Selection of Stick Electrodes

 सही 'स्टिक इलेक्ट्रोड' का चयन

Selection of Stick Electrodes

Welding rod selection

स्टिक इलेक्ट्रोड विभिन्न यांत्रिक गुणों के साथ उपलब्ध हैं और यह एक विशिष्ट शक्ति स्रोत के साथ संचालित होता है। वेल्डिंग रॉड चयन में विचार किए जाने वाले कारक निम्नलिखित हैं:

• Tensile strength

• Base metal properties

• Welding current

• Base metal thickness, shape, and joint fit-up

• Welding position

• Specification and service conditions

• Environmental job conditions

Tensile strength

Match the minimum tensile strength of the electrode with the tensile strength of the base metal. This can be identified by referring first 2 digits of the AWS classification of the electrode. For example, the number “70” on an E7018 electrode indicates that filler metal produces a weld bead with a minimum tensile strength of 70,000 psi and, would work with steel of similar tensile strength.

Base metal properties

The first step is to determine base metal composition than its mechanical properties.

• धातु कैसे दिखता है? यदि टूटे हुए भाग या घटक में मोटे और दानेदार आंतरिक सतह होती है, जिसका अर्थ है कि आधार सामग्री एक कच्चा धातु है।

• धातु चुंबकीय है? यदि बेस मेटल चुंबकीय है, तो संभावना है कि बेस मेटल कार्बन स्टील या मिश्र धातु स्टील है। यदि आधार धातु चुंबकीय नहीं है, तो सामग्री मैंगनीज स्टील, सहायक स्टेनलेस स्टील या एल्यूमीनियम, पीतल, तांबा या टाइटेनियम जैसे अलौह मिश्र धातु हो सकती है।

• एक ग्राइंडर द्वारा छुआ जाने पर धातु किस तरह की चिंगारियां देती है? अंगूठे के एक नियम के रूप में, स्पार्क में अधिक भड़कना उच्च कार्बन सामग्री को इंगित करता है जैसे कि ए -36 ग्रेड स्टील।

• बेस मेटल में छेनी "काटता है" या उछलता है? एक छेनी नरम स्टील या एल्यूमीनियम जैसे नरम धातु में काटेगी, और उच्च कार्बन स्टील, क्रोम-मोली या कच्चा लोहा जैसे कठोर धातुओं से उछल जाएगी।

Welding current

Current type:-

Depending upon the 4th digit of an electrode’s AWS classification, the current type can find out. It is based on the type of coating available on the electrode (see below figure).

4th Digit Type of Coating Welding Current

0         Cellulose sodium       DCEP

1        Cellulose potassium      AC or DCEP

2        Titania sodium             AC or DCEP

3        Titania potassium       ALL

4        Iron powder titania     ALL

8       Iron powder low hydrogen  AC or DCEP

DCEP- DIRECT CURRENT ELECTRODE POSITIVE,

DCEN- DIRECT CURRENT ELECTRODE NEGATIVE,

DCEP compatible electrode influences the penetration profile of the resulting weld. DCEP compatible electrode delivers deep penetration and produces an excellent arc. DCEN suitable (compatible) electrode provides light penetration and works well when welding high speed, high current fillet welds in the horizontal position.

An AC-compatible electrode can produce a soft arc with medium penetration of weld and can be used to weld sheet metal.

Base metal thickness, shape, and joint fit-up

Welding of thick materials needs an electrode that has maximum ductility and low hydrogen to prevent cracking. Electrodes with good toughness (high impact values) can accommodate for residual stress.

Welding position

The third digit in AWS classification of a particular electrode tells about its positional qualification. For exam- a 7018 electrode can be used in the flat, horizontal, vertical, and overhead positions.

1 = flat, horizontal, vertical, and overhead

2 = flat and horizontal only

Specification and service conditions

Take into consideration of its use- high heat, low temperature, repetitive shock loading, and pressure vessel or boiler fabrication. AND

Environmental job conditions

Metal transfer modes in GMAW

Metal transfer modes in GMAW

Globular 

Globular  मेटल ट्रांसफर के साथ GMAW को तीन प्रमुख GMAW विविधताओं में से सबसे कम वांछनीय माना जाता है, क्योंकि इसकी उच्च गर्मी, खराब वेल्ड सतह और स्पैटर का उत्पादन करने की प्रवृत्ति है। विधि को मूल रूप से GMAW का उपयोग करके स्टील को वेल्ड करने के लिए एक लागत-कुशल तरीके के रूप में विकसित किया गया था क्योंकि यह भिन्नता कार्बन डाइऑक्साइड का उपयोग करती है, जो आर्गन की तुलना में एक कम महंगा परिरक्षण गैस है। जिससे 110 मिमी / एस (250 / मिनट) तक की वेल्डिंग गति की अनुमति दी जा सकती थी। जैसा कि वेल्ड किया जाता है, इलेक्ट्रोड से पिघली हुई धातु की एक गेंद इलेक्ट्रोड के अंत में निर्मित होती है, अक्सर इलेक्ट्रोड की तुलना में एक बड़े व्यास के साथ अनियमित आकार में होती है। जब छोटी बूंद या तो गुरुत्वाकर्षण या लघु-चक्कर द्वारा समाप्त हो जाती है, तो यह असमान सतह को छोड़ कर अक्सर स्पैटर का कारण बन जाती है। बड़ी पिघली हुई छोटी बूंद के परिणामस्वरूप, प्रक्रिया आमतौर पर फ्लैट और क्षैतिज वेल्डिंग पदों तक सीमित होती है, इसके लिए मोटे वर्कपीस की आवश्यकता होती है, और एक बड़े वेल्ड पूल में परिणाम होता है।

GMAW WELDING PROCESS

GMAW WELDING PROCESS

GAS METAL ARC WELDING (GMAW)
In this process, an arc is maintained in a stream of inert gas between a consumable electrode and the workpiece. The arc heats the work and melts the electrode, which thus supplier filler metal for the joint.   The power sources used are direct current with electrode positive.   The metal transfer is irregular if the electrode is negative or if the alternating current is the use of whilst effective welding of aluminum is only possible if the workpiece is negative so that oxide film is removed by the action of the arc cathode.

Arc Welding with Coated Electrode (SMAW)

Arc Welding with Coated Electrode

Arc welding is carried out by striking an arc between a rod electrode and the workpiece, thus simultaneously heating the workpiece and melting the electrode, which supplies filler metal for the joint. The power supply used In welding with coated electrodes consists of a DC or AC source with a dropping characteristic.

PWHT, Stress reliving Procedure

 PWHT / Stress reliving Procedure

1.0 Scope:-

This describes the Procedures Provide information for heat treatment (Stress relieving only) for Carbon steel, alloy steel.

2.0 Reference Codes & Specification:-

• ASME Section VIII Div.1

• AWS D1.1

• Railway Specification.

• Manufacturing Drawing.

• Welder Procedure specification.

Preheating is Important

Why Preheating is Important?

Preheating minimizes the temperature difference between the arc and the material being welded. This benefits the weldment in the following ways.

1. it helps to reduce shrinkage stresses that can lead to cracking and distortion. 

CERAMIC BACKING STRIPS

CERAMIC BACKING STRIPS 

 ACHIEVEs

• X-Ray quality root welds In one

• Fu.ll penetration welds from one    

• Uniform back beads of finished quality 

• Root weld end fill in one pass

Application of Ceramic Backing Strip

3metres/minute and produce excellent and accurate bevels. The plates can be beveled, over a range of
6mm to 58mm; and the maximum bevel that can be cut is 28mm. A range of bevellers are available for bevelling different sections of Carbon Steel, Aluminum, Stainless Steel, and Titanium.

WELD AND MAGNETIC FIELD

Effect of Magnetic Field on Welding...

EFFECT ON WELD GEOMETRY

A magnetic field can deflect the arc perpendicular to the welding direction as AC current changes its direction because the direction of electrons changes and this changes the direction of the force on them. This way arc is deflected from the line of a weld. This results in an increase in bead width also. 

shrinkage a big factor in welding

How to calculate shrinkage in welding

What is shrinkage?

In a welded joint, expansion and contraction forces act on the weld metal and on the base metal. As the weld metal solidifies and fuses with the base metal, in this stage, it is in its maximum expanded form. While cooling, weld metal contract to the volume it would normally occupy at the room temperature, but it is restricted by the adjacent base metal. Because of this, stresses develop within the weld metal and the adjacent base metal. 

HEAT INPUT IN ARC WELDING

ARC ENERGY AND HEAT INPUT IN ARC WELDING

In arc welding process, heat input HI and arc energy AE are measures of how much heat input has been supplied to the job being welded. unit of HI is kj/mm or kj/in. If travel speed is in mm then unit will be kj/mm

arc energy AE  =  60VI / 1000s

I   =  CURRENT IN AMPS

V  = VOLTAGE

 s  = TRAVEL SPEED OF WELDING

CALCULATE WELDING CONSUMABLE FOR A ITEM

HOW TO CALCULATE WELDING CONSUMABLE FOR Any  ITEM

FORMULA FOR CALCULATION OF WELDING CONSUMABLE -

W = A x e x L X 1/E

A = cross-sectional area of weld metal deposited
e = density (7.8gr/cm3)
L = length of welding (cm)
E = deposition efficiency (n)           for SMAW- 0.55 to 0.80
                                                              MIG- 0.95
                                                           FCAW- 0.90
                                                             SAW-  1.0

FOR EXAMPLE A WELD OF L= 100 CM AND SINGLE V GROOVE AND ROOT FACE F= 3MM, ROOT GAP R= 2MM, BEVEL ANGLE 60 DEGRE, PLATE THICKNESS T=10MM
PROCESS = SMAW

WELDING POSITION EN ISO

WELDING POSITION AS PER EN ISO- 6947:2011

KEY:

PA          flat position

PB          horizontal vertical position horizontal position

PC          horizontal position

PD          horizontal overhead position

PE          overhead position

PF          vertical up position

PG         vertical down position

PH         pipe position for welding upwards    
PJ           pipe position for welding downwards

                                                                                                                                 

 

                                                                                                                     

                                                                                                                         

                                                             

SAW WELDING

WHAT IS SAW WELDING, TYPES, USES, AND ITS ADVANTAGE AND DISADVANTAGE

In this process, an arc is maintained between a continuously fed bare wire electrode and the workpiece underneath a mass of fusible granular flux. The flux is dispensed over the joint area and the wire is fed into it.  The arc which forms melts a proportion of the flux, which protects the weld pool from atmospheric contamination, shields the remaining unmelted flux acts as a shield for the arc itself.  The power source may provide either alternating or direct current.   Highest deposition. rates are obtained with electrode negative, but control of bead shape and penetration is better with electrode positive.