Imagine a manufacturer being awarded a contract to produce critical stainless steel. Metal plates and tubular profiles are cut, bent, and welded before entering the finishing station. This component consists of plates welded vertically onto the pipeline. The weld looks good, but it is not in the perfect state that the customer wants. Therefore, the grinder requires longer time than usual to remove welding metal. Then, alas, a clear blue spot appeared on the surface – a clear sign of excessive heat supply. In this case, this means that the parts do not meet the customer’s requirements.
Polishing and finishing are usually done manually, requiring flexibility and skill. Considering all the costs already invested in the workpiece, errors during precision machining may be extremely costly. In addition, the cost of rework and installation of scrap metal is even higher for expensive thermal sensitive materials such as stainless steel. Coupled with complex situations such as pollution and passivation failures, the once lucrative stainless steel work may turn into a disaster of losing money or even damaging reputation.
How can manufacturers prevent all of this? They can start by learning grinding and precision machining, learning each method and how they affect stainless steel workpieces.
These are not synonyms. In fact, everyone has fundamentally different goals. Polishing can remove burrs and excess welding metal and other materials, and surface treatment can be completed by finishing the metal. When you consider that grinding with large wheels can quickly remove a large amount of metal, leaving a very deep ‘surface’, this confusion is understandable. But when polishing, scratches are only a consequence, with the aim of quickly removing materials, especially when using heat-sensitive metals such as stainless steel.
Fine machining is carried out in stages, with operators starting with coarser abrasives and then using finer grinding wheels, non-woven abrasives, possibly felt pads and polishing paste to obtain mirror finish machining. The goal is to achieve a certain final effect (graffiti pattern). Each step (finer gravel) will remove deeper scratches from the previous step and replace them with smaller scratches.
Due to the different purposes of grinding and finishing, they often cannot complement each other, and if the wrong consumables strategy is used, they can even offset each other. In order to remove excess welding metal, the operator left very deep scratches with a grinding wheel and then handed the parts over to a dresser, which now has to spend a lot of time removing these deep scratches. This sequence from grinding to precision machining is still the most effective way to meet customer precision machining requirements. But again, they are not complementary processes.
Usually, workpiece surfaces designed for manufacturability do not require grinding and finishing. Only grinding the parts can achieve this, as grinding is the fastest way to remove welds or other materials, and the deep scratches left by the grinding wheel are exactly what the customer wants. The manufacturing method of parts that only require precision machining does not require excessive material removal. A typical example is a stainless steel part with an aesthetically pleasing weld protected by tungsten gas, which simply needs to be mixed and matched with the substrate surface pattern.
Grinding machines equipped with low material removal wheels can cause serious problems when processing stainless steel. Similarly, excessive heat can cause blueing and alter the properties of the material. The goal is to keep stainless steel as low as possible throughout the entire process.
To achieve this, selecting the wheel with the fastest disassembly speed based on the application and budget will help. Grinding wheels with zirconium particles grind faster than alumina, but in most cases, ceramic wheels work best.
Ceramic particles are very sturdy and sharp, and wear in a unique way. Their wear is not smooth, but as they gradually decompose, they still maintain sharp edges. This means that their material removal speed is very fast, usually several times faster than other grinding wheels. This usually causes the glass to turn into circles that are well worth the additional cost. They are an ideal choice for processing stainless steel because they can quickly remove large debris, generate less heat and deformation.
Regardless of the type of grinding wheel chosen by the manufacturer, the possibility of contamination must be considered. Most manufacturers know that they cannot use the same grinding wheel for both carbon steel and stainless steel. Many companies physically separate carbon and stainless steel grinding businesses. Even small sparks from carbon steel falling on stainless steel parts can cause pollution problems. Many industries, such as pharmaceuticals and the nuclear industry, require environmentally friendly consumer goods
Post time: Aug-03-2023