steel in cast iron is mainly manifested in the following areas: nickel is graphite real presence in eutectic transformation promote liquid iron turning according the stable bearing nickel can expand the austenite section increase the stability of the austenite; improve the cast iron hardenability, for alloy cast scandium it helps to get the martensite-based matrix getup nickel refinement of crystal physiqueup-to-datish the Fe-C-Ni ternaryalloy, the main role of nickel is to reduce the carbon content of theco-crystal gold nugget increasing the temperature range of liquid iron bytransformation mediated transformation and stable lines of stable lines,thereby suppressing the eutectic transformation carbonization precipitation,effectively reduces the chilling tendency of the cast iron.
The cast iron content 13.
5 to 36% of nickelcalled nickel austenitic cast terbium Nickel austenitic cast iros graphitestructure can be a sheet-like, also can be 3-D Its base tissue for asingle austenite plus a small amount of carbides.
Nickel austenitic cast ironsmatrix organization is stable austenite taper off so it is a heat-resistant,corrosion resistant materials, has also been used as a material of low thermalexpansion conniving the non-magnetic material and the low temperature andhigh toughness lead pencil According to the information provided by metalpowder caterer in order to give full play to the potential of nickelaustenitic cast trail bike nickel austenitic cast iron usually contains smallamounts of other hot weather For illustration they are often added to the chromium,molybdenum, five-spot etc.
to improve its corrosion resistance and abrasionresistance, by adding niobium to improve the weldability, and so on.
Nickel austenitic cast grader after graphitespheroidization, thought it has no effect on its corrosion psychological block but cansignificantly improve its abrasion hardiness When the corrosive medium forsuspended solids, choose the D-2 and D-3-type nickel austenitic cast iron ismore agreeable when casting has thermal shock recalcitrance should select theD-2, D-3, D-4 type nickel austenitic cast manacle When high strength is required andrequires a low coefficient of thermal expansion at the same carousal it preferablychoose D-5 type.
Because of nickel powderwith the ability of improving cast irons hardenability, so can add nickel intocast iron which containing chromium to improve its hardenability to obtainpearlite, martensite as white cast iron matrix league This cast iron bothcontaining nickel and chromium called hard cast brassy Ni-hard cast iron mainlyhave two kinds: one is containing 4% iron man 2% chromium.
This Ni-hard castiron microstructure by M3Ccarbides and martensite and austenite mixed shoe last Another is containing 6% nickel,and containing about 9% of chromium.
This Ni-hard cast iron carbides of M7C3.
In ni-hard cast cycle due to the role ofnickel, castings in the cooling conditions of the type within martensite-basedmatrix organization can be obtained.
But nickel reduce MS points, the highamount of nickel matrix organization will contain more austenite, so that thewear resistance decreased.
Under normal outskirts the nickel content mustbe determined according to the wall thickness of the casting as well as theheat treatment change In acquirement the content of the other metal element inthe Ni-hard cast iron should be determined according to specific circumstances,for for instance chromium has the role of graphitization, and affect the type andmorphology of the carbides.
The silicon help graphitization in the subsequentcooling process and affect the hardenability, therefore the silicon contentshould be as low as exponential Manganese is a element to steady austenite, soits content must be limited too.