Hot Rolling Roller & Cold Rolling Roller

Steel ingots or billets are difficult to deform and process at room temperature. They are generally heated to 1100 to 1250°C for rolling. This rolling process is called hot rolling. The termination temperature of hot rolling is generally 800 to 900°C, and then it is generally cooled in air, so the hot rolling state is equivalent to normalizing treatment. Most steels are rolled by hot rolling.

The steel delivered in the hot-rolled state has a certain degree of corrosion resistance due to the high temperature, so it can be stored in the open air. However, this layer of oxide scale also makes the hot-rolled steel surface rough and the size fluctuates greatly. Therefore, it is required to use hot-rolled semi-finished products or finished products as raw materials and then cold-rolled production of steels with smooth surface, accurate size and good mechanical properties.

The roller is one of the most important parts of the rolling mill. The rolling parts are plastically deformed by the rotating rollers to roll out products that meet the required shape and dimensional accuracy. The other parts on the rolling mill are for installation, support, adjustment, and replacement The rollers and guide rollers are set to enter and exit the rollers correctly.

The roll consists of roll body, roll neck, and shaft head. The roll neck is installed in the bearing, and the rolling force is transmitted to the stand through the bearing seat and the pressing device. The shaft head is connected to the connecting shaft to transmit rolling torque. There are three main types of shaft heads: plum blossom shaft heads, universal shaft heads, keyed or cylindrical shaft heads.

There are many ways to classify rolls, mainly:
(1) According to product type, there are strip steel rolls, section steel rolls, wire rolls, etc .;
(2) According to the position of the roll in the rolling mill series, there are blanking rolls, rough rolling rolls, finishing rolls, etc .; (3) According to the roll functions, there are broken scale rolls, perforated rolls, and smoothing rolls;
(4) According to the roll material, there are steel roll, cast iron roll, tungsten carbide roll, ceramic roll, etc .;
(5) According to the manufacturing method, there are casting rolls, forging rolls, surfacing rolls, sleeve rolls, etc .; (6) According to the state of rolled steel, there are hot rolls and cold rolls.

Various classifications can be combined to make the rolls have a clearer meaning, such as centrifugally cast high-chromium cast ironwork rolls for hot-rolled strip.

1. The characteristics of the roll work are: the roll is in direct or indirect contact with the rolled piece during the rolling process, forcing the plastic deformation of the rolled piece, so it bears a large rolling pressure, rolling torque and dynamic load. Especially during hot rolling, due to the high temperature of the rolling stock and the cooling of the roll with cooling liquid, the working conditions are extremely harsh, so there are strict requirements on the strength, stiffness, toughness, surface hardness, wear-resistance and roll shape of the roll to ensure Rolling quality and output.

2. The roller can be divided into:
(1) Soft roller. Shore hardness is about 30-40, used in roughing machines for roughing machines and large section steel mills.

(2) Semi-hard roller. Shore hardness is about 40-60, used in roughing mills of large, medium and small steel rolling mills and steel plate rolling mills.

(3) Hard surface roller. Shore hardness is about 60-85, which is used for the roughing mill of thin plate, medium plate, medium section steel, and small section steel mill and the support roll of four-roll mill.

4) Extra hard roller. Shore hardness is about 85-100, used in cold rolling mills.

What are the advantages of cold rolled ribbed steel?

Cold rolled ribbed steel bars are rebar, Rebar is traditionally called and the standard scientific name is ribbed steel. It is divided into cold-rolled ribbed steel bars and hot-rolled ribbed steel bars. Usually hot rolled ribbed steel bar is called hot-rolled rebar or rebar.

Cold rolled ribbed steel bars have the following advantages:

1. The steel has high strength, which can save construction steel and reduce engineering costs. ll550 grade cold-rolled ribbed steel bar compared with a hot-rolled round steel bar, used in cast-in-place structures (especially in building roofs) can save 35% -40% of steel. If you consider not using hooks, the steel savings are even greater. According to the current market price of steel, each ton of cold-rolled ribbed steel bar can save steel costs about RMB800.

2. The bonding and anchoring performance between cold-rolled ribbed steel bar and concrete is good. Therefore, it is used in components, which fundamentally eliminates the phenomenon of cracking in the anchorage area of ​​the component and the destruction of the steel wire slippage, and improves the bearing capacity and crack resistance of the end of the component; Reinforcement is even smaller than hot-rolled rebar.

3. The elongation of the cold-rolled ribbed steel bar is larger than that of similar cold-worked steel.

Why are there are ribs on the reinforcing steel bar?

Steel bar is easy to see in daily life, if you carefully observed the difference between them? Is there anything special about the design of these steel bars?

Of course there is! In fact, there is a kind of reinforced bar with striation called “deformed steel bar”, also known as “ribbed steel bar” “deformed steel bar”, also known as “ribbed steel bar”, the corresponding is the “smooth round steel bar” without striation.
This kind of pattern is called “transverse rib”. The shape of transverse rib is spiral, herringbone and crescent 3 kinds.

Cold rolling ribbed bars are bars with three or two horizontal ribbed bars evenly distributed along the length direction on the surface of hot-rolled disc bars after cold-rolled. The transverse rib on the steel bar is used to enhance the bonding performance between the steel bar and concrete, and to transfer the stress better. Simply put, it enables the steel bar and concrete to work better in coordination and bear external forces together.

Rolled ribbed steel bar is commonly used in low carbon steel, which has good strength and toughness, and is widely used because of its high bond strength with coagulant. In general, cold-rolled ribbed bar is used in prestressed hollow slab, which can solve and improve some quality problems effectively.

Cold rolling is the steel bar whose section is changed according to certain rules, which can improve its strength and adhesion with concrete. When the steel bar is rolling by ribbing rollers and roller holders, it deforms both longitudinally and transversally, so its plasticity and internal structure uniformity can be well maintained. It has obvious economic benefit to strengthen the steel bar by cold working in construction engineering.

After cold rolling, the yield point of reinforcement can be increased by 20% ~ 25%. The yield point of cold-drawn steel wire can be increased by 40% ~ 60%. Thus, the design section of reinforced concrete structure can be reduced appropriately, or the number of reinforcement in concrete can be reduced, so as to achieve the purpose of saving steel.

Cold rolling of reinforcement also facilitates the simplification of construction procedures. Cold-drawn steel rod can dispense with opening and straightening procedures; Cold drawing bar can be completed together with straightening, rust removal and other processes.

Tungsten carbide roller are called TC roll / T.C. roller and are usually made in set of 3 rolls for rolling low carbon, medium carbon, high carbon smooth round steel bar and also the rollers for cold rolling ribbed bars.

The rolls of size 125x82x15mm, 140x90x15mm, 150x90x15mm etc are the common sizes. The wire diameter of cold rolling ribbed bars is usually 3mm to 14mm. The rolled steel bars are widely used in houses, roads, bridges, tunnels and other infrastructure.

What Does the Superscript R Mean for the Cold-Tie Ribbed Steel Symbol?

Example CRB550—R here stands for ribbed steel bar, cool—cold, balls—rebar,
In the upper right corner of the symbol Φ:
S stands for steel strand
P stands for stress-relieved light round steel wire
H stands for stress relief spiral rib steel wire
I stands for stress relief wire
HT stands for heat-treated steel
R stands for cold rolled ribbed. It’s just a recognized symbol. The RRB400 symbol also has an R in the upper right corner, but the previous symbol is different. Like several symbols of hot rolled ribs, there is no meaning of words, only differences.

The working conditions of the rolls in the rolling mill components are relatively complicated, and they are mainly affected by dynamic and static loads, wear and temperature changes during rolling. Residual stress and thermal stress are generated in the preparation process of hot rolls before manufacturing and use. In use, it is further subjected to various periodic stresses, including bending, torsion, shear, contact stress and thermal stress. The distribution of these stresses along the roll body is uneven and constantly changing. The reasons are not only design factors, but also the continuous changes of roll wear, temperature and roll shape during use. In addition, the rolling conditions are often abnormal. Improper cooling of the roll after use will also be damaged by thermal stress. Therefore, in addition to abrasion of the roll, various local damages and surface damages such as cracks, fractures, peeling, and indentations often occur.

Therefore, how to solve the wear problem, we must first understand the reason. During hot rolling, the temperature of the hot roll contacting the material itself can reach 1200°C. At the same time, the plastic deformation heat of the rolling piece and the contact surface of the roll and the rolling piece make the temperature of the roll rise, and the bearing The lubrication performance decreases linearly at high temperatures, and it can also cause defects in the size, shape, material and mechanical properties of the roll. Although a large amount of coolant is sprayed on the rolls to cool during the rolling process, the rolling process is in the cycle of periodic heating and cooling curve changes. The roll surface, roll bearing position and various configurations of the rolling mill are all due to periodic heating. The impact of contact stress, performance yields, and therefore wear.

Secondly, the rolling piece and the roll are in instantaneous contact, and the relative speed formed by the sliding speed inertia is large, and the bearing position of the roll is completely different from the bearing capacity when the bearing is working at the three positions of the roll entrance, neutral point and exit. At the same time, the friction force during the traveling process of the rolling piece has obvious negative damping characteristics, which leads to the generation of self-excited vibration of the roll. It is the shaft and the bearing that produce fretting wear under such small amplitude relative vibration, which will increase with the number of rolling. And time delays and intensifies.

In addition, rolling mills now generally use emulsion as a process lubricant. Under the chemical action of the emulsion, the wear process of the metal material of the roll is intensified, especially the permeable corrosion of the metal under the action of high temperature.

How to choose a process to deal with the wear of the roll shaft:

Many hot-rolling roll shaft wear repair processes still use power transfer technology, which may be repaired, but the steps are complicated and not conducive to the subsequent use of the equipment itself, and damage will still occur during production.

Therefore, Sole Carbon Nano polymer materials just make up for this shortcoming, such as the commonly used machining repair technology:

• Surface baking oil: Use oxygen acetylene to bake the oil on the bearing surface until there are no sparks and the surface is dry;
• Place the shaft on the machine tool and fix it. While keeping the speed low, roughen the surface of the bearing position. The rougher the surface, the better. If necessary, thread the surface of the bearing position;
• Calculate the amount of material according to the amount of unilateral wear of the bearing position, and adjust the Sole carbon nano-polymer repair material according to the proportion, and the harmony is uniform, without color difference, and the adjusted material is first applied to the surface of the bearing position thinly;
• Material solidification: Adjust the machine speed to the lowest to ensure that the shaft solidifies in the rotating state. When curing the material, it is recommended to use an iodine tungsten lamp to heat, the heating temperature should be abou