JPS5913287B2 - High temperature lubricated extrusion die - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a die used in so-called high-temperature lubricated extrusion, in which a billet is extruded with a lubricant interposed between the die and a billet, such as in cylindrical isostatic extrusion.

It is well known that metal materials can be extruded by a lubricated extrusion method, and it is also well known that if a billet is heated to a high temperature and then extruded, it can be extruded at a higher extrusion ratio and at a higher speed than when extruding a billet at room temperature.

However, in high-temperature lubricated extrusion, seizure in the die area is more likely to occur than in cold lubricated extrusion, and as a result, significant vertical scratches occur on the product surface, making it difficult to obtain a stable product.
This tendency is particularly remarkable for aluminum alloys and the like.

Conventionally, in order to prevent this seizure, the die shape has been made multi-stage, or the entire approach area has an uneven surface (another method is to provide circumferential grooves in the entire approach area). A known method is to prevent direct contact between the die and the billet during extrusion by trapping lubricant in the billet.

However, since these methods have a large lubricant trapping effect, the lubricant is caught between the die and the product, and the surface of the extruded product is dotted with concave marks, or in severe cases, concave marks are formed. may occur in a ring shape.

Degenerated lubricant is generally attached to the recesses on the surface of these products, and it is extremely difficult to remove it.

In addition, as extrusion dies, there are known flat dies that have a flat surface that contacts the billet, and so-called conical dies that have an approach surface whose inner diameter gradually decreases in the extrusion direction. In the case of lubricated extrusion, conical dies are generally used because the lubrication conditions are very good.

This is because a wedge-shaped annular space is formed between the outer peripheral surface of the billet and the inner surface of the die approach part, and the high-pressure lubricant is present in this space, so the lubricant easily enters the contact surface between the billet and the die. This is because a so-called wedge effect occurs in which the lubrication condition there is maintained extremely well.

It is true that in the case of a die that has an approach part whose inner diameter gradually decreases in the extrusion direction, a large amount of lubricant is interposed between the billet and the die, and seizure does not occur.
Although it can be said that they are excellent in terms of lubrication, in the case of this type of die, the trapping effect of the lubricant between the die and the billet is too large, so sometimes
The billet surface in the die deformation area becomes depressed due to the entrainment of excessive lubricant, and the product surface is dotted with many concave marks, or the concave shapes form in the form of links. The current situation is that the effects cannot be fully utilized.

In view of the above-mentioned problems, it is an object of the present invention to provide a high-temperature lubricated extrusion die that does not cause seizure and is capable of extruding a sound product. The approach portion has an uneven surface of 5 to 50 μm in width, leaving a smooth portion with a width of 0.2 mm to 5.0 μm at the bearing portion side end of the approach portion whose inner diameter gradually decreases in the direction of the bearing portion.

That is, the present invention maintains the lubricant trapping effect by forming an uneven surface with a moderate roughness of 5 to 50 μ (Rmax) by shot blasting or the like in most of the area from the entrance side of the approach part. In addition to preventing seizing, there is also a width of 0 at the bearing side end of the approach
．． By providing a normal temperature part of 2 mm to 5.0 mm, it is possible to prevent the lubricant from getting caught between the die and the product and prevent local breakage of the lubricant film, thereby obtaining a healthy product.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 shows an embodiment of the high-temperature lubricated extrusion die according to the present invention. In FIG. 1, 1 is a die body, 2 is an approach portion, and 3 is a bearing portion.

The approach part 2 has a width of 0.2 mm at the side end of the bearing part 3.
A roughness of 5 to 50 μm is provided by shot blasting or the like, leaving a smooth portion 4 of ~5.0 μm.

Incidentally, the approach portion 2 may be composed of one conical surface as in the embodiment shown in FIG. 1, or may be composed of a combination of a plurality of conical surfaces.

The effects of the present invention will become clear from the following specific experimental results using the dice of the present invention.

The inventors have experienced that concave defects, which are traces of lubricant entrainment, occur on the surface of products extruded using conventional dies that have unevenness over the entire approach area. We investigated methods for obtaining a product surface from various viewpoints.

Among these many experiments, when coating the billet surface with lubricant was carried out for 1/2 length of the leading end (nose side), but not for the trailing end (jllll/2 length). An interesting phenomenon was observed on the surface of the extruded product.

In other words, concave marks are noticeable on the leading half of the product, while there are some vertical scratches on the rear end, but no concave defects are observed, indicating that lack of lubrication is the cause of the product surface After discovering something related to soundness, we repeated the following experiments.

A 2024 aluminum alloy with a diameter of 42 mm and a length of 200 mm was used as a billet, and using bentonite grease as a pressure medium, it was hydrostatically extruded at a heating temperature of 300° C. into a 45φ product at a stem speed of 2 Qmm/FieC.

After the billet was machined into a predetermined shape, its surface was coated with a graphite lubricant and extruded.

As shown in Fig. 2, the approach part 2 of the die consists of a combination of three conical surfaces, and the approach part 2 can be treated by shot blasting or by manufacturing a jig with many convex shapes and pressing it. An uneven surface was formed by changing the surface roughness in the range of 3μ or less to 120μ.

Furthermore, the width of these dies was changed to a smooth area of 0 to 8 mm near the bearing part 3, and care was taken not to completely affect this smooth area by shot blasting or the like.

The experimental results are summarized in Table 1. As is clear from Table 1, when an uneven surface is formed in the entire area of the approach part 2 (when the width of the smooth part 4 is 00), if the roughness of the approach part is 3μ or less, seizure will occur in the approach part. 35-40%) Cracks have occurred on the product surface,
At 5 to 10μ, slight seizure and traces of lubricant entrainment are observed on the product surface, and as the roughness of the approach portion becomes higher than that, the traces of lubricant entrainment become larger.

If the roughness of the approach part is 3μ or less, seizure will occur regardless of the width even if a smooth part is provided, and cracks will occur in the product.If the roughness of the approach part is 5 to 50μ depends on the width of the normal temperature area.

In other words, when the width of the smooth part is set to 0.2 mmJ, J, or more, no seizure of the approach part or defects in the product (cracks, traces of lubricant entrainment) occur, and good extrusion can be performed. However, when the width of the smooth portion exceeds 5.0 mm, seizure occurs at the approach portion.

Furthermore, if the roughness of the approach portion exceeds 50μ, traces of lubricant entrainment occur regardless of the width of the smooth portion.

In other words, there is a width of 0.2 at the bearing section side end of the approach section.
It has been confirmed that good extrusion results can be obtained by forming an uneven surface of 5 to 50 μm on the approach part and performing high temperature lubricated extrusion while leaving a smooth part of ~5-0 mm.

This is because if the roughness of the approach part is 3μ or less, the trapping effect of the lubricant is small, and this is a condition where seizure is likely to occur, especially since extrusion is carried out at high temperatures.
Although the effect of providing an uneven surface on the approach part is achieved, seizure occurs, and if the roughness of the approach part exceeds 50μ, the trapping effect of the lubricant becomes too thick, and the lubricant This is because the lubricant is excessively rolled up, which causes rolled-up marks on the product surface, and even if a smooth portion is provided near the bearing part, the excessive roll-up of the lubricant cannot be covered.

According to the die according to the present invention, the roughness of the approach portion is 5.
~50μ, the lubricant trapping effect is sufficient,
Seizure does not occur at the die approach area, and excessive entrainment of lubricant can be eliminated by providing a smooth part with a width of 0.2 to 5.0 degrees near the bearing part, which improves the quality of the product. Good extrusion results can be obtained without causing cracks or traces of lubricant entrainment on the surface.

In the example, an integrated die was explained, but in order to maintain a smooth state near the bearing part, the vicinity of the bearing part of the approach part and the bearing part are made of cemented carbide, etc., which is harder than the approach part. It is even more effective if a die of a combined type is used, and although aluminum alloy is shown in the embodiment, it is equally effective for other materials that are susceptible to seizure at high temperatures.

[Brief explanation of the drawing]

1 and 2 are front sectional views showing an embodiment of the high-temperature lubricated extrusion die according to the present invention, where 1 indicates the die body, 2 indicates the approach section, 3 indicates the bearing section, and 4 indicates the smooth section, respectively. ing.

Claims (1)

[Claims] 1. A smooth part with a width of 0.2 to 5.0 mm is left at the bearing part side end of the approach part whose inner diameter gradually decreases in the extrusion direction, and an uneven surface of 5 to 50 μm is formed in the approach part. High temperature lubricated extrusion die.