Surfacing Welding Process for Cold Pressing Die Manufacturing and Repair

Literature Overview

This technical paper by Jiang Yucheng from Yantai Automobile Plant, published in Welding in 1989, presents a practical engineering approach to using surfacing welding for both the manufacture and repair of cold pressing dies. The work addresses the economic and technical challenges of die production in automotive manufacturing, demonstrating that surfacing welding can achieve equivalent service life to conventionally manufactured solid alloy tool steel dies while offering substantial cost and schedule advantages.

Core Technical Approach

The fundamental strategy involves using a lower-grade substrate material (such as carbon steel or low-alloy steel) as the die body, with a wear-resistant alloy layer deposited on the working surfaces through surfacing welding. This approach eliminates the need for expensive high-alloy tool steels throughout the entire die volume while maintaining the critical surface properties required for cold forming operations.

Comparative Analysis of Approaches

Parameter	Solid Alloy Tool Steel Die	Surfaced Die (Carbon Steel + Overlay)
Material Cost	High (100% alloy steel)	Low (substrate) + Moderate (overlay)
Machining Time	Extensive (hardened alloy steel)	Moderate (softer substrate) + Surfacing
Manufacturing Cycle	Long	Short
Repair Feasibility	Difficult and expensive	Straightforward re-surfacing
Service Life	Baseline	Equivalent
Applicable Standards	GB/T 1299, GB/T 1298	GB/T 3482, SY/T 6503

Technical Implementation

Substrate Preparation

The substrate material must be selected to provide adequate toughness and dimensional stability during the forming process. Common choices include 45 steel, 50Cr steel, or low-alloy steels such as 16Mn. The substrate should be machined to final dimensions with an allowance of 3–5 mm for the surfacing buildup. Surface preparation is critical: the area to be surfaced must be clean, free of scale and oxide, and preferably ground to provide mechanical keying for the weld metal.

Surfacing Alloy Selection

For cold pressing dies, the overlay material must provide:

Hardness in the range of 55–65 HRC for adequate wear resistance
Sufficient toughness to resist chipping during the forming process
Good resistance to galling and seizure against the formed material
Compatibility with the substrate to prevent cracking at the interface

Typical overlay compositions include high-carbon martensitic alloys (such as those based on Cr12MoV or similar compositions), with carbon content in the range of 1.0–2.0% to ensure full martensitic transformation upon cooling.

Welding Process Parameters

The study emphasizes the use of manual arc welding (SMAW) with appropriate electrode selection. Key process considerations include:

Parameter	Specification
Preheat Temperature	200–300°C
Interpass Temperature	<300°C
Electrode Type	Low-hydrogen, high-carbon alloy
Weld Pass Thickness	3–5 mm per pass
Final Grinding Allowance	1–2 mm
Post-Weld Treatment	Temper at 550–600°C

Engineering Practice Implications

The economic advantages of this approach are substantial. In automotive manufacturing, where die volumes are large and production schedules are tight, the ability to use economical substrates with surface hardening provides significant competitive benefits. The repair capability is perhaps the most underappreciated advantage: when a die is damaged by chipping or excessive wear, the damaged area can be ground back and re-surfaced without scrapping the entire die.

Quality Control Considerations

For critical die applications, the following quality assurance measures should be implemented:

Visual inspection of all surfacing passes for cracks, porosity, and incomplete fusion
Magnetic particle testing (MT) of the overlay and heat-affected zone for crack detection
Hardness verification at multiple locations across the overlay surface
Dimensional verification after grinding to ensure geometric accuracy
Trial forming operation to validate die performance before production release

Study Insights and Reflections

This paper, while published in 1989, addresses a fundamental engineering principle that remains highly relevant: the separation of bulk properties from surface properties in component design. The surfacing approach for die manufacturing is essentially an early application of what is now termed "functionally graded design," where different regions of a component are optimized for different performance requirements. The success of this approach depends critically on the quality of the bond between substrate and overlay, which in turn depends on proper process control. Modern practitioners should note that while the basic principles remain valid, today's available electrode compositions, preheat methods, and non-destructive testing capabilities have significantly improved the reliability of this approach.