Composite Cemented Carbide Roll Structure for Long Cold-Rolling Service
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Solution Overview
Problem
Existing composite cemented carbide rolls face challenges in achieving high wear resistance and mechanical strength for cold rolling of metal strips, while also being cost-effective and capable of producing long rolls with diameters over 200 mm and lengths over 2000 mm, due to issues with residual stress, cracking, and limitations in HIP furnace capacity.
Innovation Solution
A composite cemented carbide roll design featuring an inner layer of iron-based alloy with a metallurgically bonded outer layer of cemented carbide, where the outer layer comprises 55-90% WC particles and 10-45% Fe-based binder phase, and an intermediate layer with specific compositions to reduce residual stress and enhance compressive yield strength, along with a production method using HIP treatment to integrate the layers and extend the roll length by welding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cemented carbide is used for rolls to achieve wear resistance and surface roughening resistance, then rolling quality is improved, but the roll becomes expensive and difficult to form into large products
Solution Approach 1:
The roll is divided into two functional segments: an inner layer made of ductile material (steel or cast iron) that is easy to manufacture in large sizes, and an outer layer made of cemented carbide that provides wear resistance. This segmentation allows each material to fulfill its optimal function while overcoming the limitations of using pure cemented carbide for the entire roll.
Solution Approach 2:
The invention creates a composite structure combining cemented carbide (for wear resistance) with ductile material (for toughness and ease of manufacture). This composite approach allows the roll to simultaneously achieve the wear resistance of cemented carbide and the manufacturability of conventional materials, enabling production of large-diameter rolls at lower cost.
2Ease of manufacture
If a cemented carbide sleeve is pressure-fixed to a shaft using heat-expanded spacers and fixing members, then the roll structure is assembled, but the assembling structure becomes complicated requiring high assembling accuracy and many steps
Solution Approach 1:
The invention merges the inner layer and shaft into a single integrally-formed component, eliminating the need for separate fixing members, spacers, and assembly steps. This integration simplifies the overall structure and manufacturing process while maintaining the functional benefits of a fitted sleeve design.
Solution Approach 2:
The inner layer is designed to be self-supporting and integrally connected to the shaft, eliminating the need for external fixing mechanisms. The structure serves itself by being manufactured as one piece, thereby removing the complexity of assembly operations and fixing components.
3Strength
If the outer layer and inner layer are bonded by HIP treatment to reduce residual stress, then bonding strength is improved, but a large HIP furnace is required for long rolls increasing running cost
Solution Approach 1:
The invention optimizes the composition parameters of the binder phase (specifically Ni content at 0.5-10% and Cr content at 0.5-5%) to achieve sufficient bonding strength and residual stress reduction through controlled cooling transformation, thereby reducing or eliminating the need for expensive large-capacity HIP treatment for long rolls.
Solution Approach 2:
The invention utilizes phase transition of the binder phase during controlled cooling after sintering (specifically the transformation of austenite to martensite or bainite) to reduce residual stress and enhance bonding between the outer and inner layers, replacing the need for high-cost HIP treatment.
4Reliability
If cemented carbide with Co-Ni-Cr binder phase is used to reduce roll cost, then wear resistance is improved, but compressive yield strength becomes low causing dents during cold rolling
Solution Approach 1:
The invention carefully controls the composition parameters of the binder phase, specifically limiting Ni to 0.5-10% and Cr to 0.5-5%, and utilizes controlled cooling to transform the binder phase structure. This parameter optimization maintains wear resistance while achieving sufficient compressive yield strength to prevent dents during cold rolling.
Solution Approach 2:
The invention employs phase transition of the binder phase during controlled cooling (transformation from austenite to martensite or bainite) to significantly increase compressive yield strength. This phase transformation occurs after sintering, allowing the cemented carbide to maintain wear resistance while gaining the strength needed to prevent surface dents during cold rolling operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables high-quality continuous cold rolling with reduced dents on the roll surface, supports long roll lengths, and reduces production costs by minimizing residual stress and cracking, allowing for effective use in both cold and hot rolling applications.
Implementation Method 1
conduct hot isostatic pressing (HIP)
Implementation Method 2
the binder phase having a chemical composition comprising 0.5-10% by mass of Ni, 0.2-2.0% by mass of C, 0.5-5% by mass of Cr, and 0.1-5% by mass of W
Data Source
Figure 1~2
Figure 3~4
Figure 5~8
AI summary
A composite cemented carbide roll comprising an inner layer made of an iron-based alloy, and an outer layer made of cemented carbide which is metallurgically bonded to an outer peripheral surface of the inner layer; the cemented carbide of the outer layer comprising 55-90 parts by mass of WC particles and 10-45 parts by mass of an Fe-based binder phase having a particular composition; a shaft member and a shaft end member being metallurgically bonded to at least one axial end of the inner layer; the inner layer being made of an iron-based alloy containing 2.0% or more in total by mass of at least one selected from the group consisting of Cr, Ni and Mo; and the shaft member and the shaft end member being made of an iron-based alloy containing 1.5% or less in total by mass of at least one selected from the group consisting of Cr, Ni and Mo.