New method for steel pipe rust removal

The inner and outer wall descaling machine of the steel pipe is a descaling machine for cleaning the inner and outer walls of the steel pipe. The outer surface of the steel pipe is cleaned by shot blasting, and the inner surface is cleaned by shot blasting to remove the scale on the surface. The machine mainly uses the high-speed pill flow thrown by the high-efficiency powerful blasting machine to throw the surface and the inner cavity of the rotating workpiece located in the chamber body, and remove other sticky sand, rust layer, welding slag, oxide scale and its debris. Get a fine, smooth surface. Improve the adhesion of the paint film to the steel surface, and improve the fatigue strength and corrosion resistance of the steel, improve the intrinsic quality of the steel and extend its service life.

The blasting machine selected for this equipment is a unit disk curved blade, which is precisely processed by our application of Dish sand technology, mainly consisting of impeller, main shaft and main bearing seat, cover shell, directional sleeve, splitting wheel, blade, guard Components such as plates, transmissions, motors and bearings. The blasting machine is a unit disk structure, so the inflow performance of the projectile is good, the throwing amount per unit power is large, the impeller body of the blasting machine is close to the spindle end, the structure is reasonable, the arrangement is reasonable and compact, and the maintenance is convenient.

1, the workpiece cleaning sequence

Feeding bracket → Feeding mechanism feeding→Into the shot blasting chamber→Blasting treatment (the workpiece moves forward while rotating) →Send the shot blasting chamber→Unloading mechanism cutting→Unloading bracket

2, the projectile cycle sequence

Projectile storage → Flow control → Shot blasting workpiece → Bucket lift vertical lifting → Pellet separation → (recycling)

Shot blasting machine

Tool rust removal

The steel surface is mainly polished by a tool such as a wire brush to remove loose or raised scale, rust, welding slag, and the like. The descaling of manual tools can reach Sa2 level, and the rust removal of power tools can reach Sa3 level. If the surface of the steel is adhered with strong iron oxide scale, the rust removal effect of the tool is not ideal, and the anchor pattern deep pickling that does not meet the anti-corrosion construction requirements cannot be achieved.

Rust removal level

For the construction process of epoxy, vinyl, phenolic and other anticorrosive coatings commonly used in steel pipes, it is generally required that the surface of the steel pipe reaches near white level (Sa2.5). Practice has proved that the use of this descaling level can almost remove all oxide scale, rust and other dirt, anchor depth of 40 ~ 100μm, fully meet the adhesion requirements of anti-corrosion layer and steel pipe, and spray (throwing) The rust process can achieve near-white (Sa2.5) technical conditions with lower operating costs and consistently reliable quality.

Spray (throwing) abrasive

In order to achieve the desired descaling effect, the abrasive should be selected according to the hardness of the surface of the steel pipe, the degree of original corrosion, the required surface roughness, the type of coating, etc. For single-layer epoxy, two-layer or three-layer polyethylene coating, Mixed abrasives of steel sand and steel shots are more likely to achieve the desired descaling effect. Steel shots have the effect of strengthening the steel surface, while steel sand has the effect of etching the steel surface. Mixed abrasives of steel grit and steel shot (usually the hardness of steel shot is 40-50 HRC, the hardness of steel sand is 50-60 HRC can be used on various steel surfaces, even on steel surfaces with grade C and D corrosion The rust removal effect is also very good.

Pickling and rust removal

Generally, chemical cleaning and electrolysis are used for pickling treatment. Pipeline anti-corrosion is only chemical pickling, which can remove scale, rust and old coating, and can sometimes be used as re-treatment after sandblasting and rust removal. Although chemical cleaning can achieve a certain degree of cleanliness and roughness, its anchor pattern is shallow and it is easy to cause environmental pollution.

Spray (throw)

Spraying (polishing) rust removal is a high-speed motor that drives the spray (throwing) to rotate the blade at high speed, so that the abrasive grains such as steel grit, steel shot, wire segment and mineral are sprayed (throwing) on ​​the surface of the steel tube under the action of centrifugal force. Not only can rust, oxides and dirt be completely removed, but the steel tube can also achieve the required uniform roughness under the action of abrasive impact and friction. After spraying (polishing) and removing rust, not only can the physical adsorption of the surface of the tube be enlarged, but also the mechanical adhesion of the coating layer to the surface of the tube can be enhanced. Therefore, spray (throwing) radiation derusting is the ideal way to remove corrosion from pipelines. In general, shot blasting (sand) descaling is mainly used for the inner surface treatment of pipes, and shot blasting (sand) descaling is mainly used for the outer surface treatment of pipes. There are several problems to be aware of when using blasting to remove rust.

Abrasive particle size and ratio

If the roughness is too small, the adhesion of the coating and the impact strength will be lowered. For severe internal pitting, it is not only possible to rely on large-grain abrasives for high-strength impact, but also to remove the corrosion products by small particles to achieve the cleaning effect. At the same time, reasonable proportioning design can not only reduce the abrasion of the pipes and nozzles (blades). And the utilization rate of abrasives can be greatly improved. Usually, the steel pellet has a particle diameter of 0.8 to 1.3 mm, and the steel grit has a particle diameter of 0.4 to 1.0 mm, of which 0.5 to 1.0 mm is a main component. The sand shot ratio is generally 5-8.

In order to obtain better uniform cleanliness and roughness distribution, the particle size and proportion design of the abrasive is very important. The roughness is too large, which may cause the anti-corrosion layer to become thinner at the anchor peak; at the same time, because the anchor pattern is too deep, the anti-corrosion layer is easy to form bubbles during the anti-corrosion process, which seriously affects the performance of the anti-corrosion layer.