JPS63157719A - Manufacture of rectangular pipe - Google Patents

Abstract

PURPOSE:To prevent seizures of die and plug and to manufacture a rectangular pipe excellent in accuracy of dimensions by specifying relations between an inlet shape of the die and throttle angles of the side parts and corner parts and the inclination angle of the plug, then by reducing a diameter of a circular pipe. CONSTITUTION:In the state of drawing the base pipe (circular pipe) through the die and plug to make the rectangular pipe while reducing the diameter, the inlet shape of the die is made large than the prescribed rectangular pipe and the rectangular shape is made larger in its length of the diagonal line than the diameter of the base pipe. Furthermore, the difference between the maximum values of the side parts and the throttle angles theta1, theta2 of the corner parts is made to become within 15 deg.. More, the inclination angle of the side parts of the plug is made by 2-10 deg., the inclination angles phi1, phi2 of the corner parts is made by 1-5 deg.. Both or one of them of the die and plug of these shapes are used. In this way, even if relatively at high reductions, the rectangular steel pipe, etc., are manufactured without generating any seizure of the die and plug.

Description

[Detailed description of the invention] (Industrial application field) The invention is based on a diameter reduction method using a die or a die and a plug for an electric resistance welded pipe, a forge welded pipe, a seamless pipe, or a round pipe manufactured by other methods. This invention relates to a method for manufacturing square tubes.

(Prior Art) In general, methods for manufacturing square steel pipes can be broadly classified into two types. One is to form a steel strip of a predetermined width into a tube by roll forming using several stages of stands, and then contact it with a bath to form a round tube. This method then uses several stages of restrictors to continuously manufacture square tubes from round tubes. This method is commonly used and has the advantage of being highly efficient and low-cost manufacturing, but it is disadvantageous when manufacturing many sizes in small quantities because it uses several stages of stands that match the shape. . Another method is to manufacture a rectangular steel pipe by reducing the diameter of a round pipe produced by an electric resistance welding pipe, a forge welded pipe, seamless growth, or other methods using a die or a die or a plug. This method has the advantage that square tubes of various shapes can be manufactured efficiently even in small quantities if dies and plugs are available. However, if the reduction is too large, particles will stick to the die and plug, significantly deteriorating the quality of the pipe. For this reason, depending on the shape of the rectangular tube, it may be necessary to draw the tube twice; the diameter of the round tube is reduced once to a predetermined shape, and then the diameter is reduced again to produce a predetermined rectangular tube. This is inefficient and extremely costly.

In order to avoid this, it is necessary to lower the beam reduction until no seizure occurs, but in this case, the dimensional accuracy is poor and it is difficult to manufacture products with high dimensional accuracy.

(Problems to be Solved by the Invention) As mentioned above, it is possible to process ERW pipes, forge welded pipes, seamless pipes, or round pipes manufactured by other methods using the ZED diameter method using a die or a die and a plug. In the method of manufacturing square steel pipes, if the beam reduction is large, seizure will occur locally, which will greatly impede efficiency and dimensional accuracy. Therefore, it was necessary to use a reduction that does not cause burn-in, or to lower the reduction at the expense of dimensional accuracy.

The present invention is a method for manufacturing rectangular steel pipes using a diameter reduction method using dies or dies and plugs from ERW pipes, forge welded pipes, seamless pipes, or round pipes manufactured by other methods, which is relatively cost effective. The object of the present invention is to provide a die 5 plug that does not cause burn-in even during reduction.

(Means for Solving the Problems) The present invention provides a method for manufacturing a square tube by a diameter reduction method using a die from a round tube or a die and a plug, in which the shape of the die inlet is made larger than that of a predetermined square tube, and The length of the diagonal is larger than the main pipe diameter, and the sides and corners have a constant drawing angle in the drawing direction, and the drawing angle of the sides and corners is θ.
A die for manufacturing square tubes with a difference between the maximum and minimum values of 2 within 15 degrees, and an inclination angle of the sides between 2 degrees and 10 degrees.
, a rectangular tube manufacturing method characterized in that one or both of the square tube manufacturing plugs having corner inclination angles ψl and ψ2 of 1° to 5° are used.

The present invention will be explained in detail below. FIG. 1 is a diagram showing a method of reducing the diameter from a round tube to a square tube. The main tube (round tube) is passed through a die and a plug to reduce its diameter and become a square tube. In this method of reducing the diameter from a round tube to a square tube, the reduction is different in each part in the circumferential direction, and there are parts where the reduction is very high and parts where the reduction is very low. If the reduction is high, the surface pressure applied to the die and plug will be high, causing seizure, and if the work hardening of the material is high, cracks will occur during drawing or the pipe will break. On the other hand, if the reduction is low, the shape and dimensional accuracy will be poor.

In particular, it becomes impossible to manufacture rectangular tubes with strict dimensional accuracy in terms of the smoothness of the sides and the accuracy of the radius of the corners.

The present invention attempts to optimize the shapes of the die and plug in order to solve these problems. FIG. 1 shows a die of the present invention. -First, the inlet shape of the die is made into a rectangular shape that is larger than the prescribed square steel pipe and whose diagonal length is larger than the diameter of the main pipe. This has a large reduction on the edges,
In order to make the processing uniform, the sides are processed first, and as a result, (mother pipe diameter ≧ diagonal length of square pipe)
It is formed into a square tube that looks like this.

Thereafter, it is formed into a predetermined square tube with a constant drawing angle of 9, but the degree of processing differs at each section of the square tube. Therefore, the aperture angles are different, with the center of the side being the smallest and the corner being the largest. However, it is necessary to keep this difference in aperture angle to 15 degrees or less. In Figure 1, the aperture angle at the sides is θ5, the aperture angle at the corner is θ1, and the difference in aperture angle is Δθ Δθ−angle θ! −Angle θ2, that is, where D: diameter of main tube (fa) L: length of the side of the square tube (simplified) Determine the length of the die and the diameter of the main pipe so that the length of the die is 1 m). The reason why the difference in the aperture angle is set to 15 degrees or less is because if this value is exceeded, the reduction at the center of the side becomes too sharp, resulting in burn-in and cracking.

On the other hand, the plug is shown in Fig. 1, but the inclination angle ψ1 of the side part is 26 ~
It is necessary to set the angle of inclination ψ2 of the corner to 1° to 5°. If it is less than this, the 70-temperature properties of the plaque will be impaired, and if it exceeds this, it will cause a defective shape.

The shapes of the dies and plugs have been described above, but during actual manufacturing, these dies may be used alone, or these dies and plugs may be used in combination. It is also possible to use a combination of dies or plugs according to the invention and plugs or dies not according to the invention.

The material of these square tubes for these dies and plugs is not only steel.
It can also be effectively applied to other metals such as stainless steel, aluminum, copper, etc.

(Example) Table 1 shows component C: 0.13 to 0.18, St:
0.15-0.35%, Mn; 0.60-0
．． Size 2211IllllXt3. of steel containing 85% and small amounts of P, S, Cr sMo, etc. O
2 shows a comparison between when the die and plug according to the present invention were used and when they were not used when manufacturing a square steel pipe of size 1.

If the die and plug of the present invention are not used, seizure will occur, but if they are used, seizure will not occur.

Table 1 (Effects of the Invention) As detailed above, if the die and plug of the present invention are used when manufacturing a square steel pipe by the diameter reduction method using a round tube as the mother tube, the die and plug can be used even at a relatively high reduction. Square steel pipes can be manufactured without plug seizure.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the die and plug of the present invention, and a method for manufacturing square steel pipes by diameter reduction method using these, Figure 2 (A)
, (a), ri, ni) are respectively A- in Figure 1.
A: Cross section of the round tube, B-B: Cross section when the round tube contacts the die, C-C: Cross section when the round tube becomes a square tube,
DD: A diagram showing a cross section of a square tube. 1; round tube, 2; plug, 3; die, 4; square tube, 5; drawing direction θl; drawing angle of the side in the die, θ2; drawing angle of the corner in the closing chair, ψ1; drawing angle of the side in the plug. Inclination angle, ψ2; inclination angle of the corner in the plug. Fig. 1 4 Square tube 5/drawing direction

Claims (1)

[Claims] In a method of manufacturing a square tube by a diameter reduction method using a die from a round tube or a die and a plug, the shape of the die inlet is larger than a predetermined square tube, and the length of the diagonal is made into a square shape larger than the diameter of the main tube, Furthermore, manufacturing a square tube in which the sides and corners have a constant aperture angle in the aperture direction, and the difference between the maximum and minimum values of the aperture angles θ_1 and θ_2 between the sides and corners is within 15°. It is recommended to use either one or both of the square tube manufacturing die and the square tube manufacturing plug whose sides have an inclination angle of 2° to 10° and the corner inclination angles ψ_1 and ψ_2 of 1° to 5°. Features of the manufacturing method for square tubes.