Stainless steel chain plate in high temperature due to the parts of the graphite and lubricant can decompose and produce CO, cause the carburizing, the CO and Cr reaction of chromium carbide in stainless steel wire mesh, and nitrogen in the atmosphere will react with chromium as chromium nitride, the compound of the two compounds are hard brittle, made of stainless steel mesh belt shorten service life.
Net belt in 8 weeks after operation, the band began to rupture due to nitride and carbide, in 314 stainless steel mesh belt, for example, often first as conditioning preheating treatment, commonly known as under 870 ℃ in the flow of air in a normal condition for 28 hours after switching to N2-3% H2, then hold the temperature for 2 hours, then in 14 hours, rising up to 1120 ℃ and the temperature is 8 hours, and then began to sintering parts. About 3 PPM of oxygen is contained in the atmosphere, dew point of about 55 ℃.
Water vapor (i.e., with about 20 PPM). But about eight weeks later, the band started to break. This is due to the thin chromic oxide layer on the surface of stainless steel in the preheating zone is oxidation state, after entering high temperature into a reducing, so the surface oxide reduction, but after entering cooling area, although the atmosphere, but due to lower the temperature, again
Back to oxidation, so that the net again with oxidation, the oxidation and reduction cycle will cause material damage.
Solution is as follows: the mood of dew point to 34 ℃, i.e. moisture is 260 PPM, stainless steel mesh belt in high temperature can still maintain a mild oxidation, surface of oxide reduction. In addition the surface of the decarburization phenomenon occurred.
Here for 870 ℃ to 760 ℃, can avoid the stainless steel, chromium and nitrogen in the air in the reaction and the temperature to 1120 ℃ with the atmosphere there is water, can be on the surface mesh belt Mr Into chrome oxide, thus can avoid chromium and nitrogen reaction. This mesh belt life and longer than when the best of a third time, i.e. for conditioning, adjust atmosphere condition of the service life of 2.7 times. This is because the content of chromium nitride, less grain is bigger, beneficial to creep properties.
In addition to the adjustment of moisture in the atmosphere can also add carbon dioxide, the carbon dioxide can react with hydrogen to form water, carbon dioxide and water is oxygen
Sexual atmosphere, can make the stainless steel mesh belt to adjust its content to maintain in the oxidation of mild condition, the workpiece is still under the reducing atmosphere, but it still can be iron powder surface oxide reduction and improve the bonding strength of the powder, to enhance the mechanical properties of workpieces. Moreover before use of quenched and tempered condition also influence on network, the use of if the preceding conditioning conditions changed in 760 ℃ (870 ℃) was held in the air to flow under temperature 28 hours, and then switch to contain 260 parts per million of water vapour N2-3% H2, the temperature for 2 hours and then in 14 hours to heat up to 1120 ℃, the temperature after eight hours before production.