What is steel pipe pretreatment and what is its role?
Steel plate pretreatment before steel pipe production is an important step to ensure the quality and performance of steel pipe, the following is the common pretreatment process:
Steel plates may be deformed after transportation or long-term stacking, affecting subsequent processing accuracy. Therefore, the steel plate needs to be levelled. The leveling can not only smooth the surface of the steel plate, but also make the loose part of the surface oxide peel fall off, which is conducive to the subsequent shot blasting treatment. The capacity of the leveling machine is generally 5mm - 30mm.
The purpose of preheating is to heat up the steel plate before shot blasting, remove the water and part of the oil on the surface, and make the temperature of the steel plate reach about 40℃. The preheating equipment has electric heating wire heating, medium frequency induction heating, liquefied petroleum heating and water heating. Too low temperature is not conducive to the removal of moisture and oil, and is not conducive to the drying of subsequent spraying primer; Too high a temperature wastes energy and may lead to blistering as the paint dries.
Shot blasting is the main method to remove the oxide and rust on the surface of the steel plate, and make the surface of the steel plate produce a certain roughness to improve the adhesion of the coating. The ideal abrasive for shot blasting is steel shot and steel wire section or steel shot and steel sand, with a ratio of 1:1 to 1:2.
After shot blasting, it is necessary to remove the floating rust and dust on the surface of the steel plate. It can be blown with dry, oil-free compressed air, vacuumed, or brushed with a brush. If the surface of the steel plate is contaminated before painting, it should be cleaned again.
In order to prevent the corrosion of the steel plate in the subsequent processing process, it is necessary to spray a layer of workshop primer on the surface of the steel plate. The selection of primer should be determined according to the specific application scenario and requirements. After spraying the primer, it is usually necessary to dry it to ensure that the primer is completely dry.
In the final stage of pretreatment, the steel plate needs to be inspected for quality to ensure that the surface treatment meets the requirements. Check the surface cleanliness, roughness and so on. The surface cleanliness should meet the relevant standards, such as the PSa2.5 level specified in the GB/T 8923.2 standard. The surface roughness value should reach Rz40μm ~ Rz70μm, and the surface roughness value of thick paste type heavy anti-corrosion coating and metal thermal spraying should reach Rz60μm ~ Rz100μm.
After pretreatment and quality inspection, the steel plate can be packed into the warehouse and wait for the subsequent steel pipe production process.
These steps ensure that the surface of the steel plate is clean and smooth before entering the steel pipe production process, and has good anti-corrosion properties and processing properties.
