In the process of equipment maintenance, there are often transitions and interference fit assembly of copper sleeve, steel sleeve, bearing, shaft and gear. In the past, the assembly process used to be mostly hot assembly (hot assembly for short), that is to say, by means of flame heating or oil boiling heating, the parts were heated up to about 200 ℃. After the assembly base hole was heated and expanded, the sleeve, shaft were put into the hole, etc. after cooling, the purpose of assembly of the sleeve, gear and other parts was achieved.
Shortcomings of hot charging process
1.1 long assembly time and low efficiency
Because the assembly needs to heat the parts with holes, the hole diameter expands greatly. Generally, the size and volume of the parts with holes are large, so the heating time is often very long to make the holes expand. Taking the assembly of wk-4b electric shovel winch gear as an example, the heating time is generally 2-3 hours.
1.2Assembly quality is not easy to control
Because the coefficient of thermal expansion of metal is relatively small, even when the temperature is raised to about 200 ℃, the expansion of pore size is limited. If the heating time is not enough, the gap is considered too small, and the ambient temperature is too low, the cooling speed is accelerated, and the assembly can not be carried out in time, it may cause the hole diameter to shrink during the installation process, and the sleeve and shaft are not in place yet, resulting in the locking and dilemma, Finally, the press can only be used to press out or cut out the parts in the hole, which will also cause damage to the base hole.
1.3 complicated processIn the later stage of heating, it is necessary for workers to repeatedly test the pore size under high temperature. In this way, there are not only potential safety hazards, but also no guarantee of accurate measurement.
1.4 high cost
It occupies a large area and needs to be supervised. It consumes a lot of wood, coke, oil and other materials.