When roller press is working, the materials are squeezed and rubbed between the two rollers’ surface. Therefore, the abrasion type of the roller surface is heavily stressed abrasion wear. The roller surface should have higher hardness and ductility of. From analysis of the damaged forms of squeeze roller, the selected materials for overlaying should be wear resistant with higher ductility and fatigue resistance. Therefore, when we apply hard-facing technology, the carbon equivalent should be considered since it decides the strength, ductility and impact resistance. In principle, hot welding should be adopted, which means temperature should be kept high when welding and insulating heat.

According to the work condition of roller press and abrasion of roller surface, the hardness, ductility and wear resistance should be considered for selecting materials. At the same time, it should not be too thick for hardfacing layer, or it’s easy for overlaying materials to peel off under high stress. Buffer layer is needed between parent material and hardfacing layers. It forms gradient in radial direction to enhance the integration of overlaying layers.

Besides, the wear resistance effect of squeeze roller is decided by the hardness and ductility. Usually the hardness of squeeze roller surface should be more than HRC55. There are also some strict restrictions to the quantity and distribution of surface crack to avoid crack extension and connecting each other under high stress. Meanwhile, the overlaying materials of roller are not allowed to peeling off and fall-block in part or large area in operation.

After welding, the overlaying layers of the squeeze roller are graded distribution from inner to outside in ascending order, which can not only ensure the good wear resistance, but also strong anti-impact to guarantee crack resistance and anti-fatigue performance.

In the previous repair for roller surface, high chromium iron electrode is used in cement factory . After overlaying, there are large amount of carbides distributed in hardfacing layers with hardness HRC60 and 3% C or even more. . This material has good wear resistance, but the integration, crack resistance and fatigue resistance are poor. Interlaced crack will appear even if there is one layer welded on the surface. When the squeeze rollers are running, the layers are easy to peel off in large due to stress. Meanwhile, the interlaced crack of overlaying layers are prone to extend to the parent roller, thus the quality of the whole roller will be influenced. After long operation, the roller may fail. Therefore, there are some requirements for the overlaying material and process as following:

（1）The wires for backing welding are required to be with good ductility, which are welded on the bottom layer as the one for crack resistance.

The bottom layer is used for good integration of overlaying layer and the roller, and it prevents the whole overlaying layer from peeling off. At the same time, bottom layer with good crack resistance effectively prevent weld crack and fatigue crack from spreading and developing, thus protecting the roller from damaging.

For example, ARCFCW1003 developed by Beijing ARC is hardfacing material with high impact resistance and wear resistance. The austenite formed by high alloy flux-cored wire with HB180-200 has performance of corrosion resistance, automatic hardening, anti-magnetism and thermal shock proof by 850℃. Due to the reason that its ductility is high up to 40%, such alloy can be used as transition layer on previous wear-resisting surface for joining special steels or steels that are hard to be welded (such as high manganese steel).

(2) Good materials for transition layer and welding parameters are important premise to ensure the safe and effective operation of hardfacing layer.

The transition layers not only can ensure the good integration between bottom layer and hardfacing layer, but also be the good support of hardfacing layer. So the hardness of transition layer must be higher than that of bottom layer.

The transition layers are between the parent material and the hardfacing layer. They form gradient with hardness increasing in radial direction of the roller to enhance the integration of the parent roller and the overlaying layer. Wires for transition layer should be with high strength and can resist higher tensile stress and pressure stress, thus it can have good buffer function. For example, ARCFCW9318 developed by Beijing ARC is flux-cored wire with high shock load resistance and wear resistance. With hardness of HB200-250, this overlaying material with high ductility and medium hardness has good fatigue resistance and good integration. At the same time, it also has certain wear resistance performance, which plays an role of bridge between parent roller and hardfacing layers. Besides, with pure austenite weld bead there are characteristics of corrosion resistance, non-magnetization, and high-ductility. This overlaying material can be used as transition layer on original hard surface. The working hardness of the weld bead can reach HB500. Such kind of weld bead is anti-shrinking, stress resistance and high shock load resistance.

(3) Welding materials for roller surface should be with higher hardness, crack resistance and excellent wear resistance to abrasive particle in high stress work condition. The hardness of hardfacing layer should be higher than that of transition layer.

Welding material ARCFCW9996 can be used for roller surface since the microstructure of the weld bead contains high wear-resisting titanium carbides and martensite. It has good crack resistance and can be used in rollers of cement crushing machine, pulverizer and crushing hammer. With HRC59-64, it can be used for hardfacing layer based on ARCFCW9318 as transition layer. The hardfacing layer should not be over welded, or it will be easy to peel off under high stress condition.

(4) The emboss layer is working surface, which is required for wear resistance to abrasive particle in high stress work condition and medium impact.

The materials of emboss layer have the highest hardness among all the overlaying materials. For example, ARCFCW9996 is high alloy overlaying material. As the emboss layer of the roller, it has excellent wear resistance. The hardness of welding layer is HRC59-64. Small crack in less quantity will appear on the emboss layer after hardfacing. But because ARCFCW9996 has good ductility, the crack won’t extend to overlaying layers.