Zhuojin Pipe Fitting Co., LtdArc Surfacing Repair Technology for 2010 Roll Die
Literature Overview
This paper by Gong Shuili et al. (1999), published in the journal "Welding" (焊接), addresses a practical engineering challenge: the repair of 2010 steel roll dies using manual arc surfacing. The authors from Xi'an Jiaotong University, Northwest Institute for Nuclear Technology, and Jinan Gas Company conducted a systematic analysis of the weldability of 2010 steel, selected appropriate surfacing materials, and optimized process parameters to achieve satisfactory repair results. The paper appears in Volume 6 of the 1999 issue (pages 25-27) and is classified under TG455 (welding technology).
Weldability Analysis of 2010 Steel
2010 steel is a low-carbon steel containing approximately 0.20% carbon, 1.00% manganese, and trace amounts of silicon. Its weldability is generally considered good due to the low carbon equivalent (CE ≈ 0.43%), but the repair of roll dies introduces specific challenges:
- High work-hardening capacity: Roll dies undergo severe plastic deformation during rolling operations, leading to significant strain hardening in the surface layers.
- Residual stress state: The hardened die surface carries high compressive residual stresses that can be disrupted by the thermal cycle of surfacing.
- Hardness mismatch: The as-rolled surface hardness may reach 250-320 HB, while the base metal interior remains at 160-200 HB, creating a heterogeneous welding substrate.
- Carbon segregation: Rolling and subsequent heat treatment can cause localized carbon enrichment at grain boundaries, increasing the risk of cold cracking in the heat-affected zone.
Surfacing Material Selection
The selection of surfacing material is critical for roll die repair. The authors evaluated several options based on the following criteria:
| Selection Criterion | Requirement | Selected Material |
|---|---|---|
| Hardness matching | ≥ 250 HB after welding | J507 (E5015) or specialized hard-facing electrode |
| Dilution resistance | Minimum dilution from base metal | Preheated substrate with controlled heat input |
| Crack resistance | Low CE, good toughness | Low-hydrogen electrode type |
| Wear resistance | Suitable for rolling contact | Medium-carbon martensitic microstructure |
| Service temperature | ≤ 200°C continuous | No tempering required post-weld |
The authors selected a low-hydrogen shielded metal arc welding (SMAW) electrode, likely of the J507 (E5015) type or a specialized hard-facing variant, considering its excellent crack resistance and the ability to produce a martensitic weld metal with controllable hardness through post-weld heat treatment.
Process Parameters and Technique
Preheating Requirements
Given the strain-hardened condition of the roll die surface, preheating is essential to relieve residual stresses and reduce the cooling rate in the HAZ. The recommended preheat temperature is 200-250°C, applied uniformly using induction heating or torch preheating to avoid localized overheating.
Surfacing Parameters
| Parameter | Recommended Range | Rationale |
|---|---|---|
| Current type | DCEN (Direct Current Electrode Negative) | Deeper penetration, better wetting |
| Current range | 180-240 A (for 3.2 mm electrode) | Adequate deposition with controlled heat input |
| Arc length | 2-3 mm | Stable arc, reduced spatter |
| Travel speed | 150-200 mm/min | Uniform bead profile |
| Interpass temperature | ≤ 250°C | Prevent excessive grain growth |
| Number of passes | 2-3 layers | Build up sufficient repair thickness |
| Post-weld treatment | Stress relief at 550-600°C | Reduce residual stress |
Surface Preparation
The damaged area must be machined to a smooth contour with a gradual transition (minimum 2:1 fillet radius) to avoid stress concentration at the weld toe. Surface roughness should be Ra ≤ 6.3 μm. Any cracks or deep defects should be identified through magnetic particle inspection (MT) prior to surfacing, and root-treated by grinding to expose the sound metal.
Engineering Practice Insights
From a practical standpoint, this paper addresses a common maintenance scenario in rolling mill operations. Roll dies are expensive consumables, and their failure modes typically include:
- Surface cracking due to thermal fatigue during rolling cycles.
- Wear from repeated contact with hot steel strips.
- Galling at high temperatures where adhesive wear becomes dominant.
- Plastic deformation when the die encounters localized hard spots in the rolled material.
The repair approach described here follows a PDCA (Plan-Do-Check-Act) methodology: analysis of weldability (Plan), selection and application of surfacing material (Do), hardness and metallographic verification (Check), and optimization for production deployment (Act).
A key engineering insight is that the repair must restore not only geometric dimensions but also the functional surface characteristics—hardness, flatness, and surface integrity. The interpass temperature control is particularly important; exceeding 250°C can cause tempering of the previously deposited layer, reducing its hardness and defeating the purpose of the repair.
Defect Prevention and Quality Control
| Defect Type | Cause | Prevention Measure |
|---|---|---|
| Cold cracking | Hydrogen embrittlement in HAZ | Low-hydrogen electrode, preheating, immediate post-weld heating |
| Hot cracking | Low melting point inclusions | Proper flux chemistry, controlled sulfur content |
| Lack of fusion | Excessive travel speed | Monitor bead profile, adjust parameters |
| Excessive dilution | High heat input | Reduce current, increase travel speed |
| Hardness unevenness | Inconsistent interpass temperature | Use temperature monitoring strips |
Post-repair inspection should include hardness testing (minimum 3 points across the repair area), MT inspection for surface cracks, and dimensional verification using a surface plate or laser scanner to confirm the die geometry meets rolling tolerance specifications.
Study Reflection
This 1999 paper, while relatively straightforward in its methodology, embodies the practical engineering philosophy of the era—problem-oriented, material-driven, and process-optimized. The systematic approach to weldability assessment, material selection, and parameter optimization remains relevant today. For modern engineers working with advanced high-strength steels (AHSS) or hot-rolled coil (HRC) dies, the fundamental principles described here still apply, though the material systems and process capabilities have advanced significantly. The emphasis on understanding the base metal condition before selecting repair procedures is a lesson that should not be overlooked in today's rush toward production efficiency.