Defects arising during stainless steel processing and their prevention

During the processing of stainless steel, various defects are inevitable. Let's introduce these defects and their impacts. The first one is weld defects, which are quite serious. This can be remedied by using manual or mechanical grinding methods, but it will leave grinding marks, making the surface of the stainless steel uneven and affecting its appearance. Additionally, if only the welds are acid-washed and passivated, it will also result in an uneven surface of the stainless steel. 

Common defects also include scratches. Even if the stainless steel undergoes overall acid washing and passivation, various scratches formed during the processing cannot be removed. Moreover, impurities such as carbon steel and splatters adhering to the surface of the stainless steel due to scratches or welding splashes cannot be eliminated. This will cause the stainless steel to be prone to rusting under the condition of corrosive media due to chemical or electrochemical corrosion. Additionally, it is difficult to remove the black oxide scale produced by plasma cutting and flame cutting during the acid washing and passivation of stainless steel. 

There is also unevenness in the grinding and polishing process of passivation. After manually grinding and polishing the stainless steel material and performing acid washing passivation treatment, it is difficult to achieve a uniform and consistent treatment effect for larger workpieces, and it is hard to obtain an ideal uniform surface. Moreover, the labor cost and other auxiliary material costs are also relatively high. 

There are also severe scratches caused by human factors: During the lifting, transportation and structural processing stages, factors such as bumps, dragging, hammering, etc. can cause relatively serious scratches. This will make the surface treatment more difficult, and it is also the main reason why stainless steel is prone to rust after processing. Of course, there are also equipment factors. During the bending and folding processes of profiles and sheet materials, the scratches and creases caused are also one of the main reasons for rusting after processing. 

Preventive measures to avoid defects

The first step is that stainless steel parts should be stored on dedicated storage racks. The storage racks should preferably be made of wood or have a painted surface of carbon steel, or be padded with rubber pads to separate them from other metal materials such as carbon steel. During storage, the storage location should be convenient for lifting and should be isolated from other material storage areas. Appropriate protective measures should be taken to prevent contamination of the stainless steel by dust, oil, and rust. 

When hoisting stainless steel parts, special lifting tools such as lifting belts and special clamps must be used. It is strictly prohibited to use steel wire ropes to avoid scratching the surface; and during lifting and placement, impact and collision should be prevented to avoid scratches. When transporting stainless steel products, use transportation tools (such as trolleys, battery-powered vehicles, etc.), and they should be clean with isolation and protection measures to prevent dust, oil stains, and rust from contaminating the stainless steel. Dragging is strictly prohibited to avoid and scratches. 

The next aspect is related to processing. The processing area for stainless steel parts should be relatively fixed, and the platform in the processing area should be equipped with isolation measures, such as laying rubber pads. The fixed-position management and civilized production in the stainless steel processing area should be strengthened to avoid damage and contamination of the stainless steel parts. During the cutting process, the cutting of stainless steel parts should use methods such as shearing or plasma cutting, sawing, etc. Regarding mechanical processing, attention should also be paid to protection when processing stainless steel parts with machines such as lathes and milling machines. After the operation is completed, the oil stains, iron filings, and other debris on the workpiece surface should be cleaned up. In the forming processing, when bending the stainless steel sheet, effective measures should be taken to prevent scratches and creases on the surface of the stainless steel parts. 

Before welding, stainless steel parts must be thoroughly cleaned of oil, rust, dust and other impurities. When welding, argon arc welding should be used as much as possible. When using manual arc welding, a small current and fast welding should be employed to prevent oscillation. Arc ignition is prohibited in non-welding areas. The grounding wire position should be appropriate and the connection should be firm to avoid arc scratches. Anti-splash measures should be selected during welding. After welding, stainless steel chisels should be used to thoroughly remove the slag and splashes. 

During the processing of stainless steel parts, transportation tools should be used, and measures for cleanliness and isolation protection should be taken to prevent contamination of the stainless steel by dust, oil, and rust. It is prohibited to drag them directly on the platform or the ground, and knocking and scratching are strictly forbidden.