What's The Difference Between Cast Iron Valve And Cast Steel Valve

Definition of cast iron:

Cast iron usually refers to gray iron, ductile iron, and malleable iron. It is cast iron parts with carbon content higher than 2%.

The main classification of cast iron:

①Cast iron

Gray cast iron: such as HT200, HT250, etc., suitable for nominal pressure not greater than PN16, working temperature between a 10 ~ 100 ℃ oil, general nature of the liquid medium (water, steam, petroleum products, etc.): nominal pressure not greater than PN10, working temperature between -10 ~ 200 ℃ steam, general nature of the gas, gas, ammonia and other media (ammonia, alcohol, aldehyde, ether, ketone It is not applicable to hydrochloric acid, nitric acid, etc.) It is not applicable to hydrochloric acid, nitric acid, and other media. But it can be used in concentrated sulfuric acid because concentrated sulfuric acid can produce a passivation film on its metal surface to prevent the corrosion of cast iron by concentrated sulfuric acid.

②Malleable cast iron

Such as KTH350-10, KTH450-06, etc., suitable for nominal pressure not more than PN25, working temperature between 10 ~ 300 ℃ steam, general nature of the gas and liquid, oil, and other media; its corrosion resistance is similar to gray cast iron.

③Ductile iron

Such as QT400-15, QT450-10, etc., for the nominal pressure is not greater than PN25 working temperature in a 10 ~ 300 ℃ between the steam, general nature of the gas and oil and other media. Its corrosion resistance is strong and can work in a certain concentration of sulfuric acid, nitric acid, and acid salt. But not resistant to fluorine acid, strong alkali, hydrochloric acid, and ferric chloride hot solution of corrosion. Avoid sudden heat and cold when using, otherwise, it will break.

④Nickel cast iron:

Stronger alkali resistance than gray cast iron and ductile cast iron valves; used in dilute sulfuric acid, dilute hydrochloric acid, and caustic alkali, nickel cast iron is an ideal material for valves.

Casting requirements of gray cast iron:

①The surface of the castings should be clean of sticky sand, gates, risers, sand traps, scars, etc...

②Castings shall not have cracks, porosity, sand trapping, and other harmful defects.

③Castings shall not be hammered, plugged, or impregnated to eliminate leakage.

④Castings should be of moderate hardness, and easy to cut and process.

Definition of cast steel:

Cast steel usually refers to ordinary carbon steel and alloy steel. It is the cast steel parts with a carbon content of less than 2%.

Cast steel parts are solid metal objects produced by filling the voids in a mold with liquid steel. They can be used for many of the same carbon and alloy steels that can be produced as forged metal.

Carbon steels such as WCA, WCB, and WCC are available for use in media such as steam, non-corrosive gases, petroleum, and related products at working temperatures between -29°C and 425°C.

Carbon steel castings require:

① Steel for castings should be melted in an electric arc furnace or induction electric furnace.

② All castings should be heat-treated according to the requirements of the design drawings.

③Castings should be supplied in annealed, normalized, or normalized plus tempered condition; ASTM A 216/A216M castings are supplied in accordance with supplementary requirement S15, i.e. quenched + tempered, with quenching temperature in the range of 890 ~ 910°C and tempering temperature in the range of 500 ~ 650°C.

④Castings must be cooled to below the phase change temperature before heat treatment.

Comparison of the characteristics of cast iron and cast steel.

①Iron has better corrosion properties than steel.

②Cast iron is generally cheaper than cast steel.

③Cast iron is relatively easy to cast due to its own flow characteristics.