JPH03188238A - Free cutting aluminum alloy for hot forging - Google Patents

Abstract

PURPOSE:To obtain the free cutting Al alloy for hot forging having excellent forgeability, in which sufficient strength can be obtd. as well by natural aging and furthermore having excellent machinability at the time of working by adding specified amounts of Mg, Zn, Cu, Mn, etc., to Al. CONSTITUTION:Al is incorporated with, by weight, 0.3 to 2.0% Mg, 3.0 to 8.0% Zn, 0.5 to 3.5% Cu and 0.2 to 2.0% Mn, furthermore, as free cutting elements, with at least one kind among 0.15 to 2.5% Pb, 0.15 to 2.5% Bi and 0.15 to 2.5% Sn and, if required, moreover with 0.05 to 0.25% Zr. The free cutting Al alloy free from the generation of cracks at the time of hot forging and having good forgeability can be obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for hot forging that has excellent hot forging properties, hardenability during heat treatment, aging properties, and machinability during processing. This relates to machined aluminum.

[Prior art] Conventionally, aluminum alloys subjected to hot forging were
High strength (7) JIS 2000 series and 7000 series aluminum heat-treated alloys are generally used. In order to obtain the specified strength, these alloys are subjected to solution treatment, rapid cooling (quenching), and artificial aging treatment after hot forging; sufficient strength cannot be obtained without artificial aging treatment. I can't.

In addition, these alloys do not have good machinability, and cannot satisfy high-speed machinability, which is particularly desired as a property of aluminum processed materials.

This free-cutting material with improved machinability is JIS2
000 series, 600o series c7) 77L/ Me 1-'
7 Pb alloy, which is a low melting point metal, is used as a base.
, B+, etc., have been put into practical use.

However, even with this free-cutting alloy, in order to obtain the necessary strength, it is necessary to perform sufficient heat treatment such as quenching treatment or artificial aging treatment. Furthermore, the forgeability is poor in that cracks occur during forging.

By the way, recently there has been a desire to reduce manufacturing costs and simplify the heat treatment process, and free-cutting aluminum for hot forging is designed to obtain the necessary strength through natural aging without the need for artificial aging. An alloy has been proposed (Japanese Patent Application Laid-open No. 73045/1983).

[The problem that the invention tries to solve! ! 1] However, even in the above alloys that allow natural aging,
The hardness improvement due to aging was not sufficient, and the forgeability was also unsatisfactory.

The basic purpose of this invention is to solve the above-mentioned problems, and to provide an aluminum alloy that improves forgeability, has sufficient strength through natural aging, and has excellent machinability during processing. It is something to do.

[Means for Solving the Problems] In order to achieve the above object quickly, a free-cutting aluminum alloy for hot forging according to the first invention of the present invention has M g 0.
3-2.0wt%, Zn 3.0-8.0wt%
, Cu 0.5-3.5 wt%, Mn 0.2-2.
Contains 0wt% and further contains Pb 0.15-2.5w
t%, B10.15-2.5w t%, Sn 0.1
It is characterized by containing at least one selected from 5 to 2.5 wt%, with the remainder consisting of Al and unavoidable impurities.

Moreover, the free-cutting aluminum alloy for hot forging in the second invention contains Mg 0.3 to 2.0wt%, Zn3°0 to
8.0wt%, Cu 0.5-3.5wt%, Mn0
゜2~2.0wt%, Zr 0.05~0.25w
t% and further contains Pb 0.15-2.5wt
%, Bi 0.15~2.5wt%, Sn 0.15~
It is characterized in that it contains at least one selected from 2.5wt%, and the remainder consists of Al and inevitable impurities.

Next, the purpose and reason for limiting the range of each additive element in the alloy of the present invention will be described.

Mg and Zn are converted into MgZn in the base material by heat treatment.
Forms z precipitates and contributes to improving the strength of the base metal.

However, when the amount of each element added is excessive, deformation resistance increases and forgeability decreases.

Furthermore, increasing the amount of Mg improves aging properties, but excessive addition reduces hardenability.

Therefore, the amount of each additive element to be added is set to Mg 0.3 to sufficiently achieve the above effects and not to be excessive.
~2.0wt%, Zn 3.0~8.0t%.

Cu Next, like Mg and Zn, Cu can be treated by heat treatment.
Precipitates of CLJAl2 are formed in the base metal, contributing to improving the strength of the base metal and also improving natural aging properties.

However, if the addition becomes excessive as the amount is increased, the hardenability and forgeability will deteriorate, so the addition amount should be 0.5~
It should be within the range of 3.5wt%.

In addition, as mentioned above, the addition of Cu increases the amount of Cu A 12 precipitated in the base material as the amount increases, and the addition amount increases by 1.
．． At 1 wt% or more, the effect becomes noticeable. Moreover, if the addition amount is 3.0wt% or less, more suitable hardenability and forgeability are ensured.

Therefore, it is preferable that the amount of Cu added is further limited to the range of 1.1 to 3.0 wt.

In addition, the addition of Cu can be increased compared to the conventional method by adding Mn, which will be described later, and this increase improves strength and natural aging properties without impairing hardenability and forgeability. It became possible.

Mn Next, as a result of intensive research, the present inventors found that in the alloy of the present invention, Mn improves the structure of the material without reducing the hardenability, and significantly improves the forgeability. .

Specifically, if Mn is not added or if a small amount of Mn is added, the material structure becomes an equiaxed crystal structure partially containing coarse crystal grains, and cracks may occur starting from these during hot forging. However, when an appropriate amount of Mn is added, the material structure becomes a uniform fine fibrous structure, making it difficult to form crack starting points during hot forging. , therefore, forgeability is significantly improved.

However, if excessively added, the hardenability is reduced, so the amount added is within the range of 0.2 to 2.0 wt%.

Pb, Bi, 5nPb, 8i, and Sn are low-melting point metals, and by adding these, chips of the material are shredded by processing heat during cutting, resulting in free machinability. However, when these elements are added in excess, the same effect becomes excessive, and the material melts locally during hot forging, becoming a starting point for hair cracks and reducing forgeability. For this reason, P
b0.15-2.5W t%, B j 0.15-2.
5 wt%, and at least one selected from Sn0.15 to 2.5 wt%. Note that when three types are added, the total amount added is preferably 5 wt % or less for the same reason.

Zr Zr performs almost the same function as Mn. However, since its solid solution range is narrow, addition of a small amount is allowed. Therefore, if necessary, 0. It shall be added within the range of OS to 0.25 wt%.

[Function] That is, according to the free-cutting aluminum alloy for hot forging of the present invention, the occurrence of cracks during hot forging is effectively prevented,
Improves forgeability.

In addition, the hardenability is improved, making it possible to harden using the temperature during hot forging, and even when heating is performed in a separate process, low-temperature hardening is possible.

In addition, aging properties are improved, and sufficient strength improvement can be obtained through natural aging. Furthermore, the chips during cutting become fine pieces, making high-speed cutting possible and improving machinability.

[Implementation 1 row] An embodiment of the present invention will be described below.

As an example of the present invention, an aluminum alloy (No. 1 to 5) having a composition shown in Table 1 was used.
A 1 mm billet was manufactured by a semi-continuous casting method, subjected to a homogenization treatment, and then extruded into a round bar with a diameter of 40 mm using an indirect extrusion bridge.

For comparison, as shown in Table 1, a comparative aluminum alloy (No.
, I to 8) were prepared, and a round bar was manufactured in the same manner as in the example.

A round bar obtained from each of the above-mentioned alloys has a length of 00 mm.
After cutting and heating to 380℃, reduction 60%
Upset forging (hot forging) was carried out, and the forgeability was evaluated. As for the evaluation, as shown in Table 1, those that were successfully forged without any cracks were marked with a circle, and those with partial cracks were marked with an X. Specifically, the forged processed material was etched in a 10% caustic soda solution at 45° C., and the presence of cracks on the surface was visually observed.

Next, in order to evaluate the hardenability of each alloy, the round bar was hot forged, and the hot-worked material of Q was water-cooled immediately after forging.
After performing artificial aging at 120°C for 24 hours, the hardness was measured and this hardness was used for quenching evaluation. In this evaluation, those with sufficient hardness improvement were marked with a circle, and those with insufficient hardness improvement were marked with x (Table 1).

In addition, in order to evaluate aging properties, in a separate treatment from the above-mentioned quenching, the extruded round bar was heated at 380°C for a period of time, and then
The material was cooled with water, subjected to natural aging at 20° C. for 24 hours, and the hardness was measured. The evaluation was based on the hardness, and those in which aging had progressed sufficiently were indicated by a Q mark, and those in which the degree of aging had progressed insufficiently were indicated by an x mark (Table 1).

Next, in order to evaluate the strength, the round bar was heated at 380°C for 1 hour in the same manner as in the aging evaluation above, and after cooling with water, it was heated to 20°C.
Natural aging was performed for 24 hours, and the tensile strength was measured. In the evaluation, those with a tensile strength of 35 g/m m2 or more are deemed to have sufficient strength and are marked with a circle, and 35K
If the strength was less than g/mm2, it was marked with an X, indicating that the strength was insufficient.

Furthermore, in order to evaluate the machinability of the round bar after natural aging, cutting was performed under the following conditions, and the machinability was evaluated based on the shape of the chips generated at this time. In this evaluation, the one with the most finely broken chips is evaluated by palanque, and the chips are ranked sequentially as B-
Evaluated with E rank.

In addition, in the A and 8 ranks, the chips were in a shredded shape and the machinability was good, but in the C-E ranks, the chips were in a continuous spiral shape and the machinability was poor.

Cutting conditions Depth of cut 3mm Feed amount 0. 1mm/
REV cutting speed a I 30 m/min Tool used: Carbide tool (hereinafter referred to as margin) As is clear from Table 1, the alloy of the present invention is No.
, l to NO35 were excellent in all points of hot forgeability, hardenability, aging resistance, strength, and machinability.

On the other hand, the alloy of the comparative example did not satisfy all of the above evaluation items, but was poor in any of the items. In particular, the evaluation of forgeability was poor, and in Comparative Example No. 004, which was the only sample with good forgeability, the machinability was extremely poor.

[Effects of the Invention] As explained above, the free-cutting aluminum alloy for hot forging of the present invention contains Mg0j to 2.0wt%, Zn3.
0-8.0wt%, Cu Q, 5-3.5wt%,
Contains Mn 0.2-2.0 wt%, and further contains Pb0
．． +5 to 2.5 wt%, Bi 0. +5~2.5wt
%, Sn0.15 to 2.5 wt%, and optionally Zr0.05
~0.25wt%, and the remainder consists of Al and unavoidable impurities, so it has excellent forgeability and improves product quality without cracking. Furthermore, it has good hardenability and aging properties, and by simplifying the charm treatment process, it is possible to improve work efficiency and reduce manufacturing costs. In addition, sufficient hardness can be obtained through natural aging,
Furthermore, it has excellent machinability, and has the effect of producing an aluminum alloy with high strength and excellent workability.

Claims (1)

[Claims] 1. Mg0.3-2.0wt%, Zn3.0-8.0w
t%, Cu0.5-3.5wt%, Mn0.2-2.0
further contains Pb0.15 to 2.5 wt%,
Bi0.15-2.5wt%, Sn0.15-2.5w
t%, and the remainder is A.
Free-cutting aluminum alloy 2 for hot forging, characterized by consisting of l and inevitable impurities, Mg0.3-2.0wt%, Zn3.0-8.0w
t%, Cu0.5-3.5wt%, Mn0.2-2.0
wt%, Zr0.05-0.25wt%, further Pb0.15-2.5wt%, Bi0.15-2.5
A free-cutting aluminum alloy for hot forging, characterized in that it contains at least one selected from wt%, Sn0.15 to 2.5wt%, and the remainder consists of Al and inevitable impurities.