Welding Electrode Manufacturing Process

Welding Electrode Manufacturing

Production Of Covered Electrode

Welding Electrode Manufacturing is a complex process that should be divided into different steps: Wire Drawing and Cutting, Powder Mixing, Coat Covering, Baking. it is also important to know the details about the Pre-In-After Quality Control Process. By considering these steps, WESPEC systematically describes the production process from the beginning to the end. also, you can find the list of welding electrodes that can be produced by you with WESPEC.

1)Plant Design for Welding Electrode Manufacturing:

WESPEC can design a welding electrode manufacturing plant based on your requirements. This plan will include a detailed calculation of all your requirements for the production of the best quality product. The main topics are as below:

 

1-Factory design and construction (land and buildings)

2- Power requirements (electrical, gas, water)

3-Determine the machine needed and design of plant lay out

4- Specify laboratory equipment required or outsourcing.

5-Specify the equipment needed to carry

6-Man power requirement

 

Note: If you already have a welding electrode factory, WESPEC can help you produce a quality product depending on your capabilities.

2) Review relevant production standards:

It is necessary to find out what are the standards for determining the quality of a welding electrode. This is because we guarantee the final quality of the product and its compliance with relevant standards.

For instance E308L-15 has these relevant standards as follows:

Welding Electrode Standard Code

Stainless Steel Welding Electrodes

3) Review relevant formulation & specification of Welding Electrode:

Each welding electrode has its own production formulation (FIG I1).also each raw material in Welding Electrode Manufacturing at this formula has its own spec sheet. 

Welding Electrode Manufacturing Formula

Formula & Construction Sheet

3-1) Wire : The exact specifications of the wire required include chemical analysis and the maximum, minimum, typical values of each element of the wire are shown in spec sheet.

Specification of the Wire

Core Wire Specification as a Raw Material in Production of Welding Electrode

3-2) Powder: Each Welding Electrode can contain an average, 10 to 20 types of mineral, chemical, metal, and ferroalloy. The specification sheet of each powder contains detailed properties of the powder, including chemical analysis, sieve analysis, density, humidity are shown in the figure.

Specification of the Powder

Powder Specification as a Raw Material

3-3) Binder: The main task of the binder is to paste the required powder coating on the wire surface of the Welding Electrode. This group of materials is mainly from sodium and potassium silicate compounds. The specification sheet of the raw materials contains precise properties including chemical analysis, density, viscosity, molar ratio, and Baume in the figure.

Specification of the Binder

Binder Specification as a Raw Material in Welding Electrode Production

4) Prepare of Raw Material based on spec

WESPEC knows the qualified raw material suppliers for Welding Electrode Manufacturing from around the world. We can help you in purchasing raw materials based on our patent.

5) Qc of Raw Materials for Welding Electrode Manufacturing

It is necessary to test materials before welding electrode manufacturing. All the materials need to be tested and each item of results should compare with its specification range. each number inserted in this sheet will compare with the related spec.

Final QC sheet of Raw Materials

Quality Sheet of Raw Material

Required tests are classified into main four groups

5-1) Chemical analysis:

Different methods are available to determine the quantitative and qualitative analysis of the elements and compounds present in the raw materials(e.g. figure E and Z2):

•XRF

•XRD

•Atomic Absorption

•Carbon/Sulphur

•Oxygen/Nitrogen

•ICP

 

5-2) Grain size test (sieve analysis):

After acceptance of chemical properties, the other parameters which have a very important effect on the quality of the powder is grain size. Different methods are available to control the grain size. For coarse powders, sieve analysis is used while for fine powders, laser particle size method is common (Figure F). The result will be evaluated by the grain size graph ( figure I).

 

5-3) Physico-chemical tests:

Other parameters that affect the quality of raw materials are as follows

(if needed on the spec sheet)

•Density &Bulk density

•LOI (loss of ignition)

•ASH

•Humidity or moisture (physical water & chemical water)

•Stabilize range (SR)

•Viscosity

•Baume

•Molar ratio

 

As a  sample, the moisture parameter of the covered electrodes as physical water (water that releases in 120 .c)

For basic electrodes like E7018, it should be less than 0.4 % wt. in contrast for Cellulosic electrodes like E6010 It should be more than 4% wt. This item is also important for fluxes , which will be described in the relevant section (Figure H).

In addition, Viscosity and Baume are the parameters that are important for binders. They should control by special equipment (figure G).

Stabilize range is another parameter that is critical for some powders such as low carbon ferromanganese. It is measured by specific methods through the amount of gas released and discoloration.

 

5-4) Mechanical tests:

These types of tests are used to determine the mechanical properties of primary coiled wire.  

(figure J0).

6) Welding Electrode Manufacturing Production stages:

Welding Electrode manufacturing Flowchart

Welding Electrode Manufacturing Flow Chart

6-1) Drawing, Straightening, and Cutting:

The primary feed for Welding Electrode Manufacturing as well as welding wires is metal coils. These coils are mainly produced by the hot rolling method from ingots produced in the steel plant. (figure F1).

Coiled wires have different encodings in standards. These coils are classified into (non-low-medium-high) alloy steel groups as well as stainless and non-ferrous steel such as nickel, aluminum, cobalt, etc.

Fig F1

Manufacturing of Hot Rolled Cored Wire

Coiled wires have different encodings in standards. These coils are classified into (non-low-medium-high) alloy steel groups as well as stainless and non-ferrous steel such as nickel, aluminum, cobalt, etc.

The SWRY11 wire in the GIS standard is one of the most widely used wires that can be used in the production of many electrodes, including E6013,E7018,E7024,E6010. Initial coils are usually pulled in one or two ton weights. The general steps of the stretching process are illustrated in (FIG C1-1) and flowchart.

FIG C1-1

Core Wire Manufacturing Flow Chart for Producing of Covered Welding Electrode

In recent years, with the development of technology, drawing machines have various mechanisms that have led to the improvement of the quality of the final wire. In general, dry drawing  is used in electrode production plants. In addition, methods such as acid cleaning, mechanical cleaning and washing in the detergent tub, or ultrasonic cleaning before or during process, are used to eliminate wire surface contamination (Figure D1).

FIG D1

Wire Cleaning Method

As mentioned before, The reduction of the wire diameter is accomplished by wire drawing machinery. For example, in the SWRY11 wire drawing process to produce E7018 electrodes with a final diameter of 2.5, the desired final diameter can be achieved by 6 steps of drawing. It is also necessary to use different lubricants to reduce the amount of dies friction with the wire and ease the drawing process and extend the service life of dies.sodium and calcium lubricants are widely used in the process of wire drawing (Figure E1).

Once the wire reaches the proper diameter, the wire straightening process is performed. The resulting wire must be free of any bending and deflection. The final step is to cut the wire along the desired length. the lengths of the wires are usually 350 and 450 mm.

FIG E1

Die and Lubricant in Wire Drawing

6-2) Dry & Wet-mixing

At this stage, all approved powders in the warehouse are weighted according to the formulation by the manual or automatic system and then enter the dry mixing stage. The wet mixer can be separated from the dry one or use only one mixer for both stages.

The duration of the dry mix depends on the type of mixer and the nature of the formulation. For groups of formulas, the long mixing time will lead to the adhesion of the materials and And leads to mixed failure. However, in a group of electrodes such as cellulosic electrodes, due to the very different physical nature of the cellulose powder with metal powders such as manganese, special attention should be paid to the mixing conditions to achieve Homogeneously mixed flux.

The wet mix is accomplished by adding a precise amount of binder and water to the dry powder mixture. The time of dry and wet mixes is given in the electrode manufacturing instructions ( Fig I1). The output of this step is a paste-like flux.

FIG I1

Formula & Construction Sheet

6-3) Extruder

Depending on the type of extruder, the mechanism of production at this stage will be as follows:

 

6-3-1) Vertical extruder

In this machine, the paste enters the cylindrical vertical chamber which will be directed to the extrusion die location. The advantage of this method is that more paste will be used at a single charge of the device, which will speed up production.The problem of this method is that at low rates production.

 

6-3-2) Horizental extruder:

In this method, the paste from the wet mix is first inserted into the briquetting slug press and then prepared briquette will charged into the horizontal extruder.

The advantage of this method is low rate and higher precision of production and its disadvantage compared to the previous one is low speed production. Because unlike the previous method the briquette making  is also required before the extruder unit.Types of electrode extruder machineries (figure H1).

 

6-3-3) Mechanism of Cover Pressing on Wire:

In general, the performance of all extruder machines is the same but there are differences between paste feeding.All of these devices are operated by die proportional to the size required, and the force applied to the die in the extruded chamber with outlet nozzle. An overview of this process based on the type of coating. (figure H1-1).

FIG H1

Covered Electrode Extruder Types

FIG H1-1

Cover Pressing Methods in Welding Electrode Production
Double Coated Welding Electrode Manufacturing

As shown above, there are two types of extruders for Welding Electrode Manufacturing, The mechanism of operation of these two models is the same.at these machines by applying the pressure behind the flux, the coating process is performed on the wire surface.

The difference between the two models is the applied force on the flux. In the screw model, the applied force is low and it is possible to produce simple electrodes like E6013 in high capacity. but in hydraulic system extruders, the applied force on the flux is made by hydraulic force and capable to produce special electrodes. 

The hydraulic extruders are designed in two types: vertical and horizontal .in the vertical model the capacity is more than horizontal type but has some problems in the production of several models of covered electrodes.

In the figures below, the types of horizontal and Vertical hydraulic extruders are shown:

Horizontal extruders type 1 (Top View)

Welding Electrode Manufacturing Machine Horizontal Type 1

Horizontal Extruder Type 2 (Top View)

Welding Electrode Manufacturing Machine Horizontal Type

Horizontal Extruder Type 3 (Top View)

Welding Electrode Manufacturing Machine Horizontal Type

Vertical Extruder (Side View)

Welding Electrode Manufacturing Machine Vertical Type

After the extrusion process on the wire, the pressing force throws the  electrode on conveyor, running the electrode forward, and first the concentricity of the coating is controlled by the operator with specific testing machine (Fig J1).The product then enters the tip and nip brushing unit and  then guided to the printing unit (Fig K1-1).

FIG J1 & k1-1

Concentricity Checking and Brushing and Printing of Covered Electrode

At the end, the electrode is  placed on the carriage for rest and transfer to the furnace or directly into the furnace via the same conveyor.These manufacturing methods will be performed in accordance with their own instructions.

The importance of the physical properties of the electrode such as the concentricity of the wire and the geometry of the electrode tip and nip and the other parameters is very important in the final quality of this product. All of these parameters are listed in the Physical Specifications Sheet of the electrode for each product.(Fig L1)

FIG L1

Characteristic of Welding Electrodes

6-4) Baking

The important issue in the baking of welding electrode is that the importance of uniform baking in all coating distances from the core wire. For example, in the case of incorrect baking, it causes the electrode surface to bake but does not occur in the substrates. Therefore, electrode baking can be similar to baking a cake(figure H15). Each electrode requires a different baking method depending on its nature, actually, it depends on the nature of the coating.

As a sample, the basic electrode needs to stay in the air prior to entering the furnace and have primary drying, while the rutile electrodes can be inserted directly into the furnace. stainless steel electrodes, also need to bake at different temperature and time based on the time and temperature graph. Each of these electrodes has different baking instructions that can be adapted to all types of ovens.

Another set of furnaces have different temperature zones. This method, also known as baking baguette, involves a tunnel furnace that enters the electrode at different temperature zones as it moves through the furnace(FigureM1).

FIG M1 & H15

Welding Electrode Baking

6-5) Packing

After baking, the products will be ready for packaging and delivery to the customer. The electrode packaging will vary depending on their nature. For example, cellulosic electrodes require metal cans that can keep coating moisture.

basic electrodes are packed in completely different conditions in order to prevent moisture penetration, their packs usually are sealed and resistant to any moisture and atmospheric conditions. Another group of electrodes, such as rutile electrodes, are packaged in cardboard cartons and plastic laminates because of the less importance of the moisture problem than basic electrodes. another group of electrodes will vacuum because of the sensitivity of the coating to the impact(Figure N1).

FIG N1

Welding Electrode Packing

7) Verify the Quality of the Finished Product:

A very important issue in the Welding Electrode Manufacturing process is the quality plan. this instruction involves all steps. This control is performed at all stages before, during and after production Summary of this quality plan is as follows:

Quality Plan sheet for Welding Electrode Manufacturing 2
Quality Plan Sheet for welding electrode manufacturing 3
Quality Plan Sheet for welding electrode manufacturing 4
Quality Plan Sheet for welding electrode manufacturing 5
Quality Plan Sheet 1
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The tests used to verify the quality of a product are divided into two groups:

1-Tests defined by standards

2-Tests defined by the manufacturer

7-1) Tests defined by standards:

Valid global standards for each product provide precise definitions of the tests required and the range of accepted results.(see figures below for stainless steel covered electrode E308-L15,defined by AWS standard)

FIG N1

Required Tests for Quality of Stainless Steel Welding Electrode according to AWS

FIG N1

Necessary tests for quality accuracy of Stainless steel welding electrode

7-2) Tests defined by the manufacture 

Each manufacturer, in addition to trying to get the test results in the standard optimum range, tries to add features to the product as per the customer’s requirements and also design tests based on these features.

7-3) Final Product Tests:

At this stage it is necessary to perform all tests defined in the relevant standards as well as defined tests in special conditions. Different groups of welding electrodes are classified in many standard systems. Among the most important international standards for different welding electrodes are AWS-ISO-DIN-EN-BS (see figures below) :

AWS Test Sample

AWS Tests for Weld Metal

DNV GL Test Sample

DNV-GL Tests for Weld Metal

Tensile & Impact Tests

NACE Test for Weld Metal

7-3-1) Humidiry of Electrode Covering:

The moisture content of the electrode after the final sintering as mentioned above is a very important qualitative parameter. For example, the moisture content of basic electrodes should always be below 0.6%, generally the presence of moisture is harmful, while the cellulosic electrodes require a moisture content above 4%. This item is commonly referred to H2O 120 (physical water that exits at 120 ° C) and H2O 1000 (chemical water which exits at 1000 ° C).

7-3-2) Welding Performance and Visual Test:

This test examines welding in different parameters such as shape of beads, penetration rate, convexity and concavity of weld, slag detachment, porosity, gas holes, undercut, spatter ,etc. The qualitative properties investigated in this test will vary greatly depending on the type of electrode. For example, low spatter and slag separation are important in basic electrodes, whereas in cellulosic electrodes, the penetration rate is much higher and more important. the control properties of welding according to the type of electrode are among the documents of quality control unit. (Figure P1).

FIG P1

Visual Testing of Weld

7-3-3) Destructive and Non-Destructive Tests:

As mentioned, each electrode has its own quality parameters defined in related standard . The standard also provides definitions of the limits for test results and how to perform.These tests are described below:

 

7-3-3-1) Destructive test of weld metal:

.Tensile test 

.Impact test 

.Hardness test 

.Bend test 

.Wear test 

.Fatigue test

.CTOD

.Hydrogen tests 

Tensile & Impact Tests

Tensile and Impact Test of Weld

Hardness Test

Hardness Test of Weld

Bend Test of Weld

Bending Test of Weld

Wear Test of Weld

Wear Test of Weld

Hydrogen Test of Weld

Hydrogen Test of Weld Metal

7-3-3-2) Non Destructive test of weld metal:

.VT

.PT

.MT

.UT

.RT (figure S1&S1-1)

FIG S1-1

Radiography Testing of Weld

FIG S1

Radiography Test Result of Weld Metal

7-4) Chemical and phase analysis of weld metal:

.XRF (figure Z1).

.XRD

.CS (Carbon & Sulphur).

.Atomic  Absorption.

.ON (Oxygen & Nitrogen )

.Spectrophotometry (figure Z1)

FIG Z1

Chemical Analysis of Weld Metal

7-5) Microstructural study tests:

.Microstructural study with light microscope (FIG N20)

.Microstructural study with SEM (FIG N30)

.Microstructural study with TEM (FIG N40)

FIG N20

Light Microscope for Weld Metal

FIG N30

SEM for Weld Metal

FIG N40

TEM of Weld Metal

7-6) Corrosion and erosion tests

these tests are vary and only requires that are defined by the relevant standards or are able to pass these tests as required by the customer.

Welding Electrode Production Requirements

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