JPS6355383B2 - - Google Patents

Abstract

PURPOSE:To reduce a pipe in diameter while forming a sufficiently thick shoulder part without buckling by performing diameter reduction by rotary casting after increasing the thickness of a pipe end part axially toward an internal diameter side, and then performing axial upsetting work. CONSTITUTION:A tubular material 4 heated up to about 1,250-1,150 deg.C is held by a half die 51 and intruded into a punch 61 from a pipe end, and axial upsetting work is carried out by a half die 52 and a punch 62 to form a thick part 7 on an internal diameter side at a specific distance l' from the pipe end. The blank material 4 is cast by using a tap 11 while rotated to reduce the material from the pipe end to the thick part 7 within a specific range to a specific external diameter. Then, axial upsetting work is performed by a half die 54 and punch 63 and the material 4 of the diameter-reduced parallel part elongated by said rotary casting is moved axially and an underfill part 8 is supplemented to make the shoulder part of the diameter-increased part sufficiently thick; and the reduced part is increased in diameter slightly toward the internal-diameter part slightly.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for drawing a pipe that provides a sufficient wall thickness to the shoulder portion and does not cause buckling in the parallel portion of the pipe.

The pipe neck drawing process is used to manufacture high-pressure cylinders as shown in FIG. 1a, hollow axles as shown in FIG. 1b, and the like. Conventionally, rotary forging, spinning, upset processing, etc. have been known as this neck drawing process, but in high-pressure cylinders and hollow axles, stress is concentrated on the shoulder 3 that connects the parallel neck part 1 and the non-drawn part 2. For this reason, the mouth drawing process is performed by upset processing which allows the thickness of this portion 3 to be increased. FIGS. 2a to 2e show a conventional mouth drawing method for manufacturing hollow axles.

FIGS. 2a to 2c show the axial upsetting process for increasing the thickness of the shoulder portion, in which 4 represents the material, 5 ₁ and 5 ₂ represent half dies, and 6 ₁ and 6 ₂ represent punches. By performing three axial upsetting operations using a combination of half dies 5 ₁ , 5 ₂ and punches 6 ₁ , 6 ₂ , a portion 7 at a specific distance from the tube end, which will become the shoulder portion, bulges toward the inner diameter side. It can be seen that some parts are thicker than others. Material 4 after axial upsetting
Next, as shown in FIGS. 2d and 2e, it is grasped by a half die ₅₃ , and subjected to twice-drawing upset processing by drawing dies _5'1 and _5'2 .

However, in this neck drawing upset process, as the outer diameter is narrowed, the thickness of the drawn part increases toward the inner diameter side, as shown in Fig. 2 d and e, but as shown in Fig. 2 a -
The thickened part 7 obtained by the axial upset machining shown in c does not increase in thickness much because the amount of outside diameter reduction is small, and after machining, the second
A lack of thickness 8 as shown in Figure e occurs. Needless to say, when the lack of thickness 8 occurs, the mechanical strength of the product shoulder portion 3 decreases, and the product value decreases. In order to prevent this, the number of axial upset machining steps shown in Fig. 2 a to c is increased.
If this is done, the number of man-hours and heating cost will naturally increase, and the yield will decrease and the number of man-hours will increase due to the cutting and removal of the surplus portion 10 generated in the unnecessary portion as shown by the dotted line in Fig. 2c, resulting in an economical problem. cause deterioration.

In addition, in this neck drawing upset processing, the upsetting distance l of the drawing die 5' ₂ is long as shown in FIG. As shown in e, there is a risk that buckling 9 will occur at the base of the parallel opening portion 1. This buckling 9 is more likely to occur as the parallel part 1 is longer, so its length is limited, and depending on the specifications, it may not be possible to manufacture hollow axles that require the parallel part 1 to be longer. Sometimes.

The present invention aims to provide a pipe neck drawing method that can solve all of the above-mentioned problems, and is characterized by increasing the wall thickness inward by axial upsetting at a specific distance from the pipe end. process and
The present invention is characterized in that it comprises the steps of drawing the mouth by rotary forging in the range from the tube end to the thickened portion, and performing an axial upsetting process on the parallel portion of the mouth drawing.

In other words, the method of the present invention increases the thickness of a portion at a specific distance from the tube end toward the inner diameter by axial upsetting, and then uses rotary forging without the risk of buckling to extend the area from the tube end to the thickened portion. The purpose is to compensate for the thickened portion 7, where the effect of increasing the thickness during the mouth drawing is small, by performing an axial upsetting process after the mouth drawing.

To explain this in a little more detail, in order to give the shoulder part of the product sufficient wall thickness, it is unavoidable to increase the thickness of the intended shoulder part toward the inner diameter before the mouth drawing. Directional upsetting is optimal. However, if this processing is attempted to include the opening, buckling will occur as described above. Therefore, it is considered best to focus on preventing buckling in this mouth drawing process, and supplement the insufficient material for the thickened portion separately in post-processing. In other words, if the opening after axial upsetting is performed using a process that does not pose the risk of buckling, and if the lack of increased thickness is made up for later with another process, sufficient wall thickness can be achieved at the shoulder area. Of course, the pipe is drawn in the most rational manner, with no buckling occurring at the base of the parallel part of the pipe, and there is no need to unnecessarily increase the number of man-hours. . Based on this idea, the method of the present invention applies axial upsetting to add thickened parts, rotary forging to draw the mouth without risk of buckling, and axial upsetting to replenish material shortages in the thickened parts. It is something to do.

Hereinafter, the method of the present invention will be explained in more detail using the hollow axle shown in FIG. 2 as an example.

FIGS. 4a-c illustrate an axial upsetting process for applying thickening, which is the same as that used in the conventional method shown in FIG.

That is, first, the tubular material 4 is gripped by the half die 5 ₁ , the punch 6 ₁ is inserted from the tube end, and the material 4 is punched through the stepped portion 6 ″ ₁ while the punch tip 6 ′ ₁ prevents the material from buckling. Press it in the axial direction to increase the outer diameter and thickness of the material end (Fig. 4a).Then, change the half die to ₅₂ and perform upsetting in the axial direction again with the same punch ₆₁ ( Figure 4b).

As mentioned above, these two processes are intended to expand the outer diameter and increase the thickness of the end of the material, and are pre-processing specific to hollow axles, and may be omitted in cylinder manufacturing, etc., or may be performed separately. Pre-processing is performed.

After the two pre-machining steps are completed, the punch is changed to ₆₂ and axial upset machining is performed once again (Fig. 4c). The tip of the punch 6 ₂ is tapered, and the material 4 is locally thickened toward the inner diameter near the tip of the punch 6 ₂ by pushing the punch 6 2 . The material upsetting rate in this process is 10 to 30%, because if it is less than 10%, the specified inner diameter of the intended shoulder part cannot be sufficiently obtained, and if it is more than 30%, there will be too much surplus part 10 as shown in Fig. 2 c. It is desirable to be within the range of .

Thickened part 7 shown by crosshatching in Fig. 4c
It is necessary to determine the distance l' from the tube end so that it is located approximately at the shoulder 3 after the axial upsetting process shown in FIG. 4e. In addition, its volume is determined by the product shoulder 3 shown in crosshatching in Figure 4e for the following reason.
It is recommended that the volume be approximately 80 to 90% of the volume. That is,
The missing thickness 8 in the thickened part 7 is compensated for by the final axial upsetting process, but the replenishment rate in this final axial upsetting process should be kept to about 20% due to the upsetting rate limitation as described later. Because it's good.

The part on the pipe end side of the thickened part 7 will be increased by approximately 33% in the next mouth drawing process, and will also increase slightly in the final axial upsetting process, so the target wall thickness for this part will be It is necessary to design by subtracting these thickened parts from.

After the thickened portion 7 is provided, the area from the tube end to the thickened portion 7 is narrowed down to a predetermined outer diameter by rotary forging, as shown in FIG. 4d. If the outer diameter reduction rate per blow in this process is 40% or more, overfilling tends to occur, and if it is less than 20%, the inner diameter increase is too small, so a range of 20 to 40% is desirable.

Rotary forging itself is already well known, and for example, as shown in FIG. 5, the material 4 is shrunk by moving in the axial direction while rotating inside a tap 11 consisting of a hammer divided into four parts in the circumferential direction. It is the diameter. Needless to say, it is necessary to smoothly expand the diameter of the portion from the narrowed part to the non-drawn part.

In this rotary forging, the degree of increase in thickness at the drawn part is smaller than in upset processing, and, like upset processing, the drawn part extends toward the pipe end during processing, and the thickened part increases with the metal flow. 7 has the disadvantage that it is difficult to increase the thickness, but unlike upset processing, there is no risk of buckling due to free axial compression on the outer circumference, and considering that the above-mentioned disadvantages can be compensated for by the next axial upset processing, this advantage is. becomes extremely valuable.

When the mouth drawing process by rotary forging is completed, the material 4 is finally clamped by the half die ₅₄ , and in this state, the material 4 is pressed axially from the tube end side with the punch ₆₃ to form the mouth drawing part. Axial upsetting is performed on the parallel portion of the shaft without changing the outer shape of the shaft. The material upsetting rate in this process is 0 to 15%, because if it exceeds 15%, flaws will occur at the mouth drawing part due to buckling.
Desirably within the range of 15%.

By this axial upsetting process, the material of the parallel portion of the opening is moved in the axial direction, replenishing the missing thickness 8 of the thickened portion 7, and providing sufficient wall thickness to the shoulder portion 3. The thickness increases slightly toward the inner diameter side over the entire area.

Note that each of the above-mentioned processing is performed hot, and the temperature is suitably within the range of 1250 to 1150°C.

Next, an example will be described.

A hollow axle was manufactured by subjecting the end of a raw pipe made of steel equivalent to S45C with an outer diameter of 185 mm and an inner diameter of 140 mm to the drawing process shown in FIGS. 4a to 4d. The shape of the end of the product before cutting and finishing is shown below based on the dimensions shown in FIG.

l ₁ = 570mm l ₂ = 335mm l ₃ = 50mm l ₄ = 85mm l ₅ = 80mm l ₆ = 20mm α ₁ = 185mm α ₂ = 140mm α ₃ = 202mm α ₄ = 130mm α ₅ = 50mm T = 65mm Manufactured Maximum wall thickness t of the shoulder of the hollow axle
As mentioned above, the diameter reached 65 mm, and no buckling occurred at the base of the parallel part of the opening.

Also, for reference, when we tried to manufacture hollow axles of the same size from the same raw pipe by the conventional method shown in Fig. 2 a to e, the maximum wall thickness t of the neck shoulder part was
In order to obtain the maximum wall thickness t of 65 mm, the axial upsetting process shown in FIGS. 2a-c had to be increased from three to four times. Also,
The parallel part of the product opening has a length l ₂ relative to the outer diameter α ₄
Since the ratio of 2.6 was large, cracks due to buckling occurred at the base of the parallel portion, regardless of the number of axial upset machining operations. Incidentally, according to experiments conducted by the present inventors, this buckling limit in the conventional method is l ₂ /α ₄ =2.0 to 2.5.

As is clear from the above explanation, the present invention provides a sufficient wall thickness to the shoulder portion of the neck without increasing the number of processing operations, so that it is possible to economically produce a neck-drawn product with high product value. Since buckling of the base of the parallel portion is prevented, restrictions on the length of the parallel portion are removed, making it possible to manufacture hollow axles and the like with dimensions that could not be manufactured using conventional methods.

[Brief explanation of drawings]

Figures 1a and b are explanatory diagrams of the mouth drawing processed product, Figures 2 a to e are process illustrations of the conventional method, Figure 3 is an explanatory diagram of the mouth drawing upset processing process of the same method, and Figure 4 a.
-e are process explanatory diagrams of specific examples of the method of the present invention, No. 5
The figure is an explanatory diagram of the rotary forging process of the same method, and FIG. 6 is an explanatory diagram of the shape of a hollow axle manufactured in an example of the present invention. In the figure, 1: Aperture parallel part, 2: Non-aperture part, 3:
Shoulder, 4: Material, 5 ₁ ~ 5 ₄ : Half die, 6 ₁ ~ 6
₃ : Punch, 7: Thickened area, 8: Thickness, 9: Frustration,
10: Surplus, 11: Tap.

Claims (1)

[Claims] 1. A step of increasing the thickness of a portion at a specific distance from the tube end toward the inner diameter side by axial upsetting, a step of reducing the diameter of the area from the tube end to the increased thickness portion by rotary forging, and 1. A method for drawing a pipe, comprising the step of performing an axial upsetting process on a parallel portion.