Abstract: The electroslag surfacing process using seamless flux-cored ribbons was successfully conducted through experiments. The optimal parameters for electroslag surfacing of these ribbons were determined using the orthogonal experimental method. Preface Flux-cored submerged arc welding has been widely used in applications such as guide rollers of continuous casting machines, extrusion press rollers, and the surface of large-diameter power station valves. One of the most significant advantages of this technique is its ability to adjust the type, content, and ratio of alloy within the core, allowing for the creation of a hard, wear-resistant coating that is difficult to produce as a solid ribbon. This makes it possible to use a continuous strip-shaped consumable for automatic surfacing [1]. However, the high temperature involved in flux-cored submerged arc welding often leads to significant loss of precious metals. By combining flux-cored wire with electroslag welding technology, the deposition efficiency and alloy utilization can be improved, while reducing the dilution rate. This method is more advanced than traditional submerged arc welding, offering better technical and scientific rationality. 1. Characteristics of Flux-Cored Strips The seamless flux-cored welding strip is made by wrapping various alloys inside a metal sheath. Compared to solid wires, seamless flux-cored strips have several unique characteristics: the core is composed of metal powders held together by mechanical bonding between granules, powder particles, and the outer metal skin. This allows for the production of alloy compositions that are difficult to roll into solid ribbons. Typically, the thickness of seamless flux-cored strips is ≥ 1.0 mm. When compared to solid ribbons of the same cross-sectional area, flux-cored ribbons with a core thickness ≤ 0.5 mm have a smaller heating area during electroslag surfacing. Additionally, the cross-sectional dimensions of flux-cored tapes show that the core thickness is greater than the thickness of both sides, while the middle metal skin is thinner than the outer layers. Flux plays a crucial role in the electroslag surfacing process of these strips. The electroslag welding flux must not only have good conductivity but also excellent slag removal properties [2]. Based on literature reviews and the specific characteristics of flux-cored strips, a ceramic flux designated H06 for electroslag surfacing was developed. The alkalinity (B1) of the flux was calculated using the formula recommended by the International Welding Society: B1 ≈ 3.07, which indicates a high-alkalinity flux. 2. Determination of Optimal Electroslag Surfacing Parameters Using the Orthogonal Method The test conditions included: a Lincoln DC-1000 power supply with reverse polarity, Q235 steel plates measuring 240 mm × 80 mm × 16 mm, an XY function recorder for voltage acquisition, B3 and DF flux-cored ribbons (20 mm × 1.0 mm), and H06 ceramic flux. In determining the process parameters, an approximation method was primarily used, while the orthogonal experiment method was applied to find the best parameters. Factors affecting the stability of the electroslag surfacing process include the flux-cored tape, flux, surfacing voltage, current, speed, and flux layer thickness. Therefore, the surfacing parameters were selected based on the orthogonal method, as shown in Table 1. Table 1: Surfacing Parameters Selected for Orthogonal Experiments This is an orthogonal experiment with 3 factors at 3 levels and 1 factor at 2 levels. The orthogonal table is shown below. The electroslag surfacing parameters of flux-cored strips should be evaluated from three aspects: 1) no short circuit, 2) no significant arc, and 3) low dilution rate. These criteria serve as indicators of the stability of the electroslag surfacing process. If short circuits or noticeable arcs occur, the process is considered unstable. These phenomena can be recorded by the XY function recorder and analyzed through waveform detection. If a short circuit occurs or a significant arc is generated, it is rated “0â€; otherwise, it is rated “1â€. A dilution rate above 20% is also rated “0â€, otherwise “1â€. Among them: A – deposited metal area, B – molten matrix metal area. Table 2: Orthogonal Test Table for Electroslag Surfacing Standard of Seamless Flux-Cored Welding Zone To evaluate the overall stability of the flux-cored electroslag welding process, scores from the three evaluation indices were summed to obtain a comprehensive total score. Table 3 shows the overall specifications of the electroslag surfacing process for the flux-cored welding zone. Table 3: Synthetic Scoring of Each Parameter of Electroslag Welding with Flux-Cored Tape The K1, K2, and K3 values in Table 3 correspond to the parameter columns in Table 2. The comprehensive scores for positions 1, 2, and 3 in the orthogonal table were added, and then K1, K2, and K3 were divided by 6 to represent the average composite scores for different specification levels. The results were analyzed visually. As shown in Figure 1, the best parameters for the electroslag surfacing of the flux-cored tape in this experiment are: surfacing voltage of 29 V, surfacing current of 600 A, and surfacing speed of 150 mm/min. 3. Conclusion 1. The optimal parameters for the electroslag surfacing of the flux-cored welding zone in this experiment are: surfacing voltage 29 V, surfacing current 600 A, and surfacing speed 150 mm/min. Figure 1: Analysis of the Relationship Between Each Specification Parameter and Comprehensive Score (4) Alloy transition coefficient: When using flux-cored tape in submerged arc welding, the Cr alloy transition coefficient is 70%. With seamless flux-cored strips in electroslag surfacing, the Cr alloy transition coefficient can exceed 90%. 4. Application This process has been successfully applied in the manufacturing and repair of large-diameter power station valves, concrete pump scrapers, and other products, achieving excellent results. Irregular Blow Molding,Injection Special Shaped Parts,Plastic Injection Special Shaped Parts,Plastic Irregular Tube Dandong Jinggong Heat Preservation Appliance Factory , https://www.jgplastic.com
Keywords: seamless flux-cored strip, electroslag surfacing, orthogonal method
Table 1: Surfacing Parameters of Orthogonal Experimental Method
Table 2: Electroslag Surfacing Criterion for Seamless Flux-Cored Strip
Table 3: Synthetical Instance of Surfacing Criterion Parameters
2. Compared with submerged arc welding, the characteristics of seamless flux-cored electroslag surfacing include:
(1) Low dilution rate: The dilution rate in submerged arc welding is generally above 30%, while electroslag surfacing with seamless flux-cored strips can stably control the dilution rate below 20%.
(2) Voltage waveform: During submerged arc welding, short circuits and arcs occur frequently, but during electroslag surfacing, the voltage waveform is smooth.
(3) Arc occurrence: In flux-cored submerged arc welding, the arc is common, but in electroslag surfacing, the arc is rarely seen due to the exposed slag pool, as shown in Figure 2.
(4) Alloy transition coefficient: The Cr alloy transition coefficient is 70% with submerged arc welding, but over 90% with electroslag surfacing using seamless flux-cored strips.
(5) High deposition efficiency: The deposition rate can reach up to 30 kg/h.
Fig. 1: Connection Analysis of Criterion Parameters and Synthetic Instances
(5) High deposition efficiency: The deposition rate can reach up to 30 kg/h.