basics of welding and symbols

7/29/2019 Basics of welding and symbols

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WELDING SYMBOLS

1. What is welding?

The process of joining two similar or dissimilar, metals or non-metals, with or without the

application of heat, with or without adding a filler material is known as welding.

2. Types of welding process:-

A. Fusion welding:It is a process of joining two pieces of metals by application of heat. The

two pieces to be weld are placed together, heated mostly with the addition of some filler material,

brought to the melting temperature and solidify on cooling. Various solid phase welding processes

a) Oxy-acetylene welding

b) Shield metal arc welding

c) Submerged arc welding

d) Gas tungsten arc welding

e) Gas metal arc welding

f) Electro slag welding

g) Plasma arc welding

h) Electron beam welding

i) Laser beam welding

B. Solid phase welding:The two metals to be brought into contact to produce a metallic bond

with or without the application of heat, but apply pressure for the plastic flow of the metals.

C. Plastic welding:It is a process in which two metals to be joined is heated to the plastic

state and external pressure is applied without the addition of filler material.Forge welding,

resistance welding and Thermit welding with pressure are the examples of the plastic

welding.


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2. What is the advantage and disadvantages of welding?

Advantages of Welding: -

(i) A good weld is as strong as the base metal.

(ii) General welding equipment is not very costly.

(iii) Portable welding equipments are available.

(iv)Welding permits considerable freedom in design.

(v) A large number of metals/alloys both similar and dissimilar can be joined by welding.

(vi) Welding can join work pieces through spots, as continuous pressure tight seams, end to end

and in a number of other configurations.

(viii) Welding can be mechanized.

Disadvantages of Welding: -

(i) Welding gives out harmful radiations (light) fumes arid spatter.

(ii) Welding results in residual stresses and distortion of the work pieces.

(iii) Jigs and fixtures are generally required to hold and position the parts to be welded.

(iv)Edge preparation of the work pieces is generally required before welding them.

(v) A skilled welder is a must to produce a good welding job.

(vi)Welding heat produces metallurgical changes. The structure of the welded joint is not same

as that of the parent metal.

(vii) A welded joint for many reasons, needs stress relief heat treatment.

3. Types of Welding Joints:-

Five basic joints are used for bringing two members together for welding:

Butt joint:a joint between two members aligned approximately in the same plane.

Corner joint:a joint between two members located approximately at right angles to each other in

the form of an L.

T-joint:a joint between two members located approximately at right angles to each other in the

form of a T.

Lap joint:a joint between two overlapping members located in parallel.

Edge joint:a joint between the edges of two or more parallel or nearly parallel members.

BASIC TYPES OF JOINTS & TERMS


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BASIC TYPE OF WELD JOINTS:-


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LOCATION OF ELEMENTS OF A WELDING SYMBOL:-

ELEMENTARY WELDING SYMBOLS:-


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COMBINATION OF ELEMENTARY

SYMBOLS


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SUPPLEMENTARY SYMBOLS:-

COMBINATION OF ELEMENTARY & SUPPLEMENTARY SYMBOLS


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TYPICAL WELDING SYMBOLS IN DRAWINGS:-

POSITION OF THE SYMBOL:-


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POSITION OF THE ARROW LINE:-

DIMENSIONING THE WELD:-


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basics of welding and symbols

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