Production method of composite bimetal pipe

[0017] The specific embodiments of the present invention will be described below in conjunction with the drawings.

[0018] According to the mechanical performance requirements of the composite bimetallic pipe, carbon structural steel pipes with different carbon content are selected as the outer pipe 1. The outer tube of this embodiment is a 10-steel round tube with an outer diameter of 25 mm and a wall thickness of 2.5 mm. According to the requirements of corrosion resistance, choose different corrosion-resistant metal tubes as the inner tube 2. For the inner tube of this embodiment, a T2 round copper tube with an outer diameter of 19 mm and a wall thickness of 0.5 mm is selected. The inner diameter of the carbon steel tube is slightly larger than the outer diameter of the copper tube, which makes it easy to insert the copper tube into the steel tube.

[0019] The production process of the embodiment of the present invention is as figure 1 , 2 Shown:

[0020] (1) Treatment of the inner surface of the carbon steel outer pipe

[0021] ① Clean the carbon steel round pipe in a metal cleaning agent tank to remove the grease on the inner surface, and then rinse it with water.

[0022] ②Put the grease-removed carbon steel pipe into a pickling tank of 10-15% hydrochloric acid aqueous solution for pickling to remove the internal surface oxide scale, rinse with clean water, and dry.

[0023] ③ Brush the inner surface of the carbon steel round pipe to thoroughly remove the oxide on the inner surface.

[0024] (2) Treatment of the outer surface of the copper pipe

[0025] ① Clean the copper pipe in a metal cleaning agent tank to remove the grease on the outer surface, then rinse it with water and dry it.

[0026] ② Brush the outer surface of the copper pipe to thoroughly remove the oxide on the outer surface.

[0027] (3) Diameter expansion and pultrusion of suit and inner tube

[0028] Insert the copper pipe into the steel pipe, and use the pipe expansion drawing method to expand the copper pipe to remove the gas between the inner and outer pipes and make the copper pipe close to the inner wall of the steel pipe to form an interference fit to obtain a composite pipe blank .

[0029] (4) Filling liquid and sealing the end

[0030] The steel plug 3 is pressed into one end of the composite tube blank, and the end gap 4 is welded and sealed.

[0031] The liquid medium is selected according to the nature of the corrosion-resistant inner tube material. In this embodiment, for the copper tube, water is selected as the liquid medium. Determine the amount of water added according to the volume of the tube cavity and the pressure requirement during diffusion annealing. Put water 5 into the copper tube, and use the same method to seal the other end of the composite tube.

[0032] (5) Diffusion annealing

[0033] In this embodiment, the composite tube is heated to a temperature of 500-900°C (60-85% of the melting point temperature of copper 1084+273K), the liquid 5 turns into a gas 6, and a pressure is generated in the tube, which is sufficient for the diffusion annealing temperature The lower metal joint surface produces a small amount of plastic deformation; under the combined action of internal pressure and temperature, holding for 10 to 60 minutes, the copper pipe and the steel pipe interface will be metallurgically bonded through the diffusion process between metal atoms.

[0034] (6) Post-processing

[0035] Perform end treatment, surface treatment, size adjustment and other post-treatments on the bimetallic tube after diffusion annealing.