JPH01218715A - Method for hot extruding pipe - Google Patents

Abstract

PURPOSE:To perform control corresponding to the change even when the condition is changed by using a preset material according to conditions to the billet stock and conditions such as its extrusion ratio, as the extrusion speed pattern used for control. CONSTITUTION:Signals regarding comparison results of extrusion speed measured signals from a comparator 4 with extrusion speed set signals are compared and decided by the comparator circuit 61 is a regulator 6. When a deviation of the measured value of the extrusion speed from the set value thereof is large, a change-over valve 64 on the side of a proportional circuit 62 of both change-over valves 64, 65 is operated to perform the valve opening adjustment by a hydraulic servo 2 in the proportional circuit 62. When the deviation is small, the change-over valve 65 on the side of a proportional-plus-integral circuit 63 of both change-over valves 64, 65 is operated to perform the valve opening adjustment by the hydraulic servo 2 in the proportional-plus-integral circuit 63. Hereby, when the deviation is large, but extrusion speed can correspond quickly to its set value, but, when the deviation is small, the speed can be stabilized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention involves inserting a heated billet into a container,
The present invention relates to a hot extrusion pipe manufacturing method for manufacturing a pipe by upsetting the billet and extruding it forward.

[Prior art]

In such a hot extrusion pipe manufacturing method, it is important to control the extrusion speed to properly perform billet upset processing and subsequent extrusion processing in order to improve pipe production efficiency, pipe production quality, etc.

By the way, as a method of actually controlling the extrusion speed in the hot extrusion pipe manufacturing method, for example, the extrusion speed is patterned to consist of at least one steady region and a gradually increasing region and/or gradually decreasing region before or after it. has been disclosed (Japanese Patent Application Laid-Open No. 5.8-1684).
No. 22).

[Problem to be solved by the invention]

However, in the above-mentioned control method, the pattern control of the extrusion speed is performed according to the elapsed time, so even if variations in billet size or temperature occur during the pipe-making process, corresponding control is not performed, and this is especially true in the pipe-making process. In the initial stage, there was a problem in that the forge amount varied and uneven thickness was likely to occur, and the extrusion speed at the end of the tube manufacturing process was not appropriate, resulting in frequent occurrence of shear knots on the inner surface of the bottom part of the billet. Furthermore, in the middle stage of the pipe making process, only a steady extrusion rate can be obtained;
Even if the billet to be pipe-made is a long billet in which a temperature distribution occurs in the length direction, there is a problem in that extrusion speed control cannot be performed in consideration of the temperature distribution during pipe-manufacturing.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a hot extrusion pipe manufacturing method that can solve the above-mentioned problems.

[Means to solve the problem]

A hot extrusion pipe manufacturing method according to the present invention is a hot extrusion pipe manufacturing method in which a heated billet is inserted into a container, the billet is upset, and a pipe is manufactured by extruding the billet forward. Various extrusion speed patterns are set in advance according to material conditions and their extrusion ratios,
The present invention is characterized in that the extrusion speed is pattern-controlled in accordance with the ram movement distance based on the pattern.

[Effect]

In the method of the present invention, the extrusion speed pattern used for control is preset according to conditions such as billet material conditions and its extrusion ratio, so even if the conditions change, It is also possible to perform control that can respond to these changes. Moreover, since pattern control of the extrusion speed using the pattern is performed based on the ram movement distance, the properties of the billet in the process of actually processing the billet are reliably reflected in the control.

〔Example〕

The present invention will be described below based on drawings showing embodiments thereof.

FIG. 1 is a block diagram showing an apparatus used to carry out the method of the present invention. 1 in the figure shows a hydraulic extrusion press in which the extrusion speed is controlled based on valve opening adjustment by a hydraulic servo 2. The extrusion speed of the extrusion press 1 is actually measured by a speed meter 3; A signal regarding the value (hereinafter referred to as an extrusion speed actual measurement signal) is input to a comparator 4.

In addition, the extrusion speed is input to the comparator 4 from the speed pattern setting device 5, including billet material conditions (outer diameter, wall thickness, length, temperature, etc.)
A signal related to a set value (hereinafter referred to as an extrusion speed setting signal) patterned as shown in FIG. 2, for example, according to the extrusion ratio is also input.

The extrusion speed pattern shown in FIG. 2 is determined based on the following setting criteria. That is, in the upset stage (2), it is known that the higher the extrusion speed, the greater the variation in the outer diameter of the extrusion start side tube end, so the low speed (2) is set, and the ram movement distance is determined by the billet length, material, etc. It is calculated and determined according to the length of the container and the range of ram movement. In addition, in the stable extrusion stage (■), if the extrusion speed is high, the diameter expansion from the center of the tube to the end of the tube immediately before completion of extrusion will be small; Considering this relationship, the extrusion speed is determined to be a constant value (2) based on the relationship between die wear and longitudinal dimension variation after extrusion. In addition, in the stage (2) before the completion of extrusion, a difference in strain rate occurs between the metal in the part extending from the center of the billet to the outside and the metal on the inner side, which tends to cause shearing flaws. The comparator 4 then compares the two input signals as described above and sends a signal related to the comparison result to the regulator 6.
It is designed to be input to. Note that a signal regarding the ram movement distance of the extrusion press 1 actually measured by the ram movement distance meter 8 is input to the speed pattern setting device 5. The extrusion speed setting signal from the speed pattern setting device 5 is an actual value of the extrusion temperature actually measured by a thermometer (not shown) installed on the container entrance side of the extrusion press 1 (or a predetermined value based on the actual value). is input to the calculator 7 together with a signal related to the value obtained by subtracting the constant value. Then, the calculator 7 calculates the optimum value of the customer gain of each control circuit in the regulator ε based on the above-mentioned input signal, and inputs a signal related to the calculation result to the regulator 6.

Thus, the regulator 6, which receives the signal related to the comparison result between the extrusion speed actual measurement signal and the extrusion speed setting signal from the comparator 4, and the signal related to the gain optimum value calculation result from the calculator 7, uses the re-input signal. The hydraulic servo 2 is controlled to adjust a predetermined valve opening degree.

To explain the regulator 6 in more detail, the regulator 6
is equipped with a comparator circuit 61, a proportional circuit 62, and a proportional/integral circuit 63 to which signals related to the comparison results are respectively input. and the proportional circuit 62 and the hydraulic servo 2
A first switching valve 64 is connected between the
A second switching valve 65 is provided between the hydraulic servo 2 and the hydraulic servo 2, and the switching operation of both switching valves 64 and 65 is performed based on the output of the comparator circuit 61. Note that the proportional/integral circuit 63 includes the calculator 7.
A signal related to the gain optimum value calculation result from is input,
Based on this signal, each controller 63a, 63b, 63c of the loop gain, proportional circuit gain, and integral circuit gain provided in the proportional/integral circuit 63 is adjusted.

Then, the comparator circuit 61 in the regulator 6 compares and determines the signal related to the comparison result between the extrusion speed actual measurement signal and the extrusion speed setting signal from the comparator 4, and determines the deviation between the actual extrusion speed measurement value and the set value. When large, double switching valve 64.65
The switching valve 64 on the proportional circuit 62 side is operated so that the valve opening adjustment by the hydraulic servo 2 is performed by the proportional circuit 62, and when the deviation is small, both switching valves 64 and 65 are operated.
The switching valve 65 on the proportional/integral circuit 63 side is operated to cause the proportional/integral circuit 63 to adjust the valve opening degree by the hydraulic servo 2. When such control is performed, when the deviation is large, the extrusion speed can be quickly adjusted to the set value, while when the deviation is small, the extrusion speed can be stabilized.

Furthermore, each gain controller 63a, 63b, 63c in the proportional/integral circuit 63 is adjusted based on the signal regarding the gain optimum value calculation result from the calculator 7,
The amount of control of the hydraulic servo 2 by the regulator 6 is optimized depending on the extrusion temperature and extrusion speed. When such control is performed, it is possible to cope with changes in the response of the control system depending on the extrusion conditions.

When carrying out the method of the present invention using such an apparatus, the extrusion speed pattern used for control is set in advance according to billet dimensions, material conditions such as temperature, and conditions such as extrusion ratio, for example. Since a pattern as shown in FIG. 2 is used, control corresponding to changes in the conditions becomes possible. Moreover, since the pattern control of the extrusion speed using the pattern is performed based on the actual value of the ram movement distance measured by the ram movement distance meter 8, the initial characteristics of the actual extrusion process are reliably reflected in the control.

Next, specific effects when implementing the method of the present invention will be explained.

Table 1 shows the thickness unevenness rate (thickness unevenness rate at a position 200 mm away from the extrusion start side tube end), overall length outer diameter variation, and shearing flaw (shearing flaw caused due to internal surface burning) occurrence rate. This is a list of the results obtained when extrusion pipes were produced using the conventional method and the results obtained when extrusion pipes were produced using the method of the present invention.

Table 1 From the results, it can be seen that by carrying out the method of the present invention, it is possible to reduce all of the thickness unevenness rate, overall length outer diameter variation, and shear flaw occurrence rate.

Next, examples of changes to the extrusion speed control pattern used in carrying out the method of the present invention will be explained.

FIG. 3 shows an example of a modification of the extrusion speed control pattern, and shows a pattern to be used when the billet to be pipe-made is a long billet in which temperature distribution occurs in the length direction. In such a pattern, the extrusion speed in the stable extrusion stage ■ following the upset stage ■ is V2+
It is set to gradually increase from ■2□. When controlling using such a pattern, it is possible to gradually increase the extrusion speed in accordance with the temperature distribution in the longitudinal direction of the billet, thereby suppressing the speed drop in the low temperature section and improving external diameter variations etc. can be achieved.

〔effect〕

As detailed above, according to the method of the present invention, it is possible to control according to the material conditions of the billet and its extrusion ratio, and it is also possible to perform control that reflects the characteristics of the actual pipe manufacturing process. It is possible to reduce dimensional variations, occurrence rate of uneven thickness, occurrence rate of shearing defects, etc., and improve quality.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an apparatus used to carry out the method of the present invention, and FIGS. 2 and 3 are graphs illustrating extrusion speed control patterns used to carry out the method of the present invention.

Claims (1)

[Claims] 1. In a hot extrusion pipe manufacturing method in which a pipe is manufactured by inserting a heated billet into a container, upsetting the billet, and extruding it forward, extrusion is carried out according to the material conditions of the billet and its extrusion ratio. A hot extrusion pipe manufacturing method characterized in that various speed patterns are set in advance, and the extrusion speed is pattern-controlled in accordance with the ram movement distance based on the patterns.