A REPORT ON IN-PLANT TRAINING AT
st
th
from 31 August 2012 to 5
September 2012
DONE BY, 1. 2. 3. 4. 5. 6. 7.
Nishad A Neeraj S Deth Arun S J Ahmad Mashhoor U M Manoj M P Sandeep C G Anuraj A R
Chavarcode, Parippally P.O. , Thiruvananthapuram, Pin 691574
ACKNOWLEDGEMENT
We have undergone 6 days days of In plant Training at Steel and Industrial Forgings Limited (SIFL) Athani P.O., Thrissur-680581, Thrissur-680581, Kerala, India, to fulfil the requirements of curriculum of my course B.Tech (Mechanical Engineering). We have immense pleasure in expressing our deep sense of gratitude, indebtedness and sincere thanks to Dr. P.K Balasubramanian Professor in ME & Academic Director and P Sreeraj Professor, ME College Valia Koonambaikulathamma College of engineering and technology, Parippally faring me an opportunity to undergo in-plant training at, SIFL, Thrissur. We express our sincere thanks to Lakshmi Narayanan (General ManagerWorks), E.V. Abdul Majeed (Deputy General Manager - Administration & Human Resource Development), M.A. Gopy (Sr. Manager), A.V. Mohanan (Heat Treatment Lab Manager), Anil Bose (QA Manager) and Babu (Deputy Manager Production) for giving us chance to undergo in-plant training at Steel and Industrial Forgings Limited (SIFL) Athani, Thrissur. And also we express our sincere thanks to all members of SIFL for their valuable inspiration, guidance & unforgettable co-operation during the training period. We take this opportunity to thanks our family members, friends and all others helping me directly or indirectly in in-plant training and stay at Thrissur onl y.
CONTENTS
1. About SIFL 2. Facilities at SIFL
1. ABOUT SIFL
Steel and Industrial Forgings Limited (SIFL) is a Government of Kerala undertaking commenced commercial production in 1986 and gradually forged ahead to become a name to reckon with. SIFL cater to a wide range of Industries in Defence, Automobile, Heavy engineering, Aero Space, Railways, Earthmoving Equipments, Agriculture etc... SIFL continued with landmark development, during the last quarter also. The company has been recommended for AS9100 certification . The remarkable products developed includes seven items for Arjun Mark-II, main battle tank being developed by CVRDE for INDIAN ARMY. This includes, Integral axle arms which are indigenized for the first time in the country and are of very complex in design Another technological feat which was successfully completed is the development of stainless steel valve body (S410) for BHEL, Trichy. This is the heaviest forging done by SIFL so far and weighs 550KG/piece. The company has became a partner in the prestigious Brahmos missile development program by obtaining an order from M/s Brahmos Aerospace Ltd, Hyderabad . This involves indigenization of forgings in Titanium, Aluminium and Stainless Steel Alloys. The preliminary production has been started and trial batch of forgings will roll out in March 2012. The company has to look beyond 2012 and set its sights higher, to realize its vision of becoming “ A globally well known enterprise making significant contribution to the wealth and welfare of the Nation ” with its mission of achieving Rs 100 Crore in 2012-2013, Rs 300 Crore by 2015 and Rs 500 Crore by the year 2020.
2. FACILITIES AT SIFL Main production machinery of SIFL comprise closed die forging hammers of 10 Ton(16000 ft.lb) and 6Ton(10650 ft.lb) capacity. Open die forgings requirements are met with a 1Ton clear space hammer. Other supporting facilities include shot blasting machines, Pneumatic trimming press of 1000Ton and 500Ton capacity, Hydraulic trimming press of 1200Ton capacity, Billet shearing machines and a number of oil-fired and electric furnaces for soaking as part of forging process. There is a modern heat treatment plant equipped with number of furnaces both LDO fired and electrically heated and a charging machine which takes care of loading and unloading of heat treatment charges. Our annual capacity is around 7500 Metric Tons. We manufacture closed die forgings in the weight range of 5 kg to 450 kg and open die forgings within 1kg to 75kg net weight per piece and ring rolling upto 650mmOD. The company has got the capability to manufacture forgings out of Carbon steels, Alloy steels, Stainless steels, Maraging steels, Aluminium alloys, Titanium alloys, Inconel(Su 718)etc
2.1 DIE DESIGN & DEVELOPMENT
SIFL's design & engineering capabilities are ably backed by a well equipped Die Shop, set up along modern lines with Double Spindle Copy Milling Machines, Electrical Die Sinking Machine, CNC Die Sinking Machine, CNC Turning Centre, Radial Drilling machines, Heavy Duty Plano miller, Lathes, Tool & cutter grinders, etc. The design and development of the die holds the key to blemish-free forgings. At SIFL, we design both single-impression and multi-impression dies. The design, of course, is related to the forging drawings. And the decision on the type of die to be used, is based on the specific requirement of each case. The care that goes into the design of each die, also goes into the selection of raw materials and the sequence of operation that follows. To facilitate uninterrupted operations, SIFL is equipped with standby Power Generators. To keep pace with hi-tech developments, SIFL has equipped itself with CAD,CAM facilities like DELCAM for three dimensional modeling of Product, Die & Tool design etc. thereby minimising the development cycle time ..All these qualities have helped SIFL grow quickly into a premier forging unit, capable of producing forgings with close dimensional tolerances
2.2 FORGING & HEAT TREATMENT FACILITIES The billets for forging are heated in oil fired or electric furnaces, closely controlling the temperature to reduce the scale formation and overheating so that the metallurgical properties are ensured in the final product. In addition, in-process inspection is carried out at all stages and 100% inspection for visual defects after forging. The accepted forgings are duly heat treated to ensure its mechanical properties. By providing heat treatment services in-house, SIFL is able to maintain greater control over heat treating process. The facility comprise batch furnaces both oil fired & electrical, continuous electrical heating furnaces, solution treatment etc. to carry out annealing, normalising, hardening, tempering, iso-thermal annealing, solution treatment etc or other operations as specified by our customer. Close temperature control and process monitoring with the help of temperature recorders ensures uniform properties duly supported by evaluation of metallurgical properties through representative test pieces.
2.3 TESTING/INSPECTION FACILITIES Surface conditioning is done by shot blasting/grinding and final inspection is carried out once again to ensure quality requirements. Non-conformities are taken care of b y timely corrective and preventive action. Calibration of electrical furnaces of SIFL are done by NABL accredited laboratories like HAL,STIC,CUSAT etc. SIFL has set up a system of total quality control consisting of an array of stateof-the-art speciality equipments where your products go through a series of rigorous tests, the destructive test including tensile, jominy and impact testing, wet analysis, carbon-sulphur determination, insitu metallography (where microstructure can be observed without destroying the job) and non-destructive tests using Spectrometer, Microscope, Magnaflux crack detection, Die Penetrant, Ultrasonic flaw detection etc. We are now equipped with a new digital ultrasonic flaw detector which has got a range of 5mm to 5m in steel. Setting and control of quality standards at all stages ri ght from the receipt of raw material to the finished product through quality plan makes us deliver superior quality forgings with close dimensional tolerances and metallurgical properties.
2.4 MANUFACTURING SIFL’s production machinery comprises of 10Ton & 6Ton imported air drop power hammers to manufacture closed die forgings in carbon and alloy steel, stainless steel,
aluminium, titanium and nicked base alloys etc. With a single piece of forging weight ranging from 10kg to 400kg.
3. FUNCTIONAL DESCRIPTION OF SIFL 3.1 RAW MATERIALS Bar stock, also colloquially known as billet, is a common form of raw purified metal, used by industry to manufacture metal parts and products. Most metal produced by a steel mill or aluminium plant i s formed (via rolling or extrusion) into long continuous strips of various size and shape. These strips are cut at regular intervals and allowed to cool, each segment becoming a piece of bar stock. The different billets used at SIFL are
Steel
Aluminium
Titanium
3.1.1 Steel Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten. Iron is found in the Earth's crust only in the form of an ore, usually an iron oxide, such as magnetite, hematite etc. Iron is extracted from iron ore by removing the oxygen and combining the ore with a preferred chemical partner such as carbon. This process, known as smelting, was first applied to metals with lower melting points, such as tin, which melts at approximately 250 °C (482 °F) and copper, which melts at approximately 1,100 °C (2,010 °F). In comparison, cast iron melts at approximately 1,375 °C (2,507 °F). The Society of Automotive Engineers (SAE) designates SAE steel grades. Carbon steels and alloy steels are designated by a four digit number, where the first digit indicates the main alloying element(s), the second digit indicates the secondary alloying element(s), and the last two digits indicate the amount of carbon, in hundredths of a percent by weight. For example, a 1060 steel is a plain-carbon steel containing 0.60 wt% C. SAE designation
Type
Carbon steels 10xx 11xx
Plain carbon (Mn 1.00% max) Resulfurized
12xx 15xx Manganese steels 13xx Nickel steels 23xx 25xx
Resulfurized and rephosphorized Plain carbon (Mn 1.00% to 1.65%)
Mn 1.75% Ni 3.50% Ni 5.00%
Nickel-chromium steels 31xx 32xx 33xx 34xx
Ni 1.25%, Cr 0.65% or 0.80% Ni 1.25%, Cr 1.07% Ni 3.50%, Cr 1.50% or 1.57% Ni 3.00%, Cr 0.77%
Molybdenum steels 40xx 44xx
Mo 0.20% or 0.25% or 0.25% Mo & 0.042 S[3] Mo 0.40% or 0.52%
Chromium-molybdenum (Chromoly) steels 41xx Cr 0.50% or 0.80% or 0.95%, Mo 0.12% or 0.20% or 0.25% or 0.30% Nickel-chromium-molybdenum steels 43xx 43BVxx 47xx 81xx 81Bxx 86xx 87xx 88xx 94xx 97xx 98xx
Ni 1.82%, Cr 0.50% to 0.80%, Mo 0.25% Ni 1.82%, Cr 0.50%, Mo 0.12% or 0.35%, V 0.03% min Ni 1.05%, Cr 0.45%, Mo 0.20% or 0.35% Ni 0.30%, Cr 0.40%, Mo 0.12% Ni 0.30%, Cr 0.45%, Mo 0.12%[3] Ni 0.55%, Cr 0.50%, Mo 0.20% Ni 0.55%, Cr 0.50%, Mo 0.25% Ni 3.25%, Cr 1.20%, Mo 0.12% Ni 0.45%, Cr 0.40%, Mo 0.12% Ni 0.55%, Cr 0.20%, Mo 0.20% Ni 1.00%, Cr 0.80%, Mo 0.25%
Nickel-molybdenum steels 46xx 48xx
Ni 0.85% or 1.82%, Mo 0.20% or 0.25% Ni 3.50%, Mo 0.25%
Chromium steels 50xx 50xxx 50Bxx 51xx 51xxx 51Bxx 52xxx Chromium-vanadium steels 61xx Tungsten-chromium steels 72xx
Cr 0.27% or 0.40% or 0.50% or 0.65% Cr 0.50%, C 1.00% min Cr 0.28% or 0.50%[3] Cr 0.80% or 0.87% or 0.92% or 1.00% or 1.05% Cr 1.02%, C 1.00% min Cr 0.80%[3] Cr 1.45%, C 1.00% min Cr 0.60% or 0.80% or 0.95%, V 0.10% or 0.15% min W 1.75%, Cr 0.75%
Silicon-manganese steels 92xx 0.00% or 0.65% High-strength low-alloy steels 9xx xxBxx xxLxx
Si 1.40% or 2.00%, Mn 0.65% or 0.82% or 0.85%, Cr
Various SAE grades Boron steels Leaded steels
Forging temperature 0 0 Steel - 960 C to 1250 C 0 0 Stainless Steel - 900 C to 1150 C
3.1.2 Aluminium Aluminium is a chemical element in the boron group with symbol Al and atomic number 13. It is silvery white, and it is not soluble in water under normal circumstances. Aluminium is the third most abundant element (after oxygen and silicon), and the most abundant metal, in the Earth's crust. It makes up about 8% by weight of the Earth's solid surface. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. The chief ore of aluminium is bauxite. Aluminium is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation. Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulphates. Aluminium Forgings are predominantly used in the automobile, electrical and pneumatic tools industry. Also aluminium components such as surgical tools, garden implements and even Golf Club heads are almost always produced through aluminium forging. Forging temperature - 3500C to 4400C
3.1.3 Titanium Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant (including sea water, aqua regia and chlorine) transition metal with a silver color. The two most useful properties of the metal form are corrosion resistance and the highest strength-to-weight ratio of any metal. In its unalloyed condition, titanium is as strong as some steels, but 45% lighter. Titanium is fairly hard (although not as hard as some grades of heat-treated steel), non-magnetic and a poor conductor of heat and electricity. Machining requires precautions, as the material will soften and gall if sharp tools and proper cooling methods are not used. 0
0
Forging temperature - 850 C to 940 C
3.2 FORGING Forging is a manufacturing process involving the shaping of metal using localized compressive forces. Forging is often classified according to the temperature at which it is performed: "cold", "warm", or "hot" forging. Forged parts can range in weight from less than a kilogram to 580 metric tons. Forged parts usually require further processing to achieve a finished part. Forging can produce a piece that is stronger than an equivalent cast or machined part. As the metal is shaped during the forging process, its internal grain deforms to follow the general shape of the part. As a result, the grain is continuous throughout the part, giving rise to a piece with improved strength characteristics. Some metals may be forged cold, but iron and steel are almost always hot forged. Hot forging prevents the work hardening that would result from cold forging, which would increase the difficulty of performing secondary machining operations on the piece. Also, while work hardening may be desirable in some circumstances, other methods of hardening the piece, such as heat treating, are generally more economical and more controllable. Alloys that are amenable to precipitation hardening, such as most aluminium alloys and titanium, can be hot forged, followed by hardening. Production forging involves significant capital expenditure for machinery, tooling, facilities and personnel. In the case of hot forging, a high-temperature furnace (sometimes referred to as the forge) is required to heat ingots or billets. Owing to the massiveness of large forging hammers and presses and the parts they can produce, as well as the dangers inherent in working with hot metal, a special building is frequently required to house the operation. In the case of drop forging operations, provisions must be made to absorb the shock and vibration generated by the hammer. Most forging operations use metal-forming dies, which must be precisely machined and carefully heat-treated to correctly shape the work piece, as well as to withstand the tremendous forces involved.
3.2.1 Upset forging Upset forging increases the diameter of the workpiece by compressing its length. Based on number of pieces produced this is the most widely used forging process. A few examples of common parts produced using the upset forging process are engine valves, couplings, bolts, screws, and other fasteners. Upset forging is usually done in special high-speed machines called crank presses, but upsetting can also be done in a vertical crank press or a hydraulic press. The machines are usually set up to work in the horizontal plane, to facilitate the quick
exchange of workpieces from one station to the next. The initial workpiece is usually wire or rod, but some machines can accept bars up to 25 cm (9.8 in) in diameter and a capacity of over 1000 tons. The standard upsetting machine employs split dies that contain multiple cavities. The dies open enough to allow the workpiece to move from one cavity to the next; the dies then close and the heading tool, or ram, then moves longitudinally against the bar, upsetting it into the cavity. If all of the cavities are utilized on every cycle then a finished part will be produced with every cycle, which makes this process advantageous for mass production. These rules must be followed when designing parts to be upset forged:
The length of unsupported metal that can be upset in one blow without injurious buckling should be limited to three times the diameter of the bar. Lengths of stock greater than three times the diameter may be upset successfully provided that the diameter of the upset is not more than 1.5 times the diameter of the stock. In an upset requiring stock length greater than three times the diameter of the stock, and where the diameter of the cavity is not more than 1.5 times the diameter of the stock, the length of unsupported metal beyond the face of the die must not exceed the diameter of the bar.
3.2.2 Drop forging Drop forging is a forging process where a hammer is raised up and then "dropped" onto the workpiece to deform it according to the shape of the die. There are two types of drop forging: open-die drop forging and closed-die drop forging. 3.2.2.1 Open Die Drop Forging
Open-die forging is also known as smith forging. In open-die forging, a hammer strikes and deforms the workpiece, which is placed on a stationary anvil. Open-die forging gets its name from the fact that the dies (the surfaces that are in contact with the workpiece) do not enclose the workpiece, allowing it to flow except where contacted by the dies. Therefore the operator, or a robot, needs to orient and position the workpiece to get the desired shape. The dies are usually flat in shape, but some have a specially shaped surface for specialized operations. For example, a die may have a round, concave, or convex surface or be a tool to form holes or be a cut-off tool. Open-die forging lends itself to short runs and is appropriate for art smithing and custom work. In some cases, open-die forging may be employed to rough-shape ingots to prepare them for subsequent operations. Open-die forging may also orient the grain to increase strength in the required direction.
Figure 1 : Notching
Figure 2 : Shaping
3.2.2.2 Closed Die Drop Forging
Closed die drop forging sometimes referred to as impression die forging comprises of a die on the anvil which resembles a mould, the ram which falls and strikes the top of the work piece can also be equipped with a die. The metal work piece is heated and placed on the lower die while the ram falls down forcing the metal to fill the contours of the die blocks. The ram may impact the work several times to ensure all of the contours are filled, with all the pressure put on the work piece its common place to get metal flow between the dies called flash, however the flash due to its decreased size cools relatively quickly and therefore helps block or reduce further flow between the dies. This flash will have to be trimmed off once forging is complete.
3.3 FORGING HAMMERS The most common type of forging equipment is the hammer and anvil. Principles behind the hammer and anvil are still used today in drop-hammer equipment. The principle behind the machine is simple: raise the hammer and drop it or propel it into the workpiece, which rests on the anvil. The main variations between drop-hammers are in the way the hammer is powered; the most common being air and steam hammers. Drop-hammers usually operate in a vertical position. The main reason for this is excess energy (energy that isn't used to deform the workpiece) that isn't released as heat or sound needs to be transmitted to the foundation. Moreover, a large machine base is needed to absorb the impacts. To overcome some shortcomings of the drop-hammer, the counterblow machine or impactor is used. In a counterblow machine both the hammer and anvil move and the workpiece is held between them. Here excess energy becomes recoil. This allows the machine to work horizontally and have a smaller base. Other advantages include less noise, heat and vibration. It also produces a distinctly different flow pattern. Both of these machines can be used for open-die or closed-die forging. Forging hammers employed at SIFL include 1 Ton, 6 Ton and 10 Ton hammers. An order for procuring 16 Ton pneumatic hammer has been placed.
3.4 FORGING PRESSES A forging press, often just called a press, is used for press forging. There are two main types: mechanical and hydraulic presses. Mechanical presses function by using cams, cranks and/or toggles to produce a preset (a predetermined force at a certain location in the stroke) and reproducible stroke. Due to the nature of this type of system, different forces are available at different stroke positions. Mechanical presses are faster than their hydraulic counterparts (up to 50 strokes per minute). Their capacities range from 3 to 160 MN (300 to 18,000 short tons-force). Hydraulic presses use fluid pressure and a piston to generate force. The advantages of a hydraulic press over a mechanical press are its flexibility and greater capacity. The disadvantages include a slower, larger, and costlier machine to operate. Two forging presses are employed at SIFL having capacities 500 Ton and 1000 Ton.
3.5 DIES In forging processes, several operations are often required to achieve gradual metal flow from a simple shape of initial billet to a more complex shape of the desired final forging. Amongst various kinds of preforming operations, the blocker is the stage that is normally used before the finishing operation. The geometry of the blocker cavity is often similar to that of the finisher. An appropriate design of the blocker preform can lead to a defect-free metal flow in the final forging operation and complete die-filling with minimum metal loss and die wear. However, the optimum design of the blocker die is an extremely difficult task and is known to be an art by itself, requiring skills that are achieved only by years of extensive experience.
3.5.1 Die materials The exact material used to make a forging die is dependant upon all the details of that particular forging process. In general a forging die must be tough, possess high strength and hardness at elevated temperatures, good shock resistance, resistance to thermal gradients, hardenability and ability to withstand abrasive wear. During the manufacture of a hot forged part the mold is usually preheated before the operation begins. Preheating die reduces thermal cycling that can cause cracks in the die. Forging die are hardened and tempered. Mold dimensions must account for shrinkage of the work, as well as extra material allowances for the finishing of the part. The abrasive wear present in hot forging operations is due largely to the scale on the work piece. Much of the scale can be removed from the blank immediately after heating in the furnace, prior to the forging of the part. Adequate lubrication can also greatly mitigate wear. Sometimes a mold may be assembled using different sections. These sections, called die inserts are manufactured separately and may be of different materials. Complex cavities can be produced easier with die inserts, also different sections of the mold can be individually replaced. Some factors to consider when determining the material composition of a forging mold are, type of metal forming operation, number of forgings desired, size of forged part, complexity of forged part, type of machinery to be used, temperature that the part will be forged at, and the cost of materials. Forging die are made from tool steels, that depending upon process criteria are alloyed with various levels of one or more of these materials, chromium, molybdenum, vanadium, and nickel. Die blocks are cast from the alloy, metal formed, then machined, and finished.
3.5.2 Forging Die Design Forging die design will always depend on the factors and requirements of the manufacturing process. However, there are some general principles to consider for good forging die design. During the forging process metal is flowing under pressure to fill the impression within the mold. Similar to the metal casting process of die casting, in forging, an increase in pressure on the metal within the mold will increase the ability to fill the mold completely. One main difference being that in die casting the metal is liquid, while in forging, the work is a solid metal above or below its recrystallization temperature. Smaller, thinner, longer, and more complex sections can be produced with more pressure, but too much pressure within the mold is bad because it can damage the die and machinery. The formation of flash is an important part of impression die forging manufacture. First, flash provides a way for excess material from the work piece to exit the mold. If this material could not escape during compression, the build up of pressure as the volume of work metal exceeded the volume of the mold could easily crack the die. Flash, while allowing material to escape does increase the pressure within the die cavity (mold). Flash must travel through a narrow passage called land before it opens up into a gutter. As it flows through land, the friction between the flash and the mating surfaces resists further flow of material out of the mold, increasing pressure within the mold. In addition the cooling of the flash from the mating surfaces increases resistance to flow of material out of the mold, thus also increasing pressure within the die cavity. A longer land will cause the flash to have to flow further under resistance increasing the mold pressure. Decreasing the width of land will increase the cooling rate of the flash, as the temperature goes down the metals resistance to flow goes up. More resistance to flow will cause a thinner land to have higher mold pressure. The pressure within the die cavity is often controlled by varying the width of land.
3.6 LUBRICATION IN INDUSTRIAL FORGING Frictional forces within the mold, between the work and the surfaces of the die cavity, have a large influence over the flow of material in a forging operation. Lubricants are used in industrial forging production in order to lower frictional forces, and enact a smoother flow of metal through the mold. In addition they are used to slow the cooling of the work and reduce temperature gradients in hot forging manufacture, serving as a thermal barrier between the metal and the mold. Lubricants also help keep the metal and die surfaces from sticking together and assist in the removal of the for ging from the die. Common lubricants used in modern forging industry include, water, mineral oil, soap, saw dust, graphite, molybdenum disulfide, and liquid glass.
3.7 HEAT TREATMENT Heat treating is a group of industrial and metalworking processes used to alter the physical, and sometimes chemical, properties of a material. The most common application is metallurgical. Heat treatments are also used in the manufacture of many other materials, such as glass. Heat treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a desired result such as hardening or softening of a material. Heat treatment techniques include annealing, case hardening, precipitation strengthening, tempering and quenching. It is noteworthy that while the term heat treatment applies only to processes where the heating and cooling are done for the specific purpose of altering properties intentionally, heating and cooling often occur incidentally during other manufacturing processes such as hot forming or welding.
3.7.1 Physical Processes Metallic materials consist of a microstructure of small crystals called "grains" or crystallites. The nature of the grains (i.e. grain size and composition) is one of the most effective factors that can determine the overall mechanical behaviour of the metal. Heat treatment provides an efficient way to manipulate the properties of the metal by controlling the rate of diffusion and the rate of cooling within the microstructure. Heat treating is often used to alter the mechanical properties of an alloy, manipulating properties such as the hardness, strength, toughness, ductility, and elasticity. There are two mechanisms that may change an alloy's properties during heat treatment. The martensite transformation causes the crystals to deform intrinsically. The diffusion mechanism causes changes in the homogeneity of the alloy.
3.7.2 Annealing Annealing is a rather generalized term. Annealing consists of heating a metal to a specific temperature and then cooling at a rate that will produce a refined microstructure. Annealing is most often used to soften a metal for cold working, to improve machinability, or to enhance properties like electrical conductivity. In ferrous alloys, annealing is usually accomplished by heating the metal beyond the upper critical temperature and then cooling very slowly, resulting in the formation of pearlite. In both pure metals and many alloys that can not be heat treated, annealing is used to remove the hardness caused by cold working. The metal is heated to a temperature where recrystallization can occur, thereby repairing the defects caused by plastic deformation. In these metals, the rate of cooling will usually have little effect. Most non-ferrous alloys that are heat-treatable are also annealed to relieve the hardness of cold working. These may be slowly cooled to allow full precipitation of the constituents and produce a refined microstructure.
Ferrous alloys are usually either "full annealed" or "process annealed." Full annealing requires very slow cooling rates, in order to form coarse pearlite. In process annealing, the cooling rate may be faster; up to, and including normalizing. The main goal of process annealing is to produce a uniform microstructure. Non-ferrous alloys are often subjected to a variety of annealing techniques, including "recrystallization annealing," "partial annealing," "full annealing," and "final annealing." Not all annealing techniques involve recrystallization, such as stress relieving.
3.7.3 Normalizing Normalizing is a technique used to provide uniformity in grain size and composition throughout an alloy. The term is often used for ferrous alloys that have been heated above the upper critical temperature and then cooled in open air.[17] Normalizing not only produces pearlite, but also bainite and sometimes martensite, which gives harder and stronger steel, but with less ductility for the same composition than full annealing.
3.7.4 Quenching
Quenching is a process of cooling a metal very quickly. This is most often done to produce a martensite transformation. In ferrous alloys, this will often produce a harder metal, while non-ferrous alloys will usually become softer than normal. To harden by quenching, a metal (usually steel or cast iron) must be heated above the upper critical temperature and then quickly cooled. Depending on the alloy and other considerations (such as concern for maximum hardness vs. cracking and distortion), cooling may be done with forced air or other gases, (such as nitrogen). Liquids may be used, due to their better thermal conductivity, such as water, oil, a polymer dissolved in water, or a brine. Upon being rapidly cooled, a portion of austenite (dependent on alloy composition) will transform to martensite, a hard, brittle crystalline structure. The quenched hardness of a metal depends on its chemical composition and quenching method. Cooling speeds, from fastest to slowest, go from polymer (i.e. silicon), brine, fresh water, oil, and forced air. However, quenching a certain steel too fast can result in cracking, which is why high-tensile steels such as AISI 4140 should be quenched in oil, tool steels such as ISO 1.2767 or H13 hot work tool steel should be quenched in forced air, and low alloy or medium-tensile steels such as XK1320 or AISI 1040 should be quenched in brine or water. However, most non-ferrous metals, like alloys of copper, aluminium, or nickel, and some high alloy steels such as austenitic stainless steel (304, 316), produce an
opposite effect when these are quenched: they soften. Austenitic stainless steels must be quenched to become fully corrosion resistant, as they work-harden significantly.
3.7.5 Tempering Untempered martensitic steel, while very hard, is too brittle to be useful for most applications. A method for alleviating this problem is called tempering. Most applications require that quenched parts be tempered. Tempering consists of heating a steel below the lower critical temperature, (often from 400 to 1105 ˚F or 205 to 595 ˚C, depending on the desired results), to impart some toughness. Higher tempering temperatures, (may be up to 1,300 ˚F or 700 ˚C, depending on the alloy and application), are sometimes used to impart further ductility, although some yield strength is lost. Tempering may also be performed on normalized steels. Other methods of tempering consist of quenching to a specific temperature, which is above the martensite start temperature, and then holding it there until pure bainite can form or internal stresses can be relieved. These include austempering and martempering.
3.8 TESTING AND INSPECTION The different types of testing processes include Non-Destructive testing o o o
Ultrasonic testing Magnetic particle Dye penetrant
Physical/chemical testing o
Tensile strength
o
Charpy impact
o
Drop weight
o
Metallography
o
Mass spectrography
o
Radiographic
o
Brinell and Rockwell hardness
o
Alloy separation
3.8.1 Ultrasonic testing The product is tested with sound wave emission and the amount of waves coming back is indicating if some non conformities are present. The problem is that it cannot be performed on every material. The austenitic material is difficult to test as well as the grey (flake) and malleable irons. The other problem is that the operator is reading the result on the screen and that there is no prove for later discussion in the form of a paper or file. The advantage is that the equipment is not expensive and the tests can be done everywhere. The second advantage is that the location of the non conformance is easy to state (with simple calculations). The method can also be used for: 1. structure and graphite morphology testing, using the v alue of the sound velocity 2. thickness measurements.
3.8.2 Magnetic Particle Testing This test is used to detect non-conformities in and just below the surface. Depending on the strength of the magnetic field, the thickness of the tested surface layer is set. It requires a set up location that can be darkened to have a good picture of the involved indications. The length as well as the surface of the non-conformity is measured and evaluated with the standard descriptions. The advantage is that it can also measure the layer below the surface and the result is easier to evaluate for irons (materials with a loose structure). The disadvantage is that it requires a conform location and the equipment can cost a lot (especially the high current types for deep testing).
3.8.3 Dye penetrant test The liquid penetrant method does use a penetrating fluid, which does fill every surface non-conformity like: 1. cracks 2. surface porosity 3. open structure (irons). It must be properly applied and a picture can be taken. The result is evaluated by the comparison with reference pictures, provided with the standards. The disadvantage is that it is time consuming and it uses products, which must be removed completely after the test to avoid surface damage like corrosion. Most of the tests are done without pictures, which anyhow must be taken on the prescribed time to be valid. The advantage is that it is, especially for small surface area very cheap and does not require an investment in equipment. The other advantage is that it can be used for all types of materials.
4. DEPARTMENTS IN SIFL The following are the main departments in SIFL : 4.1 Technical Department 4.2 Production Planning and Control (PPC) 4.3 Quality Assurance (QA) 4.4 Heat Treatment and Laboratory (HT & Lab) 4.5 Die Shop 4.6 Forging Shop 4.7 Maintenance Department 4.8 Materials Management Department 4.9 Finishing & Dispatch (F&D)
4.1 TECHNICAL DEPARTMENT
The technical department initiates all the processes at SIFL. When a customer makes his order at SIFL, the technical department determines the feasibility of the product and prepares the estimate for the product. If both the customer and the company agrees over the estimate, SIFL proceeds with the order. Technical department enquires about the requirements, facilities and equipments available at the company for production. If any of the requirement is not available in the company they make provisions for either procuring them from an external source or developing it at the company itself. Technical department is responsible for preparing all the designs required for the job. These designs include blocker design, if required, finisher design, die design etc... It also prepares the drawings for these. Computer softwares are used for drawing and drafting purposes. The important softwares include SolidWorks, Catia, Pro-E. Technical department prepares the process sheet for each job. As per the requirements of the customer technical department gives the order for procuring the material of the job. The materials forged at SIFL are steel, stainless steel, aluminium and titanium. Steel is purchased from Steel Authority of India Limited (SAIL). 4.2 PRODUCTION PLANNING AND CONTROL (PPC) At SIFL it is usually referred by its abbreviation PPC. When the technical department give its nod for a job, it is then forwarded to the PPC. PPC after contacting with every departments, prepares the schedule for the job. This
schedule includes all the operations to be performed on the job like cutting material, upsetting, finisher forging, heat treatment, shot blasting, grinding, inspection etc.. PPC also prepares the daily and monthly schedules for each department. If any of the operations could not be completed on time as expected, PPC makes the required adjustments on the schedule. Also it allots some backup time for each job in case anything goes wrong. Sundays are usually allotted for maintenance department. 4.3 QUALITY ASSURANCE (QA) QA is one of the most important department of SIFL. After each stage of production QA is responsible for checking the quality of every single job. The customer may have certain demands for a job in terms of its hardness, strength, finish and it is the duty of QA department to ensure this. QA uses many state-of-the-art techniques for ensuring quality like equo tip hardness tester, spectrography etc.. The main methods used by QA include
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Ultrasonic testing Magnetic particle Dye penetrant Tensile strength
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Charpy impact
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Mass spectrography
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Brinell and Rockwell hardness
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4.4 HEAT TREATMENT AND LABORATORY
The heat treatment system with its charging machine is one of the latest and best available in the country. The facilities include oil fired, electrical continous and bogie hearth furnaces, muffle furnaces etc. to carry out annealing, normalizing, hardening, tempering, isothermal annealing etc. or any other operations as specified by the customers. There are about 10 furnaces in the HT department. Charging machine is used to load the jobs into the furnaces and it has movement in many axes.
Quenching facilities available at the heat treatment shop are oil quenching, water quenching and air quenching. QA department carry out the hardness testing
process for each and every job and if any corrections are required, they suggest the retreatments as necessary.
4.5 DIE DESIGN
SIFL design both single and multi-impression dies. S IFL has now started using CAD/CAM facilities for die design and developments. This has helped SIFL to grow quickly into a premier steel forings unit, capable of producing highly complex and precision closed die forgings with close dimensional tolerances.
Numerous machine tools are employed at SIFL for developing the dies. A HMT make CNC lathe and Johnford make CNC milling machine are used in the die shop. The commonly used machines like conventional lathes, milling machines, drilling machines, coping machines etc. are also used. Templates are prepared for every die designs to check the die impressions for dimensional tolerances. Earlier models made from wood or plaster of paris was used to check the accuracy.
For a job it may require to make several blockers and finishers and the die shop is entitled to prepare all these. Material used for making die is a special grade of steel known as die steel which is directly imported from Germany as solid blocks. SIFL cuts the required angles for the dovetail for holding it in t he hammer. It also bores the holes for both 6T and 10T hammers.
4.6 FORGING SHOP
Forging shop can be said as the core department of SIFL. It is from here that the required shape of the job is produced. Forging shop currently employs three hammers of capacities 1 ton, 6 ton and 10 ton. An order for 16 ton has been placed which will be commissioned soon. The dies are fixed on the hammer with keys and locks. The upper die is fixed on the moveable part i.e. piston of the hammer and the lower die is fixed on the stationary vice. The steel and aluminium billets are first heated to the red hot condition in an oil furnace whereas titanium billet is heated in an electric furnace and then placed on the die with the help of tongs. The hammer is dropped from a height on to the workpiece several times until the required shape is achieved. Mechanism used for
lifting and dropping hammer is pneumatic valve mechanism. 6T hammer uses two valves and 10T hammer uses a single valve mechanism.
After drop forging the flash of the job are removed by presses. Two presses are used at SIFL of capacities 500 ton and 1000 ton.
4.7 MAINTENANCE DEPARTMENT
Maintenance department carries out predictive maintenance at regular intervals. Sundays are usually allotted for maintenance works when no other works are held at the company. Maintenance engineers carry out operations like inspection, testing, repairing, lubrication level checking etc. Also breakdown maintenance are performed in case of breakdown of any machines. A breakdown of any machines cause bottleneck of production. Sometimes experts from outside the company may be required to perform the repairing operations such as the complex welding processes performed by L&T personnels.
4.8 MATERIALS MANAGEMENT DEPARTMENT (MMD)
This department is responsible for the storage and management of the materials, jobs and all other equipments required for the processes. It houses a store for storing the tools and devices like the drill bits, cutting tools, grinders, nuts, bolts etc. MMD keeps a Goods Receipt Inspection Note (GRIN) for everything received at the store and it requires a Storage Requisition note for any department to obtain anything from the store. Goods inquired by a department will not be supplied to any other department from the store. Monthly assessment is done for the things stored at the store. It also carries out yearly auditing.
4.9 FINISHING AND DISPATCH
Finishing and Dispatch department is responsible for finishing the job and reaching it to the customer in the demanded condition. Smaller finishing operations like coarse and fine grinding is carried out at SIFL plant in Athani and for higher finishing operations requiring high grades of finish are either machined at the SIFL machining unit in
Shoranur or outsourced to external agencies. Punching operations as demanded by the customer are also performed at SIFL. Finished products are finally dispatched to the customer on their scheduled time.
CONCLUSION
Steel and Industrial Forgings Limited (SIFL) is a premier industry in the manufacturing sector of India. It is the numero uno company in South India in terms of jobs produced. With a realistic production capacity is 5000MT/annum of closed die forgings, SIFL specializes in the medium and heavy range of forgins of alloy steel, super alloys, aluminium and titanium.
Untiring efforts of two decaded has saddled firmly in the forging industry scenario of India and abroad with best ratings for its products and services. Forgings with a exquisite designs and shapes, flawless forms and contours, broadbands and spectra of metals including titanium and aluminium: all in wide range of weights and unmatched quality have made SIFL the most sought after Forge shop in the country for critical components.
Competence and willingness of SIFL to take up forgings in special alloys and materials of unique chemistry has stood SIFL in good stead for assuring a niche market in the premium weight range for a variety of forgings. SIFL have so far developed more than 700 different forgings for various applications.
REFERENCE [1] The art of perfect forging, SIFL brochure [2] S.K. Hajra Choudhury, A.K. Hajra Choudhury, Nirjhar Roy, Elements of Workshop Technoloy Vol. II, Media Promoters & Publishers Pvt. Limited [3]
