As a new surface protection and surface strengthening technology, flame spraying technology has developed rapidly in recent 20 years and has become a very active branch in the field of metal surface engineering. The flame is used as a heat source to heat the metal and the non-metal materials to the molten state, and a mist flow is formed under the high-speed airflow to spray onto the substrate. When the sprayed small molten particles impact on the substrate, plastic deformation occurs, Deposited coating, this process is called flame spraying. In equipment maintenance, it is used to compensate for part surface wear and improve performance.
The self-fluxing alloy material spray coating, re-heated to melt again, the coating density, performance improvement, remelted coating is called spray coating, the process is called spray.
According to the form of spray material, flame spraying can be divided into wire flame spraying, powder flame spraying, bar flame spraying, etc. The form of spray flame can be divided into ordinary flame spraying, supersonic flame spraying and gas explosion spraying.
Advantages and disadvantages
The basic characteristics of flame spraying technology are as follows:
① The general metal, non-metallic substrate can be sprayed, the shape and size of the substrate is usually not limited, but the hole is not sprayed;
② coating materials, metals, alloys, ceramics , Composite materials can be coated materials, the surface can have a variety of properties, such as corrosion-resistant, wear-resistant; high temperature, heat insulation, etc .:
③ porous coating organization has oil lubrication and anti-friction properties, The macro-hardness of the spray coating layer of the phase up to 450HB, spray layer up to 65HRC; ④ flame spray on the substrate effect is small, the substrate surface heating temperature of 200 ~ 250 ℃, the overall temperature of about 70 ℃ ~ 80 ℃, Material organization does not change.
Flame spraying technology shortcomings:
① Spraying layer and the substrate bonding strength is low, can not withstand the alternating load and impact load;
② Substrate surface preparation requirements;
③ Flame spray process by a variety of conditions, the coating quality is still not an effective detection method .
Common flame spraying methods are acetylene-oxygen flame powder coating, acetylene-oxygen flame wire spraying. Acetylene aerobic flame powder spraying equipment used in the simple, on-site construction, suitable for equipment maintenance.
Safety and protection of oxyacetylene flame spraying
1, oxygen bottle pressure regulator is not installed before the oxygen valve should be slightly purged to remove dirt, so as to avoid dust, garbage into the pressure reducer and blockage, resulting in an accident.
2, Do not put oxygen cylinders and acetylene bottles and other combustible gas cylinders together; Where flammable, grease and oil-contaminated items, can’t be the same transport and oxygen bottles.
3, handling oxygen bottles and acetylene bottles, neck bottle should be installed on the protective cap, use, should be placed in a safe place, in order to remove the protective cap on the neck of the bottle. Only use your hand or wrench to unscrew it, prohibit the use of metal hammer percussion, to prevent the occurrence of Mars causing an accident.
4, oxygen decompression table nut in the mouth of the oxygen bottle at least to be screwed 6 to 8 buckle. Screw connector should be tightened, vacuum table adjustment screw should be released.
5, the oxygen bottle, decompression device installed, slowly open the oxygen valve, check the pressure reducer connection oxygen bottle joint leak, the table indicates whether the flexibility to open the oxygen valve, the head and face do not face decompression Table, should be standing on the side or rear of the pressure reducer. Check the leak may not be used when the fireworks or open flames, soapy water can be used to check, do not leak before use.
6, Oxygen bottle mouth is strictly prohibited contact with grease, or oil wrench screw oxygen bottle valve and decompression connecting screw. Do not wear oily gloves, in order to avoid burning explosion.
7, oxygen cylinders, acetylene bottles and pressure reducers should be properly placed before and after use to avoid impact and vibration.
8, the use of acetylene bottles, oxygen bottles should stand upright, and with a fixed bracket to prevent falls.
9, Oxygen bottles and acetylene bottles, flammable and explosive materials or other open flame to maintain the distance of 8 to 10 meters. In some cases, it is indeed difficult to reach 8 to 10 meters, should ensure that not less than 5 meters, but must Strengthen protection.
10, oxygen cylinders do not allow all run out of oxygen, leaving at least 1 to 2 kg / cm 2 residual pressure.
11, winter, such as bottle valve and pressure reducer in case of freezing, you can use hot water, steam or infrared light bulbs to give thawing, non-use of open flame heating.
12, prohibit the use of iron slam gas cylinder ministries, nor pressure screw adjustment table screw to prevent air flow out at high speed, due to local friction and high temperature accident.
13, open-air operation in summer, oxygen bottles and acetylene bottles should be prevented from direct exposure to the hot sun, so as to avoid gas explosion caused by explosion, must be placed in the pergola or covered with a damp cloth.