Descaling grade

Descaling grade 4.1

Commonly used for carbon steel pipe, vinyl, epoxy phenolic anticorrosive coatings, such as the construction process, generally require steel tube surface is nearly white level (Sa2.5). Practice has proved that using the descaling grade removes almost all of the scale, rust and other debris and anchor pattern depth of 40 ~ 100 microns, and fully meet the requirements of anti-corrosion layer and steel adhesion, and shot derusting spray (cast) process can be used with low running cost and stable and reliable quality level to nearly white (Sa2.5) technical conditions.

4.2 spray (cast) shot abrasive

In order to achieve ideal cleaning effect, should according to the degree of hardness on the surface of the steel tube, the original corrosion, requirements of surface roughness, coating types to choose abrasive, for single layer, layer or three layer PE coating epoxy, using a mixture of steel shot and steel grit grinding are more likely to achieve ideal cleaning effect. Steel pill have the effect of the reinforcement steel surface, and it has steel grit etching on the surface of the steel. Steel shot and steel grit mixed abrasive (usually for 40 ~ 50 HRC hardness steel shot, steel grit of hardness of 50 ~ 60 HRC can be used for all kinds of steel surface, even in the class C and D corrosion of coating steel pipe surface, cleaning effect is very good also.

4.3 abrasive particle size and proportion

In order to obtain better uniform cleanliness and roughness distribution, ratio of abrasive particle size and design is quite important. Too much of the anticorrosive coating roughness in rush bum thin anchor lines; At the same time as the anchor lines too deep, in the process of anticorrosion coating is easy to form bubbles, serious impact on the performance of anticorrosive coating.

Roughness is too small will cause the loss of coating adhesion and impact resistance strength. For serious internal pitting, not only by the larger particles impact abrasive high strength, must also be polished away by small particles corrosion products to achieve clean effect, at the same time, reasonable proportioning design not only can slow the abrasive wear of pipeline and spray nozzle (blade), and the utilization of abrasive can be greatly improved. Usually, the particle size of steel shot 0.8 ~ 1.3 mm, steel grit size is 0.4 ~ 1.0 mm, with 0.5 ~ 1.0 mm as main ingredients. Sand shot than the average of 5 ~ 8.

It should be noted that in practice, steel shot and steel grit in grinding ratio is very difficult to achieve the ideal, the reason is hard and brittle than steel grit steel shot and broken rate is high. To this end, sampling test should be continuously mixed abrasive in the operation, according to the particle size distribution, to adding new abrasive cleaning machine, and mixing in a new abrasive, the number of steel shot to account for the main.

4.4 rust removal rate

Steel tube derusting speed depends on the type of abrasive and abrasive displacement, generally should choose low attrition rate of abrasive, so clear to improve speed and long blade life.

4.5 cleaning and preheating

Before spray (cast) shoot processing, adopt the method of cleaning to remove oil on the surface of the steel tube and fouling, the heating furnace for preheating tube body a 60 to 40 ℃, the steel pipe surface dry state. In spray (cast) processing, due to steel tube surface oil free of dirt, can strengthen the effect of cleaning, drying of the surface of the steel tube also is helpful for steel shot, steel grit and the separation of rust and scale, make after cleaning of structural steel pipe surface clean.

Emphasis on the importance of surface treatment in the production, strictly control the descaling process parameters, in actual construction, the steel pipe anticorrosion layer of the peel strength value of more than standard requirements, to ensure the quality of the anticorrosive coating, on the basis of the same equipment, improve the technological level, reduce the production cost.