WELDING PROCESSES

WELDING PROCESSES

Each of the welding and cutting processes will be treated as follows :

æ Weldability

æ Welding metallurgy

æ Welding chemistry

æ Prewelding preparation

æ Limiting factors

æ Discontinuities

æ Inspection processes

Whaever process is specified by engineer, both you and welder must also be aware of limiting factors for specific job, so that you both can anticipate and overcome the factors that could cause discontinuities or more serious problems.

In addition to weldability, these other factors influence the selection of welding process :

æ Dimensions of material being welded, especially thickness, and its shape or form

æ The welding positionthat must be used

æ Root of joint requirements

æ Back side accessibility

æ Joint preparation

æ Availability of welding equipment, power sources, and fixtures

æ Availability of consumables

æ Availability of qualified welders and opearators

æ Quality level required

æ Economics

æ Safety

WELDING PROCEDURE AND WELDER QUALIFICATION

WELDING PROCEDURE AND WELDER QUALIFICATION

Ñ The welding procedure qualification is utilized to show the compatibility of :

1) Base metal(s)

2) Weld or braze filler metal(s)

3) Process(es)

4) Techniques

Ñ The general sequence of Welding Procedure Qualification

1) Select welding variables

2) Check equipment and materials for suitablity (kesesuaian)

3) Monitor weld joint fitup as well as actual welding, recording all important variables and observations

4) Select, identify and remove required test speciments

5) Test and evaluate specimens

6) Review test results for compliance with applicable code requirements

7) Realease approved procedure for production

8) Qualify individual welders in accordance with this procedure

9) The welding inspector must then monitor the use of that procedure during production to assure that it continues to produce satisfactory results.

Ñ The general sequence of Welder Qualification

1) Identify essential variables

2) Check equipment and materials for suitablity (kesesuaian)

3) Check test coupon configuration and position

4) Monitor actual welding to assure that it complies with aplicable welding procedure

5) Select, identify and remove required test samples

6) Test and evaluate specimens

7) Complete necessary paperwork

8) Monitor production welding

MECHANICAL AND CHEMICAL PROPERTIES OF METALS

MECHANICAL AND CHEMICAL PROPERTIES OF METALS

Ñ Review documentation related to the actual properties of base and filler metal

Ñ Compare specification values with actual numbers to judge compliance

Ñ He can predict problems which may accur during welding

Mechanical Properties of Metal :

a. Strength

b. Ductility

c. Hardness

d. Toughness

e. Fatigue strength

a. STRENGHT is defined as the capacity of a material to withstand some applied load.

Ñ Tensile strength

Ñ Compressive strength

Ñ Shear strength

Ñ Torsional strength

Ñ Impact strength

Ñ Fatigue strength

Ñ Tensile strength is described as ability of metal to resist failure when subjected to a tensile, or pulling load.

Ñ Tensile strength expressed into two defferent ways i.e Ultimate tensile strength (tensile strength) and Yield strength.

Ñ Ultimate tensile strength (tensile strength) relates to the maximum load carrying capasity of metal, or failure occurs.

Ñ Yield strength is meant when a metal behaves elastically.

Ñ Behavior changes from elastic to plastic is referred to as its yield point.

Ñ Determined by conducting a tensile test, it is also possible to make indirect measurement of strength using hardness test. If hardness increases, tensile strength increase.

Ñ As temperature increases, the strength of a metal will decreases.

Ñ As temperature increases, the ductility increases as well and vice versa.

b. Ductility

Ñ The ability of a material to deform, or stretch (menegang), without failing

Ñ More ductile the more it will stretch.

Ñ Determines whether the metal fails gradually (high ductility) or suddenly (low ductility) when loaded.

Ñ Low ductility is reffered to as being brittle (no deformation before fracture)

Ñ The ductility can be expressed in one of two ways, either as percent elongation or percent reduction area.

Ñ The strength and ductility of a rolled metal is greatest in the direction of rolling.

c. Hardness

Ñ It is defined as the ability of a material to resist identification.

d. Toughness

Ñ The ability of material to absorb energy

Ñ The low toughness value difines brittle behaviour while a high value of toughness is related to a ductile failure.

Ñ The temperature is reduced, the toughness of metal decrease as well.

e. Fatigue strength

Ñ Defined as that strength to resist failure under repeated load applications

Ñ The majorrity of metal failures are the result of fatigue.

Ñ Related to the number of cycles required to cause a failure

Ñ Determined though fatigue testing.

Ñ The S-N curve is simply a graphic description of how many fatigue cycles are necessary (perlu) to produce a failure at various stress level.

Ñ A surface discontinuities, will more quickly lead to fatigue failure.

Chemical Properties of Metals

Ñ Drastic changes will also occur if the chemical composition is change

ANSI/AWS STANDARD WELDING TERM AND DEFINITION

ANSI/AWS STANDARD WELDING TERM AND DEFINITION

FUSION WELDING. The melting together of filler metal and base metal, or of base metal only, to produce a weld.

SOLID STATE WELDING. A group of welding processes that produces coalescence by the application of pressure at welding temperature below the melting temperatures of the base metal and the filler metal.

WELD. A localized coalescence of metals or nonmetals produced either by heating the materials to the welding temperature, with or without the application of pressure, or by application of alone and with or without the use of filler metal.

WELDABILITY. The capacity of material to be welded under the imposed fabrication conditions into a specific, suitably designed structure and to perform statisfactorily in the intended service.

WELDING. A joining process tha produces coalescence of metals or nonmetals produced either by heating the materials to the welding temperature, with or without the application of pressure, or by application of alone and with or without the use of filler metal.

AS-WELD, Adj. Pertaining to weld metal, welded joints, and weldments after welding, but prior to any subsequent thermal, mechanical, or chemical treatment.

WELDING ELECTRODE. A component of the welding circuit through which current is condected and that terminates at the arc, molten conductive slag, or base metal.

ARC/WELDING ARC. A controlled electrical discharge between the electrode and the workpiece the is formed and sustained by the establishment of a gaseous conductive medium, called an arc plasma.

WELDER. One who performs manual or semiautomatic welding.

OPERATOR WELDING. One who operates welding machine / robotic .

BRAZE. A weld produced by heating an assembly to the brazing temperature using a filler metal having a liquidus above 450 C (850 F) and below the solidus of the base metal. The filler metal is distributed between the closely fitted faying surfaces of the joint by capillary action.

Liquidus is the lowest temperature at which a metal or an alloy is completely liquid.

Solidus is the higest temperature at which a metal or an alloy is completely solid.

BRAZEABILITY. The capacity of material to be brazed under the imposed fabrication conditions into a specific, suitably designed structure, and to perform satisfactorily in the intended service.

BRAZING. A group of welding processes that produces coalecence of material by heating them to the brazing temperature in the presence of a filler metal having a liquidus above 450 C (850 F) and below the solidus of the base metal. The filler metal is distributed between the closely fitted faying surfaces of the joint by capillary action.

BRAZING FILLER METAL. The metal that fills the capillary joint clearance and has a liquidus above 450 C (840 F), but below solidus of base metal.

BRAZE WELDING/FLOW WELDING. A welding process variation that uses a filler metal with a liquidus above 450 C (850 F) and below the solidus of the base metal. The base metal not melted. Unlike brazing, in braze welding, the filler metal is not distributed in the joint by capillary action.

BRAZER. One who performs manual brazing.

BRAZING OPERATOR. One who operates automatic, furnace, or mechanized, brazing equipment.

SOLDERING. A group of welding process that produces coalescence of materials by heating them to the soldering temperature and by using a filler metal having a liquidus not exceeding 450 C(850 C) and below the solidus of the base metals. The filler metal is distributed between closely fitted faying surfaces of the joint by capilary action.

BUILDUP. A surfacing variation in which surfacing material is deposited to achivethe required dimensions.

BUTTERING. A surfacing variation that deposits surfacing metal on one or more surfaces to provide metallurgically compatible weld metal for the subsequent completion of the weld.

CLADDING. A surfacing variation that deposits or applies surfacing material usually to improve corrotion or heat resistance.

CLAD METAL. A laminar composisting of a metal or alloy, with a metal or alloy of different chemical composition applied to one or more sides by casting, drawing, rolling, surfacing, thick chemical deposition, or thick electroplating.

HARDFACING. A surfacing variation in which surfacing material is deposited to reduce wear

WELD JOINT GEOMETRY AND WELDING TERMINOLOGY

WELD JOINT GEOMETRY AND WELDING TERMINOLOGY

A joint is the junction of numbers or edges of members which are to be joined or have been joined.

There are five basic types of joints :

a. Butt

b. Corner

c. T

d. Lap

e. Edge

Parts of the Weld Joint

Type of Welds

There are 18 basic types of welds utilized for arc welding :

Ñ Square – groove weld

Ñ Bevel – groove weld

Ñ V- groove weld

Ñ J - groove weld

Ñ U - groove weld

Ñ Flare-bevel- groove weld

Ñ Flare-V- groove weld

Ñ Fillet weld

Ñ Edge weld

Ñ Edge-flange weld

Ñ Corner-flange weld

Ñ Spot weld

Ñ Seam weld

Ñ Plug weld

Ñ Slot weld

Ñ Surfacing weld

Ñ Back weld

Ñ Backing weld

Single-welded joint is a fusion welded joint that is welded from one side only

Double-welded joint is a fusion welded joint that is welded from both side

Fillet weld is not type of joint. It is a particular type of weld which can be applied to a lap, T-, or corner joint.

Fillet weld is a weld of approximately triangular cross section joining two surface approximately at right angles to each other in a lap joint, T-joint, or corner joint.

Back weld

Ñ As a weld made at the back of a single groove weld

Ñ Applied after the front side has already been welded

Backing weld

Ñ As backing in the form of a weld

Ñ Deposited prior to the welding of front side

STANDARDS

STANDARDS

æ Something established (ketentuan) for use as a rule or

æ Basis of comparasion in measuring or

æ Judging capacity, quantity, content, extent, value, quality. Etc.

æ Other types of documents which are considered to be standards are :

Ñ Procedures

Ñ Recommended practices

Ñ Groups of graphic symbols

Ñ Clssifications

Ñ Definitions of terms

æ Some of these considerd to be mandatory

Ñ The information is an absolute requirement

Ñ Adoption of a law or regulation

Ñ “Shall” and “Will” their requirements are not a metter of choice.

Ñ Codes are examples of mandatory standards because they have legal status

æ Some of these considerd to be non-mandatory

Ñ Nonmandatory standard would be a recommended practice, because it may provide alternative ways in which objectives can be accomplisehed.

Ñ Words “Should” and “Could”

Ñ The implication here is that the information has been put forth to serve as a guidelines for someone to perform particular task. However, it dosen’t mean that something is rejectable just because it fails to comply with that guidline.

National standards are the result of an elaborate voting and review procedure overseen by American National Standards Institute (ANSI)

CODE

CODE

A code is a body of laws, as of nation, city, etc., arranged systematically for easy reference.

When a structure is bulit within the jurisdiction of a city or state, it often must comply with certain “building codes”. Since a code consists of “laws” having legal status, it will always be considered mandatory. Therefore, we will see text containing words such as “shall” and “will”.

Examples :

AWS D1.1, Structural Welding Code – Steel

ANSI/ASME B31.1, Power Piping

ASME Section I untill XI