Do you know flame spraying? What is the combustion method of flame spraying?

       Wire flame spraying

 

      Wire flame spraying is a thermal spraying method that uses an oxygen-acetylene combustion flame as a heat source and the spraying material is welding wire. This is the first thermal spray method applied,

It is still widely used to this day.

 

1. The principle of spraying

 

      The heating and atomization of the spray material is carried out by means of a flame spray gun. The spray gun introduces acetylene, oxygen and compressed air through a siphon head, respectively. After acetylene and oxygen are mixed, in the nozzle

Combustion flames are produced at the exit. The wire feed roll continuously brings the wire into the flame through the center of the nozzle, where it is heated and melted. compressed air passes through

The conical high-speed airflow of the cap and atomize the molten wire into fine particles. Driven by a flame and a high-speed airflow, the molten particles are sprayed onto the surface of the pretreated substrate

On the surface, a coating is formed.

 

      The amount of molten wire per unit time depends on the flame power. Oxidative or neutral flames can be obtained by changing the flow ratio of oxygen and acetylene. Oxidizing flames intensify gold

Burning of carbon in filaments and increase of oxides in coatings. A neutral flame can reduce oxidation of the sprayed material to some extent.

Compressed air separates and atomizes the molten metal. General compressed air consumption is 0.8-1.2m3/min; pressure is 0.40-0.60MPa.

 

      The wire delivery relies on an air turbine or electric motor in the gun, and the wire feed rate is controlled by adjusting the rotational speed. Compact gun with air turbine

And light weight, suitable for manual operation. However, it is difficult to fine-tune the wire feed rate and is susceptible to compressed air and difficult to keep it constant. with

Motorized guns can easily adjust the wire feed speed and keep it constant, so this type of gun is used more and more.

The diameter of the wire used for spraying is usually between Φ1.6mm-Φ4.8mm. The spray gun is equipped with different types of nozzles and air caps to meet the spraying requirements of different diameters and materials

beg.

2. Equipment composition

 

The composition of a typical flame wire spraying equipment, including oxygen-acetylene supply system, compressed air supply system, wire coil rack, spray gun, etc.

 

(1) Oxygen-acetylene supply system. The system consists of gas source, pressure and flow regulating device, flashback preventer and gas pipeline. Most of the gas sources are bottled oxygen and acetylene.

The oxygen pressure reducing valve and acetylene pressure reducing valve used for pressure regulation should be purchased from regular manufacturers and checked regularly, and can be used only after they are qualified. Float flowmeter is used for flow control, and the needle valve should be sensitive,

To be accurate, the value used should be between 40-70% of full scale. A flashback prevention valve must be installed between the spray gun and the flow meter to ensure the safety of the spraying process.

 

(2) Compressed air supply system. In order to ensure the quality of the coating, the compressed air supplied to the sand blower and spray gun must be clean and dry, that is, without oil, in addition to the requirements of flow and pressure.

Anhydrous. Therefore, the compressed air supply system should include an air compressor and an air purification device.

 

(3) Spray gun. At present, there are two main types of spray guns used in China: one is the domestic type, the most representative is the SQX-1 air spray gun, and the other is the imported spray gun, mainly the original American Metco

The company's 12E and 14E flame wire spray guns use air turbine wire feeding. The pneumatic part has high machining accuracy, stable wire feeding speed, wide speed adjustment range, and high and low melting points.

Materials can be sprayed.

 

3. Coating and process technology characteristics

 

(1) Coating structure and characteristics. The coating structure of wire flame spraying is an obvious layered structure, and there are many pores and oxide slag inclusions in the coating. Coating properties depend on spray process and spray

Materials vary, general data are listed in the table below.

2. Equipment composition

 

The composition of a typical flame wire spraying equipment, including oxygen-acetylene supply system, compressed air supply system, wire coil rack, spray gun, etc.

 

(1) Oxygen-acetylene supply system. The system consists of gas source, pressure and flow regulating device, flashback preventer and gas pipeline. Most of the gas sources use bottled oxygen and acetylene for pressure regulation

The oxygen pressure reducing valve and acetylene pressure reducing valve should be purchased from regular manufacturers and calibrated regularly, and can only be used after passing the test. Flow control adopts float flowmeter, needle valve should be sensitive and accurate, and the use value should be within

Between 40-70% of full scale. A flashback prevention valve must be installed between the spray gun and the flow meter to ensure the safety of the spraying process.

 

(2) Compressed air supply system. In order to ensure the quality of the coating, the compressed air supplied to the sand blower and spray gun must be clean and dry, that is, without oil and water, in addition to the flow and pressure requirements.

Therefore, the compressed air supply system should include an air compressor and an air purification device.

 

(3) Spray gun. At present, there are two main types of spray guns used in China: one is the domestic type, the most representative is the SQX-1 air spray gun, and the other is the imported spray gun, mainly from the original Metco company in the United States

12E type and 14E type flame wire spray gun, this type of spray gun adopts air turbine wire feeding, its pneumatic part has high machining accuracy, stable wire feeding speed, wide speed adjustment range, and can be sprayed with materials with high and low melting points.

 

3. Coating and process technology characteristics

 

(1) Coating structure and characteristics. The coating structure of wire flame spraying is an obvious layered structure, and there are many pores and oxide slag inclusions in the coating. Coating properties depend on the spray process and the difference in the spray material.

The same but different, general data in the table below.