What are key points of manufacturing thin-walled seamless steel tube for gas cylinder

What are key points of manufacturing thin-walled seamless steel tube for gas cylinder ?

What are key points of manufacturing thin-walled seamless steel tube for gas cylinder ?

 

Base Material

The seamless steel tube used for gas cylinder is mainly thin-walled tube. The gas cylinder, using the seamless steel tube as the base material, is widely used for gas storage, industrial energy storage device, in fire fighting, hospital, oilfield and other fields. The gas cylinder is a pressure vessel, which has strict requirements on the quality and geometric size of the internal and external surface of the base material. Visible cracks, scars, folds, pinholes, slag, inclusions, and cracks, etc. on seamless steel tube are unacceptable. The base material must  have stable geometry and chemical composition, good solidification structure, on which there must be no defects such as white spot, shrinkage cavity, stratification, crack, bubble, inclusion, flip, subcutaneous bubble, etc.

 

Steel Grade

Because of the difficulty of deformation and the high quality requirement on inner and outer surface in the process of hot rolling, it must use the highest steel grade and the most difficult technique. Among them, 35CrMo, 37Mn, and 34CrMo4 steel tube are low carbon, low alloy austenitic steel with excellent comprehensive mechanical properties and higher rolling process requirements.

 

Development

The traditional production process of gas cylinders is mainly made of billet. Billet first is heated and then punched and drawn to make gas cylinder. However, the yield of gas cylinders using this method is low, in order to solve this problem, people recently developed the technology of thin-walled seamless tube in manufacturing high-pressure gas cylinder tube, with the help of the key technology of bottom closing of gas cylinder made of seamless tube. It is convenient for the application of the key technology, which makes the manufacture of gas cylinder tube change from using steel billet through punching and drawing to using thin-walled seamless steel tube, and it has become the development trend.

 

Advantages

Steel tube for High-pressure gas cylinder has many applications in our life. As a kind of innovation, it breaks the shackle of traditional manufacturing of gas cylinder and has its own unique advantages.

The internal and external surface quality of seamless steel tube for high-pressure gas cylinder is very good, and its whole wall thickness is quite uniform. Because of its light weight, high productivity, material rate and low cost, it is welcomed by the majority of users.

 

Process Characteristics

In order to improve the overall transport capacity of seamless steel tube for high-pressure gas cylinder, people put forward strict requirements on the steel tube rolling process. If you want to improve the quality of high-pressure gas cylinder, the key is to reduce the ratio of volume to weight. Therefore, we need to improve the ratio of diameter to wall thickness as much as possible on the premise of ensuring the excellent quality of the steel tube used to manufacture gas cylinders.

At the same time, the ratio of diameter to wall thickness is required to reach about 40. However, as far as the rolling technology of high-pressure gas cylinders is concerned, it is very difficult to improve the ratio of diameter to wall thickness, and wall thickness process technology. This is mainly because the wall is thin, the deformation of continuous rolling mill unit is large, the overall coefficient of elongation between 4.0 and 5.0. In addition, it is difficult for us to control the accuracy of wall thickness, because under normal circumstances, temperature fluctuation, adjustment, rack spring and other factors of steel tube will affect its wall thickness.

 

Major Manufacturer

Seamless steel tube manufactured by Baotou Steel ( a state-owned company of steel products ) in Inner Mongolia provide high quality base material for the manufacturing of tube-made gas cylinder. It has the advantages of good internal and external surface quality, uniform wall thickness, light weight, high productivity and finished product rate, low cost and so on, regarded  as one of  the hero products in China. As a leading manufacturer of steel products, Baotou Steel have exported seamless steel pipe, coating pipe, casing and tubing pipe, steel rails and so on throughout the world. API, ISO, TUV, ABS, CCS, etc certificated qualification and extreme standard keep Baotou Steel very competitive in current market.

 

 

What is Russian standard GOST R 51685 P65 steel rail

What is Russian standard GOST R 51685 P65 steel rail?

Introduction of P65/R65 steel rails

GOST R 51685 is the state standard of the Russian Federation for railway steel rails.This standard is effective for railway rails,used for joined and continuous welded rail tracks of railways and for production of point switches.There are four type of train rails with the steel grades of M76T,K76T,M76,K76 produced according to this standard,they are P50/R50,P65/R65,P65K,P75.Among them,P65 is widely used in railroad construction projects.Baotou Steel is an experienced train rail manufacturer who can produce P65 steel rails in large quantity.

What is Russian standard GOST R 51685 P65 steel rail

P65 steel rail section diagram

Advantages of Baotou Steel on – line heat treatment train rail

At present, Baotou Steel has two world advanced 100-meter universal rolling production lines, with a total design capacity of 2.1 million tons a year. It is one of the main manufacturers of steel rails in China.The steel rails produced by Baotou Steel have been exported to many countries such as Canada, the United States, Mexico, Brazil, Argentina, Uruguay, Bolivia, South Korea, Indonesia, Malaysia, Thailand, the Philippines, Bangladesh, Saudi Arabia, Pakistan, Iran, Kenya, Australia, Spain, Angola, Mongolia, Laos, north Korea, Vietnam and other countries.

China’s domestic online heat treatment rail manufacturers mainly adopt the online water mist cooling process and the online pure air cooling process.The stability of water mist cooling process is poor, the adjustment of process is difficult, the structure stability of rail is difficult to control, the performance index is low, which affects the comprehensive service life of rail.In view of the limitations of the on-line water mist cooling process, Baotou Steel has optimized and upgraded the 100-meter rail waste heat quenching production line, and realized the on-line pure air cooling process of rail through length. This process has high recognition in the industry and good process stability, which can effectively guarantee the safety of rail organization and greatly improve the internal performance index of rail.

Comparison of GOST R 51685 76T steel rail and TB/T 2344 U75V steel rail

With optimization and upgrading, the TB/T 2344 standard H340 U75V online heat treatment rail structure and performance indexes produced by Baotou Steel have reached the industry’s advanced level, as follows:

Main performance index of U75V online heat treatment rail
TB/T 2344
U75V
Tensile properties Surface hardness  HBW The section hardness HRC
Tensile strength Mpa Elongation % Test number Average number Volatility number First Last
Standard requirement ≥1180 ≥10 340-400 / ≥30 36-42 ≥34
Our actual production 1250-1300 11-14 355-380 ≥355 0-8 37-42 35-40

 

Chemical Composition of TB/T 2344 U75V and GOST R 51685 76T
Standard Grade C Si Mn P S Cr V AL Ti
TB2344 U75V H340 0.71-0.8 0.5-0.8 0.75-1.05 ≤0.03 ≤0.025 0.04-0.12 ≤0.01 0.007- 0.025
51685 76T 0.71-0.82 0.25-0.60 0.75-1.15 ≤0.025 ≤0.025 ≤0.02 ≤0.025

 

Range of dimensional deviation
Types Gost R 51685 P65 rail Chinese standard 60kg/m-75kg/m rails
Head width b ±0.5 ±0.5
Foot width B +1.0,-0.5 +1.0,-0.5
Web thickness e +0.8,-0.5 +1.0,-0.5
Rail height H ±0.8 ±0.6
Point height m +1.0,-0.5 +0.75,-0.5
Web height h +0.3,-0.7 +0.6,-0.5

Compared with the water mist process, the tensile strength of the rail increased by about 50MPa, the hardness of the tread increased by about 10HBW, the hardness fluctuation value of the tread decreased by about 10HBW, and the hardness of the cross section increased by 1-2HRC as a whole.So Baotou Steel can produce TB/T 2344 steel rails equals to GOST R 51685 P65 steel rails and the rails have better performance than the standard specified.

Other kinds of hot sale steel rails

The 50 kg/m, 60 kg/m (60, 60 N), 75 kg/m (75, 75 N), 60AT1, 60AT2 steel rails produced according to TB/T 2344 standard with the steel grades of U71Mn and U75V mainly supply domestic railway line section and have been exported to Vietnam,Kenya and other countries.Baotou Steel also produce the European standard EN 13674-1 54E1, 60E1 and 60E2 steel rails as well as UIC860 standard UIC54 and UIC 60 steel rails with the steel grade of 900A.