What is a seamless steel tube?

What is a seamless steel tube?

The seamless steel tube is a long strip of steel having a hollow section and no seams around it. Seamless steel tube is generally used for structural purposes and the OD is an important and exact number. Tubing size is specified by OD and the wall thickness (WT); and the measured OD and stated OD are generally within very close tolerances of each other. Seamless steel tube is usually more expensive than seamless steel pipe due to tighter manufacturing tolerances.

Characteristics Pipes vs. Tubes
Types Tube size
Process Pipe size

Characteristics And Uses Of Precision Seamless Steel Tubes

In recent years, the demand for steel products by automobile and real estate enterprises has been large, which has greatly increased the demand for steel products, which has driven the development of the steel market. The steel tube industry is one of the important basic industries in the national economy. Due to the continuous improvement of the living standards of our people and the increasingly good overall economic development, China’s steel tube market has developed rapidly. The demand for the Chinese steel tube market will continue to increase steadily in the future.
Precision seamless steel tubes have the following features:

  1. Light weight, weight is only 1/5 of the square steel.
  2. Corrosion resistance, acid resistance, alkali resistance, salt resistance, atmospheric corrosion resistance, high temperature resistance, impact resistance, fatigue resistance, no regular maintenance. Their effective service life can reach more than 15 years.
  3. The tensile strength is 8-10 times that of ordinary steel, and the elastic modulus is better than steel. It has excellent creep resistance, corrosion resistance and shock resistance.
  4. It has excellent mechanical properties and easy processing.
  5. High elasticity, mechanical equipment reuse, no memory, no deformation, anti-static.

Precision seamless tube is a high-precision steel tube material after cold drawing or hot rolling. Because the inner and outer walls of precision steel tubes have no oxide layer, high pressure and no leakage, high precision, high smoothness, no deformation of cold bending, flaring, flattening and no cracks, they are mainly used to produce pneumatic or hydraulic components as industrial materials. In terms of tight seamless tubes, this is a kind of high-precision, high-gloss, non-deformable steel tube. These steel tubes are used in many fields of industrial production, such as the automobile industry, shipbuilding industry, military industry, etc. The use of precision seamless tubes is completely irreplaceable.

Types of seamless steel tubes

  1. Heat exchanger tubes
  2. Precision seamless steel tubes
  3. ASTM A179 Tube
  4. ASTM A213 T5b tube
  5. Galvanized seamless tube
  6. Double tube
  7. EN 10305 seamless precision steel tube

Heat Exchanger Tubes

heat exchange tube - What is a seamless steel tube?

Heat exchange tubes are intended for heating or cooling process fluids, they are for example suitable for closed circuit cooling of electrical equipment using demineralised water and for cooling water soluble oil solutions in quenching tanks.

Heat exchanger Tubes are used in all types of process industries. Characteristic requirements are: bead worked weld, fixed lengths and extensive testing. In order to meet the demand for rapid delivery, we have a strip stock with both standard and special grades of steel in the most common thicknesses.

Application: For tubular heat exchangers,condensers and similar heat transfer apparatus.
Production Standard, Grade, Steel No: ASTM A179 Heat Exchanger TubesA GB6479 10, 20, 16Mn, 15MnV, 12CrMo, 15CrMo, 12Cr2Mo, 12SiMoVNb
Delivery Conditions:Annealed, Normalized, Normalized and Tempered
Main Testing Terms Accoring to ASTM A213-09 and ASTM A10161. High pressure hydraulic Test: Minimum 10 Maps.2. Eddy current test, Ultrasonic Test3. Mechanical Test4. OD and WT tolerance Test.
Surface treatment:Oil-dip, Varnish, Passivation, Phosphating, Shot Blasting.

Seamless Precision steel tubes

DIN 2391 1 Cold Drawn or Cold Rolled Steel Tube - What is a seamless steel tube?

The seamless precision steel tubes can be used for a wide range of precision mechanical spare for car and cylinder accord to standard:

  • DIN 2391
  • EN10305-1
  • DIN17175 etc

Manufacturing method: cold-rolled / cold-drawn 
Delivery condition: BK,BKS,SR,GBK,NBK.

Acceptance Test Certificate:3.1 according to EN 10204 

Packing: in bundles tied with steel strips. 
External packing by wooden cases if the wall thickness/OD ratio is low. 
Oil-coating is generally necessary especially for export.

Application: 
Used in hydraulic & pneumatic cylinder ,automobile and other mechanical device.

Feature: 
High precision and high brightness, the inner and outer surface of the tubes have high cleanness without oxid, mechanical properties of the final tubes also come out excellent, promising no leakage under high pressure, no deformation after cold-bent and no cracks when flaring and flattening, ensuring the efficient operation in all service.

NBK means protective heat-treating under the non-oxidation enviroment to get a bright and smooth surface for the tubes.

DIN 2391-81 Part 2 precision seamless steel tubes

Standard DIN 2391 defines the technical delivery conditions for seamless precision steel tubes according to DIN 2391 Part 1 which are made from the steel grades listed in section 5.
Tubes according to this Standard are mainly used where accuracy to dimension and, possibly, small wall thicknesses and good surface condition are required.

Chemical composition(%)

Code
number
Material number Mfg. Process C
max
Si
max
Mn
max
P
max
S
max
St35 1.0308 S 0.17 0.35 0.4 0.05 0.05
St45 1.0408 S 0.21 0.35 0.4 0.05 0.05
St52 1.0508 S 0.22 0.55 1.6 0.05 0.05

Mechanical and technological properties

Code number Material number Cold-finished hard(BK) Cold-finished/soft (BKW) 3)
Rm(Mpa) A(%) Rm(Mpa) A(%)
St 35/E235 1.0308 480 6 420 10
St 45 1.0408 580 5 520 8
St 52/E355 1.0508 640 4 580 7
Code number Cold finished (soft)(BKW) Annealed (GBK) Normalized (NBK)
Rm(Mpa) ReH (Mpa) A(%) Rm(Mpa) A(%) Rm (Mpa) ReH (Mpa) A(%)
St 35/E235 420 315 14 315 25 340-470 235 25
St 45 520 375 12 390 21 440-570 255 21
St 52/E355 580 450 10 490 22 490-630 355 22

Note:

  • The yield point for the annealed (GBK)condition on delivery is at least 50% of the (ultimate) tensile strength.
  • Depending upon the degree of deformation in the drawing operation, the yield point of tubes delivered in the cold-finished/hard (BK)and cold-finished/soft(BKW) conditions, may be increased to a level close to the tensile strength.
  • In calculating the yield point, the following values are recommended : cold-finished/hard condition on delivery ≥ 80% of the tensile strength, cold-finished/soft condition on delivery ≥ 70% of the tensile strength.

Quality grade

The tubes are supplied in the following quality grades :

A) precision steel tubes intended primarily for mechanical stressing, without any particular quality requirement and without acceptance test certificate.
B) precision steel tubes intended primarily for mechanical stressing, with special quirement and exclusively with acceptance test certificate.
C) precision steel tubes with special requirement according to section 12. Theses requirements and corresponding tests must be agreed, with the customer having to specify his requirements at the time of enquiry and on ordering.

ASTM A179 Cold Drawn Seamless Carbon Steel Tube

Cold Drawn Seamless Carbon Steel Tube ASTM A179 - What is a seamless steel tube?

ASTM A 179 covers minimum-wall thickness, seamless cold-drawn low-carbon steel tubes for tubular, heat exchanger, condensers, and other heat transfer services. seamless ASTM A 179 steel tube is supplied and produced by cold drawning.

Applications: For tubular heat exchangers,condensers,and similar heat transfer apparatuses.

Chemical composition contains carbon, manganese, phosphorus, and sulfur. Test required: hardness test, flattening test, flaring test, flange test, and hydrostatic test.

Chemistry Composition:

C, %
Mn, %
P, %
S, %
0.06-0.18
0.27-0.63
0.035 max
0.035 max

Mechanical Properties:

Tensile Strength, MPa
Yield Strength, MPa
Elongation, %
Hardness, HRB
325 min
180 min
35 min
72 max

Outside Diameter & Tolerance

Outside Diameter, mm
Tolerance, mm
3.2≤OD<25.4
±0.10
25.4≤OD≤38.1
±0.15
38.1<OD<50.8
±0.20
50.8≤OD<63.5
±0.25
63.5≤OD<76.2
±0.30
76.2
±0.38

Wall thickness & Tolerance

Outside Diamter, mm
Tolerance, %

3.2≤OD<38.1

+20/-0
38.1≤OD≤76.2
+22/-0

Length: 5800mm; 6000mm; 6096mm; 7315mm; 11800mm; and so on.
Max length: 27000mm, also U bending can be offered.

ASTM A213 T5b Seamless alloy tube

ASTM A213 T5b seamless alloy steel pipe - What is a seamless steel tube?

ASTM A213 T5b Standard covers seamless ferritic and austenitic steel boiler, superheater, and heat-exchanger tubes.

ASTM A213 T5b measurment out diameter - What is a seamless steel tube?

Measurment out diameter

ASTM A213 T5b Grades containing the letter H in their designation have requirements different from those of similar grades not containing the letter H.

ASTM A213 T5b measurment wall thickness - What is a seamless steel tube?

Measurment Wall thickness

ASTM A213 T5b measurment length - What is a seamless steel tube?

Measurment Lenth

ASTM A213 T5b packing in wooden boxes - What is a seamless steel tube?

Packing in wooden boxes

These different requirements provide higher creep-rupture strength than normally achievable in similar grades without these different requirements. ASTM A213 T5b tubes shall be made by the seamless process and shall be either hot finished or cold finished, as specified. Grade TP347HFG shall be cold finished. Heat treatment shall be done separately and in addition to heating for hot forming. The ferritic alloy and ferritic stainless steels shall be reheated. On the other hand, austenitic stainless steel tubes shall be furnished in the heat-treated condition. Alternatively, immediately after hot forming, while the temperature of the tubes is not less than the minimum solution temperature, tubes may be individually quenched in water or rapidly cooled by other means. Tension test, hardness test, flattening test, and flaring test shall be done to each tube. Also, each tube shall be subjected to the nondestructive electric test or hydrostatic test.

Mechanical properties for ASTM A213 T5b Low Alloy Steel

  • Other standard specifications include the categories of A209 seamless carbon-molybdenum alloy-steel boiler and superheater tubes;
  • A210 seamless medium-carbon steel boiler and superheater tubes and A213 seamless ferritic and austenitic steel boiler, superheater and heat-exchanger tubes.
  • Piping wall thicknesses range from 1/2 inch to 5 inches.
  • A213 grades also have the letter H or M assigned, which changes the composition and specifications for that series.

This abstract is a brief summary of the referenced standard. It is informational only and not an official part of the standard; the full text of the standard itself must be referred to for its use and application. ASTM does not give any warranty express or implied or make any representation that the contents of this abstract are accurate, complete or up to date.

Chemical Composition(%) for ASTM A213 T5b Low Alloy Steel

UNS Designation K41545
Carbon 0.15
Manganese 0.30–0.60
Phosphorus 0.025
Sulfur 0.025
Silicon 1.00-2.00
Nickel
Chromium 4.00-6.00
Molybdenum 0.45-0.65
Vanadium
Boron
Niobium
Nitrogen
Aluminum
Tungsten
Other Elements

Mechanical properties for ASTM A213 T5b Low Alloy Steel

Tensile strength(min) 415Mpa
Yield strength(min) 205Mpa
Elongation 30%
Hardness, HB 179 max

Permitted tolerance for OD

OD Plus tolerance(+) Minus tolerance (-)
10.29—48.3 0.4 0.4
<48.3—-≤114.3 0.79 0.79
<114.3—≤219.1 1.59 0.79
<219.1—≤323.9 2.38 0.79
<323.9 ±1%

ASTM A213 T5b Standard Scope

1.1 This specification covers seamless ferritic and austenitic steel boiler, superheater, and heat-exchanger tubes, designated Grades T91, TP304, etc. These steels are listed in Tables 1 and 2.
1.2 Grades containing the letter, H, in their designation, have requirements different from those of similar grades not containing the letter, H. These different requirements provide higher creep-rupture strength than normally achievable in similar grades without these different requirements.
1.3 The tubing sizes and thicknesses usually furnished to this specification are 1/8 in. [3.2 mm] in inside diameter to 5 in. [127 mm] in outside diameter and 0.015 to 0.500 in. [0.4 to 12.7 mm], inclusive, in minimum wall thickness or, if specified in the order, average wall thickness. Tubing having other diameters may be furnished, provided such tubes comply with all other requirements of this specification.
1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. Within the text, the SI units are shown in brackets. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in non-conformance with the standard. The inch-pound units shall apply unless the “M” designation of this specification is specified in the order.
TABLE 1 Chemical Composition Limits, %A, for Low Alloy SteelA Maximum, unless range or minimum is indicated. Where ellipses (…) appear in this table, there is no requirement, and analysis for the element need not be determined or reported.

B It is permissible to order T2 and T12 with a sulfur content of 0.045 max. See 16.3.

C Alternatively, in lieu of this ratio minimum, the material shall have a minimum hardness of 275 HV in the hardened condition, defined as after austenitizing and cooling to room temperature but prior to tempering. Hardness testing shall be performed at mid-thickness of the product. Hardness test frequency shall be two samples of product per heat treatment lot and the hardness testing results shall be reported on the material test report.

Referenced Documents (purchase separately)

Other ASTM Standards

  • A262 Practices for Detecting Susceptibility to Intergranular Attack in Austenitic Stainless Steels
  • A941 Terminology Relating to Steel, Stainless Steel, Related Alloys, and Ferroalloys
  • A1016/A1016M Specification for General Requirements for Ferritic Alloy Steel, Austenitic Alloy Steel, and Stainless Steel Tubes
  • E112 Test Methods for Determining Average Grain Size

Galvanized Seamless tube

Galvanized seamless tube - What is a seamless steel tube?

When we discuss seamless steel tube, Seamless steel tube is with a wide range of applications in our construction industry. In general, Galvanized seamless tube is the hot dip galvanized and electro-galvanized two categories.

The first to introduce hot-dip galvanizing, including wet, dry the, lead, zinc, oxidation-reduction method, etc., the process is very complex, the need for technical maturity to complete. Steel tube acid leaching after cleaning, the specific method used to activate the surface of the tube improve the quality of zinc, is not the same, hot dip galvanized main difference.

I do not know understand if understand the electro-galvanized zinc coating surface and compared to a very smooth and dense, homogeneous; the characteristics of the electro-galvanized with good corrosion resistance and mechanical properties; Production is now mainly used in dry and oxidation-reduction method. Coating on one side, the internal and external surfaces of the thickness of the coating on different double-sided smooth coating, and thin-walled tube galvanized to complete this method.

Zinc consumption 60% to 75% lower than the hot-dip galvanizing. Electro-galvanized in the operation of technical and general than there is a certain complexity, which requires high technology and conditions in order to complete.

Double tube, Double wall steel tube

double tube 1 - What is a seamless steel tube?

Double wall tube with two walls. Inside material is so wear resistantace to transport more valume concrete and outside low carbon steel play the role of protection.

DIN 2391-1 Cold Drawn or Cold Rolled Steel Tube

DIN 2391 1 Cold Drawn or Cold Rolled Steel Tube - What is a seamless steel tube?

DIN 2391 standard specifies the Seamless steel tubes used forMechanical and Automobile.

  • for Atuo usd
  • for machinery use
  • Oil cylinder tube
  • Motorcycle shock reducer steel tubes
  • Auto shock reducer inner cylinder

EN 10305 precision seamless steel tube

EN 10305 is for seamless precision steel tube applications. EN 10305 european standard specifies the technical delivery conditions for cold drawn seamless steel tube of circular cross section used in hyhydraulic and pneumatic power systems.

Tubes according to this EN 10305 European standard are characterised by having precisely defined tolerances on dimensions and a specified surface roughness. The allowed pressure rates and temperatures are the responsibility of the customer in accordance with the state of the art and in application of the safety coefficients specified in the application regulations, codes or standards.

Standard and Steel grade:

  • EN10305-1 E215
  • EN10305-1 E235
  • EN10305-1 E355

EN 10305 precision seamless steel tube shall be manufactured from hot finished seamless tubes by cold drawning. Other suitable methods of cold working are permitted. The tubes shall be delivered in the delivery condition +N which means that after the final cold drawing operation the tubes are normalized in a controlled atmosphere.

NBK means protective heat-treating under the non-oxidation enviroment to get a bright and smooth surface for the tubes.

Chemical composition(%) of EN 10305

Steel grade
Name
 Steel
Number
 C(% max)  Si(% max)  Mn(% max)  P(% max)  S(% max)
 E215  1.0212  0.10  0.05  0.70  0.025  0.015
 E235  1.0308  0.17  0.35  1.20  0.025  0.015
 E355  1.0580  0.22  0.55  1.60  0.025  0.015

Mechanical and technological properties of EN 10305

 Yield strength
(min Mpa)
 Tensile strength
(min Mpa)
 Elongation
(min %)
 215  290-430  30
 235  340-480  25
 355  490-630  22

Note:

  • The yield point for the annealed (GBK)condition on delivery is at least 50% of the (ultimate) tensile strength. Depending upon the degree of deformation in the drawing operation, the yield point of tubes delivered in the cold-finished/hard (BK)and cold-finished/soft(BKW) conditions, may be increased to a level close to the tensile strength.
  • In calculating the yield point, the following values are recommended : cold-finished/hard condition on delivery ≥ 80% of the tensile strength, cold-finished/soft condition on delivery ≥ 70% of the tensile strength.

Quality grade

The tubes are supplied in the following quality grades :

A) precision steel tubes intended primarily for mechanical stressing, without any particular quality requirement and without acceptance test certificate.
B) precision steel tubes intended primarily for mechanical stressing, with special quirement and exclusively with acceptance test certificate.
C) precision steel tubes with special requirement according to section 12. Theses requirements and corresponding tests must be agreed, with the customer having to specify his requirements at the time of enquiry and on ordering.

Condition on delivery:

Term Symbol Explanation
Cold-finished/hard
(cold-finished as-drawn)
BK No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.
Cold-finished/soft
(lightly cold-worked)
BKW After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
Annealed GBK After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
Normalized NBK The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

Cold drawn seamless steel tube process

Cold drawn steel tube is with hot-rolled steel coil as raw material, and tandem cold rolling pickled to remove oxide scale, its finished rolling hard roll, rolling hard volumes due to the continuous cold deformation caused by cold hardening strength, hardness increased indicators declined tough plastic, stamping performance will deteriorate, which can only be used for simple deformation of the parts.

Cold drawn seamless steel tube process - What is a seamless steel tube?
Process flow chart of cold drawn seamless steel tube

Rolling hard roll can be used as the raw material of the hot-dip galvanizing plant, hot dip galvanizing line set annealing line. Rolling hard roll weight is generally 6 to 13.5 tons, the coil diameter of 610mm.

Condition on delivery:

Term Symbol Explanation
Cold-finished/hard
(cold-finished as-drawn)
BK No heat treatment after the last cold-forming process. The tubes therefore have only low deformability.
Cold-finished/soft
(lightly cold-worked)
BKW After the last heat treatment there is a light finishing pass (cold drawing) With proper subsequent processing, the tube can be cold-formed (e.g. bent, expanded) within certain limits.
Annealed GBK After the final cold-forming process the tubes are annealed in a controlled atmosphere or under vacuum.
Normalized NBK The tubes are annealed above the upper transformation point in a controlled atmosphere or under vacuum.

Cold drawn seamless steel tubes process:

seamless process Cold Drawn Workshop - What is a seamless steel tube?

round tube → heating → perforation → Heading → annealing → pickling → oiled (copper) → multi-pass cold drawn (cold rolled) → blank tube → heat treatment → straightening →hydrostatic testing (testing) → mark → storage.

The general cold strip mills, volume should go through continuous annealing (CAPL unit) to eliminate cold hardening and rolling stress, or batch annealing reach the mechanical properties of the corresponding standard specifies. Cold rolled steel surface quality, appearance, dimensional accuracy better than hot-rolled plate, and right-rolled thin product thickness is about 0.18mm, so the majority of users favor.

Cold rolled steel coil substrate products deep processing of high value-added products. Such as electro-galvanized, hot dip galvanized, electro-galvanized fingerprint resistant, painted steel roll damping composite steel, PVC laminating steel plates, etc., so that the excellent quality of these products has a beautiful, high resistance to corrosion, has been widely used.

Cold rolled steel coil finishing after annealing, cut the head, tail, trimming, flattening, smooth, heavy volume, or longitudinal clipboard. Cold-rolled products are widely used in automobile manufacturing, household electrical appliances, instruments, switches, buildings, office furniture and other industries. Steel plate strapping package weight of 3 to 5 tons. Flat sub-volume typically 3 to 10 tons / volume. Coil diameter 6m.

Production process of Precision cold drawn steel tube


ASTM A179 cold drawn steel tube - What is a seamless steel tube?

Precision cold drawn steel tube production process

tube weld cracks often follow different mechanisms can be divided into two types of thermal cracking and cold cracking. It is produced by the thermal cracking of a liquid to a solid state crystallization process in the weld metal, mostly generated in the weld metal. The main causes of its low-melting substance is present in the weld, which weakens the contact between the grains when subjected to high welding stress, it is easy to cause breakdown between the grains. Weldments and welding rod containing S, Cu impurities such a long time, it is prone to hot cracking.

Thermal cracking characteristic distribution along the grain boundaries. When the crack through the surface and the outside world, it is a clear tendency hydrogenation. Cold cracks are generated in the cooling process after welding, mostly produced in the base metal or base metal and the weld fusion line junction. The main reason is due to its generation or the weld heat affected zone formed within the quenched structure, under high stress, causing rupture of grains, the higher the carbon content of the welding elements, or more easily hardened alloy steel, the most prone to cold cracking. Excessive weld melt into hydrogen, can also cause cold cracking. A defect of the most dangerous cracks, which in addition to reducing the cross-section than the bearing, but also produce severe stress concentration at the crack will gradually expand in use, may eventually lead to the destruction member. So welded structures are generally not permitted the existence of such defect has been found to be a shovel to re-welding.

Steel tube internal defects of weld lack of penetration is refers to the workpiece and the weld metal or weld layer between local incomplete fusion of a defect. Incomplete penetration welds weakened section of the work, causing serious stress concentration, greatly reduce joint strength, it is often a source of weld cracking. Weld slag sandwiched nonmetallic slag, that is called slag. Weld slag reduces work-section, resulting in stress concentration will reduce weld strength and toughness.

Porosity of the weld metal at high temperatures, the absorption due to too much gas or gas dissolved within the cell is generated by the reaction of metallurgical, too late when the bath is discharged is cooled and solidified, and the weld hole is formed inside or the surface, i.e. pores. The presence of pores reduces the effective work of the weld cross-section, to reduce the mechanical strength of the joint. If penetrating pores or continuity exists, it will seriously affect the tightness of the weldment. After cracking during welding or welding metal in the welded joints appearing partial rupture area called crack. Cracks may occur in the weld may also be produced in the weld heat affected zone on both sides. Sometimes occurs on the metal surface, the metal may be generated internally.

Thermal Expansion Treatment Of Seamless Steel Tube

The seamless expansion of the seamless steel tube is divided into an overall thermal expansion treatment, a surface thermal expansion treatment, and a chemical heat treatment. The seamless expansion of the seamless steel tube is generally treated by integral thermal expansion. Generally, they are subjected to basic processes such as heating, heat preservation, and cooling, and defects may occur in these processes.
Heat treatment defects of seamless steel tubes mainly include unqualified structural properties of steel tubes, excessive size and surface cracks, scratches, severe oxidation, decarburization, overheating, and over-burning.
Features of thermal expansion processing of seamless steel tubes:
The first process is heating: one is heating below the critical point Ac1 or Ac3; the other is heating above the critical point Ac1 or Ac3. The first is mainly to stabilize the structure of the seamless steel tube and to eliminate the residual stress of the seamless steel tube, and the second is mainly to austenitize the steel.
The second process is thermal insulation: the purpose is to uniformly heat the heating temperature of the steel tube to obtain a reasonable heating structure.
The third process is cooling: the cooling process is a key process in the heat treatment of seamless steel tubes. He determines the metallographic structure and mechanical properties of the tubes after cooling. The steel tube cooling methods used in the actual production process are various. The cooling methods often used are furnace cooling, air cooling, oil cooling, polymer cooling, and water cooling.

Heat Treatment Process Classification Of Seamless Steel Tubes

Seamless steel tube heat treatment is divided into three categories:

  • (1) Final heat treatment to meet the performance requirements of seamless steel products;
  • (2) heat treatment in the heat treatment state required by users and standards;
  • (3) heat treatment between processes in the steel tube manufacturing process.

The commonly used heat treatment processes for seamless steel tubes mainly include quenching, tempering, normalizing and annealing. For example: casings, oil tubes, drill tubes, line tubes, etc. in oil special tubes, according to the level of steel grade, the normalizing, normalizing and tempering, quenching and tempering processes are adopted accordingly;
High-pressure boiler tubes and high-pressure fertilizer tubes often use normalizing, normalizing and tempering, quenching and tempering (thick-walled tubes) and solid solution treatment of austenitic stainless steel tubes; spheroidizing annealing of steel tubes for bearings.
Some alloy steel tubes with high alloy content, in order to prevent users from cracking and deformation before use, users and standards usually require the manufacturer to deliver in heat treatment state, and seamless steel production plants need to perform heat treatment such as annealing and normalizing. The heat treatment between the processes is used in the production process of cold-rolled and cold-drawn steel tubes, and recrystallization annealing and softening annealing are usually employed. The purpose is to eliminate the cold work hardening effect, reduce the hardness and improve the toughness to facilitate further cold working.

Thick-walled Seamless Steel Tube Processing Performance

  1. Thick-walled seamless steel tube castability (castability): refers to the ability of metal materials to obtain qualified castings by casting. Casting properties mainly include fluidity, shortening and segregation. Fluidity refers to liquid metal filling molds. Capability, shortening refers to the degree of volume shortening when the casting is condensed. Segregation refers to the non-uniformity of the chemical composition and arrangement of the metal during the cooling and condensation process due to the difference in crystallization.
  2. Thick wall seamless steel tube forgeability: refers to the metal material can change the shape without cracking during pressure processing. It can be hammered, rolled, stretched, twisted in hot or cold state. Pinch and other processing. The quality of forgeability is primarily related to the chemical composition of metal materials.
  3. Thick-walled seamless steel tube machinability (cuttability, machinability): refers to the ease with which a metal material becomes a qualified workpiece after being machined by a tool. The machinability is good and the surface roughness of the workpiece is usually processed. It is measured by the cutting speed and the degree of wear of the tool.  It is related to many factors such as the chemical composition, mechanical function, thermal conductivity and degree of work hardening of the metal material. It is usually roughly judged by the hardness and the resistance for the machinability. Generally speaking, the higher the hardness of the metal material, the harder it is to cut. The hardness is not high, but the resistance is large and the cutting is difficult.
  4. Weldability (weldability): refers to the customary function of metal materials for welding processing. Firstly, it refers to the difficulty of obtaining high-quality welded joints under certain welding process conditions. It contains two aspects: Combined function, that is, under certain welding process conditions, the certain metal constitutes the sensitivity of welding defects, and the second is the application of the function, that is, the certain metal welding joints have the applicability to the application requirements under certain welding process conditions.

Pipes vs. Tubes

To an outsider, pipes and tubes may seem like they should be synonymous. To a marine engineer, the measurements, standards and language used to distinguish the two couldn’t be more different. In fact, differences in nomenclature and measurements could cause quite the headache if tubes and pipes were mistakenly assumed to be interchangeable.

The 7 Main Differences Between Pipes and Tubes

  • Tubes can come in different shapes like square, rectangular and cylindrical. Pipe is always cylindrical or round.
  • While rigid tubes are frequently used in structural applications, copper and brass tubes can be rather flexible. Pipes are typically always rigid and resistant to bending.
  • When it comes to classification, pipes use schedule and nominal diameter. For example, a pipe could have a 250mm nominal diameter and a schedule of 80. Tubes are classified by their outside diameter measurement and thickness. A copper tube, for instance, could be 10 mm with a 2 mm thickness.
  • Pipes accommodate larger applications with sizes that range from a half-inch to several feet. Tubes are generally used in applications that require smaller diameters. While 10-inch pipes are common, it’s rare that you will come across a 10-inch tube.
  • Tubes are often put to use in applications that require precise outside diameters, like with cooler tubes, heat exchanger tubes and boiler tubes.
  • Pipes have a pressure rating and are schedule, which is why they are often used to carry fluids that must be contained.
  • The thickness of tubes increases in standard increments such as 1 mm or 2 mm. Pipe thickness depends on the schedule, so there is no fixed increment.
  • Joining pipes is more labor intensive as it requires welding, threading or flanges. Tubes can be joined quickly and easily with flaring, brazing or couplings, but for this reason, they don’t offer the same stability.

pipe vs tube - What is a seamless steel tube?

How do i choose which pipe size or tube size to use for my project?

We are often asked this question by our customers and due to the number of possible variables there isn’t always an easy answer. We do offer a “standard” suggestion to all of our customers when asked which pipe size or tube size to use:

  1. If you’re building a turbo manifold we almost always suggest using pipe size. The added thickness of pipe size, when compared to tube size, will provide more longevity and be far less prone to cracking. Pipe size, due to its thickness, is far more robust than tube size, especially when you hang a 20-40 pound turbo off of the side, heat the material up to incredibly high temperatures, and then add vibration and stress into the equation. Also, most aftermarket head flanges meant for turbo applications are optimized for either 1-1/4″ or 1-1/2″ pipe size. It is extremely easy to find a suitable head flange for almost all applications these days and we often suggest, as a baseline, using components that utilize the same size for the primaries and the head flange. 
  2. If you’re building a traditional set of headers for a non-turbo application we almost always suggest using tube size (including mandrel bendsstraight lengths of tube, and either pre-formed merge collector or fabricating your own using a bandsaw and various lengths of straight tube). In the case of building traditional headers for non-turbo applications, the added thickness, and therefore weight, of pipe size is more detrimental than beneficial.
  3. If you’re building any other component of an exhaust system, including a downpipe, a cat-back, or replacing existing, yet aging exhaust piping we always suggest using tube size (mandrel bends, straight tube, exhaust flanges and gaskets, etc.). Tube size is light, yet robust enough to be used for almost every portion of your exhaust system. Also, almost all mufflersresonatorscatalytic converters, and exhaust flanges are based on common tube sizes — using off-the-shelf products to complete your exhaust system is far more cost effective than having to fabricate everything by yourself using non-standard sizes. Lastly, the added weight of pipe size makes it unsuitable for almost all exhaust applications.
  4. If you’re building your own intercooler piping was always suggest tube size (mandrel bendsstraight tubev-band assembliesdual seal clamps, or VanJen assemblies, etc.). Aluminum is by far the most common choice, yet some fabricators choose to use stainless steel material for their intercooler piping. 

If you have any questions regarding what type of material to use, or what size to use, please do not hesitate to contact us.

Tube size

round tubing sizes ace race parts tube chart for common exhaust turbo manifold and sizes tubing size for bumper - What is a seamless steel tube?

Pipe size

weight dimensions of schedule pipe stainless steel table metric - What is a seamless steel tube?

Notes:

[*] 16 gauge is typically referenced as 0.065″ in both the automotive and industrial industries. However, ASTM A269 tolerances state that there can be up to a 10% variation from the stated wall thickness For example, material ranging from 0.500″ to 5.500″ outside diameter. For material in this size range 16 gauge material can technically range from 0.0585″ at a minimum to 0.0715″ at a maximum. However, most stainless tube manufacturers tend to produce 16 gauge tube with a wall thickness that ranges between 0.059″ and 0.065″ thick. 

Source: China Seamless Steel Tube Manufacturer – Yaang Pipe Industry Co., Limited (www.ugsteelmill.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

If you want to have more information about the article or you want to share your opinion with us, contact us at sales@ugsteelmill.com

Please notice that you might be interested in the other technical articles we’ve published:

References:

  • https://www.yaang.com
  • wwww.orldwidemetric.com
  • https://www.steeljrv.com/how-to-get-high-quality-precision-seamless-pipe.html

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