Method of setting Nozzle intervals at the finishing scale breaker

Kim, Sung Cho; Choi, Jong Wook; Choi, Jin Won

doi:10.1007/bf02983401

Cited by 4 publications

(5 citation statements)

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“…An experimental study confirmed that having neighboring jets which collide with each other can significantly reduce descaling performance [10] and significantly increase cooling [4]. Industrial descaling units usually have nozzles rotated by offset angle β set to 15° (see Figure 1 right) to avoid the water jets colliding before the water hits the descaled surface [5,7,[25][26][27][28][29][30][31][32]. The only exception are patents [33,34] where the offset angle is set to 0° but the configurations produce two discontinuous lines trying to avoid problem in overlap area.…”

Section: Introductionmentioning

confidence: 94%

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optimal hydraulic descaling

Pohanka

Kotrbáček

Resl

et al. 2020

METAL 2020 Conference Proeedings

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Hydraulic descaling is an inherent part of the hot rolling process but can sometimes also be applied in the heat treatment process, continuous casting and other processes. The need for optimal descaling is linked with the quality of the final product. The goal is usually simplified to the complete removal of the scale layer from the hot surface. The descaled surfaces are often wide and a number of nozzles must be used. The quality problems are almost exclusively connected with the overlap of water jets. An experimental study of overlap optimization is presented in this paper. A new approach using in-line configuration of jets is introduced and discussed. This paper also describes why even the completely oxide-free surface achieved after descaling the unit can be a far from optimal solution. Thermal strips on the hot surface cause much more intensive oxidation of the hot part and much slower oxidation in the cold strips on the descaled surface. The speed of oxide formation on the steel surface is exponentially dependent on the surface temperature. Temperature nonhomogeneity after descaling in the rolling process can cause the same defects on the surface of the final product as poor descaling. Temperature aspects with links to heat loss and secondary oxidation are discussed.

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Section: Introductionmentioning

confidence: 94%

“…The most crucial factors that affect the process can be divided into mechanical effects and thermal effects [3,4]. The dominant parameter is impact pressure, influencing both mechanical and thermal action [5,6]. The impact pressure depends on nozzle feeding pressure, nozzle quality and nozzle standoff from the descaled surface [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

optimal hydraulic descaling

Pohanka

Kotrbáček

Resl

et al. 2020

METAL 2020 Conference Proeedings

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“…Configurations C1 and C2 simulated a very wide washout area with a smooth pressure reduction. The configurations have an offset angle of 15 • , which is also commonly used in the industry [28,29].…”

Section: First and Second Configurationmentioning

confidence: 99%

The Effect of Water Jet Overlaps in a Descaler on the Quality of Surface of the Hot Rolled Steel

Pohanka,

Votavová,

Resl

et al. 2023

Metals

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Hot rolling is a highly efficient steel processing method involving the heating and subsequent rolling of semi-finished cast products within mills; however, heating results in the formation of an undesirable, inhomogeneous oxide layer on the surface. Removal of this layer, known as scales, prior to rolling is essential to prevent scales from being rolled into the surface. The scales are removed in the descaler. Most descalers use multiple high-pressure hydraulic descaling nozzles with overlapping sprays. This setting can cause excessive cooling in the overlap area, uneven descaling of the surface, and the presence of residual scales. It can also result in uneven cooling at the finishing line. This study illustrates a typical nozzle configuration commonly used in industrial plants in the hydraulic descaling process and compares its results with a new configuration. The research focuses on examining the overlap area and the washout area of the sprays. The goal is to address the inhomogeneous descaling problem and propose procedures to prevent residual scales. It was shown that one of the problematic areas is the washout area, where the average thickness of the remaining scales was more than four times higher than other descaling areas. Reducing the offset angle has proven to be a good way to eliminate the washout area and achieve a homogeneous descaling process.

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“…These are 1) spray angle α (acting in cross width direction to DR) (generally between 15-45 o ) 2) spray thickness (or depth) angle φ (parallel to direction of rolling DR) (generally between 1.5 and 3 o , but value not quoted by manufacturer despite its criticality) 3) nozzle twist angle γ (deviation from cross width direction) (generally 15 ο ) 4) lead or rake angle β (inclination from DR, usually between 0 and 15 o , max 30 o ). The spray distance H can be increased H(+) or decreased H (-) depending on the lead (rake) and offset (or twist) angle interaction [10]. It can be observed that geometrically the standoff decreases at left of nozzle (assuming positive offset and rake) and increases at right end side from nozzle orifice centre (or COG of imprint) with ever increasing rake and offset (or twist) angle affecting also the spray width.…”

Section: Analytical Calculation Of Key Descalability Criteriamentioning

confidence: 99%

“…Optimisation using NSGAII was also performed to output optimum set-up based on IP and overlap target (not shown). It can be observed that in view of large increase in surface fracture energy, criteria of equations (10,11) based on brittle fracture cannot be satisfied, except at low temperature where γFeO ~3-4J/m 2 . Pareto plots (IP, descaling energy, overlap, etc.)…”

Section: Study Of Influence Of Thermal Effectmentioning

confidence: 99%

Advancement in Understanding of Descalability during High Pressure Descaling

Farrugia

Richardson

Lan

2014

KEM

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This paper building upon studies [1‐8] describes a subset of the High Pressure Water (HPW) descaling strategy developed at Tata Steel UK to optimise descaling set-ups for range of steel grades prone to adherent primary scale such as in high alloy steels (Si, Ni, Cr). Effective primary descaling, i.e. descaling post furnace discharge via washbox or alternative technologies is imperative to obtain good surface quality and conditioning of the surface state as well as the morphology, growth and behaviour of the secondary/tertiary scale. This paper primarily focuses on analytical descaling concepts for both mechanical and thermal outputs for flat jet nozzle and process factors. This approach has been linked to recent developments for oxide scale evolution during rolling and descaling [8].

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Method of setting Nozzle intervals at the finishing scale breaker

Cited by 4 publications

References 1 publication

optimal hydraulic descaling

optimal hydraulic descaling

The Effect of Water Jet Overlaps in a Descaler on the Quality of Surface of the Hot Rolled Steel

Advancement in Understanding of Descalability during High Pressure Descaling

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