KR20200145993A - Method of heat treatment of metal castings - Google Patents

Abstract

The present invention overcomes the mentioned and other disadvantages related to processes of an existing technique. The present invention provides an improved method and device for heat treating a metal casting having a sand core, which are provided to recover a sand core material for removing and reusing the sand core. According to the present invention, the method and the device remove necessity of chiseling and shaking of the casting before heat treatment, so that possibility of damage related to chiseling and shaking steps is excluded. Moreover, the method recovers casting sand in a clean state.

Description

Method of heat treatment of metal castings

The present invention relates generally to a method and apparatus for heat treatment of a hollow metal casting, and more particularly, an improved method of heat treatment of a metal casting having a sand core provided for recovery of a sand core material for removal and reuse of the sand core. And to an apparatus.

Methods and apparatus for manufacturing hollow metal castings such as cylinder heads, engine blocks and the like are known. The prior art aluminum casting manufacturing process typically uses a flask-type cast iron mold having the appearance of a block formed on the inner wall of the mold. A sand core preformed from a mixture of foundry sand and organic binder and having the inner shape of the casting formed by the outer surface is placed in the mold. The mold is then filled with molten aluminum alloy.

After the aluminum alloy solidifies, the casting is released from the mold. Since unheated aluminum alloys are more ductile or less strong than expected, it is often necessary to heat-treat the casting to strengthen or harden the metal. According to a conventional manufacturing process, casting sand is removed from the inside of the casting before heat treatment of the casting. The operator digs the foundry sand inside the workpiece with a pneumatic chisel. The casting is then put into the shakeout system's vibrating table to shake the casting and further crush the casting sand to remove the casting sand from the inside of the casting. When the casting sand is removed, the casting is heated to a high temperature to harden the casting.

Heat treatment. Optionally, the casting can be heated again at a lower temperature to age the aluminum.

Then, another step of treating the foundry sand is carried out if it is necessary to recover the foundry sand removed from the inside of the casting for subsequent reuse. The foundry sand removed by chiseling and shaking the foundry is sent to the foundry sand combustion unit to burn the assembly.

It is an object of the present invention to provide an improved method and apparatus for heat treating metal castings. Another object of the present invention is to provide an improved method and apparatus for removing sand cores from metal castings. Another object of the present invention is to provide a method and apparatus for removing a sand core from a metal casting while minimizing the risk of damaging the casting. Another object of the present invention is to provide a method and apparatus for removing a sand core from a metal casting. It is to provide a method and apparatus for removing sand cores from metal castings.

Efforts have been made to overcome some of the shortcomings associated with conventional methods and apparatus for sand casting metal products. One example is disclosed in U.S. Patent No. 4,411,709, in which a method of manufacturing an aluminum alloy casting involves injecting a molten aluminum alloy into a mold having a sand core formed from the casting sand and an organic resin binder. When the aluminum alloy is solidified and the casting is shaken or vibrated to crush the core, about half of the casting sand used to form the core can be easily removed from the casting. Subsequently, the casting is heated to burn out the organic resin binder of the sand core balance. Accordingly, the bonding of the casting sand is released, and about 80% of the remaining casting sand (about 40% of the total core casting sand) is separated from the casting by gravity. After that, the casting is placed in a water tank

It is quenched and water flows through the casting to remove residual casting sand in the casting.

It can be clearly seen that it provides significant advantages over prior art methods and apparatus for sand casting processing. First, there is no need to remove most of the core material prior to heat treatment on the casting; thus, labor, equipment, cost, and damage to the workpiece associated with manual finishing with a sand core or subjecting the workpiece to oscillation and vibration, or The risk of anxiety has been removed.

By applying heat and airflow in the furnace to the sand core material, the resin binder that melts the core foundry sand is burned. In order to ensure that all assemblies are substantially continuous, the screen 52 prevents chunks of core material larger than the predetermined size from falling out of the furnace, and a sufficient amount of bonds to allow the lumps to disintegrate and pass through the screen. I hold such a lump in the processing chamber 15 until it is burned. Clumps of material small enough to pass through the screen 52 impinge on the inverted V-shaped baffle 53 and roll down the inclined wall of the baffle, further decomposing the material into its individual foundry particles. Thus, the foundry sand is recycled in a clean and reusable condition.

1 is a plan view of a first embodiment of an apparatus for heat treating, quenching and aging metal castings according to the present invention.
FIG. 2 is a cut-away view of the heat treatment furnace of the device of FIG. 1;
3 is an end cut-away view of the heat treatment furnace of FIG. 2.
FIG. 4 is a side cutaway view of the quenching bath of the apparatus of FIG. 1;
FIG. 5 is an end cutaway view of the aging oven of the apparatus of FIG. 1;

Referring to the drawings in which the same reference numerals denote the same members throughout the drawings, FIG. 1 shows a heat treatment and aging apparatus 10 for a metal casting according to the present invention. In the disclosed embodiment, the metal casting is a cylinder head cast from an aluminum alloy by a conventional method. The casting process is known to those skilled in the art and is not included in the part of the invention. Therefore, the casting process will be described briefly.

The casting process uses a flask-type cast iron mold having an outer surface of the cylinder head formed on the inner surface. Caster and enemy

A sand core containing the resulting binder material and defining the inner shape of the casting is placed in the mold. Binders according to the application examples include phenolic resin binders, phenolic urethane cold box binders, or other suitable organic binder materials. The mold is then filled with molten aluminum alloy. When the alloy solidifies, the casting is separated from the mold to prepare for heat treatment and aging.

The heat treatment and aging apparatus includes a heat treatment furnace 11, a quenching bath 12, and an aging oven 13. In the disclosed embodiment, the three components are placed in a U-shape, and the heat treatment furnace 11 is included in one leg of a U-shape, and the quenching bath 12 is included in the U-shaped bottom, and the aging oven 13 ) Is included in the other leg of the U.

However, referring to space limitations, other shapes such as a straight shape or an L-shaped arrangement can be adopted. Referring to Figs. 2 and 3, the heat treatment furnace 11 defines a processing chamber 15 therein. . The heat treatment furnace 11 comprises several different zones 16, the nature and purpose of which will become clear below. In this embodiment, the heat treatment furnace includes eight zones 16A-16H. However, since the number of zones 16 is not important, it may be divided into more or less than the number of zones if a separate application example is needed.

In each section of the heat treatment furnace 11, a pair of burners 18 are mounted on the vertical sidewalls 19 and arranged diagonally so as to be ignited in opposite directions to heat the processing chamber 16 of the heat treatment furnace. The burner 18 is a conventional medium speed regulated air burner commercially available from various other manufacturers. As can be seen from FIG. 3, each burner 18 includes a fuel conduit 20 that supplies natural gas to the burner. A combustion air injector 21 connected to the burner by an air duct 22 supplies combustion air to the burner. The butterfly valve 23 located in the air duct 22 is adjustable to control the volume of air supplied to the burner 18.

The burner 18 is designed to heat the processing chamber 15 of the heat treatment furnace 11 to a temperature of about 4544 to 5378°C (850 to 1000°F). In this embodiment, the processing chamber 15 is heated to about 5267°C (980°F). The butterfly valves 23 for the first zone 16A and the fourth to eighth zones 16D to 16H are adjusted to introduce 10 to 13% of oxygen to their respective burners 18. The butterfly valves 23 for the second and third zones 16B and 16C are adjusted to introduce 13-17% of oxygen to their respective burners. The functions and purposes of controlling the amount of oxygen supplied to the various zones 16 are described below.

The heat treatment furnace 11 further includes a preheating chamber 24 disposed on the upstream side of the heating zone 16. Exhaust gas from the heating zone 16 is sent through the preheating chamber 24 to preheat the preheating chamber to a temperature of about 260 to 3711°C (500 to 700°F). Significant energy savings are achieved by heating the preheating chamber 24 using waste gas rather than a burner. The heat treatment furnace 11 has a lead-in door 25 at its upper end 26 and a discharge door 27 at its lower end 28. Another door 29 separates the preheating chamber 24 from the heating zone 16. In order to prevent heat loss through the wall of the heat treatment furnace, a layer of ceramic fiber insulator 30 is disposed immediately inside the outer wall 31 of the heat treatment furnace.

The metal liner 32 is disposed inside the ceramic fiber insulator. The purpose of the metal liner 32 is to protect the insulator 30 from the polishing effect of scattered sand, although described in detail below.

In the processing chamber 15 of the heat treatment furnace 11, a roller hearth including a plurality of driven rollers 36 for supporting and transporting the workpiece in the forward direction indicated by the arrow 38 through the heat treatment furnace 34 ). The drive mechanism for driving the roller hearth 34 and the roller 36 is a conventional design known to those skilled in the art.

The roller hearth 34 at the inlet and outlet positions of the heat treatment furnace 11 includes a high-speed clutch actuation roller for quickly sending a workpiece into and out of the heat treatment furnace. In addition, the portion of the roller hearth 34 that sends the workpiece from the preheating chamber 24 into the heating zone 16 of the heat treatment furnace also includes a high speed clutch actuation roller. The main part of the roller hearth 34 disposed in the heat treatment furnace 11 is driven at a constant speed.

When the casting is easily charged into the heat treatment furnace 11 and the casting is loaded into the basket 40 in order to easily pass through the heat treatment furnace, the casting is loaded on the roller hearth 34 so as to be transferred through the heat treatment furnace. In this embodiment, each basket 40 accommodates 40 to 50 workpieces. The basket 40 has an open structure so that the casting sand freely falls out of the basket and is removed from the workpiece. In order to easily remove the foundry sand from the workpiece, preferably, if the workpiece is placed inclined in the basket 40, the foundry sand is more easily separated.

To further explain the roller hearth 34, the speed of the roller hearth at which the workpiece is conveyed through the heat treatment furnace 11 is a function of the manufacturing capacity of the device 10. Therefore, in this embodiment, in which the heat treatment furnace 11 has to accommodate a new workpiece basket every 35 minutes, the roller hearth 34 replaces the previous workpiece basket with the next workpiece gasket within 35 minutes.

Must be transported at least a distance sufficient to allow the heat to be introduced into the furnace. In this embodiment, the roller hearth 34 transfers the workpiece through the heat treatment furnace at a speed of about 1829 cm/hr (6 ft/hr) according to the size of the basket and the manufacturing requirements of the device.

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Claims (10)

In a method for heat treatment of a casting including at least casting sand particles bonded to each other with a binder material and having a sand core defining a cavity in a metal casting, introducing the metal casting having the sand core into a furnace, the Heating a furnace to a temperature exceeding the combustion temperature of the binder material, providing an oxygen-rich atmosphere in the heated furnace, and causing the binder material to be burned so that the foundry sand particles of the sand core are separated from the sand core. The steps of accommodating the metal casting having the sand core in the heating furnace of the oxygen-rich atmosphere so as to exit, removing the foundry sand particles separated from the cavity, and the sand coming off the casting before the binder material is burned. And collecting a lump of core material; and burning the binder material by holding the lump of sand core material that have come off in the furnace. The method of claim 1, wherein the step of removing the foundry sand particles separated from the cavity comprises at least air relative to the casting when the casting is accommodated in the furnace so that the air flow drops the foundry sand particles away from the cavity. Heat treatment method comprising the step of sending a flow. The method of claim 2, wherein the step of sending air flow to the casting when the casting is housed in the furnace sends air flow to the casting at an air flow velocity exceeding at least 9144 m/min (3000 ft/min). Heat treatment method comprising the step. The method of claim 1, wherein the step of removing the foundry sand particles separated from the cavity comprises: tilting the metal casting in the furnace so that at least a portion of the found sand particles fall away from the metal casting by gravity. Heat treatment method comprising a. The heat treatment method according to claim 1, further comprising the step of collecting a portion of the foundry sand particles separated from the casting and transferring it out of the furnace. The method of claim 1, wherein the capturing and holding a lump of sand core material that has fallen apart is provided by placing a screen under the metal casting having a hole that is not large enough to allow a lump of sand core material of at least a predetermined size to pass through. Heat treatment method characterized in that it comprises the step of. The method of claim 6, further comprising the step of crushing the lump by hitting a lump of sand core material smaller than a predetermined size passing through the screen on a surface. The method of claim 7, wherein the step of impinging on the surface a mass of sand core material smaller than a predetermined size causes at least a mass of sand core material less than a predetermined size passing through the screen to strike on the inclined surface and from the inclined surface. Heat treatment method comprising the step of crushing the mass by rolling off. A method for heat-treating a casting comprising at least casting sand particles bonded to each other with a binder material and having a sand core defining a cavity in a metal casting, the metal casting before removing the substantial sand core portion from the cavity in the metal casting Introducing into a furnace, and introducing the furnace into the binder material
Heating to a temperature exceeding the combustion temperature, providing an oxygen-rich atmosphere in the furnace, and the metal casting having a sand core in the oxygen-rich atmosphere in the heated furnace so that the binder material can be burned A heat treatment method characterized in that, while the metal casting is in the furnace, the sand core part is separated from the sand core and separated from the cavity. 10. The method of claim 9, wherein before the binder is combusted from the metal casting, suspending a portion of the sand core separated from the metal casting in an oxygen rich atmosphere in the furnace, and once the binder is burned from the sand core portion, the Heat treatment method further comprising the step of releasing the suspension of the suspended sand core portion.

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