Application and Research Progress of Overlay Welding Technology on Medium and High Carbon Steels

Literature Overview and Context

The paper by Yang Qingxiang, Gao Yuwei, Liao Bo, and Yao Mei, published in 2001 in the Journal of Yanshan University (Vol. 25, Issue 4, pages 301-304), reviews the application of overlay welding technology on medium and high carbon steels and summarizes the development progress of overlay welding electrodes. The work was supported by the State Key Laboratory of Modern Welding Production Technology and the Ministry of Mechanical Industry Outstanding Talent Fund. Medium carbon steels (0.3-0.6% C) and high carbon steels (0.6-1.5% C) are widely used in structural applications, tooling, and mechanical components due to their good combination of strength, toughness, and hardenability. However, these steels are notoriously difficult to weld due to their high carbon equivalent (CE), which promotes the formation of hard, brittle martensite in the heat-affected zone (HAZ). Overlay welding offers a viable strategy for surface hardening, wear protection, and repair of these materials without compromising the base metal's structural integrity.

Core Technical Content

The authors survey the application scenarios and electrode development progress for overlay welding on medium and high carbon steels. The key technical challenges include:

Carbon Equivalent and Hardenability

The carbon equivalent, defined by the IIW formula as $CE = C + \frac{Mn}{6} + \frac{Cr + Mo + V}{5} + \frac{Ni + Cu}{15}$, is a critical parameter for assessing weldability. For medium carbon steels with CE values of 0.4-0.6, moderate preheating (100-200°C) is typically required. For high carbon steels with CE values exceeding 0.6, preheating of 200-400°C may be necessary to reduce cooling rates and prevent HAZ cracking.

Steel Grade	Carbon Content (wt%)	Typical CE	Preheat Temperature (°C)	Post-Weld Heat Treatment
45 steel (0.45C)	0.42-0.50	0.35-0.45	100-200	Stress relief at 550-650°C
50 steel (0.50C)	0.47-0.53	0.40-0.50	150-250	Stress relief at 550-650°C
60 steel (0.60C)	0.57-0.63	0.50-0.60	200-300	Stress relief at 550-650°C
80 steel (0.80C)	0.77-0.83	0.65-0.75	300-400	Stress relief at 550-650°C

Electrode Development Progress

The authors highlight several categories of overlay welding electrodes developed for medium and high carbon steel applications:

Cast iron electrodes (iron-based hardfacing) — These include Si-Mn cast iron electrodes (e.g., CH-2, CH-3 types) that produce a weld metal with good wear resistance and machinability. The high silicon and manganese content promotes the formation of pearlite and cementite in the weld deposit, providing hardness in the range of 35-50 HRC.
Stainless steel electrodes — Austenitic stainless steel electrodes (e.g., E309, E310) are used when corrosion resistance is required in addition to wear protection. The austenitic weld metal accommodates differential thermal expansion between the weld and the ferritic base metal, reducing cracking susceptibility.
Nickel-based electrodes — Nickel-alloy electrodes (e.g., E617, E618) provide excellent resistance to thermal shock and high-temperature wear. They are particularly suited for applications involving cyclic heating and cooling, such as hot work tooling.
Hardfacing electrodes with carbide particles — Electrodes containing WC, Cr₃C₂, or TiC particles produce weld deposits with exceptional abrasive wear resistance. The carbide particles remain intact or partially dissolved during welding, providing hard reinforcement phases in the weld matrix.

Application Scenarios

The overlay welding technology is applied in several key scenarios for medium and high carbon steels:

Repair of worn components — Shafts, rollers, and gears that have undergone dimensional wear can be rebuilt by depositing a hardfacing layer followed by machining to restore original dimensions.
Surface hardening — Components such as dies, molds, and extrusion tools can be enhanced by overlay welding a hardfacing layer on critical surfaces.
Transition welding — When joining dissimilar materials (e.g., carbon steel to stainless steel), a transition overlay layer of austenitic stainless steel (E309) is deposited on the carbon steel side to prevent cracking and ensure a ductile weld interface.
Corrosion protection — Overlay welding of corrosion-resistant alloys on carbon steel substrates provides a cost-effective alternative to full alloy construction for components subject to localized corrosion.

Technical Analysis and Process Considerations

The weldability of medium and high carbon steels is fundamentally limited by their propensity to form martensite during welding. The hardenability of the HAZ is governed by the carbon content, alloying elements, and the cooling rate. The critical cooling rate ($t_{800-500}$) below which martensite forms can be estimated from the CE value. For CE > 0.5, martensite formation is likely under typical welding conditions, leading to HAZ hardness values exceeding 400 HV, which poses a risk of hydrogen-induced cracking (cold cracking).

The following process parameters are critical for successful overlay welding on medium and high carbon steels:

Parameter	Recommended Range	Rationale
Preheat temperature	100-400°C (depending on CE)	Reduces cooling rate, prevents martensite formation
Interpass temperature	100-300°C	Controls thermal input, prevents excessive grain growth
Heat input	0.5-2.5 kJ/mm	Balances HAZ hardenability with dilution control
Electrode diameter	3.2-5.0 mm	Ensures adequate penetration and deposit thickness
Travel speed	50-100 mm/min	Controls bead width and dilution ratio
Post-weld heat treatment	550-650°C for 1-4 hours	Relieves residual stresses, reduces HAZ hardness

Study Insights and Reflections

This review paper serves as a valuable compilation of overlay welding practices for medium and high carbon steels during a period of rapid industrial development in China. The emphasis on electrode development reflects the practical orientation of the research, where consumable innovation is directly linked to field performance. From a modern perspective, the principles described remain valid, though the electrode compositions and welding processes have evolved significantly. The introduction of flux-cored wire (FCAW), submerged arc welding (SAW) with automatic or semi-automatic equipment, and plasma arc welding (PAW) has expanded the capabilities and productivity of overlay welding operations. Nevertheless, the fundamental metallurgical challenges of welding high carbon steels — HAZ hardenability, hydrogen cracking susceptibility, and residual stress management — remain unchanged, and the process control strategies outlined in this paper continue to provide a solid foundation for current engineering practice.