JPH0238077B2 - YOSETSUYOFURATSUKUSUIRIWAIYANOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an improvement in a method of manufacturing a flux-cored wire for welding by filling a powdery flux into a mild steel sheath material and then subjecting it to wire drawing. An object of the present invention is to provide a method capable of manufacturing flux-cored wire for welding with stable quality without any deterioration in wire drawing workability, etc., even when the total area reduction rate is increased to 90% or more. It is something. [Prior Art] Flux-cored wire for welding is made by filling a metal sheath with powdery flux and then drawing it to a predetermined cross-sectional dimension. This method is widely used in automatic or counter-automatic welding because alloy components, etc. can be continuously supplied to the welding area together with the filler metal. By the way, methods for manufacturing flux-cored wire for welding include filling powdered flux into the inside of an ERW tube or extruded tube with a diameter of about 10 mm, and then drawing the wire to a predetermined cross-sectional dimension, and curving a steel strip into a tubular shape. A method in which powder flux is filled into the interior while forming, and then wire is drawn to a predetermined cross-sectional dimension.In the above method, the butt portions of both side edges of the steel strip curved into a tubular shape are welded by resistance welding, TIG welding, etc. A method of seam welding to close the gap at the abutting portion has been practiced, and the sheath material is mostly made of mild steel. [Problems to be Solved by the Invention] In any of the above-mentioned methods, in order to improve the flux filling workability and the uniformity of the filling rate, it is necessary to increase the diameter of the sheath material at the flux filling stage. It is more advantageous to keep it. In particular, in the above method, relatively short lengths of electric resistance welded tubes, etc., are filled with flux in batches and then drawn individually, so if productivity is to be increased, the workability of flux filling is a prerequisite. As a result, the sheath material is required to have a large diameter, and if a large diameter sheath material is used, the wire diameter cannot be reduced to the desired wire diameter unless the area reduction rate is increased. However, when the area reduction rate in the wire drawing process is high, about 90% or more,
The following problems arise. (1) Work hardening of the mild steel sheath material becomes significant, making it more likely that accidents such as wire breakage or wire breakage will occur during wire drawing, and the quality of the product wire will also deteriorate. (2) Work-hardened wires tend to cause feeding defects during welding, making it difficult to obtain a sound weld. (3) In order to avoid the problems (1) and (2) above, especially when the total area reduction rate is about 95% or more, it is necessary to
Intermediate annealing is performed twice to soften the material. However, this annealing operation not only increases manufacturing costs but also causes the problem of thermally altering the filling flux. Because of this situation, in the current manufacturing method for flux-cored wire, the dimensions of the mild steel sheath material are calculated backward from the cross-sectional dimensions of the product wire, and the dimensions of the mild steel sheath material are calculated in such a way that the reduction in area can be kept to less than 90%. are doing. However, under such restrictions, the dimensions of the mild steel sheath material cannot be made sufficiently large, and the flux filling workability and the uniformity of the filling rate cannot be significantly improved. Moreover, since the total area reduction rate cannot be increased to 90% or more, the wire drawing efficiency itself cannot be increased to a satisfactory level. [Means for Solving the Problems] The present invention alleviates the above-mentioned problems, especially the problem of work hardening that occurs when the area reduction rate during wire drawing is increased, and improves workability and productivity. The purpose of the present invention is to provide a technology that can manufacture flux-cored wire for welding with stable quality under the After filling with flux, when manufacturing flux-cored wire for welding by drawing with a total area reduction of 90% or more, () 0.001 to 0.006% by weight of N and 0.05% by weight or less are used as the sheath material.
Contains Al and (Al content/N content) is 4
or () 0.001~0.006% by weight of N and 0.1% by weight or less
Contains Ti and (Ti content/N content) is 10
The gist lies in the use of the above-mentioned mild steel. [Function] In order to uniformly and stably perform the flux filling operation at a high speed of 80 m/min or more, the size of the flux filling opening (in the case of ERW pipes, the inner diameter of the pipe, etc., When filling flux in the process of bending, the upper opening width of the U-shaped steel strip should be larger; in the former case, the inner diameter should be 7 mm.
In addition to the above, in the latter case, it is desirable that the opening width be 8 mm or more. The filling rate of flux is originally determined largely by the type of flux, but conversely, the filling rate of flux is influenced by the thickness of the sheath material. For this reason, various sheath materials are used depending on the product brand, but generally the sheath material is around 1.5 mm for electric resistance welded pipes, and around 0.6 mm for steel strips. However, for example, when using an electric resistance welded pipe with an inner diameter of 7 mm and a wall thickness of 1.5 mm, if we draw it to a diameter of 1.2 mm or less, the total area reduction rate will exceed 98%, and the sheath material The above-mentioned problems arise due to work hardening. On the other hand, in order to avoid such problems, the inner diameter and wall thickness of the electric resistance welded tube must be kept considerably small, and as mentioned above, the workability of flux filling and the uniformity of the filling rate are reduced, and the It also becomes impossible to increase wire drawing efficiency. Since it is clear that the cause of such problems is "work hardening of the sheath material," the present inventors have conducted research to suppress this work hardening and improve elongation. After conducting various basic experiments, we found that the elongation during processing significantly changes depending on the amount of N, Al, and Ti contained in the mild steel sheath material.
We learned that if mild steel containing Ti and Ti is used as a sheath material, work hardening during wire drawing can be suppressed and elongation can be significantly increased. By the way, Ti is sometimes added in small amounts as a grain refining element in various steel materials, but as far as mild steel is concerned, Ti is almost never added for this purpose, and N and Al are rather added as impurity intervening elements. It is recognized that it is a substance, and it is thought that it is preferable to keep its amount as small as possible. However, the inventors have confirmed through various experiments that there are small amounts of N and Al in mild steel.
Alternatively, there is a fact that if N and Ti are actively contained, work hardening of the sheath material is suppressed and large elongation can be obtained. In order to effectively exhibit these effects, [] When containing N and Al, the amount of N should be 0.001 to 0.006% by weight, and the amount of Al should be 0.05% by weight.
and (Al content rate/N content rate: hereinafter simply referred to as Al/N) should be 4 or more, and [ ] When N and Ti are included, the N amount is 0.001 to 0.001.
0.006% by weight, the amount of Ti is 0.10% by weight or less, and (Ti content/N content: hereinafter simply referred to as Ti/N)
We found out that it is sufficient to set the value to 10 or more. By the way, Fig. 1 shows steel strips A to E of Examples described later.
We used various mild steel strips (width 8 mm, thickness 0.mm) with different Al/N and Ti/N, including titania flux (filling rate 15%), and the horizontal axis shows Al/N and Ti. /N, the vertical axis (left side) is a wire diameter that can be stably obtained without intermediate annealing, and is a graph showing the results of investigating the relationship between the two. In addition, in FIG. 1, the vertical axis on the right side shows the total area reduction rate. In addition, the lower right region (A) of the curve obtained by connecting the measured values indicates the region where wire drawing can be performed stably, and the upper left region (B) indicates the region where wire drawing can be performed stably. Indicates areas where problems occur. As is clear from Figure 1, Al/N and Ti/
As N increases, wire drawability improves, but based on 1.2 mmφ wire, which is a typical small-diameter flux-cored wire for welding, Al/ N and
Ti/N is 4 or more in the former case and 10 or more in the latter case.
In other words, by containing 4 times or more of Al or 10 times or more of Ti relative to the amount of N, it is possible to produce flux-cored wire of high and stable quality with high productivity without causing accidents such as wire breakage during wire drawing. It can be manufactured smoothly under the following conditions. In Figure 1, [N and
The graph shows the tendency when two elements [Al] and two elements [N and Ti] are contained independently, but even better effects can be obtained by containing them so that the above conditions are simultaneously satisfied. What can be obtained is also clear from the examples described later. Although the reason for this remarkable tendency is not necessarily clear, it is possible that N in mild steel is caused by Al or Ti.
It is presumed that a suitable amount of nitride (AlN or TiN) is formed and this suppresses work hardening during wire drawing. By the way, if the amount of N in mild steel is less than 0.001% by weight, or if Al/N is less than 4 or Ti/N
If it is less than 10, the above effects will not be sufficiently exhibited, and when the total area reduction rate is increased to 85% or more, work hardening will be significant, making it impossible to sufficiently increase the wire drawing speed. However, if the amount of N in the mild steel exceeds 0.006% by weight, the impact properties of the mild steel itself will deteriorate and formability will deteriorate, and the amount of N in the weld metal will increase, resulting in a decrease in impact resistance. This is undesirable as it may cause defects, and if the Al content exceeds 0.05% by weight or the Ti content exceeds 0.1% by weight, the tensile strength of the weld metal will become excessive and the impact value will decrease, so the respective set values should be adjusted accordingly. Must be kept below. As described above, the present invention is characterized by containing specific amounts of N and Al or N and Ti in the mild steel sheath material, which can suppress work hardening during wire drawing. Even so, if the total area reduction rate exceeds 98%, work hardening may progress and lead to wire breakage accidents. Therefore, when performing such high surface reduction processing, it is best to perform intermediate annealing.
The preferable intermediate annealing temperature at this time is preferably about 500 to 700°C in order to prevent thermal deterioration of the filling flux. In addition, considering the fact that in the conventional case, if the total area reduction rate was to be about 98% or more, it was necessary to perform intermediate annealing at least once or twice, it is necessary to carry out such high area reduction processing by intermediate annealing. It can be said that the technical significance (productivity and suppression of thermal deterioration of the filling flux) of being able to perform intermediate annealing without or in most cases with one intermediate annealing is extremely large. [Example] The mild steel sheath material shown in Table 1 and the titania-based filling flux were combined as shown in Table 2, and the flux filling and wire drawing were performed according to the usual method, and wire breakage occurred during wire drawing. Rate [Number of disconnections/Volume (10 tons)]
compared. The results are summarized in Table 2.

【table】

[Table] From Tables 1 and 2, the following can be considered. Sheath material A is a comparison material in which both Al/N and Ti/N are outside the specified requirements of the present invention, and in the experimental examples (Nos. 1 and 8) using this sheath material A, the occurrence of wire breakage was low in both cases. is getting higher. In particular, when an electric resistance welded tube is used as the starting material (No. 8), the incidence of wire breakage is high even when intermediate annealing is performed twice. Regarding Nos. 6, 7, and 11, Al/N and Ti/N are within the specified range of the present invention, but the amounts of Al and Ti are outside the scope of the present invention, and the performance (especially impact properties) as a weld metal is different from that of the present invention. inferior to. On the other hand, in the sheath materials B to E, one or both of Al/N and Ti/N satisfies the specified requirements,
Experimental examples using these sheath materials (No. 2 to 5, 9,
10), the incidence of wire breakage has been drastically reduced in all cases. On the other hand, regarding No. 12 with smaller sheath material dimensions,
Although the wire breakage rate and weld metal performance are both satisfactory, the flux filling workability is significantly inferior to the others, and the overall evaluation is poor. [Effects of the Invention] The present invention is configured as described above, but the point is that work hardening during wire drawing is achieved by incorporating specific amounts of N and Al and/or N and Ti into the mild steel sheath material. By suppressing this and increasing growth, we can enjoy many benefits as shown below. (1) Since there is little work hardening during wire drawing, accidents such as wire breakage during wire drawing are drastically reduced, and safety and productivity can be improved accordingly. (2) Since the area reduction rate during wire drawing can be increased, it is possible to increase the pipe diameter (or the opening width of the U-shaped steel strip) during flux filling, which improves flux filling workability and filling rate. In addition to improving the uniformity of wire drawing, the wire drawing efficiency can also be greatly increased. (3) As long as the area reduction rate is set to about 95% or less, intermediate annealing is not required at all, which reduces equipment costs and simplifies production management, and also eliminates thermal alteration of the filling flux due to annealing, resulting in high quality. flux-cored wire can be obtained. (4) If the work hardening of the sheath material is severe, the product wire may not be properly straightened, resulting in decreased feedability and arc instability, making it impossible to obtain a sound weld. However, in the present invention, Since work hardening of the sheath material is suppressed, such problems do not occur.

[Brief explanation of drawings]

FIG. 1 is a graph of experimental results showing the relationship between Al/N and Ti/N in the mild steel sheath material and the wire diameter that can be stably obtained without intermediate annealing.

Claims (1)

[Scope of Claims] 1. In manufacturing a flux-cored wire for welding by filling a powdery flux into a mild steel sheath material and then subjecting it to a wire drawing process with a total area reduction of 90% or more, the sheath material contains 0.001 A method for producing a flux-cored wire for welding, characterized in that a mild steel containing up to 0.006% by weight of N and 0.05% by weight or less of Al, and having a ratio of (Al content/N content) of 4 or more, is used. 2. When manufacturing a flux-cored wire for welding by filling a powdery flux into a mild steel sheath material and then drawing the wire with a total area reduction of 90% or more, the sheath material contains 0.001 to 0.006% by weight. Contains N and 0.1% by weight or less of Ti, and (Ti content / N content)
1. A method for producing a flux-cored wire for welding, characterized by using mild steel having a grade of 10 or more.