Zhuojin Pipe Fitting Co., LtdManual Overlay Hardening Treatment of Wall and Floor Tile Molds
Literature Overview
This technical report by Wu Jun and Wu Jingshu from Wuhan Institute of Technology, published in Welding Technology in 1994, describes the application of manual overlay welding for hardening wall and floor tile molds. The work addresses a practical manufacturing problem where mold life is limited by wear on critical cutting edges, leading to high replacement costs and production interruptions. The study demonstrates that overlay welding with high-hardness alloy deposits on medium carbon steel molds provides a cost-effective solution that achieves hardness exceeding Cr12 tool steel while significantly reducing material costs.
Technical Approach and Process Details
The researchers used medium carbon 45 steel as the base material for tile molds and applied high-hardness alloy overlay deposits to the cutting edge regions using manual arc welding. The overlay approach is selected because it allows selective hardening of wear-prone areas without requiring the entire mold to be made from expensive high-alloy tool steel.
The key process parameters and considerations include:
| Parameter | Specification | Rationale |
|---|---|---|
| Base material | 45 steel | Adequate strength, low cost, good weldability |
| Overlay material | High-carbon alloy steel | Hardness exceeding Cr12 |
| Welding method | Manual arc welding (SMAW) | Flexibility, accessibility for field repair |
| Application area | Cutting edges only | Targeted hardening of wear zones |
| Preheating | Moderate preheat | Reduce cracking risk in 45 steel |
The hardness achieved by the overlay deposits exceeds that of Cr12 tool steel, which is a high-carbon high-chromium cold work tool steel known for excellent wear resistance. This is remarkable because Cr12 is a premium tool steel with significant material cost, while the overlay approach uses a 45 steel base with relatively inexpensive alloy deposits.
Engineering Practice Implications
The overlay hardening approach described in this study is directly applicable to a wide range of manufacturing applications where tool life is limited by edge wear. Beyond tile molds, similar techniques can be applied to:
- Cutting tools and dies for metal forming operations.
- Punches and dies for sheet metal stamping.
- Milling cutters and grinding wheels.
- Pipeline forming dies and pipe bending tools.
- Extrusion dies for metal processing.
The economic advantage is substantial. By using a low-cost base material with localized overlay hardening, manufacturers can achieve the performance of expensive tool steels at a fraction of the cost. The manual welding approach also allows for in-situ repair of worn molds, extending service life without complete replacement.
From a quality control perspective, the overlay weld must be inspected for proper fusion with the base metal, absence of cracks, and uniform hardness distribution. Visual inspection, magnetic particle testing, and hardness profiling are essential quality verification methods. The weld procedure specification must be carefully developed to ensure consistent results across multiple welders and production shifts.
Study Insights and Reflections
This early technical report exemplifies the practical engineering approach of solving real manufacturing problems with accessible technology. The manual arc welding overlay technique requires minimal equipment investment and can be implemented by existing welding personnel with appropriate training. The economic analysis demonstrates clear cost savings compared to using expensive tool steels for the entire mold.
The work also highlights the importance of materials selection in manufacturing processes. By combining a ductile, weldable base material with a hard, wear-resistant overlay, the design achieves the best properties of both materials. This composite approach is a fundamental principle in materials engineering that finds application across diverse industries.
For contemporary practice, the overlay hardening concept has evolved to include automated welding processes, advanced consumable designs, and computer-controlled deposition systems. However, the fundamental metallurgical principles remain unchanged, and the manual technique described here remains relevant for small-batch production and field repair applications where automation is not practical.
The study serves as a reminder that practical, cost-effective solutions often lie in the intelligent application of well-established technologies rather than in the pursuit of novel materials or processes. Engineers should always consider the economic and practical constraints of their applications when selecting materials and manufacturing processes.