Wire drawing

an overview of wire drawing process

1. A seminar Project on “AN OVERVIEW OF WIRE DRAWING PROCESS ” Presented by- Name- Ashutosh satpathy Branch-Mechanical engineering Regd no.-1707100009 Specialization-PEOM

2. CONTENTS INTRODUCTION PROCESS CHARACHTERSTICS OF WIRE DRAWING WIRE DRAWING TERMS THE MAJOR PROCESSING PARAMETER PRINCIPLE OF THE PROCESS FOR WIRE DRAWING WORKING PRINCIPLE OF DRAWING DIES DRAWING DEFECT AND RESIDUAL STRESSES ADVANTAGE OF WIRE DRAWING LITERATURE REVIEW OBJECTIVE CONCLUSION REFERENCE

3. Introduction In 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. Thus, the difference between drawing and extrusion is that in extrusion the material is pushed through a die, whereas in drawing it is pulled through it. Although the presence of tensile stresses is obvious in drawing, compression also plays a significant role because the metal is squeezed down as it passes through the die opening. For this reason, the deformation that occurs in drawing is sometimes referred to as indirect compression. Rod and wire products cover a very wide range of applications, including shafts for power transmission, machine and structural components, blanks for bolts and rivets, electrical wiring, cables,..Etc.

4. The basic difference between bar drawing and wire drawing: The basic difference between bar drawing and wire drawing is the stock size that is processed. Bar drawing is the term used for large diameter bar and rod stock, while wire drawing applies to small diameter stock. Wire sizes down to 0.03 mm are possible in wire drawing. The basic difference between wire drawing and tube making : In tube making is a hot working extrusion process and the wire drawing is cold working extrusion process, in the both operation working principle is same.

5. TYPES OF WIRE DRAWING HYDRO STATIC WIRE DRAWING:- It is now well established and is particularly suitable for brittle materials and composites. In hydrostatic Extrusion, It is not necessary that the billet be straight or cylindrical and it need not have a constant cross-sectional area along its entire length . BUNDLE WIRE DRAWING:- Although very fine wire can be produced by drawing, the cost can be high. One method employed to increase productivity is to draw many wires (a hundred or more) simultaneously as a bundle. Bundle drawing produces wires that are somewhat polygonal, rather than round, in cross- section. In addition to producing continuous lengths, techniques have been developed to produce fine wire that is chopped into various sizes and shapes.

6. TANDEM WIRE DRAWING:- It is clear that for fine wear,(below 10mm φ) , the drawing involves passage through several dies in series , especially for copper wire , which is very ductile. This is called multistage or tandem or continuous wire drawing . The wire is passed through several dies.

7. Degree of Drawing The degree of drawing is measured in terms of “reduction of area”which is defined as the ratio of the difference cross-sectional area before and after drawing to the initial cross sectional area RA= % elongation =

8. Process characteristics of wire drawing Pulls a wire rod through a die, reducing its diameter: - Wire drawing consists of pulling a metal wire through a small circular opening called a die. This results in a stretching or elongation of the material along with a reduction in cross sectional area. Increases the length of the wire as its diameter decreases:- Yield strength depends on material composition but typically the reduction in area through a die is in the region of 20 to 40%. If a greater reduction is needed this must be done by drawing the wire through a series of dies, each one smaller than the one before. Improves material properties due to cold working:- Wire drawing is usually performed cold, although there are some cases where metal is drawn hot to improve ductility. Die lubrication is essential in cold drawing to achieve a good surface finish as well to maximize the life of the die. Wire temperature can be controlled by swaging, drawing, and annealing treatments:- The temperature of wire is increase because of the high rate of pulling of wire , so temperature is increase if temperature is increase the process is hot extrusion process .If temperature is increases many defect arises so overcome the defect and temperature can be controlled by swaging ,drawing and annealing treatments.

9. The Major P rocessing P arameter [1]Draw Dies:- Four regions of the die can be distinguished: (1) entry, (2) approach angle, (3) bearing surface (land), and (4) back relief. The entry region is usually a bell-shaped mouth that does not contact the work. Its purpose is to funnel the lubricant into the die and prevent scoring of work and die surfaces. The approach is where the drawing process occurs. It is cone-shaped with an angle (half angle) normally ranging from about 6◦ to 20◦. The proper angle varies according to work material. The bearing surface, or land, determines the size of the final drawn stock. Finally, the back relief is the exit zone.

10. [2] Die Material:- Die materials for drawing typically are tool Steels and carbides. For hot drawing, cast-steel dies are used because of their high resistance to wear at elevated temperatures. High-carbon steels- Rod material for automatic processing, wire cables Alloy steels-Industrial springs, welding wires Cu and Cu alloys- Wires, wire meshes, screws, bolts and shaped parts, parts for the electrical Industry Al and Al alloys -Screws and bolts, shaped parts, electrical lines, etc   [3]Forces and Energy in Wiredrawing:- The forces and power in wiredrawing could be analysed by using simple tension, deformation conditions in wire are, in fact, far more complex due to compressive and drag forces generated by the die surface.

11. [4] DIE ANGLE:- Die angle is crucial for the success of any wiredrawing operation. Based on the fact that frictional work increases with decreasing die angle and redundant work increases with increasing die angle, an optimum approach angle should exist—one which minimizes both frictional and redundant work and, as a consequence, the drawing force . [5]TEMPERATURE:- Mostly it is a cold working extrusion process. The final operation before drawing is drying above 100 degree Celsius. Lubricant mostly used for control the temperature. [6]LUBRICATION METHOD:- Wet drawing, in which the dies and the rod are immersed completely in the Lubricant Dry drawing, in which the surface of the rod to be drawn is coated with a lubricant by passing it through a box filled with the lubricant Metal coating, in which the rod or wire is coated with a soft metal, such as copper or tin, that acts as a solid lubricant. Mostly various kind of mineral and vegetable oils, animal fats, graphite ,soap and certain emulsions are applied as drawing lubricant

12. Principle of the process for wire drawing The wire drawing die is conical shape. The end of the rod or wire, which is to be further is reduced is made into a point shape and inserted through the die opening. Before the wire is drawn, The stock needs to be prepared for wire drawing. The material should be sufficiently ductile since it pulled by the tensile forces. Hence, the wire may have to annealed properly to provide the necessary ductility.Further,the wire is to go through the conical portion and then pulled out through the exit by the gripper .In this process ,there is no force applied for pushing wire into the die from the entrance side. The other aspects of preparation needed are the cleaning of the wire and lubricating it as it flows through the die. Cleaning is essentially done to remove any scale and rust present on the surface which may severely affect the die.

13. For very large sizes, alloy steels are used in making the dies . The tungsten carbide dies are used most commonly for medium size wire and large production. The tungsten carbide dies are preferred are used most commonly for medium size and large productions. For very thin wires diamond dies are used. The drawing machines can be arranged in tandem so that , the wire is coming from one die is coiled up to a sufficient length before it is re-entered into the subsequent die , and so on ,there is no change in volume ,successive drawing have to be done at higher speeds.

14. Rolled coil Cleaning Descaling Annealing Lubricating Drawing Remove Scale – causing surface defects Oil and greases for wire drawing Mulsifiable oils for wet wire drawing. Soap for dry wire drawing (FLOW CHART OF PROCESS OF WIRE DRAWING)

15. Drawing Equipment: Wire drawing is accomplished on a machine called a draw bench, consisting of an entry table, die stand carriage, and exit rack. The carriage is used to pull the stock through the draw die. It is powered by hydraulic cylinders or motor-driven chains. The die stand is often designed to hold more than one die, so that several bars can be pulled simultaneously through their respective dies.

16. Working principle of drawing dies Wire drawing is done on continuous drawing machines that consist of multiple draw dies, separated by accumulating drums between the dies. Each drum, called a capstan, is motor driven to provide the proper pull force to draw the wire stock through the upstream die. It also maintains a modest tension on the wire as it proceeds to the next draw die in the series. Each die provides a certain amount of reduction in the wire, so that the desired total reduction is achieved by the series. It is depending on the metal to be processed and the total reduction, annealing of the wire is sometimes required between groups of dies in the series.

17. Different type of drawing die materials Mostly drawing dies are Cemented Carbide and Industrial Diamond Cemented carbides : These are the most widely used for drawing dies due to their Superior strength ,toughness and wire resistance Cemented carbides is composed of carbide of Ti, W, Ni, Mo, Ta, Hf. Poly crystalline diamond(PCD ): It is used for wire drawing dies for fine wires longer die life ,high resistance to wear, cracking or bearing.

18. Drawing Application Drawing is usually performed as a cold working operation. It is most frequently used to produce round cross sections, but squares and other shapes are also drawn. Wire drawing is an important industrial process, providing commercial products such as electrical wire and cable; wire stock for fences; and rod stock to produce nails, screws, rivets, springs. Advantages of wire drawing Close dimensional control. Improved mechanical properties such as strength and hardness. Adaptability to economical batch or mass production.

19. Drawing defects and residual stresses Typical defects in a drawn rod or wire are similar to those observed in extrusion especially centre cracking another major type of defect in drawing is seams, which are longitudinal scratches or folds in the material. Seams may open up during subsequent forming operations such as upsetting, heading, thread rolling, or bending of the rod or wire, and they can cause serious quality-control problems. Various other surface defects such as scratches and die marks also can result from improper selection of the process parameters, poor lubrication, or poor die condition. Residual stresses are induced in drawn bars or wires during cold drawing. If the reductions are low, the surface of the drawn part is subjected to compressive residual stress. Compressive residual stress on surface improves the fatigue life and corrosion resistance of the product.

20. LITERATURE REVIEW SL. NO Author Name Topic Description 1 P.Tiernan , M.T. Hillery An analysis of wire manufacturing using the dieless drawing method It is purposed that the mostly wire drawing is depend open the die , some of the cases wire drawing is known as die less wire drawing method . In this process has the capability to effect a reduction in the diameter of a wire without the use of conventional wire drawing dies. 2 L Filice,G Ambrogio , F Guerriero A multi objective approach for wire drawing process It is defined that a multi objective approach based on the optimisation of a set of objectives is presented –process force, die wear, material thinning and damage are considered building an optimisation problem 3 P.Schade wire drawing failures It is purposed that Wire drawing condition (temperature, drawing speed, reduction in area, die properties, stress state) material properties and fracture behaviour are interconnected, so some time different type of failure occure 4 viktor TITTEL effect of drawing angle size of a die on wire drawing and bunching process it is focuses on the effect of drawing anglesize of a die on the wire processing into a ropery at the bunching of steel cords ,mainly die angle is depend open the the die geometry on wire workability. 5 Hyon Moobeak , Young Gwanjin evolution of surface defects in wire drawing ,it is purposed the evolution of surface defect in wire drawing,in this study a 3D body ,it will evaluate the deformation behaiviour of various defects such as longitudinal ,transverse, oblique and round Introduced during manufacturing process

21. Objective of wire drawing Hollow wires and which are made by cold working process such as cold extrusion, often these are cold finished by drawing the main objective are: To obtain Closer dimension tolerances. To produce better surface finish. To increase the Mechanical properties of the wire by the process of wire drawing. To produce wire in regular shapes. Freedom from any chemical or other properties Fast process times. Varied speed ranges and torque requirements depending on material. Process can suffer from very little downtime. Due to speed, issues with the process can cause large amounts of scrap and lost revenue to overcome this problems

22. CONCLUSION Wire drawing is a well know process but today is living a new interest since many manufacturers tend to Substitute copper wires with aluminum ones. For this reason, high performance machines have been developed allowing the contemporary working of a number of wires. It was found that the numerical simulations matched well with the experimental results for an arbitrary introduced wire drawing. Therefore, the currently can be useful for the prediction of the evolution of the surface defects in the wire drawing. So, here it describes the parameter, working principle and defects of wire drawing process.

23. [1] https://www.sciencedirect.com/science/article/pii/S0924013698000454 [2] https://www.sciencedirect.com/science/article/pii/S0924013604005540 [3] https://www.sciencedirect.com/science/article/pii/0016003257903393 [4] theory-of-wiredrawing [5] Process_Characteristics_of_Wire_Drawing [6]A text book of production technology by P.C. SHARMA Reference