ERW pipe manufacturing processes include HFW. ERW has low-frequency, medium-frequency, and high-frequency welding processes, and HFW is specifically for high-frequency resistance welding. The difference between ERW and HFW steel pipes is that EFW is an ERW process used for ordinary and thin-walled steel pipes.
What is ERW steel pipe?
ERW steel pipe is manufactured by low-frequency or high-frequency resistance. The weld is longitudinal. During the ERW pipe welding process, the current generates heat as it flows through the contact surface of the welding area. It heats the two edges of the steel to the point where the edges can form a bond. At the same time, under the combined pressure, the edges of the tube blank steel melt and squeeze together.
Usually the maximum outer diameter of ERW pipe is 24 inches (609 mm), and for larger size pipes, SAW will be used for manufacturing.
What is HFW steel pipe?
It should be noted that HFW pipe is a type of ERW pipe. HFW steel pipe is an ERW pipe produced with a welding current frequency equal to or greater than 70kHz. Through high-frequency current welding resistance, heat is generated on the contact object, so that the surface of the object is heated to a plastic state, and then the steel combination is achieved through forging or non-forging.
High-frequency electromagnetic waves are a kind of solid resistance heat energy. When high-frequency current passes through a metal conductor, two peculiar effects will be produced, namely the skin effect and the proximity effect.
The HFW process uses the skin effect to concentrate the metal on the surface of the steel object, and the proximity effect to control the position and the power flow path of the high-frequency current. Due to the very high speed, the edge of the contacting steel plate can be heated and melted in a very short time, and then extruded through the butt process.
Differences between ERW and HFW
The main difference between ERW and HFW is the way they use current and the types of products they are suitable for. ERW uses low-frequency current, while HFW uses high-frequency current, which results in different welding penetration, tolerances and heat-affected zones. ERW is best suited for thin-walled pipes ranging from 0.25 to 24 inches in diameter, while HFW is more suitable for thick-walled pipes ranging from 8 to 20 inches in diameter.
Advantages and Disadvantages
ERW is known for its cost-effectiveness, smooth production surface, and fast production speed. However, it also has some disadvantages, such as weak welds, higher risk of defects, and limited pipeline thickness. On the other hand, HFW produces pipes with high strength and close tolerances, and can be produced in large quantities. However, HFW has a complex process, high cost, and long production time.
ERW steel pipe includes HFW steel pipe
ERW is a general term for electric resistance welded steel pipes, which are divided into alternating current welding (AC) and direct current welding (DC). AC welding is further divided into low frequency welding, medium frequency welding, ultra-high frequency welding, and high frequency welding according to frequency. High frequency welding (HFW) is mainly used for ordinary or thin-walled steel pipes, including contact welding and induction welding, and DC welding is generally used for small-diameter steel pipes. Generally speaking, HFW is one of the ERW production methods, using high-frequency welding technology, so ERW steel pipe also includes HFW steel pipe.
What types of pipes (standards) can be produced by the ERW process?
The answer is that there are many pipes (standards) that can be manufactured by the ERW process. Below we list the most common standards in pipes.
Stainless steel ERW pipe standards and specifications
ASTM A269 stainless steel pipe
ASTM A312 stainless steel pipe
ASTM A270 sanitary pipe
ASTM A790 ferritic/austenitic/duplex stainless steel pipe
ASTM A53 Grade B and Grade A (and galvanized)
ASTM A252 pile pipe
ASTM A500 structural pipe
EN 10219 S275, S355 pipe
ASTM A134 and ASTM A135 pipe
API ERW line pipe
API 5L B to X70 PSL1 (PSL2 should use HFW process)
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