High-Strength Wear-Resistant Alloy Overlay Welding on Sintering Machine Tail Scraper

Literature Overview

This technical paper, published in Sintering and Pelletizing (2011, Vol. 36, Issue 2), documents the practical application of high-strength wear-resistant alloy overlay welding on the tail scraper of a sintering machine at Jinan Iron and Steel Group's Ironmaking Plant. The study addresses a persistent operational challenge in ironmaking operations: the rapid wear of tail scrapers caused by direct contact with abrasive sintered ore material. The implemented solution extended the scraper service life to 18–24 months, representing a dramatic improvement over conventional scraper designs and significantly reducing spare parts consumption and maintenance costs.

Problem Analysis and Force Analysis

The sintering machine tail scraper operates in one of the most abrasive environments in the ironmaking process. The scraper removes sintered ore from the machine tail, and the direct contact between the scraper surface and the abrasive ore material causes rapid wear. The failure analysis requires understanding the complex loading conditions:

Loading Conditions on Tail Scraper

Loading Factor	Description	Effect on Scraper
Abrasive wear	Direct contact with sintered ore	Surface material removal
Impact loading	Falling ore particles	Surface fatigue and chipping
Thermal cycling	Hot ore (500-800°C)	Thermal cracking and oxidation
Mechanical stress	Structural bending and vibration	Subsurface crack initiation
Corrosive environment	Sulfur and moisture in ore	Corrosion-assisted wear

The force analysis revealed that the critical wear zone is concentrated on the scraper surface directly contacting the sintered ore stream. This insight guided the overlay welding strategy to focus the wear-resistant layer on the most severely affected areas rather than applying uniform coverage across the entire scraper surface.

Overlay Welding Solution Design

Material Selection and Layer Structure

The solution employed a strategic overlay welding approach with the following design principles:

Targeted application: The wear-resistant alloy was deposited primarily on the ore-contact surface rather than uniformly across the entire scraper, optimizing material usage and cost.
Structural optimization: The overlay layer was designed to work in conjunction with the scraper's structural geometry, with the hard layer oriented to resist the dominant wear direction.
Bonding layer consideration: A transition layer between the base steel and the hard overlay alloy was likely incorporated to prevent cracking due to thermal expansion mismatch.

Overlay Layer Structure and Force Direction

The key innovation described in this paper is the rational arrangement of the wear-resistant layer structure and force direction. This means:

The overlay weld beads were oriented perpendicular to the primary sliding direction of the ore, creating a series of hard ridges that resist wear progression.
The layer thickness was optimized to provide sufficient wear reserve without adding excessive weight or stress concentration.
The transition between the overlay layer and base material was designed to accommodate differential thermal expansion during operation.

Performance Results

Metric	Before Overlay	After Overlay	Improvement
Service life	Short (implied <6 months)	18–24 months	3-4× improvement
Spare parts consumption	High	Significantly reduced	Major cost savings
Maintenance frequency	Frequent	Reduced	Lower downtime

The extension of service life to 18–24 months represents a substantial economic benefit. For a sintering plant operating 24/7, each month of scraper life represents significant production capacity that would otherwise be lost to maintenance downtime.

Process Considerations for Sintering Machine Scraper Overlay

Welding Process Selection

For this application, the following process considerations are relevant:

Process type: Submerged arc welding (SAW) or flux-cored arc welding (FCAW) is preferred for large-area overlay applications on structural components like scrapers. These processes offer high deposition rates and good penetration.
Filler material: High-carbon martensitic steel or cobalt-based alloy electrodes/wire are commonly used for severe abrasion resistance. The specific material selection depends on the wear mechanism (abrasive vs. adhesive vs. erosive).
Heat input control: Critical to prevent base metal softening and cracking. Multiple thin passes with controlled interpass temperatures are essential.

Quality Control Measures

Pre-weld inspection: Verify base material condition, remove rust and scale, check for existing cracks.
In-process monitoring: Control welding parameters, interpass temperatures, and bead geometry.
Post-weld inspection: Visual examination, hardness verification, and potentially magnetic particle testing for surface cracks.
Service monitoring: Track wear progression to validate design life predictions.

Engineering Practice Integration

This case exemplifies the practical application of overlay welding technology in addressing real-world industrial wear problems. Several lessons emerge for engineers working in similar applications:

Force analysis before material selection: Understanding the loading conditions is more important than simply selecting the hardest available material. A material optimized for the specific wear mechanism will outperform a harder but less appropriate material.
Strategic application: Focusing the overlay on critical wear zones rather than blanket coverage reduces material costs and avoids unnecessary stress concentrations.
Layer orientation matters: The orientation of weld beads relative to the sliding direction significantly affects wear resistance. Beads perpendicular to the sliding direction create a series of ridges that resist material removal.
Economic evaluation: The return on investment for overlay welding must be evaluated against the total cost of ownership, including spare parts costs, maintenance labor, and production losses due to downtime.

Study Insights and Implications

This paper demonstrates that overlay welding is not merely a technical exercise but an economic optimization tool. The systematic approach of analyzing the failure mechanism, designing the overlay layer structure to counteract the specific wear mode, and implementing targeted application resulted in a 3-4× improvement in service life. For ironmaking and similar abrasive service applications, this methodology can be adapted to other components experiencing severe wear, such as sintering machine pans, conveyor belts, crusher liners, and mill liners. The key to success lies in the combination of metallurgical understanding, mechanical analysis, and practical implementation.