JPH04202714A - Method for precisely inserting pipe - Google Patents

Abstract

PURPOSE:To obtain a product developing little hardness unevenness and strain, etc., with quenching by setting electrodes at both ends of pipe-shaped long material made of steel material, holding the intermediate part with plural heat and electric insulating materials and rapidly cooling after conducting the electric current and heating the pipe with the electrodes. CONSTITUTION:The electrodes 5 composed of steel material are fitted at both end parts of the pipe-shaped long material 1 made of the steel material and at the intermediate part, plural pieces of fixed jigs 6 formed with ceramics of heat and electric insulating material, are set. Under this condition, the electric current is conducted to the long material 1 from the electrodes 5, and after heating at >= about 850 deg.C, this is rapidly cooled with water to execute the quenching. By this method, the whole long material 1 is uniformly heated and also at the same time, this is rapidly cooled to obtain the product having no quenching unevenness and little strain.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a precision hardening method for a long object such as a pipe.

(Prior Art) In hardening long objects such as pipes, a moving hardening method using high-frequency induction heating is generally used.

In other words, Fig. 4 shows high-frequency induction heating of a long pipe (pipe-shaped part for automobile suspension), where 1 is the pipe to be quenched, 2 is a fixing jig, and 3 is a high-frequency induction heating coil. In this method, the item to be quenched is passed through a coil and moved upward while being heated, and water or the like is sequentially injected from the nozzle 4 onto the heated area to rapidly cool it.

(Problem to be Solved by the Invention) However, in the heating method described above, since the product to be quenched moves, it continues to be divided into a surface-hardened region, a heated region, and a non-heated region, resulting in a state of internal stress distribution. changes, which causes large distortions.

Also, when cooling with water, there are areas where a lot of water hits the product to be quenched, and there are areas where it can be quenched, and areas where there is less water and cannot be quenched, which inevitably results in uneven quenching and hardening, leading to large variations in the roughness. There is a problem.

The technical object of the present invention is to provide a method for quenching a long pipe-like object made of steel, which reduces the occurrence of uneven hardness, distortion, etc. due to quenching.

(Structure of the invention) (Means for solving the problem) The technical means taken to solve the problem are as follows.

In the quenching method for long pipe-shaped objects made of steel,
Precision quenching of a pipe, in which electrodes are arranged at both ends of the product to be quenched, the middle part of the product to be quenched is held with an insulating material made of a plurality of heat insulating materials, and the product is electrically heated by the electrodes and then rapidly cooled. It's a method.

(Function) Even if a long pipe is energized and heated to over 850"C, there will be no distortion of the pipe because it is held by a plurality of ceramic holders between both ends of the pipe. Since the entire part is heated uniformly, by pouring water over the entire part at once, it is quenched uniformly and there is extremely little variation in hardness.

(Example) Examples will be described below.

In Fig. 1, reference numeral 1 denotes a pipe made of a steel material to be hardened, with electrodes 5 made of a steel material fitted to the pipe at both ends, and an electrode 5 made of an insulating material ceramic 6 in the middle. This method involves arranging multiple fixing jigs.

When electricity is applied in this state and the pipe is heated to 850°C or higher, the pipe is held in place by multiple ceramic insulators and expands.
Second, the distortion is extremely small compared to the free case, and the condensate is rapidly cooled and quenched.

In addition, when forming the pipe 1 into a U-shape, the pipe is heated to several hundred degrees, bent into a U-shape, heated to an austenoid region, and then the entire pipe is rapidly cooled and quenched by flowing water like a waterfall.

With this method, the entire pipe can be heated uniformly, and it is also possible to form the pipe between warm and hot temperatures, and since the entire pipe is rapidly cooled at the same time, it is possible to prevent uneven baking (variations in hardness). Become.

In addition, since it is corrected with multiple ceramic fixing jigs (
The occurrence of quenching strain (which cannot expand freely) is almost eliminated.

The hardness of the pipe surface after quenching is shown in Fig. 2. A is the hardness of this example, B is the hardness of the conventional method, and B is 400 to 60.
There is variation in hardness of 0HV.

Figure 3 shows the variation in distortion, and the number of measurements (n) is 5.
0, the average value is 0.20 in this embodiment and 0.8 in the conventional method, which is about four times as large.

As described above, this example has no uneven heating, eliminates the re-hardening process of the conventional method, and eliminates the distortion removal process because the distortion is extremely small.Furthermore, it is possible to perform tempering by weakening the energization. It is possible.

(Effects of the Invention) The present invention has the following effects. In other words, since there is no uneven baking of the product in this example, the durability (lifespan) of the product is increased, the quenching process that is performed twice or three times in the conventional method can be eliminated, and dimensional changes are reduced due to the small distortion. Therefore, the distortion removal process of the conventional method can be abolished, and since the molding and quenching is performed at a high temperature, a small load can be applied, and the process can be shortened because molding and quenching are performed at the same time. .

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of this example, Figure 2 is a diagram showing the position and hardness of the pipe surface, Figure 3 is a diagram showing variations in hardness, and Figure 4 is an explanation of the conventional quenching method. figure. 1... Pipe, 5... Electrode, 6... Heat insulation/insulating material.

Claims (1)

[Claims] In the quenching method for long pipe-shaped objects made of steel,
A precision quenching method for a pipe, in which electrodes are arranged at both ends of a product to be quenched, the middle of the product to be quenched is held with a plurality of heat-insulating materials, the pipe is electrically heated by the electrodes, and then rapidly cooled. .