JP2742957B2 - Manufacturing method of metal powder based flux cored wire - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for manufacturing a flux-cored wire for gas shielded arc welding, and more particularly to slag generation which is being used in welding of mild steel, high tensile steel and the like. The present invention relates to a method for producing a metal powder-based flux-cored wire having a small amount, particularly a wire having a good weld feedability without a seam formed between a welded steel pipe and an outer skin with high productivity.

(Prior art) Recently, in various welding structures such as shipbuilding, steel frames, bridges, etc., the use of flux-cored wires performed by gas shielded arc welding has been rapidly increasing in terms of labor saving and improvement of production efficiency. The use of so-called metal powder flux cored wire, which contains a large amount of iron powder in the wire, has the advantages of low slag generation, high wire welding speed, and high efficiency. is there.

On the other hand, in this flux-cored wire, a seamless wire manufactured by filling a welded steel pipe with a flux material has good rust resistance due to the possibility of steel plating, and has no seam. It has the advantage of less blurring during feeding and is widely used.

However, when the above-mentioned metal powder type flux cored wire is manufactured using the flux cored wire having no joint, the conventional manufacturing method causes a small constriction in the finished wire, or the wire breakage occurs frequently during the wire drawing. There is a problem in that the wire speed must be significantly reduced to produce the wire, resulting in a remarkable increase in wire cost, and also a poor feedability during welding, resulting in a decrease in welding workability.

The present inventors have already proposed a method for solving this problem in Japanese Patent Application Laid-Open No. 1-249298, but this method sinters the filler wax inside the wire during annealing performed during the wire drawing process. In order to prevent disconnection during wire drawing due to
The annealing temperature is low and the wire drawing reduction rate after annealing is severely limited. As a result, the annealing time for the purpose of softening and dehydrogenating the wire becomes longer and the diameter of the annealed wire becomes thinner. It has been found that there is a problem in that the diameter of the plated wire becomes smaller, and the productivity in the annealing and plating steps is deteriorated.

(Problems to be Solved by the Invention) The present invention aims to improve the problems of the method proposed in JP-A-1-249298 and to provide a more excellent method as described above. However, it is an object of the present invention to provide a method for producing a low-price metal powder-based flux-cored wire that is free from constriction, has good feedability, has no break during drawing, and has good productivity.

(Means for Solving the Problems) That is, the gist of the present invention is that a metal powder-based flux cored wire obtained by filling a welded steel pipe with a flux raw material having a metal powder ratio of 80% or more at 25% or less. In performing the annealing during the drawing process after filling the flux, the annealing temperature is 650 to 850 ° C., and the annealing time is a short time of 10 minutes or less.
A method for producing a metal powder flux cored wire having a diameter of 2.0 mm or less.

In the practice of the present invention, a flux raw material is granulated as a filling flux, dried and then fired at a temperature of 300 ° C. or higher, or used as a non-granulated method. By using a filling flux mixed with the above and filling the welded steel pipe in a vacuum, a wire having even better welding performance can be obtained.

(Operation) The configuration and operation of the present invention will be described below.

In the method for producing a flux-cored wire containing a large amount of metal powder, as already described in JP-A-1-249298, if the proportion of metal powder in the filling flux is large, the annealing process after drawing is performed. During the wire drawing, the filling flux does not follow and flows during the wire drawing, and separates to form voids, thereby increasing the fluctuation resistance at the time of wire drawing and leading to disconnection. . In order to prevent this, in the method proposed in Japanese Patent Application Laid-Open No. 1-249298, the annealing temperature is lowered (the maximum temperature in the example of the invention, 550 ° C.), and the wire drawing reduction rate after annealing is strictly limited (the invention practice). The maximum wire drawing reduction rate in the example was 70%).

The present invention is characterized in that the annealing temperature during annealing during the drawing process after filling the flux is 650 to 850 ° C., and the annealing time is a short time of 10 minutes or less. Even if it is as short as 10 minutes or less, there is little sticking of metal powder to each other, it does not lead to breakage at the time of drawing, and the hardening of the outer skin due to drawing raises the annealing temperature to 650 ° C or more even with a short annealing time. It has been found that if the height is increased, the wire is sufficiently softened and can be drawn in the subsequent drawing step under the same high-speed condition as a general nonmetallic wire. In the short-time annealing, which is a requirement of the present invention, the annealing temperature needs to be 650 ° C. or more to sufficiently obtain the effect of softening. However, if the temperature is higher than 850 ° C., the skin and the filling wax deteriorate, which is not preferable. Also, as for the annealing time, a sufficient softening effect can be obtained even with an extremely short holding time of 1 to 2 seconds. However, holding for more than 10 minutes is not preferable because sintering of the filling flux occurs and causes disconnection during drawing. In addition, the annealing time is preferably within 10 minutes within a short range on the high-temperature side and a long range on the low-temperature side. Can be longer than in the case of. As a short-time annealing method, a high-frequency induction heating method, a direct current heating method, or an indirect heating method using gas or electric heat can be adopted.

When this short annealing time is employed, if the moisture content of the filling flux is large, the amount of residual hydrogen in the wire is increased, and defects such as pits, blow holes or weld cracks due to hydrogen are generated in the welded portion. Therefore, countermeasures are needed. As one of the countermeasures, it can be solved by granulating the flux raw material with water glass as in the past, drying it, and further baking it at 300 ° C. or higher to reduce the water content and use it as a filling flux. In this case, the water content can be reduced by reducing the amount of water glass as much as possible, and the longer the firing time, the lower the water content. As another method, the problem can be solved by filling various kinds of flux raw materials only by mechanical mixing without granulating with water glass. However, in the latter case, it is necessary to reduce the water content of the raw material itself as much as possible and use a raw material that does not substantially contain water (for example, 0.02% or less in water content). Such raw materials cannot be used. Furthermore, it is generally necessary to use fine-grained materials as raw materials, and when they are filled only by mixing them mechanically, filling in a vacuum is difficult because of the ease of removal and filling of adsorbed water on the raw material surface. Need a way. This vacuum filling method is a method in which the entire system from the flux supply container to the inside of the welded steel pipe is evacuated and filled by vibration, and can be easily made into an apparatus. In the case of vacuum filling, a raw material having a lower hydrogen content can be obtained by sufficiently drying the raw material immediately before filling or firing a raw material having a high water content at a high temperature to reduce the water content and then filling. . By using a wire made by these methods, a blow hole due to moisture and a crack due to hydrogen are eliminated in the welded portion, and good welding performance is exhibited.

The present invention is limited to a metal powder-based flux-cored wire filled with a flux raw material having a metal powder ratio of 80% or more at 25% or less. Due to these limitations, the inherent characteristics of the metal powder based flux cored wire, that is, characteristics such as low slag generation, high welding speed, high efficiency and good welding workability, are produced. On the other hand, when the ratio of the metal powder in the flux raw material is less than 80%, the arc stabilizer and the slag forming agent such as alkali or alkaline earth metal oxide or TiO ₂ , SiO
_{Since the} amount of oxides or fluorides such as ₂ increases, the amount of slag increases, and the original characteristics of the metal powder-based flux cored wire are lost, which is not preferable. Also, the upper limit of the filling rate is 25%
The reason for this is that if the thickness exceeds this, the thickness of the outer cover metal becomes too thin, and the wire is broken under any practical conditions in the wire drawing process, and the wire cannot be drawn.

(Example) Hereinafter, a method for manufacturing the wire of the present invention will be described in detail with reference to examples.

The manufacturing method up to the pre-annealing step except for the granulation step is performed by the following general manufacturing method.

(1) The original welded steel pipe used is mild steel with an outer diameter of 12.7 mm and a wall thickness of 2 mm. (2) Two kinds of flux materials A and B shown in Table 1 were used as flux raw materials to be filled in the welded steel pipe. A indicates the mixing ratio of the flux raw material of the metal powder-based flux cored wire targeted by the present invention, and the total amount of the metal powder added is 95%. B indicates the compounding ratio of ordinary flux-cored wire, and the total amount of metal powder added was 38.
%. (3) The flux raw material was prepared by adding water glass as a binder in the case of granulation, granulating and drying, and in the example of the present invention, sintering, and the particle size was 20 mesh or less. In the case where granulation was not performed, mechanically mixed one was used as it was. (4) The flux filling to the welded steel pipe was performed by the same vibration filling method as the method described in JP-B-45-30937. In addition, the filling method in a vacuum was performed by a device modified from the above-mentioned vibration filling device so that the flux could be filled in a vacuum system. Flux filling rate is 15%
And (5) The finished wire diameter is 1.2 mm.

Table 2 shows the manufacturing conditions of the wires such as the granulation conditions, the filling method and the annealing conditions, the manufacturing results under those conditions, and the welding results with the finished wires.

As a method of short-time annealing, a high-frequency induction heating method is used as a heating method within 10 seconds, a continuous annealing furnace using gas heating for a heating time longer than 15 minutes, and a batch heating method using electric heating for more than 1 hour. The test was performed in an annealing furnace.

The production results are indicated by the presence or absence of breakage during wire drawing and the appearance of the finished wire. The results of welding with the finished wire indicate good and poor wire feedability during welding, bead appearance, and diffusible hydrogen content of the weld metal [JIS Z 3118], and a comprehensive judgment was made for all of them.

Here, the determination of wire feedability was performed under the following welding conditions.

<Welding conditions> Polarity: DC wire (+), Shielding gas: CO ₂ , 25 / min, Welding current: 280A (1.2φ), Conduit length, 3m (Conduit, commercial product), Straight Manufacturing conditions in Table 2 The following can be considered from the manufacturing results and the welding results with the finished wires.

(1) No. 1, No. 2, No. 9 to No. 11 are examples that satisfy all the requirements specified in the present invention, the wire is not broken at the time of drawing, the finished appearance of the wire and the The wire feedability and the bead appearance are good, and the diffusible hydrogen is 5 cc / 100 g or less, which satisfies the overall judgment sufficiently.

(2) No. 3 satisfies all the conditions except the annealing time in the comparative example. However, since the annealing time is as long as 14 minutes and the annealing temperature is high in relation to the annealing time, the internal flux is low. Tie
Disconnection occurs due to poor drawability.

(3) No. 4 to No. 5 are also comparative examples in which granulated fluxes not fired at a high temperature and low annealing temperatures resulted in high diffusible hydrogen content, and thus pits were generated.

(4) No. 6 has good performance of the finished wire, but while reducing the annealing temperature and lengthening the annealing time to prevent breakage during drawing, the annealing wire diameter is reduced to 2.2 mm, and mm
The wire drawing reduction rate up to the finished diameter of
The productivity in the annealing and plating steps is low. No.7
This is an example in which disconnection frequently occurred due to a large wire reduction ratio from the diameter at the time of annealing to the diameter at the time of finishing. No. 8 is an example in which disconnection occurred frequently because the annealing temperature was high in relation to the annealing time.

(5) No. 12 is an example in which only the mechanical mixing without granulation of the filling flux was carried out and the vacuum filling method was used. There are pits due to hydrogen.

(6) In No.13, the filling flux is a mechanically mixed one, but the filling method is not a vacuum filling method but a normal method. Since the filling flux is made of fine-grained raw materials, it has poor fluidity and is long. This is an example in which filling could not be performed even if time was required.

(7) No. 14 is an example in which the annealing time was long, the sintering of the filling flux inside occurred, and wire breakage occurred frequently during wire drawing.

(8) No. 15 is an example in which the annealing time was too long, and the filling flux was sintered, resulting in frequent wire breakage during wire drawing.

(9) No. 16 is an example where the flux formulation is a non-metallic powder type. This is an example in which the moisture content is high due to the large amount of non-metallic components, the diffusible hydrogen content is high, and the slag content is large, so that the original characteristics of the metal powder flux cored wire could not be obtained.

(Effects of the Invention) According to the present invention, the disadvantages of the method proposed in Japanese Patent Application Laid-Open No. 1-249298 are that the annealing time is long and the annealing wire has a small diameter, so that the productivity of the annealing and plating steps is low. Flux-cored wire with seamless seam of welded steel pipe, characterized by the ability to solve the whole problem, copper plating, good rust resistance, and less seam due to no seams. Can be manufactured at low cost, and the industrial benefit is extremely large.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Isao Sugioka 7-6-1, Higashi Narashino, Narashino City, Chiba Prefecture Nippon Welding Industry Co., Ltd. JP-A-49-41246 (JP, A) JP-A-59-61597 (JP, A) JP 2-7759 (JP, B2)

Claims (3)

(57) [Claims] In a method for manufacturing a metal powder type flux cored wire in which a welding material is filled with a flux raw material having a metal powder ratio of 80% or more at a rate of 25% or less, during a wire drawing process after filling the flux. A method for producing a metal powder flux-cored wire having a wire diameter of 2.0 mm or less, wherein the annealing temperature is 650 to 850 ° C. and the annealing time is a short time of 10 minutes or less when performing annealing. 2. The method for producing a metal powder type flux-cored wire having a wire diameter of 2.0 mm or less according to claim 1, wherein the flux material is granulated and dried, and then fired at a temperature of 300 ° C. or more. . 3. A wire diameter of 2.0 mm according to claim 1, wherein a raw material substantially free of water is used as the filling flux, and the mixture is mechanically mixed without granulation, and then filled into a welded steel pipe in a vacuum. The following method for producing a metal powder flux cored wire.