Formation and Falling Mechanism of Black Oxide Layers in High Speed Steel Rolls during Hot Strip Milling

Hwang, Keun Chul; Lee, Sunghak; Lee, Eon-Sik

doi:10.2355/tetsutohagane1955.83.6_383

Cited by 10 publications

(2 citation statements)

References 1 publication

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“…The size of the cell structure plays a critical role in determining the overall distribution of carbides, thereby affecting the thermal fatigue and fracture toughness. 25 Thus, these microstructural factors should be optimised to manufacture HSS rolls with excellent performance.…”

Section: Discussionmentioning

confidence: 99%

Correlation of microstructure and fracture properties of five centrifugal cast high speed steel rolls

Kim¹,

Lee²,

Lee³

2007

Materials Science and Technology

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The present study is concerned with effects of microstructural factors such as distribution and fraction of coarse carbides located along solidification cell boundaries and characteristics of tempered martensitic matrix on fracture properties of five high speed steel (HSS) rolls manufactured by a centrifugal casting method. In situ microfracture observation, fracture toughness measurement and fractographic observation were conducted on these rolls to clarify fracture mechanisms. The in situ observation results indicated that coarse carbides located along cell boundaries provided easy intercellular fracture sites under a low stress intensity factor level. In the rolls whose intercellular carbide fraction and matrix hardness were high, fracture easily occurred under a low stress intensity factor. On the contrary, in the rolls where a small amount of intercellular carbides was distributed on the relatively ductile matrix of lath tempered martensite, the fracture path was accompanied by a considerable amount of plastic deformation including shear band formation, thereby resulting in high fracture toughness. In order to obtain better microstructure, hardness and fracture toughness of the HSS rolls, the minimisation of intercellular carbides, the refinement of carbides and the improvement of the matrix characteristics by controlling alloying elements and heat treatment conditions were suggested.

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Section: Discussionmentioning

confidence: 99%

Correlation of microstructure and fracture properties of five centrifugal cast high speed steel rolls

Kim¹,

Lee²,

Lee³

2007

Materials Science and Technology

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“…in general independently nucleates and grows to form a cell, or grows on the basis of primary ␥, [29] VC particles are L ϩ ␣ } ␥ ϩ VC (U 1 ; ternary peritectic, at 1370 ЊC) coarsely precipitated mainly along solidification cell boundaries (Figures 5(a) and (b)). Since the temperature reaches L } ␥ ϩ VC ϩ Fe 3 C (E 2 ; ternary eutectic, at 1120 ЊC) thereby resulting in the reduced formation of VC carbides.…”

Section: A Thermal Analysis Of Electron-beam Irradiationmentioning

confidence: 98%

Correlation of microstructure with hardness and wear resistance of VC/steel surface-alloyed materials fabricated by high-energy electron-beam irradiation

Euh

Lee

2003

Metall Mater Trans A

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Correlation of microstructure with hardness and wear resistance of VC/carbon steel surface-alloyed materials fabricated by high-energy electron-beam irradiation was investigated. The mixtures of VC powders and flux (50 pct MgO-50 pct CaO or CaF 2 ) were deposited on a plain carbon steel substrate, and subsequently irradiated using a high-energy electron beam. The surface-alloyed layers of 1.2 to 3 mm in thickness were homogeneously formed without defects, and contained a large amount (about 10 vol pct) of VC precipitates in the bainitic or martensitic matrix. This microstructural modification including the formation of hard precipitates and hardened matrix in the surface-alloyed layers improved hardness and wear resistance. Particularly in the surface-alloyed material fabricated with the lower input energy density, the wear resistance was greatly enhanced over the steel substrate because of the increased size and volume fraction of VC particles, although the thickness of the surface-alloyed layer decreased. Microstructural modifications including melting, solidification, precipitation, and phase transformation of the surface-alloyed layer were also predicted from a thermal transfer modeling and a Fe-V-C ternary phase diagram. The predicted results were found consistent with those data from actual electron-beam irradiation and microstructural analysis.

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Composition, microstructure, hardness, and wear properties of high-speed steel rolls

Park

Lee

1999

Metall Mater Trans A

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108

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The effects of alloying elements on the microstructural factors, hardness, and wear properties of four high-speed steel (HSS) rolls fabricated by centrifugal casting were investigated. A hot-rolling simulation test was carried out using a high-temperature wear tester capable of controlling speed, load, and temperature. The test results revealed that the HSS roll containing a larger amount of vanadium showed the best wear resistance because it contained a number of hard MC-type carbides. However, it showed a very rough roll surface because of cracking along cell boundaries, the preferential removal of the matrix, and the sticking of the rolled material onto the roll surface during the wear process, thereby leading to an increase in the friction coefficient and rolling force. In order to improve wear resistance with consideration to surface roughness, it is suggested that a reduction in the vanadium content, an increase in solid-solution hardening by adding alloying elements, an increase in secondary hardening by precipitation of fine carbides in the matrix, and formation of refined prior austenite grains by preaustenitization treatment be employed to strengthen the matrix, which can hold hard carbides in it.

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Formation and Falling Mechanism of Black Oxide Layers in High Speed Steel Rolls during Hot Strip Milling

Cited by 10 publications

References 1 publication

Correlation of microstructure and fracture properties of five centrifugal cast high speed steel rolls

Correlation of microstructure and fracture properties of five centrifugal cast high speed steel rolls

Correlation of microstructure with hardness and wear resistance of VC/steel surface-alloyed materials fabricated by high-energy electron-beam irradiation

Composition, microstructure, hardness, and wear properties of high-speed steel rolls

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