Metal treatment – Process of modifying or maintaining internal physical... – Heating or cooling of solid metal
Reexamination Certificate
2001-03-27
2003-12-09
Wyszomierski, George (Department: 1742)
Metal treatment
Process of modifying or maintaining internal physical...
Heating or cooling of solid metal
C148S693000, C148S697000
Reexamination Certificate
active
06660111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method of manufacturing an Al—Mg—Si series alloy plate excellent in thermal conductivity and intensity.
2. Description of Related Art
Generally, Japanese Industrial Standards (hereinafter referred to as “JIS”) A5052 aluminum alloy is used as high intensity aluminum materials for heat exchanger parts, metallic base printed circuit boards, cutting members, etc. However, JIS A5052 aluminum alloy is inferior in thermal conductivity by 30% or more as compared with pure aluminum. On the other hand, pure aluminum having high thermal conductivity is extremely low in strength and inferior to JIS A5052 aluminum alloy in cutting processability. This pure aluminum requires removal of burrs after cutting processing, resulting in poor finished surface appearance.
Furthermore, Al—Mg—Si series alloy is also used as aluminum material of high intensity in which fine Mg
2
Si particles are precipitated uniformly to improve the strength. The fine Mg
2
Si precipitation can be obtained by heat treatment, which improves strength and recovers toughness by hardening and annealing the alloy after cold rolling. Heating the alloy in general rolling process does not cause uniform and fine Mg
2
Si precipitation, but merely causes independent precipitation of Mg and Si, resulting in insufficient strength improvement.
Thus, under the present circumstances, it is additionally required to perform heat treatment after cold rolling, resulting in an increased step, which causes an increase in the manufacturing cost. Furthermore, in cases where a thin plate having a thickness of 0.1 mm or the like is manufactured from heat treatment type alloy such as Al—Mg—Si series alloy, since it was common to subject the alloy plate of 1 mm thickness or less to solution treatment in a continuous annealing furnace, it was difficult to increase the cold working rate. As a result, it was difficult to obtain high hardness.
Japanese Unexamined Laid-open Patent Publication No. H6-272001 discloses a method of manufacturing an Al—Mg—Si series alloy plate in which hot rolling conditions are specified. This technique intends to restrain big and rough precipitation from being generated during hot rolling in order to perform short-time solution treatment after cold rolling, and does not intend to promote fine Mg
2
Si precipitation during the rolling process.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method of manufacturing aluminum alloy with outstanding thermal conductivity and hardness in fewer steps.
According to the present invention, a method of manufacturing an Al—Mg—Si series alloy plate excellent in thermal conductivity and hardness, includes the steps of: preparing Al—Mg—Si series alloy ingot consisting essentially of Si:0.2-0.8 wt %, Mg:0.3-0.9 wt %, Fe:0.35 wt % or less, Cu:0.20 wt % or less and the balance of aluminum and inevitable impurities; homogenizing the alloy ingot; subjecting the alloy ingot to rough hot rolling to obtain a roughly hot rolled plate; subjecting the roughly hot rolled plate to finish hot rolling to obtain a finished hot rolled plate; and subjecting the finished hot rolled plate to cold rolling, wherein one of the rough hot rolling is controlled such that material temperature immediately before the one of the rough hot rolling is from 350 to 440° C., cooling rate between the one of the rough hot rolling and rough hot rolling subsequent thereto is 50° C./min or more, material temperature immediately after the one of the rough hot rolling is from 250 to 340° C. and plate thickness immediately after the one of the rough hot rolling is 10 mm or less, and wherein the cold rolling is controlled such that rolling reduction is 30% or more.
It is preferable that Si content of the Al—Mg—Si series alloy ingot is from 0.32 to 0.60 wt % and/or Mg content of the Al—Mg—Si series alloy ingot is from 0.35 to 0.55 wt %.
It is preferable that the material temperature immediately before one of the rough hot rolling is from 380 to 420° C., and/or the plate thickness immediately after one of the rough hot tolling is 8 mm or less.
It is also preferable that the rolling reduction of the cold rolling is 50% or more.
Furthermore, it is preferable to further perform last annealing at 180° C. or below after the cold rolling
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be detailed as follows. In the method of manufacturing an Al—Mg—Si series alloy plate excellent in thermal conductivity and hardness, the significance and reasons for the limitation of each element of the target Al—Mg—Si alloy composition will be explained as follows.
Mg and Si are essential elements for giving strength to the alloy. If Mg content is 0.3 wt % or less and/or Si content is 0.2 wt % or less, sufficient strength cannot be obtained. On the other hand, if Mg content exceeds 0.9 wt % and/or Si content exceeds 0.8 wt %, the rolling load in the hot rolling will increase, which causes a deterioration of productivity and necessitates trimming of the rolled plate before the finish rolling because of large cracks. The desirable lower limit of Mg content is 0.35 wt %, and the desirable upper limit thereof is 0.55 wt %. On the other hand, the desirable lower limit of Si content is 0.32 wt %, and the desirable upper limit thereof is 0.60 wt %.
Too much Fe and Cu causes a deterioration of corrosion resistance, resulting in an alloy plate of no practical use. Therefore, it is necessary to regulate the content of Fe and Cu such that Fe content is 0.35 wt % or less and Cu content is 0.20 wt % or less. The desirable Fe content is 0.25 wt % or less, and the desirable Cu content is 0.10 wt % or less.
The alloy composition falling within the aforementioned range causes outstanding thermal conductivity equivalent to pure aluminum.
In the method according to the present invention, fine Mg
2
Si particles can be precipitated uniformly by applying rolling under the prescribed conditions after the homogenization. As a result, effects equivalent to effects obtained by solution treatment and quenching can be obtained.
The conditions of the homogenization are not specifically limited. It is preferable to perform the homogenization for 2 hours or more at 500° C. or above in accordance with a conventional method.
In the rough hot rolling, effects equivalent to effects obtained by quenching can be obtained by the temperature reduction while rough hot rolling under the predetermined temperature conditions in any rough hot rolling pass. Therefore, the material temperature immediately before the rough hot rolling is required to fall within the range of from 350 to 440° C. which can retain the dissolved state of Mg and Si like in solution treatment. If the material temperature is below 350° C., Mg
2
Si becomes big and rough precipitation at this time, and thus the subsequent quenching effect cannot be obtained. Furthermore, since the material temperature is low, the rolling nature of the subsequent rough hot rolling pass deteriorates remarkably, the material temperature immediately after the rough hot rolling pass becomes too low, resulting in a deterioration of the surface quality. On the other hand, if the material temperature exceeds 440° C., the material temperature will not drop enough immediately after the rough hot rolling, causing insufficient quenching effects. The preferable lower limit of the material temperature immediately before the rough hot rolling is 380° C., and the preferable upper limit is 420° C. Furthermore, in order to obtain the quenching effects, it is required to control such that the cooling rate between subsequent rough hot rolling passes is 50° C./min and that the material temperature immediately after the hot rolling pass falls within the range of from 250 to 340° C. In order to control the material temperature immediately after the hot rolling pass so as to fall within the aforementioned range, forced cooling such as high-pressure shower water cooling may be performed immediately after the rough hot rolling. Furthermore, it
Kimura Kazuo
Shimao Ryosuke
Taguchi Kyohei
Tsukuda Ichizo
Combs-Morillo Janelle
Showa Aluminum Corp.
Wyszomierski George
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