制造技术(中英文课件10)

Forging （锻造）
Smith Forging（自由锻造）
The types of operations in this process available are fullering（拔长）, flattening（矫直）, bending（弯曲）, upsetting （镦粗）and swaging（旋锻）.
There are four types of forging methods which are generally used
②Drop forging: This is the operation done in closed impression dies by means of drop hammers. ③ Press forging: the press forging is also done in closed impression dies with the exception that the force is a continuous squeezing type applied by the hydraulic presses（液压机）. ④Machine forging:the material is only upset to get the desired shape.
Fullering
（砧座）
example
No special dies are used, smith forging is more beneficial in the manufacture of small lots（小批量） or in trial production（产品试制）.
Forging （锻造）
Forging （锻造）
Some typical examples of upset forgings
Forging （锻造）
Forging defects（锻造缺陷）
① Unfilled sections ( 截 面 未 充 满 ): some sections of the die cavity(模腔) are not completely filled by the flowing metal. ② Cold shut （冷疤）： This appears as a small crack at the corners of the forging. ③ Scale pits（起磷）：The oxide and scale present on the stock surface. ④ Die shift （模具偏移） ⑤ Flaks ( 白 点 ） ： These are basically internal ruptures( 开 裂 ) caused by the improper cooling of the large forging. ⑥ Improper grain flow ：（不合理的晶粒流向）
Forging （锻造）
Forging types
① Smith forging: This is the traditional forging operation done openly or in open dies（by the village blacksmith or modern shop floor by manual hammeringor by power hammers)
Forging （锻造）
Press Forging（压力锻造）
The metal is shaped not by means of a series of blows as in drop forging, but by means of a single continuous squeezing action. (hydraulic presses). Because of the continuous action of the hydraulic presses. the material gets uniformly deformed throughout its entire depth.
provide draft on forging surfaces which are at right angles to the die movement.
Forging （锻造）
Fillet and corner radii （圆角和转弯半径） When two or more surfaces meet, a corner is formed which restricts the flow of metal. Therefore, these corners are to be rounded off to improve the flow of the metal.
Forging （锻造）
② The other aspect to he considered in the
choice of parting line is the punching of holes.
Forging （锻造）
Draft(倾角) ：Similar to castings, it is necessary to
(Provide the necessary strength for lifting loads)
Forging （锻造）
Example 2
The gear blank（齿轮坯) Without upsetting in Fig (c) The upsetting process provides the radial grain flow In Fig (d) （径向晶粒流向） (essential for good strength in gear teeth （齿轮轮齿） for several applications)
Drawing out （拉拔）：the metal gets elongated with a reduction in the cross- sectional area（金属被拉长， 截面面积缩小）. Upsetting （镦粗）：This is applied to increase the cross- sectional area of the stock at the expense of its length（镦粗是牺牲毛坯长度来增加其截面面积）.
Drop Forging（模锻）
The drop forging die consists of two halves. The lower half of the die is fixed to the anvil of the machine, the upper half is fixed to the ram. The final shape desired in drop forging cannot be obtained directly from the stock in a single pass . The material should manipulated in a number of passes. The various passes used are: ① Fullering impression（拔长膜膛）
② Edging impression（滚挤膜膛）
③ Bending impression （弯曲膜膛） ④ Blocking impression （预锻膜膛） ⑤ Finishing impression （终锻膜膛） ⑥ Trimming （修边）
Rolling (（锻造） 轧制） Forging
Forging （锻造）
Forging Design（锻件设计）
Parting plane （分型面）, the plane in which the two
die halves of the forging meet.
① The parting plane should be the largest cross-sectional area of the forging.
Machine Forging（机器锻造）
Sometimes it is simply called as upset forging. （圆盘类零件， 镦粗为主） Though both drop and press forgings are also done by machines, only upset forging is referred to as machine forging. The beneficial grain flow obtained from upsetting.
Two In forging process，it is possible to control the grain flow in the specific direction（在锻造过程中， 能够控制晶粒流动的具体方向）.
Example 1: The crane hook（吊车吊钩） (drawing out ) The grain without bending in Fig (a) The grain flow is bend along the hook in Fig (b).
Forging （锻造）
Finish allowance （ 精 度 余 量 ） ： The amount of
allowance to he provided should account for besides the accuracy. the depth of the decarburised layer(脱碳 层). Also, the scale pits(铁皮坑) that are likely to form on the component should also be removed during machining.