Design And Fabrication Of Heat Treatment Furnace

ABSTRACT

Metallic materials consist of a microstructure of small crystals called “grains” or crystallites. The nature of the grains is one of the most effective factors that can determine the overall mechanical behavior 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 a metallic alloy, manipulating properties such as the hardness, strength, toughness, ductility, and elasticity.

Heat treatment furnaces are most widely used in the metallurgical industry for heat treatment of rolled products. Hot-rolled sheets are hardened, normalized, and tempered by passing through roller-hearth furnaces. Cold-rolled coils of steel strip are annealed in both drawing and bell furnaces. Drawing furnaces are used for the heat treatment of strips of carbon steel, stainless steel, and nonferrous metals and for the thermochemical treatment of electrical steel strip and preparation of the strip for the application of various coatings, such as zinc or aluminum. Standardized roller products are treated in roller-hearth and car-bottom furnaces. Pipes are treated in roller-hearth, fast-heating sectional, walking hearth, and car-bottom furnaces. Rods and coiled wire are treated in roller-hearth furnaces; bell furnaces are used for small batches. Hardening of wire in a lead bath, as well as galvanizing, is done in patenting furnaces. The heat treatment of railroad wheels and rims is accomplished in updraft furnaces, and sometimes in rotary-ring furnaces.

CHAPTER ONE

1.0                                                                  INTRODUCTION

Heat treating is the controlled heating and cooling of a material to achieve certain mechanical properties, such as hardness, strength, flexibility, and the reduction of residual stresses. Many heat treating processes require the precise control of temperature over the heating cycle. Heat treating is used extensively in metals production, and in the tempering and annealing of glass and ceramics products. Typically, the energy used for process heating accounts for 2% to 15% of the total production cost. Thermal efficiencies can range from over 90% for condensing boilers to under 10% for small, batch operated; high temperature furnaces like heat treat furnaces. In order to improve the energy efficiency and optimize the load throughput, it’s vital to have numerical modeling capability to accurately simulate the heat treatment processes. Currently there are plenty of commercial solutions for modeling the heat transfer and material properties for a single workpiece but none of them have a furnace model for simulating the thermal profile of the entire load. A comprehensive furnace model for different kinds of furnaces is crucial to accurately simulate the temperature of the load.

1.2                                      OBJECTIVES AND SCOPE OF STUDY

A furnace is a device used for high-temperature heating. The heat energy to fuel a furnace may be supplied directly by fuel combustion, by electricity such as the electric arc furnace, or through induction heating in induction furnaces. The objective of this work is to design an electric furnace.

1.3                                         SIGNIFICANCE OF THE PROJECT

This furnace is apply to the heat treatment which requires high temperature accuracy and high-grade atmosphere such as oxidization, reduction, degreasing, carbonization and baking for functional materials of the electrode material, the magnetic material and the fluorescent substance. Electricity, gas or oil is possible to use for the heat source. In case gas and oil, the running cost is one third compared with electricity and to cost down of the product.

1.4                                          LIMITATIONS OF THE PROJECT

Some of the limitations of the proposed work in this research are the availability of experimental data. The thermal gradient model is based on experimental data and is not possible to represent the gradients, unless a few experiments are conducted at several locations in the furnace. In the continuous furnaces its difficult and expensive to conduct such experiments. A datapack device that has a thermally insulated data recorder to withstand high temperatures over the duration of the process (typically several hours) is required to measure the temperature inside the furnace. Also the specifications of the datapack device itself become constraints while conducting experiments. The time allowed for the datapack to stay inside the furnace at a specified temperature has to be considered while designing the experiments. The control model needs to be modified to represent more advanced control techniques used in the industry like adaptive controllers. The heat transfer model inside the load is complex and currently in this research it was not studied.

1.5                                              PURPOSE OF THE PROJECT

The purpose of this work is to design a heating equipment used to provide heat for a process or can serve as reactor which provides heats of reaction. Furnace designs vary as to its function, heating duty, type of fuel and method of introducing combustion air.

1.6                                                 SCOPE OF THE PROJECT

The research methodology was based on both experimental work and theoretical developments including modeling different types of heat treat furnaces. More than 40 experimental validations through case studies using the current CHT model were conducted in 11 manufacturing locations to identify the specific problems in the current model. From the experimental data and knowledge from the experiments several improvements to the current furnace model are implemented and a new furnace model based on Knowledge Data Discovery (KDD) technique is also developed and validated.

A furnace tuning and calibration procedure is developed based on a virtual load design.

The main improvements include modeling thermal gradients present inside the furnace and accounting for heat loss arising due to the furnace door openings during loading and unloading of the furnaces. Also a virtual load is design procedure is developed for different loads and the reverse calculation for determining the furnace emissivity that accounts the wear and tear. Several constants are added to the current heat balance equation and they are determined using the experimental data and neural network. This KDD based model is used to optimize the load pattern using maximum entropy.

It is possible to accurately predict the thermal profile of the load inside a furnace using the improved furnace model. The new model enables us to improve the furnace efficiency by maximizing the load throughputs and save energy by accurately predicting the cycle time. The new model takes into account all the real time furnace parameters determined from the experimental data and accounts for some of the complex gradients and heating patterns that exist inside the furnace that is difficult to model.

1.7                                          ADVANTAGES OF THE PROJECT

1. Electric furnaces require far less maintenance than gas furnaces. This makes them the ideal choice for people who simply do not have the time or desire to maintain their heating system on a regular basis. This will also help to minimize the frequency of furnace repairs in the event that the required maintenance does go unattended for any period of time.
2. Electric furnaces are one of the least expensive furnaces to purchase. Additionally, since these furnaces do not make use of fuel combustion, these furnaces are also one of the least expensive furnaces to install. This makes them the ideal choice for people who are looking to replace their old furnace, but must do so on a very tight budget.
3. An electric furnace does not give off any dangerous emissions that could potentially cause harm to you or your family. This is because most emissions such as carbon monoxide which are typically created by the home heating process are the result of a leak in the fuel combustion chamber. Since electric furnaces do not require this type of chamber in order to heat your home, the risk of carbon monoxide poisoning due to a leak is absolutely nonexistent with this type of furnace.

1.8                                              PROBLEM OF THE PROJECT

1. An electric furnace costs more to run every month than a gas furnace. This is because while electricity is cheaper per unit than natural gas, electric furnaces require far more energy to heat your home than a natural gas furnace will require. This means that you can expect to pay more each and every month in order to keep your home at a comfortable temperature. Choosing to invest in a ultra high efficiency furnace can help you to offset this cost some. This is because high efficiency electric furnaces do not require as much energy as standard electric models.
2. An electric furnace may be more expensive to repair than a gas furnace. While these furnaces do not require repairs as often as other furnace models, when repairs are necessary they are often quite expensive. This is because the repair contractor who performs those repairs will need to have an electrician’s license in addition to their HVAC certification. This is the only way in which repairs can be safely performed on these appliances.
3. Electric furnaces are not very efficient at heating large spaces. This means that this option may not be available to you if you own a large home or office. In fact, people who try and utilize this appliance in a large space often find that they are unable to achieve a reasonable temperature in many areas of their house due to low air pressure in their vents. In order to achieve the desired temperature, people often have to set the thermostat much higher than the temperature they would actually like to achieve. In most cases, this simply means that you will be paying twice as much in order to achieve the same temperature as you would with a more powerful heating system.

1.8                                        PROJECT WORK ORGANIZATION

The various stages involved in the development of this project have been properly put into five chapters to enhance comprehensive and concise reading. In this project thesis, the project is organized sequentially as follows:

Chapter one of this work is on the introduction to this work. In this chapter, the background, significance, objective limitation and problem of this work were discussed.

Chapter two is on literature review of this work. In this chapter, all the literature pertaining to this work was reviewed.

Chapter three is on design methodology. In this chapter all the method involved during the design and construction were discussed.

Chapter four is on testing analysis. All testing that result accurate functionality was analyzed.

Chapter five is on conclusion, recommendation and references.