Welding instructions

Welding instructions

Welding Instructions: WPS (Welding Procedure Specification) and the purpose of setting WPS is to specify the details of the welding process of a piece or a desired material that is used for metal structures of AWS D1.1 standard and for pressure vessels ASME Sex IX.

A prerequisite for starting any welding activity is the provision of WPS. Setting WPS according to AWS D1.1 standard: The following form is for submitting WPS (SMAW and GTAW welding processes) according to the mentioned standard.

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After confirming each WPS, it is necessary to perform tests on the workpiece after welding and preparation of a test sample to determine and confirm the accuracy of the WPS. These results are entered in a special form called the PQR (Procedure Qualification Record). In the AWS D1.1 standard, if the connection scheme related to the PREQULIFIED section is used, there is no need to perform PQR anymore, because these connection plans have already passed the relevant tests and are approved. There are three variables in each WPS, which are:

Essential Variable

Non-Essential Variable

Supplementary Variable

1. Basic variables: Any change in these variables requires writing a new WPS. (Such as: materials, welding process, heat treatment, pre-cream, etc.)

2. Non-essential variables: Any change does not require a change in WPS. (Such as: electrode diameter, etc.)

3- Complementary variables: If the requirements of impact testing are provided, these variables will become basic and the conditions of paragraph 1 will apply to them.

Set up WPS according to ASME Sec.IX standard:

The following form to submit WPS based on ASME Sec. IX.

  

ASME Sec.IX is divided into QW and QB. QW stands for Qualification Welding and QB stands for Qualification Brazing. In this article, we will only describe the QW welding section, which is divided into 5 sections.

QW-100 General introduction to testing requirements etc.

QW-200 Procedure qualification details.

QW-300 Performance qualifications (welder approvals) details.

QW-400 Welding data .This is the biggest section of the code and covers data for both procedure and

Performance qualification. It includes:

-Material and consumable data

-Approval range for thickness, diameter, joint

-Configuration and welding positions.

-Definitions used in code.

QW-500 Standard Welding Procedure Specifications (SWPSs

(Welding Process es)

Process or processes used for welding:

Code QW-401 mentions the welding process as the main variable. The procedure for selecting the welding process is related to the following steps.

Step 1: Check the required connection features

At this stage, whether the weld is large or small, the welding position and direction, and the thickness of the base metal should be checked.

Step 2: Match the required connection characteristics with the welding processes

Most welding machine manufacturers provide a variety of information regarding the features and capabilities of their machines

They can be used. This step can be one or more processes depending on the characteristics of each device and the characteristics of each process

Select the type that provides the specified specifications for the connection. In this case, it rarely happens that there is only one process

Be selected and usually two or more processes provide the desired characteristics.

Step 3: Prepare a checklist to determine the ability of the selected processes to adapt to specific working conditions

Other parameters, in addition to connection, also affect process selection. Many of them are specific to work and workshop conditions

They are your welding. Sometimes these parameters have a great impact on the elimination of some selected processes. At this point it should be all

Checked these parameters and checked them one by one.

Step 4: Review the process with the welding machine manufacturer’s information to confirm its capability

At this stage, a checklist should be prepared and the required characteristics should be reviewed with the representative of the welding machine to

Ensure the ability of the device and the correct choice.

The names of some of the welding processes are as follows:

SMAW = SHILD METAL ARC WELDING Arc welding with capped electrode

GMAW = GAS METAL ARC WELDING Arc welding with shielding gas

GTAW = GAS TANGESTAN ARC WELDING Welding with tungsten electrode and neutral gas

SAW = SUBMERGED ARC WELDING Submerged arc welding

And……

(Type) How the welding operation process

 

Different methods of applying a welding process can be manual (MANUAL), automatic (AUTOMATIC), semi-automatic (SEMI-AUTOMATIC) or machine. Arc welding with coated electrode is considered manual and GMAW welding is semi-automatic It counts. And if their peak is placed on the device and moves automatically, it is called automatic or machine.

JOINT DESIGN

 

Specifications of the connection design in which the welding method is written. The most common connection designs are:

1. BUTT WELD head-to-head or butt connection

2. T-JOINT connection

3. LAP JOINT

Backing

Depending on the design conditions and in order to prevent oxidation of the weld melt, not to spill the melt from behind the weld, to ensure that it is not empty or

Weld burns on the back of the weld, etc. Metal straps, gas flow or flux are used as the back strap.

Type and material of backing material (Backing Material Type)

If the previous part is approved, ie the need to use the backrest, the material and type of materials required for the backrest is required.

. Materials that are mainly used as backrests are:

A- Plain carbon steel belts B- Copper sheets

C – flow of shielding gases such as argon gas or CO2 T – flux or boiling powder

Another thing that should usually be mentioned in WPS is drawing and displaying the sequence of welding passes (BEAD).

The choice of this sequence depends on the probability of distortion of the weld. But in the part of the connection plan after drawing the weld chamfer, the sequence

Welding Passes must be drawn together with numbering. Welding designs that are used in terms of sheet sex and type of electrode

They are similar and therefore covered by a WPS. They must be drawn separately and their pass sequences shown.

To be.

Base Metals

Mentioning the type and chemical composition of the weld metal is one of the most important things to mention in WPS. This is in the choice of others

Welding process specifications such as preheating, reheating, electrode selection and work technique are involved.

P No.

Base metals under a numerical name called P No. Are divided. If an impact test is required to check the quality of the steel, the classification is more detailed and Group No. Is also raised. The basis of the above divisions is the alloy composition, weldability and mechanical properties. To see a group from P No. It is necessary to see the code QW-422.

Note: In ASME standard, materials are marked with SA letters (according to ASME Sec.II Part A&B standard)

In QW-420.2 with the letters S No. We will face. If the metal is approved in ASME code B31 or other parts of the standard but is not present in ASME Sec.II standard, then S No. will be used.

Thickness Range

The thickness of the welding section is mentioned in this section. According to the code QW-451.1, the following thickness range can be used to reduce the number of WPS:

A-thickness less than 1/16 inch (1.6 mm)

 

 

Pipe Diameter Range

If the part to be welded is a pipe, in addition to mentioning the thickness range, it is necessary to mention the diameter of the pipe to be welded in this part of WPS.

Be. The diameter range is specified by code QW-452.3.

Filler Metal

Basically, in most welding processes, we need a metal interface to make the connection between the base metals. The metals used for this purpose are

They are known as filler metals. Select the most correct filler metal by considering the welding process and various effective parameters

The parameters for the correct choice of filler metal are:

A) Welding process

B) The chemical composition of the base metal

C) Welding condition

D) Application conditions

E) Weld penetration rate (penetration depth)

C) Quality of the welding site

G) Welding cost

H) Welding skills

According to QW-404, the specifications of filler metal in different parts of the WPS form sample are as follows:

* (F No. (Filler Metal Number

F No. It is a classification for electrodes mentioned in QW-432 in the tables.

* (A No. (Analyze Number

A No. Applies only to ferrous alloys. A is extracted and inserted according to code QW-404.5.

* Specification number of filler metal (Spec. No)

About thirty numbers are assigned by the AWS to classify the filler metal specifications. This classification is specified in the ASME standard by the letters SF.

* Class and standard number of AWS electrode (AWS No. Or Class No)

There are various standards for naming electrodes. The E XXXX format is used to name the coated electrodes of class A5.1.

* Size of Electrode

To do the most economical welding, choosing the size of the electrode (diameter of the brain rod) is as important as choosing the type of electrode. The following are considered in the selection of the following: connection design, thickness of welding layers, welding mode, heat tolerable by the part and the skill of the welder. The general rule is that you should never use an electrode that is larger than the thickness of the workpiece. The thick electrode was used for vertical or vertical welding or an electrode larger than the thickness of the workpiece. The thick electrode is not suitable for welding in vertical or vertical and overhead or ceiling K or V position, because it is difficult to control the large welding pool in these conditions. In the case of welding thick sheets with prepared edges, the first welding pass is done with a thin electrode and the next passes are done with thicker electrodes.

* Deposited Weld Metal Thickness Range

In this part of WPS, the thickness range of the deposited weld metal is entered, in which the change is defined based on QW-451.

Flux Class

Any specifications and standards related to submerged arc welding fluxes in accordance with SFA 5.17 for electrodes for electrodes and simple carbon steel fluxes and SFA 5.23 for electrodes and low alloy steel fluxes are listed in this section.

Other

The brand name, manufacturer code or other specifications of the filler metal and the consumable pad are mentioned in this section.

Welding position (Position)

Welding can be done in four general situations:

1) Flat bed

2) Horizontal horizontal

Vertical (3 vertical

Overhead (4 top series

The welding status code is listed in QW-405. The QW-461 code lists various welding situations.

Position of Groove or Fillet weld

Welding status depends on: type of welding process, accessibility of welding lines, dimensions and size of the workpiece, construction method and available facilities.

Welding Progression

In this section, the welding direction is mentioned, which is mainly for vertical welds from the bottom to the top (UP-Ward).

Preheat

The workpiece is usually preheated before welding to prevent bursting, complexity and distortion, unwanted phases, etc. Welding operations, temperature control between passes is also required to prevent the workpiece temperature from falling below the preheating temperature and rising above the allowable limit – Tempering temperature. This action is controlled by thermal plasters. These conditions can be applied by referring to code QW-406.

Post Weld Heat Treatment (PWHT)

You can perform the above operation by referring to QW-407 code.

Gas

One of the important functions of shielding gas is to protect the molten pool from atmospheric pollution. The specifications of the shielding gas in this part of WPS are based on the code QW-408.

Shielding Gas

Gases N2, He, Co2, Ar, or a mixture of these gases are used for protection.

Flow Rate song

The gas flow rate is measured in liters per unit time and should be adjusted in such a way that in addition to fully protecting the melt pool, it does not cause severe mixing of the melt and leaving the pool. The rate of gas flow depends on the nozzle diameter and the shape of the weld.

Electrical Characteristics

A change in the type and polarity of the electric current, an increase in the input heat, or an increase in the volume and amount of weld metal deposited per unit length will cause a change in the quality of the weld. Also, the amount of weld metal is proportional to the increase in the size of the weld or decrease in the length of the weld line per electrode. Electrical specifications are in accordance with QW-409.

Current type (Current AC / DC)

Some electrodes work in AC current and some in DC current. If DC current is mentioned, the type of polarity must also be specified.

Polarity

If DC current is selected, the polarity must also be specified. Polarity can be straight or inverted. And is as follows:

A) Electrode connection to the positive pole in DC DCEP current: Direct Current Electrode Positive

DCRP: Direct Current Reverse Polarity

B) Electrode connection to negative pole in DC DCEN current: Direct Current Negative Electrode

DCSP: Direct Current Straight Polarity

Current intensity (Ampere)

Depending on the type of process, the diameter of the electrode, the speed of movement, the amount of penetration, etc., the intensity of the current is determined.

Voltage

The voltage of the device is usually measured as an open circuit.

Tungsten Electrode Size and Type

In the GTAW process, the tungsten electrode is unusable. Due to the high melting point, this electrode does not melt during welding.

Technique

The technical points of the welding method are based on the code QW-410.

String or Weave Bead

In this part, the shape of the desired pollen (nut) is mentioned. In cases where thin pollen is sufficient or the lowest heat applied to the part is required, strip pollen is used because the speed of hand movement is higher in this technique. Woven pollen is executed in circular, crescent, 8 shapes.

Orifice or Gas Cup size

In shielding gas welding processes, it is necessary to mention the above.

(… Initial and Interpass Cleaning (Brushing,…) {Initial and Interpass Cleaning (Brushing,…)}

Cleaning the surface before welding The surface before welding, such as removing rust, oxides, grease and dirt from the part, increases the quality of the weld. Also, during multi-pass welding operations and at the end of the work, cleaning the surface, including cleaning slag, etc., will reduce and eliminate welding defects such as slag trapped in the melt.

Method of Back Gouging

If welding is required from behind the weld, it is necessary to first remove the first weld pass from the back of the connection by one of the following methods:

A) Arc from carbon arc electrode Electric Arc gouging

B) Oxyfuel gouging by flame removal

C) Grinding and Chipping

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