Because the large diameter seamless steel pipe diameter sizes is too large, in addition to the less efficient large hot extrusion unit and large pipe jacking machine outside, we can no longer use the familiar automatic pipe mill or continuous pipe mill and other models for direct production. Thus emerged pull Dial expanding, expanding top push and rotate the three main Seamless expanding expanding process. Currently most of the world are produced in large diameter seamless steel technology three and pull Dial and top push expanding process has been applied to some large -diameter welded steel pipe production, and become part of the composition of its processes.
Pull Dial expanding process
Pull Dial Flaring machine produced in the 1930s in Germany, then to Italy, France adopted and in Italy to perfect, which is currently the world's only six units and relatively obsolete technology. To 630 units, for example CSST; several thousand tons equipment, hundreds of millions of investment, annual output of 50,000 tons. The production process must first be heated thermal expansion material as the tube end valgus cone, for fixing the tubular body. Then the overall heating tube, with a chain pull has been set into the inner mold raw tube and fitted mandrel, complete flaring. Its characteristics: high production efficiency, longer processed finished products, equipment can be reduced flaring necking multi- wall, but the equipment weight of large infrastructure investment is large, deformed steel pipe flaring continues in tension, resulting in poor product quality, external Drive low precision steel surface is not smooth, as the removal of low end valgus cone timber defects caused more prominent.
Rotate expanding process
Expansion of the machine, also known as rotary disc flaring equipment. Its name comes from its cross- tilt placed two large-diameter disk-shaped rolls similar to the device once expansion ratio of up to 70 %, which is currently the world's largest amount of time expanded diameter pipe expansion models. The device is in a 1990s Italian oblique roller mill developed on the basis adapted from. So far only four sets of the world, only Italy Dalmine unit for the most successful cases, thousands of tons of equipment over a billion construction investment, sophisticated technology, despite its high production efficiency, deformation speed, a large flaring, so that the industry is still daunting . However, if the Department were equipped machine, sizing machine composed of expanding production lines, for a large number of large -diameter pipe production is not a good solution for the vector.
Pushing expanding process
This model was invented in Germany in the 1950s, the mid-1980s to elbow pushing machine models from Japan into China. To 1997 and renovated in China perfect obtaining intellectual property, and named two -step expansion of the machine hydraulic pusher, the device is simple in principle to the hydraulic push plate will cover only the fixed cone with expanding mandrel outside the hot feed pipe pushed through flaring cone will complete the expansion work. Expanding mandrel process only occurs in the raw material tube and associated fixed connections between stress lines therefore very short. And because of the fixed plate and cylinder mandrel mandrel tube billet between the forces, this device stiffness structure greatly simplified. Two step forward in turn reduce the length of the hydraulic cylinder nearly half, so a greater extent, reduce the equipment cost and mainly from the process solution to the cylinder machining length limit. The expanding device complete with frequency heating equipment, rapid and uniform heating of raw materials controllable, uniform propulsion deformed pipes are refined microstructure and mechanical properties of materials to improve the performance guarantee uniformity of the tube to create the conditions, although the device has less investment, short construction period, simple equipment, product quality, high geometric accuracy, finished product rate, etc.
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