Tips for vacuum brazing problem

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a) The product is not melted

1.Phenomenon and reasons: It refers to the fact that a small part of the product in the furnace is not melted during the normal process of brazing, which is called the product is not melted.

2.Solution: Unmelted products mainly include:

(1) The operator’s door or door is not closed or not closed properly.

(2) The aluminum silicate fiber felt lining the furnace wall flows down, and the nickel sheet is damaged.

(3) The temperature measurement of the thermocouple is inaccurate.

(4) The brazing process is unreasonable.

(5) The number of incoming furnaces is not as specified.

b) The product turns black after brazing

1.Phenomenon and reasons: other reasons such as vacuum furnace sealing or operation during the brazing process. The product turns black after being baked. There are two main types of blackening, high temperature blackening and low temperature blackening. High temperature blackening means that it is called high temperature from cooling to 1080 at the end of the temperature rise from 1080 to 1120. From 1080 degrees self-cooling to 850 strong cold to 80 is called low temperature.

There are two reasons for blackening: (1) During the brazing process, a certain part of the furnace (such as the door, the upper door, the electrode sealing ring safety valve, etc.) is not sealed. (2) When the positive and negative pressure is inflated, the nitrogen pressure is not up to the requirement or there is no normal gas supply, resulting in blackening.

2.Solution: After blackening, it can be turned white. The process is as follows: 1060 heat preservation for 35 minutes, it can be solved. But if the high temperature turns black, it depends on the degree of seal leakage. The degree of loss of brazing copper flux, if the loss of copper flux is serious, the product will be scrapped. However, the vacuum leakage time is short and can be solved by re-welding, but the re-welding process temperature must be 5 degrees higher than the previous heat, and the re-welding process temperature time curve is specified.

c) Sudden gas stop during normal brazing

1.Phenomenon and cause: During normal brazing, the inner air pipe or air pump fails. After the gas is stopped, the valves of the gas pump are automatically closed, and the vacuum passage is automatically closed.

2.Solution:

(1) The operator first boarded the brazing vacuum furnace in the high temperature section.Above each valve, directly pull each valve stem to a suitable height position by hand. Lining with iron bars or woodworking. At the same time, restart the mechanical pump and the Roots pump at a time (two people must operate), and operate according to the operation regulations to prevent oil return.

(2) Fix the lower door trachea stack so that the lower door slowly falls down.

(3) Use the same method to solve the vacuum furnace at low temperature.

(4) After the gas supply is normal, the lower door is judged according to the gas stop time, and the time of lowering is appropriate to increase the time of the high temperature section of brazing. If the gas is stopped in advance, notify, you can put a 29.2 welding mold on each valve in advance. After the gas is stopped in this way, the 29.2 welding die supports each valve. Vacuum shield can continue brazing. So according to the above method. In the brazing natural cooling, the effect of the gas is little. However, in heating or high temperature, the operator must judge and select the operation according to the exhaust time.

d) Emergency method for stopping circulating water

1.Phenomenon and reasons: The circulating water supply is suddenly stopped due to the water pump and other reasons

2.Solution: You must immediately go to the pump room to find out the reason when the tensioner sounds after the circulating water stops. When the water cannot be supplied for 3 to 10 minutes, the diesel engine must be turned on to supply water or the main water valve must be turned on to supply water.

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