Mainly explain the role of annealing furnace, annealing furnace working principle.

Annealing furnace is a metal heat treatment process in which the workpiece is heated to a predetermined temperature, held for a certain time, and then cooled slowly. The details are as follows:

1. Improve or eliminate various organizational defects and residual stresses caused by iron and steel in the process of casting, forging, rolling and welding, and prevent workpiece deformation and cracking.

2. Soften the workpiece for cutting.

3. Refine the grain and improve the structure to improve the mechanical properties of the workpiece.

4. Prepare the organization for the final heat treatment (quenching, tempering).

Working principle of annealing furnace:

The temperature distribution in the furnace cavity of the annealing furnace is uniform through the circulation of the fan. The two chambers of the annealing furnace can run independently, which improves the annealing efficiency. There are two fans in each furnace cavity, but there is no air filter device, which is different from the actual situation. The temperature distribution in the furnace is uniform through fan circulation, and the microstructure of the film material is reconstituted through heat treatment to improve the stability and conversion efficiency. The castings are heated to about 950℃ and cooled appropriately after holding for a certain time to eliminate the internal stress of iron and steel castings and welding parts. For iron and steel products after heating began to form austenite temperature below 100 ~ 200℃, after insulation in the air cooling, you can eliminate the internal stress.

Annealing furnace is an important equipment in cold rolling hot dip galvanizing production line. The atmosphere in the furnace directly affects the surface quality of products. At present, the furnace atmosphere requirements for the production of medium and high grade automotive panels are very high, with residual oxygen content below the overall requirement of 10ppm and dew point below -40°C at temperature. The air tightness of the furnace atmosphere depends largely on the furnace itself.

The difficulty of air tightness of continuous annealing furnace is mainly the large, complex and possible leakage range of furnace body. Air tightness inspection should be routine and institutionalized.

1, determine the air tightness of key parts check these key parts generally include:

1) Equipment maintenance position replacement. The furnace body is maintained and part of the tube is inspected as a key component.

2) Top cover, bottom cover, open door, repair of perforation.

3) Entrance seal clearance.

4) Expansion joints and circulation to the shell tube, furnace and heat exchanger flange, flange, flange and welding instruments.

5) Water pyrometer, camera, water cooled heat exchanger.

6) Analyzer sampling tube connector.

2, positive pressure in normal production process, annealing furnace in order to maintain a micro positive pressure of 150-300pa.

1) Judgment of leakage. PPM online oxygen analyzer measurements observe when there is a sudden increase in residual oxygen, which may be a furnace shell or circular pipe leak.

2) Leakage detection methods and tool points. Tool room hydrogen detector. The method is to ensure that the gas in the furnace exceeds 3%, the portable hydrogen detector is checked to verify the gas tightness leakage of the furnace section, and the top welding is a key part of the repair. A hydrogen sensor alarms when a leak is detected.

3, negative pressure suction check that the circulating fan is negative, if the leakage of the negative part, air will be sucked into the furnace.

1) Judgment of leakage. By observing the changes in the measured data of the online analyzer, the leaking blower can be identified.

2) Leakage detection methods and tool points. Through the above method negative pressure leakage detection, negative is positive pressure, and then detected by hydrogen detector, can also be used for vacuum leak detection equipment - helium leak detector inspection.

4, annealing furnace leakage treatment is always in the working state, leakage can take some high temperature sealing method call temporary treatment, a shutdown opportunity to do a thorough treatment.

Welding repair of crack location; The sealing ring is aging or damaged, the ring needs to be replaced; A leak in a component such as an expansion joint is replaced; High temperature sealant tightening bolts loose.

Leakage checkpoint, check the use of tools and annealing furnace air tightness test method is correct, correct treatment, in order to ensure the heating furnace air tightness, improve the furnace atmosphere, the production of galvanized products of high surface quality.