Heat-Resistant and Wear-Resistant Weld Overlay Process for Toothed Rollers of Sintered Hot Ore Crushers

1. Definition and Technical Principles

The heat-resistant and wear-resistant weld overlay process for toothed rollers of sintered hot ore crushers is a specialized surface engineering technology designed to extend the service life of crushing equipment operating under extreme thermal and mechanical loading conditions. Sintered ore crushers process material that has been pre-heated during the sintering process, exposing the toothed rollers to temperatures ranging from 200°C to 600°C, combined with severe abrasive and impact wear from abrasive iron ore particles.

The fundamental principle involves depositing one or more layers of alloy weld metal onto the base roller surface using arc welding processes. The overlay layers are engineered to possess a combination of:

The metallurgical mechanism relies on the formation of a hard, fine-grained martensitic or austenitic matrix with dispersed primary and secondary carbides. The thermal gradient between the molten weld pool and the cooler base metal creates a dilution-controlled transition zone that ensures adequate bonding strength while minimizing base metal contamination of the overlay.

2. Category and Business Positioning

This technology falls squarely within the TIG/MIG weld overlay business route of Cladding Technology Shanxi Co., Ltd. Specifically, it represents a high-value-added surface engineering application targeting the metallurgical and mining equipment sector. The positioning encompasses:

3. Technical Purpose and Value

3.1 Problem Statement

Toothed rollers in sintered ore crushers experience a unique degradation mechanism that combines:

3.2 Value Delivered

Successful implementation of the overlay process delivers measurable value:

4. Key Process Implementation Points

4.1 Material Selection Matrix

Layer Type Material Grade Key Alloying Elements Hardness (HRC) Function
Transition Layer 309L / 310L / Ni-based Cr 23–25%, Ni 12–14% 25–35 Stress relief, thermal expansion matching, crack arrest
Build-up Layer CastCrMo3 / D2 equivalent Cr 10–12%, Mo 5–6% 45–55 Volume build-up, dimensional restoration
Face Layer Hardfacing alloy (Cr₇C₃ type) Cr 25–30%, C 2.5–3.5%, Mo 5–8% 58–65 Abrasive and thermal wear resistance

4.2 Welding Process Parameters

Parameter Transition Layer Build-up Layer Face Layer
Process SMAW / GTAW SMAW SMAW / SAW
Electrode Type E309L / E310L E8CrMo (D2 equivalent) E81CrMo / E80NiCrMo
Wire Diameter φ3.2 mm φ4.0 mm φ4.0 mm
Current (A) 80–110 120–160 140–180
Voltage (V) 20–24 24–28 26–30
Travel Speed (mm/s) 3–5 4–6 4–7
Heat Input (kJ/mm) 0.8–1.2 1.0–1.5 1.2–1.8
Interpass Temperature ≤ 150°C ≤ 150°C ≤ 100°C
Weld Bead Width (mm) 8–10 10–12 12–15
Weld Bead Height (mm) 2–3 3–4 3–5

4.3 Surface Preparation Requirements

  1. Base material identification: Positive material identification (PMI) to confirm roller base composition (typically Q345, 40Cr, or 42CrMo)
  2. Geometry assessment: Measure remaining tooth profile and determine required build-up volume
  3. Surface cleaning: Remove existing coatings, rust, and contaminants by G7 or G8 grinding (per ISO 8501-1)
  4. Preheating: Apply uniform preheat of 150–250°C (depending on base material carbon equivalent) using induction heating or propane torch
  5. Weld groove preparation (if applicable):strong> U-groove or J-groove preparation for multi-pass build-up on severely worn teeth

4.4 Critical Process Controls

  • Low heat input strategy: Minimize dilution to base metal to preserve overlay alloy chemistry; maintain heat input below 1.8 kJ/mm for face layer
  • Interpass temperature monitoring: Use infrared pyrometer to ensure interpass temperature does not exceed specified limits, preventing excessive grain growth in the overlay
  • Weld direction and sequence: Implement butt-joint overlap sequence to minimize residual stresses; weld in the direction of roller axis to leverage roller curvature for stress relief
  • Post-weld cooling control: Allow controlled cooling rate (≤ 100°C/min) to prevent thermal cracking; apply post-weld heat treatment (PWHT) at 550–600°C for 2 hours for high-stress applications
  • Dilution control: Achieve ≤ 15% base metal dilution in face layer through proper first-pass technique and appropriate electrode selection

5. Applicable Standards and Acceptance Criteria

5.1 Welding Procedure Standards

  • GB/T 985.1 — Designation of welding methods
  • GB/T 19866 — Welding procedure qualification and validation for ferrous metals
  • GB/T 19867 — Welder qualification for ferrous metals
  • ASME Section IX — Qualification of Welding Procedures, Welders, Welding Operators, and Welding Qualified Inspectors
  • ISO 15614-1 — Qualification testing of welding procedures for metallic materials
  • NB/T 47014 — Qualification testing of welding procedures for pressure vessels

5.2 Material and Performance Standards

  • GB/T 13814 — Welding consumables for surfacing
  • GB/T 24490 — Welding consumables — Classification of surfacing electrodes
  • ASTM A523 — Specification for castings, iron, for general engineering purposes (reference for overlay material properties)
  • ASTM A528 — Specification for castings, iron, for special purposes
  • ISO 2560 — Classification of welding consumables for surfacing

5.3 Non-Destructive Testing Standards

  • GB/T 3323 — Radiographic testing of welds
  • GB/T 11345 — Ultrasonic testing of welds
  • GB/T 18851 — Magnetic particle testing
  • ASTM E709 — Standard practice for magnetic particle testing
  • ASTM E165 — Standard practice for liquid penetrant examination

5.4 Acceptance Criteria

Inspection Item Acceptance Standard Method
Overlay hardness ≥ 58 HRC (face layer), ≥ 45 HRC (build-up) HBW/HRC portable hardness tester
Overlay thickness ≥ 3.0 mm total (minimum 2.0 mm face layer) Ultrasonic thickness gauge / section measurement
Adhesion strength ≥ 25 MPa (peel test) GB/T 13914 or ASTM G106
Surface defects No cracks, porosity, or undercuts exceeding 0.5 mm depth MT (GB/T 18851) / PT (ASTM E165)
Internal defects No indications exceeding Level II per GB/T 11345 UT (GB/T 11345)
Geometric accuracy Tooth profile within ±0.5 mm of nominal dimension Coordinate measuring / template inspection
Dilution rate ≤ 15% base metal in face layer Chemical analysis / XRF

6. Common Risks and Controls

Risk Category Description Preventive/Corrective Control
Hydrogen-induced cracking Cold cracking in high-carbon base material due to hydrogen absorption Preheat to 250°C, use low-hydrogen electrodes (≤ 5 mL/100g), post-weld bake at 200°C for 2h
Thermal cracking Hot cracking in overlay weld metal due to low melting point intermetallics Control carbon content, avoid excessive sulfur and phosphorus, use appropriate electrode composition
Spalling/delamination Overlay layer separation from base metal under thermal cycling Proper transition layer application, controlled heat input, adequate preheat
Excessive dilution Base metal dilution reducing overlay hardness and wear resistance Low heat input, short arc length, proper first-pass technique, thin first bead
Residual stress-induced distortion Roller warping affecting operational balance Weld sequence planning, symmetric welding pattern, stress-relief PWHT at 550–600°C
Porosity Gas porosity from contaminated surface or electrode flux Thorough surface preparation, dry electrode storage, shield gas flow verification
Insufficient penetration Incomplete bonding between overlay and base metal Adequate preheat, proper current settings, adequate groove preparation

7. Application Across Technology Routes

7.1 TIG/MIG Weld Overlay (Primary Application Route)

This application is the core domain for the TIG/MIG weld overlay route. The specific implementation for sintered ore crusher toothed rollers involves:

  • GTAW (TIG) for transition layer: Precise heat input control for the first pass to minimize dilution and ensure metallurgical compatibility
  • SMAW for build-up and face layers: High deposition rate with flux-shielded electrodes for efficient volume restoration
  • SAW (Submerged Arc Welding) for thick face layers: When overlay thickness exceeds 5 mm, SAW provides superior efficiency and consistent quality
  • Robotic welding integration: For high-volume production, robotic TIG/SMAW systems ensure parameter consistency and reduce operator variability

7.2 Hydraulic Explosive Bonding (Supplementary Application)

While hydraulic explosive bonding is not directly applicable to roller tooth overlay, the technology contributes to related applications in the same customer ecosystem:

  • Crusher housing cladding: Hydraulic explosive bonding can produce wear-resistant lined housings where the impact zone requires a thick, fully bonded overlay
  • Material pairing: Carbon steel base with manganese steel or high-chromium cast iron cladding for housing applications
  • Complementary service: Offering both explosive bonding for housing components and weld overlay for roller components creates an integrated solutions package

7.3 Explosion Welding (Extended Application)

Explosion welding applications relevant to this technology domain include:

  • Large-diameter roller shell cladding: For large rollers where weld overlay would be impractical due to thickness requirements, explosion welding can produce thick clad shells
  • Wear plate manufacture: Explosion-welded composite wear plates for crusher feed hoppers and chutes exposed to hot sintered ore
  • Material combinations: Q345/Q460 base with 13Cr-4Mo or Cr26 high-chromium alloy cladding for extreme thermal and abrasive environments

8. Contribution to Qualification Building and Customer Value

8.1 Qualification and Certification Building

This research project directly contributes to the company's qualification portfolio through:

  • WPS qualification: Development and documentation of welding procedure specifications per GB/T 19866 and ASME Section IX, specifically qualified for high-temperature service applications
  • WPQ (Welder Performance Qualification): Certification of skilled welders capable of producing qualified overlay welds on production equipment
  • Material qualification: Validation of specific electrode/consumable combinations for hot ore service, creating proprietary process knowledge
  • Performance data library: Accumulation of field trial data establishing overlay life expectancy under defined operating conditions
  • ISO 9001 process integration: Incorporation of this specialized process into the company's quality management system with documented work instructions and control plans

8.2 Product Delivery Enhancement

  • Turnkey overlay service: Ability to deliver fully qualified, field-proven overlay solutions with documented WPS and NDT reports
  • Technical consulting: Capability to provide material selection recommendations, overlay design, and post-weld treatment specifications based on validated process knowledge
  • On-site service capability: Deployment of mobile welding equipment and trained personnel for in-situ roller overlay without equipment removal
  • Warranty provision: Confidence to offer performance warranties based on documented dilution control, hardness verification, and adhesion testing

8.3 Customer Value Proposition

For steel mills and sintering plant operators, this technology transforms toothed roller maintenance from a reactive, high-cost activity into a planned, cost-effective maintenance strategy. The company's demonstrated expertise in high-temperature overlay welding provides customers with:

  • Reduced spare parts inventory (fewer roller replacements required)
  • Lower total maintenance cost per ton of ore processed
  • Increased plant availability through planned rather than emergency maintenance
  • Technical partnership with a qualified supplier who understands their specific operating environment

9. Process Flow Summary

  1. Site assessment: Inspect roller condition, measure wear profile, identify base material
  2. Process selection: Determine overlay material system, number of layers, and welding process based on service conditions
  3. WPS development: Develop or select qualified welding procedure specification
  4. Surface preparation: Clean, grind, and preheat roller surface per procedure
  5. Transition layer application: Apply first pass with low-dilution electrode to establish metallurgical bond
  6. Build-up layer deposition: Apply intermediate layers to restore dimensional profile
  7. Face layer application: Deposit final wear-resistant layer with controlled heat input
  8. Post-weld treatment: Apply PWHT if required by procedure
  9. NDT inspection: Perform MT/PT/UT per acceptance criteria
  10. Hardness and dimensional verification: Confirm overlay hardness, thickness, and geometric accuracy
  11. Documentation and delivery: Compile inspection reports, WPS reference, and certification documents

10. Conclusion

The development of heat-resistant and wear-resistant weld overlay processes for sintered hot ore crusher toothed rollers represents a critical capability for Cladding Technology Shanxi Co., Ltd. in the metallurgical equipment services market. This specialized knowledge—encompassing material selection, process parameter optimization, dilution control, and quality verification—directly translates into measurable customer value through extended equipment life, reduced maintenance costs, and improved operational reliability. The research findings are systematically integrated into the company's WPS library, operator qualification programs, and quality management systems, creating a sustainable competitive advantage in the high-temperature surface engineering niche.