Composite protective coating of sink roll for hot dip plating and preparation method

Abstract

The invention discloses a complex protective coating of a sink roll used for hot dip coating and a preparation method. The complex protective coating comprises a bottom layer, a transition layer and a working layer; the bottom layer is a CoCrW coating, the transition layer is a coating of a mixture formed by CaO-SiO2 and CoCrW according to a proportion, and the working layer is a CaO-SiO2 coating; and a thermal expansivity relation among the coatings and a thermal expansivity relation among the coatings and a roll body are set. Coating is performed on the bottom layer by means of high velocity oxygen-fuel equipment, coating is performed on the transition layer and the working layer by means of plasma spraying equipment, corresponding technological parameters are set in the coating forming processes, and accordingly the complex protective coating on the surface of the sink roll is obtained. According to the complex protective coating provided by the invention, through design on the coating structure, good thermal expansion matching between the complex protective coating and base metal of the roll is achieved, and the purpose that the complex protective coating can be applied to practical production stably in a long term is achieved; and the preparation method is easy to operate, and the complex protective coating on the surface of the roll can be prepared and obtained.

Description

technical field [0001] The invention relates to a composite protective coating of a sinking roller for hot-dip plating and a preparation method thereof. Background technique [0002] At present, most anti-corrosion steel products need to be hot-dip galvanized. Hot-dip galvanizing technology has become the most economical and effective method for steel anti-corrosion. Hot-dip galvanized sheet has good corrosion resistance, processing formability, weldability, Paintable and environmentally friendly, it is widely used in many manufacturing fields such as construction, home appliances, vehicles and ships, containers, and electromechanical. [0003] In the continuous hot-dip galvanizing production line, the zinc liquid is highly corrosive to all parts in the zinc pot, especially the sinking roll, whose surface condition is very important and directly affects the surface quality of the steel plate. In actual production, due to the corrosion of components by zinc liquid and the we...

AI Technical Summary

Problems solved by technology

However, since the temperature of the molten high-aluminum zinc solution is as high as 550-650°C, which is 100-200°C higher than that of ordinary hot-dip pure zinc (about 450°C), it is more corrosive. Traditionally used WC-Co, Thermal spray coatings such as WC-Co-Cr and Fe-Al can no longer effectively resist the corrosion of zinc-aluminum solution, which greatly reduces the service life of the sinking roller

Therefore, the short service life of sinking rolls and stabilizing rolls has become a bottleneck factor restricting the efficient production of hot-dip high-aluminum zinc sheets

[0006] In order to increase the service life of the sinking roll and improve the quality of the strip steel, there have been attempts at various coatings in the early stage, such as WC-Co, MoB-CoCr, etc., but the results are not satisfactory.

WC-Co will decompose when it exceeds 540°C, so it can no longer be used in high-aluminum zinc-zinc pots; although MoB-CoCr has good protection performance, in actual use, zinc sticking to the roll surface is still serious, which affects the quality of the strip steel. come a big impact

And the reusability of the coating is poor, and the actual use cost is very high

The newly developed CaO・SiO 2 The coating has good anti-adhesion properties, but due to its low thermal expansion coefficient, it has a poor match with the base metal of the sinking roll and the stabilizing roll (CaO-SiO at 20-700 °C 2 The coefficient of thermal expansion of the coating is 6.5×10 -6 / K, the coefficient of thermal expansion of the metal base material of the sinking roll and the stabilizing roll is 18.9×10 -6 / K), so the coating is very prone to stress cracking or peeling, and it is difficult to meet the long-life service requirements of the roller

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