File Name: cold rolling defects and remedies .zip
After reading this article we will learn about:- 1. Meaning of Rolling 2.
- Cold rolling defects and remedies pdf
- Plate Rolling Defects and How to Avoid Them
- Rolling of Metals: Process and Principles (With Diagram)
- Plate Rolling Defects and How to Avoid Them
Cold rolling defects and remedies pdf
After reading this article we will learn about:- 1. Meaning of Rolling 2. Process of Rolling 3. Principles 4. Load and Power Requirement 5. Lubrication 6. The process of shaping metals into semi-finished or finished forms by passing between rollers is called rolling. Rolling is the most widely used metal forming process.
It is employed to convert metal ingots to simple stock members like blooms, billets, slabs, sheets, plates, strips etc.
In rolling, the metal is plastically deformed by passing it between rollers rotating in opposite direction. The main objective of rolling is to decrease the thickness of the metal. Ordinarily, there is negligible increase in width, so that the decrease in thickness results in an increase in length.
Rolling is done both hot and cold. It is accomplishes in rolling mills. A rolling mill is a complex machine having two or more working rollers, supporting rollers, roll stands, drive motor, reducing gear, flywheel, coupling gear etc. Rollers may be plain or grooved depends upon the shape of rolled product. The metal changes its shape gradually during the period in which it is in contact with the two rollers.
The range of products that can be produced by rolling is very large. Rolling is a more economical method of deformation than forging when metal is required in long lengths of uniform cross-section. It is one of the most widely used among all the metal working processes, because of its higher productivity and lower cost. The materials commonly rolled are steel, copper, magnesium, aluminum and their alloys.
Primary rolling is used to convert metal ingot to simple stock members like blooms and slabs. This process refines the structure of casted ingot, improves its mechanical properties, and eliminates the hidden internal defects. Blooms and slabs obtained from primary rolling, again converted into plates, sheets, rods and structural shapes, by hot rolling process. Cold rolling is usually a finishing process in which products made by hot rolling are given a final shape.
These processes provide good surface finish, closer dimensional tolerances and enhance mechanical strength of the material. The steel which we get from re-melting shop or from steel manufacturing plants is mostly in the form of ingots. Ingots have a roughly square cross section of 1. The blooms are rolled to billets and the billets to the desired sections like flat, square, hexagonal, angle, I,U, etc. The above mentioned member has following sizes approximately.
The rolling is a process which consists of passing the metal through a gap between rollers rotating in opposite direction. This gap is smaller than the thickness of the part being worked.
Therefore, the rollers compress the metal while simultaneously shifting it forward because of the friction at the roller-metal interfaces. When the work piece completely passes through the gap between the rollers, it is considered fully worked. As a result, the thickness of the work is decreases while its length and width increases. However, the increase in width is insignificant and is usually neglected. The Fig. The decrease in thickness is called draft, whereas the increase in length is termed as absolute elongation.
The increase in width is known as absolute spread. Two other terms are the relative draft and the coefficient of elongation can be given as follows:. The above equation 3 shows that coefficient of elongation is adversely proportional to the ratio of final to original cross-sectional areas of the work.
Also, equation 2 shows that coefficient of elongation is proportional to the ratio of final lo original lengths of the work. The metal is deformed in the shaded area, known as deformation zone. The metal does not undergo any deformation before and after deformation zone. It can also be seen that the metal undergoing deformation is in contact with each of the roller along the arc AB. The arc-AB is called the arc of contact. From the geometry of the drawing and by applying simple trigonometry, the angle of bite can be given as:.
The above equation 4 gives the relationship between the geometry parameters of the rolling process, the angle of bite, the draft, and the radius of rollers. The deformation zone, state of stress and angle of contact in rolling is shown in Fig. The main stress system produced in the deformation zone is tri-axial compression. The maximum or principal stress is acting normal to the direction of rolling.
The deformed metal is exerting an equal and opposite force on each of the rolls to satisfy the equilibrium conditions. Therefore, this force normal to the direction of rolling is important factor considered for designing of the rolls and mill body. This force F is also important in determining the power consumption in a rolling process. Unfortunately, the exact determination of the rolling load and power consumption is a typical task and requires a well knowledge of theory of plasticity and calculus.
Nevertheless, a first approximation of the rolling load can be given by the following equation:. This equation 2 neglects the friction at the roller-work interface, and therefore gives lower estimation of the rolling load. Based on the experiments, a multiplication factor of 1. Also, the power consumption in rolling process cannot be obtained easily; however, a rough estimation, in low friction consideration is given by:. Lubrication is used in rolling process to reduce the friction between rolls and metal to be rolled.
Friction plays a very important and useful roll in rolling process. In fact, it is responsible for shifting the work forward between the rolls and should not, therefore, be eliminate or reduced below an appropriate level.
This is an important consideration while choosing a lubricant for a rolling process. In cold-rolling of steel, fluid lubricants having low viscosity are used, paraffin is suitable for non-ferrous materials like aluminum, copper and its alloys to avoid staining during subsequent heat treatment process, while, hot rolling is often carried out without lubricants but with a flood of water to generate steam and break up the scales formed, are used. Sometimes an emulsion of graphited grease is employed as a lubricant.
A number of defects in the rolled products arise during rolling process. A particular defect is usually arrived with a particular process and does not arise in other processes.
Edge cracking generally occurs in rolled ingots, slabs, or plates. This is due to, either limited ductility of the work metal or uneven deformation, especially at the edges. Folds are a defect generally occurs in plate rolling. This is caused if the reduction per pass is too small. Alligatoring is the defect, usually occurs in the rolling of slabs particularly aluminum and alloys.
In this defect, the work piece splits along a horizontal plane on exit, with the top and bottom. This defect always occurs when the ratio of slab thickness to the length of contact fall within the range of 1. Shows the defect of Alligatoring. Metallurgy , Metals , Rolling , Rolling of Metals. Machine Forging: Process and Advantages Forging. Main Elements of a Die-Set Metallurgy.
Plate Rolling Defects and How to Avoid Them
The Elastic deformation of mill takes place on the metal. The roll part consists of middle position bend or deflection due to compressive load on work rolls resulting more thicker than end of work piece. The thicker of center implies the edges are plastically elongated than center. This reason to induce the residual stress of compression at the edge of part and tension along with the center line of work piece. The uneven distribution of stress in the work piece to provide center line cracking zipper cracks warping or wavy edge of final work metal sheet. In the case the roll or cover- cambered together the work piece edge thicker than center and residual stress is provided opposite to the insufficient cambering.
Quality in business, engineering and manufacturing has a interpretation as the non-inferiority or superiority of something. Quality is a perceptual, conditional and somewhat subjective attribute and may be understood differently by different people. Definition of Quality! Quality is a perceptual, conditional and somewhat subjective attribute. Types of Customer 1. Internal Customer Next User 1. FINS Fins are narrow beads running longitudinally.
Rolling- process, variables, geometry and load calculations, hot and cold rolling, rolling defects andremedies. Pdf 9 Library of Manufacturing Metal Rolling.
Rolling of Metals: Process and Principles (With Diagram)
When sheet metal is formed, it may be used by many different tools or sent through different machines. Sheet metal is cut, rolled, and manipulated into different shapes and objects that form a wide variety of purposes. In fact, a large majority of the products that we use every day were constructed from sheet metal.
Plate Rolling Defects and How to Avoid Them
Quality in business, engineering and manufacturing has a interpretation as the non-inferiority or superiority of something. Quality is a perceptual, conditional and somewhat subjective attribute and may be understood differently by different people. Definition of Quality! Quality is a perceptual, conditional and somewhat subjective attribute. Types of Customer 1.
Embed Size px x x x x These shapes are further processed through hot rolling, forging or extrusion, to. In rolling the crystals get elongated in the rolling direction. Defectsin metal forming processes and their remedies. Use Kalpakjians book. Forces and geometry relationships in rolling.
Embed Size px x x x x These shapes are further processed through hot rolling, forging or extrusion, to. In rolling the crystals get elongated in the rolling direction. Defectsin metal forming processes and their remedies. Use Kalpakjians book. Forces and geometry relationships in rolling. Simplified analysis of rolling load: Rolling variables.
Root Cause of Mill Defects & Its Remedies - Free download as Text File is the decrease of the carbon content of (the surface of) a steel due to.
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