JPS5819428A - Production of hot-extruded alloy material - Google Patents

Abstract

PURPOSE:To obtain an alloy material having no striated defects equal to the defects when the hot-rolled blank material obtained from a continuously cast blank material by heating said blank material then subjecting the material to hot working to fine the structure of the surface layers followed by hot extrusion working. CONSTITUTION:A dummy block 2 is placed on the trailing end of a continuously cast blank material 1 which is lubricated on the outside surface, and the block is forced forward from behind the block by means of a stem 3 to pass the material 1 through an extrusion die 4 until the material is forced into a container 5. At the point of the time when the working ends, the surface layers of the material 1 are recrystallized to at least 3mm. thickness by the heat that the material possesses in the container 5, whereby fine crystal grains are formed in said layers. The material 1 having the surface layers of the fine crystal grains is pressurized from behind by the ram 3 in succession and while a glass lubricant is supplied from a disc 7, the material is passed through an extrusion die 6 having a desired hole diameter, whereby an extruded product 8 is obtained. Since the material 1 has the same fine structure as that of the hot rolled blank material resulted from the breakage of the cast structure prior to working with the die 6, the material produces no striated defects which are produced with conventional continuously cast blank materials even if said material is worked with the die 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for hot extrusion processing of tubes, round bars, shapes, etc. of alloy materials such as stainless steel and superalloys using continuous cast materials as raw materials.

Metal working methods are generally divided into hot working methods and cold working methods. Hot working methods are widely used as a method for reducing working force, and include rolling, extrusion, forging, and the like. The hot extrusion method is particularly advantageous in that it can achieve a high processing rate in one process, easily produce products in various shapes just by changing the die, and can process difficult-to-process metals without defects due to compression processing. It's advantageous.

The material to be subjected to hot extrusion processing is generally finished into a circular cross-sectional shape by a melting-ingot-forming-hot-blowing-rolling process (hereinafter, the material produced by this process is referred to as hot-rolled material). However, with the development of continuous casting technology, it is currently possible to manufacture continuously cast slabs with a circular cross section.9 The hot extrusion process is now possible through a single continuous casting process that eliminates the hot blooming and rolling process. The development of continuous casting technology, which has reached the stage where it can be manufactured (hereinafter the material produced through this process is referred to as continuous casting material), is no exception to the development of stainless steel, superalloys, etc., and can enjoy the advantage of omitting the above steps. We have reached the stage where we can expect a significant improvement in yield by applying continuous casting materials to hot extrusion processing.
However, when continuous casting materials are subjected to "hot extrusion processing", if the material does not undergo structural transformation during heating and cooling, streak-like defects occur frequently on the surface of the extruded material in the extrusion direction, which seriously reduces its commercial value. There is a drawback. For this reason, conventionally, it has not been possible to hot extrude continuously cast materials such as stainless steels and superalloys to produce hot extruded materials such as pipes, round bars, and shapes. Incidentally, this streak-like defect is hardly seen when a hot-rolled material is used.

The purpose of the present invention is to manufacture hot extruded materials such as stainless steel medium superalloys that do not undergo structural transformation when heated to hot extrusion temperature and cooled, when hot rolled materials are used instead of continuously cast materials. It is possible to obtain a surface quality of the extruded material that is equivalent to or better than that of the extruded material.

Continuously cast materials have a cast structure with strong directionality, while hot-rolled materials have such a cast structure destroyed during the hot blooming process and become a microcrystalline structure, which causes the directionality to change. Because of the randomization, the present inventor completed the present invention as a result of various experimental studies on methods for refining the structure of continuous casting materials before hot extrusion processing. That is, the continuous casting material is heated and hot worked to refine the structure of the surface layer at least 3 mm thick from the surface, and then hot extruded.

The specific method of the present invention will be described below.

An example of the manufacturing method is shown in Fig. 1.The continuous casting material 1, whose outer surface has been lubricated, is placed on the rear end of the continuously cast material 1, and is continuously cast by pushing it forward through the stem 3 from behind. The casting material 1 passes through a pushing die 4' and is pushed into a container 5. The continuous casting material 1 undergoes processing by passing through the pushing die 4. When this processing is completed,
; Recrystallization occurs in the surface layer due to the heat of the material 1 in the antenna 5, resulting in fine crystal grains. The continuously cast material 1, whose narrow surface layer has become fine crystal grains, is then processed from the rear of the stem 3. While being pressed and supplied with glass lubricant from the lubricated glass disk 7, it passes through an extrusion die 6 having the desired pore size to form an extruded product 8.

By this method), the cast structure of the continuously cast material 1 is destroyed before it is processed by the extrusion die 6 and it becomes the same microstructure as the hot rolled material, so even if it is processed by the extrusion die 6,
There are no streak-like defects that occur in conventional continuous casting materials. Figure 2 shows an outline of the process of pushing a continuous casting material 1 in two stages with a container as another example. In this case, M1 is also used.
Using the same mechanism as shown in the figure, the microstructure of the material can be obtained just before extrusion.

Next, examples will be described.

The extrusion conditions are Fit-1, Pass 9. Extrusion conditions Material steel type: Sc2O3, 8U8321 Material heating temperature: 1200°C Lubricating glass Window glass Figure 3: Continuously cast material, ・: Conventional hot-rolled material, and a: Invention The continuously cast material in b shows the metallographic structure of the material cross section after indentation processing of the continuous cast material in the example.
The nc hot-rolled material has a recrystallized microstructure.In contrast, the continuous cast material according to the invention example 1 (indentation rate 1
1G), a cast structure of approximately 40φ remains in the center, but the surrounding area has a fine structure down to the surface of the material. The appearance of the products obtained by extrusion processing these materials is shown in the fourth section.
In extruded products made of continuously cast material whose entire cross section has a coarse casting structure, as shown in Figure ・b, streak-like defects that reach a maximum of 100μ occur, but as shown in There are no streak-like defects in the extruded product shown in (a).On the other hand, in the extruded product with a microstructure before final extrusion obtained by the extrusion method according to the example of the present invention, as shown in (a), a slight cast structure remains in the center of the material. However, there are no streak-like defects at all.This is similar to the Nl-based Nl pace suit.
Regardless of the type of steel, such as alloy, the same effect was seen due to recrystallization refinement after indentation.

Table 2 shows the surface roughness measurement results for the entire circumference and 150-length in the longitudinal direction of the extruded product. The roughness of the cast material extruded product is 70 in the circumferential direction.
~100μ, 30-50μ in the longitudinal direction. In the circumferential direction, the rounding roughness of the streak-like defects increases, and in the longitudinal direction, the roughness level is low because the roughness is mainly due to the lubricating glass. On the other hand, the roughness of the products of the hot-rolled material C and the continuously cast material A according to the example of the present invention is 20 to 40 μ in both the circumferential direction and the longitudinal direction, and there is no difference between the two.

This is due to the lubricated glass, and indicates that no streak-like defects occur.

As described above, the method of the present invention completely eliminates streak-like defects and makes it possible to obtain surface quality equivalent to that of conventional extruded hot-rolled materials.

In the above examples, the area reduction rate during indentation was 15.5-, there was only a slight unrecrystallized area in the center of the material, and no large Ka streak defects were observed on the extruded material surface, but due to the extrusion schedule. If the area reduction rate of indentation is smaller than the example,
The unrecrystallized area becomes larger. In such a case, there is a possibility that a streak-like defect will occur at the tip of the extruded material. As a countermeasure against this, it is possible to prevent streak-like defects at the tip of the extruded material by cold-working the end face of the material using shot blasting or the like and recrystallizing the cold-worked region in a thermal process during extrusion. In this case, it is sufficient that the recrystallized fine region has a thickness of at least three thicknesses from the surface.

[Brief explanation of drawings]

FIG. 1 is a process diagram for explaining an embodiment of the present invention,
FIG. 2 is a diagram showing another embodiment, FIG. 3 is a diagram showing the metal structure of a cross section of the material after indentation, and FIG.
It is a figure which shows the external appearance of the product obtained by extrusion processing the material of a figure. Patent applicant: Shin Nippon Keiryu Co., Ltd. 20. S 3rd a b q 4th a b c

Claims (3)

[Claims] (1) Hot processing characterized by heating and hot working a material made of continuous casting material to refine the structure of a surface layer of at least 3cm thick from the surface, followed by hot extrusion and extrusion processing. A method for producing extruded alloy materials. (2) The hot-extruded alloy according to claim 1, wherein the hot-extruded alloy is hot-processed using a die provided in front of a container of a hot-extrusion processing machine, and the material surface layer is recrystallized within the container. Method of manufacturing wood. (3) A method for manufacturing a hot extruded alloy material according to claim 1 or 2, characterized in that the end face of the material is subjected to cold working before heating.