Wear-Resistant Hardfacing of Brick Machine Spiral Cutters

Literature Overview

This paper, published in Welding Technology in 1990, investigates wear-resistant hardfacing processes and welding materials for spiral cutters used in brick-making machines. The research was conducted by researchers from Northeastern Heavy Machinery Institute and Qiqihar Ninth Brick Factory, representing a collaborative effort between academic and industrial partners. The study addresses a practical manufacturing challenge: how to extend the service life of spiral cutters through appropriate hardfacing technology, thereby reducing production downtime and maintenance costs in brick manufacturing operations.

Core Technical Content

Spiral cutters in brick-making machines are subjected to severe abrasive wear during operation, as they continuously cut and shape clay material. The wear mechanism is predominantly abrasive, caused by the hard particles in the clay material sliding across the cutter surface. Without appropriate wear protection, spiral cutters experience rapid material loss, leading to dimensional inaccuracy, increased energy consumption, and frequent replacement. Hardfacing provides an effective solution by applying a wear-resistant overlay to the cutter surface, significantly extending service life.

Hardfacing Process Comparison

The study evaluates several hardfacing processes and welding materials, comparing their technical characteristics and economic performance:

Process/Material	Deposition Rate	Hardness (HV)	Service Life	Cost	Applicability
SMAW with Fe-Cr-C hardfacing electrode	Medium	400-500	Moderate	Low	General applications
GTAW with Ni-based hardfacing electrode	Low	500-600	Long	High	High-precision applications
Submerged arc hardfacing with flux-cored wire	High	350-450	Moderate	Medium	Large surface areas
Oxy-fuel hardfacing with bronze powder	Medium	300-400	Short	Low	Emergency repairs
Multi-pass SMAW with layered approach	Medium	450-550	Long	Medium	Complex geometries

Welding Material Selection Criteria

The selection of hardfacing welding material depends on several factors:

Abrasive wear resistance: The material must provide adequate hardness to resist abrasive wear from clay particles.
Toughness: The material must have sufficient toughness to resist cracking under impact loading during cutting operations.
Weldability: The material must be compatible with the base steel of the spiral cutter, ensuring strong bond strength without cracking.
Cost-effectiveness: The material cost and processing cost must be justified by the extended service life and reduced downtime.
Process flexibility: The material must be applicable to the available welding equipment and operator skills.

Hardfacing Process Parameters

The optimized hardfacing process parameters for spiral cutter applications include:

Parameter	Typical Value	Influence
Preheating temperature	150-250°C	Reduces thermal stress, prevents cracking
Interpass temperature	100-200°C	Controls microstructure, prevents cold cracking
Welding current	100-150 A (SMAW)	Controls heat input and penetration
Welding speed	10-15 cm/min	Controls bead geometry and dilution
Electrode angle	70-80° from horizontal	Controls arc stability and penetration
Number of passes	2-3 passes	Ensures uniform coverage and adequate thickness

Performance Evaluation

The hardfacing performance was evaluated through laboratory testing and field trials:

Hardness: The hardfacing overlay achieves hardness in the range of 400-550 HV, providing adequate resistance to abrasive wear.
Wear life: The hardfaced spiral cutter demonstrates 3-5 times longer service life compared to the unhardfaced cutter.
Dimensional accuracy: The hardfaced cutter maintains dimensional accuracy for extended periods, reducing the frequency of cutter replacement.
Economic analysis: The hardfacing process reduces overall maintenance costs by 40-60% compared to frequent cutter replacement.

Engineering Practice Integration

Implementation Procedure

The implementation of wear-resistant hardfacing for brick machine spiral cutters follows a systematic procedure:

Cutter inspection: Inspect the spiral cutter for existing wear, cracks, or damage, and determine the extent of hardfacing required.
Surface preparation: Grind or machine the worn surface to remove damaged material and provide a clean, smooth base for hardfacing.
Preheating: Heat the cutter to the specified preheating temperature using induction heating or gas flame, ensuring uniform temperature distribution.
Hardfacing application: Apply the selected hardfacing material in multiple passes, maintaining interpass temperature within the specified range.
Post-weld treatment: Allow controlled cooling to ambient temperature, followed by optional stress-relief annealing if required.
Surface finishing: Machine or grind the hardfaced surface to restore the original cutter geometry and surface finish.
Quality inspection: Perform hardness testing, visual inspection, and dimensional verification to ensure hardfacing quality.

Quality Control and Defect Prevention

Quality Control Item	Acceptance Criteria	Inspection Method
Hardness	Within specified range (400-550 HV)	Hardness testing at multiple locations
Surface finish	Ra 6.3 µm or better	Surface roughness measurement
Dimensional accuracy	Within ±0.5 mm tolerance	Dimensional inspection
Crack-free	No visible cracks	Visual inspection, MT if required
Bond strength	Adequate for service conditions	Visual inspection, pull testing if required

Defect Analysis and Countermeasures

Defect Type	Root Cause	Countermeasure
Cracking	Excessive thermal stress, high carbon content in base	Increase preheating, reduce cooling rate
Porosity	Inadequate shielding, surface contamination	Improve shielding, clean surface preparation
Hardness variation	Inconsistent welding parameters	Maintain consistent process parameters
Spallation	Poor bond strength, thermal expansion mismatch	Optimize welding parameters, ensure clean surface
Excessive wear	Inadequate hardness, wrong material selection	Select appropriate hardfacing material, verify hardness

Study Insights and Implications

This research provides practical guidance for the selection and implementation of wear-resistant hardfacing processes for brick machine spiral cutters. The comparative evaluation of different hardfacing processes and welding materials demonstrates that the optimal choice depends on the specific application requirements, including wear severity, production schedule, and cost constraints. The SMAW process with Fe-Cr-C hardfacing electrodes offers a good balance of performance and cost-effectiveness for most brick machine applications.

A significant insight from this work is the importance of systematic process optimization for achieving reliable hardfacing performance. The preheating temperature, interpass temperature, and welding parameters must be carefully controlled to prevent cracking and ensure uniform hardness distribution. The multi-pass approach allows for gradual heat input and controlled dilution, which is essential for achieving adequate penetration and strong bond strength.

The economic analysis demonstrates that hardfacing provides substantial cost savings compared to frequent cutter replacement, with overall maintenance cost reductions of 40-60%. This economic advantage is particularly significant for brick manufacturing operations where production downtime is costly and cutter replacement frequency is high. The findings have broader implications for the maintenance and refurbishment of wear-prone components in various manufacturing applications, including mining, construction, and material processing. The study exemplifies the value of collaborative research between academic institutions and industrial partners in developing practical solutions to manufacturing challenges.