Role of Mould in Continuous Casting of Steel May21

Role of Mould in Continuous Casting of Steel...

Role of Mould in Continuous Casting of Steel  Moulds play an important role in the process of continuous casting of liquid steel. They are the heart of the continuous casting process. In the process of continuous casting, liquid steel is poured from the tundish into the casting mould through the submerged entry nozzle (SEN) immersed in the liquid steel. The moulds are water cooled. Solidification of liquid begins in the mould by indirect cooling. The cooling process in the mould is known as primary cooling process. In the mould, a thin shell of steel next to the mould walls solidifies before the middle section. This is called a strand and leaves the base of the mould into a spray chamber. The bulk of liquid steel within the walls of the strand is still molten. The strand is immediately supported by closely spaced, water cooled rollers which support the walls of the strand against the ferrostatic pressure of the still solidifying liquid steel within the strand. To increase the rate of solidification, the strand is sprayed with large amounts of water as it passes through the spray chamber. This is the secondary cooling process. Final solidification of the strand may take place after the strand has left the spray chamber. The function of continuous casting mould is to receive the liquid steel and guarantee a rapid heat transfer to the cooling water to enable quick solidification. The liquid steel, when leaving the mould, must exhibit a just thick enough outer shell to prevent it from splashing over the continuous casting machine parts. The mould is to serve this function. After the mould further cooling of the steel strand is done through the faster direct cooling with the help of the direct water sprays. Solidification arises from the dynamic...

White Cast Iron

White Cast Iron The term cast iron refers to those iron carbon silicon alloys which contain 1.8 % – 4 carbon (C) and usually 0.5 % – 3 % silicon (Si). Cast iron is an important engineering material with a number of advantages, mainly good castability and machinability and moderate mechanical properties. White cast iron contains 1.8 % -3.6 % C, 0.5 % -1.9 % Si and 1 % – 2 % manganese (Mn). White cast irons are so called because when broken, the fracture surface is white. This is unlike the grey fracture surface normally associated with other cast irons which contain graphite. White cast iron is a cast iron without any alloy addition and with low C and Si content such that the structure is hard brittle iron carbide (Fe?C, also called cementite) with no free graphite. A fast cooling rate prevents the precipitation of C as graphite. Instead the C, which is in solution in the melt, forms iron carbide. The structure of white cast iron consists of pearlite and ledeburite, a eutectic mixture of pearlite (converted from austenite) and cementite. Cementite is hard and brittle and dominates the microstructure of white cast iron. Thus, white cast iron is hard and brittle and has a white crystalline fracture because it is essentially free of graphite. Typical micro structure of white cast iron is shown in Fig 1. Fig 1 Typical micro structure of white cast iron White cast iron does not have the easy castability of other cast irons because its solidification temperature is generally higher, and it solidifies with C in its combined form as iron carbide. White cast iron has a high compressive strength and excellent wear resistance, and it retains its hardness for limited periods even up to a red...

Vision, Mission, and Values of an Organization...

Vision, Mission, and Values of an Organization Vision and mission both relate to an organization’s purpose and are typically communicated in some written form. Vision and mission are statements from the organization that answer questions about who we are, what do we value, and where we’re going. Vision and mission create a target for strategy development. Vision and mission provide a high level guide, and the strategy provides a specific guide, to the goals and objectives showing success or failure of the strategy and satisfaction of the larger set of objectives stated in the mission. Vision and mission statements play three critical roles. They are (i) to communicate the purpose of the organization to stakeholders, (ii) to inform strategy development, and (iii) to develop the measurable goals and objectives by which to gauge the success of the organization’s strategy. These interdependent, cascading roles, and the relationships among them, are summarized in the Fig 1. Fig 1 Key roles of vision and mission There are three reasons why an organization must develops vision and mission statements as shown above. First it helps the organization focus on what is really important. Although the organization knows what it is trying to do to improve the performance, yet it is easy to lose sight of this when dealing with the day to day hassles that plague all organizations. The vision and mission statements of the organizations help employees remember what is important as they go about doing their daily work. Second, organizational vision and mission statements let people and other organizations have a snapshot view of what the organization is and what it wants to do. When the organizational vision and mission statements are easily visible, people can learn about the organization without having to work hard for...

Beam Blank Casting Technology May14

Beam Blank Casting Technology...

Beam Blank Casting Technology The development of the direct casting of beam blanks is one of the most outstanding success stories in the evolution of the continuous casting of steel. The continuous casting of near net shape cross sections, called ‘beam blanks’ or ‘dogbones’, has been an efficient commercial process to manufacture long steel products such as I and H beams since the first beam blank caster was commissioned at Algoma Steel (now Essar Steel Algoma Inc., Sault Ste. Marie, Canada) in 1968. Its economics over conventional bloom casting are due to higher productivity, lower rolling costs and improved energy efficiency. As with many other innovations, the relatively conservative steel industry needed some time to accept this revolutionary concept. Its successful application depended on the inter-disciplinary co-operation and on the optimizing of casting and rolling process. This pioneering effort immediately attracted wide interest not only in the steel industry, but also by academia, e.g., in studying the solidification pattern of this complex strand shape. Nevertheless, it took another five years until the next beam blank caster got off the ground at Mizushima works of Kawasaki Steel Corporation. Continuous casting and rolling of beam blank has become a common practice in the steel beam production. Development in recent years concentrates in casting near net shape beam blanks. The difference between the conventional and near net shape beam blank is showed in Fig. 1. Conventional beam blank has a relatively thicker flange, usually over 100 mm, while the near net shape beam blank has a flange thickness less than 100 mm, usually with a lower limit 50 mm in the practice. Dozens, even a hundred beams can be produced through rolling only one beam blank. Fig 1 Conventional and near net shape beam blanks Beam blank...

Gray Iron

Gray Iron Gray iron (also called grey iron) is a type of cast iron that has a graphitic microstructure. It is named after the grey color of the fracture it forms, which is due to the presence of graphite. It is the most common cast iron and the most widely used cast material. Gray iron is one of the oldest cast ferrous products. In spite of competition from newer materials and their energetic promotion, gray iron is still used for those applications where its properties have proved it to be the most suitable material available. MacKenziein his 1944 Howe memorial lecture referred to gray cast iron as ‘steel plus graphite’. Although this simple definition still applies, the properties of gray iron are affected by the amount of graphite present as well as the shape, size, and distribution of the graphite flakes. Composition and effect of composition on properties  Gray iron is commercially produced over a wide range of compositions. The range of compositions which one may find in gray iron castings is given below. Carbon (C) – 2.75 % to 4.00 % Silicon (Si) – 0.75 % to 3.00 % Manganese (Mn) – 0.25 % to 1.50 % Sulfur (S) – 0.02 % to 0.20 % Phosphorus (P) – 0.02 % to 0.75 % One or more of the alloying elements namely molybdenum, copper, nickel, vanadium, titanium, tin, antimony, and chromium may be present in varying amounts. Nitrogen is generally present in the range of 20 to 92 ppm. Si is important for the gray iron since it is a graphite stabilizing element in cast iron, which means it helps the iron to produce graphite instead of iron carbides. Another factor affecting graphitization is the solidification rate. The slower is the rate, the greater is the tendency for graphite...