tailieunhanh - Automobile industry and the use of copper: Part 2

Continued from part 1, part 2 of Automobile industry and the use of copper contains the content: working with copper materials; design notes; application; usage properties. Invite you to consult the document to grasp the content details. | 79 7 Working with Copper Materials Mechanical Processing The mechanical processing of copper and copper alloys is divided into machining and non-cutting treatment. The explanations on processing methods are limited to the further processing of semi-finished products and castings. Non-cutting Treatment 14 26 27 In non-cutting forming distinction is made between cold and hot forming. The formability of a material . the dependence of the yield strength on the previous deformation is described by the flow curve. Here the yield strength is plotted over the deformation degree. To date there is however no test procedure that provides a characteristic figure for the behavior of a material both for cold and hot forming and never will be. Yield strength rises with increasing deformation in the case of cold forming which takes place below the recrystallization temperature. Copper-based materials work-harden by cold forming. On hot forming above the recrystallization temperature work-hardening is immediately extinguished by recrystallization dynamic recrystallization . This means the deformation degree has almost no influence on the resistance against further deformation only the speed of deformation has. Copper and the homogeneous copper alloys with a-mixed crystal such as flbrass maximum 36 Zn copper-tin and other homogeneous copper alloys have good cold forming properties. Pure copper and the material CuZn30 require the lowest energy for cold forming. While for copper-zinc alloys the a-mixed crystal causes good cold formability the -mixed crystal causes good hot formability but is not easily cold formed. The heterogeneous a p brass with Zn contents 37 and other copper alloys . Cu-Al alloys low and unalloyed copper - but not copper-tin alloys - are easily hot formable. 80 7 Working with Copper Materials Forming Sheets and Strips 14 26 27 38 51 All normal processes such as deep drawing stretch-forming ironing pressing bending beading chamfering or .