JP2005133103A - Method for heat-treating aluminum alloy material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat treatment method which shortens treatment time, reduces energy consumption and secures an adequate hardness of an aluminum alloy casting. <P>SOLUTION: An objective method includes the first step of casting an aluminum alloy material in a casting machine; the second step of rapidly heating a cast piston to about 520°C which is in the vicinity of an eutectic point (530°C) temperature, with a high-heat gas that has flowed into a heating chamber from a heat-generating device and circulates therein; and the third step of holding each rapidly temperature-raised piston at about 520°C for about 3 minutes in a holding chamber in which the atmospheric temperature is controlled by a cooling fan device. The method subsequently includes the fourth step of rapidly cooling the piston by taking it out from the holding chamber and charging it into a cooling water tank; and then, the fifth step of charging the rapidly cooled piston inside an aging furnace, and aging it at a predetermined temperature for a predetermined period of time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a heat treatment method for changing mechanical properties after casting an aluminum alloy material such as a piston which is a part of an automobile.

  As a heat treatment method of this kind, an aluminum alloy material (Al—Si system), various methods have been conventionally provided, and one of them is described in Patent Document 1 below.

  The present invention casts a JIS-AC4CH Al—Si based aluminum alloy, rapidly raises the casting at 570 ° C. immediately below the eutectic point of 577 ° C., and rapidly cools after reaching the vicinity of the eutectic point. Solution treatment is performed, and thereafter, aging treatment is performed at 145 ° C. for various aging treatment times.

As a result, the solution treatment can be performed in a short time, the productivity is increased, and the energy consumption is also reduced.
JP 7-310150 A

  However, in the conventional heat treatment method, the specific heat treatment conditions and the like are unclear, and for example, the shorter the holding temperature until the temperature is raised in the solution treatment after casting, the shorter the temperature holding time, and the like are better. However, even if heat treatment is performed according to the examples, there is a possibility that the aluminum alloy material may not have sufficient hardness as described in the experimental results of the graph.

  Therefore, the present invention provides a heat treatment method capable of ensuring sufficient hardness of an aluminum alloy cast product while shortening the treatment time and suppressing energy consumption based on the specific conditions of the heat treatment method.

  The present invention has been devised in view of the technical problem of the conventional heat treatment method for an aluminum alloy material, and the invention according to claim 1 is characterized in that the temperature of the cast product is reduced after casting the aluminum alloy material. It is characterized in that the temperature is raised from 300 ° C. or higher to the vicinity of the eutectic point, held at that temperature for about 3 minutes or more, and then a solution treatment is performed by quenching the cast product, followed by an aging treatment Yes.

  According to the present invention, since the temperature is raised to the vicinity of the eutectic point after casting and before the temperature becomes 300 ° C. or lower, consumption of temperature rising energy can be sufficiently suppressed.

  Moreover, after raising the temperature to the vicinity of the eutectic point, the temperature is maintained for about 3 minutes, and the subsequent rapid cooling treatment shortens the overall treatment time, thereby improving the productivity of aluminum alloy castings. The hardness can be increased by changing the mechanical properties.

  The invention according to claim 2 is characterized in that the temperature raising time to the vicinity of the eutectic point is set within a time period in which an edge remains in the silicon particles contained in the cast product. Yes.

  According to this invention, since the circularity coefficient of the silicon particles contained in the cast product is not increased and the edge is left, the area occupied by silicon with respect to aluminum increases, and wear resistance is improved. Improvement can be achieved.

  The invention described in claim 3 is characterized in that a continuous heat treatment is performed by arranging a casting machine for casting the aluminum alloy material and a solution furnace for solution treatment in the vicinity.

  According to this invention, since the casting machine and the solution furnace are close to each other, the movement time of the aluminum alloy cast product from the casting to the solution furnace is shortened. Therefore, the aluminum alloy casting can be moved into the solution furnace while maintaining a temperature of 300 ° C. or higher. In other words, since the temperature can be secured from the casting machine to the solution furnace without using any heating machine, the processing work can be improved and the processing cost can be reduced.

  Hereinafter, embodiments and examples of a heat treatment method for an aluminum alloy material according to the present invention will be described in detail with reference to the drawings. In addition, the cast of aluminum alloy provided for each embodiment is applied to a piston of an internal combustion engine.

  First, a heat treatment apparatus for performing a heat treatment method will be described with reference to FIG.

  In this heat treatment apparatus, a series of processing operations from casting of an aluminum alloy material to solution treatment and aging treatment are continuously performed by a robot, and each line facility is installed within a range reachable by the robot arm. .

  That is, the solution furnace 2 is disposed in the vicinity of the casting machine 1, and the cooling water tank 3 is disposed in the vicinity of the solution furnace 2 on the side opposite to the casting machine 1, and in the vicinity of the cooling water tank 3. A high-speed aging furnace 15 is arranged.

  The casting machine 1 is operated by a hydraulic unit (not shown), and the hydraulic source of the hydraulic unit is controlled by a control panel.

  As shown in the figure, the solution furnace 2 has a box-shaped furnace body 4 in which the inside of the furnace body 4 is separated and separated into a temperature raising chamber 5 and a holding chamber 6 in a subsequent process via partition doors 4a to 4c. A conveyor type conveyor 8 for continuously guiding individual piston castings 7 made of an aluminum alloy material cast by the casting machine 1 into the temperature raising chamber 5 and the holding chamber 6 is disposed in a horizontal direction. ing. In addition, heaters 9 and 10 are provided in the lower portion of the furnace body 4 for heating the temperature rising chamber 5 and the piston casting 7 in the holding chamber 6.

  The transport device 8 has a front end portion 8 a extending to the vicinity of the casting machine 1, and a rear end portion 8 b extending to a position above the cooling water tank 3.

  Further, two non-contact type radiation thermometers 11a and 11b serving as monitoring means are provided on the front end side of the furnace body 4, and these radiation thermometers 11a and 11b are mounted on the carrier 8. The temperature of the piston casting product 7 immediately after casting and in the heating chamber 5 is detected.

  The heating chamber 5 is supplied with a high-temperature gas, which is a high-temperature fluid, from a heat generator 12 provided in the upper part of the furnace body 4 via a duct device 13, and rapidly heats the piston casting 7 guided inside. It is supposed to be.

  The holding chamber 6 is configured to heat and cool a plurality of aluminum alloy materials 7 guided to the inside by driving a fan 14a of a cooling fan device 14 provided on the top of the furnace body 4 to a predetermined temperature. .

  In the cooling water tank 3, water W having a temperature of approximately 40 ° C. to 90 ° C. is stored, and the piston casting product 7 discharged from the holding chamber 6 and introduced into the interior is rapidly cooled. ing.

  The high-speed aging furnace 15 collectively accommodates many piston castings 7 cooled in the cooling water tank 3 and aged at a temperature of about 200 ° C. for about 2 hours. Yes.

  First, as the aluminum alloy material, JIS AC8A, an Al—Si based alloy material is used, and the composition of the sample is 11.1% by weight for Si, 1.1% by weight for Cu, 1.2% by weight for Ni, Fe is 0.4% by weight. Mn was set to 0.03% by weight, Ti was set to 0.04% by weight, and Zn was set to 0.04% by weight.

  As shown in FIG. 2, the aluminum alloy material is cast in the casting machine 1 (first step), and after solidification is completed, the piston cast product 7 is taken out from the mold by a robot, and after applying a black body paint, It is placed on the front end portion 8a of the conveyor 8. At this time, the temperature of the piston casting 7 is detected by the first radiation thermometer 11a. As a result of the detection, if it is determined that the temperature is 300 ° C. or higher, the door 4a is opened as it is, and is sent into the temperature raising chamber 5 by the transfer device 8, but for some reason, the temperature drops to 300 ° C. or lower. What is present is removed from the conveyor 8 by the robot.

  Next, the temperature of the piston casting product 7 conveyed to the temperature raising chamber 5 by the conveyor 8 is similarly detected by the second radiation thermometer 11b. In this case, for some reason, 300 What has fallen below ℃ is removed from the temperature raising chamber 5 by the robot. However, since the distance from the casting machine 1 to the heating chamber 5 is usually short, the piston casting product 7 is maintained at a temperature of about 420 ° C. as shown in the temperature change graph of FIG.

  In the heating chamber 5, the piston casting 7 is rapidly heated to about 520 ° C. near the eutectic point (P) by the high-temperature gas flowing in and circulating from the heat generator 12 through the duct device 12 a. (Second step). That is, since the eutectic temperature of AC8A is about 530 ° C., it was heated to the vicinity thereof.

  Thereafter, when the temperature rapidly reaches about 520 ° C., the carrier 8 guides the holding chamber 6 through the door 4b. Here, while the internal hot air is agitated by the cooling fan device 14 and controlled so that the ambient temperature becomes uniform, each piston casting product 7 is held at a temperature of about 520 ° C. for about 3 minutes (third). Process). In addition, the temperature raising time up to 520 ° C. is set within a time such that an edge remains in the silicon particles Si contained in the piston casting 7.

  Subsequently, the piston casting product 7 is introduced into the cooling water tank 3 from the holding chamber 6 by the transport device 8 in a fixed posture, and is rapidly cooled here (fourth step).

  In this example, the solution treatment time from the start of temperature increase in the second step to the temperature decrease due to rapid cooling from the fourth step is set to about 10 to 15 minutes as shown in FIG.

  Thereafter, the rapidly cooled piston casting product 7 was put into an aging furnace 15, where an aging treatment was performed at a temperature of about 200 ° C. for about 1.5 hours (fifth step).

  FIG. 4 is a graph in which the hardness (HRB) of the piston casting product 7 is experimentally measured by changing the temperature rise start temperature (° C.) and solution treatment time in the second step in the solution treatment of the piston casting product 7. is there.

  In this experiment, the component composition of the piston casting 7 was the same as described above, and the temperature increase in the second step was set to about 520 ° C. Further, the solution treatment time was measured by dividing into 0 minutes, 2 minutes, 3 minutes, 5 minutes, 10 minutes, and 20 minutes as in the conventional technique.

  The solution treatment time was the time from when the temperature reached about 520 ° C. in the second step to rapid cooling (water quenching) in the fourth step. As aging conditions, the temperature was set to 200 ° C. and about 6 hours.

  According to this experiment, it has been found that in most cases, when the temperature of the piston casting 7 in the temperature raising chamber 5 is heated from around 200 ° C., diffusion of solute atoms at the solution temperature is delayed.

  On the other hand, when the temperature rising start temperature is set to 300 ° C. or higher, it is found that the diffusion rate of solute atoms does not decrease, and when the temperature raised to at least 525 ° C. is maintained for at least 3 minutes, It was found that sufficient hardness of 79-79.7 was obtained by changing the mechanical properties.

  In addition, even when the temperature rise start temperature is 100 ° C., it can be seen that the same degree of hardness as 300 ° C. can be obtained. Warm time becomes longer. For this reason, a heat energy loss will become large.

  Further, as in the case of the above-described example, when the temperature rising start temperature is 400 ° C. or higher, as shown in FIG. 4, the conventional solution treatment time other than 0 hours only has a hardness of 79.5 or higher. Or since the temperature rising time to 520 ° C. is shortened, it is possible to sufficiently suppress the loss of heat energy.

  Moreover, in this example, as described above, in the third step, after the temperature is raised to 520 ° C. near the eutectic point, the temperature is maintained for about 3 minutes. It is clear from FIG. 4 that the hardness can be increased by changing the thickness.

  Further, the temperature raising time up to 520 ° C. in the third step is set within a time period in which an edge remains in the silicon particles Si contained in the aluminum alloy material. Since the circularity coefficient of the silicon particles contained in the product 7 is not increased and the edge is left, the area occupied by silicon with respect to aluminum is increased, and the wear resistance can be improved.

  In addition, since the casting machine 1 and the solution furnace 2 are arranged in the vicinity and the heat treatment is continuously performed, the moving time of the piston casting 7 from the casting to the solution furnace 2 is shortened. Therefore, the piston casting product 7 can be moved into the heating chamber 5 while maintaining a temperature of 420 ° C. or higher. In other words, since the temperature can be secured from the casting machine 1 to the solution furnace 2 without using any heating machine, the processing work can be improved and the processing cost can be reduced.

  In addition, since the cooling water tank 3 and the aging furnace 15 are also continuously arranged in the vicinity, the aging treatment can be continuously performed from the cooling of the solution treatment, so that the heat treatment time can be sufficiently shortened. it can.

  Furthermore, since the piston casting product 7 is heated by the high-temperature gas in the temperature raising chamber 5, the flow rate of heat to the piston casting product 7 is increased by the flow of the hot gas, and the temperature raising time is shortened. I can plan. Further, the piston casting product 7 as a whole can be heated more uniformly by the positive stirring effect of the fluid gas in the holding chamber 6 by the cooling fan device 14.

  Further, the temperature of the individual piston castings 7 conveyed into the temperature raising chamber 5 is detected by the radiation thermometers 11a and 11b, and those below 300 ° C. are excluded in or before the temperature raising chamber 5, Wasteful consumption of the temperature rising energy can be more reliably suppressed, and the processing can be further shortened. Further, since the piston casting product 7 does not exceed the eutectic point temperature by monitoring the temperature, eutectic melting does not occur and sufficient hardness can be maintained.

  In addition, the overall temperature of many piston castings 7 is not monitored, but the individual temperatures are monitored, so that the temperature management accuracy can be improved.

The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.
(1) The solution furnace is composed of two chambers, a rapid heating chamber and a holding chamber. In the rapid heating chamber, the aluminum alloy material is heated to a set temperature with a high-temperature fluid, and in the holding chamber, the set temperature is set. The method for heat-treating an aluminum alloy material according to any one of claims 1 to 3, wherein the temperature is maintained by a high-temperature fluid.

According to the present invention, since heating is performed with a high-temperature fluid such as a high-temperature fluid or hot air, the speed of heat with respect to the aluminum alloy material is increased, so that the temperature rise time can be shortened and the whole can be made uniform by the fluid stirring effect. It becomes possible to heat to.
(2) A monitoring means for monitoring the temperature of each aluminum alloy material that is cast and transported to the solution furnace is provided, and the aluminum alloy material is shared in the rapid heating furnace according to temperature information from the monitoring means. The method for heat treatment of an aluminum alloy material according to claim 1, wherein the temperature is controlled so as not to exceed a crystal point.

  According to this invention, since the eutectic point temperature of the aluminum alloy casting is not exceeded by temperature monitoring, eutectic melting does not occur and sufficient hardness can be maintained.

In addition, since the individual temperatures are monitored rather than monitoring the entire temperature of the cast aluminum alloy casting, the temperature management accuracy can be improved.
(3) A cooling water tank for cooling the aluminum alloy material solutionized in the solution furnace and an aging furnace for performing an aging treatment after the cooling treatment are continuously arranged. 2) Heat treatment method of aluminum alloy material.

  According to the present invention, since the temperature raising and cooling of the solution treatment and the aging treatment can be continuously performed from the cooling, these heat treatment times can be sufficiently shortened.

  The present invention is not limited to the configuration of the above embodiment. For example, the temperature monitoring means may be a contact type in addition to the non-contact type such as the radiation thermometers 11a and 11b. good.

It is the schematic which shows the heat processing apparatus provided to the heat processing method of the aluminum alloy material which concerns on this invention. It is a block which shows the heat processing process by the said heat processing apparatus. It is a characteristic view which shows the relationship between the processing time and the heat processing temperature in the heat processing method by the said heat processing apparatus. It is a graph which shows the relationship between the temperature rising start temperature performed in experiment, and the hardness of a piston casting product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Casting machine 2 ... Solution furnace 3 ... Cooling water tank 4 ... Furnace body 5 ... Temperature raising chamber 6 ... Holding chamber 7 ... Piston casting 8 ... Conveyor 9 * 10 ... Heater 11a, 11b ... Radiation thermometer (monitoring means) )
12 ... Heat generating device 14 ... Cooling fan device 15 ... Aging furnace

Claims (3)

After casting the aluminum alloy material, the temperature of the cast product is raised from near 300 ° C. to the vicinity of the eutectic point, held at that temperature for about 3 minutes or more, and then the cast product is rapidly cooled to form a solution. A heat treatment method for an aluminum alloy material, characterized by performing an aging treatment after the treatment. 2. The aluminum alloy according to claim 1, wherein the temperature raising time to the vicinity of the eutectic point is set within a time in which an edge remains in the silicon particles contained in the casting. Material heat treatment method. The heat treatment method for an aluminum alloy material according to claim 1 or 2, wherein a continuous heat treatment is performed by arranging a casting machine for casting the aluminum alloy material and a solution furnace for solution treatment in the vicinity.

Images