Metal heat treatment is a kind of technology which can heat the metal workpiece in a certain medium to a suitable temperature, and keep it in this temperature for a certain time, then cool it in different medium at different speed, and control its performance by changing the microstructure of the metal material surface or inside. The function of heat treatment is to improve the mechanical properties of materials, eliminate residual stress and improve the machinability of metals.
Metal heat treatment is one of the important processes in mechanical manufacturing. Compared with other processing technologies, Nantong heat treatment generally does not change the shape and overall chemical composition of the workpiece, but endows or improves the service performance of the workpiece by changing the microstructure inside the workpiece or the chemical composition on the surface of the workpiece. Its characteristic is to improve the internal quality of the workpiece, which is generally not visible to the naked eye. Therefore, it is a special process in mechanical manufacturing and an important part of quality management.
Today, let's learn something about the process of producing nodular cast iron and the heat treatment that should be paid attention to in this process.
1、 The content of carbon and silicon in the original liquid iron is higher than that of gray iron, and the content of manganese, phosphorus and sulfur in nodular iron is reduced.
2、 The outlet temperature of nodular cast iron is higher than that of gray cast iron, so as to compensate for the loss of temperature during spheroidization and inoculation.
3、 Spheroidizing treatment is to add spheroidizing agent to the molten iron.
4、 Inoculant is added for inoculation treatment.
5、 Ductile iron has poor fluidity and large shrinkage, so it needs higher pouring temperature and larger pouring system size, reasonable application of riser, cold iron and sequential solidification principle.
6、 Carry out Nantong heat treatment.
1. Annealing: get ferrite matrix, improve plasticity, toughness, eliminate stress, improve cutting performance.
2. Normalizing: obtain pearlite matrix, improve strength and wear resistance.
3. Tempering: obtain the matrix structure of tempered sorbite and good comprehensive mechanical properties, such as spindle, crankshaft, connecting rod, etc.
4. Austempering: to make the parts with complex shape and high comprehensive performance requirements obtain the matrix structure of lower bainite, as well as comprehensive mechanical properties such as high strength, high hardness and high toughness, so as to avoid cracking during heat treatment, such as main shaft, crankshaft, gear, etc.
If you want to produce high-quality products, you must know the above knowledge points. In this way, you can avoid some product defects in order to produce better products.
On 2018-08-08 11:45:46
