Wire and Rod Drawing Process for Steel Nov13

Wire and Rod Drawing Process for Steel...

Wire and Rod Drawing Process for Steel Drawing of wire from steel rod is a metal working process used for the reduction of the cross-section of the rod. Similarly rods are drawn from steel rounds of larger diameters. During drawing the volume remains the same and hence there is increased in the length of the drawn wire or rod. It is carried out by pulling the wire/rod through a single or a series of the drawing dies. In the case of series of drawing dies, the subsequent drawing die is to have smaller bore diameter than the previous drawing die. Drawing is usually performed in round sections at room temperature, thus it is classified as a cold working process. However, it can be performed at higher temperatures for large wires to reduce forces. Drawing process normally is most frequently used to produce round cross sections, but squares and other shapes can also be drawn. Wire/rod drawing is an important industrial process, providing commercial products. Rod and wire products cover a very wide range of applications which include shafts for power transmission, machine and structural components, blanks for bolts and rivets, electrical wiring, cables, wire stock for fences, rod stock to produce nails, screws, rivets, springs and many others. Drawing of rods from steel rounds is used to produce rods for machining, forging, and other processes etc. Advantages of drawing in the above applications include (i) close dimensional control, (ii) good surface finish, (iii) improved mechanical properties such as strength and hardness, and (iv) adaptability to economical batch or mass production. In the process of drawing, the cross section of a long rod or wire is reduced or changed by pulling (hence the term drawing) it through a die called a draw die. Pulling of rod...

Corrosion of Cast Steels...

Corrosion of Cast Steels Cast steels are generally classified into the categories of (i) carbon (C) steels, (ii) low alloy steels, (iii) corrosion resistant steels, and (iv) heat resistant steels, depending on the alloy content and the planned usage. Steel castings are categorized as corrosion resistant if they are capable of sustained operation when exposed to attack by corrosive agents at operating temperatures which are generally below 300 deg C. The high alloy iron base compositions are generally given the name ‘stainless steels’, though this name is not recognized universally. Actually, these steels are widely referred to as cast stainless steels. Some of the high alloy steels (e.g. 12 % chromium steel) show many of the familiar physical characteristics of C steels and low alloy steels, and some of their mechanical properties, such as hardness and tensile strength (TS), can be altered by suitable heat treatment. The alloy steels of higher chromium (Cr) content (20 % to 30 % Cr), Cr-Ni (nickel)  steels and Ni-Cr steels do not show the changes in phase observed in ordinary C steel when heated or cooled in the range from room temperature to the melting point. Consequently, these steels are non hardenable, and their mechanical properties depend on the composition instead of heat treatment. The high alloy steels (stainless steels) differ from C steels and low alloy steels in other respects, such as their production and properties. Special attention is required to be given to each grade with regard to casting design and casting practice in the foundry. For example, such elements as Cr, Ni, C, N2 (nitrogen), Si (silicon), Mo (molybdenum), and Nb (niobium) can exert a deep impact on the ultimate structure of these complex steels. Hence, balancing of the alloy compositions is normally required to...

Corrosion of Stainless Steels...

Corrosion of Stainless Steels Stainless steels (SS) are alloys of iron (Fe) which containing a minimum of 10.5 % chromium (Cr). With increasing content of Cr and with the presence or absence of many of other elements, SS can provide an extraordinary range of corrosion resistance. Different grades of SS are being used since several years in atmospheres which are mild (open air, in architectural applications) as well as extremely severe (chemical-processing industries). Stainless steels are classified in five families as per the crystal structures and the strengthening precipitates. Each family of SS shows its own general features in terms of mechanical properties and corrosion resistance. Within each family, there is a range of specifications which varies in composition, corrosion resistance, and cost. Stainless steels are vulnerable to several types of localized corrosive attack. The avoidance of such localized corrosion is the focus of most of the efforts made in the selection of SS. Also, the corrosion performance of SS is strongly influenced by practices of design, fabrication, surface conditioning, and maintenance. The selection of a grade of SS for a specific application involves the consideration of several factors, but the main factor remains corrosion resistance. It is the first necessity to specify the likely service environment. Besides considering the design conditions, it is also necessary to consider the reasonably anticipated exposures or upsets in service conditions. The suitability of a specific specification can be assessed from laboratory tests or from the documented field experience in similar atmospheres. Once the specification with satisfactory corrosion resistance has been identified, it is then appropriate to consider other factors such as mechanical properties, ease of fabrication, the types and degree of risk present in the application, the availability of the necessary product forms, and cost. Families of...

Nitrogen and Steels

Nitrogen and Steels Nitrogen (N) (atomic number 7 and atomic weight 14.008) has density of 1.25 gm/litre at standard temperature and pressure. Melting point of N is -210 deg C and boiling point is -195.8 deg C. The phase diagram of the Fe-N binary system is at Fig 1. Fig 1 Fe-N phase diagram N is present in all commercial steels. Since the of concerns of presence of N in steels are normally small and its analysis being complex and expensive, its existence is generally ignored even in steel specifications in various standards. However, whether present as a residual element or added deliberately as an alloying element, the effects of N in steel are significant.  N is an important and inexpensive alloying addition to steels. In recent years there has been an increasing demand to reduce and control the amount of dissolved gases in steel. N is one of the important gas which when dissolved in liquid steel affect its properties significantly. Hence control of N content of steels during steelmaking is important. N in steel can be in its uncombined form as free N or in the form of a compound or nitride. Steel from an electric arc furnace (EAF) normally has higher N levels (70-110 ppm) compared to that produced in a basic oxygen furnace (BOF) where N varies between 30 and 70 ppm. Hence, N is of particular importance in an EAF plant. In certain stainless steel grades the amount of N can be at the level of 3000 ppm. N levels in degassed steels can be below 10 ppm.  N exists in steel as an interstitial quite similar to, but much more soluble than, carbon (C) and as nitrides of iron (Fe), aluminum (Al), vanadium (V), niobium (Nb), titanium (Ti),...

Titanium in Steels

Titanium in Steels  Titanium (Ti) (atomic number 22 and atomic weight 47.90) has density of 4.52 gm/cc. Melting point of Ti is 1660 deg C and boiling point is 3287 deg C. Ti is a highly active element. It usually forms a stable oxide coating at room temperature on its surface, which limits further oxidation. The phase diagram of the Fe (iron)-Ti binary system is at Fig 1. Fig 1 Fe-Ti phase diagram Ti forms stable compounds with oxygen (O), carbon (C), nitrogen (N) and sulfur (S) at temperatures of steelmaking. It is sometimes used in steelmaking because of its property for fixing of these elements in order to reduce their harmful effects. Ti is also used for the purpose of grain refining in many steels. In many respects, functions of Ti are similar to the addition of both aluminum (Al) and niobium (Nb). Ti is more expensive than Al; hence it is rarely used as a deoxidizer.  The reactivity of Ti is similar to that of magnesium (Mg) and it can quite easily be set on fire. It burns with a bright white flame, which can be harmful to look at. Ferrotitanium powder is also flammable, with the powder having finer size and higher Ti content being more hazardous. Ti ores are mainly ilmenite (FeO.TiO2) and rutile (TiO2).  Addition agents Ti containing addition agents are Ti metal scrap, ferroalloys and master alloys. Ti metal scrap may be of commercial purity Ti. Ti metal scrap is of two types one with 6 % Al and 4 % vanadium (V) while the second with 6 % Al, 2 % tin (Sn), 4 % zirconium (Zr), and 2 % molybdenum (Mo). Sn is usually an unwanted element in steels. Since the melting point of Ti is...