Submerged Arc Surfacing Device for Roller Press Squeeze Rollers

Literature Overview

This paper by Wang Yinjun, Huang Quanxin, Huang Xiang, Jiang Sheming, and Zhang Qifu (2019), published in Casting Technology, introduces a specialized submerged arc surfacing (SAW) device designed for the continuous surfacing of squeeze rollers in roller press mills used in mining and metallurgical industries. The device was developed at the National Engineering Laboratory for Advanced Metal Coating and Surface Treatment at the Central Iron and Steel Research Institute, with collaboration from Shanghai Meishan Steel. The work addresses a significant industrial need: the wear-resistant surfacing of large-diameter squeeze rollers that must withstand extreme abrasive wear from ore, limestone, and other mineral materials.

Application Context: Roller Press Squeeze Rollers

Roller press mills are used in mineral processing, cement production, and metallurgical operations to compress and granulate bulk materials. The squeeze rollers are the critical wearing components:

The severe abrasive wear environment necessitates regular resurfacing of the roller surface, and the efficiency and quality of this surfacing process directly impact plant availability and operating costs.

Device Design and Configuration

The surfacing device described in this paper is a purpose-built machine designed for continuous SAW surfacing of cylindrical rollers. The key design features include:

Structural Configuration

The device integrates multiple functional subsystems into a single platform:

1. Roller support and rotation system: A heavy-duty cradle that supports the roller weight and provides precise rotational control at variable speeds.
2. SAW welding head: A multi-wire or single-wire SAW torch mounted on a linear traverse mechanism that moves axially along the roller surface.
3. Flux feeding and recovery system: An automated flux delivery system that continuously supplies flux to the welding zone and recovers spent flux for reuse.
4. Preheating and post-heat treatment system: Integrated heating elements (gas-fired or electric) that provide controlled preheating before welding and post-weld heat treatment to reduce residual stress.
5. Slag removal system: A continuous slag removal mechanism that strips slag from the weld surface as the welding progresses, enabling multi-pass surfacing without manual intervention.
6. Cooling and monitoring system: Temperature sensors and cooling circuits that monitor the roller temperature and provide active cooling when necessary.

Operational Sequence

The device enables a fully automated surfacing process:

1. Preheating: The roller surface is heated to 200-300°C to reduce thermal stress and prevent cracking.
2. Surfacing welding: Multiple passes of SAW surfacing are applied sequentially, with the slag removal system operating between passes.
3. Post-heat treatment: The roller is maintained at a controlled temperature (typically 500-600°C) to relieve residual stresses.
4. Cooling: Controlled cooling to ambient temperature, with monitoring to prevent cracking.

Technical Advantages of the Automated Device

Compared to conventional manual or semi-automated surfacing methods, the device offers several significant advantages:

Surfacing Weld Metallurgy

The surfacing weld metal composition and microstructure are critical for achieving the required hardness and wear resistance. For mineral processing applications, typical surfacing compositions include:

The microstructure of the surfacing weld typically consists of martensite, bainite, and carbides, with the hardness controlled by carbon content and cooling rate. The automated device allows precise control of cooling rate through the integrated heating and cooling systems, enabling consistent microstructure and hardness across the entire roller surface.

Engineering Practice and Case Applications

The paper reports successful applications in mining and metallurgical industries, where the device has been used to resurface squeeze rollers in:

• Iron ore pelletizing plants
• Cement production lines
• Coal preparation facilities
• Mineral dressing operations

The reported results show that the automated surfacing process achieves:

• Uniform surface hardness within ±5 HRC across the entire roller surface
• Residual stress reduction of 30-50% compared to conventional methods
• Service life extension of 2-3 times compared to un-surfaced rollers
• Reduction in surfacing cycle time by 60-70%

Key Reflections and Technical Considerations

This paper represents a significant advancement in surfacing technology for heavy-duty industrial applications. The integration of heating, welding, slag removal, and heat treatment into a single automated system is a paradigm shift from the traditional approach of treating each step as a separate operation. For engineers designing surfacing systems for large cylindrical components, the key lessons are:

1. Process integration reduces cycle time and improves quality consistency.
2. Automated slag removal enables multi-pass surfacing without manual intervention, which is critical for achieving the required surface thickness.
3. Integrated heat treatment is essential for controlling residual stress, which directly impacts the fatigue life of the surfacing weld.
4. The device design must account for the specific geometry of the component, including diameter, length, and weight.

Future developments should focus on expanding the device's capability to handle larger diameters, incorporating real-time monitoring of weld quality (such as ultrasonic testing integrated into the welding head), and developing adaptive control algorithms that adjust welding parameters based on real-time measurements of temperature and geometry.