INTRODUCTION
Hearth roller is a typical centrifugal casting pipe fittings. It is one of the important components in support of metallurgical equipment and transport slabs. As a result it has wide application in Continuous casting- rolling production line. In the rolling process first of all to heat the steel slab to 1050 ~ 1150 ℃ rolling temperature in the furnace continuously and stably. Furthermore stable support of the slab through the hearth roller to ensure a smooth and uniform delivery. Since intermediate section of the Hearth roller mounted on the billet calcining furnace directly the furnace temperature is about 1150 ℃ during the process of production.
Hearth roller usually was manufactured with ZG45Cr28Ni48W5Si2 and other high-temperature alloys. Meanwhile since the intermediate section of the hearth roller mounted in furnace directl the tapered section. Similarly the bearing support section are mounted inside the calcining furnace and outside the furnace respectively. The temperature gradient of hearth rolls is very large at different parts. Consequently the hearth roller welded together by the sleeve and cone and shaft generally. In order to reduce the burning of the inner surface of the cone the inside of the cone have insulation board. Which ensure the smooth delivery of high-temperature slab.
Requirements: hearth roller shaft not deformed. And external roller ring heat-resistant, wear-resistant. Research shows that the hearth roller is use of large in the metallurgical industry. almost it has high manufacturing costs. Similarly has a long-term high temperature overload working conditions. Consequently prone to failure damage.
Several major forms of roller hearth failure:
1． Weld fracture.
2． Shaft neck fracture.
3． Connect the fracture.
The main reason include:
- 1. Welding performance of high temperature nickel-base alloy is poor. Prone to weld cracking and other defects.
- 2. Welds to withstand pull – push alternating stress loads. Prone to fatigue fracture.
- 3. Weld is cold-hot junctional zone, exists of large temperature gradient cause thermal stress, thermal stress will accelerate fracture.
- Above all there are much attempts to improve hearth roll on material and welding workmanship. However the life of a hearth roller has not achieved significant results. Therefore to improve the performance of hearth roll
- and improve its life by structural optimization is very important. Consequently it may improve the quality of the product. It is a effective way to enhance the competitiveness of products.
