A Brief Discussion on Protective Treatments for Rolling Mill Equipment

Release date:

2023-02-16

In practical applications, the rolls of rolling mill equipment may develop cracks. Analysis of these cracking phenomena reveals that the primary locations of crack initiation are typically concentrated at the roll necks, with fracture surfaces exhibiting irregular inclined or perpendicular orientations. So, what causes this phenomenon?

To analyze this issue, we can consider several factors. First and foremost, the problem may stem from quality defects in the rolls themselves. Since the work rolls are in direct contact with high‑temperature slabs and subjected to various loads, they must exhibit excellent heat resistance. If the hardness of the roll body decreases significantly as the roll temperature rises, it indicates poor heat resistance, which can severely compromise the roll’s overall performance.

When analyzing rolling conditions as a whole, the roll itself must also exhibit excellent wear resistance, along with appropriate hardness and strength. In fact, surface‑layer mechanical fatigue caused by cyclic loading, as well as thermal fatigue resulting from the roll’s surface being subjected to periodic heating by the workpiece and periodic cooling by quenching water, can both lead to roll wear and the formation of thermal cracks.

The hardness specification of the roll is also very important; under normal conditions, its hardness is inversely related to the roll body’s resistance to thermal cracking. In other words, the higher the roll‑body hardness, the better the wear resistance, but the weaker its resistance to thermal cracking. Generally, the wear resistance and surface hardness of a roll are influenced by the hardness gradient along the roll’s diameter; therefore, it is desirable to minimize this gradient while maintaining an appropriate level of hardness.

In actual rolling operations, rolls are subjected to numerous types of loads. According to specialized mill manufacturers, during the rolling process, rolls experience the rolling pressure applied at both ends by hydraulic systems, as well as the reaction forces generated by the deformation of the workpiece; they also endure cyclic thermal and mechanical loads arising from alternating heating and cooling conditions.

The Relationship Between Rolling Mill Efficiency and Ambient Humidity and Temperature

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A brief introduction to rolling mills

Rolling mill manufacturers generally consider that, by “equipment,” they mean devices capable of carrying out the metal‑rolling process—essentially, the complete set of machinery required to produce rolled products. This includes primary equipment, auxiliary equipment, lifting and conveying systems, and ancillary devices. However, in actual production practice, the term often refers solely to the primary equipment.

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The Relationship Between Rolling Mill Efficiency and Ambient Humidity and Temperature

Regarding the selection of heating furnaces, appropriate relative temperature values vary. For instance, in a walking-beam furnace, where billets remain in the furnace for a relatively short time, a rolling‑type furnace requires greater driving force to achieve a higher heating rate. Typically, the partial pressure of water vapor at the gas outlet must be kept below half of the external material’s water‑vapor pressure. If a regenerative furnace is used, the water‑vapor fraction in the exhaust gas is generally about 60% of the billet’s surface water‑vapor pressure. For certain types of reheating furnaces, it is essential to maintain the required air velocity; therefore, when designing the furnace structure, both relative humidity and contact conditions should be carefully considered. To meet high air‑velocity requirements, a larger air flow can be employed to reduce relative humidity, thereby increasing the billet’s heating rate and minimizing heat loss.

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How can a short-stress rolling mill prevent bearing burnout?

How can bearing burnout in short‑stress rolling mills be prevented? Here, we focus solely on seal failure. When a seal fails, the most serious consequence is leakage of the bearing lubricant, allowing contaminants to enter the bearing and accelerating wear, ultimately leading to bearing burnout. So what are the root causes of seal failure? First and foremost is seal selection. Because rolling mills are frequently disassembled and reassembled, it is essential to use seals equipped with secondary lips, ensuring they are installed in the correct orientation to provide effective containment of lubricating oil or grease.

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A technology-driven enterprise specializing in the design, manufacture, processing, and sales of Morgan high‑carbon wire, Morgan copper wire rolling mills, and related equipment and spare parts.

Nanjing Yunzheng Industrial Equipment Co., Ltd.

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Factory Address: Building C1-1, Zhongnan Zhiyu Industrial Park, No. 5 Xiaoqi Road, Xiongzhou Subdistrict, Liuhe District, Nanjing City, Jiangsu Province

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