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1. P No And F No In Welding Electrodes
2. P No And F No In Welding Equipment
3. P No And F No In Welding Machine

This article provides information about F number in WeldingProcedure Specification based on the requirement of ASME Code Section IX.

The F number grouping of filler metals refers to theirsimilarity on their usability characteristics. The usability determines theability of a welder to deposit a sound weld metal with a certain filler metal.

The F number is essential variable in the most weldingprocess for welding procedure specification and also in welding performancequalifications. Like the P number, the Fnumber designed to reduce the number of procedure qualification and weldingperformance qualification.

I have seen some many people confusing about F number andbelieving the F number is grouping for the similar chemical composition. Thisis not true, and F number is only about of usability characteristics such aswelding position.

F number in Welding Procedure Specification

P number in Welding Application The assigned P Numbers to the materials addressed in the table QW-422. In addition, you can find minimum specified tensile strength, group number, UNS number, ISO 15608 Group number, nominal composition and product form. P number is essential variable for most welding process. Similarly it is an essential. Welding Journal The authority in metal fabrication for 90+ years. The Welding Journal has been published continually since 1922 — an unmatched link to all issues and advancements concerning metal fabrication and construction. Each month the Welding Journal delivers news of the welding and metal fabricating industry. Stay informed on the latest products, trends, technology and events via in. Things to know prior to qualifying a welding procedure Know the application for the welding procedure What welding process(es) are going to be used during construction What materials are going to be used during construction The types and grades The thicknesses of each material Are there dissimilar welds including welds between different P-No. P number 1 Group number 2. P number 1 Group number 3 Now you need your welding procedure, be qualified by impact testing as well. One set for weld metal and one set for heat affect zone. In this situation, if you have WPS that has been qualified for P number 1 and Group number 1 cannot be used for another job with P number 1 and group number 2.

Table QW-432 in ASME Code Section IX provides the list of Fnumbers. Any change from one F number in welding to the other F number is essentialvariable in the welding procedure specification. The changing from one F numberto other F number is a little bit different in welding performancequalification. The essential variable tables in welding performancequalification (QW-352 thru 357) refer you to the QW-433 for the range of qualification.

For example, a welder qualified with F number 4, he alsowill be qualified on the F numbers 1, 2 and 3.

Some contractors use the essential variable tables (QW-352thru 357) to minimize their costs. For instance, they might test the welder forstainless steel material by using carbon steel material. Consider the actualproject material is stainless steel and you do not want to waste stainlesssteel material for testing. You ask the welder to weld in carbon steel materialbut with stainless steel filler metal. Based on the essential variable table Pnumber 1 (Carbon Steel) qualifies P 8 (Stainless Steel), and the F number isthe same. So you qualify your welder for stainless steel material by usingcarbon steel material but stainless steel filler metal.

When you have a welder or welding operator with a certainqualification, and you want to use him in some other job, you need to see ifall the variables in the essential variable table confirm his qualification forthe new job. Each of the item in the table has veto right, if 6 out of 7 is Ok,but only 1 of them is not meeting the requirements, and then you cannot usethat welder in the new job and you need to re-qualify him by the new test.

The ASME Section IX Training Course is 2 days video training course and available online and the student that successfully pass the exam, receive I4I academy certificate with 16 hours training credit.

Related Links:

Nonessential Variables, Supplementary Essential Variables, A number in WPS

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P No And F No In Welding Electrodes

Have you heard of post weld heat treatment (PWHT)? Of course you have. If you are involved in welding you have definitely heard this term. But what is PHWT? When is PWHT required? What temperature should PWHT be done at? Heat treating of materials can be a very complicated subject, but when it comes to heat treatment after welding it boils down to a simple concept: PWHT is done in order to maintain or improve material strength and mechanical properties and to relieve residual stresses. In steel fabrication, the most common PWHT procedures applied are post heating and stress relieving.

When we weld, we introduce enough heat to melt the base material. This elevated temperature causes microstructural changes to the base material which can change very important material properties such as tensile strength, hardness, ductility and toughness. The degree to which these properties are affected depends on the chemical composition of the base material and the cooling rate after welding. PWHT treatment requirements are typically dictated by codes and standards and by any special requirements due to the service conditions of the welded structure.

For steel fabrication the use PWHT is driven by the need to resist brittle fracture via post heating and to reduce residual stresses via stress relieving.

Post heating is primarily done to avoid hydrogen induced cracking (HIC), also know as cold cracking and hydrogen assisted cracking (HAC). In order for HIC to occur three things must be present:

P No And F No In Welding Equipment

1. A susceptible base material microstructure (usually due to high levels of carbon)
2. Threshold level of hydrogen
3. Elevated stress levels (internal or external)

For more detail on this topic you can read Factors Influencing Hydrogen Induced Cracking.

If you eliminate one of the three things above, hydrogen induced cracking will not take place. Post heating allows hydrogen to diffuse out of the weld and heat affected zone (HAZ), thus reducing diffusible hydrogen below the threshold level. For more information on preventing HIC read Preventing Hydrogen Induced Cracking.

The weld should not be allowed to cool to room temperature before post heating. HIC will occur once the material temperature drops below 200F. Before this happens the part must be heated to a specific temperature and held for a specific amount of time which depends on the material type and thickness. This allows hydrogen to diffuse out of the weld and prevent cold cracking upon reaching room temperature.

P No And F No In Welding Machine

Codes and standards will specify temperatures and holding times. In general, you must heat the part high enough to allow hydrogen to diffuse out of the weld and HAZ but not high enough to create any type of microstructural change. Typically, this bake out procedure is done between 300˚F – 600˚F [149˚C – 316˚C]. This temperature is held for at least 1 hour per inch [25mm] of material thickness. Always consult the code you are working with or the engineer in charge before developing your own post heating procedure.

Charts showing post heating and PWHT temperatures and holding times should be included with all WPSs. An example of this type of chart is shown below.

Sample PWHT chart for P91 steel. Actual temperature and holding times are determined by material composition and thickness.

Stress relieving is the other common purpose of applying PWHT. Stress relieving is done at a much higher temperature and usually for a longer period of time than post heating. Stresses can develop in weldments due to high levels of restraint and shrinkage forces. These stresses may not cause the part to crack right away, but significantly reduce the fatigue life of the welded structure or component.

Stress relieving will reduce these residual stresses that are present after welding by carefully controlling the heating of the part to a specific temperature, holding it for a specific amount of time and then controlling the cooling rate. Unlike postheating, the temperatures for stress relieving are much higher. For most carbon steels stress relieving is done at 1000˚F – 1400˚F [538˚C – 760˚C].

Other than relieving stresses, PWHT provides other benefits: tempering, hydrogen removal, improved ductility, toughness and corrosion resistance. However, be aware that PWHT can also have damaging effects if done improperly or done on materials that should not be post weld heat treated.

Exceeding the stress relieving temperatures can reduce tensile strength, reduce creep strength and reduce notch toughness. Additionally, some steels should not be post weld heat treated or at least it is not recommended. AWS D1.1 Structural Welding Code (Steel) states that stress relieving the following common structural steels is not recommended:

• ASTM A514 (commonly referred to as T-1 steels – Arcelor Mittal trade name)
• ASTM A517
• ASTM A709 Grade HPS 100W
• ASTM A710

It is worth restating that any PWHT must be done according the specific code or standard that governs the fabrication of the structure or component. Even though PWHT is done after welding it forms part of the welding procedure specification (WPS) and clear instructions must be shown in this document on how to perform the PWHT.

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