How to Choose Pump Materials
1 Cast iron
For most liquid transfer applications, gray cast iron is the preferred material for pump housings. For single-stage pumps, gray cast iron is strong enough to resist the pressures generated. In the medium pressure and temperature range, ductile iron is widely used. If gray cast iron and ductile iron cannot achieve sufficient corrosion resistance. Corrosion-resistant high-nickel cast iron is often used as the pump body material.
In recent years, a new type of corrosion-resistant high-nickel cast iron with good welding performance (named D2W) has been developed. It contains a small amount of niobium to improve its welding performance. Typical austenitic cast iron contains 15% to 20% nickel and is widely used in the brine.
Grey cast iron
It is the most commonly used cast iron. The national standard code is HT.
Generally, this material is used in the pump body, impeller, pump cover and suspension of the clean water pump.
Three grades are usually used: HT150, HT200, HT250.
For non-main parts, HT150 is mostly used as a base and backing plate. HT200 is mostly used for pump body, pump cover, suspension. HT250 is mostly used for impeller, mouth ring, and shaft sleeve.
Different countries have different ways of expressing gray iron. For example, the Japanese code is FC, the German code is GG, and the United States is Class 4.
It is a kind of cast iron with better comprehensive performance. The national standard code is QT. Due to its mechanical properties Near steel. At the same time, its casting performance and processing performance are better than steel. So, it is used as a substitute for cast steel.
The most commonly used grades are: QT450-10, QT500-7, QT600-3. Due to the limitation of casting and other reasons, this material is currently used for the impeller of the water pump. In particular, the cost-effectiveness of the open impeller of the cutting type is superior.
The DIN standard’s representation method for ductile iron is GGG. The United States’ representation method is Ductile iron.
2 Cast steel
For corrosive and harmful petroleum products, or when the outlet pressure of the multi-stage pump reaches 13.8Mpa, it is necessary to use the specified cast steel or cast stainless steel. In boiler feed pumps and many hydrocarbon applications, martensitic stainless steel is often used. Martensitic stainless steel has good mechanical properties. It is suitable for high pressure conditions. However, its corrosion resistance is not as good as other types of stainless steel.
In chemical applications and other corrosive environments, austenitic stainless steels (CF-8M, CF-3M, etc.) are often used as pump housing materials.
In addition, austenitic stainless steels are resistant to corrosion due to high speeds. And Field weld repairs can be performed relatively easily.
High-pressure shallow sea water injection pumps have higher requirements on corrosion resistance and mechanical properties. The pump casing is made of duplex stainless steel (50% ferrite + 50% austenite).
Due to the higher strength of cast steel, usually when the pressure is greater than 1.6Mpa, the pressure-bearing parts are mostly cast steel. Its national standard code is ZG. The most commonly used grade is ZG23 0-450. Japan and the United States usually use CS to represent cast steel.
In many pump applications, bronze materials are also used for the pump body.
Lead bronze is commonly used in small low pressure pumps.
Lead contributes to the tightness of the pump body.
Tin bronze is used as the pump body material for larger centrifugal pumps.
Nickel aluminum bronze has the best mechanical properties and corrosion resistance. But expensive and not competitive.
4. Stainless steel
The most widely used stainless steel is austenitic stainless steel. Such as 0Cr18Ni9, 1Cr18Ni9Ti,0Cr18Ni12Mo2Ti. Except for a few media such as hydrochloric acid and dilute sulfuric acid, austenitic stainless steel is an excellent corrosion-resistant material. It is the most commonly used corrosion-resistant material for chemical pumps.
Japan and the United States usually use SS304, SS316, SS316L to represent austenitic stainless steel.
Martensitic stainless steels such as 2Cr13 and 3Cr13 have better mechanical properties than austenitic stainless steels. They are usually used as materials for pump shafts and bushings.
The corresponding codes in Japan and the United States are SS420.
In addition, high-alloy stainless steel (#20 alloys) and duplex stainless steel are also ideal corrosion-resistant materials.
5. Carbon structural steel
Usually divided into ordinary carbon structural steel and high-quality carbon structural steel. The most representative ordinary carbon structural steel is Q235. Various types of steel plates and section steels are mostly made of this material.
The most representative high-quality carbon steel is No. 45 steel. It is widely used in pump shaft materials where no corrosion is required
6. Alloy steel
The most representative alloy steel is 40Cr. Material typically used for high-strength pump shafts.
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