JPH0191957A - Heat treatment for casting - Google Patents

Abstract

PURPOSE:To improve the efficiency of a core removing work by intermittently feeding a casting to a heating furnace, injecting an air to the shell core at its stopping time as well and burning the shell core by the heating furnace temp. and air. CONSTITUTION:A waling beam 8 is provided in a heating furnace F to move a casting W forwards by the moving stroke of the beam 8. In this case, hole as cost 11, 11 of the casting W are engaged via the positioning pin 9 of a mobile feeding bar 1 to move the casting W. An air nozzle 13 is provided on the heating furnace F and an air piping 14 is connected to the nozzle 13. It is thus heated at the heating furnace stm. temp. at the stopping position inside the furnace of the casting W, a compressed air is blown into the opening part 15a of a shell core 15 as well, the core 15 is burnt and the burning collapse is executed. The collapse reaches to the inner part of the core 15, so the efficiency of the core 15 removing work is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for heat treating a casting that has been cast by placing a shell core in a mold cavity.

[Prior Art] When removing the shell core remaining in the casting before sending the casting using a shell core to a subsequent process such as a machining process, it may be necessary to remove the shell core remaining in the casting, depending on the size, shape, etc. of the core. , it may be difficult to disintegrate and remove using normal mechanical methods. In such cases, the casting containing the core is heated at a predetermined temperature for a predetermined period of time to burn the binder (resin) contained in the shell core to improve the collapsibility of the core, and to remove the core. Conventionally, efforts have been made to facilitate this.

For example, when the cylinder block of a vehicle engine is manufactured from aluminum alloy casting, the water jacket through which the engine cooling water passes is formed by placing a shell core in the mold during casting. It is difficult to remove the subsequent core using normal mechanical methods, and the following methods are used.

That is, first, unnecessary parts such as weirs and runners are removed from the casting material, then vibration is applied to the casting material to cause part of the core to collapse, and the collapsed portion is removed.

Thereafter, the casting material is heated to 350°C or higher and held for about 4 hours to burn off the binder contained in the core and improve the disintegration of the remaining core.Furthermore, the casting material is subjected to vibration. to disintegrate and remove the remaining core.

By the way, the core for forming the water jacket part of the cylinder block is usually made of resin-coated core sand particles coated with a binder (resin) in order to improve the strength of the core. It is made of sand, and the sand particles are strongly bonded to each other not only on the surface of the core but also inside it, making it able to withstand pressure during pouring and other external forces.Therefore, after casting, the nonyl In order to improve the disintegrability of the core and to perform core removal work efficiently, it is necessary to burn not only the surface of the core but also the binder inside.

When the binder used in the shell core is heated at a temperature of 350° C. or higher, it can burn even the contents inside the core, as long as oxygen is supplied sufficiently.

[Problem to be solved by the invention] However, when heating a casting containing a core to burn out the binder in the core, conventional methods simply hold the casting at a predetermined temperature in a heating furnace for a predetermined period of time. Since the amount of oxygen supplied was not sufficient, the binder inside the core could not be burned, and therefore the disintegrability of the core could not be sufficiently improved. For example, at a heating temperature of about 400°C, the binder near the surface of the core can be burned, but the binder inside the core cannot be burned, so the disintegration of the inside of the core is could not be sufficiently increased.

For this reason, it may be possible to increase the heating temperature of the casting to promote the combustion of the binder, or if the melting point of the casting material is relatively low, such as aluminum alloy, the heating temperature may be set too high. Since this may damage the properties of the casting material, it has not been possible to apply a temperature high enough to burn the binder inside the core even in an insufficient supply of oxygen.

[Object of the invention] This invention was made to solve the above problems, and it is an object of the present invention to improve the collapsibility inside the shell core without increasing the heating temperature, and to improve the efficiency of core removal work. With the goal.

[Means for Solving the Problems] For this reason, the present invention provides a method for heat treating a casting including a shell core, which is carried out without passing through a heating furnace, in which the casting is transported intermittently in the heating furnace, At the stopping position of the casting, air is blown to the shell core from an air nozzle provided at a position opposite to the opening of the shell core, and the shell is heated by the atmospheric temperature in the heating furnace and the air that permeates into the shell core. It is designed to burn the core.

[Effects of the Invention] According to the present invention, the casting is conveyed intermittently in the heating furnace, and at the stopping position of the casting, the air nozzle is fitted into the opening of the shell core included in the casting. Therefore, in addition to the atmospheric temperature in the heating furnace, the combustion of the binder in the shell core can be promoted by the compressed air jetted from the air nozzle. As a result, it is possible to improve the collapsibility not only near the surface of the shell core but also inside it, and also to improve the firing efficiency (and to improve the discharge efficiency of core sand). Be able to carry out removal work efficiently.

[Example] Hereinafter, a case where an example of the present invention is applied to an aluminum alloy casting of a cylinder block of a vehicle engine will be described with reference to the accompanying drawings.

This example is applied to the heating step of the T6 treatment described above for a cylinder block that particularly requires high strength and high hardness, and requires solution treatment T6 on the cast material. In addition, after casting, the above casting material may have been removed by removing unnecessary parts such as weirs and runners in the process before heat treatment, and a part of the core may have been collapsed and removed by vibration, or it may have been used to form a water jacket part. The shell core is made of Lennon coated sand, and cannot be removed using only the mechanical methods described above, so it is sent to the heat treatment process while containing the shell core.

As shown in FIGS. 1 and 2, the casting W containing the shell core has two fixed rails 2 disposed in parallel, It is carried into the heating furnace F by a conveyance device equipped with a movable feed bar I disposed between the fixed rails 2 and parallel to the rails 2. The heating furnace F is a continuous furnace in which heat-treated products are heat-treated without passing through the furnace, and has a ceiling 3 and a hearth 4.
A large number of heating elements 5 are arranged in parallel in a direction perpendicular to the direction of movement of the casting W (to the right in the figure) in order to maintain the inside of the furnace at a predetermined temperature.

The movable feed bar 1 is fixed to a lifting rod 6 of an intermittent feeding device A that is arranged at appropriate intervals in the longitudinal direction of the furnace F, and is positioned above the fixed rail 2 when the lifting rod 6 is in the raised position. When the elevating rod 6 is in the lowered position, it is positioned below the fixed rail 2 and the casting W is placed on the fixed rail 2. The lifting rod 6 is vertically movably attached to a walking beam 8 that is movable back and forth in the longitudinal direction of the heating furnace F on a pedestal 7 fixed to the floor surface G. Further, an opening 4a is provided in the hearth 4 so that the lifting rod 6 can move back and forth in accordance with the back and forth movement of the walking beam 8, and the opening 4a prevents heat dissipation from inside the heating furnace F. Therefore, the hearth 4 is covered with a slide shutter 12 installed on the lower surface.

In the intermittent feeding device A, when the lifting rod 6 rises and the movable feeding bar 1 lifts the casting W above the fixed rail 2, the walking beam 8 moves forward (to the right in the figure).
Then, while the lifting rod 6 is lowered and the casting W is placed on the fixed rail 2,
The walking beam 8 moves backward (to the left in the figure) and remains stationary until the lifting rod 6 rises again, so that the casting W in the heating furnace F is intermittently transported forward. It has become.

Two positioning pins 9 are fixed to the movable feed bar 1 at predetermined intervals in the longitudinal direction of the movable feed bar 1 in order to accurately determine the position of the casting W on the feed bar 1. The positioning pin 9 is fitted into a cast hole 11.11 of a cylinder head mounting bolt hole of the casting W being transported with the cylinder head mounting surface facing downward. The distance between the positioning pins 9 is set to be equal to the movement stroke of the walking beam S. Due to the lowering of the lifting rod 6, the casting W is separated from the movable feed bar 1 and placed on the fixed rail 2.
However, after a predetermined period of time has elapsed, when the lifting rod 6 is raised and the movable feed bar 1 is lifted again, the positioning pin 9.9 disposed in front by a predetermined interval is fitted into the cast hole 11.11. As a result, the casting W is moved forward by the movement stroke of the walking beam 8 while being accurately positioned.

Incidentally, the heating furnace F is provided with an air nozzle 13 for blowing air into the opening of the shell core forming the water jacket portion of the cylinder block.

The air nozzle! 3 is connected to an air pipe 14 for supplying compressed air from a near compressor (not shown) installed outside the heating furnace F to the air nozzle 13. The air piping 14 is arranged so that the length of the piping inside the heating furnace F is as long as possible in order to prevent the temperature of the casting W from decreasing due to the air ejected from the air nozzle 13.

The air nozzle 13 is provided between the movable feed bar 1 and the fixed rails 2.2 on both sides, as shown in FIG.
With the casting W placed on the fixed rails 2, 2, the third
As shown in the figure, the positional relationship with the positioning pin 9.9 is determined so as to fit into the opening 15a of the shell core 15 for forming the water jacket part included in the casting W. Also, the air nozzle mentioned above! As shown in detail in FIG. 4, 3 preferably has a plurality of air injection holes 13a on the side surface near its tip in order to prevent clogging due to collapsed core sand falling from above. The height of the tip of the air nozzle 13a is set so that the air nozzle 13a is located within the opening 15a when the air nozzle 13 is fitted into the opening 15a. And the opening 15a
Compressed air is blown into the unit for a predetermined period of time.

Due to the heating step of solution treatment T6, i.e. about 500
Casting W carried into heating furnace F to be heated at ℃ for about 2 hours
After being heated to a temperature of 350°C or higher in the heating furnace F, the opening 15 of the shell core 15 is heated by the above-mentioned air nozzle 13 during the first half of the holding period at approximately 500°C.
Compressed air is blown into the shell core 15, and the shell core 15 is fired and collapsed.

During the firing collapse period of the casting iron 15, compressed air is supplied from the air nozzle 13 until the temperature of the casting W is 3.
The reason I decided to do it after the temperature reached 50℃ or higher was 350℃.
This is because the combustion efficiency of the binder in the shell core I5 deteriorates below 500°C.
The reason for finishing the process by this time is to uniformly apply the temperature (approximately 500° C.) required for the T6 treatment to the entire casting W.

Therefore, the installation location of the air nozzle I3, the number of installation locations, the number of nozzles at each location, etc. are determined based on these considerations and the size of the casting W.

As described above, according to the present embodiment, in the heat treatment method for an aluminum alloy casting of a cylinder block of a vehicle engine, the casting W is conveyed intermittently in the heating furnace F, and the casting W is stopped at a stop position. Since the air nozzle 13 is fitted into the opening 15a of the shell core 15 included in the casting W, in addition to the atmospheric temperature in the heating furnace F, the compressed air ejected from the air nozzle I3 causes Combustion of the binder in the shell core I5 can be promoted.

As a result, it is possible to improve the collapsibility not only near the surface of the shell core 15 but also inside the shell core 15 without heating the casting W to a high temperature relatively close to its melting point. The sand discharge efficiency can be controlled, and the core removal work can be carried out efficiently.

Although the above embodiments were applied to aluminum alloy castings, it goes without saying that the present invention can also be applied to castings made of other materials, such as cast iron.

[Brief explanation of the drawing]

The drawings are all for explaining the present invention, and Fig. 1 is a front explanatory view of the inside of the heating furnace, Fig. 2 is a perspective view of the conveying device and the casting, and Fig. 3 is a norinder including the core. FIG. 4 is a vertical cross-sectional view of the casting for the block, and is a vertical cross-sectional view of the tip of the air nozzle fitted into the shell core opening. l...Movable feed bar, 2...Fixed rail, 6...
Lifting rod, 8...Walking beam, 13...Air nozzle, 15...Shell core, 15a...Shell core opening, A...Intermittent feeding device, F. Heating furnace, W.
··casting. Patent Applicant Mazda Motor Corporation Agent Patent Attorney Qing Bai Bo and 2 others Engraving of the 2nd drawing N3 Figure 3 Relationship with the case of the person making the amendment Patent Applicant A Hira Rin Fut Yuwa t: I7+//Chi Address Hiroshima 3-1 Shinchi, Fuchu-cho, Aki-gun, Prefecture Name (313) Mazda Motor Corporation Address 2-1-61, Higashi-ku, Osaka City, Osaka Prefecture 540
No. 7, Contents of amendment IW, in the brief explanation of the drawings in the specification, page 13 of the specification, lines 2 to 4, ``Figure 4 is...a vertical cross-sectional view.'' Masu. First, correct the mt drawings Figures 3 and 4 as shown in the attached sheet. that's all

Claims (1)

[Claims] (1) In a method for heat treatment of a casting including a shell core, which is carried out by passing the casting through a heating furnace, the casting is conveyed intermittently in the heating furnace, and at a stopping position of the casting, the casting is moved relative to the opening of the shell core. Air is blown out to the shell core from an air nozzle installed at a position where
A method for heat treating a casting, characterized in that a shell core is combusted at an ambient temperature in a heating furnace and air permeating into the shell core.