Created on:2021-05-18 09:17

Common materials for gear pump manufacturing process

Common materials for gear pump manufacturing process

The common materials of key parts of gear pump are as follows.

(1) The shell and end cover are usually made of cast iron or aluminum alloy. Large displacement gear pumps are mostly made of cast iron shell, medium and small displacement gear pumps are mostly made of aluminum alloy shell, and the middle part shell of large displacement gear pump is mostly made of extruded special-shaped pipe after cutting, which has the advantages of low cost and uniform material compared with casting blank. The bearing surface of the gear ring of the internal gear pump can also be made directly in the aluminum shell. The front and rear end covers of small displacement pumps are usually made of die cast aluminum alloy blanks, but some manufacturers use ductile iron to make the front and rear end covers, which have the characteristics of high strength, vibration reduction and noise absorption.

(2) Gear, gear pump and high pressure gear pump gear is made of carburized or nitrided steel. As mentioned above, the shaft of small and medium-sized gear pump is usually made into integral type, while the large pump is made into separate type and connected with key. The common material grades of gears and shafts are 45 steel, 40Cr, 20CrMnTi, 20Cr, 38CrMoAl and other materials (the first two are used for low-pressure gear pumps, and the last three are used for high-pressure gear pumps). After carburizing and nitriding treatment, the surface hardness of the material is 60 ~ 62Hrc, and the core hardness is 28 ~ 44hrc, so that the gear has high wear resistance and impact toughness. The working surface after quenching must be polished.

The inner and outer rotors of small low-pressure cycloidal internal gear pump are usually made of iron-based powder metallurgy materials with low cost.

(3) The common materials of shaft sleeve are 40 steel, 40Cr, copper alloy (mainly tin bronze) and low tin alloy.

There are two types of shaft sleeve: integrated type and integral type. The integrated shaft sleeve is made of bimetallic bearing or Du bearing pressed into the shaft sleeve hole, while the integral shaft sleeve is made of low tin alloy material without bimetallic bearing or Du bearing.

Bimetal bearing, also known as double metal bearing, is a thin-walled double-layer metal with copper alloy sintered on the steel back. Compared with integral copper alloy bearing, it has low cost and is convenient for mass production.

Du bearing is also called SF-1 bearing. Du bearing made of three-layer composite material is originally a kind of oil-free bearing, which can work under friction or no lubrication conditions. When working, the PTFE molecules on the surface of Du bearing can be transferred and bonded to the surface of shaft diameter, which turns the friction between metal materials of friction pairs into the internal friction between PTFE molecules, so as to obtain low friction coefficient and high bearing performance. Du composite bearing is composed of thin steel plate (matrix), lead bronze powder or wire mesh sintering layer and polytetrafluoroethylene. The sintered bronze powder is sponge like multi-l-gap structure (the mesh is reticular), and the PTFE material is impregnated in vacuum. The PTFE material filled with bronze has high elastic modulus, thermal conductivity, the lowest coefficient of thermal expansion and deformation. At various temperatures, it shows a high limit PV value. Using Du bearing in gear pump has good adaptability and performance. At present, the PV value of domestic Du bearing can reach 140 MPa · M / s, and the specific pressure can reach 54 MPa.

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