JPS5978717A - Production of stepped bar or pipe - Google Patents

Abstract

PURPOSE:To produce easily a stepped bar by heating the mid-part of a bar of a metal to a temp. at which the resistance to plastic deformation decreases and pulling axially the bar. CONSTITUTION:Both ends of a metallic bar 1A are clamped with pulling chucks 9, 9, and electric current is conducted to the bar through said chucks or the current conducting chucks clamping separately the bar on the inner sides of both ends thereby heating the bar. The intermediate part 11A is heated and the chucked parts 12A are cooled to prevent heating up and therefore if the bar is axially pulled by the chucks 9, 9, the part 11A is formed into a smaller diameter and the parts 12A on both sides thereof remain at a large diameter. A stepped bar is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to rods or tubes made of steel or other metal materials that are stepped, that is, a relatively large diameter portion and a small diameter portion are continuous, particularly those that have a large diameter at both ends. The present invention relates to a method of manufacturing a product having a small diameter in between. With the present invention, stepped rods or tubes can be manufactured efficiently with high material yields.

In recent years, there has been an increasingly strong demand for reducing the weight and manufacturing cost of machinery such as automobiles. For example, the shafts of automobile transmissions are stepped rods,5 which have traditionally been manufactured by cutting, which takes a long time to manufacture and results in considerable material loss. It was wanted.

Furthermore, can hollow products be manufactured using conventional technology? There are various difficulties in doing so. That is, welded steel pipes have high productivity and low cost, but cannot be used as important safety parts because defects occur in the welded parts. Also, it is difficult to make something with a small diameter and a thick wall. On the other hand, seamless steel pipes have excellent reliability and can be used for parts that are subject to high stress, but small diameter pipes require a long manufacturing process by reducing the diameter from hot extruded rough pipes, resulting in high costs. This is an obstacle.

An object of the present invention is to solve these problems and provide a method for manufacturing stepped rods or tubes, especially those with large diameters at both ends and a small diameter in the middle, with a high material yield through simple processes. There is a particular thing.

The method for producing stepped rods or tubes of the present invention involves heating a certain midway portion of a metal rod or tube to a high temperature that reduces plastic deformation resistance, and then cooling both sides of the metal rod or tube to a lower temperature that increases deformation resistance. By stopping and pulling in the axial direction, the portion with low deformation resistance is stretched to reduce the diameter, thereby forming a step between the portion with high deformation resistance and the diameter not being reduced.

The applicant has previously developed a method for manufacturing a tapered rod whose diameter changes continuously by applying a temperature gradient in the axial direction of a metal material and pulling it, as well as an apparatus for the same, and has already proposed this method in Japanese Patent Application Laid-Open No. No. 56-131035, No. 57-11
No. 722, No. 57-22819). The previous technology is
In contrast to forming a temperature gradient, that is, a temperature distribution that changes continuously, in the present invention, only the middle part where the diameter is desired to be reduced is heated to a temperature where the plastic deformation resistance is small, and the parts on both sides have a large deformation resistance. Stop at a low temperature and press A3,
It is novel in that it forms stages by providing a discontinuous temperature distribution.

One method of heating a certain part of a metal rod or tube to a high temperature that reduces resistance to plastic deformation is to first heat substantially the entire metal rod or tube. Afterwards, only the other parts, that is, the parts whose diameter is not intended to be reduced, are cooled to a low temperature where the deformation resistance is large. Another method is to heat the portions that are not desired to be heated while cooling the temperature and suppressing the increase in temperature. Although any of these methods may be used or they may be used in combination, the latter method is advantageous.

The means of heating is arbitrary, and the simplest option is to use a gas flame or an electric furnace, but in order to noticeably enjoy the high productivity that is one of the effects of the present invention, it is desirable to heat quickly. . From this point of view, it is preferable to directly energize the material using Joule heat or to heat it by high-frequency induction.

The means for cooling is also arbitrary, and blowing cold air or spraying water can be easily implemented. In order to form the steps abruptly, it will be readily appreciated that the temperature change between the heated and unheated sections must be abrupt.

If that is desired, use the latter of the two methods described above, i.e. cold Nl t.

It is best to use a method of heating the food while heating it. For cooling, contact with a cooling device is effective. The simplest way is to have the cooling tool also serve as a dilator for tension processing. In other words, from the heating stage, both sides of the part of the metal rod or tube whose diameter is to be reduced are gripped with chucks, and once the middle part is heated, it is pulled out. Grasping with a tension chuck may be done from the beginning of heating, or may be done from the middle. If direct current is applied to the metal material as the heating means, the tension chuck can also serve as the current-carrying chuck.

If a large amount of heat is to be removed from the metal material by contact with the cooling device, it is preferable to use a cooling device made of a material with high thermal conductivity, such as copper.

This can also simply serve the purpose of cooling by being in close contact with the tension chuck and transferring heat thereto.
If necessary, the cooling device and/or the tension chuck can be provided with fins for heat dissipation, and if necessary, means such as passing cooling water through the inside of the cooling device can be provided.

To explain an example with reference to the drawings, first, as shown in FIG. 1A, both ends of a metal rod 1A are held in a tension chuck 9.
9 and heat the rod by passing an electric current through it or separately by means of an electric chuck gripping the rod inside these. The intermediate portion 11A is heated, while the portion 12A gripped by the chuck is cooled and the temperature does not rise, so that the temperature distribution of the material is conceptually shown in FIG. 1B.

Then, by pulling it in the axial direction with a tension chuck, a stepped rod 1B is obtained, as shown in FIG. 2, in which the middle portion 11B has a small diameter and the portions 12B on both sides thereof have a large diameter.

The method of the present invention can also be applied to pipes as described above, and can be carried out more advantageously on pipes.

This is because tubes are hollow and convenient for heating and cooling, and it is easier to create the desired temperature distribution in the material than with solid rods.

Another embodiment in which the present invention is applied to the manufacture of stepped pipes is shown in the drawings. As shown in FIG. The cooling device 7.7 is used as an energizing terminal, and the intermediate portion 21A of the material tube is heated by direct energization.
Since the temperature does not rise in the contact area 22A of the tension chuck 9.9 and the cooling device 7.7, the temperature distribution of the material is again as shown in FIG. 1B. As a result of the stretching, a stepped tube 2B is obtained, as shown in FIG. 4, with a large diameter section 22B on either side of a small diameter section 21B.

According to the present invention, stepped rods or tubes with various diameter combinations can be easily produced without the need for special rolls or forging tools. The material yield is much higher than by machining.

Since stepped tubes are difficult to manufacture by other methods, the ease of heating and cooling the tubes, combined with the high productivity, allows the method of the present invention to It can be said that its significance is particularly great.

-1L"1 Outer diameter 25. Qmm, inner diameter 17.0nun (thus wall thickness 4
．． A cold-finished seamless steel pipe of JIS 5TPG38 of 0111111) with a length of 1200III11 was used as a material, and the length from both ends to the 100III1 part was grasped with a tension grip, and the temperature was raised to 780 ° C. in 15 seconds by direct energization.

Perform tensile processing of 4801III11 in the axial direction,
A stepped tube as shown in FIG. 4 was manufactured. There is a part with no change in diameter of 110vn at each end, and between them there is a stepped pipe with a smaller diameter, and the outer diameter of the smaller diameter part is 1.
9.2mm, inner diameter is 12.0+++m (therefore, wall thickness is 3
．． 6+I1m). Despite the drastic change in the thickness of the step part, the wall thickness was sufficient to maintain the width of 4t.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating the process of manufacturing a stepped bar according to the method of the present invention, and shows the stage in which the raw bar is held and pressed with a tension chuck and heated by direct energization; B shows the temperature distribution of the material after heating. Fig. 2 is a partially cross-sectional side view showing the shape of the stepped bar manufactured by the process shown in Fig. 1. 1A is a diagram similar to FIG. 1A illustrating a step of manufacturing a stepped tube according to another embodiment of the method of the invention. FIG. 4 shows the shape of a stepped tube manufactured by the step of FIG. It is a side view of a partial cross section. IA (2A)... Material rod (tube) 11△ (21
△)...High temperature part 12△(22Δ)...
・・Low temperature part IB (2B＞・・・・・・Stepped rod (
pipe) 11B (21B>...Small diameter part 12B
(22B) Large diameter portion 7 Cooling device 9 Tension chuck Patent applicant Daido Steel Co., Ltd. Representative Patent attorney Souo Suga Figure 1 A 'Ir11 Figure B O8 Figure 4 @

Claims (1)

[Claims] (1) A metal rod or tube is heated at a certain midpoint to a high temperature where plastic deformation resistance is small, and both sides are cooled and kept at a low temperature where deformation resistance is large. A method for manufacturing a stepped rod or tube, characterized by forming a step between the part with high deformation resistance and the part whose diameter cannot be reduced by stretching the part with low deformation resistance and reducing the diameter. ( 2) A manufacturing method according to claim 1, in which the heating means is flame, direct current, or high frequency induction. (3) A patent in which the cooling means is contact with a tension chuck having good thermal conductivity. The manufacturing method according to claim 1. (4) The manufacturing method according to claim 1, wherein the cooling means is a cooling device with good thermal conductivity provided in close proximity to the tension chuck.