Thermal-fatigue resistant work rolls for hot rolling mills

Abstract

Cyclic temperature changes in the working layer of a roll during hot rolling cause thermal stress which leads to damage on the surface layer of the roll due to thermal fatigue. The pre-conditions of crack initiation are described. The intensity of crack propagation could be influenced by optimizing the chemical composition and physical-mechanical properties of the material on the working layer. This reduces the tendency of the material with respect to damage due to thermal fatigue and extends the lifetime of the rolls. The microstructure as well as the operational characteristics of the developed HSS working rolls resistant to thermal fatigue are presented.

Ceramic rolls for rolling of steel foils

“…The suitability of these materials was examined by upsetting cylinder samples made of steel, pure aluminium, copper, tungsten, molybdenum and Cu-Sn and Cu-Ag alloys with ceramic upsetting tracks (Ø50 x 30) made from the above-mentioned ceramic materials. The effect of the quality of the compression track, such as silicon nitride raw material quality (standard or high quality), manufacturing process (low-pressure sintering, gas-pressure sintering, hot isostatic pressing), surface condition (ground or polished surface), effect of the compression force used, compression tests with the above-mentioned metals and alloys are presented by us in [18][19][20][21][22][23][24].…”

“…15b). The results obtained [16,[18][19][20][21][22][23][24] were used as a basis for further optimization of the rolling process in 20-roll stands [28][29][30][31][32][33][34].…”

Modern materials for cast rolls of hot strip mills

“…The vanadium-based MC carbides dissolve only partially (Fig. 4), as they have a higher dissolution temperature in austenite than the hardening temperature [25].…”

“…Compared to chrome rolls and Indefinite Chill Double Pour rolls (ICDP) (see below), HSS rolls show a 2 to 5 times longer service life. The higher performance of HSS rolls are associated with the special features of the microstructure, which has a hardness of 78-84 ShC and a tensile strength of around 900 N/mm² [25]. This is achieved through the presence of fine special carbides (primary and secondary carbides), which have a significantly higher hardness than M 7 C 3 carbide, and the higher hardness of the strengthened matrix of tempered martensite.…”

“…Partially dissolved MC carbides (SEM): a -overview image (3000:1), b -detail (6000:1) and EDX mapping to determine the element distribution (c -h) [25]Slika 4. Delimično rastvoreni MC karbidi (SEM): a -pregledna slika (3000:1), b -detalj (6000:1) i EDX mapiranje za određivanje raspodele elemenata (c -h)[25]…”