JPH10328727A - Method for preheating mandrel of hot extruding tube and heating device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly heat only the surface layer part of a mandrel and to reduce the amount of scale generation as much as possible by heating the mandrel so that the temperature distribution of the mandrel in the axial direction becomes prescribed pattern with high frequency induction heating just before setting the mandrel to a hot extruding press. SOLUTION: A heating device is installed between a container 8 attached with a hollow billet composing a hot extrusion tube press and the retreating limit of a stem in which a ram is inserted through. A lateral type high frequency induction heating furnace 5 lifting up and down using a means of a reciprocating cylinder 5a, etc., is installed on a carriage 7 reciprocating between the inlet side face 8a of the container 8 and the retreating limit of the stem 9 with a means of a reciprocating cylinder 7b, etc. The carriage 7 and the high frequency induction heating furnace 5 are moved to the front face position of the stem 9, and a mandrel 4 is preheated at a prescribed temperature. Next, the carriage 7 and the high frequency induction heating furnace 5 are returned to the original position and the mandrel 4 is instantly supplied for producing a tube.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preheating a mandrel used in a hot extrusion tube and a heating apparatus used for the method.

[0002]

2. Description of the Related Art It is well known that a mandrel is used for a hot extrusion tube represented by the Eugene Sejournet method. This mandrel is usually screwed at room temperature to a ram of an extrusion press, and is used for extrusion of a hollow hollow material.

[0003] However, a mandrel at room temperature reduces the inner surface temperature of a hollow billet heated to a predetermined temperature,
It deteriorates the inner surface quality of the extruded tube. Therefore, prior to its use, the mandrel at room temperature is brought to a predetermined temperature (usually 1).
(200-250 ° C.).

[0004] Conventionally, a burner-type atmosphere heating furnace using gas, heavy oil, or the like as a fuel fixedly installed near a hot extrusion tube press is used to set a hot extrusion tube press before the hot extrusion tube press. Was preheated to the target mandrel, but there were the following problems (a) to (c).

(A) Depending on the performance of the heating furnace, for example,
The surface temperature of a mandrel with an outer diameter of 100 to 200 mm is 10
Preheating takes a long time, for example, it takes 1 to 4 hours to reach 0 to 250 ° C. For this reason, it is necessary to frequently replace the mandrel when producing small-sized products having different dimensions. However, it is not possible to preheat the mandrel to a predetermined temperature before the replacement, which impairs productivity. In addition, the prolonged heating increases the scale (mainly iron-based oxide) generated and adhered to the mandrel surface, which is a factor of deteriorating the inner surface quality of the extruded tube.

(B) It is virtually impossible to precisely control the temperature of each part in the furnace. For this reason, for example, the temperature of the bottom side of the hollow billet decreases during the extrusion process, which deteriorates the inner surface quality of the extruded tube. In order to prevent this, the rear end of the mandrel (ram side) is more advanced than the front end. Heating at an appropriate temperature distribution such as heating to a high temperature cannot be performed.

(C) Due to the characteristics of the atmosphere heating furnace, there is a temperature difference between each part in the furnace, specifically, near the burner installation part and near the charging / extracting port of the mandrel to be heated. For this reason, for example, in the case where a plurality of mandrels are simultaneously heated in order to cope with frequent mandrel replacement at the time of the above-mentioned small-lot product production, a variation occurs in the preheating temperature between the mandrels. The inner surface quality between the extruded pipes also varies, and stable quality cannot be ensured.

(D) Since the atmosphere heating furnace takes a long time to heat, it cannot be placed in a hot extrusion tube press. For this reason, mandrel preheating is performed by fixing the atmosphere heating furnace heat near the hot extrusion tube press, but if the mandrel replacement work takes a long time due to unexpected trouble, a relatively strict temperature The temperature of the mandrel that needs to be controlled decreases, which degrades the inner surface quality of the extruded tube. In such a case, it is sufficient to perform preheating again, but this further impairs productivity.

Therefore, not only the above (a) to (c) but also
It has been desired to develop a method for preheating a mandrel that can also solve the disadvantage described in (d) and a heating device used for the method.

[0010]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned situation, and has the following problems. However, the present invention provides a method for preheating a mandrel and a heating method used in the method. It is to provide a device.

The mandrel before use can be heated in a short time. An arbitrary temperature distribution can be provided in the axial direction of the mandrel. Able to preheat the mandrel after setting in the hot extrusion tube press.

[0012]

As a result of various experiments and studies to achieve the above object, the present inventor has found that the preheating of the mandrel does not necessarily have to have the same temperature at the center and at the surface layer. It was confirmed that the temperature of the part should be set to a desired temperature. Accordingly, the present invention has been made by paying attention to a high-frequency induction heating technique that can rapidly heat only the surface layer to a predetermined temperature in the circumferential direction uniformly and that generates as little scale as possible. .

The gist of the present invention based on the above findings is as follows: (1) and (2) a method for preheating a hot extruded pipe mandrel, and (3) and (4) a preheating method for a hot extruded pipe mandrel. In the heating device.

(1) A method for preheating a mandrel used in a hot extrusion tube, wherein a temperature distribution in the axial direction of the mandrel using a high frequency induction heating means immediately before setting the mandrel in a hot extrusion tube press. Is heated so as to have a predetermined pattern.

(2) A method for preheating a mandrel used in a hot extrusion tube, wherein after setting the mandrel in a hot extrusion tube press, the high-frequency induction heating means is used to reduce the temperature distribution in the axial direction of the mandrel. A method for preheating a mandrel for a hot-extrusion pipe-making pipe, characterized by heating to a predetermined pattern.

(3) A heating device used in the method according to the above (1), wherein a plurality of sets of annular coils connected to an independent power supply device are arranged continuously with their axes aligned. A horizontal high-frequency induction heating furnace equipped with a temperature measuring means for measuring the surface temperature of a mandrel as a body to be heated in each of the annular coils, and an output of each of the power supply devices based on a temperature measurement result of the temperature measuring means. A temperature control device for controlling;
The high-frequency induction heating furnace is fixedly installed in the vicinity of a hot extrusion tube press, and the mandrel holding means is provided so as to be capable of moving toward and away from the high-frequency induction heating furnace. A heating device for a mandrel for a hot-extrusion pipe-making tube.

(4) A heating device used in the method according to (2), wherein a plurality of sets of annular coils connected to an independent power supply device are arranged continuously with their axes aligned. A horizontal high-frequency induction heating furnace equipped with a temperature measuring means for measuring the surface temperature of a mandrel as a body to be heated in each of the annular coils, and an output of each power supply device based on a temperature measurement result of the temperature measuring means. The high-frequency induction heating furnace is movable up and down or horizontally on the inlet side of the container of the hot extrusion tube press, and in the axial direction of the hot extrusion tube press. A heating device for a hot-extrusion pipe mandrel, which is provided so as to be reciprocally movable.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for preheating a mandrel according to the present invention and a heating device used in the method will be described in detail with reference to the accompanying drawings.

<< Preheating Method >> In the present invention, as shown in FIG. 1, the axes are aligned and connected to each other, and each is connected to an independent power supply device 2 ₁ , 2 ₂ , 2 ₃ ,. and a plurality (shown example three) annular coil ₁ 1, 1 _2,
1 _3, high-frequency induction heating furnace 5 of the lateral is used consisting of ....

The high-frequency induction heating furnace 5 above, the substantially central portion of each annular coil 1 _1, 1 _2, 1 _3, ... consecutively provided direction,
Temperature measuring means 3 ₁ , 3 ₂ , such as a radiation thermometer for measuring the surface temperature of the mandrel 4 as the material to be heated,
3 ₃ ,... Are provided.
Are connected to the temperature control device 6 together with ₁ , 2, ₂ , ₃ ...

[0021] Then, the temperature control device 6 described above, the annular coil ₁ 1, 1 _2, 1 _3, and heated is inserted into ... within each temperature measuring means 3 _1, 3 _2, 3 _3, measured by ... Each power supply device 2 is based on a comparison result between the surface temperature of each part of the mandrel 4 in the axial direction and the target preheating temperature of each part of the mandrel 4 in the axial direction set in the temperature control device 6 in advance.
_1, 2 _2, 2 _3, to adjust the ... output, thereby adapted to preheat the mandrel 4 by applying a predetermined temperature distribution in the axial direction.

When the horizontal high frequency induction heating furnace 5 configured as described above is used, the following effects (A) and (B) are obtained.

(A) Since high-frequency induction heating is used, the mandrel can be heated to a predetermined preheating temperature in a short time. As a result, it is possible to quickly respond to frequent replacement of the mandrel required when producing small-sized products having different dimensions, and productivity is not hindered. In addition, since the heating is performed for a short time, the scale generated and adhered to the mandrel surface is small, and the deterioration of the inner surface quality of the extruded tube is suppressed.

(B) the high-frequency induction heating furnace comprises a plurality of annular coils connected to an independent power supply;
Since the surface temperature of the mandrel at the portion heated by each annular coil can be measured and controlled by the temperature measuring means, an arbitrary temperature distribution can be provided in the axial direction of the mandrel. As a result, for example, it is possible to heat the rear end of the mandrel located on the bottom side of the hollow billet to a higher temperature than the front end side, which lowers the temperature during the extrusion and causes deterioration of the inner surface quality of the extruded tube. In addition, deterioration of the inner surface quality of the extruded tube is suppressed.

<< Regarding the Heating Apparatus >> There are two types of heating apparatuses according to the present invention, one of which is to set a mandrel before being set in a hot extrusion tube press as a preheating target. It is a device installed near. The other one is intended to preheat a mandrel set in a hot extrusion tube press, and is an apparatus installed in the hot extrusion tube press.

FIG. 2 is a schematic side view showing a heating device installed in the vicinity of a hot extrusion tube press. As shown in the drawing, this heating device is fixedly installed on a floor using a column. Horizontal high-frequency induction heating furnace 5 having the above configuration
And a carriage 7 which can be freely moved toward and away from the high-frequency induction heating furnace 5 by using an appropriate means such as a reciprocating cylinder 7b.

A support plate 7a provided with a female screw into which a male screw 4a (see FIG. 1) formed at the rear end of the mandrel 4 is screwed is provided on the carriage 7, and the mandrel 4 is mounted on the support plate 7a. Can be held cantilever horizontally.

Then, the mandrel 4 is inserted into the horizontal high-frequency induction heating furnace 5 by moving the carriage 7 from the position shown by the thick solid line in the drawing to the position shown by the dashed line, and is preheated to a predetermined temperature. The carriage 7 is returned to the position indicated by the thick solid line, the mandrel 4 is removed from the support plate 7a, and the mandrel 4 is set on a hot extrusion tube press.

FIG. 3 is a schematic side view showing a heating device installed in a hot extrusion tube press. As shown in FIG. Provided between the container 8 in which the biletto is inserted and the retreat limit of the stem 9 through which the ram penetrates, and similarly to the above, the inlet side surface 8a of the container 8 and the stem 9 are provided by appropriate means such as a reciprocating cylinder 7b. And a horizontal high-frequency induction heating furnace 5 having the above-described structure, mounted on the carriage 7 so as to be able to move up and down by appropriate means such as a reciprocating cylinder 5a. It is composed of

At any time (during pipe production), the carriage 7 and the horizontal high-frequency induction heating furnace 5 are kept at a position shown by a thick solid line in the figure to correspond to the production of product pipes having different dimensions. After the used mandrel is removed from the ram and a new mandrel 4 is set on the ram, the carriage 7 and the horizontal high-frequency induction heating furnace 5 are moved to the position indicated by the one-dot chain line in the figure to move the mandrel 4 to a predetermined position. After preheating to a temperature, the carriage 7 and the horizontal high-frequency induction heating furnace 5 are returned to the position shown by the thick solid line, and the mandrel 4 is immediately provided for pipe production.

In the case of the heating device shown in FIG. 2 among the above two types of heating devices, when the heated mandrel 4 is removed from the support plate 7a and set on the ram of the hot extrusion tube press, the temperature drop occurs. Is inevitable. For this reason, it is necessary to heat the preheating temperature to a higher temperature in anticipation of the temperature drop, and the scale generated and attached to the surface of the mandrel 4 increases by that amount, and the effect of suppressing the deterioration of the inner surface quality of the extruded pipe is impaired. This is not the case with the heating device shown in FIG. Therefore, it is more preferable to use the apparatus shown in FIG.

When the mandrel before being set in the hot extrusion tube press is to be preheated and a plurality of mandrels are to be heated at the same time as in the heating apparatus shown in FIG. 2, for example, as shown in FIG. What is necessary is just to make an apparatus configuration. That is, while a high-frequency induction heating furnace 5 having a large inner diameter (see FIGS. 3C and 3D) is prepared, a plurality of mandrels 4, 4,. Support plate 7c that can be held and held (see FIGS. 7A and 7B)
May be set up. However, in this case, since each mandrel 4 is heated by deviated heat in the circumferential direction, it is desirable to use a high-frequency induction heating furnace in which an annular coil having a small inner diameter is arranged so as to coincide with the axis of each mandrel.

[0033]

EXAMPLE A heating apparatus shown in FIG. 2 equipped with a high-frequency induction heating furnace having the specifications shown in Table 1 and an atmosphere heating furnace having the specifications shown in Table 2 were prepared.

[0034]

[Table 1]

[0035]

[Table 2]

Then, the outer diameter is 157.3 mm and the length is 140
A 0 mm SDK61 mandrel was preheated in the high-frequency induction heating furnace and the atmosphere heating furnace described above, and had an outer diameter of 285 mm and an inner diameter of 1 mm.
658.7 m long, 930 mm long, 168.7 m outside diameter from a SUS304 hollow billet heated to 1210 ° C.
m, a wall thickness of 7.1 mm, and a length of 6900 mm were provided for an extruded tube.

In the case of a high-frequency induction heating furnace, the preheating temperature of the mandrel is 120 ° C. at the tip and 15 ° C. at the middle.
At 0 ° C., the rear end was heated to 180 ° C. On the other hand, in the case of the atmosphere heating furnace, since the temperature difference imparting heating cannot be performed, the entire length thereof is heated to 150 ° C.

As a result, the time required to complete the preheating of the mandrel is about two hours in the case of the atmosphere heating furnace,
Since many scales were generated and adhered to the surface of the mandrel, many flaws were generated on the inner surface of the extruded tube.

On the other hand, in the case of the high-frequency induction heating furnace, the preheating was completed in about 3 minutes, and scale was hardly formed on the surface of the mandrel. It was about one-third less than in the case of preheating.

[0040]

According to the present invention, the mandrel used for pipe making can be heated to a predetermined temperature for a short time, and an arbitrary temperature distribution can be given in the axial direction thereof.
As a result, not only can extruded pipes with good inner surface quality be obtained, but it is also possible to adequately cope with frequent mandrel replacement during the production of small-sized products with different dimensions, impeding productivity. Never be.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a preheating mode of a mandrel according to the present invention.

FIG. 2 is a schematic side view showing an example of a heating device according to the present invention.

FIG. 3 is a schematic side view showing another example of the heating device according to the present invention.

FIG. 4 is a schematic view showing still another example of the heating device according to the present invention, wherein FIG. 4 (a) is a front view of a truck, FIG. 4 (b) is a side view of the truck, and FIG. The front view of the high-frequency induction heating furnace, and FIG. 2D is a longitudinal sectional view of the high-frequency induction heating furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Annular coil, 2; Power supply device, 3; Temperature measuring means, 4; Mandrel, 4a; Male screw, 5; High-frequency induction heating furnace, 5a, Returning cylinder, 6; Temperature control device, 7; Dolly, 7a; 7b; return cylinder, 7c; support plate, 8; container, 8a; entry side of the container, 9;

Claims (4)

[Claims] 1. A method for preheating a mandrel used for a hot extrusion tube, wherein a temperature distribution in the axial direction of the mandrel is set using a high frequency induction heating means immediately before setting the mandrel in a hot extrusion tube press. A method for preheating a mandrel for a hot-extrusion pipe-making pipe, characterized by heating to a predetermined pattern. 2. A method for preheating a mandrel used for a hot extrusion tube, comprising: setting a mandrel in a hot extrusion tube press; A method for preheating a mandrel for hot extruded pipes, characterized in that the mandrel is heated so as to form a pattern. 3. A heating device used in the method according to claim 1, wherein a plurality of sets of annular coils connected to an independent power supply device are arranged continuously with their axes aligned.
A horizontal high-frequency induction heating furnace equipped with a temperature measuring means for measuring the surface temperature of a mandrel as a body to be heated in each of the annular coils, and an output of each of the power supply devices based on a temperature measurement result of the temperature measuring means. The high-frequency induction heating furnace is fixedly installed in the vicinity of a hot-extrusion tube press, and comprises a mandrel holding means for holding the mandrel horizontally, and a mandrel holding means for the high-frequency induction heating furnace. A heating device for a mandrel for a hot-extrusion pipe, characterized by being provided so as to be able to move freely. 4. A heating device used in the method according to claim 2, wherein a plurality of sets of annular coils connected to an independent power supply device are arranged continuously with their axes aligned.
A horizontal high-frequency induction heating furnace equipped with a temperature measuring means for measuring the surface temperature of a mandrel as a body to be heated in each of the annular coils, and an output of each power supply device based on a temperature measurement result of the temperature measuring means. Temperature control device to control
The high-frequency induction heating furnace is provided on the entrance side of the container of the hot extrusion tube press so as to be movable vertically and horizontally and reciprocally movable in the axial direction of the hot extrusion tube press. A heating device for a mandrel for a hot extrusion tube.