WO2022119024A1 - Method for manufacturing aluminum alloy of medium-strength and high-ductility - Google Patents

Abstract

The present invention relates to a method for manufacturing aluminum alloy of medium-strength and high-ductility by controlling the solution-treatment and cooling steps in the manufacturing process thereof. Specifically, provided is a method for manufacturing aluminum alloy comprising: a heating step for heating, up to 500-560°C, aluminum alloy produced using an aluminum alloy composition; a solution-treatment step for maintaining the heated aluminum alloy for 5-7 hours; a cooling step for cooling, for 15 seconds to one minute, the aluminum alloy that has been solution-treated; and an aging step for age-hardening the cooled aluminum alloy. The method for manufacturing aluminum alloy and aluminum alloy manufactured thereby, according to the present invention, shorten the solution-treatment time to assure high ductility, and control the lowering speed of a palette between a solution treatment furnace and cooling water tank and the distance between the furnace and water tank to relatively extend the cooling time and thus reinforce residual heat-induced strength, thereby allowing aluminum alloy with excellent mechanical properties to be provided.

Description

Method for manufacturing medium-strength and high-ductility aluminum alloy

The present invention relates to a method for manufacturing an aluminum alloy, and more particularly, to a method for manufacturing a medium strength and high ductility aluminum alloy by controlling the solution heating step and the cooling step of the aluminum alloy manufacturing process.

Aluminum (Al) is easy to cast, alloyed with other metals, so it is easy to process at room temperature and high temperature, and has strong corrosion resistance in the atmosphere and good electrical and thermal conductivity, so it is widely used throughout the industry.

For the purpose of imparting various properties such as strength, hardness, abrasion resistance, impact resistance and workability, which are properties required for metals or alloys, heat treatment combining various operations of temperature increase and cooling is used, and the heat treatment is a metal or alloy of recrystallization, diffusion of atoms, and phase transformation are used.

That is, such heat treatment is generally used for the purpose of increasing the strength or hardness of a metal material, removing internal stress, etc., and improving the material properties by controlling the temperature, time, and speed of applying heat or cooling. There are heat treatment methods such as quenching, tempering, annealing and normalizing.

In particular, aluminum is very light, has excellent workability and corrosion resistance, and has excellent thermal and electrical conductivity. Alternatively, in the case of aluminum treated with some alloys, strength and hardness are increased through heat treatment, or stress is reduced or removed. In general, since aluminum alloy has a reinforcing phase component, physical properties such as strength and hardness improvement and stress removal are possible through heat treatment, but defects may occur depending on the method of construction.

In a general operating environment, these defects are minute and do not have a significant effect, but there is a problem in that the defects become prominent or occur when the temperature rises due to heat treatment or the like. In order to prevent defects occurring in the heat treatment process and improve physical properties, research on improving the structural design of the heat treatment apparatus as in Korean Patent Application Laid-Open No. 10-2018-0069268 is continuing.

In addition to the mechanical properties, the heat treatment temperature and subsequent process of the aluminum alloy affect the physical properties of the alloy, especially the strength and elongation. The need for an aluminum alloy manufacturing method is highlighted.

An object of the present invention is to provide a method for manufacturing an aluminum alloy in which heat treatment and aging conditions are controlled according to the above needs.

Another object of the present invention is to provide an aluminum alloy manufactured according to the method for manufacturing an aluminum alloy.

In order to achieve the above object, the present invention

A temperature raising step of heating the aluminum alloy prepared using the aluminum alloy composition to 500 ~ 560 ℃;

a solutionizing step of maintaining the elevated temperature of the aluminum alloy for 5 to 7 hours;

A cooling step of cooling the solution-ized aluminum alloy for 15 seconds to 1 minute; and

It provides an aluminum alloy manufacturing method comprising; an aging step of age hardening the cooled aluminum alloy.

The cooling is water cooling or air cooling.

The aging step is to age harden the aluminum alloy at 140 to 180° C. for 2.5 to 4 hours.

In order to achieve the above other object, the present invention

It provides an aluminum alloy manufactured according to the method for manufacturing an aluminum alloy of the present invention.

The aluminum alloy manufacturing method according to the present invention and the aluminum alloy manufactured according to the present invention secure elongation by shortening the solution heat treatment furnace and the cooling time by reducing the pallet lowering speed between the solution heat treatment furnace and the cooling water tank and the distance between the furnace and the water tank. It is possible to provide an aluminum alloy having excellent mechanical properties by reinforcing strength through residual heat by extending it.

1 is a graph of precipitation hardening according to aging time of an aluminum alloy used in an embodiment of the present invention.

2 is a graph of hardness according to the temperature deviation of the solution treatment step of the present invention.

3 is a graph of hardness according to the temperature deviation of the aging step of the present invention.

Hereinafter, the present invention will be described in more detail.

According to one aspect of the present invention, a temperature raising step of heating an aluminum alloy manufactured using an aluminum alloy composition to 500 ~ 560 °C; a solutionizing step of maintaining the elevated temperature of the aluminum alloy for 5 to 7 hours; A cooling step of cooling the solution-ized aluminum alloy for 15 seconds to 1 minute; and an aging step of age hardening the cooled aluminum alloy.

Among the heat treatment processes, the T6 method is a typical heat treatment method used for heat-treated aluminum alloys, and is used to improve hardness and mechanical strength by precipitating a compound dissolved by solution heat treatment.

Although it is different depending on the type and amount of mixed metal and the shape of the parts used, the T6 heat treatment process treats an aluminum alloy with a solution treatment, quenches it in water at room temperature, etc., and performs aging again. ) treatment to improve the strength and hardness of the aluminum alloy.

In the aluminum alloy manufacturing method of the present invention, heat treatment is performed for a relatively short time compared to the conventional heat treatment time in the temperature increase and solution heat treatment step. When the effect of the solution heat treatment is increased, the expectation of strength strengthening is high but the expectation of elongation is lowered. Accordingly, the present invention aims to solve the problem of a relatively low elongation by shortening the solution heating time to a predetermined time.

The solutionized aluminum alloy is cooled by water cooling or air cooling. The solutionized aluminum alloy may be cooled with a hot fluid or sprayed water, or the like. The high-temperature aluminum alloy that has undergone the solutionizing step may be cooled using water in a liquid state at room temperature, or may be cooled using water in a spray state such as fine droplets, or may be cooled in air, but is not limited thereto.

The aluminum alloy manufacturing method of the present invention is characterized in that it is cooled for 15 seconds to 1 minute in the cooling step. The cooling time can be controlled by adjusting the distance between the solution treatment furnace and the cooling water bath and the moving speed of the alloy pallet. Unlike the conventional rapid cooling conditions, it is possible to secure strength through residual heat as cooling proceeds over a relatively long period of time. There is an effect of shortening the solution heating time but increasing the cooling time so that the manufactured aluminum alloy secures a certain strength and at the same time also secures the elongation.

The aging step of the aluminum alloy manufacturing method of the present invention is characterized in that the aluminum alloy is age-hardened at 140 to 180° C. for 2.5 to 4 hours. It is possible to control the mechanical strength, especially the elongation, by controlling the temperature and time, which are the processing parameters of age hardening.

Since there is a difference in thickness and shape depending on the part to which the aluminum alloy is applied, it is necessary to continuously measure the overall temperature of the part during the heat treatment and aging step according to the present invention, so that a thermocouple, etc. It is preferable to accurately measure the temperature range, time, etc. using

The aluminum manufacturing method of the present invention largely includes solution heat treatment and aging treatment steps, and may constitute one apparatus including a dedicated furnace and a cooling water tank, respectively. The temperature generated by each device can be collected and monitored by the DAQ module, and it is desirable to design it to meet the heat treatment standards by homogenizing the temperature through adjustment of the temperature controller.

As described above, through the improved heat treatment process compared to the prior art, it is possible to obtain a medium-strength and high ductility aluminum alloy, which was difficult to secure with conventional heat treatment, and the degree can be controlled by adjusting the conditions of each process step.

Hereinafter, preferred embodiments of the present invention will be described in detail. On the other hand, the illustration and detailed description of the configuration and the action and effect thereof, which can be easily known from those of ordinary skill in the art, will be simplified or omitted, and the parts related to the present invention will be described in detail.

<Example>

The solution heat treatment temperature or the aging temperature was adjusted to set the optimization conditions for the solution heat treatment and aging treatment. 1 is a graph of precipitation hardening according to the aging time of the aluminum alloy used in the embodiment of the present invention, FIG. 2 is a hardness graph according to the temperature deviation of the solution heating stage of the present invention, and FIG. 3 is the aging stage temperature deviation of the present invention It is a graph of hardness. 1 to 3, the solution heat and aging temperature setting process will be described below.

To set the comparative standard, solution heat treatment was performed at 535°C for 8 hours while minimizing the variation in heat treatment temperature to within ±5°C for A356.2 alloy in a small furnace, and then the aging treatment was performed at different times at 155°C to increase the aging time. The time to reach the peak was confirmed by confirming the precipitation hardening phenomenon.

As a result of measuring the known hardness for each aging time under a load of 0.05 kg using a micro Vickers hardness tester, it was confirmed that the peak hardness was reached in about 4 hours.

Considering the deviation of the solution heating temperature, when the solution heating temperature was 515°C, which is 20°C lower than the reference, the change in the known hardness value after aging was not large. .

In fact, when the solution heating temperature rises to the maximum upper limit of 555 ° C, incipient melting occurs in the case of π-Al8FeMg3Si6 and Mg2Si secondary phases having a low melting point of 556-561 °C, and it was judged that the physical properties of the matrix tissue due to the generation of defects abruptly occurred.

In the case of fixing the solution heat condition and changing the aging temperature, the difference in known hardness is not large when the aging temperature is in the range of 155 to 175°C. It was confirmed that there was no significant increase. This is because the growth rate of Mg-based metastable precipitation phase (β″-Mg2Si or β′-Mg2Si) is slow under low-temperature aging conditions such as 135°C. It can be judged that this is because

Accordingly, the following heat treatment and solution heat treatment temperature was set to 535 °C, and the aging treatment temperature was set to 155 °C.

Example

AC4CH (A356.2) material (refer to Table 1 below) was applied and heat treatment, cooling and aging process were performed. A solution heat treatment step was performed at 535° C. for 6 hours, and then aging treatment was performed at 155° C. for 2.5 hours. Furthermore, X-ray inspection was performed.

AC4CH (A356.2)	standard
Si	7-10
Fe	0~0.8
Cu	2-4
Mn	0~0.5
Mg	0~0.5
Cr	0~0.2
Ni	0~0.35
An	0~1
Sn	0~0.1
Ti	0~0.2
Pb	0~0.2
Na	-
Ca	-
CD	-
Sr	~250ppm

Comparative Example 1

It was carried out in the same manner as in Example, except that the aging treatment time was controlled to be less than 2.5 hours and X-ray inspection was not performed.

Comparative Example 2

It was carried out in the same manner as in the example, but the aging treatment was performed for 4 hours and X-ray inspection was not performed.

Comparative Example 3

It was carried out in the same manner as in Example, but the aging treatment was performed for 4 hours.

Comparative Example 4

It was carried out in the same manner as in Example, except that the heat treatment time was 8 hours, and X-ray inspection was not performed.

The process conditions of Examples and Comparative Examples 1 to 4 are shown in Table 2 below.

	Heat treatment (535℃)	Aging (155℃)	X-ray inspection
Example	6h	2.5h	Yes
Comparative Example 1	6h	2.5h↓	No
Comparative Example 2	6h	4h	No
Comparative Example 3	6h	4h	Yes
Comparative Example 4	8h	4h	No

<Results and evaluation>

The mechanical properties of the specimens according to Examples and Comparative Examples 1 to 4 are shown in Table 3 below.

	No.	T/S(MPa)	Y/S(MPa)	EL(%)
Example	One	276	175	24
	2	263	159	16
	3	266	166	16
	4	280	170	19
	5	266	199	17
	6	277	200	15
Comparative Example 1	One	253	135	17
	2	239	135	9
	3	245	138	11
	4	261	139	17
	5	246	132	12
	6	237	135	9
Comparative Example 2	One	271	165	13
	2	259	156	14
	3	272	169	12
	4	267	163	14
	5	284	177	11
	6	263	171	10
Comparative Example 3	One	285	233	24
	2	303	214	16
	3	290	210	16
	4	288	216	19
	5	300	223	17
	6	291	253	15
Comparative Example 4	One	289	206	10
	2	293	211	17
	3	254	208	7
	4	287	205	11
	5	285	209	9
	6	301	212	14

Referring to Table 3, in the Example according to the present invention, as compared to Comparative Example 4, the relative strength decreased as the solution heating time was shortened, but it was confirmed that the tensile strength required as a standard was not less than 240 MPa. Although the solution heating time was decreased, the cooling time was increased to improve strength by using residual heat and to secure a relatively high elongation.

The foregoing has outlined rather broadly the features and technical advantages of the present invention so that the following claims may be better understood. Those of ordinary skill in the art to which the present invention pertains will understand that the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the claims and their equivalents should be construed as being included in the scope of the present invention.

Claims (4)

1. A temperature raising step of heating the aluminum alloy prepared using the aluminum alloy composition to 500 ~ 560 ℃;

   a solution heating step of maintaining the elevated temperature of the aluminum alloy for 5 to 7 hours;

   A cooling step of cooling the solution-ized aluminum alloy for 15 seconds to 1 minute; and

   An aging step of age hardening the cooled aluminum alloy; including, an aluminum alloy manufacturing method.
2. The method of claim 1,

   The cooling is water cooling or air cooling, characterized in that the aluminum alloy manufacturing method.
3. The method of claim 1,

   The aging step is characterized in that the age hardening of the aluminum alloy at 140 ~ 180 ℃ for 2.5 ~ 4 hours, an aluminum alloy manufacturing method.
4. An aluminum alloy manufactured according to the method for manufacturing an aluminum alloy according to claim 1 .

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