Cooling rate of X80 pipeline steel welding heat affected zone

For long-distance natural gas pipeline, using high grade pipeline steel is the main way to save costs.

Canada's pipeline industry practice proved that: compared with the X60, adoption of X70 pipeline wall thickness can be reduced 14%;Compared with X70, adoption of X80 pipeline wall thickness can be further reduced by 12.5%. Welding is one of the key links in steel pipe manufacturing and pipeline construction, due to uneven welding thermal cycle, the welding heat affected zone (HAZ) is a weak part of the pipeline. Cooling rate is the main parameter to determine HAZ organization performance, it is related to the welding heat input, the thickness of workpiece and the surrounding radiation condition. Therefore, making the reasonable welding process, control welding cooling speed can get excellent organization performance of the HAZ, avoid HAZ cracks, so as to ensure the safety operation of pipeline.

With the increase of cooling rate, the microstructure of X80 pipeline steel HAZ is given priority to with polygonal ferrite, to give priority to with B or grain of lath martensite, the hardness will increase. When the welding heat input is too big or preheating temperature is too high and the cooling speed is lower than 2 ℃ / s, X80 pipeline steel HAZ organization is given priority to with or B polygon ferrite grains, but due to the existence of pearlite and MA island group block distribution, leading to the coarse crystal impact performance poorer.

When the welding heat input is too small or preheating temperature is too low and the cooling speed is greater than 30 ℃ / s, X80 pipeline steel HAZ organization is given priority to with BF or lamellar martensite, resulting in the decrease of the coarse crystal impact performance. Making reasonable welding process, controlling the cooling rate within the scope of 2 ~ 30 ℃ / s, X80 pipeline steel HAZ organization is given priority to B, MA island group is scattered, the coarse grain zone has proper hardness and excellent impact performance.

Tech & Service of Seamless pipe

Seamless pipes are extensively applied for the nuclear device, gas, petrochemical, ship building and boiler industries. Seamless pipes dominates 65% of market share in Chinese boiler industry.

How to make seamless pipe(seamless pipe process)?
Hot Piercing Workshop
Piercing process
The cross roll piercing and pilger rolling process in the size range from approx. 250 to 660 mm outside diameter.
Precision cold drawn steel tube production process
Pipe weld cracks
often follow different mechanisms can be divided into two types of thermal cracking and cold cracking.
How to calculate a steel pipe and tube theoretic weight
Calculate a steel pipe?
Pipe fittings are necessary to join together pipes, or to change the direction of an existing pipe.
Pipe beveling
Pipe beveling is the process where an angle is formed between the edge of the end of a pipe or tube and a plane perpendicular to the surface.
Steel pipe cutting machine
Pipe cutting
Cutting tools have a grinding wheel piece cutting machine (also known as toothless saw), hand saw, cutter and other hand tools.
Packing the steel pipes
There are probably hundreds of different methods for packing a pipe, and most of them have merit, but there are two principles that are vital for any method.


Our team are highly trained and experienced in servicing and producing all types of steel supplies. Whether you've got a large construction project, or need parts for industrial machinery, our team of steel fabrication consultants will ensure that your project is provided with the parts you need, when you need them.

Link exchange

Copyright © 2011 Sunny Steel Enterprise Ltd.  All Rights Reserved ICP No.:08010763