How to choose the right alloy products

Update:04 Jun 2019

The attributes to consider when selecting a level include:
Corrosion resistance
Oxidation resistance vulcanization
Strength, ductility and ambient temperature at use
Adaptability to processing technology
Adaptability to washing process
Stability of performance in use
The intensity of
Resistance to abrasion and erosion
Resistance to corrosion
reflective
magnetic
Thermal conductivity
Thermal expansion
The resistivity
sharpness
hardness
Dimensional stability
Corrosion resistance is usually the important characteristic of stainless steel or heat resistant steel, but in application, corrosion resistance is also the  difficult to evaluate. Corrosion resistance is relatively easy to determine under natural conditions and in pure chemical solutions. However, local corrosion, such as stress corrosion cracking, crevice corrosion, pitting corrosion, intergranular corrosion (which exists in the heat affected zone of welding), is much more complex than normal corrosion. Although such local corrosion does not cause extensive damage to the whole structure, it may cause unpredictable and even fatal failure. Therefore, these factors must be carefully considered when designing the construction and selecting stainless steel. Corrosion can expand dramatically through tiny impurities in the medium, which are unpredictable but can cause serious consequences at concentrations as small as one part per million. Under heating conditions, even small changes in the atmosphere greatly accelerate corrosion on metals, which may affect corrosion rates, vulcanization, and carburization.
In spite of these complications, we can empirically select suitable steels for applications based on the recommendations of the steel manufacturers. However, it should be recognized that the corrosion data obtained from the test are not always accurate in predicting the performance of a particular kind of material. Even the data obtained from the work are limited, because similar corrosive media may be materially different from each other due to slight variations in some of the corrosion factors mentioned above. For more demanding applications, extensive research and comparative analysis of the two types of data are required, and sometimes guided tests or working tests are conducted accordingly.
Mechanical properties at operating temperatures are the primary consideration, but the need for satisfactory performance at other temperatures is sometimes overlooked. Therefore, products used in low-temperature environments must have subzero performance, although a constant operating temperature may be much higher, performance at room temperature after operation is also important.
The selection of products should not only consider the performance requirements, but also consider the requirements of manufacturing and cleaning. Materials with a certain machinability (formability or weldability) are usually selected, rather than other materials with relatively good properties but high processing costs. Even cleaning procedures affect the choice of steel. In some cases, the use of stable, low carbon materials for welding may be overlooked, even if sensitization under working conditions is not important. The welded material needs to be cleaned in a medium, such as nitric acid-hydrofluoric acid, which will corrode the sensitized alloy. For some specialized applications, the other capabilities listed in the list are critical. But it is rarely considered in many other applications. Surface layer smoothness is important for many applications, sometimes using stainless steel, because it has a variety of beautiful surface layer for selection. Surface layer can be selected according to appearance, smoothness or cleanability. The effect of surfaces on cleanliness is sometimes not as simple as one might think, and testing existing surfaces may be desirable. The choice of surface layer may affect the choice of type, and the choice of surface layer may in turn affect the choice of material grade, because different levels of surface layer, surface layer durability is different. The grade with higher corrosion resistance will maintain a bright finish in a corrosive solution that will corrode steel with lower alloy content.

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