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Basic Welding Knowledge

Time:2008-11-16 Tag:welding  

Types of weld joints: Five most common types of joints are the Tee, Butt, Lap, Corner and Edge joints.

Types of welds: The two common types of welds will be considered either a fillet weld or a groove weld.

Fillet weld: A right triangular cross section of filler metal deposit joining two pieces of base material at or nearly perpendicular to each other.  By fare the most common type of weld and usually requiring no material preparation other then cleaning. 

    A fillet weld is not a full through thickness penetration weld but that can be used in conjunction with a groove weld to aid in a full penetration joint.

    Groove welds: Are a partial penetration or full penetration through thickness weld deposit of the base material. Groove welds usually require some base material preparation of at least a single bevel face.  A square groove but joint requires no bevel preparation, but some time four or more angles will be used on a groove joint.  There are depths of preparation details, root face and root opening details, bevel angle details groove opening detail's or included angles.

Weld Details: The common details of a weld are the Root, Throat, Face, Toes and the leg length or bevels depending if we are talking about a fillet weld or groove weld.

Types of weld throat details: Theoretical throat, Effective throat and Actual throat.

Welding Positions: This is a relatively easy numeric alpha system. The main key of knowing welding positions (after learning the numeric alpha (Abbreviation) is ask what position is the weld face in? The plates or pipe can be in a certain position, but technically the weld face will be in the correct numeric alpha position other than what the plates or pipe appears to be in.

                                       1 stands for Flat position.
                                       2 stands for Horizontal position.
                                       3 stands for Vertical position.
                                       4 stands for Overhead position.

                                       F stands for fillet weld
                                       G stands for groove weld.

So if we are welding an vertical fillet weld what numeric alpha position are we welding?  Answer: 3F for vertical fillet weld.  Pipe welding position become a little bit more tricky due to the fact the pipe may or may not be rotated.

Weld quality definitions: The list below is only a start.  Forgive us for not having it completed yet.  We hope to give the definition and then include information that will apply to maybe you specifics. 

    Discontinuities: Acceptable variations of the weld deposit.  There is no such thing as a perfect weld.  The alloying content, heat input, grain structure, weld stresses even going through all the post weld treatments to make a weld to the highest quality, the weld never is identical to the original base material.  So all welds have some degree of discontinuities.  The type of and volume of discontinuity, up to a certain specified acceptance criteria is acceptable.

    Defects: A type and volume of weld discontinuities that exceed acceptable limitations.  A defect is not acceptable and must be reported as a reject and not allowed for use with out repairing.  The acceptance standard for weld rejection varies.  Each code, specification or welding applications have different acceptance or rejection tolerances, depending on the load, requirements, or concerns of the weld.

Types of weld discontinuities and defects:

Welding Processes Advantages and Disadvantages: Each process has many characteristics.  Choosing a particular process or modifying a process for the welding needing to be done can be very involved.  The decision can be simple because your limited by wind 14 floors up, but then choosing a process that meets the quality and production needs in a cost effective manor may not be so simple. 


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