Shijian YUAN
,
Gang LIU
,
Xianwei TIAN
,
Z.R.WANG
材料科学技术（英）
In order to reduce high calibration pressure in hydroforming of components with too small radii, a method was proposed to manufacture automotive hollow components with rectangular shape by relatively lower pressure. The process is simulated and analyzed. It is thought that the friction force between the die surface and tube is a main reason that high pressure is needed to form small radii. Using the method proposed in this paper, a petal-like section shape is first preformed so that the central zones of the four sides of the preform section do not contact with the die sides, thus the tube metal is easy to flow into the transition radii area in calibration stage. Moreover, a positive force along the sides is produced by the internal pressure, which is beneficial to overcome the friction force and push the material into the radii. Therefore, the pressure for forming the transition radii is greatly reduced and the components with small radii can be formed with relatively lower pressure. For the experimental case conducted in this paper, the forming pressure is reduced by about 28.6% than the estimated forming pressure.
关键词:
Hydroforming
,
null
,
null
,
null
Shijian YUAN
材料科学技术（英）
To reduce defects, such as the shrinkage cavity and the surface cracks caused by non-homogeneous metal flow in extrusion process, an extrusion method was proposed by using a die with the guiding angle. Numerical simulation and experiment were conducted to investigate the metal flow in this extrusion process. It is shown that the stress state at the bottom of the die is changed. The tendency to generate the dead zone is decreased by employing the guiding angle at the die entrance. The shrinkage cavity is reduced because the non-homogeneous metal flow at the final stage of extrusion is improved. The axial stress is decreased greatly so that the surface cracks caused by additional stress are avoided.
关键词:
Guiding angle
,
挤压
,
金属流动
,
缺陷
Transactions of Nonferrous Metals Society of China
A new process for the hydrometallurgy of refractory gold concentrates was presented. The process comprises grinding-leaching, intensified alkaline leaching (IAL), cyanidation and adsorption. In a stirring-type pulverizing-leaching tower mill, the concentrate is ground to <35. 6 μm of 95. 5 % while simultaneously leached by NaOH of 12 kg/t, then carried out intensified alkaline leaching for 48 h by NaOH of 108 kg/t in enhanced agitation tanks with the pulp concentration of 40% solids at the environmental temperature of 9. 5 &SIM; 13. 5 &DEG;C and the environmental pressure of 10(5) Pa. The oxidation rate of As is 94. 9%, and 47. 6% for S. The total consumption of NaOH is only 20% of that theoretically calculated under the conditions of full oxidation at the same oxidation rates of arsenic to arsenate and sulfur to sulfate. The gold leaching rate by NaCN in 24 h is increased from 9. 2% before pretreatment to 94. 2%. The consumption of NaCN is 7. 5 kg/t, which is one times less than that before pretreatment. The extraction cost of gold is about 422 Yuan/t.
关键词:
refractory gold concentrates;grinding-leaching;intensified alkaline;leaching (IAL);pretreatment;common temperature and pressure
