Composite Casting Special-Shaped Roll for Steel Pipe Mills
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Solution Overview
Problem
Current methods for producing special-shaped rolls for steel pipe and cold forming sectional steel face challenges in achieving the required combination of abrasion resistance, impact resistance, and rapid cooling/heating resistance while being cost-effective and material-efficient, due to limitations in existing manufacturing processes such as forging and centrifugal casting.
Innovation Solution
A composite casting method using a double-liquid double outer mold casting technique to create a bimetal or single-metal special-shaped roll with a high chromium cast iron or alloy nodular cast iron outer layer and a cast steel or ductile cast iron inner layer, ensuring a thick working layer with high strength and toughness, and optimizing material utilization and processing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single metal material is used for special-shaped rolls, then manufacturing process is simple, but it is difficult to achieve both high abrasion resistance and high toughness simultaneously
Solution Approach 1:
The patent applies composite materials by creating a bimetallic roll structure where the outer layer is made of high chromium cast iron or alloy nodular cast iron for abrasion resistance, while the inner layer is made of cast steel or ductile cast iron for toughness and strength. This composite structure allows each layer to contribute its superior properties, resolving the contradiction between manufacturing simplicity and comprehensive performance requirements.
Solution Approach 2:
The patent implements local quality by differentiating the material composition between the outer working layer and the inner core layer. The outer layer is specifically engineered with high chromium content for wear resistance where it contacts the material being processed, while the inner layer provides structural support and toughness. This localized material optimization allows the roll to meet different performance requirements in different regions.
2Strength
If forging process is used to manufacture special-shaped rolls, then material strength can be improved, but material utilization rate drops below 50%
Solution Approach 1:
The patent changes the manufacturing parameter from forging to casting, specifically using composite casting method. This parameter change allows the roll to be formed directly into its final shape with complex internal structures and curved surfaces, achieving near 100% material utilization while maintaining or exceeding the mechanical properties previously only attainable through forging.
Solution Approach 2:
The patent applies preliminary action by designing the mold cavity to precisely match the final roll geometry including the curved surface with large diameters at both ends and small middle diameter. This preliminary shaping in the casting mold eliminates the need for extensive subsequent machining and material removal, thereby maximizing material utilization while achieving the required strength and geometric complexity.
3Ease of manufacture
If conventional normalization process is used for high-alloy ductile iron rolls, then processing is simpler, but strength and toughness are much lower compared to isothermal quenching
Solution Approach 1:
The patent changes the heat treatment parameter from conventional normalization to isothermal quenching for the high-alloy ductile iron outer layer. This parameter change transforms the microstructure to achieve superior strength and toughness while maintaining the simplicity of the overall manufacturing process. The isothermal quenching process allows the ductile iron to attain mechanical properties comparable to or exceeding forged rolls.
4Loss of substance
If centrifugal casting is used to manufacture bimetal structure rolls, then material utilization can be improved, but the process becomes difficult and requires multiple sets of molds
Solution Approach 1:
The patent applies segmentation by dividing the casting process into two sequential steps: first casting the inner layer, then casting the outer layer over it. This segmented approach uses a single mold that is reused after removing the inner layer, achieving bimetallic structure with high material utilization while avoiding the complexity of centrifugal casting and multiple mold sets required by conventional methods.
Data Source
AI summary
A composite casting special-shaped roll is compounded of two parts: an inner layer and an outer layer. The shape of body of the roll is curved surface, and a center hole is arranged for mount the shaft in that central axis of roll. The casting mold is designed into two parts, namely inner cast mold and outer cast mold through the curved surface design and mold design of the roll body. The composite casting special-shaped roll with the wear-proof working layer of the roll body that is resistant to impact, rapid cooling and heating resistance and the high-strength and high-toughness core is prepared by separate casting. It meets the requirements of the service conditions of rolls used by the steel pipe and cold forming sectional steel rolling mill and other equipment, improves the service life of the roll, saves the alloy material and reduces the manufacturing cost.