding current and a large variation, whereas wires (d), (e), and (f) have a low yield shear rate of B. The retention rate is high and the variation is small. Also, from Figure 1, the wire ((1)
, (f) have low impact values at each welding current, whereas wires (d) and (@) have high impact values and are stable at each welding current.

In wire (e), B is added to the 7 lacs, so B cannot be stably yielded in the weld metal due to segregation of B in the blacks or fluctuations in the filling rate. , the variation in yield rate was large and the impact value was low. Since the wires (d) and (e) contained B in the steel outer shell, the yield of B was stable in the weld metal and the impact value was high.

However, since wire (f) has a high OB content in the steel jacket,
A large amount of B remained in the weld metal and hardened, resulting in a low impact value.

Table 7 shows wire (g) containing B and C in the steel sheath.
, (h) and (i) are shown.

In order to investigate the wire drawability of wires (g), (h), and (i) shown in Table 7, wire diameters of 4.2 mφ and 1.
The number of wire breakages was investigated when a prototype wire of 1.2 ton in diameter was produced at a wire drawing speed of 500 m/min with a die area reduction rate of approximately 25%. The results are shown in Table 8.

Table 8 shows that when B is contained in the shear steel sheath, when the amount of C in the wire steel sheath is 0.05%, the diameter is 1.2111 mφ.
It is recognized that it is impossible to draw wire up to this point. Therefore, when B is contained in the wire steel sheath, the amount of C in the steel sheath must be 0.04 or less.

Basically, all of the B added to the wire of the present invention is added from the steel outer shell, but it is also economically possible to add a small amount of B (up to 7 lux) to appropriately control the total B amount. Naturally, it falls within the scope of the present invention in view of the purpose of supplying wire for this purpose. It goes without saying that the wire of the present invention can be applied not only to rutile-based CO2 wires but also to Ar-co2 welding wires, electrogas welding wires, submerged arc welding wires, no-gas wires, etc.

(Effects of the Invention) As described above, according to the present invention, it is possible to stably retain an appropriate amount of B in the weld metal, so that the joint effect of Tl-H is further exhibited, resulting in excellent impact toughness. Weld metal is obtained.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between welding current and impact value in a prototype wire. (]8)

Claims (1)

[Claims] In a flux-cored wire formed by filling the wire sheath with flux, the amount of B is 0.001 to 0.01 in terms of weight ratio.
%, and a flux-cored wire for welding, characterized in that it uses a steel outer skin having a C content of 0.04% or less.