JPH0459969B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a punching pipe manufacturing method. More specifically, the present invention relates to a method for producing a tube by punching, which obtains a thin-walled or long bottomed blank tube after punching. (Prior Art and its Problems) Conventionally, as a method for producing a bottomed base tube, there is a punching method called an ironing method. This is a cold working method that aims to keep the wall thickness constant in a bottomed cylindrical material obtained by deep drawing, thin the wall, improve dimensional accuracy, and make the product surface beautiful. be. There is also a conventional punching method called the push bench method. This is usually done by using the Erhard method, which is one of the hot seamless pipe manufacturing methods, in which a cylindrical material with a bottom is obtained by perforating each steel ingot with a rigid hydraulic press. This is a method of applying Of course, it is also possible to use the push bench method as a cold punching method, and this method is used in some cases. The above two methods will be explained in detail below. Both methods are basically the same method. For example, in the case of the push bench method, first, as shown in Fig. 1, a mandrel 2 is inserted into the bottomed cylindrical material 1 obtained in the previous step, and then the mandrel 2 is inserted as shown in Fig. 2. As shown in FIG. 3, the mandrel 2 is punched out in the direction of the arrow in the figure with a die 4 attached to a fixed frame 3, and then the mandrel 2 is turned into a bottomed blank tube (hereinafter also simply referred to as a "blank tube"), as shown in FIG. 5) is inserted in close contact with 5. Next, as shown in FIGS. 4 and 5, a horseshoe-shaped stripper 6 is placed on the front surface of the fixed frame 3 in the punching direction, and the mandrel 2 is moved back in the direction of the arrow in the figure using a press such as water pressure. Therefore, the blank tube 5 is prevented from retreating by the stripper 6, and the mandrel 2 is separated from the blank tube 5, and the punching operation is completed, or the die 4 is replaced with one with an even smaller inner diameter and the punching operation is performed again. You can start. Furthermore, in the ironing method, instead of the horseshoe-shaped stripper 6, a stripper on a half ring is similarly mounted on the mandrel 2, and the mandrel 2 and the raw pipe 5 are separated by retracting the mandrel 2. However, after punching in the above method,
When a long blank tube is obtained, the area of the close contact between the mandrel 2 and the blank tube 5 is large, and as a result, the retreating force due to pressing such as hydraulic pressure becomes extremely large, resulting in the blank being broken regardless of whether it is hot worked or cold worked. The rear end of the tube 5 may buckle or curl up like peeling a banana, or in the worst case, the mandrel 2 and the blank tube 5 may be separated due to insufficient capacity of the press for retracting the mandrel. There are even situations where it becomes completely impossible. This becomes more noticeable as the tube becomes thinner. Naturally, dealing with this trouble requires a great deal of time and effort, and it goes without saying that it is an extremely serious problem in terms of production. In addition, especially when carrying out the cold punching method, the requirements for the dimensions and properties of the inner and outer surfaces of the raw pipe are often extremely strict, and of course the dimensions and finish properties of the inner surface of the die and the outer surface of the mandrel are Must be strictly managed. In other words, considering the extremely wide processing surface of the mandrel, that is, the surface that processes the material between the die and the die during punching, the costs required for maintenance, management, and production are enormous. We cannot overlook the fact that the desire to shorten the length is a stumbling block to the production of long, thin-walled blank tubes. Furthermore, there is no process for manufacturing ultra-thin seamless steel pipes with an outer diameter/wall thickness ratio of 2 to 3% or less, especially when long sizes are to be manufactured efficiently, and the existing processes Even considering the current situation where ultra-thin walled tubes are manufactured by performing internal and external cutting on the raw tubes obtained in the process, there is an urgent need to be able to manufacture long ultra-thin walled tubes by the punching method. It is said that SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, to facilitate and smooth the separation of the mandrel from the blank tube after punching in punched tube manufacturing, and to eliminate the conventional large cost. The object of the present invention is to provide a method that greatly reduces the problems associated with mandrel maintenance, management, and production. (Means for Solving the Problems) The gist of the present invention is to provide a punching pipe manufacturing method in which a mandrel is inserted into a cylindrical material with a bottom and punching is performed using a die to produce a base pipe with a bottom. In this step, the mandrel has a double structure having an inner layer portion and an outer layer portion of the mandrel whose advancing speed can be independently controlled, and punching is started with the inner layer portion of the mandrel stored in the outer layer portion of the mandrel, and the outer layer portion of the mandrel After the tip of the mandrel passes through at least the die, the mandrel is punched out at a speed of advancement of the outer layer portion smaller than that of the inner layer portion. As described above, according to the present invention, the mandrel is composed of an outer mandrel and an inner mandrel nested therein. The contact area with the mandrel is much smaller than in the past, and in addition, when separating the mandrel and the raw pipe, the inner layer of the mandrel, that is, the inner mandrel, is advanced relative to the outer layer of the mandrel, that is, the outer mandrel. In addition, the two can be easily separated without any buckling or curling occurring at the rear end of the raw pipe. In addition, according to the present invention, the length of the outer mandrel, which requires strict control of dimensions and finishing properties, is significantly shorter than the length of conventional mandrels, especially when cold punching is performed. This makes it possible to significantly reduce the large amount of costs required for mandrel maintenance, management, and production. The method according to the present invention can be employed not only during cold working but also during hot working. This is because the problem solved by the present invention is basically the same phenomenon regardless of whether it is hot or cold. (Function) Hereinafter, the present invention will be explained in more detail based on the drawings. FIGS. 6 to 10 are schematic cross-sectional views sequentially illustrating the punching tube manufacturing method in a preferred embodiment of the present invention. First, as shown in FIG. 6, the mandrel 2 is inserted into the bottomed cylindrical material 1. The mandrel 2 is composed of an outer mandrel 7 and an inner mandrel 8, and the inner mandrel 8 is nested inside the outer mandrel 7, and the two are integrated. Considering the subsequent process, it is desirable that the front end surfaces of both in the punching direction are substantially the same. Next, at the beginning of the punching tube manufacturing process, as shown in FIG. 7, the forward speed V _i of the inner mandrel 8 is made to match the forward speed V _p of the outer mandrel 7,
It is desirable to begin punching in exactly the same way as a normal bush bench or ironing process. This is the forward speed of the inner mandrel 8 at this point.
This is because if V _i is made larger than the forward speed V _p of the outer mandrel 7, the required thickness reduction process will not be performed at the tip of the punched blank tube, and the predetermined wall thickness and outer diameter will not be obtained. Outer mandrel 7 and inner mandrel 8
Each of the rear end portions is connected to an appropriate drive mechanism (not shown) such as a hydraulic device, and is moved independently. After starting punching in this way and advancing the inner mandrel 8 and outer mandrel 7 by a certain amount in an integrated state, for example, after the tip of the outer mandrel passes at least the die, the 8th
The forward speed of the inner mandrel 8 as shown in the figure
Make V _i larger than the forward speed V _p of the outer mandrel. In this case, a method may be adopted in which only the forward speed V _i of the inner mandrel 8 is increased compared to the initial speed of punching when the inner mandrel 8 and outer mandrel 7 are integrated to perform punching, or 7 forward speed V _p
It may be a method of reducing only the amount of the difference, or a method of changing both. In short, it is sufficient that a speed difference arises between the two as a result. The reason why the inner speed is set to be higher than the outer speed is that the inner needs to be in a state in which it precedes (projects) the outer as shown in FIG. 9 at the end of machining. However, as shown in FIG. 9, the forward speeds V _i and V _p must be determined so that at the end of punching, a part of the outer mandrel 7 is located behind the minimum inner diameter portion of the die 4 in the punching direction. It won't happen. Otherwise, the rear end of the bottomed cylindrical material 1 would remain unprocessed. Now, at the end of punching shown in Figure 9,
Since the outer mandrel 7 is in contact with only a part of the entire length of the bottomed pipe 5, the speed of both is controlled so that the inner mandrel 8 can be moved forward relative to the outer mandrel 7, as shown in FIG. Control. Even if both move forward or backward, they can be separated as long as V _i >V _p is satisfied. As described above, according to the present invention, it is possible to separate the outer mandrel 7 and the bottomed cylindrical tube 5 much more easily than in the conventional method,
Moreover, since tension is applied over the entire length at this time, it is clear that buckling or blistering does not occur at the rear end of the bottomed blank tube 5. Furthermore, a tool for determining the inner surface properties and dimensions of the bottomed blank pipe 5 in the punching pipe manufacturing method according to the present invention;
In other words, the outer mandrel 7 can be made much shorter than the mandrel used in the conventional method, which reduces the costs required for mandrel maintenance, management, and production, which are particularly problematic in cold punching pipe manufacturing. There is something unimaginable about this. According to experiments conducted by the present inventor, the total length/outer diameter ratio is such that it is possible to punch out a bottomed cylindrical blank tube with a wall thickness/outer diameter ratio of 1% without causing shape defects at the rear end. It was confirmed that in the present invention, it was possible to punch out even if the number exceeded 10 without any problem, whereas in the method, the number was 4 to 5 at most. Next, the present invention will be explained in more detail with reference to Examples. Example In this example, the material is
Using S15C material with a diameter of 62 mm and a wall thickness of 1 mm,
Cold punching was carried out. Table 1 summarizes the die diameters and mandrel dimensions for the inventive example and the conventional example. The result of the punching pipe production performed in this way is the second
This is shown in the table along with that of the conventional example.

【table】

[Table] (Note) *: In conventional example No. 2, when the mandrel and the product are separated after punching, the rear end surface of the product
The material curled up, making it impossible to make pipes.
As can be seen from the results shown in Table 2, according to the conventional method, the total length/outer diameter ratio is at most 4.3, whereas
According to the present invention, the ratio is 11.4, making it possible to manufacture long tubes. Moreover, since the outer mandrel is 200 mm long, compared to the conventional mandrel length of 700 mm, the contact area with the inner surface of the raw pipe is less than 1/3, which makes maintenance easier. It is possible to significantly reduce production costs.

[Brief explanation of the drawing]

Figures 1 to 4 are schematic sectional views showing the working steps of the conventional punching pipe manufacturing method;
The figure is a sectional view taken along the line A-A in FIG. 4; and FIGS. 6 to 10 are schematic sectional views showing the working steps of the punching pipe manufacturing method according to the present invention. 1...Cylindrical tube with bottom, 3...Fixed frame,
4...Dice, 7...Outer mandrel, 8...
…Inner mandrel.

Claims (1)

[Claims] 1 In a punching tube manufacturing method in which a mandrel is inserted into a bottomed cylindrical material and punched out using a die to produce a bottomed tube, the mandrel has an inner layer portion and an outer layer portion that can independently control the advancing speed of the mandrel. Punching is started with the inner layer of the mandrel stored in the outer layer of the mandrel, and after the tip of the outer layer of the mandrel has passed at least the die, the advancing speed of the outer layer of the mandrel is adjusted to A punching pipe manufacturing method characterized by punching at a speed lower than that of the inner layer.