JPS60223618A - Bending method of metallic material - Google Patents

Abstract

PURPOSE:To make bending thrust smaller than in the conventional particle and to prevent spring back by repeating the heating and cooling cycle consisting of heating a work to the transformation point temp. or above while exerting the bending thrust thereto then cooling the work down to the transformation point temp. or below. CONSTITUTION:The outside periphery of the work W is heated to a ring like by a heating coil 4 and the heating temp. is detected by a temp. sensor 8; at the same time, the thrust is applied thereto by a cylinder 9. The conduction of electricity to the coil 4 is interrupted when the sensor 8 detects that the temp. of the work exceeds the transformation point. The conduction of electricity to the coil 4 is started to reheat the work W when the sensor 8 detects that the temp. of the work W falls down to the transformation point or below. The heating and cooling based on the heat cycle are repeated until the bending of the work W is completed.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for bending metal materials, and more particularly, a method for forming bent portions in various pipes and shapes installed in nuclear power generation facilities, for example. The present invention relates to an improved method for bending metal materials, which is suitable for use when

BACKGROUND OF THE INVENTION Conventionally, a so-called high-frequency heating method has been adopted as a method for forming a bent portion in a pipe material among various pipe materials and shapes made of metal materials.

Roughly speaking, the high-frequency heating method is to heat the outer periphery of a pipe material, which is a workpiece material, in a ring shape using a high-frequency heating coil, and at the same time apply a bending thrust to the workpiece material, and also to bend the tip side of the workpiece material in the bending direction. It means rotating.

In other words, the high-frequency heating method described above is one of the hot tube bending methods that applies bending to the workpiece while locally lowering the deformation resistance of the workpiece using a high-frequency heating coil. The working force is reduced to only about 115" in the case of the cold pipe bending method, and furthermore, since the bending of the pipe causes springback due to processing, a new process is required to remove this springback.

On the other hand, the so-called tension bending method and rolling bending method have been conventionally adopted as methods for forming bent parts in shapes made of metal materials, but none of the above However, there is a problem similar to that of the high-frequency heating method in that springback occurs when bending the book or shape.

[Purpose of the invention]

The present invention was developed as a result of various studies to enable easier bending of metal materials such as the above-mentioned pipes and shapes than before. , the bending thrust applied to the workpiece is smaller than before, and there is no springback in the workpiece.
The present invention aims to provide a method for bending metal materials with excellent workability.

[Summary of the invention]

In order to achieve the above object, the present invention applies a bending thrust to the workpiece at the same time as heating the outer circumference of the workpiece,
In a method for bending a metal material in which the tip side of the workpiece is rotated in the bending direction, the workpiece is heated to a temperature higher than the transformation point temperature of the workpiece itself while applying a constant bending thrust to the workpiece. Then, the workpiece is cooled to a temperature K below the transformation point temperature of the workpiece itself, and the heating/cooling cycle is repeated.

[Embodiments of the invention]

Hereinafter, the present invention will be explained in detail based on an example of the drawings, taking as an example a case in which a pipe material is subjected to a bending process. Figure 2 is a plan view of the main parts of a hot pipe bending device, and is a view taken along the X arrow in Figure 1.
In FIG. 1, reference numeral 1 denotes a guide arm that defines the bending radius of a workpiece W, and the guide arm I is rotated by an arm driving section 2 around its pivot center C. As shown in FIG.

A clamp 3 for gripping a workpiece W is attached to the tip of the guide arm l. Reference numeral 4 denotes a high-frequency heating coil that heats the outer periphery of the workpiece W in a ring shape, as shown in FIG. , the force μ in the circumferential direction of the workpiece W is made uniform. 6 is a coil power supply, 7 is a coil control unit, 8 is a temperature sensor that detects the heating temperature of the workpiece W, the detected value of the temperature sensor 8 is sent to the coil control unit 7, and the coil power supply 6 is a coil control unit. It is controlled by a signal from the control section 7.

In FIG. 1, reference numeral 9 indicates a cylinder that applies a bending thrust to the workpiece W, and reference numeral 10 indicates a guide member that guides the workpiece W pressed by the cylinder 9.

The configuration of a hot tube bending device suitable for carrying out the method of the present invention is as described above.Next, a case where a workpiece W is subjected to a bending process using the tube bending device described above will be described.

First, the workpiece W is set in the state shown by the two-dot chain line in FIG. Further, the guide arm 1 is also set in the state shown by the two-dot chain line in FIG. 1, and the tip of the workpiece W is gripped by the clamp 3. In this state, the outer periphery of the workpiece W is heated in a ring shape by the heating coil 4, and the workpiece W is heated in a ring shape.
At the same time, the cylinder 9 applies a thrust to the workpiece W. In addition, in the present invention, the thrust force applied to the workpiece W is
Cone J point out I? When the thrust does not pass through the transformation region of the workpiece W, a thrust that does not deform the workpiece W is sufficient.

Here, the deformation state of the workpiece W during thermal cycling will be explained based on FIG. 3.

If we take time on the horizontal axis in Figure 3 and temperature and strain on the vertical axis, for example, if the material is 12Cr steel, its Acs transformation will be around 800C, and its Ma1 transformation will be around 3
The temperature is around 00C, but when the temperature is increased with a low acting force of 0.9Kf/m'' applied to the material, a strain (rc) of 1.0 In the process, during Mgl metamorphosis, 0. This results in a strain (rr) of 1×10”.

Therefore, in the method of the present invention, the heating temperature of the workpiece W is gradually raised from room temperature, and the temperature sensor 8 detects that the temperature of the workpiece W has exceeded the transformation point Acs of the workpiece W. If so, it is sufficient to cut off the power to the heating coil 4, and from the event shown in FIG. 3, strain is applied to the workpiece W when the temperature of the workpiece W passes through the transformation point ACI of the workpiece W. The resulting strain is a strain in the bending radius defined by the guide arm l. Next, in the process of cooling the workpiece W, if the temperature center 8 detects that the temperature of the workpiece W has dropped beyond the transformation point Mat of the workpiece W, then the heating coil 4
It is sufficient to start energizing the workpiece W and reheat the workpiece W, and from the event shown in FIG. 3, even when the temperature of the workpiece W passes through the transformation point Ms1 of the workpiece W, the workpiece Since this causes strain in W, this strain becomes a strain in the bending radius defined by the guide arm 1, similar to the strain when the workpiece W exceeds the ACI transformation point.

FIG. 4 shows the thermal cycle of the workpiece W described above, and in the present invention, heating and cooling are performed based on the thermal cycle until the bending of the workpiece W is completed.

Repeat this process.

The present invention is as described above, and the present invention utilizes the transformation superplasticity phenomenon of metal materials for bending the workpiece W, and utilizes the transformation region characteristics of the metal materials, that is, high ductility and low deformation resistance. It is possible to apply bending to the workpiece W with a small processing force, and according to calculations, it is possible to apply bending to the workpiece W with a small bending thrust of about 1/10 compared to the conventional hot pipe bending method. The workpiece W can be bent.

In addition, as described above, the workpiece W that is bent using the transformation superplasticity phenomenon of the gold bullion material has high strength at room temperature, and therefore does not suffer from the problem of springback as in the conventional method.

〔Effect of the invention〕

As described in detail above, according to the present invention, the bending thrust applied to the workpiece can be reduced compared to the conventional method, and the bending force of metal materials can be bent with excellent workability without causing springback in the workpiece. The machining force method can be obtained.

[Brief explanation of drawings]

Fig. 1 is a plan view of the main parts of a hot pipe bending device suitable for carrying out the method of the present invention, Fig. 2 is a view taken in the direction of the X arrow in Fig. 1, and Fig. 3 shows that the pipe bending material is Cr steel. FIG. 4 is a temperature distribution characteristic diagram when the temperature of a pipe bending material is controlled by the method of the present invention. 1... Guide arm, 2... Arm drive section, 3...
- Clamp, 4... High frequency heating coil, 5... Coil drive unit, 6... Coil as source, 7... Coil control unit, 8... Temperature sensor, 9... Cylinder, 1o.
...Guide member, W...Work material. Agent Patent attorney Hiroo Nagasaki (and 1 other person) '41 Mekyo 2 Ro

Claims (1)

[Claims] 1. In a metal material bending method in which the outer periphery of the workpiece is heated, a bending thrust is applied to the workpiece at the same time, and the tip side of the workpiece is turned in the bending direction. While applying a bending thrust of
A method for bending metal materials, characterized by repeatedly performing the heating/cooling cycle described above.