Monday, December 29, 2014

16Mn seamless pressure pipes and GB8162 standard

Why 16Mn seamless pressure pipes should not be in accordance with GB8162 standard?
The 16Mn seamless steel pipe standard includes GB8162, GB8163, GB6479 and GB9948. For example, 16Mn9948 one kind of 16Mn seamless steel pipe.
GB8162 and GB8163 seamless steel pipe differences:
GB8162 "structural seamless steel pipe", this standard applies to the general structure of the mechanical structure; GB8163 "transmission fluid with seamless steel pipe" This standard applies to transport fluids generally seamless steel pipe, the main difference is that the GB8163 steel should be carried out hydraulic test or ultrasonic, eddy current and magnetic flux leakage inspection one by one, so for the standard selection of pressure line pipe, GB8162 standard should not be used.
16mn seamless and 16MnR, 19Mng are merged into Q345R. Q345R is ordinary low-alloy steel, and common used boiler and pressure vessel, delivery status: hot rolled or normalizing, is a low-alloy steel, containing low Mn content. Performance is similar with 20G (412-540), and the tensile strength (450-655) slightly stronger, elongation of 19-21%, poorer than 20G of greater than 24 percent. Q345R process is in reference to standard GB713-2008.

Sunday, December 28, 2014

How to distinguish the 16Mn seamless steel pipe from 45 # steel.

How to distinguish the 16Mn seamless steel pipe from 45 # steel.
45 # steel is widely used in machinery manufacturing with good mechanical properties of this steel. But this is a medium carbon steel, hardened performance is not good, 45 steel can be hardened to HRC42 ~ 46. So if you need a surface hardness, and also hope to play 45 # steel superior mechanical properties, it often does carburizing on the surface of 45 # steel, so you can get the required surface hardness.
16Mn seamless steel pipe is a pressure vessel dedicated board with a yield strength of 340MPa grade, and it has a good mechanical properties and process performance. Phosphorus, sulfur content is slightly lower than the S & P 16Mn steel, in addition to the tensile strength and elongation requirements are higher than ordinary steel, the 16Mn also sought assurances toughness. It is currently China's most widely used and the largest amount ofpressure window special steel. Special steel 16Mn seamless steel pipe for the bridge as "16Mnq", a special steel for automobile frames "16MnL", a special steel pressure vessel is "16MnR".
Such steel is to rely on the adjustment of carbonaceous (C) amount to improve the mechanical properties of the steel, and therefore, according to the level of the carbon content, such steels can be divided into:
Mild steel - carbon content is generally less than 0.25% , such as10# steel and 20# steel;
Medium carbon steel - carbon content is generally between 0.25 to 0.60%, such as 35# steel and 45# steel;
High carbon steel - carbon content is generally greater than 0.60%. Such steel is generally not used in the manufacture of steel pipe.

What is a non-metallic inclusions in seamless steel pipe

What is a non-metallic inclusions in seamless steel pipe and where is it come from?
Non-metallic compounds present in the steel, such as an oxide, sulfide, nitride or complex compounds, collectively referred to as non-metallic inclusions.
Non-metallic inclusions in steel comes from two aspects: one is produced with the smelting process, the other is brought in due to various reasons from the outside. The former we call it endogenous inclusion, and the latter is called foreign inclusion.
(1) endogenous inclusions. Can be produced in the following situations:
① in the smelting process, the product of deoxygenation is not fully ruled out, while remaining in the liquid steel. Some of them are small particles present in the basic structure of the steel, the others are gathered into large particles, and some take solid solution state in the steel;
② deoxygenation reactions are mostly exothermic reaction, the temperature drops in the casting process, then deoxygenation reaction continues to proceed, deoxidation products generated too late to float and remain in the steel;
③ In the tapping and casting process, molten steel is oxidized in contact with air, oxygen in combination with steel elements, to form a secondary oxide remaining in the steel;
④ during solidification of the ingot, as a result of "selected sub-crystalline" of the liquid steel, the low melting point of FeS, FeO precipitated between the grain boundaries and the dendrite ingot, becoming non-metallic inclusions.

(2) foreign inclusions can be produced in the following situations:
① soil, rust brought by scrap materials and impurities brought by refractories;
② in a steel casting process, molten steel tank washed out, ladle, tundish, the refractory material washed down to the molten steel to go, if too late float, then left in the molten steel;
③ When the punch mixed with slag, the steel slag to be wrapped into liquid forming mixed;
④ ladle as residue or a steel cover agent when falling ash and steel ladle and tundish stream sediment, tundish and mold will be mixed with the liquid steel to form inclusions;
In general, the endogenous particles are relatively small, and are relatively uniform distributed in the seamless steel pipe, but foreign inclusions are mostly irregular in shape, size and relatively large, the distribution is not uniform, sometimes appear here, sometimes there appear.

Thursday, December 25, 2014

Analysis of seamless steel pipe industry development

Analysis of seamless steel pipe industry development
Through the rapid development of Chinese seamless steel pipe industry, "Eleventh Five-Year" period, now has nearly 400 sets of various types of units, production capacity more than 30 million tons, accounting for about half of the world production of seamless steel tubes, become a veritable seamless steel pipe production and consumption country. During the "Eleventh Five-Year", China seamless steel pipe production from 15.08 million tons in 2006 to 25.28 million tons in 2010, the annual increase of 10.2 million tons. Apparent consumption of 13.27 million tons from 2006 to 2010 of 21.72 million tons, an increase of 8.46 million tons. 2011 Chinese seamless steel pipe production 26.488 million tons, an increase of 3.88%; apparent consumption 2512.80, an increase of 16.75%. 2012, cumulative production of 28.199 million tons of domestic seamless pipe, an increase of 6.46%; after the impact of the financial crisis in 2009, China's seamless steel pipe is blocked, in 2012 China's seamless steel pipe exports reached 500 million tonnes again.

Internationally renowned seamless steel pipe industry enterprises
Argentina Tenaris Group (TENARIS)
Vallourec & Mannesmann Pipe Company (Vallourec & Mannesmann)
Japan's JFE Steel Corporation
Sumitomo Metal Industries (Sumitomo)

Chinese seamless steel pipe industry leaders
Hengyang Valin Steel Tube Co., Ltd.
Jiangsu Chengde Steel Tube Co., Ltd.
Anhui Tianda Oil Pipe Steel Pipe Group Co., Ltd.
Yantai Lubao Steel Pipe Co., Ltd.
Hunan great steel pipe co.,ltd
WSP OCTG Steel Pipe Manufacturing Co., Ltd.
Tonghua Iron and Steel Group Co., Ltd.

Wednesday, December 24, 2014

Basic situation of container size

Basic situation of container size overview for welded steel pipe:
20-foot container: internal dimensions 5.69 m X 2.13 m X 2.18 m / picking gross weight is generally 17.5 tons / volume 24-26 cubic
40-foot container: internal dimensions 11.8 m X 2.13 m X 2.18 m / picking gross weight is generally 22 tons / volume 54 cubic
40 high cabinet: internal dimensions 11.8 m X 2.13 m X 2.72 m / picking gross weight is generally 22 tons / volume 68 cubic
20-foot refrigerated: internal dimensions 5.42 m X 2.26 m X 2.24 m / picking gross weight is generally 17 tons / volume 26 cubic
40-foot refrigerated: internal dimensions 11.20 m X 2.24 m X 2.18 m / picking gross weight is generally 22 tons / volume 54 cubic
40 high refrigerated: internal dimensions 11.62 m X 2.29 m X 2.50 m / picking gross weight is generally 22 tons / volume 67 cubic
45-foot refrigerated: internal dimensions 13.10 m X 2.29 m X 2.50 m / picking gross weight is generally 29 tons / volume 75 cubic
20-foot open top container: internal dimensions 5.89 m X 2.32 m X 2.31 m / picking gross weight 20 tons / volume 31.5 cubic
40-foot open top container: internal dimensions 12.01 m X 2.33 m X 2.15 m / picking gross weight 30.4 tons / volume 65 cubic
20-foot flat-bottomed container: internal dimensions 5.85 m X 2.23 m X 2.15 m / picking gross weight 23 tons / volume 28 cubic meters
40-foot flat-bottomed container: the size of 12.05 meters within meters X 1.96 X 2.12 m / picking  gross weight 36 tons / volume 50 cubic meters
45-foot container: the size of 13.58 meters within meters X 2.71 X 2.34 m / picking gross weight is generally 29 tons / volume 86 cubic.

Tuesday, December 23, 2014

Overcapacity of ERW steel pipe in China

For the 21st century, China's natural gas industry will enter a development period of "natural gas" as a symbol, natural gas source diversification, and city gas transition to natural gas. China has abundant natural resources, coupled with the increasing proved reserves and imported natural gas, making the construction of gas transmission lines and downstream branch pipe network become a reality, in fact, our pipeline industry in the second construction boom has arrived.
Currently, cities across the country are all promoting and transforming the urban gas pipeline network project, which account for about 45% of the total investment in this project is the pipeline - steel pipe, and according to more than 50 cities gas pipe network design applications, almost all are the high-frequency straight seam resistance welded steel pipe (Electric Resistance Welding,  ERW steel pipe for short). However, due to the experience issue, there is a big difference of the mastering content of ERW steel pipe specifications, resulting in ERW steel pipe manufacturer for each project must face different process parameters, increasing the difficulty of the work, and some even produce overcapacity problem.

Monday, December 22, 2014

What matters when high speed welding the steel pipe

In terms of the welded steel pipe at processing, the main problem needed to be solved is: the welder should deliver enough energy to the V-weld pipe area. This transfer of energy is achieved by the magnetic field produced during operation of the welder, and conducted through the impedance. Its magnetic field vector is increased with the increasing of the required welding power (rolling speed×wall thickness). And the magnetic flux of the impedance is affected by the strength of the saturation magnetic flux of ferrite, the total cross-sectional area and temperature. With the V-shaped area of welding flux (V-type area of×V-shaped opening) of decreases. Based on the above theory, this welded steel pipe at high speed, executing the following specifications is necessary:
1.Use a large diameter resistor as much as possible. End solid shape is superior to hollow circle.
2. Provide sufficient cooling water - at least 4 gallons per minute (US), best reaching 5 gallons per minute. Because water line near the impedance is small and easy for blockage, it must ensure that the cooling water is very clean. In addition, the housing of the impedance can senseg heat, which will result in the accumulation of the metal particles and the destruction of the housing and ferrite.
3. Place the resistor correctly (from the apex 1/8 " of the V-shaped area). If choose from the available small impedance and meeting the specification requirements, the requirements of the specification should be preferred.
4. Place the roll as close to the welding squeeze roll as possible, from its approximately 1/4 to 1/2, and guarantee that its center perpendicular to the rolling axis .
5. When molding the hfw steel pipe, shaped with large diameter as much as possible; then reducing in the sizing section. Optimum pipe diameter is preferably formed of 0.695. "
6.Correct positioning of material holder can obtain the minimum length of a V-shaped mouth, and can make the weld squeeze rollers heated to a minimum. The size of the V-shaped mouth should be 2 times the diameter or slightly less. Between two rollers at the top, and it will give the minimum length of the V-shaped mouth.

Sunday, December 21, 2014

304N stainless steel seamless steel pipe

304N stainless steel
Name: Austenitic stainless steel
Standard: AISI, ASTM
Model: 304N
UNS Number: S30451
A, 304N Characteristics and Application:
304N is a nitrogen-containing stainless steel, is a stainless steel seamless steel pipe, standard: GB 0Cr19Ni19N, adding nitrogen is to increase the strength of steel, with a high content of nickel, and the hardening rate is low, 304N stainless steel is suitable for those with low requirements of cold forming.

B, 304N chemical composition①:
C: ≤0.08
Mn: ≤2.00
Si: ≤0.75
Cr: 18.0 ~ 20.0
Ni②: 8.0 ~ 10.5
P: ≤0.045
S: ≤0.03
N: 0.10 ~ 0.16
Note: ①single value except stated, all are the highest value; ②for some pipe technology, and the nickel content of some types of austenitic stainless steel must be slightly higher than the values shown in the table.
C, mechanical properties:
Tensile strength σb (MPa): ≥550
Conditions yield strength σ0.2 (MPa): ≥275
Elongation δ5 (%): ≥35
Section shrinkage ψ (%): ≥50
Hardness: ≤ 217HB; ≤95HRB; ≤220HV
1: heat treatment and microstructure specifications:
Heat Specifications: 1010 ~ 1150 ℃ rapid cooling.
Microstructure: Organizing for the austenitic type.
2: Delivery status:
Generally heat treatment delivery, the treatment types specified in the contract; not indicated, by not heat treatment delivery.

Thursday, December 18, 2014

Cold straightening of seamless steel pipe

Let the processed seamless steel pipe products have a smaller tortuosity relied on the mechanical straightening machine to complete. So in order to eliminate the seamless steel pipe turns, all seamless steel pipe must undergo cold straightening.
Seamless steel pipe tortuous is caused by the improper adjustment, residual stress of rolling and inequality of the cooling section and length along the tube. Thus, you can not get straight pipe directly from the mill, only through straightening, the steel pipe tortuosity can meet the conditions of the rule.
The fundamental principle of straightening is to make the seamless steel pipe elastoplastic tortuous, changing from large tortuosity to small tortuosity, and therefore within the steel straightening machine will definitely suffer repeated setbacks. The repeat tortuous degree of the steel pipe is mainly determined by adjusting the straightening machines.
There are many factors affecting the straightening quality, such as the tortuosity of original tube, pipe dimensions and material type alignment models, adjusting parameters and so on.

Straight seam steel pipe and spiral steel pipe

Process quality overall performance of straight seam steel pipe is better than spiral steel pipe. At present, the domestic production of straight seam steel pipe are: nominal diameter DN400 and below the high-frequency ERW steel pipe, nominal diameter DN400 above for LSAW steel pipe. For LSAW steel pipe, according to different molding process, a total five different ways of UOE, JCOE, HME, RBE and PFP, the former two are the most common. Because UOE forming welded steel pipe production line is with high molding equipment technology content, high production efficiency, molding process is relatively simple, good shape, and a small welding stress after forming ; and because of the overall expansion of production used in hydraulic diameter steel pipe can effectively eliminate stress, improve the pipe strength and dimensional accuracy, so the quality is better than JCOE forming welded steel pipe.

45 # seamless steel pipe

45 # seamless steel pipe
45 # seamless steel pipe is one of the steel materials. A high-quality carbon structural steel.
A lot of mold production company will use it as the mold steel.
45 # seamless steel pipe refers to the carbon content of such material, probably about 450. Such material, compared to the other high quality carbon steel, are more common.
45 Steel: the average carbon content of 0.42-0.50%, the average silicon content of 0.17-0.37%, the average manganese content of 0.50-0.80%, the average sulfur content of <= 0.035%, the average phosphorus content <= 0.035% , the average chromium content <= 0.25%, with an average nickel content of <= 0.2545 steel. About 0.45% carbon content.
Recommended heat treatment temperature
45 # seamless steel normalizing: 850
45 # seamless steel pipe quenching: 840
45 # seamless steel tempering: 600
45 # seamless steel tensile strength: not less than 600Mpa
45 # seamless steel pipe yield strength: not less than 355Mpa
45 # seamless steel pipe elongation: 10%
45 # seamless steel pipe shrinkage: 40%
45 # seamless steel pipe Impact Energy: 39J
45 # seamless steel pipe steel delivery status hardness: no more than
45 # seamless steel pipe is not heat-treated: 229HBS
45 # seamless steel annealed steel: 197HBS
45 # seamless steel pipe Application examples:
For parts of the impeller pump compresso,r manufacturing gears, rack, sprockets, shaft, keys, pins, steam turbine.
Model 45 #
45 # seamless steel pipe products specifications φ: 756MM; wall thickness: below 100MM.

Wednesday, December 17, 2014

Main materials of line pipe

The line pipe includes seamless steel pipe and welded steel pipe two type, the pipe ends have flat end, threaded end and socket end; coupled essentials for welding ends, coupling connection, socket connection and so on.

Materials mainly are: 10 #, 20 #, 35 #, 45 #, 16Mn (Q345), 27SiMn, 40Cr, 15CrMoG, 35CrMo, 12Cr1MoVG, 10CrMo910, T91 (Steel Institute 102), A335P11, A335P12, A335P22, A335P91, A213T11, A213T12, SA106B, SA106C, A333GR.1, A333GR.6, ST45.8-III, J55, K55, N80, L80, P110, X40-70, L245, L360, DZ40, DZ50, R80, YB235-70,12Cr2MoWVTiB etc. .

APISPEC5L-2000 line pipe steel is a pipeline specification prepared and published by the American Petroleum Institute, common used throughout the world. This kind of critical steel material: B, X42, X56, X65, X70 and other steel grade.

Oil casing importing

Oil casing import
(1)oil casing main importing countries are: Germany, Japan, Romania, the Czech Republic, Italy, Britain, Austria, Switzerland, the United States, Argentina, Singapore also. Standard reference import more American Petroleum Institute Standard API5A, 5AX, 5AC. Steel grade is H-40, J-55, N-80, P-110, C-75, C-95 and the like. The main specifications for 139.77.72R-2,177.89.19R-2,244.58.94R-2,244.510.03R-2,244.511.05R-2 and so on.
(2)API predetermined length in three ways: i.e., R-1 is 4.88 ~ 7.62m, R-2 is 7.62 ~ 10.36m, R-3 is 10.36m to longer.   
(3)some of the imported goods marked with LTC words, that is the filaments buckle sleeve.
(4)The casing pipe imported from Japan in addition to using API standards, there are a small part implementation of the Japanese factory standards (such as Nippon Steel, Sumitomo, Kawasaki, etc.), steel grades are the NC-55E, NC-80E, NC-L80, NC-80HE and so on.
(5) In the case of claims, there have been black buckle, threaded injury, tube folding buckle down and threaded standoff ultra-poor, ultra poor coupling J value the appearance of defects and brittle casing, yield strength and low intrinsic quality problems.

Tuesday, December 16, 2014

Width, material, temperature and magnet requirements for welded steel pipe

Welded steel pipe strip width, material, temperature and magnet requirements
1 the width of the steel belt and tolerance range are carried out according to the requirements of GB/T3091-2001, cutting edges strip should be adopted in principle.
2 the material of steel belt (weldability), according to the request of GB700.
3 welding temperature: 1350-1380℃, the high frequency furnace frequency: 200-400 KHZ, under the condition of the high frequency equipment must have built-in frequency, frequency of high frequency welding changes with the welded steel pipe diameter and wall thickness.
4 bar (impedance) requirements

NPS Bar OD        NPS Bar OD
1/2" Ф13×140 2" Ф35×200
3/4" Ф18×140 3" Ф30×200×4
1" Ф22×140 4" Ф30×200×7
1 1/4" Ф30×200 5" Ф32×200×7
1 1/2" Ф32×200 6" Ф35×200×7

5 water cooling control.
Induction coil, the magnet, and adjacent squeezing roller device generated large heat due to the high frequency effect, which must strengthen the water flow to cooling, after cooling temperature shall below 400℃. Output transformer and induction coil device also should be passed into the circulating cooling water, and ensure the long-term circulating water outlet water in the running process.
6 high frequency electric resistance welded steel pipe appearance judgment:
6.1 when do normal welding operation, look from the squeezing roller center along the direction of equipment operation should be from coarse to fine, from deep to dark red metal extrusion line.
6.2 by scraping scar device, the burr of the steel pipe can not have split ends.
6.3 by scraping scar, the weld of the steel pipe surface should be a continuous blue strip, line width of 1 -- 3 mm.
6.4 weld reinforcement inside the steel pipe should be full and uniform.

Thermal expansion seamless steel pipe and straight seam steel pipe

Thermal expansion seamless steel pipe and straight seam steel pipe production technology
In terms of the technology processes, the thermal expansion seamless steel pipe and straight seam steel pipe production are almost the same. The large thermal expansion seamless steel pipe is generally using seamless steel pipe of finished, semi-finished seamless steel pipe or seamless steel blanks for secondary processing. On the expansion machine equipment, medium frequency heating the finished seamless steel pipe, semi-finished seamless steel pipe or seamless steel blank, select the appropriate processing of finished steel according to the required specifications, with a suitable mold expand from a small pipe to a bigger one and from coarse to fine. The difference between flaring straight seam steel pipe and thermal expansion seamless steel pipe lies in the the choice of the mother pipe - straight seam or seamless.

Wednesday, December 10, 2014

Treatment for transverse cracks of LSAW steel pipe

Treatment for transverse cracks of LSAW steel pipe
Once confirmed as the transverse crack, the LSAW steel pipe must be sent for rework processing. Transverse crack before repair should be determined the depth and width of gouging and grinding. In order to ensure a thorough rework, the confirmed depth of the ultrasonic testing should be added a few millimeters for margin. Also after gouging and grinding and before re-welding repair, the pipe must be carried out a magnetic particle testing. What should be noted is that the side wall of the groove also belong to the detection range, in order to ensure complete removal of the defect, and then welded by welding personnel, otherwise it would be difficult to ensure the complete eradication of the crack. The low hydrogen welding wire (strip) should be used when repairing, must be preheated before repair, cleaning up after gouging, grinding carbon to the exposed metallic luster, take the necessary protective measures after slow cooling repair, such as the use of asbestos-coated after welding welding sew for slow cooling. In addition, the re-examination of transverse crack repair, must be strictly enforced at 24h or 48h after welding and then check.

Application differences of high-frequency resistance welded steel pipe

Application differences of high-frequency resistance welded steel pipe
The purpose of manufacturing the product is in order to meet certain social functional requirements, pipe production as well. At present, the welded steel pipe has been more and more used in the field of machinery, automotive, energy, large-scale engineering structure and re-processing. Take the development and application of Nippon Steel Pipe Company in the welded steel pipe field for example, its products are related to each of the major areas of industrial production.
The use of high-frequency resistance welded steel pipe is mainly small diameter structural steel pipe, tubing and casing, line pipe and boiler tubes, etc, and this need tends to classify refinement with the changes and advances in production technology and market demand.
In terms of the overall trend of steel pipe: mechanical and structural tube occupies a large proportion, and to maintain the momentum of growth; exclusive possession ratio remains at a certain level. This is closely related to manufacturing technology and its environmental and energy-saving high-strength materials for pipe, so do the leading steel manufacturing technology. Mechanical and structural pipe is right one of the main developing areas of application.
Small diameter welded steel pipe is mainly used in the field of institutional structures, automotive, petroleum, petrochemical, boiler, and high-performance products, high precision, good surface finish, good processing performance as the main direction of development; medium diameter welded steel pipe is mainly used in the field of the petroleum and petrochemical, marine areas, large engineering structures, and the high strength products, high toughness, high corrosion resistance, good weldability and security as the main direction of development. Differences on this demand will lead the medium and small diameter high-frequency resistance welded steel pipe technology tending to extend in different directions.

Installation of plastic composite pipe

Plastic composite pipe is based on the seamless steel pipe and welded steel pipe, inner wall painting with high adhesion, corrosion, hygienic food grade polyethylene powder coating or epoxy painting. After the process of pre-treatment, preheating, inside painting, leveling, and reprocessing, the water galvanizing inner plastic composite pipe is an upgraded product of traditional galvanized steel pipe process, and plastic composite pipe is generally connected with thread.

For the plastic composite pipe during installation, remember not to be buried in concrete. Designer at design time if needed go through the roof and the floor to design a reserve hole, which will be very convenient for future construction . Pipe assembly is certainly received from large diameter to small diameter, according to this law to install it, this is the correct way to facilitate. When a large pipe to be bent, it must be within bending range. Use plastic composite pipe as hot water safety pipeline, we adopt the rubber seal, so as to avoid leakage phenomenon occur during use. During the installation, it must be in accordance with the design drawings for processing, according to the parameters of the above construction. Be sure to check whether it is high-quality fittings, installation is a very important part, playing a very important role for later use.

Plastic composite pipe is based on the seamless steel pipe and welded steel pipe, inner wall painting with high adhesion, corrosion, hygienic food grade polyethylene powder coating or epoxy painting, and is anti-corrosion, corrosion resistance, non-toxic, non-radiation green pipe, used in a variety of fluid transfer. LSAW steel pipe as base pipe shall conform to the requirements of GB / T3091-2008 for the base pipe; seamless steel pipe as base pipe should comply with the requirements of GB / T8163-2008 for the base pipe; and SSAW steel pipe shall comply with the requirements of SY / T5037-2000 for the base pipe.

Monday, December 8, 2014

20 # steel pipe

20 # steel pipe material 20 steel, usually 20 seamless steel pipe
20 # steel pipe material: high-quality carbon structural steel  Grade: 20 Steel Standard: GB / T 699-1988, API5L
● Features and Scope: higher intensity than the 15 steel, very little quenching, no temper brittleness. High cold deformation plasticity, usually for bending, welding performance rolling, curved edges and hammer arch processing, good arc welding and contact welding performance, gas welding with small thickness, shape requires strict or complex shape parts is prone to cracks. Machinability drawn or normalizing state is better than the annealed condition, generally used for manufacturing with low discontinuity and high toughness requirements.
● Chemical Composition: C: 0.17 ~ 0.24 Si: 0.17 ~ 0.37 Mn: 0.35 ~ 0.65 S: ≤0.035 P: ≤0.035 chromium Cr: ≤0.25 Ni: ≤0.25 Cu: ≤0.25.
● Mechanical Properties: Tensile strength σb (MPa): ≥410 (42) yield strength σs (MPa): ≥245 (25) Elongation δ5 (%): ≥25 section shrinkage ψ(%): ≥5, hardness: no heat, ≤156HB, sample size: Sample size 25mm
● Heat treatment and microstructure specifications: Heat treatment specifications: normalizing, 910 ℃, air cooling. Microstructure: ferrite and pearlite.
● Delivery status: no heat treatment or heat treatment (annealing, normalizing or tempering) state delivery. Require heat treatment delivery should be specified in the contract, not indicated by not heat treatment delivery.

City gas pipeline comparisons

Here's three kinds of city gas pipeline network used comparison in terms of the overall performance and comprehensive cost:

(1) Integrated Performance Comparison
 Table I
   Project
  ERW steel pipe
   ductile iron pipe 
      PE  pipe
Tensile strength (Nmm2)
     400
   ≥420
   18-20
Bending strength (Nmm2)
     400
   ≥590
    70
Elongation (%) 
     18
   ≥10
600(elongation at break)
Elastic modulus  (N/mm2)
     20*104
    15-17*104
      0.9*104
Hardness
     140HBS
   230HBS
     50D-70D
corrosion resistance
     poor
   Relative good
    good
Used life (years)
     25-50
   ≥50
    ≥50
construction strength
   Relative small
   Relative small
    small


(2) large diameter pipes comprehensive cost comparison
 Table II
Diameter (mm)
   Type
    OD * WT (mm)
    Cost (yuan / m)
φ150
 Ductile iron pipe
    φ169*6.3
      357
   
 Seamless steel pipe
    φ159*8
      326
   
 ERW steel pipe
    φ168.3*8
      323
   
 PE pipe 
    φ160*14.6
      293
φ200  
 Ductile iron pipe
    φ220*6.4
      433
   
 Seamless steel pipe
    φ219*8
      419
   
    φ219*8
      392  
   
 PE pipe
    φ220*18.2
      402
φ300
 Ductile iron pipe
    φ322.8*7.2
      596
    
 Seamless steel pipe
    φ325*8 
      572
    
 ERW steel pipe
    φ323.9*8
      525
    
 PE pipe
    φ315*28.6
      974
φ400
 Ductile iron pipe
    φ425.6*8.1
      795
   
 Seamless steel pipe
    φ426*8
      908
   
 PE pipe
    φ400*36.4
      1420

Note: 
a.pipe costs are based on prices, fittings and valves expenses by 15% the cost of the meter tube; 
b.by using two layers of steel corrosion tape consideration; 
c.not consider the barriers treatment fee, road restoration and farmland compensation fees; 
d.the unit price based in the year of 2000.