Mig Welding Vs Oxy.docx Aasiemnet 2.docx

Henrry Diaz Sevilla

UNIT 13: Welding Technology

MIG Welding

 Types of welding processes: 1. Manual: Metal active gas (MAG) welding, is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt and join. One of the most common types of arc welding is shielded metal arc welding (SMAW) it is also known as manual metal arc welding (MMA) or stick welding. Electric current is used to strike an arc between the base material and consumable electrode rod, which is made of filler material (typically steel) and is covered with a flux that protects the weld area from oxidation and contamination by producing carbon dioxide (CO2) gas during the welding process. The electrode core itself acts as filler material, making a separate filler unnecessary. 2. Automated: MIG/MAG welding is a semi-automatic process where the welding arc is formed between the material being welded and the welding wire fed through the welding gun. Furthermore, Automatic MIG welding machines are custom designed for each application and include single and dual-head design; multi-station designs; rotary head styles; and multiple torches. Single-head designs are ideal for lighter fabrication tasks while the dual-head design welding machines are better suited for industrial production or fabrication. Automatic MIG welders are custom designed for each application and include single and dual-head design; multi-station designs; rotary head styles; and multiple torches.  MIG Welding: Metal Inert Gas (MIG) is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal, which heats the workpiece metal, causing them to melt and join. A MIG is a lot easier to learn and makes a good, strong weld. A MIG welder with enough capacity and properly equipped can weld anything from thin sheet metal.  Advantages and disadvantages: One advantage of MIG Welding is that it has better weld pool visibility also in order to use this welding process is not needed to be skilled which anyone can use this processes however the person that is going to use this machine must know the basics and must have knowledge of health and safety, furthermore another advantage of using welding process is that is high in productivity which saves time moreover this process is clean and efficient because a shielding gas to protect the arc, there is very little loss of alloying elements as the metal transfers across the arc, also this processes is faster because the continuously fed wire keeps both hands free for MIG welding, which improves the welding speed, quality of the weld, and overall control, however an a disadvantage for this process is that is very expensive because the equipment used in this process is more complex which can be hard to get the equipment maybe a piece has to be shipped and extra cost can be charged, furthermore another disadvantage is that before welding a metal you must prepared which it takes a quiet long time to prepare, the metal must be free of rust or dirt in order to get a good weld and for the safety of the welder.

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Henrry Diaz Sevilla

UNIT 13: Welding Technology

Butt joints are used where high strength is demanded, they are reliable and can survive stress better than any other type of weld joint, in order to accomplish full stress value, the weld must have 100% penetration through the joint, which can be done by welding completely through from one side.

Corner joints are used to join two members located approximately at right angles to each other in the form of an L. The closed corner joint is used on lighter sheets when high strength is not required at the joint. In making the joint by oxyacetylene welding, the overlapping edge is melted down, and little or no filler metal is added, however as high strength is been demanded I will not use this type of welding joint.

 Research the welding properties for mild steel, and stainless steel, and justify which in is the best for welding: mild steel: the properties for mild steel is that the melting point is of 1600°C, furthermore, mild steel has more properties such as tough, ductile, malleable, good tensile strength, poor resistance to corrosion. Stainless steel: Stainless steels are picked due to their improved consumption protection, high temperature oxidation protection or their quality. The different sorts of stainless steel are distinguished and direction given on welding procedures and methods which can be utilized in manufacturing stainless steel parts without disabling the consumption, oxidation and mechanical properties of the material or bringing deserts into the weld  Preparation of metal for welding carbon steel: The best welds come from pure clean metal to metal contact, any foreign materials in the welding area can cause welding imperfections. Even brand new metal must be prepped before it can be welded because there is usually a coating put on new metal so it does not rust or oxidize during the shipping process. Furthermore, to start, the type of welding you are doing will determine how you prep the metal. Inherently MIG welding steel does not need the metal to be perfectly clean. On the other extreme, TIG welding aluminium requires contaminant free metal to create a strong clean weld.  storage of electrodes: it is stored in a box.  short circuit transfer mode for MIG welding: Short racing circuit circle carry-over is a transfer used when a lower potential drop is used for MIG welding. Short circuit transfer occurs when the conducting wire electric arc s and link the metal creating short circuit circuits. During this short circuit, the wire contacting the metal heats up and drips into the joint by creating a pool . Then another arc begins and the process keeps repeating many times a second. The easiest way to tell if the transfer is short circuit is by the auditory sensation . The sound greatly resembles, an ballock Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun hit an extremely hot frying pan. It is a very crisp and fast crackling sound. Typically short circuit transfer is used on thin metals or flat solid metals.

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Henrry Diaz Sevilla

UNIT 13: Welding Technology

 safe handling and storage of shielding gases: COSHH Control of substances Hazardous to health and BOC Collect ad replace bottles.

 power source/current: MIG welding unlike most other welding processes has one standard voltage type and polarity type. The voltage used is D/C direct current, much like the current in a car battery. Direct current flows in one direction, from the negative (-) to the positive (+). The polarity used is also standard and that is D/C electrode (+) positive. This means that the handle is the positive side of the circuit, or it may be said, the electricity flows from the metal in to the welding handle.  welding stainless nickel alloys: Stainless steels are chosen because of their enhanced corrosion resistance, high temperature oxidation resistance or their strength. The various types of stainless steel are identified and guidance given on welding processes and techniques which can be employed in fabricating stainless steel components without impairing the corrosion, oxidation and mechanical properties of the material or introducing defects into the weld.  power source/voltage HAZ (heat affected zone when welding nickel & nickel alloys, and stanilees steel) (use the benefit of using filler rod electrode: these steels are alloyed with chromium and because of their low carbon content the structure is almost completely ferritic. They are magnetic and though easier to weld than the martensitic group because they are not hardenable to any extent by heat treatment they suffer from grain growth and embrittlement at temperatures above 900C and form of intergranular corrosion in the HAZ.  HAZ (heat affected zone when welding steel): The heat-affected zone (HAZ) is the area of base material, either a metal or a thermoplastic, which is not melted and has had its microstructure and properties altered by welding or heat intensive cutting operations. ... Alternatively, a low diffusivity leads to slower cooling and a larger HAZ

Oxy-Acetylene Welding

 Types of welding: 1. Manual: Gas Welding is a welding process utilizing heat of the flame from a welding torch. The torch mixes a fuel gas with Oxygen in the proper ratio and flow rate providing combustion process at a required temperature. The hot flame fuses the edges of the welded parts, which are joined together forming a weld after Solidification. 2. Automatic: Oxyhydrogen Welding is a Gas Welding process using a combustion mixture of Hydrogen (H2) and oxygen (O2) for producing gas welding flame.  Oxy-Acetylene Welding: Oxyacetylene gas welding is commonly used to permanently join mild steel. A mixture of oxygen and acetylene, burns as an intense / focussed flame, at approximately 3,500 degrees centigrade. When the flame comes in contact with steel, it melts the surface forming a molten pool, allowing welding to take place. Oxyacetylene can also be used for brazing, bronze welding, forging / shaping metal and cutting. http://www.technologystudent.com/equip_flsh/acet1.html  Advantages and Disadvantages: One advantage of using Oxy-Acetelyne is that is easy to learn which gives the opportunity to people to use this process moreover this process is cheap, the equipment that is used in this process is cheap than must of other welding process e.g. MIG Welding, furthemore the equipment is more portable than most other types of welding rings moreover the equipment can also be used to ‘flame-cut’ large pieces which is versatile 3|Page

Henrry Diaz Sevilla

UNIT 13: Welding Technology

suitable for small objects and big objects, another advantge for this process is that is adaptable to many different jobs in welding positions, however there is disadvantages for this process, one of the disadvantages is that unsuitable for welding high alloy steel in harden conditions moreover fluxes are required for welding most material, moreover not all metals can be weld. http://www.acastronovo.com/ClassHtms/Weld01.htm  Consumables Equipment: fluxes is one of the consumables in the process of Oxy-acetelyne welding, this means that it describes the quantity which passes through a surface or substance  Equipment: The equipment used in the process are as follow; Fuel gas cylinder with pressure regulator; Oxygen cylinder with pressure regulator; Welding torch; Blue oxygen hose; Red fuel gas hose; Trolley for transportation of the gas cylinders.

I have used this table in order to help me to identify the voltage that’s been asked which is 230v, one of the reason is because it has a lot of information and is accurate.

I have used this table because shows the thickness of the workpiece which is 2.0 – 3.0, furthermore the table also shows the welding position which helps a lot more over the table shows the wire speed adjustment.

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Henrry Diaz Sevilla

UNIT 13: Welding Technology

This diagram shows us a MIG Welding machine which is been label with the letters A,B,C which in the table that I have talked before we can also see this letters which this helps to minimize any mistakes that can be made when welding furthermore this is also useful because you can adjust it to the accurate sizes.

Tee joints are used to weld two plates or sections whose surfaces are located approximately 90° to each other at the joint. This type of welding joint is perfect because it has full strength if is been weld properly which is stronger than other welding joint, moreover I will be using this type of welding joint.

I have used this table to help me to identify what type of gas supply I need in MIG Welding machine, this table is very specific because it tells you what kind of gas supply need in different types of materials and as am going to use Mild Steel I would be using Carbon Dioxide (CO2).

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Henrry Diaz Sevilla

UNIT 13: Welding Technology

Health & Safety for both types of welding: 

You must wear protective clothes at all times when welding- gauntlet gloves designed for use in welding, apron, and protective shoes. Button shirt collar and pocket flaps, and wear cuffless trousers to avoid entry of sparks and slag. You must wear a helmet or protective goggles in order to prevent radiant energy, furthermore make sure you don’t wear any jewellery or headphones when welding to prevent any problems moreover wear gloves to prevent major burns in your hand due to the piece of metal will be hot, also make sure you always check for full free air circulation around in order to prevent inhaling the gases that the MIG welding can release, furthermore you must check that the pressure regulator and gauges are working correctly also remove all flammable materials that’s around however a extinguisher must be close to you in case of a fire the correct extinguisher in case of a fire are ‘dry powder, CO2 or BCF and in case of an emergency a first aid staff member qualified in first aid should be supervising around the workpiece.

What it should not been done when welding: 

One of the things that you should never do when welding is not to remove any of the panels unless the machine is disconnected from the supply also you should not try to repair any mechanical problem unless you are qualified technician, when using the MIG welding machine you should make sure you use the right gas and not use any unknown gas that can be a risk for you and others moreover you should not point with the MIG flame to anyone because it can prevent major burns.

The type of joint I will be using for the two pieces of metal. This is the type of joint I would be using to join the two pieces of metal, which it has the shape of an L. I think this type of welding joint is the best one to join the two pieces of metal because it has more strength than other types and because is more easy to weld and is fast.

Conclusion. The best way to weld this two pieces of metal (20mm x 90mm x3mm) mild steel is by using the MIG welding, this is because the area of the flame is smaller than Oxy-Acetylene which by having a small are of flame will allow me to work more easily and more accurate than Oxy-Acetylene, furthermore in order to weld this successfully I would be using the L welding joint which it has more strength and is more easy to work on with the MIG welding machine, in addition the advantage of using the MIG weld is that you don’t need to wear any explosion safety which this would make the student more comfortable and more secure however using the Oxy-Acetylene is dangerous because you must use gas which this is a high risk in case of an incident due that can explode and cause injuries to other students that are around whereas the MIG welding machine doesn’t use any type of gas and is not dangerous to use.

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Henrry Diaz Sevilla

UNIT 13: Welding Technology

Assignment 2

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Ferrous non alloyed (steel): Steel is made by adding iron to carbon which hardens the iron. Engineering steel becomes even tougher as other elements like chromium and nickel are introduced. Steel is made by heating and melting iron ore in furnaces. The steel can is tapped from the furnaces and poured into moulds to form steel bars. Steel is widely used in the construction and manufacturing industries. Ferrous metals have a high carbon content which generally makes them vulnerable to rust when exposed to moisture. There are two exceptions to this rule: wrought iron resists rust due to its purity and stainless steel is protected from rust by the presence of chromium.  Alloyed (stainless): Stainless steels are steels possessing high corrosion resistance due to the presence of substantial amount of chromium. Furthermore the properties for stainless are; strength, hardness, toughness, wear resistance, corrosion resistance, hardenability, and hot hardness. To achieve some of these improved properties the metal may require heat treating.  Non-ferrous (aluminium): Nonferrous metals are specified for structural applications requiring reduced weight, higher strength, nonmagnetic properties, higher melting points, or resistance to chemical and atmospheric corrosion. They are also specified for electrical and electronic applications. Aluminium is a metal with a much lower density than iron, making it a vital material in applications that need strength without weight, such as the aerospace industry. It is corrosion resistant because aluminium, like stainless steel, reacts to oxidization by creating a metal oxide shell that protects it. Aluminium also has a lower melting point than many of the steels or irons it might replace, which makes it easier to cast than steel, needing less oversight for complex forms.  TIG & Titanium welding: TIG welding is an arc welding process that uses a non-consumable tungsten electrode to produce the weld. The weld area and electrode is protected from oxidation or other atmospheric contamination by an inert shielding gas (argon or helium), and a filler metal is normally used, though some welds, known as autogenous welds, do not require it. A constant-current welding power supply produces electrical energy, which is conducted across the arc through a column of highly ionized gas and metal vapors known as a plasma. Gas tungsten arc welding is most commonly used to weld stainless steel and nonferrous materials, such as aluminium and magnesium, but it can be applied to nearly all metals, with a notable exception being zinc and its alloys. Its applications involving carbon steels are limited not because of process restrictions, but because of the existence of more economical steel welding techniques, such as gas metal arc welding and shielded metal arc welding. For each: Ferrous non alloyed (Steel), alloyed (Stainless) and a non-ferrous (aluminium). You should consider changes in properties, the effects of heat input (Melting Temperature) and cooling rates (Thermal Conductivity).  Changes in properties temperature non-alloyed (steel): Low temperatures can adversely affect the tensile toughness of many commonly-used engineering materials. Tensile toughness is a measure of a material’s brittleness or ductility; it is often estimated by calculating the area beneath the stress-strain curve. Ductile materials absorb significant amounts of impact energy before fracturing, resulting in tell-tale deformations. Brittle materials, on the other hand, tend to shatter on impact. Furthermore, the electrical, magnetic and structural properties of metals can be changed through heat. As the applications of metal are varied, different environments prioritize different qualities. For example, in engineering applications, toughness is desired; in electrical applications, low electrical resistivity is important. Electrical resistance: Electrical resistance is the measure of how strongly the metal impedes the passage of electrical current. As electrons pass through the metal, they scatter 7|Page

Henrry Diaz Sevilla

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UNIT 13: Welding Technology

as they collide with the metallic structure. When the metal is heated, the electrons absorb more energy and move faster. This leads to more scattering, thus increasing the amount of resistance. Structure: Metals are comprised of a symmetrical structure of atoms known as an allotrope. Heating the metal will displace atoms from their position and the displaced atoms form a new structure. Moreover Heat treatment is a process designed to alter the properties of the metal to better suit its intended use. The main types of heat treatment are annealing, normalising, hardening and tempering. Steel is just the element iron that has been processed to control the amount of carbon. Iron, out of the ground, melts at around 1510 degrees C (2750°F). Steel often melts at around 1370 degrees C (2500°F). http://www.totalmateria.com/page.aspx?ID=CheckArticle&site=kts&NM=48= Changes in properties at high and low temperatures (stainless): Stainless steels have good strength and good resistance to corrosion and oxidation at elevated temperatures. Stainless steels are used at temperatures up to 1700° F for 304 and 316 and up to 2000 F for the high temperature stainless grade 309(S) and up to 2100° F for 310(S). Stainless steel is used extensively in heat exchangers, super-heaters, boilers, feed water heaters, valves and main steam lines as well as aircraft and aerospace applications. With time and temperature, changes in metallurgical structure can be expected with any metal. In stainless steel, the changes can be softening, carbide precipitation, or embrittlement. Softening or loss of strength occurs in the 300 series (304, 316, etc.) stainless steels at about 1000° F and at about 900° F for the hardenable 400 (410, 420, 440) series and 800° F for the non-hardenable 400 (409, 430) series. Changes in properties at high and low temperatures (aluminium): Mechanical and physical properties of aluminium and aluminium alloys change when working temperature change from cryogenic (-195oC) to elevated temperatures (max. 400oC). These changes are not so intensive compared to another materials such as steel and others. Changes of properties of aluminium alloys with temperature depend on chemical composition and temper. Strength at temperatures above about 100 to 200 °C is improved mainly by solid-solution strengthening or second phase hardening. Another approach to improve the elevated-temperature performance of aluminium alloys has been the use of rapid solidification technology to produce powders or foils containing high supersaturations of elements such as iron or chromium that diffuse slowly in solid aluminium. Low-Temperature Properties. Aluminium alloys represent a very important class of structural metals for sub-zero-temperature applications and are used for structural parts for operation at temperatures as low as -270oC. Below zero, most aluminium alloys show little change in properties; yield and tensile strengths may increase; elongation may decrease slightly; impact strength remains approximately constant. Consequently, aluminium is useful material for many low-temperature applications.

Describe the HAZ in the different materials and what changes does it make to the properties and the microstructure of the metal. The heating -affected zone (HAZ) is the expanse of foot cloth, either a metal lick element or a thermoplastic, which is not melted and has had its microstructure and properties altered by welding or heat intensive 20 senses of cut operations. The heat from the welding mental process and subsequent re-cooling causes this change from the weld port to the final result of the sensitizing temperature in the cornerstone metal. The extent and magnitude of property change depends primarily on the base material, the weld filler metal, and the amount and concentration of heat input by the welding process During welding operations, the HAZ may orbit from small to large depending on the rate of heat comment . Theodore Dwight Welding mental summons with heights rates of heat input (i.e. fast heat ) have faster cooler rates compared to welding processes with depression rates of heat input (i.e. slow heating) and thus, have smaller HAZs. Conversely, a process with low rates of heat input will result in a larger HAZ. The size of a HAZ also growth as the speed of the welding process decreases. HAZ problems can be mitigated by performing a pre- and/or military post -weld heat 8|Page

Henrry Diaz Sevilla

UNIT 13: Welding Technology

treatment. Weld geometry also plays a role in the size of the HAZ. Because the HAZ experiences sufficient heat for a long enough period of time, the layer undergoes microstructure and property changes that differ from the parent metal. These property changes are usually undesirable and ultimately serve as the weakest part of the component. For example, the microstructural changes can lead to residual stresses, reduced material strength, increased brittleness, and decreased resistance to corrosion and/or cracking. As a result, many failures occur in the HAZ. During high-temperature cutting operations, the depth of the HAZ is associated with the cutting process, cutting speed, material properties, and material thickness. Similar to the results of welding processes, cutting processes that operate at high temperatures and slow speeds tend to lead to large HAZs. Furthermore, cutting processes that operate at high speeds tend to reduce the width of the HAZ.

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