JP2950051B2 - Die for hot extrusion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot extrusion die used for manufacturing a seamless tube or the like by hot extrusion.

[0002]

2. Description of the Related Art As shown in FIG. 1, a seamless tube is manufactured by hot extrusion by heating a hollow material 1 into a container 2.
It is manufactured by passing the material 1 through the material 1 and passing the mandrel 4 into the die 3 and pressing the material 1 forward in this state. That is, the pressed material 1 is tubularly extruded forward from an annular gap formed between the die 3 and the mandrel 4. Here, the die 3 is accommodated in the die holder 5 and supported by the die backer 6 from the front in the extrusion direction.

[0003] As a material of a die used for such a hot-extrusion pipe, SKD6 having little deformation and abrasion is used.
Alloy tool steels such as No. 1 are generally used, and recently, an integrated die made of a Mo-based or Ni-based heat-resistant alloy, which is more excellent in strength and wear resistance at high temperatures, is also used.

[0004]

However, the so-called bearing portion of the die in which the material comes into contact with the die has a high temperature of 900 to 1100 ° C. due to abrasion with the material and heat transfer from the material, and also has a large compressive force and shearing force. Receive strength.

[0005] Therefore, in the case of a die made of alloy tool steel, when the extrusion conditions of a small-diameter thin-walled tube or the like are severe or when the material is a difficult-to-work material, it is 0.5 to 2.0 mm in one working.
A degree of wear and deformation occurs in the bearing. as a result,
The dimensional accuracy of the product tube deteriorates. In addition, the life of the die is shortened, and the cost of pipe production is increased.

On the other hand, in an integrated die made of a heat-resistant alloy, wear and deformation of the bearing portion are small. But M
An o-based heat-resistant alloy is expensive, and it is difficult to suppress an increase in pipe production cost even if wear and deformation are suppressed. In this regard, Ni-based heat-resistant alloys are relatively inexpensive, and usually this integrated die is used.

However, Ni-based heat-resistant alloys are inferior in strength at room temperature as compared with alloy tool steel. The die is supported by a die backer 6 or the like in a die holder 5 as shown in FIG. 1, and the supporting portion does not become as hot as the inner surface during processing. Therefore, the die itself may be deformed depending on the pushing force. When the die itself deforms,
The dimensions of the product tube are extremely reduced, making it difficult to reuse the dies. In addition, deformation and wear of the bearing portion are becoming insufficient under recent severe extrusion conditions.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hot extrusion die having little deformation and wear of a bearing portion even under recent severe extrusion conditions, and having no possibility of causing deformation of the die itself.

[0009]

According to the hot extrusion die of the present invention, the die body is made of alloy tool steel, and at least the inner surface including the bearing portion has an average particle diameter in a base metal made of a heat-resistant alloy. It is characterized in that a composite material in which heat- and abrasion-resistant compound particles of 50 to 100 μm are dispersed at a ratio of 10 to 50% by mass is built up.

[0010]

In the hot extrusion die of the present invention, a composite material in which heat-resistant and wear-resistant compound particles are dispersed in a base metal made of a heat-resistant alloy is built up on the inner surface including the bearing portion. The deformation and wear of the bearing part are even less than the heat-resistant alloy integrated die.

Further, since the die body is made of an alloy tool steel having excellent room-temperature strength, the die itself, which is a problem with the integrated die made of a heat-resistant alloy, does not occur.

Further, since the composite material is integrated with the die body by overlaying, there is no possibility that this portion is detached from the die body. In the case of the hot extrusion pipe, the mandrel is pulled backward after the extrusion is completed, so that the bearing portion receives a strong force in both the front and rear directions and may be detached when the composite material ring is fitted.

The base metal used for the composite material is Mo based, N
As a heat-resistant alloy such as i-base, a Ni-base heat-resistant alloy such as Hastelloy C276 and Inconel 718 (both are trade names) is more economical and desirable.

As the compound particles to be dispersed in the base metal, for example, NbC, WC or the like can be used. These have not only high hardness and abrasion resistance at high temperature but also a specific gravity equivalent to that of the base metal and are advantageous in promoting the dispersion of the compound particles at the time of overlaying.

The content of the compound particles is from 10 to 5 in mass ratio.
0%. If it is less than 10%, the effect of improving the strength and abrasion resistance at high temperatures is small, and if it exceeds 50%, the toughness of the composite material is reduced, and there is a risk that cracks may occur during overlaying or extrusion.

The average particle size of the compound particles is 50 to 100 μm.
m. If it is less than 50 μm, it is difficult to disperse the particles.
If it exceeds 0 μm, the toughness of the composite material is significantly reduced.

The cladding can be carried out irrespective of its type, for example, by plasma-spraying a mixture of a base metal powder and a compound powder. Further, the present invention can also be carried out by gas shielded arc welding using a wire in which a compound powder is filled in a metal tube made of a base metal.

The area of the build-up requires a bearing portion on the inner surface of the die body. The approach portion and the relief portion before and after the bearing portion may be padded as necessary.

It is preferable that the padding allowance is 2 mm or more.
That is, if the thickness is less than 2 mm, the component ratio of the alloy tool steel that dissolves in the composite material increases, and there is a concern that the original high-temperature strength of the composite material cannot be obtained. The upper limit is not particularly limited, but with an increase in the build-up allowance, the number of build-up increases, and there is a risk that the strength of the heat-affected zone of the alloy tool steel may decrease, so that the strength does not decrease. It is desirable to set the limit, which differs depending on the component composition of the alloy tool steel used. Therefore, it is preferable to determine the limit by appropriate experiments and not to exceed the limit.

[0020]

Embodiments of the present invention will be described below.

In producing the extruded tube shown in Table 1 under the conditions also shown in Table 1, three types of dies were used.

The first die is an integrated die made of alloy tool steel SKD61 (JIS G4404) whose composition is shown in Table 2. The second die is an integrated die made of a Ni-based heat-resistant alloy (Hastelloy C276) whose component composition is shown in Table 2. As shown in FIG. 2, the third die is provided with the composite material 2 on the entire inner surface including the bearing portion of the die body 10.
0 is built up and the inner surface is finished by cutting. The die body 10 is manufactured from the above alloy tool steel,
The composite material 10 was coated by plasma cladding thermal spraying. The base metal of the composite material 10 was the Ni-base heat-resistant alloy, and the compound particles were NbC. The diameter of the NbC particles was 100 μm on average, and the content was variously changed in the range of 0 to 60% by mass.
The overburden allowance of the composite material in the bearing part is 3 mm,
1 mm was removed by cutting.

Table 3 shows the use results of each die. The amount of change in inner diameter is the amount of change in the inner diameter of the bearing part by one extrusion, and the number of repetitions means that the amount of change in the inner diameter is 1.0 m.
m is the number of repetitions of the extrusion until it reaches m or more.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

The tool steel integrated die has an inner diameter variation of 0.5 m.
m and the number of repetitions is only two. The heat-resistant alloy integrated dies have a small amount of inner diameter fluctuation per processing,
Since the die itself was deformed by the single processing, it could not be used repeatedly. On the other hand, the die in which the composite material of the heat-resistant alloy and the compound powder is overlaid has a smaller inner diameter variation than the heat-resistant alloy integrated die as long as the amount of the compound powder is appropriate. In addition, since there is no deformation of the die itself and no peeling of the composite material, the number of repetitions is greatly increased. Furthermore, the cost of the die itself is low because the composite is locally used and the body is made of inexpensive tool steel. Therefore,
Along with the improvement of the dimensional accuracy of the product, a reduction in pipe production cost is achieved.

[0028]

As is clear from the above description, the hot extrusion die of the present invention has a small deformation and abrasion of the bearing portion and has no deformation of the die itself, so that it can be used repeatedly many times. It is. Furthermore, since the composite material for suppressing deformation and wear is locally used, the cost of the die itself is low. Therefore, the ratio of the die cost to the product manufacturing cost is reduced, and the manufacturing cost is significantly reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an outline of a hot extrusion pipe production method.

FIG. 2 is a cross-sectional view schematically illustrating a configuration example of a die of the present invention.

[Explanation of symbols]

 10 Die body 20 Composite material

Claims (1)

(57) [Claims] A die body is made of alloy tool steel, and at least an inner surface of the die including a bearing portion is provided with heat-resistant and wear-resistant compound particles having an average particle diameter of 50 to 100 μm in a base metal made of a heat-resistant alloy. A hot extrusion die characterized in that a composite material dispersed at a ratio of mass% is built up.