JPS646871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a stainless steel bottomed container used for water heaters and the like.

Conventionally, a method for manufacturing bottomed containers has been lap welding. In this case, welding is extremely simple, but there is a drawback that a gap is formed on the inner surface of the welded part, resulting in crevice corrosion. In addition, flat butt welding was used to prevent crevice corrosion, but in this case, because the butt is made on a flat surface, there are gaps in the joint, resulting in holes, and the thickness of the welded part is too thick. Since it is thinner than the base metal, it has the disadvantage of being prone to welding cracks.

The present invention solves the above-mentioned conventional drawbacks, and aims to provide a bottomed container that is easy to weld, has high productivity, and has good corrosion resistance by welding base metals.

In order to achieve the above object, the present invention bends the lower end of the body inward to have an L-shaped cross section to form a flange, and forms a bottom plate that fits into the flange in a dish shape to form an outer circumference. a side wall is formed on the bottom plate, the upper end surface of the side wall of the bottom plate projects upwardly from the flange portion, and the side wall of the bottom plate and the end surface of the flange portion are forcibly fitted to form a T-shaped cross section; A welding torch is positioned above the upper end to weld the flange portion and the bottom plate to the base metal to obtain a bottomed container. According to this manufacturing method, the strength of the T-shaped joint is strong; Moreover, since there is little deformation during welding, the base metal can be reliably melted and a bottomed container without holes or welding cracks can be obtained.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In Fig. 1, 1 is a body made of plate material formed into a cylindrical shape and the seam 2 is welded to the base metal by arc welding, and the upper edge 3 is formed outward at the upper end, and the lower end is inwardly shaped into an L-shaped cross section. A bent flange portion 4 is formed. Reference numeral 5 denotes a bottom plate formed by drawing a plate material into a dish shape, and a side wall 6 is formed on the outer periphery, and the diameter of the upper end of this side wall 6 is formed to be slightly larger than the inner diameter of the flange portion 4 of the body 1.

As shown in FIG.
is fitted so as to protrude upward from the upper surface 10 of the holder, thereby forming an abutment portion having a T-shaped cross section.

This dimensional relationship is such that the body 1 and the bottom plate 5 are placed in the recess 12 of the rotating jig 11, the bottom plate pushing jig 13 and the body pushing jig 14 are
is pressed into a fixed position. 15
is a torch of an arc welding machine, and the electrode rod 16 is located above the approximate center of the thickness of the upper end surface 9 of the bottom plate 5. In this state, when the space 17 around the fitting part between the flange part 4 and the side wall 6 is filled with an inert gas such as argon and a voltage is applied to the electrode rod 16, an arc reaches the upper end surface 9 of the side wall 6 and melts it. Furthermore, the vicinity of the end surface 7 of the flange portion 4 is also melted, and the body 1 and the bottom plate 5 are joined to the base material as shown in FIG. At this time, side wall 6
Since the upper end portion 18 flows downward as it melts, the welded portion 19 is formed to be thicker than the base material thickness of the body 1 and the bottom plate 5. Moreover, since the arc from the torch 15 is first generated on the side wall 6, the side wall 6 is located at the arrow A in FIG.
It thermally expands in the direction that it comes into close contact with the end surface 7 of the flange portion 4 and eliminates the gap, thereby preventing the base material from being penetrated and forming a hole.

Furthermore, welding is performed continuously by rotating the rotating jig 11. In this case, as the torch 15 moves away, the welded part 19 hardens rapidly, but since the welded part 19 is a thick molten body, the welded part 19 becomes tensile as the next parts of the body 1 and the bottom plate 5 are heated. Even if it is exposed to water, it will absorb it sufficiently and solidify without cracking.

In general, welding holes occur when the arc leaves the joint, and weld skipping is a welding defect that occurs when the distance between the electrode rod 16 and the joined body changes and the arc stops; however, in the present invention, the electrode rod 16 is located above the upper end face 9 of the side wall 6, so even if the position of the electrode rod 16 is slightly shifted, the arc will not stop because the upper end face 9 has a plate thickness. However, since the upper end portion 18 of the side wall 6 protrudes from the upper surface 10 of the flange portion 4, the arc does not reach the flange portion 4 first. Therefore, weld holes and weld skips are extremely unlikely to occur.

When a plurality of torches 15 are provided, the welding time is shortened, and the bottom plate 5 and the body 1 are heated less, which has the effect of preventing deformation.

In addition, by slanting the side wall 6 of the bottom plate 5 in a direction in which the upper end is located outward, not only is it easier to fit the flange portion 4, but also it is possible to force fit the flange portion 4 and the side wall 6 without creating a gap. This makes it possible to reliably prevent holes from forming. Moreover, during welding, the side wall 6 thermally expands and deforms so as to come into closer contact with the flange portion 4, making welding easier.

Further, by making the bottom plate 5 thicker than the body 1, the amount of protrusion of the side wall 6 from the flange portion 4 can be reduced, and the welded portion 19 can be finished more uniformly due to constant melting flow.

The plate material of the bottomed container used for this type of water heater etc. is made of ferrite stainless steel containing 0.02% or less ultra-low carbon 18% chrome stainless steel, 0.5 to 2.5% molybdenum, and 0.2 to 1% titanium or niobium. If steel is used, the corrosion resistance will not deteriorate due to welding, and the effect can be further enhanced.

As is clear from the above description, according to the present invention, the lower end of the body is formed to have an L-shaped cross section, the bottom plate is formed to be dish-shaped, and the side wall of the bottom plate and the end face of the flange portion are formed to have a T-shaped cross section. Because they are forcibly fitted in a shape, the side wall of the bottom plate will thermally expand during welding, and will be further pressed toward the end face of the flange.
As a result, it is possible to prevent gaps from forming at the joint, and since there is no joint gap, even if the amount of protrusion of the T-shaped part is reduced, the thickness of the melted part of the joint can be made thicker than the original plate. As a result, even highly corrosion-resistant stainless steel plates containing molybdenum or niobium can be reliably welded to the base metal. Furthermore, in the present invention, a plurality of welding torches are positioned at the welding part, and at least the outer surface of the body is held with a jig, so it is possible to further improve the contact of the joint part, and it is possible to It is also possible to reduce the difference in expansion between the body and the bottom plate due to thermal expansion, and as a result,
The stress during cooling and solidification is also reduced, making it possible to prevent the occurrence of cracks. Therefore, it is possible to provide a bottomed container in which welding is simple and reliable, and there are no cracks or holes in the welded portion, and since there is no welding gap, no crevice corrosion occurs, and the container is highly corrosion resistant.

Although the bottomed container in the above embodiment was described as having a round shape, the same effect can be obtained even if the bottomed container is square. A similar effect can be obtained by positioning the torch at

[Brief explanation of drawings]

Fig. 1 is a perspective view of a bottomed container manufactured by the manufacturing method of the present invention, Fig. 2 is a sectional view of a main part showing a state of welding in the same manufacturing method, and Fig. 3 is a sectional view of a main part of a welded bottomed container. It is a diagram. 1... body, 4... flange section, 5... bottom plate,
6... Side wall, 18... Upper end of the side wall.

Claims (1)

[Scope of Claims] 1. The lower end of the body is bent inward to have an L-shaped cross section to form a flange, and the bottom plate that fits into the flange is formed into a dish shape to form a side wall on the outer periphery. The upper end surface of the side wall of the bottom plate is made to protrude upward from the flange portion, and the side wall of the bottom plate and the end surface of the flange portion are forcibly fitted to form a T-shaped cross section. multiple welding torches are positioned on the body, at least the outer surface of the body is held with a jig, the flange portion and the bottom plate are welded to the base metal, and the material of the body and the bottom plate is ultra-low carbon 18% chromium with a content of 0.02% or less. Stainless steel with 0.5-2.5% molybdenum and 0.2-1
A method for producing a bottomed container using a ferritic stainless steel plate containing % titanium or niobium. 2. Incline the side wall of the bottom plate in a direction in which the upper end is located outward, and forcibly fit it into the flange part of the body,
2. The method of manufacturing a bottomed container according to claim 1, wherein the bottom plate has a thickness greater than that of the body.