JPH0741397B2 - Manufacturing method of stainless steel coated cast iron pipe - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a cast iron pipe whose surface is coated with stainless steel.

(Prior Art) A cast iron deformed pipe (hereinafter, referred to as a pipe) may require corrosion resistance on the surface of the pipe. In this case, usually, a stainless steel powder is sprayed on the surface of the pipe by a metal spraying method, and the surface of the pipe is covered with a sprayed layer of stainless material.

(Problems to be Solved by the Invention) However, when forming the above-mentioned sprayed layer, a base treatment is necessary in order to obtain a good bond between the sprayed metal and the tube. Also,
Since the thermal spray layer is porous, there is an air passage extending from the surface of the thermal spray layer to the surface of the pipe, and the surface of the underlying pipe is easily corroded through this. For this reason, there is a problem in that after forming the sprayed layer, a sealing treatment such as coating with a resin must be performed.

Further, it is very difficult to form a thermal spray layer on the inner surface of a pipe having a small diameter (50 mmφ to 300 mmφ) because of the size limitation of the thermal spraying machine (so-called thermal spraying gun).

The present invention has been made in view of the above-described problems, and a manufacturing method capable of easily obtaining a stainless-coated cast iron pipe without subjecting it to a base treatment or a sealing treatment and being influenced by the size and shape of the pipe. The purpose is to provide a method.

(Means for Solving the Problem) The method for producing a stainless-steel-coated cast iron pipe of the present invention is a method of producing cast iron molten metal in a tubular fusible model arranged in a granular material made of only stainless steel powder contained in a mold. After casting, the cast iron pipe is cast when the model disappears.

(Operation) During casting of the pipe, the stainless steel powder disposed adjacent to the surface of the fugitive model is melted by the molten cast iron, and is welded to the surface of the pipe as a coating layer together with the molding of the cast iron pipe. The coating layer is metallurgically integrated with the surface of the pipe, and there is no air passage in the coating layer from the surface of the coating layer to the surface of the pipe. Therefore, the coating layer can exhibit the original corrosion resistance of stainless steel without the need for sealing treatment.

Further, the fusible model is simply placed in a granular material consisting of stainless steel powder, regardless of the size and shape of the fusible model, the stainless steel powder is placed adjacent to the surface of the fusible model. A coating layer of stainless steel can be formed very easily on the surface.

(Example) The stainless steel-coated cast iron pipe of the present invention will be described below according to its manufacturing method.

FIG. 1 shows a mold 1 for casting and molding a stainless steel-coated cast iron pipe according to the present invention. In order to form the casting mold 1, first, an extinguishing model 3 having a predetermined pipe shape and provided with a sprue 6 and a runner model 5 is prepared. As the model, a foamed polystyrene foam is usually used. The model 3 is placed in a stainless steel powder 4 in a mold 2, and the powder 4 is usually filled by vibration to form a mold 1.

As the stainless steel powder 4, a rapidly solidified powder such as a gas atomizing method or a water atomizing method is usually used.

In addition, the particle size of the powder 4 is set to an appropriate particle size (usually 100 to 20 mesh) in consideration of the moldability of the mold, outgassing at the time of pouring, or meltability at the time of forming the coating layer on the tube surface. To be done.

Next, a cast iron molten metal having a predetermined chemical composition is injected from the sprue 6 of the mold 1 shown in FIG.
At this time, the model 3 vaporizes and disappears due to the heat of the molten metal, and the molten metal enters the disappeared portion to form a cast iron pipe having a predetermined shape. On the other hand, the stainless steel powder placed in contact with the surface of the model 3 is melted by the heat of the molten metal and welded to the surface of the pipe as the pipe is formed. The coating layer 8 is formed on the surface. The coating layer 8
As described above, since it is formed integrally on the surface of the pipe 7 in a metallurgical manner, there is no ventilation passage extending from the surface of the coating layer 8 to the surface of the pipe 7, and the pipe is also joined to the pipe. It is good.
Therefore, the original excellent corrosion resistance of the stainless steel material can be exhibited without performing the sealing treatment.

After pouring the molten metal, it is allowed to cool, then the mold is removed, the pipe is taken out, and the black skin on the pipe surface is removed to obtain a cast iron pipe.

In this embodiment, the cast iron deformed pipe is described, but the present invention is not limited to this, and it is needless to say that the present invention can be applied to a general cast iron straight pipe.

Specific examples will be described below.

An extinguishable model made of expanded polystyrene (with a runner) having the same shape as a T-shaped 90 ° bent tube with a nominal diameter of 100 mmφ was prepared.

As shown in Fig. 1, a model of 600mmw × 600mml × 600mmh
A stainless steel (JIS SUS304) powder having a grain size of -30 mesh was placed in the mold together with the sprue, and the mold was assembled by filling the inside of the mold so as to fill the upper surface of the mold.

Inject the molten ductile from the sprue of the mold obtained in
A bent pipe having the same shape as that of the model was cast. At this time,
The pouring temperature was 1522 ° C, and the pouring time was about 5 seconds.

After pouring, leave it for 24 hours to cool, remove the mold,
A cast iron bent pipe having a coating layer made of a stainless material was obtained.

When observing the cross-sectional structure of the curved pipe with a microscope,
It was confirmed that a coating layer made of stainless steel having a thickness of about 0.5 mm was formed by welding on the outer peripheral surface and the inner peripheral surface of the bent pipe. Further, no air passage extending from the surface of the coating layer to the surface of the tube was observed in the coating layer.

(Effect of the invention) As described above, according to the present invention, the tubular fusible model is arranged in the granular material consisting of only the stainless steel powder, so that the surface of the fusible model is irrespective of the size and shape of the fusible model. In this state, the stainless steel powder is placed adjacent to the cast iron pipe, and by casting, a cast iron pipe having a stainless steel coating layer integrally welded on the surface of the casting can be easily obtained, and the productivity is extremely high.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a mold for casting and molding a stainless steel-coated cast iron pipe according to the present invention, and FIG. 2 is an enlarged cross-sectional view of the surface of the cast iron pipe cast by the mold of FIG. 3 ... Disappearance model, 4 ... Stainless steel powder, 7 ... Cast iron pipe, 8 ... Coating layer.

Claims (1)

[Claims] 1. A cast iron pipe is cast into a tubular extinguishing model placed in a granular material made only of stainless steel powder contained in a mold, and the cast iron pipe is cast when the model disappears. A method for producing a characteristic stainless steel-coated cast iron pipe.