JPH0645080B2 - Method for manufacturing wire containing metal powder flux - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a flux-cored wire for gas shielded arc welding, and more particularly, to the amount of slag generated which is being used recently in the welding of mild steel, high strength steel and the like. A small amount of metal powder-based flux-cored wire, in particular, a wire having a welded steel pipe as an outer shell and having a good welding feedability,
The present invention relates to a manufacturing method that can be obtained with high productivity.

[Conventional technology]

Recently, in various welded structures such as shipbuilding, steel frames, and bridges, the use of flux-cored wire for gas shielded arc welding is rapidly increasing from the viewpoint of labor saving and improving production efficiency. The so-called metal powder-based flux-cored wire, which is contained in a large amount, has a small amount of slag, and the wire welding rate is fast and efficient, so that its use is increasing.

On the other hand, in this flux-cored wire, the seamless wire produced by filling the welded steel pipe with the flux raw material has good rust resistance because it can be plated with copper, and since it has no seam, It is being used widely because of its characteristics such as less blurring during feeding.

However, when manufacturing the above-mentioned metal powder-based flux-cored wire with this seamless flux-cored wire, the conventional manufacturing method causes a small constriction in the finished wire and often causes wire breakage during wire drawing. There is a problem in that the wire speed must be greatly reduced to produce the wire, resulting in a significant increase in the wire cost, and the feedability during the welding of the finished wire is poor, which lowers the welding workability. It was

Under these circumstances, it has been desired to develop a seamless flux-cored wire which has good welding workability and good productivity.

[Problems to be Solved by the Invention]

The present invention has been made in view of the current situation as described above, and an object thereof is a wire having no constriction, good feedability, and no wire breakage at the time of wire drawing and good productivity and inexpensive. The present invention provides a method for producing a metal powder-based flux-cored wire without any joints.

[Means for Solving the Problems]

The present invention is a method of manufacturing a metal powder-based flux-cored wire in which a welded steel pipe outer shell is filled with a flux material having a metal powder content of 90% or more in an amount of 10 to 25%, and an annealing step performed during a wire drawing process. Of the metal powder flux-cored wire having a wire diameter of 2.0 mmφ or less, characterized in that the annealing temperature of the wire is within the range of the following formula (1) and the area reduction rate of the wire drawing step after annealing is within the range of 30 to 75%. The main point is the manufacturing method.

(1 set: Here, T (° C.): annealing temperature R (%): wire drawing area reduction rate after annealing [Operation] The present inventors firstly fill a welded steel pipe with a flux raw material containing a large amount of metal powder. In the case of the system wire, the phenomenon of frequent wire breakage during wire drawing was observed in the wire drawing process using an ordinary continuous wire drawing machine, and the cause was examined by cutting longitudinal sections of various wires. As a result, we found that the wire breakage during wire drawing was due to the following reasons. That is, when observing the longitudinal section of the wire that was broken during manufacturing under the conventional manufacturing conditions, the filling flux to be compressed and expanded along with the outer skin during the drawing process separated at several mm intervals, forming voids. It can be seen that it is not extended. The reason for such a state is that in the case of a normal flux-cored wire containing a large amount of non-metal components (oxides, fluorides), the fixed flux does not stick during the annealing process, and the flux powder Easily flows and is compressed and stretched together with the outer shell as the wire drawing process progresses, and the separation of the filling flux does not occur, whereas if the proportion of metal powder is large, the metal powder adheres to each other during the annealing process. The reason is that when the wire is drawn, it separates and creates voids.

The wire breakage during wire drawing as described above forms a gap and a filling part in which the flux raw material is separated during the wire drawing process, and therefore the resistance in the die shows a wavy shape. And I confirmed that the resistance was caused by a sudden increase.

Next, the inventors conducted an experiment to examine various manufacturing conditions based on the analysis of the cause of the disconnection described above, and obtained the idea that the following means are effective in preventing the disconnection, to complete the present invention. I arrived.

(1) Minimize the wire drawing workability (area reduction rate) after annealing to reduce the separation of the filling flux during wire drawing.

(2) Lower the annealing temperature as much as possible to reduce the sticking of metal powders to each other.

(3) The upper limit of the annealing temperature changes depending on the area reduction ratio of the wire drawing after annealing, and the annealing satisfies the following formula.

The structure and operation of the present invention will be described below.

First, the present invention is limited to a metal-powder-based flux-cored wire obtained by filling 10 to 25% of a flux raw material containing 90% or more of metal powder. These limitations are the original characteristics of the metal powder-based flux-cored wire, that is, the characteristics such as less slag, efficiency and good welding workability are eliminated, but the proportion of metal powder in the flux raw material is When it is less than 90%, the amount of the slag is increased because the amount of the arc stabilizer, the slag forming agent such as alkali or alkaline earth metal oxides or oxides such as TiO ₂ and SiO ₂ inevitably increases. It is not preferable because the original properties of the flux-cored wire are lost. Moreover, the upper limit of the filling rate is set to 25%. If the upper limit is exceeded, the wall thickness of the outer metal becomes too thin, the wire becomes soft, and the wire breaks under any conditions in the wire drawing process. This is because wire drawing will not be possible.

On the other hand, if the filling rate is less than 10%, it is not possible to sufficiently add and adjust the flux components such as the metal powder mainly composed of iron powder, the arc stabilizer, and the slag-forming agent component which is required in a small amount.

The reason why the wire drawing area reduction rate after annealing is limited to the range of 30 to 75% is that if it is less than 30%, the wire is too soft and buckles easily in the conduit cable during welding, resulting in poor feeding. On the other hand, if the area reduction rate exceeds 75%, it is necessary to reduce the annealing temperature to 450 ° C or less, because the metal powder particles in the filling flux adhere to each other during the wire drawing process. This is because at the time, the wires are separated, and due to this, the wires cannot be manufactured due to disconnection or become constricted wires, which deteriorates the wire feedability during welding.

If the annealing temperature is set to 450 ° C. or higher, if it is lower than this, H _{2 in} the wire during annealing will be insufficiently diffused, the amount of diffusible hydrogen in the weld metal during welding will increase, and low temperature cracking by H ₂ or This is because defects such as blowholes occur.

The upper limit of the annealing temperature is the following formula Is limited by the empirical formula obtained from many experimental data obtained by variously changing the annealing temperature (T) and the wire drawing area reduction rate (R) after annealing. This is because the above-mentioned disconnection during wire drawing frequently occurs, or the wire becomes constricted and becomes unusable.

〔Example〕

 The present invention will be described below with reference to examples.

The manufacturing conditions up to the pre-annealing step are the usual manufacturing methods shown below.

(I) The welded steel pipe used is a mild steel material having an outer diameter of 12.7 mmφ and a wall thickness of 2 mm.

(Ii) As the flux raw material to be filled in the welded steel pipe, two types of A and B shown in Table 1 were used. Among them, A indicates the mixing ratio of the flux raw materials 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 represents the compounding ratio of the usual flux-cored wire, and the amount of the metal powder added is 38%.

(Iii) The flux material was prepared by adding water glass as a binder, granulating and firing, and the particle size was 20 mesh or less.

(Iv) Flux filling of welded steel pipe is described in "Japanese Patent Publication No. 45-30937".
The vibration filling method was the same as that described in the publication. The flux filling rate was 15%.

In the experiment, the annealing temperature and the wire drawing diameter before the annealing were changed to variously change the area reduction rate of the wire drawing after the annealing. Table 2 shows the experimental conditions and the experimental results. The annealing time was 3 hours.

The experimental results show the presence or absence of wire breakage during wire drawing, the appearance of the finished wire, and the good and poor wire feedability during welding, and the diffusible hydrogen content of the weld metal [according to JIS Z3118]. Was done.

Here, the wire feedability was determined under the following welding conditions.

<Welding conditions> Polarity: DC wire (+), shielding gas: CO ₂ , 25 / min, welding current: 380A (1.6φ), 280A (1.2φ) conduit length, 3m (conduit, commercial product), straight The following can be considered from the experimental conditions and the experimental results in Table 2.

(1) NO.3, NO.6, NO.10 and NO.12 are examples satisfying all the requirements specified in the present invention, there is no disconnection at the time of wire drawing, and the finished appearance of the wire and at the time of welding. Has good wire feedability, and the amount of diffusible hydrogen is 5cc / 1
It is less than 00 g, which is satisfied as a comprehensive judgment.

(2) For NO.2, NO.5, and NO.11, the area reduction rate after annealing is 7
The annealing temperature is less than 5%, but the annealing temperature is expressed by equation (1). Since the above condition is not satisfied, many wire breaks occur during wire drawing.

(3) NO.4 satisfies the equation (1) in the annealing temperature, but since the area reduction rate after annealing exceeds 84% and 75%, this is also a large number of wire breaks during wire drawing.

(4) NO. 1, NO. 8 and NO. 9 do not satisfy the requirements of the present invention for both the annealing temperature and the area reduction rate, and there are many wire breaks during wire drawing.

(5) No. 7 cannot be used because the annealing temperature is too low, the amount of diffusible hydrogen is high, and there is a risk of cold cracking.

(6) In No. 13, the area reduction rate is too low, the wire is too soft, and buckling occurs during welding, resulting in poor feed.

(7) NO.14 and NO.15 are comparative examples in which the wire prescription is a non-metal powder type. In this case, wire drawing, wire finish appearance, wire feedability and diffusible hydrogen content are all good results. However, the amount of slag is large, and the characteristics as a metal powder-based flux-cored wire are not seen.

〔The invention's effect〕

According to the present invention, a wire breakage occurred in the conventional normal manufacturing conditions, or a constriction could not be produced, and a seamless metal powder-based flux-cored wire having a welded steel pipe as an outer shell with high productivity. Since it can be manufactured, it has a great industrial advantage.

Claims (1)

[Claims] 1. A method of manufacturing a metal powder-based flux-cored wire comprising a welded steel pipe outer shell filled with a flux material having a metal powder content of 90% or more in an amount of 10 to 25%, and an annealing step performed during a wire drawing process. Of the metal powder flux-cored wire having a wire diameter of 2.0 mmφ or less, characterized in that the annealing temperature of the wire is within the range of the following formula (1) and the area reduction rate of the wire drawing step after annealing is within the range of 30 to 75%. Production method. Where T (° C): annealing temperature R (%): wire drawing area reduction after annealing