There are no perfect welders. Just welders who are better at fixing their mistakes.
The Oxy-Acetylene Flame
The heat source for this process is a chemical reaction resulting from the combustion of acetylene with oxygen. This is an exothermic reaction in which equal volumes of acetylene and oxygen supplied by the blowpipe react to produce carbon monoxide, and hydrogen as products of the first stage of combustion.
As the supply of oxygen to the blowpipe is further increased, the flame contracts and the white cone becomes clearly defined, assuming a definite rounded shape. At this stage approximately equal quantities of acetylene and oxygen are being used and combustion is complete, all the carbon supplied by the acetylene is being consumed and the maximum heat given out. The flame is now neutral, and this type of flame is the one most extensively used by the welder, who should make himself thoroughly familiar with its appearance and characteristics.
This is a flame in which an excess of acetylene is burning, i.e. combustion is incomplete and unconsumed carbon is present. When lighting the blowpipe the acetylene is turned on first and ignited, giving a very smoky yellow flame of abnormal size, showing two cones of flame in addition to an outer envelope; this is an exaggerated form of the carburising flame, but gives out comparatively little heat and is of little use for welding. When the oxygen is turned on and the supply is gradually increased, the flame, though still of abnormal size contracts towards the blowpipe tip where an inner white cone of great luminosity commences to make its appearance. If the increase in the supply of oxygen is stopped before the cone becomes clearly defined and while it is still an inch or so long, the result is a carburising flame which is mainly used for hard surfacing and should not be employed for welding steel as unconsumed carbon may be introduced into the weld and produce a hard, brittle, deposit.
A further increase in the oxygen supply will produce an oxidizing flame in which there is more oxygen than is required for complete combustion. The inner cone will become shorter and sharper, the flame will turn a deeper purple colour and emit a characteristic slight "hiss", while the molten metal will be less fluid and tranquil during welding and excessive sparking will occur. An oxidizing flame is only used for special applications, and should never be used for welding.
Depending on the type of attachment, the Oxy/Acetylene torch can be used for heating and bending, welding, or cutting metal. The Plasma Cutter will also cut through metal, but only up to 3/8" thick.
- Follow the cutting chart for proper cutting speeds (similar to the plasma cutter) if using the cutting head
- Cutting/Welding tips will still be hot after use, be careful where you put the torch handle
- Always use the right size tip for cutting and welding
- Extra tips should be put away when not in use
- The rosebud torch is best for heating metal for bending
|Lighting Procedure||Safety Procedures|
ACETYLENE WELDING TIPS
|Metal Thickness (inches)||Tip Size (number)||Rod Size (inches)||Oxygen Pressure (psi)||Acetylene Pressure (psi)|
|1/64 - 1/32||000||1/16||3||3|
|1/32 - 3/64||00||1/16||3||3|
|1/32 - 5/64||0||3/32||3||3|
|3/64 - 3/32||1||1/8||3||3|
|1/16 - 1/8||2||5/32||4||4|
|1/8 - 3/16||3||3/16-1/4||4||4|
Metal Inert Gas welding
(From Wikipedia, the free encyclopedia)
Gas metal arc welding (GMAW), sometimes referred to by its subtypes metal inert gas (MIG) welding or metal active gas (MAG) welding, is a semi-automatic or automatic arc welding process in which a continuous and consumable wire electrode and a shielding gas are fed through a welding gun. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used. There are four primary methods of metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each of which has distinct properties and corresponding advantages and limitations.
Originally developed for welding aluminium and other non-ferrous materials in the 1940s, GMAW was soon applied to steels because it allowed for lower welding time compared to other welding processes. The cost of inert gas limited its use in steels until several years later, when the use of semi-inert gases such as carbon dioxide became common. Further developments during the 1950s and 1960s gave the process more versatility and as a result, it became a highly used industrial process. Today, GMAW is the most common industrial welding process, preferred for its versatility, speed and the relative ease of adapting the process to robotic automation. The automobile industry in particular uses GMAW welding almost exclusively. Unlike welding processes that do not employ a shielding gas, such as shielded metal arc welding, it is rarely used outdoors or in other areas of air volatility. A related process, flux cored arc welding, often does not utilize a shielding gas, instead employing a hollow electrode wire that is filled with flux on the inside.
Tungsten Inert Gas (TIG) Weldinghttp://www.efunda.com/processes/metal_processing/welding_inertgas.cfm
An arc is struck between a tungsten electrode (non-consumable) and the sheet metal to be welded. An inert gas shields the arc from the ambient to prevent oxidation. A filler material is optional. Carbon steels, low alloy steels, stainless steels, most aluminum alloys, zinc based copper alloys can be welded using this process. TIG is quite suitable for welding dissimilar materials, but usual cautions of galvanic corrosion still apply. The TIG process is a slower process compared to the MIG process, but the quality of weld is cosmetically better. There is no weld spatter, and the quality of welds is higher than MIG welding.
Personal Protection Equipment
Floppy-billed Welding Cap to protect top of head, ears, and back of neck
Hardened Shaded Welding Goggles, Shade 5
Welding helmet, shade 10 or better
Ear Plugs or Ear Muffs
Recommended if using cutting torch; Required if forging metal
Leather welding gloves
Leather top shoes - NO! tennis shoes, open toed shoes, or shoes with nylon
Leather welding jacket and long pants
NIOSH-Approved N95 Disposable Particulate Respirator
Initial lighting of the acetylene gas produces large amounts of soot
Oxy/Acetylene ONLY! Arc is a whole 'nother matter
|Lens shade no.|
|Brazing||3 or 4|
|Light cutting (up to 1")||3 or 4|
|Medium cutting (1" to 6")||4 or 5|
|Heavy cutting (over 6")||5 or 6|
|Light welding (up to 1/8")||4 or 5|
|Medium welding (1/8" to 1/2")||5 or 6|
|Heavy welding (over 1/2")||6 or 8|
Welding symbols are used on blueprints and drawings to show where the weld is to be placed and may also show the size, type of weld, number of welds, details about the weld and even details about the joint.
Welders that fabricate or work with drawing must be able to interpret the welding symbol to prepare the joint and apply a weld that has the required strength and soundness.
THE REFERENCE LINE AND ARROW
The reference line is one of the most important elements on the welding symbol. All the other elements that describe the weld are on or located around this line. The reference line has a leader and arrow that points to where the information applies. It may also have a tail that has information about the process, specification, or other notes that do not normally have an element that describes them. If the elements on the reference line describe the necessary details (as it does in most cases) the tail is not used.
In the examples one of the reference lines has multiple arrows that are used to show the same weld in three locations that are relatively close to each other. There is also a reference line that has an arrow break. The break in the arrow is used to indicate the joint member that is to receive the edge preparation.
KEY POINT: the arrow points to the bevel where the bevel needs to be prepared.
One of the most important things about the reference line and the welding symbol is the top and bottom of the horizontal line. The actual symbol that shows the type of weld and the elements surrounding it that detail the weld can be placed on the top of the line or on the bottom of the line.
KEY POINTS: Symbols on the bottom of the reference line mean weld the side of the joint the arrow is touching or pointing to. Symbols on the top of the reference line mean apply the weld to the other side of the joint, or the side opposite to where the arrow is pointing. This method is used because sometimes the welding symbol must be drawn on the blueprint on the other side of the joint. When symbols appear on both sides of the reference line it means weld both sides of the joint. If the reference line has a weld symbol on both sides of the reference line they may, or may not be the same weld on both sides of the joint. Remember the rule to apply the right weld to the right side.
OTHER ELEMENTS ON REFERENCE LINE
There are two other elements that may be seen on the reference line that provide information about the weld. One is a circle around the place where the leader line connects to the reference line and indicates the weld is "ALL AROUND". This means the weld extends all the way around the joint the arrow is pointing at.
KEY POINT: The all around element is only used when it is possible to weld all the way around a single surface. Otherwise more than one symbol is used.
The other element seen on the reference line resembles a flag and is located where the leader line joins the reference line. This element is called a field weld and means the weld will be done in another location. For instance, this weld may be applied at the job site not in the shop. Sometimes clarification will be given in the welding symbol tail or as a specification on the print.
The names of the parts of the fillet weld
THE FILLET WELD
The fillet weld symbol is one of the most widely used symbols and the shape placed on the reference line to indicate a fillet weld is a triangle that resembles the side profile of a fillet weld.
The examples of the weld all around and field weld above show a fillet weld symbol so that the weld to be applied in both cases is a fillet weld.
KEY POINT: Fillet sounds like fill it (pronounce the T) not fillay as in fillet a fish.
The important elements added to a simple fillet weld symbol are as follows:
- The size of the weld.
- The length of the weld.
- The length and pitch OF INTERMITTENT welds.
- The contour requirements.
THE SIZE OF THE WELD
The size of the fillet weld is determined by the legs of the triangle shape which represent the legs of the fillet. A welded piece may have a different weld size on each side or they may be the same size. Sometimes (not often) a weld of unequal legs may be required. For example: if one member of the joint is thinner than the other. If no size is shown on the fillet weld, a size for all fillets will be given on the drawing as a note or specification.
KEY POINT: Making the fillet welds the wrong size may lead to costly rework if you are not sure ask for clarification.
THE LENGTH OF THE FILLETWELD
The length of the weld when it is not a continuous weld is shown by a number on the right side of the fillet weld triangle. If it is not obvious the location is detailed on the drawing.
THE LENGTH AND PITCH OF INTERMITTENT WELDS
An intermittent weld is one that is not continuous across the joint, but rather is a given length of weld separated by a given space between them. This method of welding may be used to control heat distortion or where the joint strength requirements allow. Intermittent welding can save time and money if a long weld is not necessary. Used more frequently than the length alone, the length and pitch are two numbers located at the right of the fillet weld symbol. The length appears first as before followed by a hyphen then the pitch is shown. The pitch refers to a dimension from the center of one weld to the center of the next weld.
KEY POINT: The pitch is not the space between welds but a measurement from center to center of the welds. To get the spacing for layout subtract the length of one weld from the pitch.
The intermittent welds may be chain intermittent or staggered intermittent. Chain intermittent the welds on both sides of the joint are opposite each other and resemble a chain. Staggered intermittent the welds on the opposite side are usually started in the gap between the welds on the first side. The welds then appear staggered.
KEY POINT: If the welds are staggered the fillet weld symbol will be staggered on the reference line.
THE CONTOUR REQUIREMENTS
Some welding symbols may show a contour finish that details how the fillet weld shape must be finished after welding. The contour may be flat or convex and the element to describe this is placed above the slope on the fillet weld symbol. A letter to indicate the method of finish may be given above the finish element. A letter U may be used to designate an unspecified finish, when the choice of finishing is given.
- When reading a fillet weld symbol always make sure you know what side of the joint the weld is applied to. Fillet weld symbols on the bottom of the reference line mean apply the weld to the side of the joint the arrow points to. Fillet weld symbols on the top of the reference line mean apply the weld to the opposite side of the joint. Fillet weld symbols on both sides of the reference line mean apply weld to both sides of the joint. This remains the case regardless of how the break in the arrow is drawn.
- The size of a fillet weld is determined by the length of the leg of the fillet weld and is shown on the symbol to the left.
- If two numbers appear in parenthesis the legs are unequal, check the drawing for clarification.
- When a length of weld is shown on a fillet weld symbol the dimension is placed on the right side.
- When two numbers appear separated by a hyphen, the length is indicated first then the pitch. The pitch is the distance from the center of one length of weld to the center of the next length of weld.
- When finishing directions are shown they appear over the slope of the fillet weld symbol.
GROOVE WELDING SYMBOLS
Groove welding symbols are used to show how butt joints are prepared for welding and to detail how the weld is to be applied. When two pieces of metal, other than sheet metal or thin sections, are butted together for welding they usually have some form of a groove to allow the weld to penetrate into or through the joint.
The groove is formed by preparing the edges to be welded with a bevel edge, chamfer edge, double bevel edge, J groove edge or double J groove edge.
When the butt joint has no edge preparation it is referred to as a square groove.
The typical edge preparations are shown here. The edge preparations may be assembled as either open root, with a backing bar or by utilizing the back weld or backing weld application. The open root assembly allows penetration through the joint, while the backing bar is used for easier welding. The backing bar may be removed or may be a part of the joint. The backing weld is applied before welding and acts as a backing bar, while the back weld is applied after welding to finish the back side of the joint. Before applying the back weld a grinder or other method may be used to prepare a V.
The edge preparations may be assembled in any configuration to form the groove for welding from either one side or both sides. The most common configurations and their basic symbols are shown below.
KEY POINT: If two imaginary lines are drawn parallel to the horizontal line in the above symbols they show the joint shape, this is true for most of the symbols. This can be helpful to remember since symbols on a blueprint do not show the actual joint shape or edge preparation.
KEY POINT: The Groove welding symbols have the same placement relevance on the reference line as the fillet weld. Symbols on the bottom of the reference line mean weld the side of the joint the arrow is touching or pointing to, while symbols on the top of the reference line mean weld the opposite side of where the arrow is touching or pointing to.
If it is not clear always ask someone; reworking welds is costly and time consuming.
GROOVE WELDING ELEMENTS
GROOVE WELD SIZE
The groove weld size is given in two dimensions and like the fillet weld it is placed to the left of the weld symbol.
The first size given is THE DEPTH OF GROOVE and is the dimension used to prepare the edge preparation.
The depth of groove is measured from the surface of the joint to the bottom of the preparation.
KEY POINT: The depth of groove does not include weld reinforcement or root penetration.
ACTUAL WELD SIZE
The second size given is the ACTUAL WELD SIZE and is enclosed in parentheses to distinguish it from the groove size, or depth of groove. The actual weld size is again measured from the surface of the groove through the bottom of the groove but now includes the expected penetration of the weld. On a square groove only the weld size is given. The weld size does not include face reinforcement or root reinforcement.
KEY POINT: The penetration into the joint shown on the weld size is not measurable by the naked eye but is given to provide information about the expected outcome.
ROOT OPENING AND GROOVE ANGLE
Two other important elements for preparing and welding the groove are the root opening and the groove angle. The root opening, when used, dimensions the space between the joint to be welded and is placed inside the weld symbol. The groove angle is also placed inside the weld symbol and is given in degrees.
KEY POINT: The groove angle for a V groove is given as the INCLUDED angle so that means the edge bevel or chamfer for each piece is 1/2 of the degrees given. For example; A 45 degree included angle means bevel each member at 22 1/2 degrees. J grooves angles may be detailed elsewhere on the drawing. The root opening and groove angle are separate elements and may or may not appear together depending on the joint requirements.
On some drawings the root opening or groove angle will be covered in a note or specification on the drawing for all similar symbols, and does not appear on the symbol.
The Welder must always read all information given on a drawing.
CONTOUR AND FINISHING
The same contour symbols that apply to fillet welds may be used with groove welding and are placed above the weld symbol.
BACKING BARS BACK WELDS AND SPACERS
As previously mentioned in this section some joint configurations may have a backing bar or spacer for easier welding or may employ the back or backing weld technique. The elements for these are placed on the bottom of the reference line opposite the weld symbol or in the case of the spacer on the reference line.
KEY POINT: If the backing bar is to be removed the symbol will contain an R for remove after welding. Since the back and backing weld symbol look the same you must look for details to see which weld applies. Spacers may be removed before the second side is welded or they may become part of the joint.
The groove weld symbols are used to provide information for preparing and welding the groove; however, they cannot always show every intended operation and often notes or specifications are used on the drawing. The welder should read the entire drawing before making a weld to avoid costly rework. Whenever you see something you are unfamiliar with check with engineering or supervision for clarification.
It is critical to produce the right size fillet and groove weld for the application so check sizes with weld gauges.
Oxyacetylene Welding (Filler) Rods
The use of the proper type of filler rod is very important in oxyacetylene welding operations. This material not only adds reinforcement to the weld area, but also adds desired properties to the finished weld. By selecting the proper type of rod, either tensile strength or ductility can be secured in a weld. Similarly, rods can be selected that will help retain the desired amount of corrosion resistance. In some cases, a suitable rod with a lower melting point will eliminate possible cracks from expansion and contraction.
Welding rods are classified as ferrous and nonferrous. The ferrous rods include carbon and alloy steel rods as well as cast iron rods. Nonferrous rods include brazing and bronze rods, aluminum and aluminum alloy rods, magnesium and magnesium alloy rods, copper rods, and silver rods. The diameter of the rod used is governed by the thickness of the metals being joined. If the rod is to small, it will not conduct heat away from the puddle rapidly enough, and a burned weld will result. A rod that is to large will chill the puddle. As in selecting the proper size welding torch tip, experience will enable the welder to select the proper diameter welding rod.
Arc Welding Rod Numbers Decoded (from Damon Gentile)
Typical arc welding rod has a part number like: E6010 or a fancy one is E8018-B1-H4R. Let's start by decoding the short one. If you have digits left over, it's a long number, read on. This can be decoded fairly easily.
E stands for "Electrode"
The first two digits (or first 3 if it's a 5-digit number) are an abbreviation of the weld's strength. To figure out the strength of the weld, take the 2 digits, in this case 60, and multiply by 1000 to get the weld strength in PSI. So if you had welded two plates together, with the weld covering one square inch (or even 1/4" x 4" : that's still one square inch) that weld could take 60,000 pounts of pulling force. Typical vales are 60,70,80,90,100,110.
The 3rd digit tells you what position the rod is recommended for.
|1||Flat, Horizontal, Vertical, Overhead|
|2||Flat and Horizontal only|
|3||Flat, Horizontal, Vertical Down, Overhead|
The last digit tells you about welding current and the coating.
|2||AC or DC:ROD+
|3||AC or DC:ROD-||titania sodium|
|4||AC or DC:ROD-
|iron powder titania|
|5||DC:ROD+||low hydrogen sodium|
|6||AC or DC:ROD+||low hydrogen potassium|
|7||AC or DC:ROD+
|iron powder iron oxide|
|8||AC or DC:ROD+||iron powder low hydrogen|
You probably don't need to worry much about the coating.
I have in my notes, but don't remember where I read it, that having the rod + will give deeper penetration, and the rod - will give faster deposition.
If there is a letter and number combination next, it relates to the chemical composition of the weld deposit.
|* (G only needs one of the elements listed)|
Next part is a H#. This relates to the maximum amount of hydrogen that will be diffused from the rod.
A trailing R means that the rod is moisture resistant.
Select Your ElectrodeSource: http://www.millerwelds.com/products/helpmechoose/basics5.html
If you plan to weld with a particular diameter electrode, you need to know its operating range (basically, smaller electrodes carry less current, larger electrodes carry more current). The following chart suggests operating ranges for common Stick, wire, TIG and carbon arc gouging electrodes. This helps you determine which electrode sizes you can use with a particular machine.
|Amperage for Stick Electrodes|
|Stick diameter and type||3⁄32"||1⁄8"||5⁄32"||3⁄16"||¼"|
|Amperage and Voltage for Wire Electrodes — Part 1|
|Wire diameter and type||.030"||.035"||.045"||.052"||1⁄16"|
|Tubular (flux or metal cored)||N/A||N/A||15-36V
|Self-shielded flux cored||N/A||14-20V
|Amperage and Voltage for Wire Electrodes — Part 2|
|Wire diameter and type||.072"||5⁄64"||3⁄32"||7⁄64"||1⁄8"|
|Tubular (flux or metal cored)||22-36V
|Self-shielded flux cored||16-25V
|Amperage for TIG Welding|
|Tungsten type & diameter||1⁄16"||3⁄32"||1⁄8"||3⁄16"||¼"|
|Amperage for Carbon Arc Gouging|
Gee Mom, look what else I've found!
- begin listing of videos, books, links, etc. for more
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