JPS6210246A - Manufacture of hot-forged products of aluminum alloy - Google Patents

Abstract

PURPOSE:To obtain hot-forged products of aluminum alloy causing no exposure of snakeskin-patterned recrystallized grain structure at the surface and having an attractive aluminum color, by subjecting an Al alloy ingot containing each prescribed amount of Zn, Mg, Mn and Zr to homogenizing treatment, hot forging by the ordinary method and then solution heat treatment. CONSTITUTION:The Al alloy ingot containing 4.0-5.0% Zn, 1.0-2.0% Mg, 0.35-0.7% Mn and 0.1-0.3% Zr is subjected to homogenizing treatment at 430-515 deg.C for 4-48hr, preferably at 470-510 deg.C for 6-10hr. Subsequently, the above homogenized ingot is hot-forged with adjusting the preheating temp. of the stock to 320-450 deg.C, preferably 360-400 deg.C. Then the above hot-forged products are subjected to solution heat treatment at 350-465 deg.C for 30-120min, preferably at 380-450 deg.C for 30-90min, which are subjected to washing and anodic oxidation film treatments by and under conventional method and conditions, so that the desired hot-forged products of Al alloy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for improving hot forging of aluminum alloys.

Conventional technology Conventionally, to manufacture medium-sized to small-sized forged products of aluminum alloy, extruded rods are used as raw materials and forged, but in order to prevent the formation of a snakeskin pattern on the outer surface, the tails of the extruded rods are cut off, The outer circumference of the rod is shaved off before it is forged.

Problems to be Solved by the Invention The structure of extruded rods in the prior art has a large degree of directionality, forming a prominent IIM-like structure in the length direction. In areas subjected to intense extrusion, the surface layer of the extruded rod and the extrusion tail (rear part of the billet), the tendency to release is reduced or granular crystals form. Grain recrystallization and its coarsening also occur due to temperature increases during hot forging and solution treatment.

This granular recrystallized surface can be etched (e.g. by caustic cleaning).
Alternatively, anodizing creates a snakeskin pattern, and in motorcycle parts where appearance is important, the appearance is poor and the product value is lost, so as mentioned above, the tail of the extruded rod is cut off or the outer periphery of the rod is scraped off. It is forged from -.

Therefore, there are problems such as a decrease in yield, complicated management due to an increase in the number of processing steps, instability in production planning, and an increase in processing costs due to an increase in the number of inspection steps.

Means for Solving the Problems The present invention was made to solve the above problems, and includes Zn: 4.0-5.0%, Mg: 1.0-5.0%.
2.0%, Mn: 0.35-0.7%, Zr0.1
430-51 aluminum alloy ingot containing ~0.3%
A method for producing a hot forged aluminum alloy product, which comprises homogenizing at 5°C for 4 to 48 hours, hot forging by a conventional method, and then solution treatment at 350 to 465°C for 30 to 120 minutes. It is.

Mn and Zr in the above composition are effective for forming an IIM-like structure, and it is difficult to obtain a fibrous structure even if their content is less than the lower limit or exceeds the upper limit.

A more preferable amount of Mn is 0.35 to 0.55%,
Further, a more preferable amount of Zr is 0.15 to 0.25%.

Zn and M(+ are added to improve the strength of the product. If the amount is less than the lower limit, the strength will be insufficient, and if it exceeds the upper limit, the extrudability will deteriorate.

Furthermore, each of trace components other than those mentioned above may be contained in an amount of 0.05% or less.

In the present invention, the main steps for forging such a compositional alloy ingot are homogenization → extrusion → cutting → heating → forging → solution treatment → cleaning and anodizing treatment.

The homogenization treatment is carried out at 430 to 515°C for 4 to 48 hours, but if any value is lower than the lower limit or higher than the upper limit, the crystal grains become coarse and tend to form a snakeskin pattern. More preferably, the temperature is 470 to 510°C for 6 to 10 hours.

Extrusion is normal indirect extrusion, and the outer circumference of the circular cross-section billet is
~4Il+m 7 After peeling one side, billet temperature 2
Taberheat at 00-450°C, more preferably 250-420°C, container temperature 350-430°C, more preferably 360-400°C, extrusion speed 2-20 m/mi
Do it with n.

Hot forging is performed at a preheating temperature of the material of 320 to 450°C, preferably 360 to 400°C.

The solution treatment is carried out at 350 to 465°C for 30 to 120 minutes, but if the upper limit is exceeded, the crystal grains will become coarse. A more preferable range is 380 to 450°C for 30 to 90 minutes.

The cleaning and anodic oxidation film treatment may be performed using any conventionally used method and conditions.

Example Zn: 4.8%, lylg: 1.12%, Mn
:0.42%, Zr:0.19%, Fe:0.13%,
5ilo, 03%, CIJ: 0.07%, Ti: 0.0
1%, remainder A1, diameter 260m1, length 130m
A 0 mm alloy ingot is peeled to a diameter of 254 mm.

After homogenizing this, the billet temperature is 270-400.
℃, container temperature 380℃, extrusion speed 4m/min
(45111nφ, 4-hole press) to form an extruded rod. At this time, the billet temperature was 400℃ at the head and 27℃ at the bottom.
Taberheat at 0°C (0.1°C/min >).

This extruded rod is hot forged at 380°C.

Then, after solution treatment, cleaning and anodic oxidation coating treatment are performed.

The conditions of the homogenization treatment and solution treatment were varied, and the surface exposure state of the recrystallized grain structure of each extruded material was visually determined. The results are not shown in a table.

Comparative example Zn: 4.7%, M (1: 1.2%, Mn
: 0.3%, Zr: 0.15%, Fe: 0.13%
, 3i: 0.02%, Cu: 0.15%, Ti: 0.0
1%, Cr: 0.06%, and the balance A1 was hot forged under the same conditions as in Example 1.

Coarse crystal grains were exposed on the surface of both the head and tail of the extruded material. That is, exposure of coarse crystal grains was observed even when the amount of Mn was less than the lower limit of the present invention.

Effects of the Invention According to the method of the present invention, the recrystallized grain structure with a snakeskin pattern is not exposed on the surface of the forged product, resulting in a beautiful aluminum color. Since there is no need to scrape off the outer periphery of the extruded rod or cut off the tail, the number of processing steps is reduced, yield is improved, and costs are reduced.

As a result, production planning becomes stable and process control becomes easier.

Claims (1)

[Claims] Zn: 4.0-5.0%, Mg: 1.0-2.0%, M
An aluminum alloy ingot containing n: 0.35 to 0.7% and Zr 0.1 to 0.3% is homogenized at 430 to 515°C for 4 to 48 hours, and after hot forging by a conventional method, 46
A method for producing a hot forged aluminum alloy product, the method comprising solution treatment at 5° C. for 30 to 120 minutes.