ASTM A672 EFW Steel Pipe | Electrofusion Welded Pipe

da admin / mercoledì, 06 Novembre 2024 / Pubblicato il TUBI

ASTM A672 Electrofusion Welded (EFW) Tubo D'Acciaio

Introduzione

ASTM A672 is a specification that covers electric-fusion-welded (EFW) steel pipes designed for high-pressure service at moderate temperatures. These pipes are commonly used in industries such as power generation, petrolchimico, olio e gas, and water transmission. The specification provides guidelines for the manufacturing, test, and inspection of steel pipes to ensure they meet the necessary mechanical properties and performance requirements for high-pressure applications.

The EFW process is a welding method that uses an electric arc to fuse the steel plates together, forming a longitudinal seam. This process is highly efficient and produces pipes with excellent structural integrity and mechanical strength. ASTM A672 pipes are available in various grades based on the type of steel used and the required mechanical properties.

This article will explore the manufacturing process, Proprietà meccaniche, and applications of ASTM A672 EFW steel pipes, as well as the testing methods used to ensure their qualità e prestazioni.

Sommario

What Is ASTM A672 EFW Steel Pipe?
Manufacturing Process of ASTM A672 EFW Steel Pipe
- Electric Fusion Welding (EFW) Processi
- trattamento termico
Grades and Classes of ASTM A672 Steel Pipe
Mechanical Properties of ASTM A672 EFW Steel Pipe
Testing and Inspection Requirements
- controlli non distruttivi (NDT)
- Test idrostatico
Applications of ASTM A672 EFW Steel Pipe
Domande frequenti (FAQ)
Conclusione

What Is ASTM A672 EFW Steel Pipe? {#what-is-astm-a672-efw-steel-pipe}

ASTM A672 is a standard specification for electric-fusion-welded (EFW) steel pipes designed for high-pressure service at moderate temperatures. These pipes are fabricated from pressure vessel qualità steel plates that are fusion welded using an electric arc. The specification covers pipes with a longitudinal seam and is intended for use in applications where high strength and durability are required.

Key Features of ASTM A672 EFW Steel Pipe:

Electric Fusion Welded (EFW): The pipes are manufactured using the EFW process, which involves fusing the steel plates together using an electric arc. This process produces a strong longitudinal weld that can withstand high pressures.
Recipiente A Pressione qualità In acciaio: The steel plates used in the manufacturing of ASTM A672 pipes are of pressure vessel quality, meaning they are designed to withstand high internal pressures without failure.
High-Pressure Service: ASTM A672 pipes are suitable for high-pressure applications, such as boilers, scambiatori di calore, and pipelines in the oil and gas industry.
Moderate Temperature Applications: The specification covers pipes designed for use at moderate temperatures, typically up to 400°C (752° F).
Various Grades: ASTM A672 pipes are available in different grades based on the type of steel used and the required mechanical properties. The grades are determined by the chemical composition and heat treatment of the steel.

Manufacturing Process of ASTM A672 EFW Steel Pipe {#manufacturing-process-of-astm-a672-efw-steel-pipe}

The manufacturing of ASTM A672 EFW steel pipes involves several steps, including the selection of pressure vessel quality steel plates, the electric fusion welding (EFW) Processi, and heat treatment to achieve the desired mechanical properties.

Electric Fusion Welding (EFW) Processi {#electric-fusion-welding-efw-process}

The EFW process is a type of arc welding that uses an electric arc to fuse the steel plates together along a longitudinal seam. Il processo prevede i seguenti passaggi:

Plate Preparation: The steel plates are first cut to the required dimensions and inspected for any surface defects or imperfections.
Edge Preparation: The edges of the steel plates are beveled to ensure proper fusion during the welding process. The bevel angle is carefully controlled to achieve a strong weld.
Electric Fusion Welding: The plates are positioned edge-to-edge, and an electric arc is used to melt the edges of the plates, creating a weld pool. As the arc moves along the seam, the molten metal solidifies, forming a continuous weld along the length of the pipe.
Weld Inspection: The weld is inspected for defects such as porosity, crepe, o fusione incompleta. Controlli non distruttivi (NDT) metodi, such as ultrasonic testing or radiographic testing, are often used to ensure the quality of the weld.
Sizing and Shaping: Dopo la saldatura, the pipe is passed through a series of rollers to achieve the desired diameter and roundness. The pipe is also inspected for dimensional accuracy.

trattamento termico {#heat-treatment}

After the EFW process, the pipes may undergo heat treatment to improve their mechanical properties and relieve residual stresses induced during welding. The type of heat treatment depends on the grade of the steel and the application requirements. Common heat treatment processes include:

Normalizing: The pipe is heated to a temperature above its critical point and then cooled in air. This process refines the grain structure and improves the toughness of the steel.
Quenching and Tempering: The pipe is heated to a high temperature and then rapidly cooled (quenched) in water or oil. It is then reheated to a lower temperature (tempered) to improve its ductility and toughness.
Alleviare lo stress: The pipe is heated to a moderate temperature and then slowly cooled to relieve residual stresses without significantly altering the mechanical properties.

Grades and Classes of ASTM A672 Steel Pipe {#grades-and-classes-of-astm-a672-steel-pipe}

ASTM A672 steel pipes are available in various grades and classes based on the type of steel used and the required mechanical properties. The grades are determined by the chemical composition of the steel, while the classes are based on the heat treatment and testing requirements.

Common Grades:

Grade B60: This grade is made from carbon steel with a minimum tensile strength of 415 MPa (60,000 psi). It is commonly used for moderate-pressure applications.
Grade C65: This grade is made from carbon-manganese steel with a minimum tensile strength of 450 MPa (65,000 psi). It is suitable for higher-pressure applications.
Grade C70: This grade is made from carbon-manganese steel with a minimum tensile strength of 485 MPa (70,000 psi). It is used in high-pressure applications where strength and durability are critical.

Classes:

Classe 10: Pipes in this class are supplied in the as-welded condition without any heat treatment.
Classe 12: Pipes in this class are heat-treated after welding to improve their mechanical properties and relieve residual stresses.
Classe 22: Pipes in this class undergo quenching and tempering to achieve higher strength and toughness.

Material Specification {#material-specification}

ASTM A672 pipes are made from pressure vessel quality steel plates that are welded using the electric fusion welding (EFW) Processi. The specification covers pipes in various Gradi e classes, which are determined by the Composizione chimica of the steel and the trattamento termico applied after welding.

Key Features of ASTM A672 EFW Steel Pipe:

Electric Fusion Welded (EFW): Pipes are welded using an electric arc to fuse steel plates, creating a longitudinal weld.
Pressure Vessel Quality Steel: The steel plates used are of pressure vessel quality, ensuring the pipes can withstand high internal pressures.
High-Pressure Service: ASTM A672 pipes are designed for high-pressure applications at moderate temperatures.
Grades and Classes: The specification provides multiple Gradi e classes based on the Composizione chimica e trattamento termico of the steel.

Chemical Composition Table {#chemical-composition-table}

The chemical composition of ASTM A672 steel pipes varies depending on the Grado of the steel used. The table below outlines the typical chemical composition for common grades used in ASTM A672 pipes.

ELEMENTO	Grade B60 (%)	Grade C65 (%)	Grade C70 (%)
CARBONIO (C)	0.26 max	0.24 max	0.23 max
manganese (MN)	0.98 max	1.20 max	1.35 max
fosforo (P)	0.035 max	0.035 max	0.035 max
zolfo (S)	0.035 max	0.035 max	0.035 max
Silicio (Si)	0.13-0.45	0.13-0.45	0.13-0.45
cromo (CR)	0.30 max	0.30 max	0.30 max
nichel (NI)	0.30 max	0.30 max	0.30 max
Molibdeno (Mo)	0.12 max	0.12 max	0.12 max
rame (Cu)	0.40 max	0.40 max	0.40 max
Vanadio (V)	0.08 max	0.08 max	0.08 max

Appunti:

Contenuto di carbonio is a key factor in determining the forza e Durezza of the steel. Lower carbon content improves saldabilità e duttilità.
manganese improves the Resistenza alla trazione e hardenability of the steel.
fosforo e zolfo are kept at low levels to prevent brittleness e improve toughness.
Silicio acts as a deoxidizer during the steelmaking process and improves forza.

Mechanical Properties Table {#mechanical-properties-table}

The mechanical properties of ASTM A672 steel pipes are determined by the Grado e Classe del tubo, as well as the trattamento termico applied after welding. The table below provides the typical mechanical properties for common grades of ASTM A672 pipes.

Property	Grade B60	Grade C65	Grade C70
Resistenza alla trazione (MPa)	415 min (60,000 psi)	450 min (65,000 psi)	485 min (70,000 psi)
Resistenza allo snervamento (MPa)	240 min (35,000 psi)	275 min (40,000 psi)	275 min (40,000 psi)
Allungamento (%)	22 min	22 min	22 min
Resistenza all'impatto (J)	Varies by class	Varies by class	Varies by class

Appunti:

Resistenza alla trazione is the maximum stress the material can withstand before breaking.
Resistenza allo snervamento is the stress at which the material begins to deform plastically.
Allungamento is a measure of the material’s ductility, indicating how much it can stretch before breaking.
Resistenza all'impatto is typically measured using Charpy V-notch tests, especially for applications in low-temperature environments.

Testing and Inspection Requirements {#testing-and-inspection-requirements}

To ensure the quality and performance of ASTM A672 EFW steel pipes, several testing and inspection methods are used during the manufacturing process. These tests help to identify any defects or inconsistencies in the material or weld that could compromise the pipe’s mechanical properties or structural integrity.

controlli non distruttivi (NDT) {#nondestructive-testing-ndt}

controlli non distruttivi (NDT) methods are used to inspect the weld seam and the pipe body for defects without damaging the material. I metodi NDT comuni includono:

Test ad ultrasuoni (OUT): Ultrasonic waves are used to detect internal defects such as cracks, vuoti, or incomplete fusion in the weld or pipe body.
Test radiografici (RT): X-rays or gamma rays are used to create an image of the weld, allowing inspectors to identify internal defects such as porosity, inclusioni di scorie, or cracks.
Test delle particelle magnetiche (MT): This method is used to detect surface defects in ferromagnetic materials. A magnetic field is applied to the pipe, and iron particles are used to reveal any cracks or discontinuities on the surface.
dye penetranti (P.T): A dye is applied to the surface of the pipe, and any cracks or defects will absorb the dye, making them visible under ultraviolet light.

Test idrostatico {#hydrostatic-testing}

Hydrostatic testing is a critical test used to ensure that the pipe can withstand the internal pressure it will be subjected to in service. During this test, the pipe is filled with water and pressurized to a level higher than its operating pressure. The pipe is then inspected for any leaks or deformations that may indicate a weakness in the material or weld.

Test Pressure: The test pressure is typically 1.5 times the design pressure of the pipe.
Duration: The pipe is held at the test pressure for a specified period (usually 5 per 15 minutes) to ensure it can maintain the pressure without failure.

Applications of ASTM A672 EFW Steel Pipe {#applications-of-astm-a672-efw-steel-pipe}

ASTM A672 EFW steel pipes are used in a wide range of industries and applications where high-pressure service and structural integrity are critical. Alcune applicazioni comuni includono:

produzione di energia: ASTM A672 pipes are used in boilers, scambiatori di calore, and steam pipelines in power plants due to their ability to withstand high pressures and moderate temperatures.
industria petrolchimica: These pipes are used in refineries, impianti chimici, and petrochemical facilities for transporting corrosive fluids and gases under high pressure.
Industria petrolifera e del gas: ASTM A672 pipes are used in oil and gas pipelines, Piattaforme offshore, and subsea pipelines to transport crude oil, gas naturale, and other hydrocarbons.
Water Transmission: These pipes are used in water transmission systems for transporting potable water, wastewater, and industrial water under high pressure.
Structural Applications: ASTM A672 pipes are used in structural applications such as columns, beams, and supports in buildings and industrial structures where strength and durability are required.

Domande frequenti (FAQ) {#FAQ}

1. What is the difference between EFW and ERW pipes?

EFW (Electric Fusion Welded) pipes are welded using an electric arc to fuse the steel plates together, while ERW (Resistenza elettrica saldato) pipes are welded using electrical resistance to heat the edges of the steel and fuse them together. EFW pipes are typically used for high-pressure applications, while ERW pipes are used for low to moderate pressure applications.

2. What are the common grades of ASTM A672 pipes?

Common grades of ASTM A672 pipes include Grade B60, Grade C65, and Grade C70, which are based on the chemical composition and mechanical properties of the steel.

3. What is the maximum operating temperature for ASTM A672 pipes?

ASTM A672 pipes are designed for use at moderate temperatures, typically up to 400°C (752° F), depending on the grade and class of the pipe.

4. How is the quality of ASTM A672 pipes ensured?

The quality of ASTM A672 pipes is ensured through nondestructive testing (NDT) metodi come i test ad ultrasuoni, Test radiografici, and magnetic particle testing, as well as hydrostatic testing to verify the pipe’s ability to withstand internal pressure.

5. What industries use ASTM A672 EFW steel pipes?

ASTM A672 EFW steel pipes are used in industries such as power generation, petrolchimico, olio e gas, and water transmission due to their ability to withstand high pressures and moderate temperatures.

Conclusione {#Conclusione}

ASTM A672 EFW steel pipes are designed for high-pressure service at moderate temperatures, making them ideal for use in industries such as power generation, petrolchimico, olio e gas, and water transmission. The electric fusion welding (EFW) process ensures a strong longitudinal weld that can withstand high internal pressures, while the use of pressure vessel quality steel ensures the pipes have the necessary mechanical properties for demanding applications.

The testing and inspection requirements outlined in ASTM A672, including nondestructive testing and hydrostatic testing, help to ensure the quality and performance of the pipes, making them a reliable choice for high-pressure and structural applications.

Taggato in: EFW Steel Pipe

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