1. What is a welded pipe?
Welded steel pipe is referred to as welded pipe. It is a steel pipe made by welding steel plates or steel strips after curling and forming. The production process of welded pipe is simple, the production efficiency is high, the varieties and specifications are many, the equipment investment is small, and the general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip steel continuous rolling production and the advancement of welding and inspection technology, the quality of welds has been continuously improved, the varieties and specifications of welded steel pipes have increased day by day, and they have replaced seamless steel pipes in more and more fields. Welded steel pipes are divided into spiral welded pipes and straight welded pipes according to the form of welds.
2. What is a spiral welded pipe?
Low-carbon structural steel or low-alloy structural steel strip is rolled into a tube blank at a certain spiral angle (called forming angle), and then the tube seam is welded together. It can produce large-diameter steel pipes with narrower strip steel. Spiral welded pipes are mainly used for natural gas and oil pipelines, and their specifications are expressed by outer diameter × wall thickness. Spiral welded pipes are single-sided welded and double-sided welded. The welded pipes should ensure that the water pressure test, tensile strength of the weld and cold bending performance meet the requirements.
3. What is a straight seam welded steel pipe?
It is named because the welding part of the steel pipe is in a straight line; the method is to use steel strips to produce pipes that are straight-seamed in high-frequency welding equipment. According to different uses, there are different post-production processes. It can be roughly divided into scaffolding pipes, fluid pipes, wire casings, bracket pipes, guardrail pipes, etc. Low-pressure fluid welded pipes are a type of straight seam welded pipes, generally used for water and gas transportation. After welding, they are subjected to one more water pressure test than ordinary welded pipes. Therefore, the price of low-pressure fluid pipes is generally a little higher than that of ordinary straight seam welded pipes (according to the current market price, it is about 80 yuan higher). For example: the price of a 1-inch welded steel pipe fluid pipe (DN25) (that is, Φ33.5*3.25) is about 3900 per ton. The price of ordinary straight seam welded pipes is about 3800. The price changes every day. Please refer to the price of the day.
4. What are the types of welded pipes according to their functions?
A. (GB/T3092-1993) Welded steel pipes for fluid transportation are also called general welded pipes, commonly known as black pipes. Made of Q195A, Q215A, and Q235A steel. They are welded steel pipes used for conveying generally low-pressure fluids such as water, air, gas, oil, and heating steam, and for other purposes. The wall thickness of the steel pipe joint is divided into ordinary steel pipes and thickened steel pipes; the pipe end form is divided into non-threaded steel pipes (plain pipes) and threaded steel pipes. The specifications of the steel pipe are expressed in nominal diameter (mm), which is an approximate value of the inner diameter. It is usually expressed in inches, such as 11/2, etc. In addition to being used directly to convey fluids, welded steel pipes for low-pressure fluid transportation are also widely used as the original pipes of galvanized welded steel pipes for low-pressure fluid transportation.
B. Galvanized welded steel pipe for low-pressure fluid transportation (GB/T3091-1993) is also called galvanized electric welded steel pipe, commonly known as white pipe. It is a hot-dip galvanized welded (furnace welded or electric welded) steel pipe used for conveying water, gas, air oil, heating steam, warm water and other generally low-pressure fluids or other purposes. The wall thickness of the steel pipe joint is divided into ordinary galvanized steel pipe and thickened galvanized steel pipe; the pipe end form is divided into non-threaded galvanized steel pipe and threaded galvanized steel pipe. The specifications of the steel pipe are expressed in nominal diameter (mm), and the nominal diameter is the approximate value of the inner diameter. It is usually expressed in inches, such as 11/2, etc.
C. Straight seam electric welded steel pipe (YB242-63) is a steel pipe with the weld parallel to the longitudinal direction of the steel pipe. It is usually divided into metric electric welded thin-walled pipe, electric welded steel pipe, transformer cooling oil pipe, etc.
D. Ordinary carbon steel wire casing (GB3640-88) is a steel pipe used to protect wires in electrical installation projects such as civil construction and industry, installation machinery and equipment.
E. General low-pressure fluid transportation spiral seam submerged arc welded steel pipe (SY5037-83) is made of hot-rolled steel strip coil as pipe blank, spirally formed at room temperature, and made by double-sided automatic submerged arc welding or single-sided welding. It is used for gas, water, air and steam and other general low-pressure fluid transportation submerged arc welded steel pipe.
F. Spiral seam submerged arc welded steel pipe for pressure fluid transportation (SY5036-83) is made of hot-rolled steel strip coil as pipe blank, spirally formed at room temperature, welded by double-sided submerged arc welding, and used for pressure fluid transportation. The steel pipe has strong pressure bearing capacity and good welding performance. It has undergone various rigorous scientific inspections and tests and is safe and reliable to use. The steel pipe has a large diameter, high transportation efficiency, and can save investment in laying pipelines. It is mainly used for pipelines for transporting oil and natural gas.
G. Spiral seam high-frequency welded steel pipe for pressure fluid transportation (SY5038-83) is made of hot-rolled steel strip coil as pipe blank, spirally formed at room temperature, and welded by high-frequency lap welding. It is used for spiral seam high-frequency welded steel pipe for pressure fluid transportation. The steel pipe has strong pressure bearing capacity, good plasticity, and is easy to weld and process. After various strict and scientific inspections and tests, it is safe and reliable to use. The steel pipe has a large diameter and high transportation efficiency, and can save investment in laying pipelines. It is mainly used for laying pipelines for transporting oil, natural gas, etc.
H. Spiral welded steel pipe for piles (SY5040-83) is made of hot-rolled steel strip coil as pipe blank, spirally formed at room temperature, and made by high-frequency welding or double-sided submerged arc welding. It is used for foundation piles of civil engineering structures, bridges, docks, etc.
I. Spiral seam high-frequency welded steel pipe for general low-pressure fluid transportation (SY5039-83) is made of hot-rolled steel strip coil as the tube blank, spirally formed at room temperature, and welded by high-frequency lap welding. It is used for spiral seam high-frequency welded steel pipe for general low-pressure fluid transportation.
5. What is the calculation formula for various pipes?
Straight seam welded pipe: (outer diameter-wall thickness) × 0.02466 × wall thickness × length (6 meters) × ton price = branch price
Galvanized pipe: (outer diameter-wall thickness) × 0.02466 × wall thickness × 1.06 × length (6 meters) × ton price = branch price
Spiral welded pipe: (outer diameter-wall thickness) × 0.0246615 × wall thickness × length (6 meters) × ton price = branch price
