JPS61172625A - Production of exhaust pipe of three layers structure - Google Patents

Abstract

PURPOSE:To produce the exhaust pipe of three layers structure with good working efficiency by filling up the intermediate material of slurry state in the gap between the inner tube and outer tube, by performing the bending of the inner and outer tubes at the stage when the intermediate material becomes in a hard rubber state and by performing a baking treatment thereafter. CONSTITUTION:The inner tube 1 of a ferritic stainless steel, for instance, is inserted with providing a gap into the outer tube 2 of the same steel and fixed by inserting a wire mesh ring 3 into one end of the outer tube 2. The intermediate material 5 of slurry state, for instance, those which is made in slurry state with blending a ethyl silicate 40 with the powders of Al2O3, SiO2 is filled up in the gap between the inner tube 1 and outer tube 2 thereof. The bending of the inner and outer tubes is performed at the stage when the intermediate material 5 becomes in a hard rubber state and the three layer structure exhaust pipe is produced with performing a sinter treatment thereafter.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a three-layer exhaust pipe used in automobiles and the like.

(Prior Art) A three-layer exhaust pipe conventionally used in automobiles and the like has a structure in which a gap is provided between an inner tube and an outer tube, and an intermediate material having heat insulating properties is inserted into the gap. When molding such an exhaust pipe into a product shape, a molding filler is inserted into the gap between the gates of the inner and outer tubes, the bending process is performed, and after the molding, the filler is taken out and the intermediate material is then inserted. Was. When inserting the above-mentioned molding filler, methods such as (1) filling the voids between the inner and outer tubes with sand grains or iron balls, (2) injecting a low melting point alloy and solidifying it, and (3) injecting water and freezing it. was taken.

(Problems to be Solved by the Invention) However, all of the above methods require a step of removing the filler after bending, which poses a problem in terms of work efficiency.

The object of the present invention is to provide a method for manufacturing a three-layer exhaust pipe, which is filled with an intermediate material from the beginning and then bent and formed without using a shaping filler.

(Means for Solving the Problems) In order to achieve the above object, the present invention fills a gap between an inner tube and an outer tube with a slurry-like intermediate material, and makes the intermediate material have a hard rubber-like shape. This method of manufacturing a 3W exhaust pipe is characterized in that the inner and outer pipes are bent in a step, and then fired.

(Example) The present invention will be described below based on drawings showing examples of products to which the manufacturing method of the present invention is applied. In the figure, 1 is an inner tube, and 2 is an outer tube. For example, the inner tube 1 is made of ferritic stainless steel with a plate thickness of 1.5 am, and the outer tube 2 is made of the same steel material with a plate thickness of 1.6 mm. A wire mesh ring 3 is inserted into one end of the outer tube 2 to maintain a gap of about 4 mm between the inner tube 1 and the outer tube 2. The wire mesh ring 3 is made of austenitic stainless steel. Further, the outer periphery of the inner tube 1 is covered with a wire mesh 4 made of stainless steel, as shown in FIG. This is to allow the inner tube 1 and outer tube 2 to slide in order to release the difference in thermal expansion between the inner tube 1!1 and the outer tube 2 when used as an exhaust pipe. Next, as shown in FIG. 3, the gap between the inner tube 1 and the outer tube W2 is filled with an intermediate material 5 in the form of slurry (mud-like investment material). Slurry intermediate material 5
is Al2O3, SiO2 powder or A I 203
．． Alcohol, water and acid are added to MQO, ZrO2 powder to make it easier to fill and dry, and ethyl silicate 40 is blended as a binder.

It is also possible to use these short fibers instead of the above powder. When the slurry-like intermediate material 5 gels and becomes hard rubber, the wire mesh ring 3 is stuffed into the upper end of the outer tube 2, and as shown in FIG.
(not shown) into the desired shape. After this,
It is fired at 650 to 850°C in a heating furnace (not shown). After firing, one end of the outer tube 2 is squeezed as shown in FIG. 1, and the inner and outer tubes 1 and 2 are welded. Leave the other tube end free;
Allow it to slide during thermal expansion. Seven lunges 6 are attached to both ends of the inner pipe 1 to complete the exhaust pipe.

(Effects of the Invention) As explained above, the present invention is a manufacturing method for a 3m exhaust pipe in which an intermediate material is filled from the beginning and bent and formed without using a molding filler, so the manufacturing process is efficient. This has the effect of improving work efficiency.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view of a 311 structure exhaust pipe manufactured by the manufacturing method of the present invention, and FIGS. 2 to 4 are longitudinal sectional views of a three-layer structure exhaust pipe at each step. 1... Inner tube 2... Outer tube 5... Intermediate material

Claims (1)

[Claims] Filling the gap between the inner tube and outer tube with a slurry-like intermediate material,
A method for manufacturing a three-layer exhaust pipe, characterized in that the inner and outer tubes are bent when the intermediate material becomes hard rubber, and then fired.