Welder World Blog

Archive for January, 2011

Welding is mostly used for the combination processes i.e. arc, resistance, laser, electron beam, stud and orbital welding.

Weld controllers are required to help the processes used by these tools. Welding machines also work as aid to welding power source. There are also wide-ranging system to cutting machine, torch, feeders, cables, robots and feeders. This article describes the purpose of arc welding in detail.

Arc welding methods and welding machines

For melting the metals at welding point, Arc welding is utilizing welding power supply to produce an electric arc between the base material and an electrode. Arc welding equipments can use either direct current or alternating current, and consumable or non-consumable electrodes. Shielding gas protects welding region using some inert or semi-inert gas and evaporate wadding material. The method of arc welding is broadly recognized for low capital and running costs.

MIG (Metal Inert Gas) welding and TIG welding are the two general specifications of Arc Welding. MIG is also acronym as MAG (metal active gas welding) and regarded as one of the mostly popular arc welding methods. MIG welding equipments uses various kinds of gas like pure carbon dioxide, argon gas and some time blend of both to complete the process.

TIG (Tungsten Inert Gas) Welding is another latest welding process.  This term stands for its utilization when shaping an arc in between the electrode and the item. Argon is use to inert gas portion in welding. TIG welding is slower compare to MIG and at the same time more expensive.

Arc welding has other methods like flux cored arc welding, gas metal arc welding, resistance seam welding, spot and shielded metal arc welding.

More welding measures serve by arc welding machines

Frictional welding is also a type of welding equipments. Examples of friction welding machines are hot plate welding, plastic welding, electron beam welding and Oxyfuel welding.

Despite the diversities in arc welding procedures, the purposes that are common is it all stops rust, serve varying actions and render water cooling uses. Of course heavy-duty equipment with engine driven generators is the best to fulfill these methods.

Cleveland, Ohio – Governor Ted Strickland today announced that 25 Ohio projects will receive more than million in grant awards funded through the American Recovery and Reinvestment Act’s State Energy Program.

“We are shaping Ohio’s future by strengthening our advanced energy economy today. Supporting the growing wind and solar industries creates jobs, creates energy and reduces costs for hard-working Ohioans,” Strickland said. “These Recovery Act-funded projects take the state another vital step toward our goal of making Ohio a world center for advanced energy.”

US Representatives Betty Sutton and Marcia Fudge, Ohio Department of Development Director Lisa Patt-McDaniel, the governor’s energy advisor Mark Shanahan, and other community leaders and elected officials joined the governor and Lincoln Electric Chairman and CEO John Stropki for today’s announcement in Cleveland. Lincoln Electric will receive a million grant for its wind turbine installation project.

These renewable energy awards are the first to be awarded from Ohio’s million State Energy Program, which was accepted by the U.S. Department of Energy on June 26th.

“We are excited to have this opportunity under Ohio’s energy program to demonstrate the value of wind energy by investing in our own installation,” Stropki said. “This project is a continuation of other Lincoln EHS programs and green initiatives currently under way in our manufacturing operations to improve our costs and protect our environment. Not only will the wind project provide long-term benefits by reducing our energy costs, it will also showcase the unique benefits that Lincoln products and welding solutions provide to wind tower manufacturers to improve their quality and lower their costs.”

Public and private entities will use the funds to install wind electric, solar electric and solar thermal technologies at businesses, schools, parks and other public locations throughout Ohio.

“Ohio is an impact state for advanced energy job creation potential,” Patt-McDaniel said. “Our state’s manufacturing strengths, logistics capabilities, skilled workforce, and competitive business environment make Ohio a major competitor in the growth of our nation’s new energy economy.”

Proposals for Deploying Renewable Energy: Wind and Solar component of the program were accepted beginning August 25, 2009. Projects submitted were selected through a competitive review process based on several criteria: project readiness and ability to be completed within 12 months, a matching investment of at least 50 percent, and direct economic impacts to create and retain jobs in Ohio.

Governor Strickland acknowledged that these awards would not have been possible without the support of members of Ohio’s Congressional delegation and President Barack Obama for the American Recovery and Reinvestment Act.

“The Wind and Solar Awards afford Cuyahoga County and the State of Ohio an opportunity to create jobs in a burgeoning field. By investing in energy, we will promote an industry of endless possibilities, create sustainable jobs, and retrain workers to enter this expanding ‘green’ workforce,” said Representative Fudge (OH-11).

“Today’s announcement of million for the solar energy project that will be installed in Akron Metro’s facility is great news,” Representative Sutton said. “It is projected that these solar panels could save up to 33 percent in energy costs. The projects announced today will strengthen Ohio’s advanced and renewable energy sectors, facilitate job creation and retention, and reduce energy costs along with greenhouse gas emissions.”

Awarded projects meet the federal goals of the Recovery Act’s State Energy Program to accelerate renewable energy development in Ohio by creating or preserving jobs and reduce energy usage and greenhouse gas emissions.

“Expanding the use of wind and solar energy across Ohio will create jobs in an expanding global market, positioning Ohio for growth for years to come,” Shanahan said. “Recovery Act resources are helping Ohio communities make their own renewable energy while accelerating market-driven job creation in our state.”

A list of award recipients follows below:

WIND PROJECTS

Archbold Area Local Schools (Fulton County) – 0,000 to install a 500 kW wind turbine and integrate the technology as a teaching tool in the classroom. Cuyahoga County Board of Commissioners (Cuyahoga County) – million to install a 600 kW wind turbine at the Cuyahoga County Fairgrounds in conjunction with a career and new energy training center. Green City Growers Cooperative (Cuyahoga County) – million to install a 1.5 MW wind turbine to power a 5.35 acre greenhouse and a 40,000 square-foot facility that will process fresh produce for Northeast Ohio. Huron-Wind LLC and City of Huron (Erie County) – 0,500 to install a 100 kW wind turbine. Kenston Local School District (Geauga County) – 0,500 to install a 600 kW wind turbine and integrate the technology as a teaching tool in the classroom. Lincoln Electric Company (Cuyahoga County) – million to install a 2.5 MW wind turbine at its manufacturing facility.

Pettisville Local Schools (Fulton County) – 0,000 to install a 500 kW wind turbine and integrate the technology as a teaching tool in the classroom.

Toledo Electric Joint Apprentice and Training Committee (Lucas County) – 0,000 to install a 100 kW wind turbine to serve as a training tool for 1,000 apprentices.

SOLAR ELECTRIC PROJECTS

Affinity Building Systems, Inc (Montgomery County) – 2,684 to install a 105 kW solar photovoltaic system. City of Cincinnati, Duke Energy Convention Center (Hamilton County) – 2,937 to install a 93 kW photovoltaic array rooftop system at the Duke Energy Convention Center.

City of Cincinnati Parks (Hamilton County) – 1,418 to install a total of 170 kW solar photovoltaic systems at 13 sites in the park system.

Forest City Residential Management Inc., Midtown Towers (Cuyahoga County) – million to install a 350 kW solar photovoltaic rooftop system on three of The Midtown Towers’ residential building complexes. Greater Cincinnati Water Works (Hamilton County) – 5,655 to install a 280 kW photovoltaic solar array rooftop system. Hull & Associates Inc, Bedford Office (Cuyahoga County) – 6,254 to install a 93 kW solar photovoltaic system at its office building in Northeast Ohio. Hull & Associates Inc, PNA Solar Project (Wood County) – 0,782 to install a 250 kW solar array project on Pilkington North America, Inc’s (PNA) Plant 21 site. IGS Energy (Franklin County) – 1,089 to install a 93 kW solar photovoltaic system on their corporate office building. Jewish Community Federation of Cleveland (Cuyahoga County) – 7,479 to install a 76 kW solar photovoltaic rooftop system at an office building built to LEED certification. METRO Regional Transit Authority (Summit County) – million to install a 488 kW solar photovoltaic rooftop system located on its central bus barn. Ohio Department of Mental Health (ODMH), Summit Facility (Hamilton County) – 2,932 to install a 232.65 kW solar photovoltaic rooftop system. Solar Vision LLC, Athens City Community Center (Athens County) – 1,637 to install a 220 kW photovoltaic solar array system on four carport structures in the parking lot of the Athens City Community Center. Solar Vision LLC, Bexley Police (Franklin County) – 5,328 to install a 117 kW photovoltaic array system on four new carport structures in the parking lot. Toledo Museum of Art (Lucas County) – 2,264 to install a 100 kW solar rooftop system. Toledo Zoo (Lucas County) – 6,837 to install a 103 kW solar system.

SOLAR THERMAL PROJECTS

Great Lakes Brewing Company (Cuyahoga County) – 0,082 to install two hot water heating systems. Parkway Local Schools (Mercer County) – ,080 to install a solar thermal system.

Step inside the partnership between Ohio State and the Edison Welding Institute as these specialized emerging professionals design the products and create the jobs of tomorrow.
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Carpenters specialise in the working and constructing of wooden and similar materials on a range of projects, with their project suitability spanning across major construction projects to home renovations and everywhere in-between. Carpenters are highly requested from corporate construction projects such as office or public buildings to residential projects or small scale renovations, withthe construction projects alone asking carpenters to perform jobs ranging from the framework to the roofing to flooring. Naturally, aside from the construction industry carpenters also receive a large majority of jobs from residential projects. The sheer range of carpentry projects that are available has resulted in several branches of carpenters within the industry.

Styles of carpenters

The specialised field of carpenters, while broadly similar across the industry at the beginning of a carpenters career, has different avenues that carpenters can focus on throughout their career. What this means is that a carpenter will pursue kinds of jobs that asks for and develop the various skills needed for different levels of carpentry. Largely, there are five kinds of sorts of carpenters that centre on different categories of carpentry jobs although there are two that make up the greater part of the carpentry industry. That is Rough carpenters and Finish carpenters.

Rough Carpenters

Rough carpenters are those that operate on the various jobs linked with structural construction work, framing and even roofing. The jobs linked with this speciality of carpentry include:

Rough Carpenter Jobs

* Pre-construction work – sizing, scaffolding, bracing, and formworks preparation

* Making frames, partitions, floor construction, walls, insulation, roof trusses and construction

* Understanding construction blueprints, measurement of materials required and distances, dimensions of structure which are all crucial for major construction projects

* Managing the sizing and cutting of various wood materials, knowing the different requirements of the different types of wood

* Understanding construction of both wood and metal structures, which is fundamental is the construct of building of frameworks

* Understand the the carpentry damage that can affect different types of wood, including any decay or rot

* Fabricate parts through woodworking and metalworking machines, dig post holes, and construct support structures

When selecting deciding on which rough carpenter to sign up for a project, simply look to their experience in the kind of carpentry that you are after to determine if they are suitable. Furthermore, a prospective customer should request examples of any earlier jobs.

Finish Carpenter Jobs

Finish carpenters are those that work specifically with the finished product of a project. The amount of jobs that this can relate to is diverse including:

* Decking
* Roofing
* Interior trimming
* Siding
* Drywall detailing
* Remodelling
* Intricate woodwork projects

Finish carpenters are commonly more expensive to employ but they commonly have high experience and are decidedly skilled, which means that for a little extra they will provide a clean and artistic finish to a wooden project.

Finish carpenters require to have a sharp eye when creating the style, joints and overall look of a project or room which means the choice of who to hire can be crucial for a successful project or renovation central which means that the selection of who to hire for the job is essential for the overall look of the finished product. Begin by assessing their previous projects, price quotes and years of experience in order to warrant that you are hiring someone that is capable.

Other carpenters jobs include:

* Cabinet Makers – furniture and interior wooden cabinets
* Trim carpentry – window, ceiling trimmings or mouldings
* Ship carpentry – shipbuilding and nautical woodwork projects

Carpenters and the industry of carpentry are extensive and diverse with various branches and avenues that individual carpenters can take on, suiting the scope of carpentry projects that are demanded. Carpenters services are in major demand with the construction, maintenance and manufacturing industries all requiring the services of carpenters.

An excellent career option for many people is to become a welding inspector. A welding inspector is an individual who inspects completed welding work and reviews welding plans. Becoming a welding inspector requires years of welding experience, which can be difficult to obtain without first going to welding school. One of the best ways to start your welding inspection career is to attend a Texas welding school upon graduation from high school.

While attending a Texas welding school, you will learn all about different fields within welding. You will also learn about all of the different types of metals, welding techniques, and all of the different welding machines. Furthermore, you will learn about current welding laws and codes that must be followed. As a welding inspector, you will need to be well versed in the current laws and codes in the location where you will be a licensed inspector.

What to Expect When You Enroll in Welding Inspector Training

When you start taking classes at a welding school to become a welding inspector, you will have to learn the basics first. This means learning how to weld properly and how to weld using various welding techniques. After that you will begin your welding inspector courses. These will teach you about inspecting welds and how to safely determine the strength of a weld. After completing your school work, the next step in becoming a welding inspector is to get a job. The best place to find a job is working for either a union or through a privatized construction company. After completing a few years of experience working as a welder, you may now be prepared to sit for the welding examination.

Prior to taking the CAWI (Certified Associated Welding Inspector) exam, be sure to follow up with your state to ensure you have all necessary qualifications. If available, you should take any seminars which are geared to helping individuals pass the CAWI examination. Once you have completed the CAWI examination, you are qualified to be a certified welding inspector.

Related Welding Inspection Jobs Articles

If you’re in the need of welding equipment but on a tight budget, you will be pleased to know that oftentimes you can get the right tools to get the job done at a fraction of the cost. Many welders who want to start their own welding shop or business are the ones usually interested in buying pre-owned welding equipment.

Purchasing used welding tools is one way to practically stock your arsenal with equipment from the best manufacturers in the industry. Quality new tools are always expensive, so opting for used tools is your perfect bet for inexpensive quality if you know where to look.

There are many factors that need to be considered in purchasing previously-owned welding equipment and other tools. Here are some tips to help you get the best deals in second-hand welding machine:

Before anything else, you need to decide on the brand of the equipment you want to use. It’s always better to choose the reputable manufacturers such as Miller, Lincoln and Hobart. A dynamic, multi-purpose machine would be a fantastic choice because it is capable of doing TIG, MIG, stick welding and other processes.

Cruise the second-hand equipment shops. Many stores have a section for welding equipment and other tools. Chances are, you’ll be able to find what you’re looking for at a very cheap price.

Skim the classified ads. While used welding tools might not be listed, you can still look for moving sales around your area. Call ahead if there’s a phone number provided in the advertisement and see what the seller has. Take note that nearly 500,000 employees in the USA work in factories that do welding jobs. This means that it’s not impossible to find used welding equipment around for sale.

Shop online! If you want to look for more options, visit the online auction shops like Ebay or classified ads sites such as Craigslist, where you will find tons of bargain listings. If you decide on buying the second-hand welding equipment listed in the internet, you should insist on seeing the actual photos of the equipment and inspect them beforehand.

Please remember that second hand welding equipment varies greatly in price. Some tools are much more expensive than the others. But whatever the price of a piece of welding equipment you choose, it is always essential to make sure you get the best value for your hard-earned money!

Born Again American www.bornagainamerican.org The Words to The Song Just a workin man without a job It got shipped off to China via Washington, DC And I know Im nothin special, there are plenty more like me Just the same I thought I knew the rules of the game I stood up for this country that I love I came back from the desert to a wife and kids to feed Im not sayin Uncle Sam should give me what I need My offer stands Ill pull my weight you give me half a chance I went up to a congressman and said to him you know Our government is letting people down He said hed need a lot of help to buck the status-quo I said there was a bunch of us around Im a Born Again American, conceived in Liberty My Bible and the Bill of Rights, my creeds equality Im a Born Again American, my country tis of me And everyone who shares the dream from sea to shining sea My brothers welding chassis at the plant Hes earning what our granddad did in 1948 While CEOs count bonuses behind the castle gates How can they see When all they care abouts the do re mi Its getting where theres nowhere left to turn Not since the crash of twenty-nine have things been so unfair So many of our citizens are living in despair The time has come To reaffirm that hopes not just for some The promise of Americas surrendering to greed The rule is just look out for number one But brace yourself cause some of us have sown a different seed A harvest of the spirit has begun Im a Born Again American conceived in liberty My Bible and …
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Tig welding tips for stainless steel welding. Copper is one of the best materials to use for a heat sink fixture for welding stainless steel. Less discoloration, less warping, and better looking tig welds can be made using a fixture made from copper. You can weld copper with silicon bronze, aluminum bronze, or pure copper tig welding wire.

Welding is one of the most resourceful activities in the world.  Defined as a fabrication process that is used to join materials, welding often requires the melting of a material before joining it to another through the use of heat.  The welding industry employs a large number of workers and, because it is a dangerous job, it requires specialized training and certification.

In addition to pre-employment training, welding also requires specific safety measures that must be followed by every worker.  The proper knowledge combined with today’s technology can reduce the likelihood of injuries related to welding.  However, the risks associated with any job can never be completely eliminated.  Because welding commonly involves exposure to extreme heat, there is a significant risk of burns.  In an effort to prevent this risk, welding professionals must wear protective clothing, including leather gloves and special long sleeve jackets.  The additional coverage will help to prevent the likelihood of flames coming into contact with the skin and thereby helps to prevent burns.  

Actual contact is not the only risk associated to welding.  In fact, the brightness of the welding process is often damaging to the worker’s eye.  A condition may develop as a result of the cornea becoming inflamed and/or the retina becoming burned after exposure to ultraviolet light.  In order to prevent this occurrence, welding professionals are required to wear a helmet and goggles with a darkened face plate.  A number of companies also manufacture helmets with the face plate built-in.  

Welding professionals are also often exposed to harmful gases and/or smoke.  In an effort to reduce the worker’s exposure to these potentially dangerous pollutants, proper ventilation must be provided.  Employers who offer welding positions are responsible for the care and safety of their workers and, as such, are required to uphold certain safety standards in maintaining a proper work environment.

In order to find work as a welding professional, interested candidates are usually required to attend classes for certification.  The length of time spent in this type of learning environment will vary depending on the position and required expertise of the welder.  In order to enroll in welding certification classes, candidates will likely be required to pay a small fee before signing up.  The certification process is not lengthy and classes typically last for several months.  After successful completion, the graduate is awarded with a welding certification.  At that time, he/she may apply for jobs in the industry that is related to their field of study.

Global NDE Guru , www.ndeguru.com – Our online multimedia Ultrasonic Testing- Level II, training is deigned to fulfill the requirements of ASNT SNT-TC-1A , CP -189, other equivalent standards and customer specific written practice for training and certification of NDE personnel. This method will give you in depth knowledge of ultrasonic shear wave theory, application on weld inspection, interpretation and evaluation of weld discontinuity etc. This course will give you 24 hours of credit for your certification in this method.

More Welding Certification Classes Articles

You will not find any other company other than Carhartt that provides as much protection as the protective clothing line from Carhartt. They design their work wear in such a way so as to provide maximum protection to workers like fitters and welders preventing them from receiving burns from sparks from a cutting torch or a welding machine. Besides, you also get good quality Carhartt coats and other kinds of protective clothing for other areas of work like sandblasting and painting.

The flame resistant clothing from Carhartt is first treated with chemicals that will self extinguish as soon as the starting point of the fire has been moved away. All Carhartt coats and other pieces of clothing meet the ASTM and OSHA standards and are still assembled in order to ensure that the clothes are not only long lasting but comfortable as well. Carhartt flame resistant clothing which is quilt lined should never be subjected to dry cleaning nor should one use any kind of softeners or bleach. Even though you might think that there is stiffness due to starch in the material it is in fact the chemicals used when treating the material, so the stiffness is best left alone.  Use very low heat to wash the clothes and the same applies for other clothes too whether they are unlined or twill lined.

A lot of companies need their employees to put on clothing that is reflective or has a high visibility. This kind of clothing is made from 3M Scotchlite Reflective Material. This special material passes all the requirements and specifications of the ANSVISEA 107-2004. You have a lot of clothes like t-shirts, sweatshirts, color enhanced shirts, head gear and rainwear coming under this group of Carhartt clothing. You must know how to care for your Carhartt coats and other items of clothing so they last longer but to ensure that their protective quality is retained they should be washed a maximum twenty five times.

The Carhartt clothing line includes flame resistant denim jeans which have 19” leg openings which makes it easy for you to cover your boots. These jeans also satisfy the NFPA70E code. Carhartt’s weatherware includes a waterproof jacket which comes with a lining that is breathable allowing the heat to go out while the material on the outside is water proof, the cuffs have storm flaps and it comes with a two-way zip. Such Carhartt coats or jackets are getting to be pretty popular  these days.

The Carhartt summer wear line includes clothes for men as well as for women whether it is shorts and t-shirts or gloves and blouses and they all fulfill the terms of Carhartt care and good quality. Then you have the Carhartt wet ware which includes t-shirts to manage the moisture in the atmosphere as well as the perspiration on the wearer’s body; they use material with an anti-odor property which is lightweight as well as long-lasting. Lastly, you have the Carhartt coats, jackets, thermal shirts and bottoms for their winter work dry line which will keep the wearer warm no matter how nasty the weather.

Major causes

Hydrogen embrittlement

Main article: Hydrogen embrittlement

Residual stresses

Main article: Residual stress

The magnitude of stress that can be formed from welding can be roughly calculated using:

ET

Where E is Young’s modulus, is the coefficient of thermal expansion, and T is the temperature change. For steel this calculates out to be approximately 3.5 GPa (510,000 psi).

Types

Cracks

Defects related to fracture.

Arc strike cracking

Arc strike cracking occurs when the arc is struck but the spot is not welded. This occurs because the spot is heated above the materials upper critical temperature and then essentially quenched. This forms martensite, which is brittle, and micro-cracks. Usually the arc is struck in the weld groove so this type of crack does not occur, but if the arc is struck outside of the weld groove then it must be welded over to prevent the cracking. If this is not an option then the arc spot can be postheated, i.e., the area is heated with an oxy-acetylene torch, and then allowed to cool slowly.

Cold cracking

Residual stresses can reduce the strength of the base material, and can lead to catastrophic failure through cold cracking, as in the case of several of the Liberty ships. Cold cracking is limited to steels, and is associated with the formation of martensite as the weld cools. The cracking occurs in the heat-affected zone of the base material. To reduce the amount of distortion and residual stresses, the amount of heat input should be limited, and the welding sequence used should not be from one end directly to the other, but rather in segments.

Cold cracking only occurs when all the following preconditions are met:[citation needed]

susceptible microstructure (e.g. martensite)

hydrogen present in the microstructure (hydrogen embrittlement)

service temperature environment (normal atmospheric pressure): -100 to +100 F

high restraint

Eliminating any one of these will eliminate this condition.

Crater crack

Crater cracks occur when a crater is not filled before the arc is broken. This causes the outer edges of the crater to cool more quickly than the crater, which creates sufficient stresses to form a crack. It may form a longitudinal or transverse crack or form multiple radial cracks.

Fusion-line crack

This section requires expansion.

Hat crack

Hat cracks get their name from the shape of the cross-section of the weld, because the weld flares out at the face of the weld. The crack starts at the fusion line and extends up through the weld. They are usually caused by too much voltage or not enough speed.

Hot cracking

Hot cracking, also known as solidification cracking, can occur with all metals, and happens in the fusion zone of a weld. To diminish the probability of this type of cracking, excess material restraint should be avoided, and a proper filler material should be utilized. Other causes include too high welding current, poor joint design that does not diffuse heat, impurities (such as sulfur and phosphorus), preheating, speed is too fast, and long arcs.

Underbead crack

An underbead crack, also known as a heat-affected zone (HAZ) crack, is a crack that forms a short distance away from the fusion line; it occurs in low alloy and high alloy steel. The exact causes of this type of crack are not completely understood, but it is known that dissolved hydrogen must be present. The other factor that affects this type of crack is internal stresses resulting from: unequal contraction between the base metal and the weld metal, restraint of the base metal, stresses from the formation of martensite, and stresses from the precipitation of hydrogen out of the metal.

Longitudinal crack

Longitudinal cracks run along the length of a weld bead. There are three types: check cracks, root cracks, and full centerline cracks. Check cracks are visible from the surface and extend partially into weld. They are usually caused by high shrinkage stresses, especially on final passes, or by a hot cracking mechanism. Root cracks start at the root and extent part way into the weld. They are the most common type of longitudinal crack because of the small size of the first weld bead. If this type of crack is not addresses then it will usually propagate into subsequent weld passes, which is how full centerline cracks (a crack from the root to the surface) usually form.

Reheat cracking

Reheat cracking is a type of cracking that occurs in HSLA steels, particularly chromium, molybdenum and vanadium steels, during postheating. It is caused by the poor creep ductility of the heat affected zone. Any existing defects or notches aggravate crack formation. Things that help prevent reheat cracking include heat treating first with a low temperature soak and then with a rapid heating to high temperatures, grinding or peening the weld toes, and using a two layer welding technique to refine the HAZ grain structure.

Root and toe cracks

This section requires expansion.

Transverse crack

This section requires expansion.

Distortion

Welding methods that involve the melting of metal at the site of the joint necessarily are prone to shrinkage as the heated metal cools. Shrinkage then introduces residual stresses and distortion. Distortion can pose a major problem, since the final product is not the desired shape. To alleviate certain types of distortion the workpieces can be offset so that after welding the product is the correct shape. The following pictures describe various types of welding distortion:

Transverse shrinkage

Angular distortion

Longitudinal shrinkage

Fillet distortion

Neutral axis distortion

Gas inclusion

Gas inclusions is a wide variety of defects that includes porosity, blow holes, and pipes (or wormholes). The underlying cause for gas inclusions is the entrapment of gas within the solidified weld. Gas formation can be from any of the following causes: high sulfur content in the workpiece or electrode, excessive moisture from the electrode or workpiece, too short of an arc, or wrong welding current or polarity.

Inclusions

There are two types of inclusions: linear inclusions and isolated inclusions. Linear inclusions occur when there is slag or flux in the weld. Slag forms from the use of a flux, which is why this type of defect usually occurs in welding processes that use flux, such as shielded metal arc welding, flux-cored arc welding, and submerged arc welding, but it can also occur in gas metal arc welding. This defect usually occurs in welds that require multiple passes and there is poor overlap between the welds. The poor overlap does not allow the slag from the previous weld to melt out and rise to the top of the new weld bead. It can also occur if the previous weld left and undercut or an uneven surface profile. To prevent slag inclusions the slag should be cleaned from the weld bead between passes via grinding, wire brushing, or chipping.

Isolated inclusions occur when rust or mill scale is present on the base metal.

Lack of fusion and incomplete penetration

Lack of fusion is the poor adhesion of the weld bead to the base metal; incomplete penetration is a weld bead that does not start at the root of the weld groove. Incomplete penetration forms channels and crevices in the root of the weld which can cause serious issues in pipes because corrosive substances can settle in these areas. These types of defects occur when the welding procedures are not adhered to; possible causes include the current setting, arc length, electrode angle, and electrode manipulation.

Lamellar tearing

Lamellar tearing is a type of welding defect that occurs in rolled steel plates. It has rarely been an issue since the 1970s because steel produced since then has less sulfur.

There is a combination of causes: non-metallic inclusions, too much hydrogen in the material, and shrinkage forces perpendicular to the face of the plates. The main factor among these reasons is the non-metal inclusions, of which the sulfur is the main problem. Lamellar tearing is no longer a problem anymore because sulfur levels are typical kept below 0.005%.

Some things that are done to overcome lamellar tearing are: reducing amount of sulfur in the material or adding alloying elements that control the shape of sulfide inclusions, such as rare earth elements, zirconium, or calcium. A more drastic option is change the workpieces to castings or forgings because this type of defect does not occur in those workpieces.

Undercut

Undercutting is when the weld reduces the cross-sectional thickness of the base metal, which reduces the strength of the weld and workpieces. One reason for this type of defect is excessive current, causing the edges of the joint to melt and drain into the weld; this leaves a drain-like impression along the length of the weld. Another reason is if a poor technique is used that does not deposit enough filler metal along the edges of the weld. A third reason is using an incorrect filler metal, because it will create greater temperature gradients between the center of the weld and the edges. Other causes include too small of an electrode angle, a dampened electrode, excessive arc length, and slow speed.

References

^ Matthews, Clifford (2001), ASME engineer’s data book, ASME Press, p. 211, ISBN 9780791801550, http://books.google.com/books?id=7nIqrfROowQC&pg=PA211. 

^ Bull, Steve (2000-03-16), Magnitude of stresses generated, University of Newcastle upon Tyne, archived from the original on 2009-12-06, http://www.webcitation.org/5lpLTHRZo, retrieved 2009-12-06. 

^ Rampaul 2003, pp. 207208.

^ a b Cary & Helzer 2005, pp. 404405.

^ a b c Raj, Jayakumar & Thavasimuthu 2002, p. 128.

^ Bull, Steve (2000-03-16), Factors promoting hot cracking, University of Newcastle upon Tyne, archived from the original on 2009-12-06, http://www.webcitation.org/5lpX2E1S7, retrieved 2009-12-06. 

^ a b Raj, Jayakumar & Thavasimuthu 2002, p. 126.

^ Rampaul 2003, p. 208.

^ Bull, Steve (2000-03-16), Reheat cracking, University of Newcastle upon Tyne, archived from the original on 2009-12-06, http://www.webcitation.org/5lpXkrGfA, retrieved 2009-12-06. 

^ Bull, Steve (2000-03-16), Reheat cracking, University of Newcastle upon Tyne, archived from the original on 2009-12-06, http://www.webcitation.org/5lpYdb66E, retrieved 2009-12-06. 

^ Weman 2003, pp. 78.

^ Bull, Steve (2000-03-16), Welding Faults and Defects, University of Newcastle upon Tyne, archived from the original on 2009-12-06, http://www.webcitation.org/5lpDLc6Iw, retrieved 2009-12-06. 

^ Defects/imperfections in welds – slag inclusions, archived from the original on 2009-12-05, http://www.webcitation.org/5lp4O9zyW, retrieved 2009-12-05. 

^ Bull, Steve (2000-03-16), Welding Faults and Defects, University of Newcastle upon Tyne, archived from the original on 2009-12-05, http://www.webcitation.org/5lnmtLCCy. 

^ Rampaul 2003, p. 216.

^ a b Bull, Steve (2000-03-16), Welding Faults and Defects, University of Newcastle upon Tyne, archived from the original on 2009-12-03, http://www.webcitation.org/5ll21lW3L. 

^ a b Still, J. R., Understanding Hydrogen Failures, http://www.aws.org/wj/jan04/still_feature.html, retrieved 2009-12-03. 

^ Ginzburg, Vladimir B.; Ballas, Robert (2000), Flat rolling fundamentals, CRC Press, p. 142, ISBN 9780824788940, http://books.google.com/books?id=NeKG76F4KWUC&pg=PA141. 

^ Rampaul 2003, pp. 211212.

Bibliography

Cary, Howard B.; Helzer, Scott C. (2005), Modern Welding Technology, Upper Saddle River, New Jersey: Pearson Education, ISBN 0-13-113029-3. 

Raj, Baldev; Jayakumar, T.; Thavasimuthu, M. (2002), Practical non-destructive testing (2nd ed.), Woodhead Publishing, ISBN 9781855736009, http://books.google.com/books?id=qXcCKsL2IMUC. 

Rampaul, Hoobasar (2003), Pipe welding procedures (2nd ed.), Industrial Press, ISBN 9780831131418, http://books.google.com/books?id=cie00sSLFqoC. 

Weman, Klas (2003), Welding processes handbook, New York, NY: CRC Press, ISBN 0-8493-1773-8. 

External links

Understanding Hydrogen Failures

Categories: WeldingHidden categories: All articles with unsourced statements | Articles with unsourced statements from December 2009 | Articles to be expanded from December 2009 | All articles to be expanded

Welding is a sculptural process where it deals with raw items such as metal and pipes Historical monuments, construction of building, bridges, ship building, automobile, aerospace, power plants, refineries and lots of manufacturing activities needs the process of welding and it is a part of it. The manufacturing industry came to know about the importance of welding service during 20th century and new welding equipment with latest welding technology were introduced later and requirement for welding supplies increased a lot. The welding industry should be equipped with modern tools such as welding electrodes, welding torches, welding consumables and welding guns and should follow the proper welding system with appropriate welding technology.

There are different types of welding process and each one has its own merits and demerits. Arc welding is a welding technique that uses a welding power supply and creates electric arc between electrode and base materials and Forge welding is a process that joins metal by heating them to high temperature. Tig welding uses tungsten electrode to produce the weld and it is the other name for gas tungsten metal arc welding and it is used to weld thin sections of stainless steel and non ferrous metals. Mig welding is an automatic arc welding process preferred for its versatility and speed and weld aluminum and non ferrous materials. Spot welding is a process in which metal surfaces are joined by the heat obtained from resistance of current flow. Gas welding is also called as oxy-fuel welding and use gases to weld and cut metals. Stick welding or shielded metal arc welding is a manual arc welding process that uses consumable electrodes. Plasma arc welding uses plasma gas and has narrow penetration with greater energy concentration.

Plasma arc cutting is an easy process if you follow these safety precautions. Do not touch any wet surface when operating the plasma cutter equipment and don’t use plasma cutters without any proper protection. Don’t remove the ground cable, which is attached with the work object and ensure that there is proper earth since it connects with high electric circuit. In welding, electrode is used to conduct current and it is of two types such as consumable one and a non consumable one. Shielded metal arc, gas metal arc, flux cored arc and submerged arc welding comes under the category of consumable electrode methods and tig welding and plasma arc welding are non consumable electrode methods

Apart from the welding products such as mig, tig, stick and submerged arc welding products, the other products such as wire feeders, spot welders, multi process units and water coolers comes under the welding products. Welding equipment is a heat generating equipment and it is needed to be cooled by some machines. Water coolers are the instruments which prevent overheating of machines. These have the motors which create a flow of water and cool the welding equipment. Tungsten electrodes are used in tungsten arc welding process. Tungsten electrode is used to weld stainless steel and non ferrous metals and it is called as a steel electrode.