Operating Instructions of "Yafei Net Belt" Net Belt

Yangzhou Yafei Machinery Manufacturing Co.， Ltd.

Operating manual of mesh belt

1. Cleaning method of mesh belt;

The mesh belt must be cleaned before use， and there must be no oil pollution， otherwise the mesh belt will contaminate materials after being put on the machine， especially in the food industry. In the high-temperature furnace industry， the oil pollution on the mesh belt surface will volatilize， causing the furnace atmosphere to change and affecting the atmosphere composition. The cleaning mesh belt can be wiped with gasoline or degreasing agent or added into the sink with degreasing powder， with a concentration of 1%-5%， heated to 50-60 degrees， soaked for 40 minutes and rinsed with clear water. If the mesh belt is dense and it is difficult to clean the internal oil stain， in the production process， split and clean， soak the spiral strip and the threading strip in the cleaning tank for 40 minutes before assembly， and then assemble after cleaning and rinsing，

Second， the installation method of mesh belt

When installing the mesh belt， it is necessary to adjust the idler until the mesh belt does not deviate and runs smoothly before feeding. When the mesh belt runs at high temperature or heavy load for a period of time， it will be elongated， which needs to be cut off in time. When the mesh belt is butted again， it only needs to put on the thread and weld the head. In general， under high temperature environment， such as powder metallurgy， heat treatment and brazing industries， the elongation of the mesh belt will be longer， and the period will be cut off once every 2 weeks to one month. Some users will dig a column-shaped pit at the end of the furnace， and the growing part of the mesh belt can be in the pit. Prevent the growing part from affecting the operation.

3. Application skills of powder metallurgy sintering mesh belt in high temperature operation

Powder metallurgy sintering mesh belt， the general mesh belt in operation after 8 weeks， due to nitridation and carbonization lead to the belt began to break. Take the traditional 314 stainless steel mesh belt as an example， it is usually treated by quenching and tempering preheating， that is， operating at 870 ℃ in flowing air under normal conditions for 28 hours， then switching to N2-3% H2， then holding the temperature for 2 hours， then gradually heating up to 1120 ℃ within 14 hours and holding the temperature for 8 hours， and then starting sintering parts. At this time， the atmosphere contains about 3ppm of oxygen and the dew point is about-55 ℃. (I. E. containing about 20ppm of water vapor). But after about 8 weeks， the tape began to break. This is because the thin chromium oxide layer on the surface of stainless steel is oxidized in the preheating zone， and becomes reducing after entering the high temperature zone， so the surface oxide is reduced. However， after entering the cooling zone， although the atmosphere is the same， it becomes oxidizing again due to the decrease of temperature， so that the mesh belt is oxidized again， and this oxidation and reduction cycle will lead to material damage.

In addition， in the high temperature zone， the graphite and lubricant in the parts will decompose to produce CO， which leads to carburization. This CO reacts with Cr in the stainless steel mesh to form chromium carbide， and the nitrogen in the atmosphere will also react with chromium to form chromium nitride. These two compounds are hard and brittle compounds， which shorten the service life of the stainless steel mesh belt.

The solution is as follows: If the dew point of the atmosphere is raised to 34 ℃， that is， the water vapor is 260ppm， the stainless steel mesh belt can still maintain slight oxidization at high temperature， and the oxides on the surface will not be reduced. In addition， there is no decarburization on the workpiece surface.

In addition to the above-mentioned adjustment atmosphere of water gas can also add carbon dioxide， this carbon dioxide will react with hydrogen into water， this carbon dioxide and water are oxidizing atmosphere， adjust its content can make stainless steel mesh belt in a slightly oxidized state， but the workpiece is still in a reducing atmosphere， so it can still reduce the surface oxide of iron powder to improve the bonding strength between powders and improve the mechanical properties of the workpiece.

In addition， the conditioning conditions before use also have an impact on the net. If the aforementioned conditioning conditions are changed to 760 ℃ (originally 870 ℃) and kept in flowing air for 28 hours， then switched to N2-3% H2 containing 260ppm water vapor， kept for 2 hours and then raised to 1120 ℃ within 14 hours， and kept for 8 hours before starting production.

The reason here is that the chromium in stainless steel can be avoided from reacting with nitrogen in the air when the temperature is reduced from 870 ℃ to 760 ℃， and when the temperature is raised to 1120 ℃， chromium oxide can be formed on the surface of the mesh belt because of water vapor in the atmosphere， so the reaction between chromium and nitrogen can be avoided. At this time， the service life of the mesh belt can be prolonged by 1/3 of the time compared with that in the aforementioned * * * state， that is， 2.7 times of the service life without quenching and tempering and without adjusting atmosphere. This is because the content of chromium nitride is less and the grain size is larger， which is beneficial to the latent property.

IV. Matters needing attention in the use of brazing furnace mesh belt

Generally， the high temperature zone of brazing furnace mesh belt reaches about 1130 degrees， and it is woven with imported high temperature resistant materials. In the process of use， brazing material cannot adhere to the mesh belt， especially copper brazing material cannot penetrate into the mesh belt. The furnace is generally cleaned once every 3 months to half a year to clean up the brazing slag and impurities in the furnace. Once there is more copper leakage， the high temperature will volatilize， and the mesh belt is easier to oxidize. The mesh belt will also contact copper material for a long time in the furnace， and the solder adhered to the mesh belt will be cleaned in time. Otherwise， after the furnace is at high temperature， CU will come into contact with oxygen， copper oxide will be produced， the mesh belt will be oxidized， the metallographic structure will change， and the mesh belt will crack easily. Once it cracks， it will tear a bigger hole. The mesh belt is tightly woven， and it is difficult to repair after high temperature deformation. Some users will lay a mesh on the mesh belt to cut off the direct contact between copper leakage and mesh belt. Replace the screen in time.