3.7 The direct-discharge gas furnace is adopted.

Direct-discharge gas furnace directly discharges the combustion products into the curing furnace. If impure gas is used, the small molecular carbonized products formed during incomplete combustion will adhere to the surface of the cured coating, forming an "oil film". If it is not removed during back spraying, it will directly cause the adhesion failure of the back spraying coating. In addition, if some indirect exchange gas stoves are not properly maintained (such as gas leakage), the combustion by-products may be attached to the coating surface, resulting in the loss of adhesion during later re-injection.

3.8 Compatibility between coatings

Due to different indexes such as reactivity and viscosity of resin used, or different batches of sand grain coatings from the same manufacturer, there may be matching problems due to different formulas (some batches may consume stock powder, powder to be inspected or even recycled powder). If the sand grain powder from different manufacturers or a different batch of powder is used during back injection, it is very likely that delamination will occur during back injection. The preventive measure is not to easily change the paint supplier or sand grain powder before entering the factory or before using it, to test the adhesion of back spray in small batches.

3.9 The back spray coating is thick.

When the back spray coating is thick, with the increase of viscosity and coating rigidity and the gradual formation of adhesion to the substrate, the cohesion increases and remains in the coating. After curing, the stress between coatings varies greatly, and the coatings will naturally fall off when subjected to external force.

4. Correct operation process of back sandblasting grain powder

Polyester powder coating for aluminum profile is a thermosetting powder coating. Because there is no chemical bond between the two sprayed coatings when spraying reworked materials, it is easy to delaminate only by mechanical force. According to the actual production experience of spraying workshop, correct management measures and quality inspection should be adopted when spraying back to ensure the adhesion of the sprayed coating.

Distinguish between good and bad aluminum profiles

6063 alloy is an alloy with Al-Mg-Si as the main element, each element has a certain content, and the price of magnesium is high. In order to reduce the cost, some manufacturers reduce the amount of magnesium to the minimum allowable content. Some even worse, the content of magnesium is lower than the minimum allowable content.

Other factories add waste wires and waste pots and waste aluminum pot to the alloy, which is basically far from 6063 alloy. As a result, the mechanical strength of aluminum profiles is very low, which can be so low that it is easy to bend with both hands, commonly known as "noodles". This is one of the reasons why aluminum profiles can be several thousand yuan cheaper.

Regular aluminum profile manufacturers have internal standards when preparing alloy components, that is, within the range of various elements, each factory has its own smaller variation range, and the ratio between aluminum, magnesium and silicon is very strict, and each factory has its own data and keeps it confidential.

Only the alloy made of qualified formula can guarantee the quality, otherwise, the quality will not be improved in the future.

Aluminium alloy smelting furnac

It is also very important how to melt the prepared 6063 alloy and what furnace to use. At present, the furnaces used in China are 40' s level and 90' s level, and the worst manufacturers use the original crucible furnace. There are coal-fired, oil-fired, gas-fired and electric-heated smelting furnaces.

Some stoves have chimneys, while others have no chimneys. Generally, most square furnaces (rectangular furnaces) are used, the advanced ones are round furnaces, and some round furnaces can pour aluminum water obliquely. On aluminum melting furnaces with tonnage of one ton, two tons, five tons, ten tons, twenty-five tons and fifty tons. More advanced, a static furnace is added below the aluminum melting furnace, which is important for preparing 6063 alloy. Slag can be removed and degassed in this furnace, and then aluminum bars can be cast for extrusion.

The quality of alloy prepared in the original coal-burning furnace is absolutely different from that in the modern circular furnace.

Generally, no matter what kind of fuel is burned, there should be a chimney, and most of the waste gas and waste residue produced during the combustion of fuel can be discharged from the chimney.

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