JPS6351762B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a welded pipe made of titanium, zirconium, or an alloy thereof. Titanium, zirconium, or their alloys (hereinafter referred to as
When manufacturing tubes using materials such as titanium,
After forming a plate-shaped hoop of material into an oven tube by passing it between each forming roll, the joining edge is welded near the squeeze roll, and then the outer diameter is adjusted using multiple sizing rolls to continuously form the tube. Methods of manufacturing are known. Although the amount of reduction in the outer diameter of the welded pipe by the sizing roll affects the outer diameter tolerance and roundness of the product, the amount of reduction in the outer diameter of the welded pipe made of titanium or the like has not been sufficiently studied. steel pipes and
The experience with SUS pipes was directly utilized. By the way, in the manufacture of welded titanium pipes, etc., relatively soft copper alloy rolls are used to prevent seizure.
%), there was a problem that the sizing reduction amount was larger than necessary and the copper alloy rolls were severely worn. The present invention has been made in view of the above points, and its purpose is to provide a necessary and sufficient outer diameter for adjusting the tolerance and roundness of the outer diameter of the pipe when manufacturing welded titanium pipes, etc. The purpose of the present invention is to provide a method for manufacturing welded pipes made of titanium, etc., in which the amount of reduction is determined and applied to drawing rolls such as sizing rolls, thereby preventing wear caused by unnecessary reduction of the rolls. Titanium, zirconium,
Or, after forming a plate-shaped houb made of the alloy into an oven tube by passing it between forming rolls, welding the joining edge near the squeeze roll, then adjusting the outer diameter with multiple sizing rolls and forming the tube into an oven tube. In the method for continuously manufacturing , the total amount of outer diameter reduction from the squeeze roll to the final sizing roll is set at 1 to 2% and distributed to each of the rolls. The present invention will be explained in detail below. First, the outline of the manufacturing process of a welded pipe made of titanium or the like will be explained based on the embodiment shown in FIG. FIG. 1 shows a forming process, in which a strip hoop 1 made of titanium or the like is rolled onto seven forming rolls F.
1 to F7 to form a circular oven tube. FIG. 1 shows a welding process, in which the edge joints of the oven tube are welded in the longitudinal direction after the forming process is completed,
A squeeze roll SQ that controls the oven tube offset amount and edge butt shape,
Placed either before or after squeeze roll SQ
It consists of a TIG welding torch 2. Figure 1 shows the sizing process, in which the pipe after welding is rolled by sizing rolls F8 to F11 consisting of four rolls each having a perfect circular hole diameter.
It passes through to finish the outer diameter tolerance and roundness. In the figure, 3 indicates an uncoiler and S indicates a side roll. Next, the reason why the total amount of outer diameter reduction from the squeeze roll to the final sizing roll is set to 1 to 2%, which is the gist of the present invention, will be explained in detail. This is based on a mock test using the mold described below, which was conducted to understand the appropriate sizing conditions for welded titanium pipes (hereinafter referred to as titanium pipes) after passing through a squeeze roll. This is because if the amount is less than 1%, the roundness cannot be improved, and if it exceeds 2%, the contact length between the roll and the tube becomes longer and roll wear becomes severe. The method, results, and ideas for the mock test using the above-mentioned model will be explained. [Test method] (1) Test material A 22〓×0.7 ^t mm titanium tube was molded with a sizing roll completely floating, and a tube with poor roundness immediately after welding was sampled and used as the test material. (2) Shape of test piece and mold The test piece used was a sample material cut into approximately 50 ^l mm and the end surface polished with emery paper. In this experiment, six types of carbon steel (S45C-
N) A mold was used, and its hole diameter is shown in Table 1. Table 1 also shows the nominal reduction ratio when rolling down using each mold, but these values were calculated from the average outer diameter of the test piece and the hole diameter. All sample materials were sampled by continuous molding, so
All specimens used in this test had approximately equal average outer diameters.

[Test results and ideas]

FIG. 2 shows the relationship between the hole diameter and the outer diameter of the titanium tube after sizing. In the figure, the horizontal axis shows the hole diameter (mm) and the nominal drawing ratio (%) shown in Table 1, and the vertical axis shows the titanium tube outer diameter (mm). The outer diameter of the titanium tube was measured by a six-point method, and the average value, maximum, and minimum values are shown in the figure. In the figure, if you look at the outer diameter tolerance (maximum diameter - minimum diameter), the outer diameter tolerance of the material was about 0.5 mm, but when the nominal reduction rate is applied to a reduction of 0.7% or more, it becomes less than 0.1 mm. Become. on the other hand,
The average outer diameter is slightly larger than the hole diameter, and when the reduction rate is 1% or more, the difference between the two is uniformly about 0.07 mm.
This value is considered to be largely due to the elastic recovery of the titanium tube, since the elastic deformation of the hole shape is considered to be negligible. This elastic recovery amount is approximately 0.31% when converted to circumferential strain, and this value is approximately equal to the yield strain of the titanium tube. FIGS. 3A and 3B show a roundness measurement diagram of the material pipe before rolling and after rolling, respectively. Of course, the profiles of other molds after rolling were also measured, but FIG. 3 is shown here as a representative example. In the figure, a
indicates a welded part, b indicates a profile, and c indicates a reference circle. FIG. 4 shows the relationship between nominal drawing ratio and roundness. The definition of roundness shown in the figure is the sum of the maximum deviations from the reference circle of the profile inward and outward (unit: μm), as shown in the upper part of the roundness measurement diagram of the material in Figure 3A.
given by. In Figure 4, in addition to the roundness mentioned above,
The degree of small bends (irregularities on the circumference) of the titanium tube is also shown by distinguishing the plot marks. In other words, here, the degree of small bending is judged by the number of intersections between the profile curve and the reference circle on the roundness measurement diagram, ● indicates the number of intersections is 8 or more, △ indicates the number of intersections 6 to 7, ○ indicates a case where the number of intersections is 4 to 5. Figure 3 A, B and 4
According to the figure, the roundness of the material is approximately 350μm, and when the nominal drawing ratio is less than 1%, the roundness is large and the correction is insufficient, and when it is over 1%, the roundness is almost constant at approximately 60μm, and there is no small bend. be corrected. If it exceeds 2%, correction will not be effective considering the amount of reduction. All of the above are the test results when the die reduction is carried out sequentially from → (sequential reduction), but in a test similar to this test except for the order of reduction, the material is directly reduced to the desired mold at once (single reduction). ) tests were also conducted. A detailed explanation of the results in this case will be omitted, but the conclusion is that there is almost no difference in the results of outer diameter measurement and roundness measurement between sequential rolling and single rolling. However, regarding the relationship between the rolling load and the clearance between the upper and lower dies, the shape of the curve in FIG. 5 differed depending on the rolling method. FIG. 5 is a diagram showing the relationship between the rolling load and the clearance between the upper and lower molds when the mold is rolled down, and in the figure, the solid line and the broken line indicate the cases of sequential rolling and single rolling, respectively.
In addition, a in the figure is the maximum load point and indicates the point where the clearance between the upper and lower dies is 0, and b indicates the clearance at the start of rolling. From the figure, it can be seen that the rolling load starts to increase when the clearance is larger in single rolling than in sequential rolling, in other words, as the drawing ratio increases in one mold. Applying this to the sizing roll, if the reduction amount per stand is increased, the contact length between the titanium tube and the roll hole surface will become longer, and as a result, it is expected that the wear of the copper alloy roll will increase. Ru. Therefore, it can be seen that it is more preferable from the viewpoint of preventing roll wear to equally distribute the appropriate drawing rate to each stand. The mock test using the mold is as described above, and the results were confirmed by applying the amount of outside diameter reduction based on the above results to the sizing roll of the actual machine. [Implementation method] Using 31.75〓×0.5 ^t mm as the target titanium tube,
The actual machine used was one with four sizing rolls, as shown in Fig. 1. The rolls were stopped during molding, and the titanium tubes after passing through each sizing roll F8 to F11 after the squeeze roll SQ were sampled. The outer diameter and roundness of these titanium tube samples were actually measured, and the relationship with various sizing conditions was determined. The upper and lower roll clearances are set to 0, and all pipes are new (no wear).
roll was used. [Results and Discussion] The measurement results of the outer diameter tolerance and roundness of the titanium tubes sampled as described above are shown in FIGS. 6A and 6B. In these figures, the plastic reduction rate is plotted on the horizontal axis, and this value was determined using the following formula. δ _P = | d _F / d _SQ −1 | × 100 (%) Where, δ _P : Plastic reduction rate, d _F : Average outer diameter of titanium tube after passing through each sizing roll, d _SQ : Titanium tube after passing through squeeze roll The vertical axis shows the outer diameter tolerance (mm) and roundness (μm), respectively. As is clear from Fig. 6A and B, the outer diameter tolerance,
The roundness decreases as the drawing ratio increases, and when the plastic drawing ratio is 0.5 to 0.6% or more, sufficient roundness (outer diameter tolerance) is achieved even when compared to ASTM standards. Therefore, from the results of this implementation, a value of 0.5 to 0.6% is obtained as the appropriate sizing reduction rate. As mentioned above, if the elastic recovery strain of the titanium tube is estimated to be approximately 0.31%, the appropriate sizing reduction ratio (total strain) will be 0.81 to 0.91%, and this value is close to the results obtained in mock tests using molds. . From the above results, it was confirmed that the appropriate sizing reduction rate is 1 to 2% as described in the previous section. Regarding this implementation, other titanium tubes were investigated regarding the above items, and almost the same results were obtained, and the appropriate sizing reduction ratio was 1 to 2%.
However, it was found that this method can be applied regardless of the size of the titanium tube. As described above, according to the method for manufacturing a welded pipe made of titanium or the like of the present invention, the total amount of outer diameter reduction from the squeeze roll to the final sizing roll can be reduced by 1 to 2%.
As a result, the tolerance and roundness of the outside diameter of the tube can be adjusted with high precision, and wear of the rolls due to unnecessary rolling can be prevented, making it possible to extend the life of the rolls. In addition, since the amount of outside diameter reduction can be clearly set, it is possible to optimally design the roll hole shape after the squeeze roll, taking the outside diameter reduction amount into consideration, and determine the appropriate hoop width. These incidental matters, which had previously been done through trial and error, can now be handled efficiently and contribute to improved productivity.

[Brief explanation of drawings]

Figure 1 is a schematic process diagram showing the manufacturing process of welded titanium pipes, etc. Figure 2 is a diagram showing the relationship between the hole diameter, nominal drawing ratio, and titanium pipe outer diameter, and Figures A and B are raw material pipes. Figure 4 is a diagram showing the relationship between the nominal drawing ratio and roundness, Figure 5 is a diagram showing the relationship between the clearance between the upper and lower dies and the rolling load, and Figure 6 is a diagram showing the relationship between the clearance between the upper and lower dies and the rolling load.
Figures A and B are diagrams showing the relationship between plastic reduction ratio, outer diameter tolerance, and roundness. 1... Hoop, 2... Welding torch, F1-F7... Forming roll, SQ... Squeeze roll, F8-F11
...Sizing roll.

Claims (1)

[Claims] 1. After forming a plate-shaped houb made of titanium, zirconium, or an alloy thereof into an oven tube by passing it between forming rolls, the joining edge is welded near the squeeze roll, and then a plurality of... In the method of continuously manufacturing pipes by adjusting the outer diameter with a sizing roll, the total amount of outer diameter reduction from the squeeze roll to the final sizing roll is 1 to 2.
A method for manufacturing a welded pipe of titanium, zirconium, or an alloy thereof, characterized in that the welded pipe is distributed as a percentage to each of the rolls. 2. The method for manufacturing a welded pipe of titanium, zirconium, or an alloy thereof according to claim 1, wherein the distribution is approximately equal.