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Mosten Alloy Co., Ltd.

Processing of molybdenum alloy

  • Mosten
  • 8 May

Plastic processing is not only the forming method of molybdenum alloy, but also can improve the strength and low temperature plasticity of molybdenum alloy. Molybdenum and its alloys can be produced by conventional plastic processing methods such as sheet, strip, foil, tube, bar, wire and profile. The characteristic of molybdenum alloy material processing is that each process of hot deformation has obvious influence on the final performance of the product. Molybdenum oxidizes rapidly above 600 ℃ and volatilizes and appears liquid phase at 725 ℃, so molybdenum and its alloys are usually protected by hydrogen or other reductive atmosphere when heated. Because the contamination layer of molybdenum is very thin, it is easy to be washed by molten alkali, so the hot processing can be carried out under atmospheric conditions, but it is suitable for rapid processing. The cold working of molybdenum and its alloys should be carried out above the temperature of plasticity-brittleness transition. The ingot billet of molybdenum and its alloy is mainly produced by powder metallurgy process, but also by melting process. Generally small size billets use powder metallurgy technology, large size billets can be both adopted. What kind of process is adopted depends on the requirements for the performance of the final product. The suitable density of powder metallurgy billet is about 93% of theoretical density. The melting of molybdenum and its alloys in industry is mainly by vacuum consumable arc melting and electron beam melting. Ingots with coarse grains can only be processed after extrusion and opening of the ingots. Extrusion is used to crush coarse as-cast grains, improve the processing properties of ingots, and can also be used to produce pipes, bars and profiles. In order to fully break the as-cast grain, the extrusion ratio should not be less than 4, and the extrusion temperature is usually between 1100 ℃ and 1315 ℃. If products and intermediate products are obtained directly by extrusion, greater extrusion ratio and higher extrusion temperature should be adopted. In order to prolong the die life and ensure the size and surface quality of the product, zirconia or aluminum trioxide refractory coating mould should be used and lubricated with glass lubricant during extrusion. Forging includes rotary forging and ordinary forging. Rotary forging is mainly used to produce bar and drawing wire billet with diameter of 2.5 mm or more. The blank is 10 mm 30 mm square sintered strip. The open forging temperature of pure molybdenum rotary forging is usually about 1400 ℃, and the pass deformation is about 10% and 30% respectively. With the decrease of the diameter, the forging temperature gradually decreases, and the diameter of 3 mm can be reduced to about 800 ℃. For ordinary forging, hammer forging is more suitable than press forging. Large size billets and large forgings can be obtained by ordinary forging. The open forging temperature of pure molybdenum is about 1400 ℃, while the open forging temperature of extruded billet can be lower. Free forging should be safe to prevent work pieces or fragments from flying out of harm.

Rolling for plate, strip, foil and bar production. The initial rolling temperature of the billet produced by rolling melting-extrusion is generally between 1200 ℃ and 1250 ℃, and the initial rolling temperature of the billet supplied by powder metallurgy is usually about 1400 ℃. In order to reduce the non-uniform deformation, the pass deformation should be between 20% and 40% during the initial rolling, and the total deformation of the rolling after each heating should be about 75%. When the total deformation is more than 85% (the thickness of the plate is about 6 mm), the rolling temperature can be reduced to 700 μ 900 ℃, and the rolling temperature can be reduced to 200 μ 400 ℃ when the thickness of the plate is 1? 2 mm. According to the plasticity-brittleness transition temperature of the material, the thickness of the cold rolled sheet is 0.5 mm. Cross rolling can be used to improve the anisotropy of the product. In order to obtain enough work hardening and improve low temperature plasticity, the suitable cold working amount of the final product should be about 70%. Pipe processing molybdenum pipe mainly ingot or sintered ingot as extruded tube billet, temperature processing technology, by rolling, drawing or spinning into a variety of pipe. Small diameter molybdenum tubes are produced by warm rolling in China. The initial rolling temperature is about 650 ℃ and the final rolling temperature is about 350 ℃. The processing rate of warm rolling pass is between 20% and 35%, the maximum is more than 40%. For molybdenum tubes with a diameter of 8 mm and a wall thickness of 0.5 mm, the rolling tube can be up to 6500 mm in length. The hot rolled molybdenum tube has good inner and outer surface, good plasticity at room temperature, and can be further drawn into capillary. Thin-walled tubes with larger diameters are generally produced by extrusion or sintering of tube billets and then spinning. Recrystallization annealing and stress relief annealing are generally used in heat treatment. Recrystallization annealing is used in extrusion, forging and hot rolling. Stress-relieving annealing is intended to eliminate work hardening. The plasticity-brittleness transition temperature of the material is increased due to recrystallization annealing, which is not conducive to the next processing. Generally, the processed products are delivered and used in the state of stress-relieving annealing.