LB-52U welding rod is a low-hydrogen manual arc welding rod produced by KOBELCO (Kobe Steel, Ltd.) in Japan, specifically designed for root passes in pipeline and structural steel welding. It is renowned for its unique **single-sided welding with double-sided forming** capability. After two years of research and development, we have successfully developed an alternative to LB-52U—AK-52U. We will now focus on discussing the performance and process characteristics of AK-52U.
一. **Product Overview and Technical Standards**
1. **Model and Certification**
– International Equivalent: AWS A5.1 E7016 (American Standard), suitable for welding low-carbon steel and 490MPa-grade (50kgf-grade) high-strength steel.
– Typical composition of deposited metal: Carbon (C) 0.08%, Manganese (Mn) 0.86%, Silicon (Si) 0.64%, with low phosphorus and sulphur content (P ≤ 0.012%, S ≤ 0.008%), ensuring weld purity.
2. **Core characteristics**
– **Single-sided welding with double-sided formation**: When welding the root pass of a pipe, uniform formation on both sides can be achieved without back-side root cleaning, significantly improving efficiency.
– **Low-hydrogen design**: Strictly limits the content of diffusible hydrogen, reducing the risk of cold cracks, particularly suitable for high-strength steel and thick plate structures.
– **Process-friendly**: Stable arc, excellent slag removal, and aesthetically pleasing weld bead formation, commonly used in welder skill assessments and demonstrations.
二. **Key Process Parameters and Operating Techniques**
1. **Pre-treatment Requirements**
– Drying conditions: **300–350°C for 30–60 minutes** to prevent moisture absorption causing porosity or cracks.
2. **Welding Parameter References**
| Electrode Diameter (mm) | Flat Welding Current (A) | Vertical/Overhead Welding Current (A) | Base Pass Current (A) |
|—————-|—————|———————|—————— -|
| 3.2 | 90–130 | 80–120 | 60–110 |
| 4.0 | 130–180 | 110–170 | 90–140 |.
– **Polarity requirements**: DC reverse polarity (DC+) or AC.
3. **Operating techniques**
– **Key points for root pass welding**: Use **short arc operation** (arc length ≤ electrode diameter), lightly oscillate the electrode to form a melt hole, then quickly raise the arc. The electrode movement should be a small sawtooth pattern back and forth.
– **Melt Pool Control**: The melt pool should be 1/2 on the inner side and 1/2 on the outer side of the groove. Follow-up frequency: 1–1.5 seconds per pass to avoid weld spatter or concavity.
– **Arc Starting/Extinguishing**: Start the arc on the side of the groove; when extinguishing the arc, pull back 10–15 mm to the side wall to prevent cold shrinkage holes.
三. **Application Areas**
– **Key Industries**: Shipbuilding, pressure vessels, bridge and building steel structures, pipeline engineering (especially for single-sided welding with double-sided forming butt joints).
– **Suitable Materials**: Low-carbon steel (e.g., Q235), 490 MPa-grade high-strength steel (e.g., SM490).
四. **Comparison with Other Welding Rods in the Same Series**
| Model | AWS Equivalent | Characteristics Differences | Applicable Scenarios |
|————|———— -|——————————————|—————————– -|
| **AK-52U** | E7016 | Specialised for single-sided welding with double-sided formation, impact toughness 130J (0°C) | Root welds in pipelines |
| **AK-52** | E7016 | General-purpose, impact toughness 210J (0°C) | Shipbuilding, pressure vessel welding in all positions |
| **AK-62UL**| E9016-G | Ultra-low hydrogen, resistant to -20°C low temperatures | 55–60 kgf grade high-strength steel (e.g., offshore platforms) |.
**Summary**
The core value of the AK-52U welding rod lies in its **efficient single-sided welding with double-sided forming capability** and **low-hydrogen crack resistance**, making it particularly suitable for confined space operations such as pipeline welding. During operation, strict control of drying processes, current parameters, and melt pool dynamics is required to avoid defects such as incomplete penetration or concavity.