JP2002321009A - Extrusion method and extruded product manufactured by the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extrusion method in which productivity is improved and an extruded product excellent in quality and material characteristics is stably obtainable when manufacturing the product by extruding a metal billet, and such an extruded product. SOLUTION: The method is to control the extruding speed after accelerating the billet extruding speed to a given speed when extruding the heated billet so as to prevent generation of a defective product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing an extruded material by extruding a metal billet, and more particularly, to stably providing an extruded material of good quality by controlling the extruding speed of the billet. The present invention relates to an extruding method which can be performed and an extruded material produced by the method.

[0002]

2. Description of the Related Art Extrusion of metal products by extrusion involves manufacturing a product having a cross section corresponding to the shape of a die by placing a heated billet in a container and extruding the billet through a die with a ram. It is.

In this extrusion process, the product extrusion speed (billet extrusion speed) is an important factor that determines the quality of the product. When the extrusion speed is increased, a large amount of processing heat is generated, and the processing heat becomes larger than the heat taken by the tool, and the temperature of the billet rises to cause baking cracks. On the other hand, if the extrusion speed is reduced, it takes too much time to extrude the billet, which is not suitable for actual operation, and the strength of the product may be insufficient. Therefore, various techniques have been proposed focusing on the relationship between the billet extrusion speed and the product quality.

For example, JP-A-5-104132 and JP-A-6-104132
No. 277750 discloses a technique for measuring the temperature of an extruded product using a radiation thermometer and controlling the extrusion speed so that the temperature falls within a certain range to provide a product without surface baking. Have been. However, these techniques do not consider changes in the product shape during extrusion and changes in the composition of the extruded material, and thus have caused problems such as a reduction in material strength and the occurrence of cracks during welding.

In these techniques, it is difficult in actual operation to feed back the measured temperature results within one billet extrusion time (the time required for completely extruding one billet). I understood that. In other words, in these techniques, the next billet extruding speed can be made lower than that in the previous pass, which further increases the time required for extruding the billet. Therefore, productivity could not be improved.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is an object of the present invention to improve productivity and improve product quality and material properties in extrusion processing. An object of the present invention is to provide an extrusion method capable of stably obtaining an excellent extruded product, and to provide such an extruded material.

[0007]

The extrusion processing method of the present invention which can solve the above-mentioned problem is as follows. When extruding a heated billet, the extrusion speed of the billet is accelerated to a predetermined speed. The gist is that the extrusion speed is controlled so as not to cause a product defect, and the extrusion process is performed.If the extrusion speed is controlled in a deceleration direction or the extrusion speed is reduced at a constant rate, a more excellent effect is obtained. Obtainable.

[0008] In the extrusion method of the present invention, a strain rate range that can be controlled to a crystal grain size that does not cause a product defect is determined in advance based on the relationship between the strain rate of the billet during extrusion and the recrystallization state. Extrusion is preferably performed within the speed range. In this case, it is more preferable to set the extrusion speed pattern in consideration of the time required from the start of extrusion to the end of extrusion.

In the extrusion method of the present invention, a surface temperature range in which surface seizure does not occur is determined in advance based on a relationship between a change in the surface temperature of the billet or the product and surface seizure. It is also preferable to perform the extrusion process in this case. In this case, it is more preferable to set the extrusion speed pattern in consideration of the time required from the start of the extrusion to the end of the extrusion.

Further, according to the extrusion method of the present invention, a strain rate range that can be controlled to a crystal grain size that does not cause a product defect is determined in advance based on the relationship between the strain rate of the billet during the extrusion and the recrystallization state. Alternatively, based on the relationship between the change in the surface temperature of the product and the surface seizure, a surface temperature range where surface seizure does not occur is determined in advance, and extrusion is performed so as to satisfy the strain rate range and the surface temperature range. In this case, in consideration of the time required from the start of extrusion to the end of extrusion, an extrusion speed pattern of a billet satisfying the strain rate range and an extrusion speed pattern of a billet satisfying the surface temperature range are determined. Further, it is more preferable to perform the extrusion processing using a condition of lower speed from both of these patterns.

In the extrusion method of the present invention, a plurality of billet heating temperatures are set in advance, and the time required from the start of extrusion to the end of extrusion is determined from the extrusion speed patterns corresponding to each of the heating temperatures. Extrusion can be performed by selecting a short one as the optimal extrusion speed pattern, or by heating the billet using a billet heating facility that can provide a heating temperature gradient at the tip and end of the billet. In doing so, a plurality of heating temperatures at the tip of the billet are set in advance, and a billet temperature gradient is calculated for each of the heating temperatures so that the heat energy applied to the billet can be extruded with the minimum necessary, and the calculated heating temperature is calculated. The extrusion speed pattern is determined for each of the gradients, and the time required from the start of extrusion to the end of extrusion is determined in the determined extrusion speed pattern. Select the one is short as the optimum extrusion speed pattern, it is preferable to extrusion by the optimum extrusion speed pattern selected.

The extruded material of the present invention produced by the above-described extrusion method is an extruded material made of an aluminum alloy, and the extruded material has a surface recrystallization thickness throughout the length of the extruded material.
It has a feature of being 100 μm or less.

The extruded material of the present invention manufactured by the above-mentioned extrusion method is an extruded material made of an aluminum alloy and has a variation in tensile strength and proof stress of not more than 20 N / mm ² over the entire length of the extruded material. It has the feature of.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have studied from various angles the cause of the deterioration of the product characteristics of an extruded material. As a result, it was found that the material properties of the extruded material were related to the change in the strain rate applied to the billet during the extrusion process. When the strain rate exceeded a certain value, the crystal grains became coarse when recrystallizing (hereinafter, referred to as "May be referred to as" defective recrystallization "), thereby deteriorating the material properties. As a result of further studies by the present inventors, it was found that an extruded material exhibiting good properties by reducing recrystallization defects can be obtained by appropriately controlling the billet extrusion speed during extrusion, and completed the present invention. did.

On the other hand, based on the finding that the cause of the change in the product temperature immediately after extrusion is related to the amount of heat generated during the extrusion, the present inventors have further studied and found that:
By controlling the billet extrusion speed in consideration of the billet temperature at the time of inserting the container (initial billet temperature) and the calorific value generated during extrusion, it was found that the occurrence of seizure failure can be reduced. .

Hereinafter, the configuration, operation and effect of the present invention will be described in detail.

According to the extrusion method of the present invention, when extruding a heated billet, the extruding speed of the billet is accelerated to a predetermined speed, and then the extruding speed is controlled so that a product defect does not occur. is there. Here, the "predetermined speed" is a speed at which billet extrusion can be stably performed, and is generally called "initial speed".

In the conventional extrusion processing method, the billet is extruded at a constant speed so as to maintain this initial speed, but in the extrusion processing method of the present invention, the extrusion speed of the billet after reaching the initial speed does not cause a product defect. It is controlled by range and has the largest point here. The points of the present invention will be described with reference to the drawings.

FIG. 1 is a graph showing the relationship between the time required to extrude the billet to the end and the extrusion speed of the billet. FIG. 1A shows a conventional example. In the conventional extrusion processing method, after the extrusion speed reaches the initial speed, operation is performed so as to maintain the initial speed. However, in the extrusion method of the present invention,
After the extrusion speed reaches the initial speed, the extrusion speed is controlled (changed). At this time, the control of the extrusion speed needs to be performed in a range in which no product defect occurs, as described later.

In the present invention, the extrusion speed after reaching the initial speed is preferably controlled in a deceleration direction. For example, Figure 1
After reaching the initial speed, as shown in (b-1), a pattern for controlling the speed in the order of "deceleration → constant speed → deceleration" or in the deceleration direction as shown in Fig. 1 (b-2) Controlling the extrusion speed in this manner is exemplified. The most preferred control mode of the present invention is shown in FIG.
As in 1 (c), the extrusion speed of the billet that has reached the initial speed is reduced at a constant rate. The reason will be described later.

Here, the control form of the extrusion speed shown in FIG. 1C, which is an example of the present invention, will be described in detail. Figure
In the control pattern of the extrusion speed shown in FIG. 1 (c), the time required for extruding the billet can be shortened as compared with the related art. In other words, as shown in FIG. 2 (a), the initial speed is
If you decelerate after making it larger than "c", the trapezoid "Irohohe" and the square "Ihanit" formed on the graph
Area indicates the length of the extruded billet, so if the trapezoid "Irohohe" and the square "Ihanit" are equal, the same length billet is extruded, and the time required for extrusion is "F". From "to". Therefore, as shown in FIG. 2 (b), the acceleration until reaching the initial speed is made larger than before, but if the initial speed reached is about the same as the conventional one, the time required for billet extrusion becomes longer than before. However, as shown in FIG. 2 (c), if the acceleration before reaching the initial speed is made larger than before, and if the initial speed is set to be larger than before, then the speed is reduced, so that the extrusion time can be further reduced than in FIG. 2 (a). is there.

In the present invention, "there is no product failure" means that no recrystallization failure or surface seizure occurs.
In the present invention, an extrusion speed range in which product defects do not occur is determined in advance, and the extrusion speed is controlled within that range. Hereinafter, the relationship between the product defect and the billet extrusion speed will be described in detail. Here, the control of the extrusion speed will be described using a case where the extrusion speed is reduced at a fixed rate after reaching a predetermined speed (initial speed). .

(1) Poor recrystallization and extrusion speed of billet
As related above, causes recrystallization defect is in the strain rate at the time of the billet extrusion, exceeds a certain value the strain rate, the recrystallized grains become coarse, material strength may decrease, during welding Cracks are generated from the coarse portion of the recrystallized grains, thereby deteriorating the material properties. Therefore, in the present invention, a strain rate range that can be controlled to a crystal grain size that does not cause recrystallization failure is determined in advance based on the relationship between the strain rate of the billet during extrusion and the recrystallization state (hereinafter referred to as “strain rate prediction model”). In some cases, the extrusion speed is controlled within the strain rate range to carry out extrusion.

The features of the present invention will be described with reference to FIG. Figure 3
(A-1) and (b-1) are conventional examples, and (a-2) and (b-2)
Is an example of the present invention. As shown in the line in Fig. 3 (a-1),
After the billet extrusion speed reaches the initial speed, if the initial speed is maintained and the billet is extruded to the end portion, the strain rate increases as the extrusion process proceeds (as the billet end portion is approached). If the strain rate exceeds a certain value at the end of the product, the recrystallized grains become coarse and the material properties deteriorate [line (b-1) in FIG. 3]. In order to solve this problem by the conventional method of maintaining the initial speed, the initial speed is set as small as possible, as shown in the line of FIG. A method is conceivable. However, in this case, it takes too much time to extrude the billet, and the productivity becomes very poor.

On the other hand, as shown in FIG. 3 (a-2), in the method of the present invention, the extrusion speed is accelerated with a larger acceleration until the extrusion speed reaches the initial speed, and the initial speed is set to be larger than the conventional speed. Therefore, although the increase in the strain rate in the initial stage is large [Fig. 3 (b-2)], after the initial speed is reached, the extrusion speed is reduced at a constant rate. Do not exceed.
Therefore, it is possible to obtain an extruded material having uniform characteristics in which coarse recrystallized grains are not generated from the leading end to the trailing end of the product, and to extrude the billet in a shorter time than before.

In the present invention, the extrusion speed pattern that does not cause recrystallization defects is calculated as follows. In the metal flow of the billet in the forward extrusion, the deformation area is expanded as the billet becomes shorter. The present inventors have clarified through experiments that the boundary line d (t) of the deformation region can be expressed by the following equation. Here, L (t) indicates the billet length at time t,
R indicates the extrusion ratio. d (t) = f (L (t), R)

When the extrusion is performed so as to maintain the initial speed after reaching the initial speed as in the prior art, the deformation area near the extrusion opening expands toward the outer periphery of the billet as the billet becomes shorter. Therefore, the amount of strain applied to the billet increases, and the strain rate increases. The maximum strain rate e (t) near the extrusion port is
When the ram speed at time t is V _ram (t), it is expressed by the following equation. e (t) = g (L (t), R, V _ram (t)) When this inverse function is calculated, the following expression is obtained, and the control pattern of the extrusion speed can be calculated. V _ram (t) = g ^-1 (L (t), R, e (t)) (1)

That is, when a strain rate (constant) at which recrystallization failure does not occur is substituted for e (t), an extrusion rate pattern that can be extruded over the entire length of the product while keeping the strain rate constant is obtained. It is. That is, assuming that the maximum strain rate e (t) near the extrusion port and the extrusion ratio R are constant, the above equation (1) indicates that the pattern of the extrusion processing speed is the billet length L.
This shows that there is a relationship with the change in (t). this is,
In the early stage of extrusion, the billet is long and the extrusion speed is high, but in the end of extrusion, the billet is short, which is consistent with the low extrusion speed.

According to the above method, a plurality of billet extrusion speed patterns can be determined within a strain rate range which can be controlled to a crystal grain size that does not cause a product defect. The productivity can be further improved by setting the extrusion speed pattern in consideration of the time required. "Consideration"
This means that when setting the extrusion speed pattern, one with some time margin is set. That is, in order to improve the productivity most, it is sufficient to select the extrusion time pattern from the above extrusion speed patterns, the extrusion time being the shortest, but the extrusion time is slightly longer in consideration of operational safety. In some cases, the extrusion speed pattern is set in consideration of time.

(2) Surface Seizure and Billet Extrusion Speed
When the temperature of the billet in the container or in the vicinity of the die outlet exceeds a certain temperature, surface seizure occurs, which causes seizure failure on the product surface, as described above. Conventionally, this problem has been dealt with by measuring the surface temperature of the product immediately after extrusion using a non-contact thermometer, and setting the initial speed so that this temperature does not exceed a certain value and performing extrusion. Was. However, in this method, no consideration was given to changes in surface temperature due to differences in the shape and composition of the extruded material, so that if the production conditions were different, the operating conditions had to be considered from the beginning each time.

According to the research conducted by the present inventors, extrusion processing is performed in consideration of the billet temperature at the time of insertion into a container (initial billet temperature) and the calorific value generated during extrusion processing. There is no need to reconsider the operating conditions due to differences in the shape of the product, and even if the composition of the billet is changed, the amount of heat generated during processing can be easily determined as long as the deformation resistance of the material having the composition at a high temperature is known. Since it can be estimated, it was found that it was not necessary to measure the product surface immediately after extrusion each time as described above and to carry out a troublesome operation such as reconsidering the operating conditions. Therefore, in the present invention, a surface temperature range in which surface seizure does not occur is determined in advance based on the relationship between the change in the surface temperature of the billet or the product and the surface seizure (hereinafter, referred to as a “product temperature prediction model”).
Extruded within this surface temperature range.

The features of the present invention will be described with reference to FIG. Figure 4
As shown in the line (a-1), after the billet extrusion speed reaches the initial speed, the billet is extruded at a constant speed. Since heat is generated, the surface temperature of the product increases with this, and the surface temperature of the product particularly exceeds the temperature at which surface seizure occurs at the end portion of the product. Therefore, in order to solve this problem by the conventional method, it is conceivable to extrude the product by setting the initial velocity to a small value as shown in the line of FIG. 4 (a-1).
1) Line] In this case, it takes time to extrude the billet, and the productivity is very poor.

On the other hand, as shown in FIG. 4 (a-2), in the method of the present invention, the extrusion speed is accelerated at a larger acceleration than before until the extrusion speed reaches the initial speed, and the initial speed is set to be larger than the conventional one. The rate of increase of the product surface temperature at each stage becomes very large [Fig. 4 (b-2)]. However, after reaching the initial speed, the extrusion speed is reduced at a constant rate, so that the product surface temperature does not exceed the expected value. Therefore, extruded material with good product quality can be obtained from the front end to the end of the product,
It can be extruded in a shorter time than before.

In the present invention, the billet or product surface temperature is calculated as follows. Table heat quantity Q _b with the billet during the container insertion, the machining amount of heat generated by processing the [Delta] q _1, the heat removal amount from the billet to the container and [Delta] q _2, the amount of heat Q _p with the extruded material, by the following formula from the heat balance Is done. Q _p = Q _b + Δq ₁ −Δq ₂

When the deformation resistance is Y and the extrusion ratio is R, the calorific value of processing Δq ₁ is the load Y × ln required for deformation.
It is generally known that it is proportional to (R). And
Taking into account that the deformation resistance Y has a speed dependency, the processing heat value Δq ₁ is expressed by the following equation. Δq ₁ = f ₁ (V _ram (t), R, Y)

If the container temperature is T _c and the billet temperature is T _b (l), the heat removal Δq ₂ from the billet to the container is represented by the following equation. Note that the billet temperature is represented by a function of the length 1 because the longitudinal temperature distribution (temperature gradient) of the billet is taken into account. Δq ₂ = f ₂ (T _c , T _b (l))

[0037] Here, the heat quantity Q _b with the billet, a function of billet temperature distribution T _b (l), In addition, since the function of the heat Q _p may similarly billet temperature distribution T _p (l) with the extruded material , Q _b, and Q _{p, respectively,} as Q _b = f ₃ (T
_b (l)), When _{Q p = f 4 (T p} (l)), Q p = Q b + Δq 1 -Δq 2 ⇔ f 4 (T p (l)) = f 3 (T b (l) ) + F ₁ (V _ram (t), R, Y) −f ₂ (T _c , T _b (l)). By transforming this, T _p (l) is expressed by the following equation. T _p (l) = f ₅ (T _b (l), V _ram (t), R, Y, T
_c )

Therefore, when this inverse function is obtained, the extrusion speed V
_ram (t) becomes V _ram (t) = f ₅ ^-1 (T _p (l), T _b (l), R, Y, T _c ) (2) T that satisfies the requirements of the present invention
_By substituting _p (l) as a constant, it is possible to calculate the extrusion speed (ram speed) that can keep the product surface temperature immediately after extrusion constant.

As described above, according to the present invention, it is possible to calculate a plurality of extrusion speed patterns within a surface temperature range where surface seizure does not occur, but it is necessary to consider the time required from the start to the end of extrusion. The productivity can be further improved by setting the extrusion speed pattern. Note that "consideration" means that when setting the extrusion speed pattern, one having some time margin is set. That is, to maximize productivity,
From the above extrusion speed patterns, it is sufficient to select the one that requires the shortest time for extrusion.However, the extrusion time may be slightly longer in consideration of safety in operation. The “examination” is used to set the extrusion speed pattern.

Further, according to the present invention, a strain rate range which can be controlled to a crystal grain size which does not cause a product defect is determined in advance based on the relationship between the strain rate of the billet during extrusion and the recrystallization state, Based on the relationship between the change in temperature and the surface seizure, a surface temperature range where surface seizure does not occur is determined in advance, and the extrusion speed pattern is set so as to extrude so as to satisfy the strain rate range and the surface temperature range. If it is set, it is possible to carry out the extrusion process so that recrystallization failure does not occur and surface seizure does not occur.

Also in this case, taking into account the time required from the start of extrusion to the end of extrusion, the extrusion speed pattern of the billet that satisfies the above strain rate range and the extrusion speed of the billet that satisfies the above surface temperature range are also considered. Find a pattern,
It is preferable to extrude using low-speed conditions of both these patterns. That is, since the extrusion method of the present invention satisfies both the strain rate range and the surface speed range, it is possible to manufacture a product that does not cause product defects such as recrystallization defects and seizure defects, and to extrude. Since the required time is taken into consideration, productivity can be improved.

The present inventors have also studied the heating temperature at which billets can be extruded. If the shape (product shape) of the extruded material is different, the frictional resistance during the extrusion process changes, so that the load required for extruding the billet also changes, and the optimum extrusion speed changes accordingly. In the present invention,
Let Pi be the initial load required for billet extrusion.
Pi can be calculated by the following equation (hereinafter sometimes referred to as “load estimation model”). Pi = Pf + Pd (3) Here, Pf is a drag force against the friction between the container and the billet during extrusion, and it is generally known that Pf is represented by the following equation. Here, Y is the deformation resistance, μ is the coefficient of friction, l
a indicates the initial length of the billet, and da indicates the container radius. Pf = Y × 4 × μ × la / da

Further, Pd shows a drag required for deformation,
When the shape of the product becomes complicated, it becomes difficult to calculate Pd. Therefore, in the present invention, Pd is estimated as follows. Pd = P1 + P2 P1 indicates the load required to extrude the billet into a solid round bar having the same cross-sectional area as the product (extruded material), where Y represents the average deformation resistance and R represents the extrusion ratio, and is expressed by the following equation. Is known to be. P1 = Y × ln (R) P2 is a load required for extrusion deformation to a product of a desired shape having the same cross-sectional area as that of the solid round bar. Is estimated by the following equation using the outer peripheral length L2 and the deformation resistance Y. P2 = g (L1, L2, Y)

Therefore, when the billet is extruded, if the relationship shown in the following equation (4) is satisfied, a product having a desired shape can be extruded with the load Pi. Pi ≧ Pf + Pd⇔Pi ≧ Y × 4 × μ × la / da + P1 + P2⇔Pi ≧ Y × 4 × μ × la / da + Y × ln (R) + g (L1, L2, Y) (4)

In other words, when the maximum extrusion load of the billet extrusion processing equipment is substituted for Pi in the above equation (4), if the extrusion conditions are set so as to satisfy the above equation (4), the billet can be extruded. Can be calculated.

In the present invention, when setting the extrusion speed pattern in consideration of the strain speed range and / or the surface temperature range obtained in advance, a plurality of billet heating temperatures are set in advance, and the billet heating temperatures are respectively set. If the time required from the start of extrusion to the end of extrusion is selected as the optimum extrusion speed pattern from among the extrusion speed patterns and extrusion is performed, the productivity is further improved.

Further, according to the present invention, when the billet is heated before being inserted into the container, the billet is heated by using a billet heating facility capable of imparting a heating temperature gradient at the leading end and the trailing end of the billet. There is. In this case, when performing the extrusion, a plurality of heating temperatures of the billet tip are set in advance, and the maximum temperature gradient at which the extrusion can be performed with the maximum extrusion load determined by the equipment used for the extrusion for each of the heating temperatures is calculated. Then, for each of the calculated temperature gradients, the strain rate range and / or
Or determine the extrusion speed pattern considering the surface temperature range,
Among the obtained extrusion speed patterns, the one that requires the shortest time from the start of extrusion to the end of extrusion is selected as the optimal extrusion speed pattern, and extrusion is performed according to the selected optimal extrusion speed pattern. The flow of determining the extrusion speed pattern in the extrusion processing method of the present invention will be specifically described with reference to a flowchart.

The flowchart shown in FIG. 5 is an example in which the extrusion speed pattern is set in consideration of the load estimation model, the strain speed range, and the surface temperature range. A device capable of imparting a temperature gradient is used. The temperature of the billet tip (die side) is T _bh , and the billet end (ram side)
_Is T _bt .

First, in [Step 1], the temperature (T _bh0 ) of the billet tip is set. Usually, this temperature is a temperature at which the billet tip can be heated to the maximum in the billet heating facility.

Next, in [Step 2] to [Step 3], the heating temperature gradient of the entire billet is calculated based on the heating temperature of the billet tip using the load estimation model.

In step 2, _assuming that the temperature of the billet tip calculated at the i-th time is T _bhi , the heating temperature of the billet tip is expressed by the following equation. _Tbhi = _{Tbh (i-1)-[ Delta]} T Here, [Delta] T represents the width of the temperature setting when heating the billet (the width of the heating temperature setting), and is set by the capacity of the billet heating equipment.

Next, in Step 3, based on the calculated T _bhi, to calculate the heating temperature gradient across the billet, calculates the temperature T _bti billet termination.

The heating temperature gradient is calculated using T _bhi obtained in [Step 2] and the above equation (3). In other words, in the extrusion process, when the temperature of the billet tip is T _bhi ,
Must be able to extrude. Therefore, the relationship between the heating temperature gradient of the entire billet and the load required for extrusion processing will be examined using the above equation (3). Since the average deformation resistance Y of the billet in the load estimation model depends on the temperature of the billet, substituting the maximum capacity (maximum load) of the billet extruder into Pi determines whether or not extrusion molding can be performed at the billet temperature. Can be. And Pi ≧
If Y × L + Pd, it can be extruded. here,
Since the temperature T _bhi of the billet tip is calculated, P from the value of the temperature T _bhi the average deformation resistance Y of the billet tip
Temperature T at billet end that satisfies i ≧ Y × L + Pd
_bti can be calculated.

Next, in Step 4, by comparing the temperature T _bti temperature T _bhi a billet end portion of the billet tip, case classification in the case of T _bhi ≧ T _bti, in the case of T _bhi <T _bti do.

If T _bhi ≧ T _bti , the process proceeds to the direction of YES in FIG. 5, that is, to [Step 5]. [Step 5]
Using the above equation (2) calculated based on the product prediction model, a billet extruding speed pattern V _1i within a surface temperature range where seizure failure does not occur is calculated.

Next, in [Step 6], using the above equation (1) calculated based on the above strain rate prediction model, the billet extrusion speed pattern V _2i within the strain rate range where recrystallization failure does not occur. Is calculated. Note that the order of [Step 5] and [Step 6] may be reversed.

Next, in [Step 7], the above V _1i
And V _2i are combined to calculate an optimum extrusion speed pattern.
When the extrusion speed patterns of V _1i and V _2i are different, the extrusion speed patterns are determined so that the two patterns are superimposed so as to satisfy the low speed condition. The optimum extrusion speed pattern in this case is _defined as V _3i .

Next, in [Step 8], the cycle time _Cti required for extruding the billet using the optimum extrusion speed pattern is calculated. After calculating the cycle time _Cti , the process returns to [Step 2] and proceeds to the next calculation.

On the other hand, in the above [Step 4], T _bhi <T
_In the case of _bti , proceed to the direction of NO, that is, [Step 9],
Choose C _tn capable extruded by the time the shortest among the cycle time C _t1 -C _ti calculated so far. The extrusion speed pattern V _{3n in} this case is an extrusion speed pattern that satisfies the requirements of the present invention, and T _bhn and T _{btn in} this case are the optimum patterns of the billet heating temperature gradient.

When the billet is extruded under these operating conditions, a good-quality product can be produced without causing baking defects or recrystallization defects. Further, since the cycle time C _tn finally selected in the above flowchart is the shortest time required for the extrusion, the productivity can be improved.

The extrusion method of the present invention can be employed when a metal billet is extruded to produce a product, and the metal species is not particularly limited. For example, copper-based materials such as pure copper, brass, and bronze, and special materials such as magnesium and titanium can be used. It has been found that the present invention preferably employs the present invention particularly when extruding an aluminum alloy billet.

The extruded product made of an aluminum alloy produced by the extrusion method of the present invention has a feature that the surface recrystallized thickness of the extruded material is 100 μm or less over the entire length of the extruded material. Further, the extruded material made of an aluminum alloy manufactured by employing the extrusion method of the present invention has a variation in tensile strength and proof stress of 20 N / m over the entire length of the extruded material.
It exhibits the characteristic that m is ² or less.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following Examples are not intended to limit the present invention, and any change in the design based on the above and following points is not limited to the present invention. Are included within the technical scope of

[0064]

Example 1 An aluminum alloy billet corresponding to JIS 7N01 shown in Table 1 was uniformly heated to 480 ° C. using a Granco furnace, then inserted into a container and extruded. The shape of the container is φ200,
The shape of the billet is φ198 × L550.

[0065]

[Table 1]

In the example of the present invention, as shown by the dotted line (variable speed extrusion) in FIG. 6A, the initial speed of the extrusion speed is set to 18.0 m / min, and then the billet is extruded (as the product length becomes shorter). Extrusion was performed at a reduced extrusion rate at a constant rate. On the other hand, in the comparative example, as shown by the solid line (constant speed extrusion) in FIG. 6A, after the initial speed of the extrusion speed reached 12.0 m / min, the extruded material was extruded to the billet terminal end while maintaining this speed. The physical properties of the extruded product are the variation in tensile strength (N / mm ² ), 0.2%
Evaluation was made based on the variation in proof stress (N / mm ² ) and the recrystallization thickness (μm).

<Variation in tensile strength and variation in 0.2% proof stress> After the extruded material was heat-treated under the conditions of JIS H001 (T5 condition), a test piece indicated in JIS H4100 was prepared, and the tensile strength and 0.2% proof stress at room temperature were prepared. Was measured. Test pieces were sampled at around 2 m, 10 m, and 18 m from the tip of the extruded material.
The variation in the tensile strength and the 0.2% proof stress was expressed as a difference between the tensile strength and the 0.2% proof stress of a test piece taken from each position, based on a material near 2 m from the tip of the extruded material.
Fig. 6 (b) shows the results of variation in tensile strength, and Fig. 6 (c)
The results of the 0.2% proof stress variation are shown in FIG.

<Recrystallized thickness> Around 2 m from the tip of the extruded material,
A cross section perpendicular to the extrusion direction at a position around 10 m or around 18 m was used as a test piece. After etching this test piece, it was observed using an optical microscope. The results are shown in FIG.

The following can be considered from FIGS. 6 (b) to 6 (d).

When the extrusion method of the present invention is employed, an excellent extruded material having a variation in tensile strength and proof stress of not more than 20 N / mm ² over the entire length of the extruded material can be obtained. In addition, the surface recrystallization thickness is 100
μm or less.

On the other hand, in the conventional extrusion method as a comparative example,
It can be seen that the physical properties decrease toward the end of the extruded material. That is, when comparing the product front end portion and the terminal portion, the variation of tensile strength of about 33N / mm ^2, and the also was approximately 38N / mm ² variation of 0.2% proof stress. Also, the recrystallization thickness exceeds 100 μm at the end of the product. Therefore, if the extruded material is extruded to the end of the billet while maintaining the initial speed as in the conventional art, a uniform product cannot be obtained over the entire length of the extruded material. As a result, the end of the extruded material cannot be used as a product, and resources are wasted.

Example 2 When the billet is pre-heated, the case where the billet is heated uniformly and the case where the billet is heated with a temperature gradient are compared.

<Homogeneously Heated> A billet having substantially the same components as the aluminum alloy billet shown in Example 1 was heated to a target temperature of 500 ° C. using a Granco furnace and extruded. The Granco furnace is a furnace in which a billet is directly heated by a burner, and the heating temperature (° C.) near the tip of the billet, around 280 mm, and around 550 mm after heating was measured using a contact thermometer. The heating temperature with respect to the longitudinal position of the billet is shown by a solid line (uniform heating) in FIG.

<Applying Temperature Gradient> A billet having substantially the same components as the aluminum alloy billet shown in Example 1 was uniformly heated to a target temperature of 460 ° C. using a Granco furnace. Thereafter, the tip of the billet was reheated to 500 ° C. using an induction heater (induction heating device). The heating temperature (° C.) near the tip of the billet, around 280 mm, and around 550 mm after heating was measured using a contact thermometer. The heating temperature for the longitudinal position of the billet is shown by a dotted line (taper heating) in FIG.

The billet heated by uniform heating or by applying a temperature gradient was accelerated to an initial speed of 12 m / min, and then the extrusion speed was reduced at a constant rate. The final speed is 8 m / min.

In the same manner as in Example 1, the variation in the tensile strength, the variation in the 0.2% proof stress, and the recrystallization thickness of the extruded material were measured.
The results are shown in FIGS. 7 (b) to 7 (c).

As is clear from FIGS. 7 (b) to 7 (c), the extrusion speed can be controlled by controlling the extrusion speed regardless of whether the billet is extruded after being uniformly heated or extruded after heating the billet with a temperature gradient. When extruded, an extruded material excellent in all physical properties can be obtained. In particular, when the billet is heated to give a temperature gradient and then extruded, it is understood that a further effect is exhibited. That is, the variation in tensile strength between the extruded material front end portion and the extruded material end portion is within about 6 N / mm ^2, and the variation in 0.2% proof stress is also within about 5 N / mm ² . Recrystallization thickness is also about 10
within μm.

[0078]

According to the present invention, there is provided an extrusion method capable of stably obtaining a product having good product quality and excellent material properties while improving productivity as compared with the conventional one. Was completed. When this processing method was employed, an extruded material free from defective products such as poor seizure and poor recrystallization could be provided from the front end to the rear end of the product.

[Brief description of the drawings]

FIG. 1 is a graph illustrating a billet extrusion speed pattern.

FIG. 2 is a graph illustrating an extrusion speed pattern of a billet according to the present invention.

FIG. 3 is a graph illustrating a billet extrusion speed pattern.

FIG. 4 is a graph illustrating a billet extrusion speed pattern.

FIG. 5 is a flowchart showing a flow for obtaining an optimum extrusion speed pattern satisfying the requirements of the present invention.

FIG. 6 is a graph according to an example.

FIG. 7 is a graph according to an example.

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Claims (13)

[Claims] The present invention is characterized in that, when extruding a heated billet, after extruding the billet to a predetermined speed, the extruding speed is controlled so as not to cause a product defect. Extrusion processing method. 2. The extrusion method according to claim 1, wherein the extrusion speed is controlled in a deceleration direction. 3. The extrusion processing method according to claim 2, wherein the extrusion speed is reduced at a constant rate. 4. A strain rate range that can be controlled to a crystal grain size that does not cause a product defect is determined in advance based on the relationship between the strain rate of the billet during the extrusion process and the recrystallization state, and the extrusion process is performed within the strain rate range. The extrusion processing method according to claim 1. 5. An extrusion speed pattern is set in consideration of a time required from the start of extrusion to the end of extrusion.
Extrusion processing method described in 1. 6. A surface temperature range in which surface seizure does not occur based on a relationship between a change in surface temperature of a billet or a product and surface seizure, and extrusion is performed within the surface temperature range. 4. The extrusion method according to any one of items 1 to 3. 7. The extrusion speed pattern is set in consideration of the time required from the start of extrusion to the end of extrusion.
Extrusion processing method described in 1. 8. Based on the relationship between the strain rate of the billet during extrusion and the state of recrystallization, a strain rate range that can be controlled to a crystal grain size that does not cause a product defect is determined in advance, and a change in the surface temperature of the billet or the product is determined. The surface temperature range in which surface seizure does not occur is determined in advance based on the relationship of surface seizure, and extrusion is performed so as to satisfy the strain rate range and the surface temperature range. Extrusion processing method as described. 9. A billet extrusion speed pattern that satisfies the strain rate range and a billet extrusion speed pattern that satisfies the surface temperature range, taking into account the time required from the start of extrusion to the end of extrusion. The extrusion processing method according to claim 8, wherein the extrusion processing is performed using a lower speed condition among the two patterns. 10. The method according to claim 5, wherein a plurality of billet heating temperatures are set in advance, and from the extrusion speed pattern corresponding to each of the heating temperatures, from the start of extrusion to the end of extrusion. An extrusion method in which the shortest time is selected as the optimum extrusion speed pattern and extrusion is performed. 11. After the billet is heated using a billet heating facility capable of imparting a heating temperature gradient at the front end and the end of the billet, a plurality of heating temperatures of the front end of the billet are set in advance during extrusion. And calculating a billet temperature gradient such that the heat energy applied to the billet can be extruded with a minimum necessary for each of the heating temperatures, and for each of the calculated heating temperature gradients.
9. An extrusion speed pattern is obtained by the method described in any one of 9 above. Among the obtained extrusion speed patterns, the one that requires the shortest time from the start of extrusion to the end of extrusion is selected as the optimum extrusion speed pattern. The extrusion method according to any one of claims 5, 7, and 9, wherein the extrusion is performed according to the determined optimum extrusion speed pattern. 12. An extruded product made of an aluminum alloy produced by the extrusion method according to any one of claims 1 to 11, wherein the extruded material has a recrystallized surface thickness over the entire length of the extruded material. Is 100 μm or less. 13. An extruded product made of an aluminum alloy produced by the extrusion method according to any one of claims 1 to 11, wherein a variation in tensile strength and proof stress is 20 N / over the entire length of the extruded material. An extruded material characterized by being within ² mm2.