The Applied Research of Cryogenic Metalworking

在将深冷金属加工应用于板材加工、拉拔和轧制过程中，对周边的设备和工艺，即金属的冷却和搬运条件、模具的材料和结构、加工产品的后处理等进行了研究。板材冲压试验采用10吨级液压压力机进行试验。纯铝和耐蚀铝合金板材在液氮温度(LN)下冷却0.5 mm后，用转移模组以50 mm为间隔进行深冷胀形。通过对金属加工前后温度变化的分析，从理论和实验上阐明了液氮冷却与液氮充气相结合的模具结构是最合适的模具结构。SU 304适用于模具材料。拉丝试验采用纯铜和几种铜合金进行拉丝实验。由于冰润滑，低温拉丝的摩擦系数仅为常温拉丝的1/2~1/3。低温拉丝带来了约10kgf的强化。&lt；mm^(-2)&gt；与常温拉丝的强度比较。这可以用位错的增加和细胞结构的形成来解释。对于沉淀型合金，这有利于降低析出温度。板材轧制采用纯铝、耐蚀铝合金板材在小型二辊轧机上进行轧制试验。通过测量轧制力和前滑移来计算摩擦系数的变化。与常温轧制的强度相比，深冷轧制的强度提高了约10%。这可以用位错的增加和细胞结构的形成来解释。

In applying the cryogenic metalworking to sheet metalworking, wire drawing and sheet rolling, the surrounding apparatus and technology; namely the cooling and carrying conditions of metal, the material and construction of die set, the post-treatment of worked products, etc; are investigated here.1. Sheet metalworkingThe hydraulic press machine having the capacity of 10 ton is used for the experiment. After cooling pure aluminium and corrosion-resistance aluminium alloy sheets of 0.5mm in thickness at the temperature of liquid nitrogen (LN), cryogenic bulging is carried out in the interval of 50 mm using transfer die set. By analysing the change of temperature before and after metalworking, theoretically and experimentally, it is clarified that the most appropriate structure of die set is the combination of die cooling by LN and blowing-up of LN. SUS 304 is useful for die material.2. Wire drawingPure copper and some kinds of copper alloys are used for wire drawing experiment. Frictional coefficient in cryogenic wire drawing is 1/2-1/3 of that in room temperature drawing, as a result of ice lubrication. Cryogenically drawn wires bring the strengthening of about 10 kgf. <mm^(-2)> in comparing with the strength of room-temperature drawn wires. This can be explained by the increase of dislocation and the formation of fine cell structure. For precipitation type alloys, this is useful for decreasing the precipitation temperature.3. Sheet rollingPure aluminium, corrosion-resistance aluminium alloy sheets are used for rolling experiment in using small 2 high mill. The change of frictional coefficient is calculated by measuring rolling load and forward slip. Cryogenically rolled sheets bring the strengthening of about 10% in comparing with the strength of room-temperature rolled sheets. This can be explained by the increase of dislocation and the formation of fine cell structure.