Classified by chemical composition of stainless steel with Cr and Cr, Ni stainless steel stainless steel two kinds big.
Affect the corrosion performance of stainless steel are mainly C content and precipitation of carbides, so the corrosion resistance of stainless steel C content is lower, the better, usually C≤
08%, however, the high temperature of heat resistant steel mechanical performance is determined by its stable carbides precipitate phase in the organization, so the heat resistant steel C content is higher, general carbon content in the 0.
More than 20%.
1 to chromium as main alloy elements and Cr content is in commonly 13%
Has good oxidation resistance of medium corrosion and air oxidation resistance at high temperature, also can be used as heat resistant steel.
This kind of steel welding performance is poorer.
Chromium is more than 16%, the as-cast organization bulky, in 400 -
525 ℃ and 550 -
Between 700 ℃ heat preservation for a long time, can appear & other;
Brittle phase and the sigma phase, make steel brittle.
475 ℃ brittleness associated with ordering containing Cr ferritic phenomenon.
475 ℃ brittle phase and the sigma phase brittleness, can be heated to above 475 ℃ and then quickly to improve the cold.
Room temperature brittleness of brittleness and after welding heat affected zone is also one of the basic problems of ferritic stainless steel, vacuum refining, can be used to trace elements (
Such as boron, rare earth and calcium, etc. )
Austenitic formation elements (or
Such as Ni, Mu, N, Cu, etc. )
Can be improved.
In order to improve the weld area and the mechanical properties of heat affected zone, usually also add a small amount of Ti and Nb and grain growth in heat-affected zone.
Commonly used ferrite steel has ZGCr17 and ZGCr28.
The impact toughness of the steel is low, on many occasions by the high nickel austenitic stainless steel.
Ni content more than 2%, more than 0 N content.
15% of the impact of the ferritic steel has good performance.
3 austenitic stainless steel can be divided into four groups, namely the Cr ‐ Ni department;
Cr ‐ Ni ‐ ‐ Mo, Cr Ni ‐ ‐ Cu and Cr Ni ‐ Mo ‐ Cu is;
Cr ‐ ‐ Ni Mn ‐ N series and Cr ‐ Mn ‐ N system.
Cr ‐ Ni is by the famous & other;
As a representative.
Cr ‐ Ni ‐ ‐ Mo, Cr Ni ‐ ‐ Ni, Cu, Cr ‐ Mo ‐ Cu system on the basis of Cr ‐ Ni is add 2%
3% of molybdenum and copper (
Or both to join)
, in order to improve the resistance to sulfate corrosion, but form element, molybdenum is ferrite to austenite, after add molybdenum content of Ni to appropriately increase.
Cr ‐ Mn ‐ N is save Ni alloy.
When Cr content is more than 15%, are unable to obtain the ideal individual to join fierce austenitic organization, must add 0.
3% of the nitrogen, to get a single austenite must add 0.
More than 35% of nitrogen.
Due to too high N content tend to make the casting
defects such as blowholes, osteoporosis, and adding suitable amount of N and a small amount of Ni, can be single austenite, this is a Cr ‐ Ni ‐ Mn ‐ N system.
Of course to get austenitic, ferritic phase organization, we need not to add more N and Ni.
2 martensitic stainless steel including markov shape and precipitation hardening stainless steel stainless steel.
In engineering application, based on mechanical properties of main purpose.
Although this type of steel in atmospheric corrosion and moderate corrosion medium (
Such as water and some organic medium)
Good corrosion resistant ability, but its corrosion resistance is often inspection items.
The scope of its chemical composition is: Cr13 % -
Microstructure of low carbon plate strip martensite, therefore, it has excellent mechanical properties, strength index is more than 2 times of austenitic stainless steel, and also have good process performance, especially the welding performance.
Therefore occupies very important position in important engineering application, is an important branch of cast stainless steel field.
4 the complex phase steel microstructure is usually contains 5%
40% of the ferrite, to improve the weldability of alloy, increase strength and improve the ability of resistance to stress corrosion.
Cr28 % - for example
30% of the high carbon high chromium alloy steel, with good resistance to sulfate corrosion ability, can be used to manufacture castings.
On the basis of the development of the controlled company ferrite steel, has high strength, and in the sulfate has the good ability to resist stress corrosion, commonly used in the oil industry.
According to the microstructure classification, stainless steel, martensite stainless steel are divided into ferrite stainless steel and austenitic stainless steel and duplex (
In the austenitic matrix ferrite)
Stainless steel, stainless steel, chromium content is more than 12% of the iron base alloy called stainless steel, is the floorboard of the stainless steel, acid steel.
Stainless steel is weak corrosion media such as air, steam and water resistance of steel, acid steel is refers to the chemical etching media such as acid, alkali, salt corrosion of steel, stainless steel with acid-resistant steel alloying extent have bigger difference, the stainless steel are not rust, but does not necessarily acid;
And acid is commonly have stainless steel, resistant to chemical corrosion medium in the air or corrosion of a high alloy steel, stainless steel is a beautiful surface and corrosion resistant performance is good, need not after surface treatment, such as color of plating and the surface of the stainless steel inherent performance, used in a variety of steel a, often called stainless steel.
At present, the stainless steel castings has been widely used in the market, small make up today about the stainless steel castings for everybody to four categories:
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