For aluminum alloy large-caliber seamless pipes, the current production methods are generally forward kneading and reverse kneading. The reverse kneading is divided into horizontal double-drive kneader and back kneading. Kneading by vertical die forging press.

When the horizontal kneading machine produces pipes, the output is high, but because the tooling of the kneading cylinder, the kneading shaft (or large needle) is replaced in a messy and time-consuming manner, it needs to be warmed up for a long time together. Production. For the tube that is kneaded in the forward direction, although the length of the extruded tube is long, there are also problems such as uneven arrangement of the front and rear ends of the tube, thick inter-rings, large wall thickness differences, and misalignment. The kneading of the pipe in the reverse direction has improved the functional difference between the front and rear ends of the pipe, but the length is limited by the length of the kneading shaft.

At the beginning of this century, the foundry of Southwest Aluminum (Group) Co., Ltd. first developed the back-kneading process for large-sized aluminum alloy pipes. It produced 12500 tons of horizontal kneading on a6000-ton vertical free-standing casting hydraulic press . The Φ800mm tube produced by the kneader Φ500mm can produce the aluminum alloy pipe with a diameter of more than Φ500mm, which reduces the production cost, shortens the production cycle, and satisfies the urgent needs of the defense industry.

Because of insufficient attention to the protection of skills and trade secrets, the skills and tooling drawings of large-scale aluminum alloy pipes produced by Southwest Aluminum's vertical casting press quickly spread to all parts of the country, making anti-kneading into different domestic standards (particularly Large diameter pipe), the primary production method of small batch pipe.

Using a vertical casting press to knead the produced pipe in reverse, in addition to the length constraints of the headroom of the press and the travel of the beam, it also requires mechanical processing due to poor surface quality, resulting in increased production costs and extended production cycles. But also because of the need for mechanical processing, after all, the appearance quality and dimensional accuracy of the pipe given to the user can be well ensured, and the user can use it without going back.

In addition to the traditional uses in the fields of national defense industry and petrochemical industry, aluminum alloy pipe has been strengthened with the emphasis on environmental protection. Because of its outstanding corrosion resistance, aluminum alloy pipes will play a role in the development and application of new energy represented by natural gas and hydrogen. VIP.

Take the 6061 aluminum alloy liner carbon fiber full-circle gas cylinder as an example to clarify that it has a general function compared to steel gas cylinders, and the operating pressure has greatly improved (now the national standard is 35Mpa, Japan has reached 70Mpa). Gas storage is added, and the weight is reduced by about 50%, with better corrosion resistance, insulation, shock absorption and safety. The production methods are mainly the following two:

● Aluminum alloy sheet → punched into discs → multiple deep drawing + annealing → spinning closing → heat treatment → anodizing treatment on the inside and outside → carbon fiber surrounding layer.

● Aluminum alloy pipe → spinning molding → spinning necking → heat treatment → anodizing treatment of internal and external surfaces → carbon fiber surrounding layer.

Compared with the deep-drawing production process of sheet slice, direct spinning production with pipe has higher output power and stable product quality. Although the cost of pipe material is higher than that of sheet metal, but after summing up the subsequent processing cost, production power, quality cost and other factors, the final production cost may be almost or slightly lower.