Milling Mc

CHAPTER-1

1.1

INTRODUCTION

What is Profile Hot Rolling? As we know, Mechanical Working of a metal is simply plastic deformation performed to change dimensions, properties, and/or surface condition by means of mechanical pressure. Mechanical working may be either hot working or cold working. Plastic deformation above recrystallization temperature, but below the melting or burning point is called hot work. Some hot working processes are Extrusion is a process in which a heated billet or slug of metal is forced by high pressure through an orifice that is shaped to provide the desired form to the finished part. Drawing is pulling the metal through a die or a set of dies to achieve a reduction in diameter. Rolling is the most rapid method of forming metal into desired shapes by plastic deformation in between rolls. In the hot rolling process, metal in a plastic state is passed between two rolls revolving at the same speed but in opposite direction. As metal passes through the rolls, it is reduced in thickness and increased in length. It is used either for changing dimension of metal sheets or for forming of bars having cross sectional area of simple shapes, i.e. square, rectangular Think of the large number of small components used to manufacture a variety of appliances, instruments, equipment and machinery. From springs to blades, cutting tools to chisels and sections to rings. Though so large in numbers quantity when translated into tones. High precision parts which are used in small quantities may turn out to be too low weight wise to justify production on

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conventional Rolling Mills. The machining of rounds into different shapes to continues conventionally. The result? Increased labor, heavy tooling charges and prolonged schedules leading to a build up of unnecessarily large inventories at the users’ end. The Profile Rolling Mill, on the other hand, is a new concept in India and has some unique features. Various pre-shaped sections with stringent dimensional tolerances can be produced on it thereby avoiding the scrap generated due to turning or milling. We can also call this process as Unconventional Rolling process.



Advantages Over Conventional Rolling Such an arrangement of continuous heating & rolling has following advantages over conventional rolling:

•

Reduced scaling on account of electrical heating.

•

Better dimensional tolerances due to reduced scaling.

•

Consistency in dimensions due to continuous rolling.

•

Reduced material wastage on account of better tolerances.

•

Reduced cost of machining operations and saving in time.

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CHAPTER-2 2.1

PROFILE HOT ROLLING MILL The Profile hot rolling mill has a state of the art manufacturing facility for

producing 6000 MT per annum of hot rolled & cold drawn solid steel sections with close dimensional tolerances. This mill is manufactured by FALCI in Italy. These types of only four mills are in the whole world. From these four mills two are it self in Italy, one is in U.S.A and last one is in India. The uniqueness of this latest technology lies in the fact that the profiles are rolled from wire rods that are continuously heated on-line with electrical resistance heaters, unlike from billets that are heated in fuel fired furnaces in conventional rolling mills. Hot rolled profiles are solid shapes or sections that are manufactured from either billets or wire rods. Unlike extrusion, where molten metal is pushed through a die to obtain the required shape, the hot rolling process involves shaping of the heated billets or wire rods by passing through a set of rolls that are rotating in opposite direction. These roll sets are arranged in tandem in a number of rolling stands. The rolls have groves cut in it as per the specific roll pass design and each roll has a different set of groves. These profiles or sections have the same shape or cross section throughout the length i.e. they are two dimensional shapes.

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2.2 GENERAL SPECIFICATION  Manufacturing

:

FALCI, Italy

 Plant capacity

:

6000 MT/annum

 Connected electric load

:

1000 KVA, 380 volts

 Raw material

:

Hot rolled wire rod

 Rolling speed

:

Rod entry speed 4 to 14 m/min

 Steel grade

:

Mild Steel, Medium Carbon steel, High Carbon steel, Alloy steel, Stainless steel

 Specific Weight of Profiles :

0.2 Kg / meter to 4.5 Kg / meter

 Width of Profiles

:

8 mm to 55 mm.

 Thickness of Profiles

:

3 mm minimum.

 Length of Profiles

:

3000 mm to 11000 mm

 Weight of Profiled Coils

:

500 Kg. maximum

 Tolerance

:

On thickness  +/- 0.2 to +/- 0.5 mm.

On width

 +/- 0.2 to +/- 0.5 mm.

On length

 + 100 mm, - 0 mm.

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2.3 PROFILE HOT ROLLING MILL COMPONENTS 

Uncoiler : In profile hot rolling process, uncoiler is also called raw material holding equipment. The raw material of hot rolled wire in its coiled form loaded on uncoiler. And as its name suggests it is used for uncoiling the raw material for further process. fig.(2.1)



Straighter: The raw material from uncoiler is in very uneven shape. To convert

this uneven shape in to the straight form straighter is used. For

straightening purpose it carries total 18 rollers. These rollers are arranged in such a way that raw material has one line passage to pass. From 18 rollers, first nine rollers punch the raw material vertically and remaining nine punch horizontally. Arrangement of all 18 rollers are shown in fig.(2.2) 

Chain puller: The function of the chain puller is to guide the free end of coiled raw material rod to the vertical roller of the straighter. Mostly it is fixed with the straighter at bottom.



De-scale: Descaling is the process of removing the scales and rough particles from the rod so during the further processes there may not remain any impurities on the profile.



Heating zone: By using of heating elements, the temperature of rod can be increased. Three heating elements, which are called heating zone 1, heating zone 2 and heating zone 3. Each heating zone is connected with electric load of 1000 KVA and 380 Volts. The current is passed in increasing order through each zone. The heating zone 3 has maximum current about 800 to 1000 amp. , which differs with the different raw materials. At zone 3 the raw material rod becomes red hot. After this zone the actual rolling process has been started.

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FIG.-2.1: UNCOILER

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FIG.-2.2 : ARRANGEMENT OF ROLLERS IN STRAIGHTER



Mill stand : The red hot material from heating zones is directed to mill

stands, which are in 4 nos. Each mill stand has a pair of rolling assembly, which contains one top roll and one bottom roll. These rolls revolving at same speed but in opposite direction. The shape of profile cross section that we want is grooved on these rollers. By passing the red hot material between the rolls and applying tremendous amount of pressure on it, we get required shape of profile. Four numbers of stands are required for increasing no. of pass, so profile is made well finished and perfectly shaped.



Pinch roll drive: The profile, coming out from mill stands, is very hot.

Pinch roll drive is used to grip this hot profile in such a way that the shape of profile doesn’t change. Then after it draws the profile to the shear carefully. 

Shear cutter: Profile rolling process is continuous process, so after

rolling profile is cut in required length (between 3 m to 11 m).for cutting purpose shear is used. For cutting of these type of hot metal we need cutter having sharp edge which cuts profile rapidly only in one pass. 

Cooling bed: For cooling of hot profile cooling bed is required, which

has length same that of profile which is required.

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

Pusher blade: Pusher blade is used to push profile having required

length from cooling bed to collection bed. At collection bed profiles are cooled at atmospheric temperature by natural heat transfer.



Profile projector: It is not a part of mill, but very important for completion of

process. It is used for inspection purpose of profile section. Here profile section is enlarged ten times of actual with the help of projector and check with the original sectional drawing.

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CHAPTER-3 3.1

PROFILE HOT ROLLING PROCESS The profile hot rolling process is divided in to two processes. First process is named manufacturing of rolls and second, which is performed on mill.

3.1.1

Manufacturing of the rolls This process is considered as pre-rolling process. This process plays very important role, because the complicate profile shape is grooved first on rolls and afterward by pressing steel rod between rolls, the required profile is obtained. This process contains other processes like template making, profiling of grinding wheel, profiling of rolls and at last nitriding process for rolls. First of all, the profile drawing, which is required, is drawn on brass plate having 2 mm thickness for making templates having its dimensions five times actual. With the help of jig saw machine, the drawing on brass plate is cut. This cut part of brass plate is called templates and the process is called template making. After the template making process, the grinding wheel is loaded on the cylindrical grinding machine and the template is fixed on diaform machine template bed which is connected with grinding machine. Then the tracer tool, on diaform machine, is moved on the periphery of template and with the help of universal diamond dresser, fitted on the machine bed, the grinding wheel is dressed till diamond stops touching the wheel. This process is repeated till the full wheel is dressed in respect to template. This process is called profiling of grinding wheel. Rolls are cut from H-13 bars of required diameter. On the lathe machine, machining of is started as per the dimensions of the drawing, which is in the shape 9

of the rough profiled roll but it is not be perfect as per the drawing. It has shape very near to profile drawing. This rough profiled roll is then mounted on the mandrel of grinding machine & with the help of grinding wheel which have been profiled, grinds the roll. Afterward for the hardening purpose, nitriding has been done for rolls Nitriding: Alloying elements in steels such as aluminium, chromium, vanadium and molybdenum would form very hard nitrides when they come contact with nitrogen. This is made use of in the process of nitriding where alloy steels are case hardened without any quenching process. The nitriding temperatures are in the range of 500oC to 575oC. The steels which are already quenched and tempered are put in a sealed container with ammonia gas and then heated to the 8 to 40 hrs for getting necessary case depths. The nitrogen forms complex nitrides with the alloying elements, whose depth depends on nitriding time. Because of the lower temperatures employed in nitriding, there are less possibilities of distortion and deformation than any other case hardening process. Also this process increases the wear resistance and fatigue life greatly. Further, no finish machining is required. Now after nitriding process rolls are ready for rolling process on mill. 3.1.2

Working process of rolling mill The process on mill is started with loading of raw material coil on uncoiler. At the time of loading raw material, first of all, the uncoiler has been made horizontal. After loading it has been made vertical position. The coil end is pulled up to straightening machine by the chain of the bar gripper on the winch drum, provided on the straightening machine. With the help of portable hydraulic bar straightener, the coil end has been made temporarily straight and has been fed to online straightening unit. All vertical and horizontal rolls of online straightening unit have been set for smooth feeding of coil in to it. Afterward the coil, which is

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now converted into rod, has been fed to further line equipments like descaler, brusher, healing element, etc. The heating groups have been switched on and its current is increased slowly in steps for all the three zones, at the same time the speed of the bar has been increased slowly till the bar gets red hot.

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When the rolls, after nitriding process, get cooled, have been sent to mill stands. The top and bottom assemblies are made fix in all four mill stands. The gap between top and bottom assemblies has been kept different in all mill stands. The gap is in decreasing order in subsequence mill stand. At the exit of each mill stand, the out coming section is measured and then it is passed to next mill stand.

As soon as the rolling gets set for o.k., with the help of shear unit, the sample bar of 1 m length is cut and quenched in water. The quenched sample is measured as per the final profile dimension and if any minor deviation is observed then it is corrected on the mill. Then the slice about 10 mm thickness is cut from sample and then on profile projector, the sample projection is compared by matching it with 10 times drawing of required profile.

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The cutting profiles of same length, which are cut by shear, are pushed to cooling bed. When the profile is cut on cooling bed, with the help of pusher blade the profile is removed from cooling bed. Then the whole bunch of profiles is sent for dispatch.

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CHAPTER–4

4.1

APPLICATIONS

The profile mill provides a variety of profiles like rings for truck wheels, nose bars for textile machines, pole shoe for automotive starters, grouser tips for earth moving vehicles, and others for sickles, computer peripherals, turbine blades, cutting tools, taper washers, ring gears, gear rings, etc. Its range finds wide application in a variety of sectors such as the electronic, mechanical, automobile and electrical industries, etc. The list is end less and growing fast. Furthermore, we can design any type of complicated profile shape to suit any specified requirement. In different industries or sectors, which type of complicated profile shapes are used and in which manner and how its manufacturing differs from conventional processes are described as follow:  Agriculture sector •

Sickles

•

Coffee Choppers

The manufacture of hot rolled sections for various agricultural implements such as Sickles & Coffee Choppers. Sickles are used for harvesting as well as weeding 14

or grass cutting operation & have conventionally been manufactured by the village smiths.

Sickles

The sickles that are hand forged by the village smiths have following disadvantages: •

No guarantee in the quality of steel as most of the time it is made from scrap.

•

Sickles made by hand forging are imbalanced due to non-uniformity of the

section that leads to non-uniform moment of inertia. This leads to uneven wearing of the sickle blade as well as more fatigue to those using such sickles. On account of the above reason, the sickle blade needs re-sharpening very

•

often. •

Hand forged sickles cannot be manufactured on a mass production basis to

cater to huge requirements. Sickles made from hot rolled section manufactured by us have following advantages: •

The hot rolled sections are supplied in taper condition that avoids the

necessity to forge & form. The manufacturing process does not involve forging operation by simple press working & bending. •

We offer these sections in a specific medium carbon grade that can be

properly heat-treated to give long life to the sickles.

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Due to a uniformly produced taper section, the sickle blade has an uniform

•

moment of inertia that reduces the fatigue while using such sickles and at the same time makes the sickle self sharpening. Sickles made from such hot rolled taper sections can be produced on a mass

•

production basis. Various export requirements for sickles clearly indicate use of hot rolled

•

section instead of hand forged one. When produced on a mass production basis, the cost per sickle can be

•

considerably brought down. Similarly the coffee chopper (tool used for cutting coffee plants) produced from a hot rolled section also offer the same advantages to its users. Automotive industries

 •

Door Hinges

•

Pole Shoes

•

Lock Rings / Flanges / Side Rings / Advance Bands

•

Flywheel Ring Gears

•

Serrated Angles

•

Special T

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car door hinges

car door hinges

starter motor

ring gear

The Profiles mill has an expertise in manufacturing hot rolled steel sections for various automotive applications such as: •

Door hinges for cars,

•

Pole shoe sections for starter motors & dynamos,

•

Rectangular & trapezoidal sections for flywheel ring gears / starter ring gears,

sections for lock rings / side rings / flanges / advance bands for wheel rims of trucks, buses & forklifts •

Serrated angles for steps of buses & trains,

•

Special T sections for pass-way interconnection of buses,



Construction industries •

Ornamental Grills

•

Hand Railings

•

Gratings

•

T for joining chequered plate

•

Serrated T's

•

Chamfers

•

Half Ovals

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Rallings

Grills

Rallings

The profile mill can manufacture hot rolled sections for various architectural applications such as ornamental grills, hand railings, gratings, T sections for joining chequered plates, serrated Ts for staircases etc. Use of such sections for grills, railings & gratings provide an edge over the conventional flats or squares that are used for fabricating these items. In the construction industry, concrete has been used effectively for centuries for all types of buildings and conditions. Buildings are being built at site using concrete structures such as columns & beams and recently many builders to drastically reduce the total construction time have started using pre-cast structures. The pre-cast structures are made off the site by using suitable molds. The profiles division manufactures two types of hot rolled sections that are used in these pre-cast molds. One of the sections is an isosceles triangle that is available in different sizes and is called as chamfer. These chamfers are fitted into the corners of the molds of the pre-cast structures so as to obtain a chamfered edge along the length of the pre-cast column or beam. On account of such chamfered edges (no corner), the question of corner breakage does not arise. Another section that is used in the pre-cast molds is called as a half oval section. This section that is used to obtain flutes on decorative pillars, is available in a standard length of 4 meters, in various widths and sizes. 

Defense sector 18

• Gun Barrel

The profile mill has the capability to manufacture various intricate sections that can be used for manufacturing various ammunition parts such as barrels of guns and pistols. The barrel sections can be supplied as per specifications & drawings. The basic hot rolled barrel section can be further drilled / machined to make the final barrel of a handgun or a pistol. Near net shape sections for other ammunition parts such as triggers can also be supplied that will require minimum machining to get the final shape.

Cutting Tools sector

 •

Wood Chisel. Paring Tools, Rasp & Planer

•

Engineers' Steel Files & Rasps

•

Hot rolled preshapes for Clicking knives

Wood chisel

Engineers steel files

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Hot rolled sections are supplied for various cutting tool applications such as cutting tool shanks, chisels, rasps, & planers for wood crafting and sections for engineers steel files & rasps. Earth Moving vehicle industries

 •

Grouser Bars / Lug Bars for rebuilding track shoes

Earthmoving equipment such as Dozers and Excavators plays an important role in the mining and construction industry. These equipment have tracked chains for moving into the difficult terrains such as sandy deserts, marshy lands, rocky mines, ice and many others. Tracked vehicles are also used in the defense sector as warfare tanks. The traction chains of these vehicles are called as track chains or grouser chains. These chains are made of number of track shoes or plates or grouser shoes or plates that form part of the undercarriage. These undercarriages are directly exposed to the terrain and therefore get worn out. Depending upon the terrain, these chains have a discard life ranging from 2000 to 4000 hours of operation.

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The replacement of worn out grouser chains is a very costly & painful affair, as the whole chain has to be discarded mostly on account of the wearing of the shoe tips and not the whole plate. In order to avoid such a costly changeover, people have developed various methods of re-furbishing the worn out chains that consist of rebuilding the grouser tip and the mounting holes. The re-furbished track chain can provide at-least 50% life of the new one that too at a nominal cost. The profiles mill can manufacture hot rolled grouser bars or tips suitable for various models and make of dozers & excavators in special steel grade so as to ensure better weld ability, harden ability and life of rebuilt shoes. The grouser bar profile is designed to match the original worn out grousers and the 45-degree chamfer at the bottom is provided to facilitate proper welding on the worn out grouser. These bars are available in various cross sections suitable for various dozer & excavator models in 3 to 5.8 meter lengths, which can be cut to the required length as per the width of the grouser shoe. For builders & contractors who have a fleet of dozers & excavators and whose track machines are operating with worn out grousers, causing loss in traction, time and increased fuel bills, we have our grouser bars to offer to restore the tracked shoes. It's an easy job that any welder can do and is the quickest and most economical means of rebuilding grouser/track shoes. 

Horse shoe

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Tamed horses have traditionally being using metallic shoes to protect their hoofs from injury due to exposure to hard rocky terrains or the modern roads. Conventionally, horse shoes are manufactured by village smiths by hand forging of steel bars. This process of manufacturing horse shoes is very tedious and left to the skill of the smith. In today's modern day life where horses are used more for races than for transportation, the shoe changing is very frequent and the requirement is very large. It is therefore difficult for the village smiths to cater to such a huge demand and this leads to the development of a modern process for manufacturing of horseshoes on a mass production basis. To cater to the requirements of such modern horseshoe manufacturers, the profiles division has developed hot rolled sections of various shapes and sizes that are suitable for manufacturing horseshoes suitable for various terrains, geographic locations, climatic conditions and nature of work of the horses. 

Textile Machinery

The profile mill caters to the requirement of various textile machinery manufacturers by sections, supplying them custom made hot rolled sections, cold 22

drawn hot rolled sections, cold drawn sections and hot rolled pre-shapes for further cold drawing for textile machine parts such as: •

Nore bar/Apron bar for ring frame machines

•

Condenser support bar

•

Lappet rail

•

Balance weight

•

D bars

•

Rod weighing bars Miscellaneous



The profiles division can manufacture hot rolled steel sections for various other end users such as: •

Springs

•

Taper washers

•

Locks and Keys

•

Sliding rails for partitions

•

Gibson ring and retaining rings

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•

Retched Paul for pneumatic concrete breakers

•

D sections for two wheeler kicks/gear shifters

•

Unequal angles with square edges for tops of steel tables

•

Knife-edge & bearing sections for mechanical weighing machines

It can also manufacture hot rolled pre-shapes for further cold drawing or machining for various end products/applications such as: •

Retched Paul for pneumatic concrete breakers

•

Machine tool guide ways

•

Linear motion guide ways

•

Steam turbine blades

•

Gear shifting sliding keys

•

Bearing steel flats

•

Sections for sprays

•

Half round pipe casing used in oil exploration

4.2ADVANTAGES AND DISADVANTAGES Advantages

 •

Reduced scaling on account of electrical heating.

•

Better dimensional tolerances due to reduced scaling.

•

Consistency in dimensions due to continuous rolling.

•

Reduced material wastage on account of better tolerances.

•

Reduced cost of machining operations and saving in time.

Disadvantages

 •

Hollow profiles can not be manufactured. 24

•

The profiles of more than 50 mm width can not be rolled.

•

More care should be taken during whole operation, because whole process

is gone through at very high temperature. •

Primary cost is high.

•

Occupy large floor area.

•

Whole process would be done accurately, because small error in

dimension makes high material waste.

CONCLUSION Since any industry is a profit generating mechanism, the general attitude is to select the most economic method. In our case, if we want to make complicated sectional profile, then we will have to choose the Profile Hot Rolling Mill. Because, this operation with any other mill is not possible and if it is possible, it will take more time & also we will never find fine surface as with the help of the Profile mill. In other way, if we want either to make simple shaped sectional profile or to change dimension of plate or sheet, conventional rolling mill

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will be used. Because, for these types of operation less energy consumption is required.

BIBLIOGRAPHY 1) http://www.tataprofiles.com/ 2) http://www.falcispa.com/

3) Working Instruction manual of Profile department of Tata CRMSisodara 4) “Elements of Workshop Technology vol: 1 (Manufacturing processes)” by Hajra Choudhury.

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