Podchlazování rozvalku v oblastech překryvu vodních paprsků při hydraulickém odstraňování okují

OVERCOOLING IN OVERLAPPING AREAS DURING HYDRAULIC DESCALING

conference paper

en

The production and processing of high quality grades of steel is connected with oxidation at high temperatures. Unwanted scales are formed on the steel surface, which is usually heated over 900°C. These scales are often removed by hydraulic descaling during production. In most cases where long, flat products are produced, one row of descaling nozzles is used. Because these flat jet nozzles are arranged in the row, the water spray from one nozzle interferes with the spray from neighboring nozzles. This zone is called an overlap area and oftentimes more scales remain here after the descaling process. An increased amount of scales left behind result in a lower quality final product. The typical configuration with an inclination and twist angle equal to 15° was studied. Heat transfer coefficients (HTC) and surface temperatures were measured in the overlap area and compared with values obtained from undisturbed areas. It was found that the overlap area is grossly overcooled. Results were compared with a new configuration, where the twist angle was changed to 0°, and it was found that the overcooling was significantly reduced. Temperature measurement showed that the increased thickness of the scales in the overlap area can also be caused by surface overcooling because the scales change material properties with temperatures, and are therefore more difficult to remove. The new configuration with a twist angle of 0° seems to promise to improve the quality of hydraulic descaling.

Výroba a zpracování oceli je spojena s oxidací při vysokých teplotách. Nežádoucí okuje se tvoří na povrchu oceli, která se se obvykle zahřívá na více než 900 ° C. Tyto okuje jsou při výrobě odstraněny pomocí hydraulického odkujování. Ve většině případů se používají trysky uspořádané v řadě. Tento příspěvek se zabývá oblastí překryvu trysek, především zvýšeným přestupem tepla v těchto místech a příslušnými koeficienty přestupu tepla (HTC). Článek porovnává dvě konfigurace trysek a porovnává jejich intenzitu chlazení v oblasti překryvu.

The production and processing of high quality grades of steel is connected with oxidation at high temperatures. Unwanted scales are formed on the steel surface, which is usually heated over 900°C. These scales are often removed by hydraulic descaling during production. In most cases where long, flat products are produced, one row of descaling nozzles is used. Because these flat jet nozzles are arranged in the row, the water spray from one nozzle interferes with the spray from neighboring nozzles. This zone is called an overlap area and oftentimes more scales remain here after the descaling process. An increased amount of scales left behind result in a lower quality final product. The typical configuration with an inclination and twist angle equal to 15° was studied. Heat transfer coefficients (HTC) and surface temperatures were measured in the overlap area and compared with values obtained from undisturbed areas. It was found that the overlap area is grossly overcooled. Results were compared with a new configuration, where the twist angle was changed to 0°, and it was found that the overcooling was significantly reduced. Temperature measurement showed that the increased thickness of the scales in the overlap area can also be caused by surface overcooling because the scales change material properties with temperatures, and are therefore more difficult to remove. The new configuration with a twist angle of 0° seems to promise to improve the quality of hydraulic descaling.

scales, steel, water, hydraulic, descaling, overlapping, temperature, heat transfer coefficient, surface

2015

28.09.2015

Inštitut za kovinske materiale in tehnologije, Ljubljana, Lepi pot 11,

Ljubljana

978-961-92518-8-1

Book of abstracts

23

199–199

1