What does Ni Resist mean?
Definitions of Ni-resist. cast iron consisting of graphite in a matrix of austenite. synonyms: Ni-resist iron. type of: alloy cast iron, alloy iron. cast iron containing alloying elements (usually nickel or chromium or copper or molybdenum) to increase the strength or facilitate heat treatment.
What is NI resist material?
Ni-Resist or Ni Resist alloy grades are austenitic gray cast iron casting grades that provide good hardness, dampening, and some corrosion resistance. These grades are very brittle and cannot be welded.
What is ASTM a439?
Austenitic Ductile Iron, also known as austenitic nodular iron or austenitic spheroidal iron, is characterized by having its graphite substantially in a spheroidal form and substantially free of flake graphite.
Is cast iron heat resistant?
The Ni-resist cast irons have good resistance to high-temperature scaling and growth up to 1500°F (815°C) for most oxidizing atmospheres. In sulphur-containing atmospheres, however, the nickel content of these alloys limits their use to temperatures below 932°F (500°C).
What is austenitic cast iron?
The austenitic cast irons are a range of highly alloyed cast irons containing nickel, and, according to the grade: manganese, copper, chromium, niobium, and an elevated silicon content. Carbon is present either as flake (lamellar) or spheroidal graphite and, in some grades, carbides.
What changes occurs in cast irons when nickel is added?
Nickel and copper increase strength, and machinability, but do not change the amount of graphite formed. The carbon in the form of graphite results in a softer iron, reduces shrinkage, lowers strength, and decreases density.
What is nickel cast iron?
[′nik·əl ′kast ′ī·ərn] (metallurgy) An improved-strength alloy cast iron containing a small percentage of nickel (2-5%); in larger amounts (15-36%) nickel primarily imparts corrosion resistance.
What is ASTM a436?
This is an America standard for the physical properties, mechanical properties and chemical analysis of austenitic cast iron. The types of austenitic cast iron include austenitic gray cast iron and austenitic ductile cast iron.
What is the effect of nickel on cast irons?
The addition of Nickel in cast iron has following effects mainly: It increases impact strength, machinability, toughness. Increases hardenability, but is least effective among hardenability agents. It helps in reducing distortion and cracks in quenching phase of heat treatment.
Is austenite a phase?
Austenite is a high temperature phase and has a Face Centred Cubic (FCC) structure [which is a close packed structure]. The alpha phase is called ferrite. Ferrite is a common constituent in steels and has a Body Centred Cubic (BCC) structure [which is less densely packed than FCC].
How do you make cast iron corrosion resistant?
Nickel is used to improve the corrosion resistance of cast iron in a number of applications. Ni increases corrosion resistance by the formation of protective oxide film on the surface of the casting. Ni up to 4 % is added in combination with Cr for improving both the strength and corrosion resistance in the cast iron.
What is heat treatment for Ni-resist castings?
Stress Relief It is advantageous to use heat treatment to stress-relieve Ni-Resist castings to remove residual stresses formed during cooling after casting and subsequent machining. This is done by heating to 600-650°C(1110-1200°F) at a rate of 50-100°C/hour (90-180°F/hour).
What is the heat resistance of Ni-resist alloys?
Heat Resistance: Originally, because of good heat and oxidation resistance, the flake graphite Ni-Resist alloys were used at temperatures up to 700°C(1300°F). How- ever, because of the superior elevated temperature properties of the spheroidal graphite Ni-Resists, the flake alloys are now seldom used above 315°C(600°F).
What is the thermal expansion coefficient of Ni resist?
Generally, the density of Ni-Resists is about 5% higher than for gray cast iron and 15% lower than cast bronze alloys. Thermal Expansion For the various Ni-Resist alloys, the coefficients of ther- mal expansion range from 5.0 x 10–6/°C(2.8 x 10–6/°F) to 18.7 x 10–6/°C(10.4 x 10–6/°F).
How does temperature affect the impact resistance of Ni-resist D-2M?
The impact resistance decreases as temperature drops to sub-zero levels, but, because of the austenitic structure, there is no sharp embrittlement or transition point. In the case of Ni-Resist D-2M, the impact strength is maintained to -196°C(-321°F).