JPH0832371B2 - Flux-cored wire for gas shield arc welding - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flux-cored wire for gas shielded arc welding, which has excellent low-temperature toughness performance, improved productivity, and stabilized quality performance. is there.

[Conventional technology]

Conventionally used flux-cored wire for gas shielded arc welding (hereinafter referred to as wire) is mainly made of titania, which has excellent arc stability, less spatter, better welding workability and bead appearance than solid wire. Is used for.

In recent years, along with the polarization of energy resources, steel materials are required to have higher quality and higher toughness. However, as a means for improving the toughness of a conventional titania-based wire, for example, Japanese Patent Laid-Open No.
In JP-A 58-119490, low temperature toughness is improved by controlling the nitrogen content of the steel shell and iron powder, but the biggest drawback of titania is that even if a large amount of deoxidizing element is added, Since the amount of oxygen is as high as 500 ppm or more, the performance of the weld metal may be poor.

Further, there is a wire with improved low temperature toughness as shown in Japanese Patent Publication No. 46-24124 and Japanese Unexamined Patent Publication No. 52-125437.
The wire shown there has been improved in low temperature toughness by adjusting the metal carbonate, the slag forming agent and the strong deoxidizer mainly containing metal fluoride, but the metal fluoride shown here is
Almost all of them except CaF ₂ are chemically synthesized.Since the grain size is fine and the apparent density is small, there is a large variation in the target flux filling rate, which is a problem in wire production such as wire breakage during wire drawing. However, it is not always satisfactory in terms of impact value stability and quality performance.

[Problems to be Solved by the Invention]

The present invention is intended to eliminate the above-mentioned drawbacks of conventional wires and expand the field of application, and it is an object of the present invention to provide a wire that stabilizes low temperature toughness, improves wire productivity, and obtains stable quality performance. To do.

[Means for solving the problem]

The characteristic of the wire according to the present invention is that the composition of the steel outer shell is C: 0.06% or less, P: 0.009% or less, Mn: 0.2 to 1.2%, N:
Metal fluoride with an apparent density of 1.3 g / cm ³ or more based on the total weight of the wire in the cavity surrounded by the skin that is 0.0040% or less: 1
~ 10%, acidic oxide: 0.1 ~ 1%, arc stabilizer: 0.05 ~
Low temperature toughness due to 10 to 30% of the total weight of the wire filled with flux containing 0.3%, deoxidizer: 1 to 5%, iron powder and one or more kinds of alloying agents: 0.5 to 10% In addition, it is possible to improve the wire productivity and to stably obtain quality performance.

The reason why the wire according to the present invention has the above structure will be described in detail below.

[Action]

First, in the present invention, the components of the steel shell are C: 0.06% or less, P:
It is necessary to use a steel material containing 0.009% or less, N: 0.0040% or less and 0.20 to 1.2% Mn.

That is, in order to obtain a weld metal with high toughness, the C in the weld metal must be 0.07% or less, but considering the flux and the lubricant on the wire surface, the C of the rigid outer skin should be 0.06% or less. Should be. Although P and N are unavoidable impurities, P hinders the high temperature crack resistance of the weld metal and N significantly deteriorates the toughness, so P is 0.009% or less and N is 0.0040%.
Do the following. Further, Mn must be added in an amount of at least 0.20% or more in order to obtain a weld metal suitable for the required strength, but if it exceeds 1.2%, the workability at the time of wire production deteriorates and productivity deteriorates.

 Next, the composition of the flux component will be described.

The metal fluoride encapsulates the weld metal as a slag agent to improve the bead shape and raises impurities in the weld metal to clean the weld metal. This improves toughness. The metal fluorides were almost chemically synthesized except for CaF ₂ , and their grain size was small, which was a factor of decreasing the production yield and varying the flux filling rate in the wire production.

As a result of various studies to solve these problems, the present inventors have found that the apparent density of metal fluoride is 1.
It has been found that the wire productivity can be significantly improved and the quality can be stabilized by making it ³ g / cm ³ or more. As a result, it is necessary to control the apparent density of the metal fluoride to 1.3 g / cm ³ or more. As the metal fluoride, CaF ₂ , Mg
F ₂ , BaF ₂ , MnF _{2 and the} like are effective, but when an alkali metal fluoride is used, the stability of the arc is improved. If it is less than 1%, these characteristics are not sufficiently exhibited, while if it exceeds 10%, the arc becomes unstable and the amount of slag produced becomes excessive, deteriorating the welding workability. Therefore, the apparent density is 1.3g / c
The content of metal fluoride having m ³ or more is in the range of 1 to 10%. As the alkali metal fluoride, K ₂ SiF ₆ , NaF, Na ₂ SiF _{6 and the} like are effective. On the other hand, inexpensive CaF ₂ is Ar as a shielding gas.
When mixed with each other, CaF ₂ alone can reduce the generation of spatter, so that only CaF ₂ can be used as the metal fluoride. However, when CO ₂ gas is used as the shield gas, spattering is more likely to occur with CaF ₂ alone, so it is preferable to use it in combination with an alkali metal fluoride. The apparent density was measured according to JIS Z 2504.

The acidic oxide has the effect of adjusting the viscosity of the slag and as an arc stabilizer, and if it is less than 0.1%, these effects cannot be obtained. On the other hand, if it exceeds 1.0%, the amount of oxygen in the weld metal increases and the toughness deteriorates, which is not preferable. Therefore, the range is 0.1 to 1.0%. SiO ₂ as the acidic oxide,
Al ₂ O ₃ , TiO ₂ , ZrO ₂ etc.

Arc stabilizers are oxides and carbonates of alkali metals such as K, Na and Li, and rare earth compounds such as Ce and La.
If it is less than the above, the effect as an arc stabilizer cannot be obtained. on the other hand
If it exceeds 0.3%, the amount of spatters increases and the amount of fumes increases, which is not preferable. Therefore 0.
The range is from 05 to 0.3%.

As the deoxidizing agent in the wire of the present invention, Si, Mn, Al, Ti, Mg
Etc. are added, but the addition amount is 1 to 5%. If the addition amount of these deoxidizers is less than 1%, the deoxidation becomes insufficient, and the weld metal becomes porous and the X-ray performance deteriorates. On the other hand, if added in excess of 5%, a large amount of deoxidizer is retained in the weld metal,
The weld metal hardens, resulting in a decrease in toughness and crack resistance. Therefore, in the wire of the present invention, the deoxidizing agent in the flux is 1 to 5
The range is%. Further, 0.5 to 10% of one or more of iron powder and alloying agent is added. Iron powder is for the purpose of increasing the welding speed, and by adding Ni, it is possible to further enhance the low temperature toughness at -60 to -80 ° C level, and Cr is capable of enhancing the high temperature strength and for the purpose of improving weather resistance. It is also possible to add a small amount of Ni, Cr, Cu. In addition, small amounts of Ti and B can be added for the purpose of obtaining TCOD performance. The addition amount of these is
The range is 0.5 to 10%.

As the wire sheath, low carbon steel within the compositional regulation range is used, but low alloy steel or high alloying steel satisfying the compositional regulation range can be used.

In the present invention, the filling rate of the flux with respect to the wire weight
The range was set to 10-30%. If it is less than 10%, a sufficient amount of the slag forming agent cannot be included, and the welding workability cannot be satisfied. On the other hand, if it exceeds 30%, on the contrary, the amount of slag becomes excessively large, which deteriorates the welding workability and causes many troubles such as disconnection during wire production, which is not preferable.

There is no restriction on the cross-sectional shape of the wire, and in the case of a diameter of 2 mmφ or less, a relatively simple cylindrical shape is used.
In the case of a large-diameter wire of about 3.2 mmφ, a structure in which a sheath material is complicatedly folded inside is generally used. Further, it is also effective to subject the surface of the seamless wire to a plating treatment such as Cu. Furthermore, mild steel and high-strength steel are generally used as the steel types to be welded, but it is also possible to apply them to the welding of low-alloy steel, high-alloy steel, etc. depending on the application.

〔Example〕

Table 1 shows the composition of the steel shell used for the trial production in Table 2
Table 3 shows the composition of the wire flux and Table 3 shows the test results. In the table, Nos. 1 to 5 are comparative examples, and Nos. 6 to 14 are examples of the wire according to the present invention.

Using the steel outer shell shown in Table 1, all of them were finished into 1.2mmφ wire, and JIS SLA33B25mmt low temperature steel plate with 50 ° V
The composition and mechanical properties of the weld metal were investigated by assembling in the groove with 270A and performing 5-pass 7-pass welding. The shielding gas is 80% Ar ・ 20.
A mixed gas of% CO ₂ was used.

As is clear from the test results of Table 3, the wires of Nos. 1 to 5 having the outer skin and the flux composition outside the scope of the present invention had a transition temperature of about -40 ° C and no improvement in toughness was observed. Also
No. 4 has the outer skin component and the flux composition within the present invention, but the flux filling rate is low, so the slag encapsulation is poor, the arc becomes unstable, and the nitrogen content in the weld metal is high at 55 ppm, resulting in toughness. No improvement was observed. On the other hand, No. 6
All of the wires according to the present invention of 14 have all transition temperatures −
It was confirmed that the low temperature toughness was good because the temperature was 60 ° C or less.

[Advantages of the Invention] The present invention is configured as described above, and in particular, by regulating the apparent density of metal fluoride, it is possible to significantly improve the productivity of the wire and reduce the fluctuation of the flux filling rate. Became possible. Further, it has become possible to provide a flux-cored wire for gas shielded arc welding, which can obtain good low temperature toughness by combining the outer skin component and the flux composition and can achieve high grade and high toughness.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the apparent density of metal fluoride and the variation of the wire production yield and the flux filling rate.

Claims (1)

[Claims] [Claim 1] The composition of the steel shell is C: 0.06% or less (wt%: the same below), P: 0.009% or less, Mn: 0.2 to 1.2%, N: 0.0040%
Metal fluoride with an apparent density of 1.3 g / cm ³ or more, relative to the total weight of the wire in the cavity surrounded by the following: 1-10% acid oxide; 0.1-1.0% arc stabilizer: 0.05 -0.3% Deoxidizer: 1-5% One or more of iron powder and alloying agent: 0.5-30% flux containing 10-30% of the total weight of the wire.
A flux-cored wire for gas shielded arc welding, characterized by being filled.