Continuously plastically deformed main working parts and tools on the rolling mill. The roller consists of a roller body, a roll neck and a shaft head. The roll body is the middle part of the roll that actually participates in rolling the metal. It has a smooth cylindrical or grooved surface. The roll neck is mounted in the bearing and the rolling force is transmitted to the frame via the bearing housing and the pressing device. The shaft end of the transmission end is connected with the gear seat through the connecting shaft, and transmits the rotational torque of the motor to the roller. The rolls can be arranged in two, three, four or more rolls in the roll stand.

1. A brief history of the development of the roller

The variety and manufacturing process of rolls have continued to evolve with the advancement of metallurgical technology and the evolution of rolling equipment. The use of low-strength gray cast iron rolls in the rolling of soft non-ferrous metals in the Middle Ages. In the middle of the 18th century, the United Kingdom mastered the production technology of chilled cast iron rolls for rolling steel plates. In the second half of the 19th century, advances in European steelmaking technology required the rolling of larger tonnage steel ingots, whether the strength of gray cast iron or chilled cast iron rolls could not meet the requirements. Carbon steel is 0.4% to 0.6% of ordinary cast steel rolls. The appearance of heavy-duty forging equipment has further enhanced the toughness of forged rolls of this composition. The introduction of alloying elements and the introduction of heat treatment in the early 20th century have significantly improved the wear resistance and toughness of cast and forged hot and cold rolls. The addition of molybdenum to the cast iron rolls used for hot-rolled strips improves the surface quality of the rolled strips.
The rinsing compound casting significantly increases the core strength of the casting roll.The heavy use of alloying elements in rolls is after World War II. This is a higher requirement for roll performance after rolling equipment has grown in size, continuousness, high speed, automated development, increased rolling material strength and increased deformation resistance. the result of. During this period, semi-steel rolls and ductile iron rolls appeared. After the 1960s, powder tungsten carbide rolls were successfully developed. Centrifugal casting technology and differential temperature heat treatment technology for rolling rolls widely promoted in Japan and Europe in the early 1970s have significantly improved the overall performance of strip rolls. Composite high chromium cast iron rolls have also been successfully used on hot strip mills. In the same period, forged white iron and semi-steel rolls were used in Japan. In the 1980s, Europe introduced cold-rolled rolls with high-chromium steel rolls and ultra-deep-hardened layers, and special alloy cast iron rolls for the finishing of small-sized steels and wire rods. The development of modern steel rolling technology has led to the development of higher performance rolls. The cores produced by the centrifugal casting method and new composite methods such as continuous casting compound method (CPC method), spray deposition method (Osprey method), electroslag welding method, and hot isostatic pressing method are strong toughness forged steel or ductile ink Cast iron, composite high-speed steel rollers and metal ceramic rollers have been applied on new generation profiles, wire rods and strip mills in Europe and Japan respectively.

2. Roll classification

There are various methods for classifying rolls, which are: (1) There are steel strip rolls, profile steel rolls, wire rolls, etc., according to the type of product; (2) There are roll blanks, rough rolls, and the like according to the position of the rolls in the rolling mill series. Finishing rolls, etc.; (3) According to the roll function, there are broken scale rolls, perforated rolls, leveling rolls, etc.; (4) Roll rolls are divided into steel rolls, cast iron rolls, hard alloy rolls, ceramic rolls, etc.; (5) Press Manufacturing methods include casting rolls, forging rolls, surfacing rolls, nested rolls, etc.; (6) Hot rolled rolls and cold rolled rolls are divided according to the state of rolled steel. Various classifications can be combined to give the roller a more definite meaning, such as centrifugal cast high chromium cast iron work rolls for hot strip.

3. Roller selection

The commonly used roll materials and uses are shown in the table. Roll performance and quality generally depend on its chemical composition and manufacturing method and can be evaluated by its organization, physical and mechanical properties, and the type of residual stresses present inside the roll (see Roll Inspection). The effect of the roll in the rolling mill depends not only on the material of the roll and its metallurgical quality, but also on the conditions of use, roll design, and operation and maintenance. There are great differences in the operating conditions of the rolls of different types of rolling mills.
The factors causing the differences are:
(1) Mill conditions. Such as the mill type, mill and roll design, hole design, water cooling conditions and bearing types, etc.;
(2) rolling conditions such as rolling stock varieties, specifications and deformation resistance, pressing system and temperature system, production requirements and operations, etc.;
(3) Requirements for product quality and surface quality.
Therefore, different types of rolling mills and rolling mills of the same type and using different conditions have different requirements for the performance of the used rolls. For example, billets and slab bloomer rolls must have good torsional and bending strength, toughness, and bite in, Hot crack resistance and thermal shock resistance and abrasion resistance; and tropical finishing stands require high hardness, resistance to indentation, wear resistance, spalling, and thermal cracking resistance on the roll surface.
Understanding the conditions of use of the rollers and the failure modes of the rollers used in the same type of mill, and understanding the current performance and manufacturing processes of the various roller materials, can correctly formulate the technical conditions of the roller for the mill and select a suitable and economical roller material.
The most commonly used methods to evaluate the roll performance in the rolling mill are:
(1) Roll weight (kg) consumed for rolling 1T rolling stock (referred to as roll consumption), expressed in kg/t;
(2) Diameter reduction per unit roll diameter The weight of the rolled material is expressed int/mm.
With the modernization of rolling mills, the in-depth study of failures in the use of rolls, and improvements in the material and manufacturing process of rolls, the average roll consumption of industrially-developed countries has been reduced to less than 1 kg/t.

Leave a Reply

Your email address will not be published. Required fields are marked *