basic welding

EXCHANGE PROGRAMME OF TECHNICAL INFORMATION

• BY

• PM-MA (STEEL)

• M U B A R R A Z

• 23RD MARCH 2009

SUBJECT PROPOSED & SUPPORTED BY:

• MR N. SUGAYA

• &

• MR GHASSAN

BASIC WELDING

• COMMON WELDING PROCESSES

• WELDING TERMINOLOGY

• WELD SYMBOLS / JOINT CONFIGURATION

• WELDING SAFETY

BASIC WELDINGCommon Welding Processes

Listed below are some of the more common welding processes used :

• SMAW -Shielded Metal Arc Welding (stick)• GMAW -Gas Metal Arc Welding (mig)• GTAW -Gas Tungsten Arc Welding (tig)• SAW -Submerged Arc Welding


• SMAW- Shielded Metal Arc Welding uses the heat of an electric arc between a covered metal electrode and the work (pipe, plate, etc). Shielding comes from the decomposition of the electrode flux coating. Filler is supplied by the electrode core wire and covering (iron powder and alloys).This process is usually done manually. The basic equipment is a power source, an electrode holder, a work clamp and the electrode. Electrodes operate variously on alternating current, direct current electrode positive (reverse polarity) or direct current electrode negative (straight polarity).


• SMAW welding metallurgy– Weld is strengthened by adding alloying elements and by

incorporating iron powder in the electrode covering(flux). Some ingredients in the covering may attract and hold moisture (a source of hydrogen) which causes cracking in certain welds. A group of electrodes specifically formulated to result in weld deposits having very low levels of hydrogen are referred to as “Low Hydrogen” electrodes. These have identification numbers ending in 5,6 or 8. Once removed from containers they require electrically heated storage in a vented oven capable of holding the electrodes between 250 – 350 deg F. (Low hydrogen electrodes should be stored in their original containers until ready for use)


• SMAW ELECTRODE IDENTIFICATION SYSTEM

E X X X X

STRENGTH

POSITION

COATING / OPERATING CHARACTERISTICS

Strength- Tensile strength (I.E. 70, or 60) 70,000 psi / 60,000 psi

Position: 1= all positions. 2= flat and horizontal fillet position only

Example: E-7018, E-6010


• SMAW limiting factorsAll of the welding manipulations are controlled by the welder, such as electrode inclination, arc length and travel speed. The welder must set the proper current and select polarity if direct current.

• DiscontinuitiesAlmost any defect or discontinuity can be produced, but the most common is porosity, and slag inclusions.


• GTAW – Gas Tungsten Arc Welding (TIG) uses an electric arc between a non consumable electrode (Tungsten) and the work. Shielding is obtained from an inert gas (Argon gas) or inert gas mixture. Filler metal is added as needed. Welds may be made with or without filler metal as required. Inert Gas purging is done as required.

• The most significant feature in GTAW is that the electrode (Tungsten) used is not intended to be consumed. Only the filler metal is consumed.


• Limiting Factors

The outstanding factor of GTAW is the exceptional cleanliness that can be obtained in the weld, producing crack free welds in alloys that are difficult to weld in other process. However the limiting factor is the high skill level necessary to produce high quality welds is acquired by long experience in manipulating the electrode and feeding the filler wire when used.

WELDING TERMINOLOGY

• Destructive testing- a sampling of the weld that is actually taken from the weldment and is subjected to a bend, tension, or other form of test that usually destroys the test coupon.

• Essential variables- are those which a change, is considered to affect the mechanical properties of the weldment and shall require requalification of the WPS

• Filler metal- The consumable electrode that is used in most welding processes to fill the weld groove

• Flux- The coating on welding electrodes that when decomposes during welding forming a shielding gas around the weld.

JOINT CONFIGURATION

Butt Weld• 1= Groove Face

• 2= Root Opening

• 3= Groove Angle

• 4= Root Face

• 5=Plate thickness

• 6=Bevel Angle 1 2

3

4

5

6

JOINT CONFIGURATION• Root Opening – A separation at the joint root between the

two work pieces• Root Face – The portion of the groove face adjacent to the

joint root• Groove Face – The surface of a joint member included in the

groove• Groove Angle – The total included angle of the groove

between the two work places• Bevel Angle – The angle formed between the prepared edge

of a member and a plane perpendicular to the surface of the member

• Groove weld size – The joint penetration of a groove weld• Plate thickness – The thickness of the base metals to be

welded

JOINT CONFIGURATION

Parts of a butt weld

Weld Face

Weld Root

Toe of Weld both side

Face or Weld Reinforcement

JOINT CONFIGURATION

• Parts of a butt weld

Heat Affected Zone (HAZ)

Weld Metal

Groove FacesCap

Root

Base Metal

WELDING SYMBOL

Arrow side

Other side

R

F

A

(E)S L-P

(N)

Finish symbol

Contour symbol

Groove angle

Root opening

Length of weld

Pitch (center to center )

Weld all around symbol

Reference line

S

I

D

E

S

B

O

T

H

The weld symbol both sides or one side

Groove weld size

Depth of bevel

Arrow connecting reference line to arrow side member of joint or arrow side of joint

Number of spot, seam or plug welds

Tail omitted when reference not used

Length of weld

Field weld

WELDING SYMBOL

• Examples: Single V Butt Weld

1/8

1/8 root opening

1/875 deg

75 deg

75 deg. groove angle

WELDING SYMBOL

• Staggered intermittent fillet weld

3-10

3-10

Fillet weld side view

10”

3”

(3/8)

(3/8)

3/8”

WELDING SYMBOL

Single V Groove

Double V Groove

Single Bevel Groove

Double Bevel Groove

WELDING SAFETY

• SAFETY IS AN IMPORTANT CONSIDERATION IN ALL WELDING, CUTTING AND RELATED WORK

• Only approved welding, cutting, equipments are to be used. Such equipment includes torches, regulators, welding machines, electrode holders, and personal protective devices.

• Proper use and maintenance of the equipments. • Personnel in areas next to welding and cutting must also be

protected from radiant energy and hot spatter

WELDING SAFETY• Open flame, electric arcs are a ready source of ignition.

The best protection against fire is to do welding and cutting in specially designated areas or enclosures made of non combustible materials

• Welding helmets containing the appropriate filter plates must be used by welders and nearby personnel when viewing an arc.

• Sturdy shoes, boots and heavy clothing should be worn to protect the body from flying sparks, spatter and radiation burns. (cuff less pants and covered pockets are recommend

• Durable leather gloves or other suitable material should be worn

• Ear plugs should be worn when performing air arc gouging

WELDING SAFETY

DURING RADIOGRAPHIC TESTING OF WELD JOINTS

• Please do not forget x-ray (gamma ray) radiation safety. Obey all x-ray barrier signs. Do not go into these areas when radiography is taking place (normally magenta and yellow tape)

REMEMBER, WELDING SAFETY IS A VERY IMPORTANT PART OF WELDING

WELDING WRAP UP

• This presentation is only a brief overview of welding and is intended to only give a general understanding and familiarization of some of the more common processes, welding symbols and safety.

• PLEASE REMEMBER: ADOC POLICY: ALWAYS SAFETY FIRST

Thank you for your attendance.

basic welding

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