What are the spring oxidation treatments:
A dense protective film is formed on the surface of the spring, and oxidation treatment and phosphating treatment are usually used. Oxidation treatment and phosphating treatment have low cost and high production efficiency. General spring manufacturers use oxidation treatment as anti-corrosion treatment. .
The oxidation treatment of oxidized steel is also called bluing, blacking, and boiling black. After oxidation treatment, protective magnetic iron oxide is formed on the surface of the spring. This oxide film is generally blue or black, and sometimes dark brown. Its color determines It depends on the surface state of the spring, the chemical composition of the spring material and the oxidation treatment process.
The methods of oxidation treatment include: salty oxidation method, alkali-free oxidation method and electrolytic oxidation method. Alkaline oxidation method is mostly used.
The alkaline oxidation method is to put the spring into a sodium hydroxide solution containing an oxidant at a temperature of about 140°C for a certain period of time. The oxidant and sodium hydroxide react with iron to generate sodium ferrite and sodium ferrite, and then react with each other. This produces magnetic iron oxide.
The thickness of the oxide film layer is about 0.6~2μm. Although the oxide film can improve the corrosion resistance of the spring, because the film is thin and has pores, its protection ability is poor and can only be used in non-corrosive media. The spring working in the middle. The level of its anti-corrosion performance depends on the density of the oxide film and its thickness, which is also determined by factors such as the concentration of sodium hydroxide, the concentration of the oxidant, and the temperature of the solution.
In order to improve the corrosion resistance and lubricating ability of the oxide film, the treatment before and after the oxidation treatment should be strengthened. Before the oxidation treatment, the rust, oxide scale, oil stain, heat-treated salt residue, surface contact layer, etc. on the spring surface must be thoroughly removed. After that, the spring is usually filled in a soap solution or dichromate, and then washed with running warm water, blown dry or dried, and finally replaced with a water film to replace the anti-rust oil or a certain temperature of mechanical oil for immersion Oil treatment.
Oxidation treatment erodes the surface grain boundaries of some hot-rolled spring materials, which will reduce the fatigue strength to a certain extent.Therefore, caution should be taken when using oxidation treatment.
The traditional oxidation treatment requires heating. In recent years, some domestic manufacturing units have used room temperature blackening agents, which overcome the defects of traditional blackening processes and save a lot of energy.
The blackening agent is a concentrated liquefaction of blue-green, no impurities, no peculiar smell, non-flammable, non-explosive, non-corrosive, and safe to transport. The blackening agent is diluted with water, and the commonly used dilution ratio when the spring is blackened is about 1:5.
The operation process of the blackening agent is relatively simple, and the process route is: degreasing, rinsing, acid washing, rinsing, blackening (2~5min at room temperature), rinsing, and water film replacement anti-rust oil. It should be noted that: Remove the oil on the spring workpiece and clean it before putting it in a room temperature agent for oxidation treatment.
The oxidation treatment cost is low, the process formula is relatively simple, the production efficiency is high, and the oxide film has a certain degree of elasticity, which basically does not affect the characteristic curve of the spring. Therefore, the oxidation treatment is widely used as the anti-corrosion and anti-corrosion treatment of formed coil springs, spring washers and leaf springs. Decorative measures.
The quality inspection of the spring after oxidation treatment includes visual inspection and corrosion resistance inspection.