The Usage And Types Of Straightener

The Usage And Types Of Straightener

The Usage of the Straightener

During the heating, rolling, finishing, and transportation process of the rolling piece, the external force, temperature changes, internal force changes, or some other factors, very easily lead to curve, deform, and some other variations, for solving these problems, we need to use a straightener to eliminate the stress from both inside or outside, then we can get straight final steel, the straightener is essential equipment in a rolling mill workshop, and is widely used for other workshops like cars and ships.

The Types of the Straightener

According to the requirement of the final product specification requirement, the straightener style would be the difference, divided by working theory, and application purpose can be divided as the following:

Press straightener

Parallel straightener

Cross rolls straightener

Stretch straightener

Bending straightener

Reverse straightener

Except for the above straightener, there are still a lot of special straighteners, basically, with the development of technology, the straightener will be promoted very quickly, for different requirements of the application.

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The Usage Of Water In Rolling Mill Machines

The Usage Of Water In Rolling Mill Machines

With the development of the steel industry, more attention is paid to the protection of mechanical machines, such as roughing machines, reversible rolling mills, pre-finishing rolling mills, finishing rolling mills, and wire-rod mills. Therefore, most of the water used in the iron and steel industry is used for cooling, protecting equipment, and improving the working conditions of the employees. The Health and safety of the employee require dust control, which is commonly accomplished by sprinkling water on floors and machines.

Water use in all types of hot rolling mills is mainly for scale removal and temperature control. When steel is heated to the high temperature desired for hot rolling, its surface is oxidized and a hard scale is formed. If not removed before rolling, this scale would be rolled into the steel and would cause surface defects.  A common method of scale removal is to spray water under a pressure of as much as 2,000 psi (pounds per square inch) against the steel immediately before it enters the rolls.

Cooling water is sprayed on the rolls during hot rolling to prevent distortion and reduce erosion of the roll surfaces. Because considerable heat is produced by the rolling processes, water also serves to keep the steel at its proper rolling processes. Upon emergence from rolling mills, steel may be sprayed with water to hasten cooling. This spray prevents excessive scale formation. Roll bearings also require cooling. Spent cooling water flows to the scale pit along with that used for scale removal and may be reused after clarification and cooling.

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The Use And Maintenance Of Roller

The Use And Maintenance Of Roller

The roller is the biggest wearing part, expensive so for reducing the cost, we should carefully maintain it.

1. Full quality test before entering the workshop

The roller is a high technology, high value-added product, should apply quality tests according to the quality standard, test the roller surface, and end’s hardness, the hardness deviation should be below ±（2-3）HS, apply ultrasonic to test the inside flaws, surface wave for testing surface quality, visual inspection for outside flaws.

2. Regular refacing

We should change the roller regularly for better protection even if the surface is flawless, roller working hours should be 50-100H, and the supportive roller should reface after 2000-3000h, for removing the working layer, the remover layer should be thicker than the working layer.

3. Use the roller in the right way.

Use the roller according to the guidance, should adjust the temperature to 70-80℃ when switching rollers, the cold roller should be at 30-50℃, should cold down in the water, and the roller neck should be lubricated, keep clean, avoid rusting and grinding damage iron sheet, prevent misoperation and accident.

4. Avoid roller break accident

Breaking down of  roller is a destructive accident, there are normally two reasons, one is because of the quality of the roller, normally we can find flows in the breaking point, the other reason is from the outside and causes the roller's power and torque is overweight, we should avoid this circumstance.

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The Characteristics Of Horizontal Rolling Mill And Tandem Rolling Mill

The Characteristics Of Horizontal Rolling Mill And Tandem Rolling Mill

The horizontal rolling mill is mainly used for the production of various sections of steel, narrow hot strips, and small billets. The following are the main features of the horizontal rolling mill :

(1) A row of rolling mills is driven by a motor. The rolling speed of each rolling mill is the same, and the rolling speed cannot be increased as the length of the rolling stock increases, so the output is low and the labor productivity is low;

(2) The structure of the rolling mill is generally three-roller or two-roller alternate;

(3) The rolling mill operation mode is mostly shuttle rolling or loop rolling. With flexible deformation and strong adaptability, each rolling mill can roll several times. The product range is wide and the operation is relatively easy;

(4) The rolling mill equipment is simple, with less investment and quick construction.

The tandem rolling mills are arranged in a row according to the rolling direction of the rolling stock. The rolling stock is only rolled once on each rolling mill. Each rolling mill is driven separately. Each rolling mill has different rolling speeds, that is, the rolling speed of the rolling rolls can be related to the rolling stock. The reduction in the section or the increase in the length of the rolled piece increases. Therefore, compared with the horizontal rolling mill, the rolling mill has the advantages of short gap time, high production efficiency, and less auxiliary equipment.

However, when this kind of rolling mill works, the rolling stock sequentially enters each rolling mill without forming a continuous rolling relationship, and the rolling stock is lengthened as the number of rolling passes increases, and the distance between the racks increases as the length of the rolling stock increases, so Longitudinal mills occupy a longer plant. This type of rolling mill is only suitable for large and medium-sized steel production. In order to overcome this shortcoming, the tandem mill was further developed into an off-road and a chess mill.

In cross-country rolling mills and staggered rolling mills, the head and tail of the rolling stock are alternated in different passes, which means the upper head becomes the tail of the track, and the tail of this track becomes the next head again. The rolling stock has lateral movement during the rolling process. The arrangement of the cross-country rolling mills and staggered rolling mills is more concentrated, which overcomes the shortcomings of the long mill. These mills also have a fast rolling speed and are suitable for the production of large, medium, and small complex sections of steel such as I-beam, channel steel, and H-beam.

The Work Theory Of Film Bearing

The Work Theory Of Film Bearing

Film bearing is a radial running bearing that uses lubricant as a media, the basic working theory is, during the rolling process, the bearing journal moves because of the rolling power, and the bearing center and the bearing journal have skewing, making two zones in the gap of film bearing and journal, one is called amplification area, the gap is getting bigger and bigger according to the rotating direction, one is called constriction area, the gap is getting smaller according to the rotating direction. When the rotating journal brings the lubricant from the amplification area to the constriction area, the gap becomes smaller and smaller, forming a lubricant wedge, creating pressure on the lubricant oil pressure, the pressure from every point in the film altogether is bearing capacity of film bearing, when the rolling power is bigger than the bearing capacity, the journal center and the bearing center eccentric distance enlarges, in the constriction area, the gap between bearings changing fast in the direction of journal rotating, the thickness of film get to the thinnest, the pressure of film getting bigger, carry capacity getting bigger, until balance the rolling power of the journal will not deviation, the bearing and journal completely separated by the film, become all liquid lubricant in theory.

From the film bearing theory, we can sense that the most important specification is film thickness, if the thickness is too thin, and the impurity in the lubricant is too big, which is just like metal touching directly, can lead to burning inside, meanwhile, if the thickness of the film is too thin, if steel pushing accident happens, it is very easy to course direct contact which leads to burning, the smallest thickness of the film is related to bearing structure material, related parts’ accuracy, and film bearing system assemble accuracy, lubricant, and rolling power.

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Types Of Furnaces---Induction Furnace (Two)

Types Of Furnaces---Induction Furnace (Two)

Induction Furnace:

Induction heating of metal will provide the heat required for the electrical furnace. An induction furnace will provide a clean, energy-efficient, and well-controlled process of melting when it is compared with other processes. Most of modern foundries use this type of furnace instead of cupolas to melt cast iron as the former emits lots of duct along with other pollutants. 

The capacity ranges from less than one kilogram to a hundred tonnes capacity is used in melting iron, steel, copper, aluminum, and other precious metals. As the process does not use combustion, the material temperature is not higher than the required to melt it. This process prevents the loss of valuable alloying elements. The induction furnace lacks the refining capacity where the charge materials clean the oxidation products and the known composition. The alloying elements may have a chance to lose alloying elements due to oxidation.

The frequency of operation is high and is dependent on the material that is to be melted, and the furnace capacity required. If the volume of the melts is small then it requires a higher frequency. A pre-heated furnace of the melting iron can melt the cold charge by tapping of the readiness within an hour. The power supply range is from 10 KW to 42 KW which melts in size ranges of 20 kg to 65 tonnes of the respective metals. The operating induction furnace can be used by the operators to identify the correct operation and its corresponding power level.

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Types Of Furnaces --- Open Hearth Furnace（Three）

Types Of Furnaces --- Open Hearth Furnace（Three）

Open Hearth Furnace:

The open heart process is also called a Siemens-martin process i.e. steel making technique for most of the applications in the 20th century. This process seeks a means to increase the temperature in a metallurgical furnace that uses the waste heat given out from the furnace that directs the fumes from the furnace through a brick checker work. A brick is heated to a high temperature, and then it is introduced into the furnace. The device is first used to produce steel that is charged with pig iron and wrought iron along with their scrap. The US and Britain are best suited to the open hearth process.

Natural gas or atomized heavy oils are used as fuel. The air and fuel are heated before combustion. The furnace gets charged with blast furnace iron in liquid form, steel crap that is combined with ore, limestone, dolomite, and fluxes. The roofs and body of the furnace are made of highly refractory materials such as magnetic bricks. 600 tons is the capacity of the open hearth furnaces that are installed in groups for massive auxiliary equipment, that is needed to charge up the furnaces and to handle the liquid steel that can be employed efficiently. It is most commonly used in industrial applications such as electric arc furnaces and oxygen process-based furnaces.

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