Laser Cladding Work Roll Surface for Thermal Fatigue Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Work rolls for hot and cold rolling mills face challenges in achieving adequate resistance to thermal fatigue and surface degradation, with existing methods often resulting in cracks, porosities, and inadequate strip cleanliness.
Innovation Solution
A method of laser cladding a steel substrate with a metal coating external layer composed of specific work tool steel composition, involving multiple sublayers, thermal treatment, and a combination of induction heating and laser cladding, to create a wear-resistant and crack-free surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If spin or centrifugal casting is used to manufacture work rolls with a tough core and wear-resistant surface, then the roll can withstand thermal fatigue and wear, but the surface quality and strip cleanliness are inadequate
Solution Approach 1:
The work roll is divided into two distinct parts: a core made by spin/centrifugal casting providing thermal fatigue resistance, and a surface layer applied by laser cladding providing high surface quality. This segmentation allows each part to be optimized independently for its specific function.
Solution Approach 2:
The invention uses a composite structure combining the cast core material with a laser-clad surface layer of different material composition. The surface layer contains higher carbon and alloying elements to achieve the required surface hardness and cleanliness, while the core maintains toughness and thermal fatigue resistance.
2Duration of action of moving object
If HSS rolls are used to improve roughness retention, then abrasive wear resistance is enhanced, but strip cleanliness remains inadequate
Solution Approach 1:
The surface layer composition is precisely controlled with specific ranges of carbon (1.5-4.5%), chromium (2-18%), molybdenum (0.5-7%), and other alloying elements. These parameter changes in material composition enable simultaneous achievement of roughness retention and strip cleanliness through laser cladding.
3Strength
If a thick wear-resistant layer is applied by laser cladding, then surface hardness and wear resistance increase, but cracks and porosities may form in the coating
Solution Approach 1:
The substrate is preheated to 150-300°C before laser cladding to reduce thermal gradients and prevent cracking. This preliminary thermal preparation ensures that the subsequent thick coating can be applied without forming defects.
Solution Approach 2:
The laser cladding process is performed in continuous passes with overlapping tracks to ensure uniform deposition and eliminate voids or porosities. The process maintains continuous heating and material deposition to prevent discontinuities in the coating.
4Reliability
If multiple alloying elements are added to increase carbide content for wear resistance, then surface durability improves, but manufacturing complexity and cost increase
Solution Approach 1:
The invention specifies precise compositional ranges for multiple alloying elements (C: 1.5-4.5%, Cr: 2-18%, Mo: 0.5-7%, V: 0.5-5%, W: 0.2-5%, Nb: 0-5%, Ti: 0-1%, Mn: 0.5-1%, Si: 0.2-3%, Ni: 0-3%) to optimize carbide formation while controlling manufacturing complexity through standardized material specifications.
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 method achieves improved thermal fatigue resistance, reduced surface degradation, and enhanced surface quality with a refined microstructure, leading to increased roll campaign life, productivity, and reduced roll flattening and bending.
Implementation Method 1
forming a melt pool on the surface of the rotating substrate by means of a laser beam
Implementation Method 2
a preheating of the substrate is performed thanks to a coating head combining induction heating with laser cladding process
Implementation Method 3
submitting the coated substrate to a thermal treatment made of a tempering treatment comprising a heating up to a temperature in the range 500-650°C followed by a holding at this temperature during a time comprised between 2 and 5 hours, in order to soften martensite and precipitate carbides
Data Source
Figure 1
Figure 2
Figure 3A
AI summary
The present invention relates to a method for manufacturing a rolling mill roll by laser cladding a steel axe substrate having a rotational symmetry axis with a metal coating external layer, said metal coating external layer having a work tool steel composition, comprising the steps of : - rotating the substrate around its axis of rotational symmetry; - forming a melt pool on the surface of the rotating substrate by means of a laser beam and affixing the coating layer by feeding a powder material into the laser-induced melt pool, wherein the composition for said metal coating external layer is essentially consisting of 0.5-3.5% C, 2-18% Cr, 0.5-7% Mo, 0.5-8% V, 0.2-5% W, 0-5% Nb, 0-1% Ti, 0.5-1% Mn, 0.2-3% Si and 0-3% Ni, the rest being Fe and inevitable impurities.