Purchase of stainless, heat-resistant and refractory steels
Stainless steel - is a corrosion-resistant steel that contains at least 10.5% of chromium and a maximum of 1.2% of carbon. According to the application, it is divided into stainless steel, heat-resistant steel and heat-resistant steel.
In addition to chromium, carbon and iron, corrosion-resistant steels contain additions of other alloying elements to improve various properties of the steel, e.g. mechanical properties, corrosion resistance and formability.
Incandescent steel retains its mechanical and structural properties at extremely high temperatures, typically in excess of 500°C. It is resistant to corrosion from both chemical and high temperatures. Despite its strength, it is relatively well machinable, facilitating the production of complex structures and components.
Chrome-nickel steel
Popularly known as acid-resistant steel, it has in its composition Nickel (min 8%) and chromium. It is mainly found in the form of sheet metal, pipes and components for household items. Acid-resistant steel scrap should be free of contaminated with other metals and organic substances.
Shavings
Chips are an important by-product of the turning and milling processes of stainless steel. The allowable coolant content is 5%. In addition, the material should not be contaminated with other metals in order to preserve its original properties and exceptional corrosion resistance.
Chrome steel
A type of alloyed steel which contains chromium as the main alloying element and stainless steel, which is characterised by high corrosion resistance as well as a noble appearance. On scrap it is mainly found in the form of sheets and drums from washing machines. Scrap should be cleaned of steel and other metals.
Chemical composition of stainless steels
chromium (10.5-30%), nickel (up to 35%) and molybdenum (up to 8%), and, in addition, additions of elements such as: titanium, niobium, copper, manganese, silicon, aluminium, carbon and nitrogen.
It also happens that, in addition to the above-mentioned alloying additives, tungsten, zirconium and boron additives may also be present in stainless steels.
Based on their chemical composition, steel grades are classified into different groups. Depending on the main element or several elements present in corrosion-resistant steels, we can distinguish four subgroups.
Division by main characteristics:
- stainless steels
- heat-resistant steels
- high-temperature steels
Division by chemical properties:
- chromium steels
- chromium-nickel steels
- chrome-nickel-molybdenum steels
- chromium-manganese-nickel steels
Buying stainless steel - price
The scrap purchase prices of these steels depend on the grade.
The cheapest stainless steel is that which contains approximately 8% of nickel.
In contrast, the most expensive steels are heat-resistant and refractory steels, where the nickel content is in the region of twenty or so per cent.
Acid resistant steel - interesting facts
The chromium in the steel, as a result of its higher affinity with oxygen, combines with it faster than with iron and forms a thin oxide layer on the steel surface called the passive layer. This layer adheres tightly to the steel surface and protects it from external corrosive influences.