Wear-Resistant Cladding of Sintered Hot Ore Crusher Toothed Rollers

Literature Overview

This study note addresses the application of weld overlay cladding technology for the wear-resistant protection of toothed rollers used in sintered hot ore crushing operations, as reported by Zhang Baochen from Hainan Steel Group Sintering Plant and Liu Xin and Wang Zhiqiang from CITIC Heavy Industries in 2003. Sintered iron ore crushers operate under exceptionally severe conditions: high temperatures (300-500°C from hot sintered ore), high impact loading from large ore chunks, and intense abrasive wear from the angular, hard sintered pellets. The toothed roller design concentrates the crushing force at the roller teeth, creating localized high-stress regions that are prone to rapid wear and chipping.

Core Technical Content

Operating Environment and Wear Mechanisms

The sintered hot ore crushing environment presents a unique combination of wear mechanisms that must be addressed simultaneously:

Wear Mechanism	Contributing Factors	Dominant Location
Abrasive wear	Angular sintered pellets, high hardness (Mohs 6-7)	Roller tooth flanks and tips
Impact wear	Large ore chunks, high kinetic energy	Roller tooth tips
Thermal fatigue	Repeated heating/cooling cycles from hot ore	Roller surface, especially teeth
Adhesive wear	Metal-to-metal contact at high pressure	Roller tooth roots, raceway areas

The combination of thermal cycling and mechanical loading creates a particularly challenging environment for cladding materials. The overlay layer must maintain its hardness and structural integrity at elevated temperatures while accommodating thermal expansion mismatch with the base material.

Cladding Process Selection

For toothed rollers, the geometry presents unique challenges for automated cladding. The teeth are discrete features with varying surface orientation, making continuous automated cladding difficult. The authors likely employed one of the following approaches:

Submerged arc welding (SAW) with multiple passes: Suitable for large, flat surfaces between teeth but requires manual finishing on tooth surfaces.
Flux-cored arc welding (FCAW): More versatile for complex geometries, with self-shielded flux providing protection in all positions.
Oxy-fuel welding: Flexible for manual application on tooth surfaces but produces thicker, lower-quality layers.
Hot-wire TIG: Combines TIG arc stability with GMAW deposition rates, suitable for precision cladding on complex geometries.

The most practical approach for toothed rollers in an industrial setting is typically FCAW or SAW for the main roller body and manual FCAW or oxy-fuel for the tooth surfaces. This hybrid approach balances productivity with geometric flexibility.

Cladding Material Selection

The selection of cladding material for sintered hot ore crushers requires careful consideration of the operating temperature and wear mechanisms:

Material System	Hardness (HV)	Temperature Resistance	Typical Application
Cr-Mo cast iron (Cr 12-14%)	500-700	400°C	Moderate temperature, abrasive wear
High-Cr white iron (Cr 20-25%)	700-1000	350°C	High abrasion, lower temperature
Maraging steel (H13 + tempering)	450-600	500°C	High impact, thermal cycling
Ni-Cr-C (Stellite type)	350-450	600°C	High temperature, moderate abrasion
WC-reinforced alloy	1000-1600	400°C	Severe abrasion, lower temperature

For sintered hot ore crushers operating at 300-500°C, materials such as high-chromium white iron or modified austenitic manganese steel with carbide reinforcement offer the best balance of hardness retention at temperature, thermal shock resistance, and impact toughness. Purely carbide-reinforced systems may suffer from thermal cracking at elevated temperatures due to the low thermal conductivity and high coefficient of thermal expansion mismatch with the base material.

Engineering Practice and Quality Control

Pre-Cladding Preparation

The surface preparation of the toothed roller is critical to achieving sound cladding bonds. The roller must be machined to remove existing wear, scale, and oxide layers, exposing clean base metal. The tooth geometry should be optimized for cladding — sharp tooth tips may require rounding to prevent stress concentration during the cladding process. Surface roughness should be controlled to Ra 6.3-12.5 μm to promote adequate wetting without excessive material consumption.

Post-Cladding Treatment

The cladding process introduces significant residual stresses due to the thermal mismatch between the overlay and base material. For toothed rollers operating under cyclic loading, these residual stresses must be managed:

Stress relief annealing: Heating to 550-650°C for 2-4 hours followed by controlled cooling reduces residual stresses by 60-80%.
Peening: Shot peening the cladded surface introduces compressive residual stresses that counteract the tensile stresses from cladding, improving fatigue resistance.
Controlled cooling: Slower cooling rates (10-20°C/h) during the post-cladding cooling phase reduce thermal stresses.

Defect Analysis

Defect	Detection Method	Impact on Service Life
Cracking at tooth root	MT, PT, visual inspection	Catastrophic — tooth detachment
Porosity in overlay	UT, radiography	Reduced effective cross-section
Insufficient penetration	Sectioning, hardness profiling	Delamination risk
Excessive dilution	Metallography, composition analysis	Reduced hardness, premature wear
Inclusion of flux	Metallography, hardness profiling	Stress concentration sites

Key Questions and Reflections

The 2003 publication reflects a mature period of cladding technology application in Chinese steel and mining industries. Several engineering questions merit consideration:

What was the service life improvement achieved with cladded toothed rollers compared to uncladded or conventionally protected rollers? In similar applications worldwide, cladding typically extends service life by 3-8 times.
How was the thermal management addressed during cladding of hot ore crushers? Preheating and interpass temperature control are critical for preventing cracking in high-carbon overlay materials.
What was the economic analysis — comparing the cost of cladding plus labor against the cost of roller replacement? The economic justification for cladding depends on the relative cost of overlay material, labor, and downtime.

The work by Zhang Baochen and colleagues represents the practical application of cladding technology in a demanding industrial environment. The collaboration between the end-user (Hainan Steel) and the equipment manufacturer (CITIC Heavy Industries) reflects the integrated approach necessary for successful cladding implementation — the equipment manufacturer must understand the operating conditions, and the end-user must understand the limitations and maintenance requirements of the cladding system.

Study Insights and Implications

The cladding of sintered hot ore crusher toothed rollers demonstrates the power of surface engineering to extend component life in extreme operating environments. The technology enables the use of cost-effective base materials (typically Q345 or 42CrMo steel) while providing a high-performance surface layer tailored to the specific wear mechanisms. The key insight from this work is that successful cladding requires not only the right material and process but also careful attention to surface preparation, process parameters, and post-treatment. The collaborative approach between the end-user and equipment manufacturer is essential for optimizing the cladding system for the specific application. This case study remains relevant to contemporary practice, as sintered ore crushers continue to be a major application for wear-resistant cladding in the steel and mining industries.