CLADDING TECHNOLOGY SHANXI CO., LTDMicrostructure and Properties of the Cladding Layer on Draw-Reduction Rolls
Overview of the Study
The research conducted by Chen Hua, Wang Liyan, and Liu Xiaochun, supported by the Jilin Provincial Natural Science Foundation (Grant No. 201115143), focuses on the microstructural evolution and mechanical performance of weld overlay layers applied to draw-reduction rolls used in wire and cable drawing operations. Draw-reduction rolls are critical components in the cold-drawing industry, subjected to severe abrasive and adhesive wear against high-strength steel wires. The cladding layer must therefore exhibit a combination of high hardness, good toughness, and strong metallurgical bonding with the substrate. The authors investigated the effect of thermal processing parameters on the cladding microstructure and wear resistance, providing valuable guidance for optimizing cladding processes in industrial practice.
Key Technical Parameters and Process Window
The study examines the relationship between heat input, welding current, travel speed, and the resulting microstructure of the overlay layer. The following table summarizes the typical process parameters and their influence on the cladding microstructure:
| Parameter | Typical Range | Effect on Microstructure |
|---|---|---|
| Welding current (I) | 180–260 A | Higher current increases dilution and grain coarsening |
| Travel speed (V) | 15–30 cm/min | Higher speed reduces heat input and refines grains |
| Heat input (q) | 1.2–2.5 kJ/mm | Low q favors martensitic transformation; high q promotes retained austenite |
| Layer thickness | 3–8 mm | Thicker layers require multi-pass welding with interpass temperature control |
| Interpass temperature | ≤ 150 °C | Excessive interpass temperature reduces hardness and promotes carbide coarsening |
The authors employed metallographic analysis, scanning electron microscopy (SEM), and microhardness testing to characterize the cladding layer. The microstructure of the overlay typically consists of martensite, retained austenite, and carbides (primarily Cr7C3 and M7C3 type). The hardness of the cladding layer was measured in the range of HRC 55–62, depending on the specific composition and thermal cycle.
Microstructural Analysis and Wear Mechanism
The wear mechanism of the cladding layer on draw-reduction rolls is primarily governed by abrasive wear from wire contact and adhesive wear from friction. The authors identified that the distribution and morphology of carbides play a decisive role in wear resistance. Fine and uniformly dispersed carbides provide superior abrasion resistance, while large and coarse carbides act as stress concentrators and initiate micro-cracks under cyclic loading.
The dilution ratio between the base metal and the overlay material was found to be a critical factor. Excessive dilution introduces carbon and alloying elements from the substrate into the overlay, altering the phase composition and reducing the hardness. The authors recommended using a pre-heating temperature of 100–150 °C to reduce residual stresses and minimize the risk of cracking, while maintaining a controlled cooling rate to promote fine microstructural features.
Engineering Practice Implications
In industrial applications, the cladding of draw-reduction rolls is typically performed using submerged arc welding (SAW) or gas metal arc welding (GMAW) with hardfacing electrodes such as M2Mn or Cr-Mo-V type consumables. The following practical considerations should be noted:
- The surface of the roll must be thoroughly cleaned and pre-heated uniformly to avoid localized stress concentrations.
- Multi-pass welding is necessary for achieving the required layer thickness, with each pass carefully controlled to limit heat accumulation.
- Post-weld heat treatment (PWHT) at 550–600 °C for 2 hours can improve toughness without significantly reducing hardness.
- Non-destructive testing (NDT) using magnetic particle inspection (MT) or ultrasonic testing (UT) should be performed after cladding to detect surface and subsurface defects.
The study contributes to the understanding of how thermal processing parameters influence the service life of draw-reduction rolls. By optimizing the heat input and interpass temperature, the service life of the cladding layer can be extended by 30–50% compared to conventional practices. This finding has direct implications for reducing downtime and maintenance costs in wire and cable manufacturing plants.
Study Insights and Concluding Remarks
The research by Chen Hua and colleagues provides a systematic investigation into the microstructure-property relationship of cladding layers on draw-reduction rolls. The emphasis on thermal processing parameters as a means to control the overlay microstructure is particularly valuable for engineers who must balance hardness, toughness, and bonding strength in practical applications. The work reinforces the principle that cladding is not merely a deposition process but a carefully controlled metallurgical operation where heat input, composition, and cooling rate must be harmonized to achieve the desired performance. For engineers working in the wire and cable industry, the findings offer a clear roadmap for selecting welding parameters that maximize the wear resistance of draw-reduction rolls while maintaining the integrity of the cladding-substrate bond. This study exemplifies how fundamental metallurgical research can be directly translated into improved industrial outcomes.