The phase transition temperature of tin bronze sheet from α→α+ ε is about 320 ℃, that is, the heating temperature is higher than 320 ℃, the structure is single-phase structure, until heated to 930 ℃ or so liquid phase structure, considering the use of equipment, the degree of oxidation of the workpiece after heating and the actual processing of the workpiece after heat treatment and other properties. The heating temperature is too high, the workpiece oxidation is serious. The temperature is too low, the workpiece strength and elasticity is high and the toughness is obviously insufficient, not suitable for forming.
Due to the large amount of furnace, in order to make it dithermal and obtain a certain strength and toughness, in order to facilitate the subsequent bending processing, each furnace workpiece to the temperature needs to hold about 2h, then can be empty cold treatment, can also leave the workpiece in the tempering barrel slowly cooling. Generally, the processed workpiece can be identified simply by two methods. One is to observe the color of the workpiece, that is, the processed workpiece from the original copper color to blue color, due to oxidation and on the surface of the workpiece to produce 2 ~ 3μm thick oxide layer, easy to fall off.
Second, the workpiece can be directly processed by hand bending to discriminate. When bending, if feel that the workpiece has a certain strength and elasticity, but also can bend, then the annealing effect is good, suitable for forming processing. On the contrary, the strength and elasticity of the workpiece after treatment are higher, and it is not easy to bend by hand, indicating that the annealing treatment effect is poor, and it needs to be annealed again.
In order to achieve the purpose of uniform temperature and oxidation, tin bronze sheet material workpiece is generally not suitable for processing in the box furnace without stirring fan. For example, under the condition of the same amount of furnace, the workpiece is treated in the box furnace without stirring fan and the well furnace with stirring fan respectively.
The tin bronze sheet workpiece treated by box-type furnace has different luster, high strength and insufficient toughness, which is difficult to be bent and processed. After the well furnace treatment of the same batch of workpiece, the luster is uniform, the strength and toughness are suitable, which is conducive to the subsequent processing operations.
Post time: Oct-11-2022