JP2593479B2 - Manufacturing method of aluminum alloy material for forming - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method capable of producing an aluminum alloy material for molding with high productivity by rolling a large ingot.

(Prior Art) In general, a process for manufacturing an aluminum sheet material from a large ingot is comprised of melting → semi-continuous casting → soaking treatment → hot rough rolling → hot finishing rolling → cold rolling → annealing → product.

By the way, the required properties of a sheet material for forming processing are various, such as mechanical properties, ear ratio, formability, streaky defects appearing in the rolling direction appearing at the time of drawing, that is, living marks, and the like. The control of the metal structure is performed every time. Also, ingots are increased in size to improve productivity, so the rolled plates are also longer, and hot rolling mills for rolling heated ingots are also capable of reciprocating rolling, for example, reversible rolls in which the direction of roll rotation changes. Type or multi-stage rolls are often used.

(Problems to be Solved by the Invention) In recent years, it has been desired to improve the quality of the above-mentioned sheet material, and thus the requirements for the above-mentioned properties have also become severe. It has become difficult to satisfy. In order to satisfy the required quality of molding materials, in addition to the conventional control of texture (control of ear ratio), uniform refinement of crystal grains (improvement of formability), etc. In addition, it is necessary to control a subtle azimuth difference between crystal grains (improvement of living mark).

Further, even if the above characteristics are satisfied, it has become difficult to maintain uniformly excellent characteristics over the entire length of the elongated plate material product. This is because, in hot rough rolling, the degree of cooling of the rolled sheet differs at various points in the longitudinal direction.

The present invention has been made in view of the above points,
The aim is to refine the metallographic structure during hot rolling, and to control the texture and precipitation to produce aluminum sheets with excellent formability. It is an object of the present invention to establish a manufacturing method for preventing quality variations in the longitudinal direction, that is, the rolling direction of each sheet material due to the miniaturized metal structure and the like.

(Means for Solving the Problems) The present inventors have conducted various studies, and have found that coarse recrystallized grains that are generated unevenly during hot rolling cause living marks. Therefore, an attempt was made to uniformly form a metal structure by fine crystals during hot rough rolling, thereby overcoming the drawbacks of the conventional method.

Usually, in the production by rolling of an aluminum sheet with severe required properties of surface quality, a recrystallized structure is obtained by hot rough rolling.
Elements such as e, Si, and Mn are precipitated before and after the completion of hot rough rolling due to a decrease in the temperature of the rolled cast sheet material.Precipitation and recrystallization of the solid-solution element compete with each other mainly in the sub-bandry, and the recrystallization grains Since the generation is suppressed, the recrystallized structure may be significantly coarsened.

Therefore, the present inventors have (1) controlled the content of the solid solution element within a predetermined range, and (2) maintained a constant temperature between the rolling pass during hot rough rolling and the next rolling pass. Doing so promotes the precipitation of the solid-solution element, and then further performs the subsequent hot rough rolling, whereby the amount of solid solution of the solid-solution element can be reduced, so that the recrystallization is performed by the subsequent hot rough rolling. It has been found that the process proceeds with little hindrance to the generation of crystal grains and that a fine crystal structure can be obtained at the end of hot rough rolling.

That is, the present invention relates to a method for producing the alloy containing 0.1 to 2.0 wt% of Mn and 0.1 to 2.0 mg of Mg.
wt%, Fe 0.7wt% or less, Si 0.5wt% or less, Cu 0.5wt
% Or less, the ingot of an aluminum alloy consisting of the balance of aluminum is subjected to hot rough rolling after soaking, and between the rolling pass after the total reduction exceeds 50% during the rolling and the next pass. Wherein the temperature of the plate to be rolled is maintained at 300 ° C. to 450 ° C. for 1 minute or more.

In the present invention, when the temperature of the plate to be rolled after the total reduction exceeds 50% is adjusted to 300 ° C. to 450 ° C., it is preferable to perform cooling or forced cooling using water or a coolant.

The operation of each component in the aluminum alloy used in the present invention is as follows.

Mn is an element that gives strength improvement, and its content is 0.
1 to 2.0 wt%. If the content is less than 0.1 wt%, the effect is not obtained. If it exceeds 2.0% by weight, giant crystals are formed and the formability is reduced.

Mg is added for the purpose of improving the strength and increasing the recrystallization speed. When the recrystallization speed is increased, it is effective in preventing living marks and suppressing variations in characteristics in the longitudinal direction. If the added amount is less than 0.1 wt%, these effects are not obtained, and if it exceeds 2 wt%, the strength becomes too high and the workability is lowered.

Fe has the effect of refining the crystal grains, but if it exceeds 0.7 wt%, giant crystals are formed and the formability is reduced.
% Or less.

Si coexists with Mn to form an Al-Mn-Si-based precipitate, which reduces the effect of Mn on inhibiting recrystallization. However, if the content exceeds 0.5 wt%, the strength is reduced.

Addition of Cu improves the strength, but if it exceeds 0.5 wt%, the formability is reduced, so the content is set to 0.5 wt% or less.

Other elements may be added as long as the effects of the present invention are not affected, for example, 0.05 wt% or less of Ti or B is added to refine the crystal grains during casting.

Now, in the present invention, in performing the hot rough rolling after the homogenizing treatment of the alloy ingot, the rolling reduction between the rolling pass after the total reduction exceeds 50% during the rolling and the next pass is performed. The temperature of the board
The temperature is maintained at 300 ° C. to 450 ° C. for 1 minute or more (hereinafter referred to as “holding process”) for the following reason.

(1) Coarse recrystallized grains in hot rough rolling cause living marks. Mn and F dissolved as a result of the holding process
e) Precipitating Si, making it difficult for competition between recrystallization and precipitation to occur, and preventing generation of coarse particles.

(2) When a large ingot is used, the length of the rolled plate, that is, the distance between the leading end and the trailing end of the rolled plate, often exceeds 100 m in several rolling passes immediately before the end of rough rolling. At this time, if the next rolling pass is reciprocating rolling, the roll enters the roll first from the rear end of the rolled plate, so that the time interval between the leading end and the rear end of the rolled plate is 3 hours.
If the recrystallization is delayed because it may last from seconds to 60 seconds or more, rolling is performed during the recrystallization, and thus a difference in structure occurs in the length direction. In the present invention, when the holding treatment at a constant temperature is performed, the recrystallization inhibiting factor is removed, so that the recrystallization is promoted, and the rolling is prevented from being performed during the recrystallization, and as a result, the characteristics in the longitudinal direction are reduced. Can be prevented.

Next, in the present invention, the reason why the holding treatment is performed after the total reduction amount exceeds 50% is that precipitation easily occurs in the presence of strain. Also, since the temperature of the slab generally decreases during hot rolling, the precipitation rate is higher after the temperature exceeds 50% than at the beginning of rolling. Therefore, the holding treatment is performed after the temperature exceeds 50% for the reason (1). It is determined as follows. On the other hand, even if the holding process is performed with a reduction amount of less than 50%, since many passes are left after that, it is not possible to prevent variations in the structure in the longitudinal direction. It is most effective to perform such a holding process immediately before performing the last pass of the hot rough rolling.

If the temperature for the holding treatment is lower than 300 ° C., the subsequent rolling temperature is lowered and the edge of the plate is cracked, and if it exceeds 450 ° C., the precipitation rate is slow and the effect of the present invention cannot be obtained. Therefore, the holding temperature of the present invention is determined to be 300 ° C. to 450 ° C., and among them, the effect of the present invention appears most at a temperature around 400 ° C. Further, if the forced cooling is performed before the holding treatment, the temperature of the entire plate becomes uniform, and the precipitation speed is reduced by cooling, so that the effect of the present invention is remarkable.

If the holding time is less than 1 minute, the precipitation is not sufficient and the reason (1) cannot be satisfied, and the structure of the plate remains non-uniform in the longitudinal direction. Therefore, the reason (2) cannot be satisfied. Therefore, the holding time is determined to be 1 minute or more. When held for more than one minute, there is no variation in the structure. This is because, in the case of the alloy component of the present invention, the recrystallization proceeds in the hot rough rolling until about one minute after the rolling, and after that, the competition with the precipitation stops the progress of the recrystallization. Therefore, from the reason of the above (2), it is sufficient to hold for 1 minute or more. On the other hand, from the reason (1), if the holding time is longer than 1 minute, the longer the holding time, the more the amount of precipitation increases. Therefore, it is desirable that the holding time is long. .

In the method of the present invention, steps other than the above (homogenization treatment,
Hot rolling start temperature, end temperature, cold rolling, annealing conditions, etc.) may be the same as the conventional conditions.

(Examples) Next, the present invention will be described in more detail based on examples.

Example Ingots having the components and sizes shown in Table 1 were chamfered by 10 mm on each side and homogenized at 600 ° C. for 6 hours, and hot roughed to a thickness of 20 mm by hot rough rolling shown in Table 2. Rolling was performed, followed by hot finish rolling to a thickness of 2.5 mm. The obtained hot coil was annealed at 360 ° C. for 2 hours, cold rolled to 0.32 mm, and annealed at 130 ° C. for 2 hours. The obtained cold-rolled sheet was drawn with a blank diameter of 61 mmφ and a shoulder radius of 4.5 mm, and the ear ratio and generation of living marks were evaluated.

The description in Table 2 is as follows. In the ingot size, t represents the thickness, l represents the length, and in the column of holding conditions, the numerical value represented by mmt represents the plate thickness,
Cooling is a cooling method that keeps the temperature of the rolled sheet at the holding temperature. Cooling is no special cooling, and cooling is forced cooling with water or a coolant (water + rolling oil emulsion). . Taking No. 1 as an example, start rolling at 500 ° C, and after several rolling passes, when the plate thickness reaches 40 mm, allow it to cool to 400 ° C before moving on to the next rolling pass. After holding for 120 seconds, the next rolling was performed for the first time, and the rough rolling was finally completed at 370 ° C.

Table 3 shows the evaluation results. In the case where the holding process was not performed, a living mark was generated, the ear ratio was high, and the values varied.

(Effect of the Invention) According to the method of the present invention, an aluminum alloy sheet having excellent properties can be obtained. Moreover, according to the method of the present invention, a long plate can be manufactured from a large ingot with increased productivity, and uniform quality can be maintained in the longitudinal direction of the long plate, so that the obtained aluminum alloy plate can be used for cambodies, closures, Equipment,
It is suitable as a molding material for automobile body sheets and the like.

Claims (2)

(57) [Claims] (1) Mn 0.1-2.0 wt%, Mg 0.1-2.0 wt%, Fe
0.7wt% or less, Si 0.5wt% or less, Cu 0.5wt% or less,
In performing the hot rough rolling after soaking the aluminum alloy ingot consisting of the remaining aluminum, during the rolling, between the rolling pass after the total reduction exceeds 50% and the next pass,
A method for producing an aluminum alloy material for forming, characterized in that the temperature of a plate to be rolled is maintained at 300 ° C to 450 ° C for 1 minute or more. 2. The method according to claim 1, wherein the temperature of the plate to be rolled is maintained at 300 ° C. to 450 ° C. for 1 minute or more, and then cooling is performed by cooling or forced cooling using water or a coolant. A method for producing the aluminum alloy material for molding according to the above.