JPS5978750A - External chiller for casting - Google Patents

Abstract

PURPOSE:To prevent melt sticking of an external chiller for a casting to be used in the stage of casting on the casting at the temp. of the cast molten metal by forming an Al diffused layer on the surface of the chiller. CONSTITUTION:Molten steel is charged from a pouring cup 6 through a sprue 7 into a cavity 4 for casting in a casting mold constituted of top and bottom sand molds 2, 1, in the stage of casting the shoe of an endless tracked vehicle made of cast steel. A round bar-like chiller 9 is disposed in the place required for quick cooling in this case. The chiller 9 is beforehand formed thereon with a diffusion coating layer of Al by dipping in molten Al, a diffusion penetration method of Al, a melt spraying method, etc. The Al diffusion coating layer forms an Fe-Al alloy layer on the steel material of the chiller and since a thin layer of Al2O3 is formed on the surface, the removal of the casting is easy without melt sticking the cast steel and the chiller and the repetitive use of the chiller is possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel external cooling metal for castings used during casting.

Chilled metal differs depending on its cooling method.When in use, chilled metal is buried in the molten metal and has a cooling effect, and after solidification, there is an internal chilled metal called a so-called korigurumi, which forms part of the casting, and a metal mold. They are broadly divided into so-called face frames and external cooling metals, which come into contact with the surface of the casting and provide external cooling.

The present invention relates to an external chiller among chillers, and hereinafter the external chiller will be simply referred to as a chiller.

As is well known, chillers are used to locally increase the cooling capacity of the mold and control the solidification rate of the casting. For example, in areas where solidification is delayed, such as local thick areas or thickness intersections. In addition, by forcibly cooling areas where it is difficult to supply hot water from the riser part, the solidification rate is accelerated and the solidification rate is kept in balance with the pond area, thereby preventing the formation of shrinkage cavities and shrinkage of the solidified area. It is used for the purpose of accelerating the solidification rate in areas where cracking is likely to occur in order to prevent hot cracking of castings caused by hot cracking, and to improve properties by densifying the structure of the surface layer of castings by rapid cooling. The shape of the glaze varies depending on the commonly used casting, but rectangular parallelepipeds and round bars are most commonly used, and the materials are cast steel,
Mild steel is often used, and sometimes the same material as the molten metal is used.

Such chilled metals are usually conveniently used by exposing the surface that is to come into contact with the molten metal at a predetermined portion during mold making and fixing it in sand, but there are the following problems. In other words, the casting and the chilled metal are likely to be welded together due to the high heat of the molten metal, and the molten cold metal must be removed by fusing in the subsequent process, and after removal, the welded part must be finished using a grinder, etc., which increases the number of work steps. Furthermore, since the chilled metal can only be used once, consumption increases, which is a factor that increases the cost of castings. To prevent welding, a method has been proposed in which the high-chilled metal is coated with liquid resin and a Sigilcon Sand type coating mold is applied, but this cannot be completely prevented, and conversely, the resin generates gas during casting. The current situation is that casting defects are caused by peeling of the mold and coating.

Also, even if the cold metal is used for the first time, its surface will rust to varying degrees, and after use, it will be covered with scale generated under high temperatures, so if it is used as it is, these iron oxides and the molten metal will rust. Because CO gas is generated by a chemical reaction with carbon, which causes pore defects such as pinholes and blowholes, it is necessary to perform preliminary treatment to clean the surface using shot blasting, a grinder, etc.

The present invention provides a new chiller which eliminates all the drawbacks of conventional chillers, as described above, and is characterized by the formation of an A1 diffusion coating layer on the surface layer of the chiller. That's true. However, this A1 diffusion coating layer is made of Pe.
-A1 alloy layer, or an Al2O3 film formed on the surface and a continuous Fe-A1 alloy layer.

In order to form the A1 diffusion coating layer in the present invention, the surface of the base material is coated with A1 by the A1 diffusion permeation method, the AI dipping method, the thermal spraying method, the electroplating method, etc., and then the person 1 is coated on the base material by heating. Among these methods, the A1 diffusion permeation method, which is the most practical method, will be briefly explained.

The A1 diffusion infiltration method is called calorizing, and there are powder methods, gas methods, etc., of which the powder method is widely used. In the powder method, a penetrating agent containing a small amount of # penetration enhancer consisting of Fe-A1 alloy powder, A1゜03 powder, and a halide should be filled into a metal non-sealable container such as an iron box and allowed to permeate into the penetrating agent. The base material is cooled and completely buried at a temperature of 850 to 1050C for 10 to 10 minutes.
By heating for 25 hours, an Fe-A1 alloy layer, which is an A1 diffusion coating layer, having a required thickness can be formed on the coating layer of the cold metal.

Furthermore, by adjusting the A1 content of the permeability agent, it is possible to freely adjust the A1 concentration of the formed Fe-A1 alloy layer.

According to the experiments of the present inventors, the thus obtained Fe-A1
The surface Al concentration of the alloy layer is 10 to 35% by weight, preferably 20 to 32m:1%, and the layer thickness is 0.1 to 1%, preferably 0.3 to 1. Owm is appropriate. Regarding the surface Al concentration, if it exceeds the 7-fold limit that enables selective oxidation of A1, it will have a welding prevention effect, but if
A due to decrease in Al concentration due to film formation and high temperature of molten metal
Considering the decrease in concentration due to diffusion throughout the cooling of 1, 1
0 weight tg6 or more is likely. In addition, in the case of cargoes with a high surface A1 concentration of 35, the Fe-A:i alloy layer itself becomes hard and brittle, so selective oxidation of A1 takes advantage of dense A1□o3.
Even if a film is formed, there is no risk of thermal shock during injection of molten metal.Fe-A
This is not preferable because one alloy layer may peel off and the service life may be reduced. Also, if the thickness of the Fe-A1 alloy layer is thinner than 0.1w+m, it may not be able to withstand repeated use (which is not practical), considering the cost and effectiveness of forming the he-A1 alloy layer. 0.3-1. (Ig+++ is suitable.

A1 diffusion coating layer formed on the surface layer of the chilled metal in this way,
That is, due to the selective oxidation property of A1 in the Fe-A1 alloy layer, 1 to 30
Produces an extremely thin, dense and strong A1□03 film. This A1□03 film does not form compounds with the molten metal or various components in the molten metal, such as O, so it maintains a high melting point of 2osoc, has extremely poor compatibility with the molten metal, that is, has very poor soaking properties, and has a Fe-A1 alloy layer. Because it is bonded to the metal, there is no peeling due to high impact, etc., and welding of the cold metal is prevented. It is also possible to prevent rusting during storage or embedding in a sand mold, and the formation of scales due to the heat of the molten metal during use. Furthermore, A like this
The formation of A12o3 film by selective oxidation of 1 is Fe-Al
It continues until the A1 performance in the alloy layer drops to 7g, so even if the formed A1□O3 film peels off due to thermal shock, it will be automatically and immediately regenerated by the high heat during use. Therefore, there is no problem with repeated use.

As mentioned above, the surface of the cooling metal of the present invention is always A1□ during use.
Fe-A1 is covered with 03 film and the inside is bonded and continuous.
The alloy layer does not weld to the molten metal, so the pretreatment as mentioned above is not required at all, and the various drawbacks of the conventional cooling metal can be solved by the present invention. All have been resolved.

Now, the case where the chiller according to the present invention is used in a casting mold for @ steel caterpillar shoe, for example, will be explained with reference to drawings 1 and 2. In this case, the lower mold 1, the upper mold 2, and the socket mold 3, the mold 4 of the main body of the shoe is the lower mold 1, and the riser 5
is formed in the upper mold 2, and the sand 8 hardened with a binder is formed so that a hot water lower is formed which leads from the socket 6 through the upper mold 2 and the lower mold 1 to the bottom of the mold 4 of the shoe body. Filled. And, in the place where this mold 40 is attached, a cold metal 9.9 made of a steel round bar whose surface layer is an A1 diffusion coating layer in the vertical direction
is buried in the sand so that a part of its surface is used for agricultural purposes and comes into contact with the bathwater supplied to the mold 4.

Examples of the present invention will be described below for the case shown in this drawing.

Example 1 In order to confirm the effect of the cooling metal of the present invention, the radiused part of the mold for casting of a cast steel caterpillar shoe shown in Figs. The cold metal of the present invention, one coated with resin, and one with surface polishing,
A total of 3 types of cold gold, 4 for each caterpillar shoe.
10 caterpillar shoes were cast in each case.

Casting conditions caterpillar shoe j 60 ran x 300 theory x
600 theory As-cast dimensions Injected molten metal amount: 115 molten metal chemical composition (%): o sIMnpO1200
,450,700,025 8Ni Or M.

O, 0100, 100, 130, 003 injection temperature + 15? OC injection time: 15 seconds A mild steel rod (6 days 41) with an outer diameter of 20 pieces and a length of 80 m was used, and the following three types of chilled metals were used.

1) The contact treatment for forming the chilled metal A1 diffusion coating layer of the present invention was performed by colorizing. i.e. A1# with a small amount of accelerator? The above mild steel rod was buried in an iron box filled with agent A and heat treated to produce F8-A' with a surface A1 concentration of 28 mm and a thickness of 0.6 mm.
An L alloy layer was obtained.

2) Chilled metal coated with resin The above-mentioned mild steel rod was cleaned by shot blasting to remove rust from the surface, and then immersed in liquid resin to cover the entire surface with resin, and then thoroughly dry-recorded before use.

3) Chilled metal with only surface polished The above mild steel bar was used after cleaning the surface by shot blasting.

In all of the casting results, no hot cracks occurred and the cooling effect as a chilled metal was satisfactory, but with the chilled metal of the molten water invention, only one piece was welded and two defects occurred. All castings were in good condition.

The resin-coated cooling metal has fewer welds than the surface-polished one, and the effect of preventing welding is recognized, but it is still not perfect, and only 2 out of 10 cast caterpillar shoes are completely cooled. A gas defect caused by the resin was found in the installation, and repair work had to be carried out in the post-process. Approximately 60% of the cold metal with only surface polishing was welded, and it was necessary to remove the fused parts and finish the surface of the fused parts in the subsequent process, which required a lot of effort. In addition, the surface of some of the caterpillars became rusty during the fourth stage after being cast in the mold.
A gas defect caused by rust occurred in the shoe.

As described above, by using the chilled metal of the present invention, gas defects caused by the chilled metal were eliminated, contributing to improved quality and significantly reducing the number of work steps in the post-process.

Example 2 In order to confirm the service life of the chilled metal of the present invention, four chilled metals coated at the same time were each tested at 50 ml under the same casting conditions as in Example 1.
It was used repeatedly up to the maximum number of times. The coating treatment for forming the Al diffusion coating layer was carried out using the mild steel (SE14
1) After soaking the rod for 5 minutes and coating the surface with A1,
After heating at oooC for 5 hours, an Fe-A1 alloy layer with an outermost A1 concentration of 21% by weight and a layer thickness of 0.4mm and a 6μ thick A1□03 film formed on the top surface was obtained. .

The casting results showed that there was no occurrence of hot cracking, all four pieces were not bath-bonded, they could withstand 50 uses, and there were no casting defects caused by the chilled metal of the present invention. Also, the outermost Al 6 degree of the Fθ-A1 alloy layer is 17.8 fold f coefficient, and the layer thickness is 0.51
Although there were some slight changes, it was confirmed that it could be used satisfactorily as the chilled metal of the present invention.

FIG. 3 shows a photograph of the cross-sectional structure of the chilled metal of the present invention after 50 uses.e The surface layer is an A1 diffusion coating layer made of a Fe--Al alloy layer, and the inside is the base material. As mentioned above, the chiller of the present invention does not require welding and can be used for general purposes, so the amount of chiller consumed can be significantly reduced. In addition, since no scale is generated even when heated by molten metal, there is no need for preliminary treatment using shot planutes, etc., and the recovered material can be reused as is next time, resulting in good work efficiency and no need for equipment for preliminary treatment.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment in which a chilled metal is used in a caterpillar shoe casting FT8 type, and FIG. 2 is a view taken along the X-Y arrow in FIG. 1. FIG. 3 is a photograph of the cross-sectional structure of the chilled metal of the present invention after repeated use 50 times. 4...Mold of caterpillar lash body, 5...Riser,
6...Socket, 7...Gate, 8...Sand solidified with adhesive, 9...Cold metal. Applicant's agent Kiyoshi Inomata → Wa2 Figure

Claims (1)

[Claims] External chiller for steel castings and cast iron castings whose surface layer is an A1 diffusion coating layer.