JP2635769B2 - Manufacturing method of seamless aluminum clad tube - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method of coating a tube (referred to as a core material) on the inner surface or both inner and outer surfaces with a material different from the core material. The present invention relates to a method for manufacturing a seamless aluminum clad tube having features at the same time.

[Conventional technology]

With regard to aluminum pipes for piping conventionally used in car coolers, etc., gas such as chlorofluorocarbon circulates inside the pipe, so that corrosion of the pipe inner surface is not considered important. And the like, the boundary corrosion occurring at the joint with the outer tube has become a problem, and an outer tube clad tube has been used to prevent corrosion of the outer tube surface. However, when a corrosive liquid circulates inside the pipe, in addition to boundary corrosion of the pipe outer surface, corrosion resistance of the pipe inner surface by the corrosive liquid becomes a problem.

On the other hand, conventionally, a double-sided clad tube (ERW) is used in which a clad plate obtained by laminating plates is processed into a cylindrical shape, and then joints are joined by welding. However, this seamed double-sided clad tube has problems such as corrosion resistance at the joint and cracking at the time of bending, and is unsuitable for piping that is severely bent.

As the aluminum clad tube, by coating the outer surface or both surfaces of the core material composed of the 3XXX alloy with the Al-Zn alloy, the sacrificial effect of the Al-Zn alloy and the Zn of the 3XXX alloy as the core material are reduced. There is known one in which corrosion resistance is improved by diffusion. As a method for manufacturing an aluminum clad tube in which a material different from the core material is coated on both the inner surface and the inner and outer surfaces, a method in which a clad plate is processed into a cylindrical shape as described above, and a seam thereof is welded, and a billet is used. Direct extrusion or indirect extrusion is known. However, each has the following advantages and disadvantages.

The electric resistance welded pipe has a stable covering rate as a whole, and there is no air entrapment, but the covering rate of the welded portion is unstable and the workability such as bending is poor. An extruded tube formed by direct extrusion has excellent workability such as bending, but is easy to entrain air, and the coverage in the extrusion direction is unstable. An extruded tube formed by indirect extrusion has not only excellent workability such as bending, but also has a more stable coverage than direct extrusion, but easily entrains air.

[Problems to be solved by the invention]

Conventionally used seam-clad pipes of the electric resistance welded pipe type have seams, and due to cracks during processing such as corrosion resistance and bending at these seams, piping is severely bent and piping etc. that require high corrosion resistance Not suitable for On the other hand, in the case of a seamless inner surface or inner and outer double-sided clad tube by indirect extrusion, an air layer exists between the core material and the coating material, especially the inner surface coating material and the core material at the time of extrusion, so this air is caught in the product and blown. When a billet is heated by high frequency induction heating due to a defective hole, the billet is heated unevenly due to the heat insulating effect of the air layer, so that it is very difficult to establish the manufacturing conditions. Although production is possible by direct extrusion, it has been difficult to obtain a stable coverage over the entire length of the extrusion due to the relationship of the metal flow peculiar to the extrusion.

[Means for solving the problem]

In view of this, as a result of various studies, the present invention has a uniform inner or inner and outer coating layer thickness in the longitudinal direction of the extrusion, and has no defects such as air entrainment and poor adhesion between the core material and the coating material. A method for producing a seamless aluminum clad tube capable of obtaining extremely good surface properties has been developed.

That is, the present invention relates to a method of manufacturing an aluminum clad tube in which a combined billet in which a sleeve made of a material different from that of a core material is covered on the inner surface or both inner and outer surfaces of a cylindrical core material by hot indirect extrusion into a tubular shape is used. It is characterized by uniformly heating with a heating furnace, increasing the outer diameter of the sleeve of the inner surface coating by advancing the mandrel during extrusion, bringing the sleeve into close contact with the core material, and then advancing the hollow stem to extrude the combination billet. Things.

[Action]

In the combination billet, since the heat insulating layer of air exists between the core material and the inner sleeve, uniform heating becomes difficult due to the action of the heat insulating layer in the case of high-frequency induction heating. When the temperature distribution of the billet becomes uneven, the surface properties of the product after extrusion are deteriorated. Therefore, in the present invention, in order to eliminate the uneven heating, the billet is uniformly heated by an ordinary heating furnace, and the temperature of each member is made uniform, thereby improving the surface properties.

The uniformly heated billet is charged into a container while being held in a die and a ram nose. As described above, in the related art, extrusion was performed without removing an air layer existing between the core material and the inner sleeve. Therefore, the air was mixed into the product, and blowhole defects occurred frequently. Therefore, in the present invention, in order to remove this air layer, a mandrel having an outer diameter larger than the inner diameter of the inner sleeve is used, and by advancing the mandrel, the air is forcibly forced on the die side while pushing the inner sleeve with the mandrel and expanding. Discharge more. This unique air discharge prevents air from entering the product,
Improves adhesion between core material and inner sleeve. Thereafter, the hollow stem is advanced while the mandrel is fixed, so that a very high quality seamless aluminum clad tube whose inner surface or inner and outer surfaces are coated with a different material is obtained. This is subjected to a drawing process after extrusion as required to finish it to a desired size.

〔Example〕

A sleeve made of JIS 7072 alloy is used on both the inner and outer surfaces to improve corrosion resistance using JIS 3003 alloy as the core material, and a sleeve (2) for the skin material is provided outside the cylindrical core material (4) as shown in FIG. The combined billet was prepared by covering the inside with the inner sleeve (3), attaching the cap (1) made of JIS 7072 alloy to the front, and fixing the ends by welding. A sleeve thicker than a predetermined thickness was used for the inner sleeve (3).

This was soaked in a heating furnace to 500 ° C., and as shown in FIG. 2 (a), sandwiched between a die (5) and a ram nose (6) and charged into a container (7). With the ram nose (6) fixed, a mandrel (8) having an outer diameter larger than the inner diameter of the inner sleeve (3) is press-fitted as shown in FIG. 2 (6), and the inner sleeve (3) is expanded. The air between the core (4) and the inner sleeve (3) is discharged in the direction of the arrow. When the air between the core (4) and the inner sleeve (3) is discharged as shown in FIG. 2 (c),
The mandrel (8) was fixed in place, then the hollow stem (9), not shown, was advanced and the combined billet was extruded through the die (5) to produce a seamless aluminum clad tube.

The transition of the coating ratio on both sides of this clad tube was examined.
FIG. 3 shows the results. In the figure, (10) indicates the outer coating, (11) indicates the inner coating, and (12) indicates the core. The coating rate (%) was measured every 20 m from the extrusion direction. The change in the rate is indicated by a symbol. The occurrence of blowholes between the core and the inner coating was also investigated. As a result, no brohole was observed at the interface.

JIS 3003 alloy was used as the core material, and JIS 4045 alloy was adhered to both the inner and outer surfaces for the purpose of improving brazing properties. JI for the core material
JIS 4004 alloy was applied to both the inner and outer surfaces for the same purpose using S 6063 alloy. With respect to these seamless aluminum clads and the like, the transition of the coverage ratio on both surfaces and the occurrence of blowholes at the interface were examined. As a result, the same result as above was obtained.

〔The invention's effect〕

As described above, according to the present invention, a seamless aluminum having a very good surface texture having a uniform coating thickness over the entire length of the extruded material and having no defects such as air entrainment and poor adhesion between the core material and the coating material. Industrially remarkable effects such as the ability to manufacture a clad tube can be obtained.

[Brief description of the drawings]

1 (a) and 1 (b) show an example of a billet for the present invention, where (a) is a front view, (b) is a side sectional view, and FIGS. 2 (a), (b) and (c). 3) is a side sectional view showing an air discharging step between the core material and the inner sleeve in the present invention, and FIG. 3 is a graph showing the transition of the coverage of the double-sided clad tube. (1) cap, (2) outer sleeve, (3) inner sleeve, (4) core material, (5) dad nose, (6) ram nose, (7) container, (8) mandrel, (9) hollow stem, (10) Outer coating, (11) inner coating, (12) core material

Claims (1)

(57) [Claims] 1. An aluminum clad tube for extruding a combined billet having a sleeve made of a material different from the core material on the inner surface or both inner and outer surfaces of a cylindrical core material by hot indirect extrusion to form a tube. A seam characterized by uniformly heating with a heating furnace, increasing the outer diameter of the sleeve of the inner surface coating by advancing the mandrel during extrusion, bringing the sleeve into close contact with the core material, and then advancing the hollow stem to extrude the combined billet. Manufacturing method of aluminum-free clad tube.