Chaotic process and requirements for high temperature combustion

2022-06-13

Precision casting is a more traditional casting method. During the machining process, a relatively precise shape and high casting accuracy can be obtained. In the process of processing, it is necessary to make electrodes for the required raw materials, and then form cavities in detail according to the corrosion form of the electrodes, and then perform wax casting by selecting a casting process, so that the original wax pattern can be preserved.
The surface of the fine sand is coated with a layer of high temperature resistant liquid sand. After drying at a temperature above the desired thickness, the inner wax pattern is melted during heating and then ready to be obtained. The cavity is the same as the raw material, then cast iron is poured into the cavity to melt the wax mold compared to solidification. This makes it possible to compare sophisticated products.
Precision casting is a relatively superior casting technology. The products are versatile and suitable for casting processes of various types and alloys. This method allows for more disordered, high-temperature-resistant, difficult-to-machine castings.
In short, precision casting is meltable data. These data can be made into a soluble model. In fact, it can be made into a meltable model. In the painting process, several special coatings can be used for painting. The flame retardant coating is designed to form a complete shell after the product has hardened and dried, and the model is then melted into a shell made of hot water or steam.
In the final step of the finishing process, cast iron is placed in a furnace for high-temperature rough grinding. If a high-strength bowl is used in the casting process, the deformed shell can be baked without molding. After the casting burns, the molten metal is poured to obtain the casting.
The precision casting process requires high precision. Under normal circumstances, it can reach CT4-6. But in the casting process, under normal circumstances, the machining process will be chaotic, thus affecting the size of the casting. There are many factors such as using insert deformation or shortening the mold material.

common problem

Overheating Overheating of the microstructure after quenching can be observed from the rough mouth of the bearing parts. But to accurately judge the degree of its overheating must observe the microstructure. If coarse acicular martensite appears in the quenched structure of GCr15 steel, it is a quenched superheated structure. The reason for the formation may be the overall overheating caused by the quenching heating temperature is too high or the heating and holding time is too long; it may also be due to serious banded carbides in the original structure, forming local martensitic needle-like thick in the low-carbon area between the two bands, localized overheating. The retained austenite in the superheated structure increases and the dimensional stability decreases. Due to the overheating of the quenched structure and the coarse crystals of the steel, the toughness of the parts will be reduced, the impact resistance will be reduced, and the life of the bearing will also be reduced.

chemical heat treatment

Chemical heat treatment is to make the surface of the workpiece infiltrate the atoms of one or several chemical elements, thereby changing the chemical composition, structure and properties of the surface of the workpiece. After quenching and low temperature tempering, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, and the core of the workpiece has high toughness.

surface hardening

Case hardening and tempering heat treatment is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardened layer depth. Vickers hardness tester can be used for hardness testing, Rockwell or surface Rockwell hardness tester can also be used. The selection of the test force (scale) is related to the depth of the effective hardened layer and the surface hardness of the workpiece. There are three durometers involved here. 1. Vickers hardness tester is an important method to test the surface hardness of heat-treated workpieces. It can use a test force of 0.5-100kg to test the surface hardened layer as thin as 0.05mm thick. Its accuracy is yes, and it can distinguish the surface hardness of heat-treated workpieces. small differences. In addition, the depth of the effective hardened layer is also detected by a Vickers hardness tester. Therefore, it is necessary to have a Vickers hardness tester for units that perform surface heat treatment processing or use a large number of surface heat treatment workpieces. 2. The surface Rockwell hardness tester is also very suitable for testing the hardness of surface quenched workpieces. There are three scales for the surface Rockwell hardness tester to choose from. Various case-hardened workpieces with an effective hardening depth of more than 0.1mm can be tested. Although the accuracy of the surface Rockwell hardness tester is not as high as that of the Vickers hardness tester, it has been able to meet the requirements as a detection method for quality management and qualification inspection of heat treatment plants. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement, and direct reading of hardness values. Using the surface Rockwell hardness tester, batches of surface heat-treated workpieces can be quickly and non-destructively tested piece by piece. This has important implications for metalworking and machine building plants. 3. When the surface heat treatment hardening layer is thick, the Rockwell hardness tester can also be used. When the thickness of the heat treatment hardened layer is 0.4-0.8mm, the HRA scale can be used, and when the thickness of the hardened layer exceeds 0.8mm, the HRC scale can be used. The three hardness values of Vickers, Rockwell and superficial Rockwell can be easily converted to each other and converted into standard, drawing or user-required hardness value. The corresponding conversion table has been given in the international standard ISO, American standard ASTM and Chinese standard GB/T.

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