Stainless steel is chromium and chrome alloys with at least 11% chromium.
The addition of other elements to the alloys allows the formation of a wide range of materials, known as the stainless steel family. Among the alloying elements, there are two prominent elements: chromium, an element found in all types of stainless steel because of its role in corrosion resistance and nickel due to its memory in mechanical properties.
Below is a panoramic view of the stainless steel family, its main characteristics and applications.
Some stainless steel applications
Stainless steel type Implementation
Austenitic (corrosion resistant) Equipment for the chemical and petrochemical industries Food and drug industry equipment
Civil construction industry
Tableware and household utensils
Iron (corrosion resistant, cheaper) Home appliances (kitchens, refrigerators, etc.)
Refrigerated counters
Coins
Auto industry
Covered
Martensitic (high hardness) Tableware
Surgical tools such as scalpel and forceps
Cutting knives
Brake discs
Stainless steel
In SA 213 TP304stainless steel, carbon is in such a concentration that allows austenite to be formed at high temperatures, which in turn converts to martensite during cooling.
Martensite is a carbon rich, fragile and very difficult stage. Martensitic stainless steel has the common features of being magnetic and hardensible by heat treatment. tHEN it is presented at a loosening of the annular microscopic structure (in the form of needles).
It is important to note that this SA 213 TP304Lsteel is usually produced by steelmaking in a solid state, with reasonably good ductility. Only after hardening, they will be very hard and not too soft. But in this particular case (tempered) it would be resistant to corrosion.
In the case of annealing (iron structure), it does not exhibit good behavior against atmospheric corrosion. This is because during the annealing process OF SA 213 TP321, at an approximate temperature of 760 ° C, carbon and chromium combine to form Cr23C6 chromium carbide. Each chromium carbide molecule, by weight, contains approximately 95% of the chromium. Since all carbon is depositing chromium carbide during annealing, this precipitation will remove from the solid solution about half of the available chrome. In this case, the material does not resist corrosion and cannot be considered correctly stainless steel.
Therefore, SA 213 TP316 stainless steel is put into service by the user, only after curing hardening. When it is diluted, carbon forms part of the Martinique stage, and is not found in alloys such as chromium carbide precipitator.
The high hardness and wear resistance of these materials determine the applications of this material for tableware, brake discs, surgical and dental equipment, and turbines.
If the high amount of carbon is defective in stainless steel SA 213 TP316L in the case of steel. Then the logical solution is to reduce this content, which is made in type 410 stainless steel. Since this substance contains 0.15% carbon as a maximum, then this amount it is not sufficient to remove a lot of chromium from the solid solution. Therefore, it has good resistance to air corrosion, both in the case of annealing and hardening.