Surface treatment technology for stainless steel products
1. Grinding: It uses manual mechanical grinding, mainly dealing with cutting defects, weld defects, riveting welding joints and various scratches in the process of processing.
2 weld acid pickling: the weld is pickled and passivated, mainly dealing with the black oxide scale on the weld.
3. Integral passivation: Integral pickling passivation, mainly dealing with products with the same overall requirements, but this treatment method is difficult to achieve the desired results.
4 polishing passivation: pickling passivation after manual polishing, mainly for products with decorative surface requirements, but the current treatment methods are difficult to achieve better results, and material costs and labor costs are relatively high.
Problems in the processing of stainless steel products
1. Weld defect: The weld defect is serious, and manual mechanical polishing treatment is used to make up for it, resulting in grinding marks, resulting in uneven surface, affecting the aesthetic.
2 the surface is inconsistent: only pickling and passivation of the weld, but also uneven surface, beautiful appearance.
Scratch is difficult to remove: the whole pickling passivation, also can not remove all kinds of scratches produced in the process, and can not remove the scratches, welding splashes and other impurities adhered to the surface of stainless steel carbon steel, splashes and other impurities, resulting in the presence of corrosive media under the conditions of chemical corrosion or electrochemical corrosion and rust.
4. Non-uniform passivation in grinding and polishing: after manual grinding and polishing, pickling passivation can hardly achieve uniform treatment effect on large workpieces, and can not get ideal uniform surface. And the cost of labor and accessories are also higher.
5 pickling capacity is limited: pickling passivation paste is not omnipotent, plasma cutting, flame cutting and black oxide, it is difficult to remove.
The scratches caused by six human factors are more serious: in the process of hoisting, transportation and structural processing, the scratches caused by human factors such as bumping, dragging and hammering are more serious, which makes the surface treatment more difficult, and is also the main cause of rust after treatment.
7 Equipment factors: Scratches and creases are the main causes of rust in the bending and bending process of profiles and sheets.
Other factors: stainless steel raw materials in the procurement, storage process, due to hoisting, transportation process of the collision and scratch is more serious, but also one of the causes of corrosion.
1 storage, hoisting and transportation
1.1 Stainless steel parts storage: There should be special storage rack, storage rack should be wood or surface painted carbon steel bracket or pad with rubber pad to isolate from carbon steel and other metal materials. Storage location should be convenient for hoisting, and be relatively isolated from other materials storage areas. Protective measures should be taken to avoid pollution of stainless steel by dust, oil and rust.
1.2 Stainless steel lifting: When hoisting, special lifting gear, such as hoisting belt, special chuck, etc., should be used. Strictly prohibit the use of wire rope to avoid scratching the surface; and in hoisting and placing, should avoid impact bump caused by scratch.
1.3 Transportation of stainless steel parts: Transportation tools (such as cars, batteries, etc.) should be used, and should be clean and have protective measures to prevent dust, oil pollution, rust stainless steel pollution. No delay is allowed to avoid bumping or scratching.
2.1 processing area: the processing area of stainless steel parts should be relatively fixed. Stainless steel processing area platform should take isolation measures, such as rubber pads. Setting management and civilized production of stainless steel parts processing zone should be strengthened to avoid damage and pollution to stainless steel parts.
2.2 blanking: cutting of stainless steel parts by shearing or plasma cutting, sawing and so on.
Shear: when shearing, it should be separated from the support, and the hopper should also be covered with rubber pads to avoid scratching.
Plasma cutting: after plasma cutting, the slag should be cleaned up. When cutting in batches, the finished parts should be cleaned up in time to avoid smearing the workpiece by cutting slag.
_sawing and cutting: when sawing and cutting, the clamping should be protected by rubber skin, and the oil stains and residues on the workpiece should be cleaned up after sawing.
2.3 Machining: Stainless steel parts in turning, milling and other mechanical processing should also pay attention to protection, work should be completed to clean the surface of the workpiece oil, iron scraps and other debris.
2.4 Forming: Effective measures should be taken to avoid scratches and creases on the surface of stainless steel in the process of rolling and bending.
2.5 rivet welding: when stainless steel parts are assembled, avoid assembling by force, especially avoid flame baking. Isolation measures should be taken to avoid slag contamination to other stainless steel parts when plasma cutting is temporarily used in the assembly or fabrication process. After cutting, the slag on the workpiece should be cleaned up.
2.6 welding: stainless steel parts must be carefully removed before welding, such as oil, rust, dust and other debris. When welding, argon arc welding should be adopted as far as possible, and manual arc welding should be adopted with small current and rapid welding to avoid swing. It is strictly prohibited to strike arcs in the non welded area, and the grounding wire is properly positioned and firmly connected, so as to avoid the abrade of the electric arc. Anti splash measures should be adopted when welding, for example, whitewash. After welding, stainless steel (no carbon steel) flat shovel is used to clean slag and spatter thoroughly.
2.7 multi-layer welding: when multilayer welding, the slag must be removed. For multilayer welding, the interlayer temperature should be controlled, generally not exceeding 60 C.
2.8 Weld seam: Weld joint should be grinded, weld surface should not have slag, porosity, undercut, spatter, cracks, non-fusion, non-penetration and other defects, weld and base metal should be smooth transition, not lower than the base metal.
2.9 Orthodontics: For stainless steel parts, flame heating should be avoided, especially in the same area. When orthopedic, try to use mechanical devices, or with wooden hammer (rubber hammer) or pad rubber pad hammer, forbid hammer hammer, to avoid damage to stainless steel parts.
2.10 Handling: Stainless steel parts in the process of handling, the use of transport tools (such as trolleys, battery cars or cranes, etc.), and should be clean with isolation and protection measures to prevent dust, oil, rust pollution of stainless steel. It is strictly prohibited to drag directly on the platform or the ground, and it is strictly prohibited to bump and scratch.
3 surface treatment
3.1 Cleaning and grinding: If there is any damage should be grinded, especially with carbon steel contact caused by scratches and splashes, slag cutting caused by damage must be carefully and thoroughly cleaned and grinded.
3.2 Oil and dust removal: Stainless steel parts must be cleaned of oil, oxide scale, dust and other impurities according to the process before pickling and passivation.
3.3 pickling passivation: the pickling passivation of stainless steel parts must be carried out strictly according to the technical requirements, the passivation paste coating should be uniform, the passivation time should be strictly enforced the technical requirements.
3.4 Cleaning and drying: After pickling and passivation, wiping, washing and drying should be carried out strictly according to the process, and pickling and passivation paste and acid liquid should be thoroughly removed.
3.5 Protection: After finishing the surface treatment of stainless steel parts, we should do a good job of protection, to avoid people touching and oil, dust and other debris pollution.
3.6 Avoid Reprocessing: Reprocessing of stainless steel parts or products should be avoided after finishing surface treatment.