Some Basics of Rolling and Rolling Mills...

Some Basics of Rolling and Rolling Mills Rolling is the process of plastically deforming metal by passing it between rolls. It is the most widely used forming process, which provides high production and close control of final product. During rolling metal is subjected to high compressive stresses as a result of the friction between the roll and the metal surface. Leonardo da Vinci invented the first rolling mills but only after a few centuries rolling mills became important for the steel industry. Modern rolling practice is attributed to Henry Cort who got a patent for use of grooved rolls for rolling iron bars. Henry Cort is also called “father of modern rolling”. The first rail mill was established in 1820 while the first plate mill was exhibited in 1851. Three high mills for rolling heavy sections were introduced in 1853. Hot strip mill were developed in America in the first half of the twentieth century. Basic concept of the rolling The arc of contact between the rolls and the metal is a part of a circle. The coefficient of friction is constant in theory, but in reality it varies along the arc of contact. The metal is considered to deform plastically during rolling. The volume of metal is constant before and after rolling. In practice the volume might decrease a little bit due to close up of pores. The velocity of the rolls is assumed to be constant. The metal only extends in the rolling direction and there is no extension in the width of the material. The cross sectional area normal to the rolling direction is not distorted. Factors influencing rolling The major factors which influences the rolling process are given below The diameters of the rolls The amount of reduction in a...

Continuous Improvement Process...

Continuous Improvement Process In a quality organization, quality is a never ending quest and continuous improvement process (CIP) is a never ending effort to improve products, services or processes by discovering and eliminating the main causes of problems. Continuous improvement process accomplishes this by using small-steps improvements (incremental improvements over time), rather than implementing one huge improvement (breakthrough improvement) all at once. Organization having faith in CIP, continuously evaluate and improve products, services or processes with respect to quality, efficiency, effectiveness and flexibility. CIP provides many measures for gauging how well an organization is meeting the needs of its customers. CIP provides organizations a method for analyzing how work is currently being done and how processes can be improved to do the job more efficiently and effectively on an ongoing basis.  Organizations implementing CIP are to ensure the efforts for CIP implementation are aligned with the goals of the organization. There are several approaches and schools of thought for CIP. Most important of these are given below: Lean – This approach is evolved with increased voice of customer value added focus from Just-In-Time (JIT) principle. This has been initially practiced in the manufacturing industry. Six-Sigma – This approach has been evolved from Shewhart, Deming and Juran’s statistical quality control and total quality management focus upon satisfying customer expectations across multiple sectors. Theory of constraints – This approach has been evolved through continual refinement by Eli Goldratt to a present stage of advanced planning capability through critical chain functionality. These schools of performance improvements have been separately and collectively proven to be useful in last two decades in many organizations. Communication and information management is also critical to CIP but it is not mandatory for goal achievement. Key features of CIP Key features of CIP are given...

Slit rolling for bar production May30

Slit rolling for bar production...

Slit rolling for bar production In merchant bar mills with conventional rolling, rounds and rebars (both of them commonly known as bars) are produced from billets which are rolled in a sequence of passes through a multi stand rolling mill. Each of the stands is having a set of two rolls, grooved on the circumference to give together a desired pass shape. Cross section of the billet is gradually reduced and shaped in a sequence of passes till the final shape and cross sectional size is obtained. While rolling bars in a merchant bar mill, the productivity of smaller diameter bars is generally lower than the bigger diameter bars. To improve such productivity, one of the most significant developments in the area of bars production in recent years is the slit rolling. This method of rolling bars is also called “Multi Slit Rolling (MSR)”. The process of slit rolling is to roll two or more bars simultaneously from a single billet. When compared with the conventional single strand continuous rolling, MSR has reduced number of passes. The multi slit rolling technology use a combination of special roll pass design and designated guide equipment to prepare, shape and longitudinally separate the incoming billet into two or more individual strands for further rolling into the finished size. The bar is slit by rolls without any other special slitting devices. The numbers of slits can be selected by the appropriate design of the roll grooves. A bar can be separately split into two, three or four pieces in one pass. By selecting the number of slits according to the product size, the same productivity of all the products can be achieved in the bar mill. The slitting is done by applying axial force which is done by using special pass...

Special Bar Quality steels...

Special Bar Quality steels Special bar quality (SBQ) steels represents a wide variety of higher quality carbon and alloy steels. Although there is no single definition, special bar quality steel can be defined as steel that moves (rotates, twists or bends) rather than stays still whilst in use. The term is used to describe steel long products for more demanding processing or end-use applications which cannot be met by merchant quality grades. The term “Special Bar Quality” is a predominantly a North American term. In Europe, special bar quality steels are commonly known as “engineering steels”. Both these terms refer to steel types as well as to bar products, and as they are often associated with the steel grades, they refer to billet and slab as well as bar. SBQ steels are at the higher end of the quality spectrum in both metallurgical consistency and dimensional accuracy. Some end uses of these steels may require superior surface quality, or special chemical restrictions, metallurgical characteristics, heat treatment or surface finishes. The internal quality of these steels is very important since machining and bending activities are involved during the processing of these steels in subsequent stages. In order to achieve metallurgical quality, the steel has to be particularly clean. This makes the production route of these steels a bit complex. Steel cleanliness can be achieved through the integrated route or through an additional refining step and cleaner iron bearing inputs into an EAF in a mini mill. Internal metallurgical quality and consistency is also achieved by a meaningful reduction during the rolling process. These steels are produced both in cut lengths and coils. The specification of SBQ steels may range from plain carbon and carbon manganese steels to alloy and stainless steels containing different percentages of...

Customer Focus and Quality Organization...

Customer Focus and Quality Organization Quality organizations are those which recognize the importance of the customers. In these organizations quality normally begins and ends with customers. In these organizations all employees are one another’s customers and suppliers, who are linked in a chain that extend from within the organization to the external supplier and the external customer (Fig 1). Fig 1 Customer Supplier chain In an organization only a small percentage of employees are in direct contact with the external suppliers and external customers. However all the employees depend on the other employees to do their jobs. Hence every employee is a supplier to the employee who depends on him for the input and is a customer to the employee who supplies him with his output. In this way all the employees depend on other employees for the products or services they need to do their jobs. This simple customer supplier chain structure support various work processes in the organization and represents natural flow of work across functions and between employees within the organization. In fact, work of an employee can be seen as a process in which as a customer he receives inputs (e.g. machine parts, data etc.) from his supplier employee, add value (e.g. assembly, data processing etc.) to the inputs and then pass output (e.g. assembled part, processed data etc.) to his customer employee. Hence the prime concern of each employee should be the meeting of the requirements of his immediate customer. Alignment There should not be any conflict of interest between company’s interest and the customer’s interest. The alignment between the internal customer and the internal supplier is the matching of the capabilities of the supplier with the needs of the customer. In a quality organization, customers and suppliers work...