What kind of polishing process does the stainless steel surface treatment have

Stainless steel surface treatment is common stainless steel anodic oxidation, stainless steel galvanized, stainless steel chromium plating, stainless steel electroless nickel plating process, but because of stainless steel in the production process, inevitably need to go through annealing, normalizing, quenching, welding and other processing processes, the surface often produces black oxide skin. Oxide scale not only affects the appearance quality of stainless steel, but also adversely affects the subsequent processing of the product. Therefore, pickling, passivation, polishing and other surface treatment methods must be used to remove it in the subsequent pretreatment of electroplating.

Common polishing has mechanical polishing, chemical polishing, electrochemical polishing 3 kinds.

I. Mechanical polishing

Mechanical polishing refers to polishing and batch finishing with polishing wheel, polishing belt, etc. Batch finishing is by means of polishing agent in the abrasive polishing on the surface of parts, so that the surface smooth, to achieve polishing effect. After polishing, the mirror brightness with surface roughness below 0.4um can be obtained.

Parts of simple shape can be polished with hard polishing wheel or polishing belt, and parts of complex shape can be polished with soft polishing wheel. Large batch of small parts with batch decoration method. Batch light decoration and drum rolling light, vibration motor vibration light decoration, centrifuge centrifugal light decoration and rotating light decoration and other methods.

Mechanical polishing of the surface grinding amount is very small, difficult to polish the rough surface. At this time, it is necessary to be polished in advance, with a grinding wheel, with a grinding paste for grinding, coarse grinding, grinding and fine grinding. The surface roughness can reach 0.4um after fine grinding.

In order to achieve some other requirements, such as peeling, deburring, welding slag, extinction and other purposes, sometimes also for sandblasting, shot blasting and with steel wire wheel brush light and other surface treatment, with stainless steel wire wheel polishing surface can better avoid iron pollution.

2. Chemical polishing

Chemical polishing is to immerse the parts in the appropriate solution, because the solution to the convex part of the surface than the concave part of the solution to dissolve faster, so that the surface leveling, to achieve the purpose of polishing. Generally speaking, the polishing ability of chemical polishing is poor, and only a small amount of brightness can be improved. But compared with mechanical polishing, save labor and time, and can polish the inner surface of small parts. Recently, it has been reported that the surface of 18 -- 8 austenitic stainless steel can be polished to mirror by adding brightener. But note the following.

(1) After chemical polishing, the active surface must be passivated to ensure corrosion resistance.

(2) For a large number of small parts such as brackets and screws, mechanical stirring should be adopted to make polishing uniform.

(3) When polishing the large surface of stainless steel clad plate and other products, especially pay attention to keep the polished surface wet, and should be fully washed after polishing to prevent uneven surface brightness.

3. Electrochemical polishing

Electrochemical polishing can improve the reflective property of parts. Improved corrosion resistance; Reduce the surface hardness of machined parts; And reduce the friction coefficient by reducing the surface roughness. Electrochemical polishing can also be used to remove burrs from objects.

Compared with mechanical polishing, electrochemical polishing has the following characteristics:

(1) Mechanical polishing will produce surface hardening layer and abrasive inclusion, reducing the corrosion resistance of stainless steel, while electrochemical polishing will produce passivation surface, increasing the corrosion resistance of stainless steel.

(2) Electrochemical polishing has certain requirements on the substrate, such as uneven metallographic structure will produce uneven polished surface, and deep scratches can not be polished smoothly. Mechanical polishing is much less demanding on the substrate.

(3) Electrochemical polishing is much easier than mechanical polishing for complex parts, wires, thin plates and small parts.

(4) Electrochemical polishing is more efficient than mechanical polishing, but large workpiece can not be placed in the polishing tank, and requires a particularly large current, it is difficult to electrochemical polishing.

(5) The current density on the surface of the electrochemical polishing workpiece must be uniform, and a pictographic cathode should be used when necessary, otherwise the surface brightness is not uniform.

(6) When the electrochemical polishing current is relatively large, the fixture and the workpiece need to have a large enough contact area and good contact, otherwise local overheating will burn the workpiece.

(7) Certain austenitic stainless steel polishing process can not be used to polish martensitic stainless steel, easy to produce corrosion.