JPS59190345A - Aluminum or aluminum alloy ingot having deformed cross-section for working - Google Patents

Abstract

PURPOSE:To obtain the titled ingot enabling the stable manufacture of a forged article having an acute angle by continuously casting Al or an Al alloy so as to provide a shape having an acute angle in its cross-section while specifying the grain size of the structure and the space between secondary dendrite arms. CONSTITUTION:Al or an Al alloy is continuously cast by a hot top continuous casting method using a gas pressure impressing system or other method so as to provide a deformed cross-section having at least one acute angle as shown by the figures, and the cooling rate is properly selected as to form a structure in which >=85% of the grains have <=180mum grain size and >=90% of the spaces each between secondary dendrite arms are <=25mum. The resulting Al or Al alloy ingot can be used as cast to manufacture stably an Al or Al alloy article having an acute angle by plastic working, cold forging or other forming.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum or aluminum alloy ingot that has excellent plastic workability, particularly forging workability9, more specifically, an ingot that has no microstructure and whose cross section has at least one acute angle. This is a continuous casting ingot of aluminum or aluminum alloy for machining in a shape having a section.

As is well known, forged products made of aluminum or aluminum alloy have high strength per unit weight, that is, specific strength.
It also has excellent impact resistance, fatigue strength, corrosion resistance, etc., and as a highly reliable material, it is widely used as a component of aircraft, automobiles, ships, and various other mechanical devices.

For this type of forging material, extruded round bars from large-diameter billets have conventionally been used in most cases, and some have been used by punching rolled plates from sheet ingots.

However, if continuous casting ingots such as billets and sheet ingots are extruded and rolled, it goes without saying that the processing itself requires considerable processing costs, but it also results in a structure that is extremely undesirable as a material for forging. It's hard to avoid. In other words, if such plastic working is applied to a continuously cast ingot, (1) the crystal grains and second phase particles (crystals and precipitates of primary crystals and intermetallic compounds) in the ingot will be elongated in the plastic working direction; As a result, a directional fiber structure is formed. (2) During extrusion, the surface layer of the extruded material recrystallizes due to frictional heat generated by the die and the crystal grains become coarse, and in the longitudinal cross-section of the extrusion, coarse grains tend to form at the rear due to the heat generated during the process. . During forging processing, the direction of the fiber structure shown in (],) above is extremely important, and if forging is performed in the opposite direction, cracks may occur, and mechanical strength and fatigue strength may partially decrease. Such materials may be difficult to use depending on the shape of the product. Therefore, in the case of forged products with complex shapes, methods such as first forging the ingot into a gentle cross-sectional shape and then finishing forging are adopted, but the two-step forging increases the cost, and the overall process is limited. It is not possible to add forging processing that exceeds the rate. Although there are methods such as intermediate annealing to improve this problem, it is difficult to significantly improve the processing rate.

As a result of various studies to solve the above-mentioned problems, the present inventors have discovered an excellent aluminum alloy ingot for forging that does not require prior extrusion processing, rolling processing, etc., and therefore has no restrictions on directionality, and a method for producing the same. , and patent applications are pending (Japanese Patent Laid-Open No. 56-69344, Japanese Patent Laid-open No. 56-69346, and Japanese Patent Laid-open No. 56-69348). The above-mentioned aluminum alloy ingots for forging are currently being used in the commercial production of a wide variety of forged products, and are achieving the desired results. However, there are still points that need improvement for forged products with complex shapes. discovered. In other words, in the case of forged products with sharp edges, if the raw material is a continuous cast ingot with a customary circular, square, or rectangular cross section, defects such as cracking, entrainment, and lack of thickness will easily occur at the pointed end. That's true. This means that at the sharp point,
This is thought to be because the processing rate is significantly higher than in other parts, but in order to solve these difficulties, it is possible to switch from cold forging to hot or warm forging, or to strengthen the leaf-shaped forging of the material. However, since this increases costs, there is a need for materials that can be cold forged without such preliminary processing.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide an aluminum or aluminum alloy ingot for processing that allows stable production of forged products having acute corners.

The aluminum or aluminum alloy ingot for processing according to the present invention is a continuously cast ingot, and consists of a structure in which 85% or more of the crystal grains have a grain size of 1180 μm or less, and 90% or more of the secondary dendrite arm interval has a grain size of 25 μm or less, The ingot is characterized in that its cross section has at least one substantially acute angle.

In the present invention, "processing" is not necessarily limited to forging processing, but includes general plastic processing such as swage processing, roll forming, rolling, drawing, and extrusion processing.

Furthermore, "continuous casting" refers not only to so-called completely continuous casting, but rather to the production of columnar ingots by vertical semi-continuous casting, which is commonly performed in non-ferrous metals, but continuous plate casting is not covered by the purpose of the present invention. be.

In addition, the term "9 cross section" of the ingot refers to a cross section cut in a direction substantially perpendicular to the axis of the columnar ingot. A columnar ingot with one acute corner is the object of the present invention.

However, in the present invention, the acute angle part is not limited to the shape of a sharp tip as shown in FIG. This includes those in which a substantial acute angle is formed.

The present invention requires that 85% or more of crystal grains have a grain size of 180 μm or less and that 90% or more of secondary dendrite arm intervals have a grain size of 5 μm or less as a structure in a cross section of an ingot in any direction. Due to such a fine casting structure, the ingot can be used as a material for plastic processing without undergoing preliminary plastic processing such as extrusion or rolling, and has excellent plastic workability and is suitable for forging. Machinability such as cutting after isoplastic processing is also good. In addition to the above-mentioned structural requirements for the ingot, more preferably primary crystals and All-
Ou.

M-8i1Mg-8i1M-Mn-Fe, Al1-
In an aluminum alloy in which Fe-8i, M- and silicon have a hypereutectic region, it is desirable that the particle size of primary silicon is at least 50 μnL or less for at least 70 cycles.

An ingot with the above-mentioned structural requirements depends on the alloy composition, but mainly depends on the cooling rate during ingot production (the cooling rate of the solid-liquid interface during continuous casting, which substantially corresponds to the solidification rate of the alloy. ), and the lower limit of the cooling rate that satisfies the above-mentioned microstructural requirements for each alloy can be confirmed in advance through experiments. According to the experiments conducted by the present inventors, the lower limit of the cooling rate is about 15'-30°O/sec for various aluminum or aluminum alloys, and casting of alloy ingots with such rapid cooling is performed by direct cooling vertical semi-continuous. The casting method is most suitable, but since the cooling medium is industrially room-temperature water, it is most economical to reduce the diameter of the ingot to increase the cooling rate. In the case of high-silicon alloys, it is also desirable to add a modifier such as P to the molten metal to simultaneously refine the primary silicon.

As the direct-cooled vertical semi-continuous casting method, the commonly used float continuous casting method may be used, but the hot top continuous casting method using gas pressure application, which was previously developed by the present inventors, 54-42847, Patent No. 1007387
According to No. 1), the obtained ingot has very little reverse segregation of alloying elements to the surface layer and has a smooth casting surface, so it can be plastically worked without peeling.

For columnar ingots with irregular cross-sections such as those of the present invention, which are extremely difficult to peel, it is industrially very advantageous to be able to forge them while leaving the cast surface intact.

Example 1) Alloy used: ■JIS6061, ■JIS20172
) The cross-sectional shape of the ingot is an equilateral triangle with a knee side of 55 mm, and the apex is an arc with a radius of 6 degrees (mold dimensions) 3) Continuous casting method: Gas pressure application hot tofu' continuous casting method (Special Publication 1977-
42847) 4) Cooling rate: 27°O/sec The surface skin of the columnar ingot cast under the above conditions exhibited a homogeneous and smooth appearance over the entire circumference. The macrostructure of the ingot is fine and homogeneous as shown in Figure 2 (JIS-6061 alloy). As shown in Table 1, the microstructure of the ingot was observed for the skin and center.
, (b) Center part, Fig. 4 (J l5-2017) (a
) Skin part, surface layer; DAS: Secondary dendrite arm spacing Surface part: Lower layer of reverse segregation layer The above aluminum alloy ingot remains cast without peeling.\Plasticity of aluminum or aluminum alloy products having sharp corners It is extremely advantageous in that it can be used for processing and forming, especially cold forging, and can be formed without causing cracks or the like due to excessive plastic working.

[Brief explanation of drawings]

FIG. 1 is an illustration of the cross-sectional shape of a columnar ingot, which is the object of the present invention. Figure 2 is a macrostructure photograph of a columnar ingot according to the present invention whose cross section is an equilateral triangle, and Figure 3 is a photograph of the JIS-60 according to the present invention.
Figure 4 is a microstructure photograph of the JIS-2017 alloy according to the present invention, where (a) is the skin part and (b) is the center part. Patent applicant Showa Light Metal Co., Ltd. Agent Sei Kikuchi (α') (b) (C) Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1 Continuous casting ingot of aluminum or aluminum alloy, in which 85% or more of the crystal grains have a grain size of 180 μm,
Aluminum or aluminum for machining irregular cross-sections, characterized in that 90% or more of the secondary tendrite arm spacing is composed of a structure of 25 μm or less, and the cross section of the ingot has at least one substantially acute angle. Alloy ingot.