Industry News

The construction process of flux-cored wire cladding wear-resistant rollers directly affects the wear resistance, bonding strength and service life of the cladding layer. The following summarizes the key technical points from the aspects of pretreatment, welding parameter control, process execution points, post-treatment, etc., and gives operation suggestions based on practical application experience:

1. Pretreatment before welding: substrate preparation and defect repair

The roller surface should be cleaned to remove defects such as oil, rust, oxide scale and cracks on the surface of the wear-resistant roller. Sandblasting (grain size 80-120 mesh) or mechanical grinding (grinding wheel/wire brush) can be used to ensure that the metallic luster is exposed and the surface roughness reaches Ra12.5-25μm to enhance the bonding strength between the cladding layer and the substrate. For high-hardness substrates (such as 42CrMo, 34CrNiMo6, etc.) or large-diameter rollers (diameter>1m), preheating is required to reduce welding stress and prevent cold cracks. Electric heating plates or flame heating can be used, and infrared thermometers can be used to evenly monitor the roller surface temperature.

2. Welding process parameters: Matching welding wire type and equipment requirements

Select welding wire model according to the working conditions of wear-resistant rollers (such as abrasive hardness and impact load). Low-alloy high-strength flux-cored welding wire is used for the base layer; medium-hardness welding wire is used for the transition layer; wear-resistant layer: use high-chromium and high-carbon welding wire; welding equipment is recommended to use CO₂ gas shielded welding (low cost, high deposition efficiency) or mixed gas protection (Ar+CO₂, improved forming), gas flow 15-25L/min, to ensure protection effect (avoid pores).

3. Overlay process control: avoid defects and stress accumulation

During the overlay process, the interlayer temperature must be maintained at ≥150℃ to prevent the weld from cooling rapidly to produce martensitic structure and cause cracks. When surfacing a large diameter roller (diameter > 1.5m), hammering treatment (using a copper hammer or rubber hammer) can be performed after every 2-3 layers of surfacing. The weld surface should be hammered to release stress. The hammering point spacing is 5-10mm, and hammering should be avoided in overheated areas (hammering is prohibited when the temperature is > 200℃). For parts with a long axial length such as vertical mill rollers, "symmetrical segmented welding" (alternating surfacing from the center to both ends) can be used to reduce axial deformation.

4. Post-weld treatment: Improve performance and dimensional accuracy

After surfacing, stress relief annealing is required within 24 hours. After annealing, machining (grinding or turning) is performed to control the roller surface dimensional tolerance to ±0.5mm and the surface roughness Ra≤6.3μm. For the roller surface of the roller press, specific wear-resistant patterns (such as serrated and grid-like) need to be processed to enhance the friction of the extruded material.

5. Process optimization suggestions

Automated welding: For wear-resistant rollers produced in batches, CNC cladding equipment (such as cantilever welding robots) can be used to accurately control the welding trajectory and parameters, which can increase efficiency by 3-5 times compared to manual welding, and the cladding layer has better uniformity.

Composite coating design: Under high impact and high wear mixed conditions, a gradient design of "bottom layer toughness + surface layer wear resistance" (such as the combination of ZD1+ZD3+ZD310) can be used to balance wear resistance and impact resistance, extending the service life by more than 30%.