Extrusion characteristics of nickel-based alloy

The production of pipes is often extruded. From the international point of view, there has been a deep research on the extrusion of soft metals such as Mg, Al, Cu, etc. In about 1797, the British Braman was designed. The world’s first mechanical extruder for lead extrusion has been patented. From the late 1950s to the early 1980s, advanced countries such as Europe, America, and Japan promoted the rapid development of aluminum alloy pipe extrusion processes for construction, transportation, power, and electronics. In 2005, the world’s extruded aluminum production was about 11 million tons (approximately considered as consumption), about 2012 extrusion plants with a production capacity of around 18.5 million tons. In 1930, hot extrusion of steel occurred in Europe. However, due to the use of lubricants such as grease and graphite, the lubricating properties were poor, and there were fatal weaknesses such as many defects in the extruded product and short tool life. The extrusion of steel has really been greatly developed and applied to industrial production after the invention of the glass lubricant in 1942.

Production process of nickel base alloy pipe

The nuclear steam generator heat transfer tubes are seamless tubes. Because the seamless tubes are integrally formed and have no welded joints, their pressure resistance and corrosion resistance are much better than welded tubes and become the preferred tube for pressure pipes.

Superalloy seamless pipes are not like ordinary steel pipes, and their alloying degree is high, which brings a series of difficulties to processing, making it more difficult to make seamless steel pipes. Due to the narrow temperature range and poor thermoplasticity, the tube blanks are prone to cracks or even breaks during thermal perforation, which directly reduce the feasibility of hot perforation to produce high-temperature alloy seamless tubes. Production practice also shows that the production of high-temperature alloy tubes using the above-mentioned hot-rolled seamless steel tubes basically does not meet the performance requirements of the tubes. Through scientific research and production, scientists and engineers from all over the world have mastered the hot processing feature of high-temperature alloys and the influence laws of various processes, and combined with the production experience of seamless steel pipes, proposed to produce waste pipes by drilling and squeezing. Then, through the multi-pass cold rolling and cold drawing combined with the intermediate heat treatment process, each of the high-temperature alloy seamless tubes is produced, and a good effect blank is obtained by drilling and reaming to obtain the capillary tube, and then hot extrusion to produce the waste pipe. The molding function is equivalent to the perforation function and the partial extension function in the hot-rolled seamless steel pipe production, and the multi-stand cold continuous rolling has the function of continuing the extension molding.

For the nickel-based corrosion-resistant alloy seamless pipe, it is difficult to obtain a good production effect, firstly because the nickel-based alloy has a high degree of alloying and a slow heat transfer, which results in uneven temperature distribution of induction heating during reaming; Secondly, the deformable temperature of the nickel-based alloy is very narrow, which requires the extrusion of the waste pipe to be carried out at a high temperature and high speed, and the high-speed extrusion causes an increase in the unevenness of the performance of the product, which is liable to cause a large number of defects; The hardness is relatively large, the resistance during processing is very large, the requirements for the extrusion die are high, and at the same time, the energy consumption is large. These all determine that the production of nickel-based superalloy seamless pipes has many unique characteristics, and it is necessary to have corresponding process specifications to achieve controllable production of pipe quality.

The production of high-temperature alloy seamless pipe generally includes the following steps: tube-drilling-induction heating-reaming-induction heating-hot extrusion-solid solution cold milk/cold drawing-heat treatment->cold milk/cold drawing-heat treatment- Quality Inspection. The results of large-scale trial production and preliminary research indicate that the processes that have a greater impact on the quality of the finished pipe are induction heating reaming, hot extrusion, cold rolling (pulling) and heat treatment.