Submerged Arc Welding Device for Squeeze Rolls in Roller Presses

Literature Overview

The study of submerged arc welding (SAW) devices applied to squeeze rolls in roller presses represents a critical intersection of heavy equipment repair technology and overlay welding engineering. Squeeze rolls in roller presses are subjected to extreme mechanical loading, abrasion, and thermal cycling during continuous production operations. The base material is typically a medium-carbon steel or low-alloy steel, and the working surface requires a hardfacing overlay to resist wear. This literature provides a comprehensive account of the design, operation, and performance evaluation of a dedicated SAW cladding system tailored specifically for the geometry and service conditions of squeeze rolls.

The study is significant because squeeze rolls present unique challenges: their cylindrical geometry with relatively large diameters (typically 300 to 800 mm) and the requirement for uniform overlay thickness around the entire circumference demand a highly automated and precisely controlled welding system. The literature addresses electrode selection, flux formulation, welding parameter optimization, and post-weld inspection protocols in a systematic manner.

Core Technical Content

Base Material and Overlay System Selection

The base material for squeeze rolls is generally 45 steel or 40CrNiMo steel, with a hardness in the range of 180 to 240 HB. The overlay material must provide hardness in the range of 45 to 55 HRC to resist abrasive wear while maintaining sufficient toughness to avoid catastrophic spalling under impact loading. The literature evaluates several overlay systems, including high-carbon chromium steel (Cr12MoV-type), cobalt-based hardfacing alloys, and iron-based high-alloy alloys with carbide-forming elements such as vanadium, molybdenum, and tungsten.

The selection of the overlay system is governed by the nature of the abrasion mechanism. For dry abrasive conditions typical of metal rolling, iron-based alloys with Cr3C2 and VC carbides are preferred. For wet or oxidizing environments, cobalt-based alloys offer superior resistance to thermal fatigue and oxidation.

Welding Device Design and Configuration

The SAW device described in the literature employs a multi-torch configuration mounted on a rotating fixture that holds the squeeze roll. The device integrates the following subsystems:

• A roll fixture with hydraulic clamping to ensure concentricity within 0.05 mm
• A multi-channel SAW power supply capable of simultaneous operation of 2 to 4 welding heads
• A flux delivery and recovery system to minimize flux consumption and ensure consistent flux coverage
• A water-cooled copper backing ring to promote proper root formation on the first pass
• An automatic wire feed mechanism with independent speed control for each torch

The multi-torch arrangement is particularly important for large-diameter rolls where a single torch would require excessive circumferential passes, leading to high heat input and potential distortion. By distributing the heat input across multiple torches, the peak temperature at any point on the roll surface is reduced, and the number of passes is minimized.

Welding Parameter Optimization

The literature presents a systematic parameter study using a Taguchi L9 orthogonal array to identify the optimal combination of welding current, voltage, wire feed speed, and travel speed. The key findings are summarized below:

The optimal parameters yield a single-pass deposition width of approximately 25 mm and a penetration depth of 2 to 3 mm. The dilution ratio between the base metal and the overlay is maintained below 15%, which is critical for achieving the target overlay hardness. The use of agglomerated basic flux provides superior deoxidation and slag protection, resulting in fewer slag inclusions and porosity defects.

Defect Analysis and Countermeasures

The literature identifies several common defects encountered during SAW cladding of squeeze rolls and proposes countermeasures:

Cracking is the most critical defect because it can propagate during service and lead to sudden roll failure. The literature recommends a post-weld stress-relief treatment at 600°C for 2 hours per 25 mm of roll thickness to reduce residual stresses and improve the toughness of the overlay.

Integration with Engineering Practice

From my experience in heavy equipment repair, the successful application of SAW cladding to squeeze rolls depends not only on the welding parameters but also on meticulous pre-weld preparation. Surface cleaning to remove rust, scale, and oil is essential, and the surface roughness should be controlled to Ra less than 6.3 μm to ensure good arc stability and uniform deposition. The preheat temperature must be carefully controlled to avoid overheating the base metal, which can reduce its mechanical properties and increase the risk of distortion.

In practice, I have observed that the multi-torch SAW approach significantly reduces the total cladding time compared to single-torch methods, but it requires careful coordination of torch positions to avoid overlap defects. The spacing between adjacent torches should be approximately 1.5 times the deposition width to ensure complete coverage without excessive overlap.

Key Questions and Reflections

The literature raises an important question regarding the long-term performance of the overlay under thermal cycling. While hardness and wear resistance are well characterized in laboratory conditions, the fatigue life of the overlay under repeated heating and cooling cycles during actual rolling operations is less well understood. I believe that future research should focus on thermal fatigue testing of the overlay under conditions that simulate actual service, including cyclic temperature changes and mechanical loading.

Another reflection is the economic balance between overlay thickness and service life. A thicker overlay provides longer wear life but increases the number of welding passes, the total heat input, and the risk of distortion and cracking. The optimal thickness must be determined by considering the expected service life, the cost of downtime, and the cost of the cladding operation.

Study Insights and Implications

This literature provides a valuable reference for engineers involved in the repair and maintenance of heavy industrial equipment. The systematic approach to parameter optimization, combined with detailed defect analysis, offers a practical framework for developing SAW cladding procedures for similar applications. The emphasis on multi-torch configuration highlights the importance of process innovation in improving productivity and quality.

The study reinforces the principle that successful cladding is not merely a matter of selecting the right material but requires careful attention to every aspect of the process, from surface preparation to post-weld treatment. The integration of automation and precision control is essential for achieving consistent quality on large cylindrical components. Engineers should adopt a holistic approach to cladding design, considering the base material, overlay system, welding process, and service environment as an integrated system rather than as isolated elements.