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Internship ReportPEOPLES STEEL MILLS LIMITED

Prepared by:

Names

Roll Number

Dawood College of Engineering & TechnologyDegree Awarding Institute, Karachi.

DEPARTMENT OF METALLURGY & MATERIALS ENGINEERING (Final year students.)

Table of ContentsDedication Acknowledgments

Chapter#1 Chapter#2 Chapter#3 Chapter#4 Chapter#5 Chapter#6

Introduction Process Flow Diagram Melting Shop (M-Shop) Bar Rolling Mill (Q-Shop) Slab & Bloom Rolling Mill (N-Shop) Forging Shop (R1,R2 & R3 Shop)

Chapter#1

INTRODUCTION

Peoples Steel Mills Ltd, a world class alloy and special steel manufacturing plant located in Manghopir, Karachi Pakistan and spread over an area of 100 acres was set-up by the Government of Pakistan in 1975 with Japanese assistance. In order to keep pace with emerging technologies, the plant was upgraded in 1996 though a comprehensive balancing & modernization programs with the technical assistance of VAIS, INTECO and Bohler of Austria. The plant is now equipped with modern melting, refining, degassing, electro slag re-melting and necessary casting , rolling and forging facilities with an annual capacity of 70,000mt. Products quality is assured through modern material testing facilities and well trained staff The plant has the capability to produce steels according to all major international quality standards and to date has manufactured more than 300 steel grades. Peoples Steel enjoys the highest market share in the alloy and special steel market of Pakistan. A diversified base of more than 200 customers includes high profile illustrious end users in automotive, defense, machinery construction, special/high rise buildings, transportation and engineering sectors in Pakistan. Components manufactured from our steel are supplied by our customers to renowned European & Japanese automobile manufactures. In addition to manufacturing & supply of quality steels Peoples Steel is extending its expertise in the following fields:

Material Testing & Analyzing-Chemical, Mechanical, NDT, Metallographic, Failure Analysis. Industrial Project & Services-Plant Fabrication & Installation.Seamless Pipe ManufacturingPipe/Tubes up to 300mm diameter are expected to be available in near future.

Chapter#2

PROCESS FLOW

Chapter#3

ELECTRIC ARC FURNACE

The melting shop of PSM consists of following facilities: Electric arc furnace. Ladle furnaces Ladle Vacuum Degassing Unit. Electro Slag Re-melting furnace. Continuous Casting Machine. The brief processing and configuration of above processing unites is as follows:

3.0 Electric Arc Furnace:In PSM there are two EAF in M- shop. The basic purpose of EAF is to melt the Steel Scrape and provide oxidizing environment to remove phosphorous contents (Dephosphorization).The electric arc furnace operates as a batch melting process producing batches of molten steel known "heats".

3.0.1 Operation of an Electric Arc Furnace:The electric arc furnace operating cycle is called the tap-to-tap cycle and is made up of the following operations: Furnace charging; Melting; Basic slag formation; Tapping the steel; Killing of steel( Deoxidation). Refractory lining maintenance. i. Furnace Charging: The first step in the production of any heat is to select the grade of steel to be made. Usually a schedule is developed prior to each production shift. Thus the melter will know in advance the schedule for his shift. The scrap yard operator will prepare buckets of scrap according to the needs of the melter. Preparation of the charge bucket is an important operation, not only to ensure proper melt-in chemistry but also to ensure good melting conditions. The scrap must be layered in the bucket

Chapter#3

ELECTRIC ARC FURNACE

according to size and density to promote the rapid formation of a liquid pool of steel in the hearth while providing protection for the sidewalls and roof from electric arc radiation. Following is the classification of Steel Scrap used: Home Scrape/ Shop returns: Ferritic Stainless Steel

Maragin Steel Tool Steel Special alloy steel

Purchased Scrape: Heavy mill Scrap 1 & 2 Sheratted Scrape The total time of charging is 45min. In PSM Scrap yard there are 8 buckets of different size ranges. ii. Charge Melting: The EAF has evolved into a highly efficient melting apparatus and modern designs are focused on maximizing the melting capacity of the EAF. Melting is accomplished by supplying energy to the furnace interior. This energy can be electrical or chemical. Electrical energy is supplied via the graphite electrodes and is usually the largest contributor in melting operations. Initially, an intermediate voltage tap is selected until the electrodes bore into the scrap. Usually, light scrap is placed on top of the charge to accelerate bore-in. Approximately 15 % of the scrap is melted during the initial bore-in period. After a few minutes, the electrodes will have penetrated the scrap sufficiently so that a long arc (high voltage) tap can be used without fear of radiation damage to the roof. The long arc maximizes the transfer of power to the scrap and a liquid pool of metal will form in the furnace hearth At the start of melting the arc is erratic and unstable. Wide swings in current are observed accompanied by rapid movement of the electrodes. As the furnace atmosphere

Chapter#3

ELECTRIC ARC FURNACE

heats up the arc stabilizes and once the molten pool is formed, the arc becomes quite stable and the average power input increases. Chemical energy is be supplied via several sources including oxy-fuel burners and oxygen lances. Oxy-fuel burners burn natural gas using oxygen or a blend of oxygen and air. Heat is transferred to the scrap by flame radiation and convection by the hot products of combustion. Heat is transferred within the scrap by conduction. Large pieces of scrap take longer to melt into the bath than smaller pieces. In some operations, oxygen is injected via a consumable pipe lance to "cut" the scrap. The oxygen reacts with the hot scrap and burns iron to produce intense heat for cutting the scrap. Oxidation of C, P, Mn, Si, Al:Once a molten pool of steel is generated in the furnace, oxygen can be lanced directly into the bath. This oxygen will react with several components in the bath including, aluminum, silicon, manganese, phosphorus, carbon and iron. All of these reactions are exothermic (i.e. they generate heat) and supply additional energy to aid in the melting of the scrap. Oxidizing slag formation: The metallic oxides that are formed will end up in the slag. Once enough scrap has been melted to accommodate the second charge, the charging process is repeated. Once the final scrap charge is melted, the furnace sidewalls are exposed to intense radiation from the arc. As a result, the voltage must be reduced. Alternatively, creation of a foamy slag will allow the arc to be buried and will protect the furnace shell. In addition, a greater amount of energy will be retained in the slag and is transferred to the bath resulting in greater energy efficiency. Sampling and chemical analysis of the melt: Once the final scrap charge is fully melted, flat bath conditions are reached. At this point, a bath temperature and sample will be taken. The analysis of the bath chemistry will allow the melter to determine the amount of oxygen to be blown during refining. De-slagging: When sufficient amount of phosphrous has been oxidized and gone in to slag the slage is removed.

iii. Basic slag formation:Basic slag is then formed by addition of flux and blowing of oxygen. The purpose of this basic slage formation is that the furnace is taped at 17000C at this temperature

Chapter#3

ELECTRIC ARC FURNACE

P2O5 ,which has penetrated in to refractories and remaining in the melt, decomposes resulting in increase in percentage of Phosphorous. But due to the formation of basic slag this effect is prevented.

iv. Tapping the steel:When steel has got aimed( average of upper and lower limits) composition and temperature Steel is tapped in preheated ladles by tilting slowly at an angle of 450.

v. Killing of steel( Deoxidation):During the tapping the steel is killed by using deoxidizers. Which include Ferrosilicon, Ferromanganese, Ferrochrome, Aluminum & Silicomanganese. The addition of these oxidizing agents is based on the composition of melt and cost. The basic purpose of killing of steel is to maintain oxygen content from 100 ppm to 200 ppm.

3.0.2 Chemistry of process:At this stage excessive carbon, phosphorous, silicon and manganese oxidize. The process is similar to that in Basic Oxygen Furnace. Basic oxidizing slag composed of lime (CaO) and ion ore (FeO) is used during the oxidizing period. Gaseous oxygen is blown into the melt for additional oxidizing and to stabilize the arc. Iron oxide causes increase of Oxygen content in the molten steel according to the reaction: (square brackets [ ] - signify solution in steel, round brackets ( ) - in slag, curly brackets {} - in gas). (FeO) = [Fe] + [O] Oxygen dissolved in the melt oxidizes carbon, phosphorous, silicon and manganese: [C] [Si] [Mn] 2[P] + [O] + {O2} + 1/2{O2} + 5/2{O2} = {CO} = (SiO2) = (MnO) = (P2O5)

Carbon monoxide partially burns in the atmosphere:

Chapter#3{CO} + {O2}

ELECTRIC ARC FURNACE= {CO2}

The formed oxides are absorbed by the slag. CO bubbles floating up through the melt result in refining of the steel from non-metallic inclusions and hydrogen removal. Gaseous products CO and CO2 are removed by the exhausting system. Oxidizing potential of the atmosphere is characterized by the post-combustion ratio: {CO2}/({CO2}+{CO}). The oxidizing slag enriched with phosphorous and other oxides formed d