Page 42 - CITS - Welder - Trade Theory

WELDER - CITS

Edge Preparation

Objectives: At the end of this lesson you shall be able to
• state the necessity of preparing the materials to be welded
• state different methods used to cut mild steel sheets and plates to the required size before welding
• identify different tools and equipments used to prepare the mild steel sheets and plates
• state the types of edge preparation.

Definition
The term Edge preparation refers to the manner in which the edges of work pieces are prepared prior to welding
in order to accommodate the weld metal, and . varies according to such factors as the type of metal thickness of
plate and the method of welding to be employed.
Necessity of edge preparation

Edge preparation of plates is required before butt welding due to the following reasons:
1 To ensure full thickness of preparation.
2 To obtain full strength weld with minimum of weld metal.
3 To limit distortion due to welding.
4 To accommodate the weld metal.
5 To obtain welds free from defects.

Influencing factors
Joint to be prepared are largely influenced by the view point of economy. The preparation is done prior to
welding in order to obtain the required strength. The following factors are to be taken into consideration for the
edge preparation.
1 The welding process like SMAW, Oxy-Acetylene welding, MIG/MAG/Co electro slag etc.
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2 The type of metal to be joined, i.e. mild Steel, stainless steel, aluminium etc.

3 The thickness of metal to be joined.
4 Economic factor.
Method of edge preparation
The joining edges may be prepared foe welding by any one of the metliods mentained below.
i Flam cutting

ii Machine tool cutting
iii Machine Grinding or Hand grinding
iv Filing chipping.
Type of edge preparation
Deferent type of plate preparation have been designed which permit penetration of plates with minimum of weld
metal
1 Flanged preparation: For Sheet metal up to 1/16 inch (1.6mm) thickness, the edges to be joined should be
flanged, the upturned edges to joint Should be Flanged, the upturned edge being at right angles to the sheet
and of a depth equal to about twice the thickness of the Sheet. Flanging may be performed by the special
machines built for this purpose or the material could be held in a vice and hammer to the require shape. Such
type of joint is known as Flanged joint.
2 Squire edge preparation: For material of thickness between 1/16 inch and 1/4 inch (16mm to 6mm) it is not
necessary to flange or to bevel the edges; the latter are left Square, such joints are turned as Square Butt joint.
and the preparation is known as square edge preparation square butt joints are of two types.

3 Closed square butt joint: It is used for plates up to 3 mm thick where full thickness penetration is not
necessary

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CITS : C G & M - Welder - Lesson 6&7