Industry advantages of 15crmo alloy steel pipe
Related standards and uses of seamless steel tubes:
1.GB/T8162-2008 (seamless steel pipe for structure). Mainly used for general structural and mechanical structures. Its representative material (brand): carbon steel, 20, 45 steel; alloy steel Q345, 20Cr, 40Cr, 20CrMo, 30-35CrMo, 42CrMo and so on.
2. GB/T8163-2008 (seamless steel pipe for conveying fluid). Mainly used for conveying fluid pipelines on engineering and large equipment. Representative material (brand) is 20, Q345
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3.GB3087-2008 (seamless steel pipe for low and medium pressure boilers). It is mainly used for pipes for conveying low and medium pressure fluids in industrial boilers and domestic boilers. The representative material is steel No. 10 and No. 20.
4.GB5310-2008 (seamless steel pipe for high pressure boiler). It is mainly used for high temperature and high pressure conveying fluid gathering boxes and pipelines on power stations and nuclear power plant boilers. Representative materials are 20G, 12Cr1MoVG, 15CrMoG, etc.
5.GB5312-2009 (carbon steel and carbon-manganese steel seamless steel pipe for ships). It is mainly used for I and II pressure pipes for ship boilers and superheaters. Representative materials are 360, 410, 460 steel grades, etc.
6.GB6479-2000 (seamless steel pipe for high pressure fertilizer equipment). It is mainly used to transport high temperature and high pressure fluid pipelines on fertilizer equipment. Representative materials are 20, 16Mn, 12CrMo, 12Cr2Mo and the like.
7.GB9948-2006 (seamless steel pipe for petroleum cracking). Mainly used in boilers, heat exchangers and pipelines for conveying fluids in petroleum smelters. The representative materials are 20, 12CrMo, 1Cr5Mo, 1Cr19Ni11Nb and the like.
8.GB18248-2000 (seamless steel pipe for gas cylinders). Mainly used to make various gas and hydraulic cylinders. The representative materials are 37Mn, 34Mn2V, 35CrMo, and the like.
In addition, there are GB/T17396-1998 (hot rolled seamless steel pipe for hydraulic props), GB3093-1986 (high pressure seamless steel pipe for diesel engine), GB/T3639-1983 (cold drawn or cold rolled precision seamless steel pipe), GB /T3094-1986 (cold drawn seamless steel pipe shaped steel pipe), GB/T8713-1988 (precision inner diameter seamless steel pipe for hydraulic and pneumatic cylinders), GB13296-1991 (stainless steel seamless steel pipe for boilers and heat exchangers), GB/T14975 -1994 (stainless steel seamless steel pipe for structure), GB/T14976-1994 (stainless steel seamless pipe for fluid transportation) GB/T5035-1993 (seamless steel pipe for automobile semi-axle casing), API?SPEC5CT-1999 (casing and Tubing specifications) and so on.
2. Welding steel pipe standard
Welded steel pipe is also called a welded pipe which is formed by welding a steel plate or a steel strip after being crimped. The welded steel pipe has simple production process, high production efficiency, many varieties and specifications, and less equipment, but the general strength is lower than that of seamless steel pipe. Since the 1930s, with the rapid development of high-quality strip continuous rolling production and the advancement of welding and inspection technology, the quality of welded joints has been continuously improved, the variety specifications of welded steel pipes have been increasing, and more and more fields have replaced Seam steel pipe. Welded steel pipes are divided into straight welded pipes and spiral welded pipes in the form of welds. Straight seam welded pipe has simple production process, high production efficiency, low cost and rapid development. The strength of the spiral welded pipe is generally higher than that of the straight welded pipe. It is possible to produce a welded pipe with a large diameter by using a narrow blank, and it is also possible to produce a welded pipe having a different pipe diameter by using a blank of the same width. However, compared with the straight pipe of the same length, the weld length is increased by 30 to 100%, and the production speed is low. Therefore, most of the smaller diameter welded pipes are straight seam welded, and the large diameter welded pipes are mostly spiral welded.
1. Welded steel pipe for low-pressure fluid transportation (GB/T3092-1993) is also called general welded pipe, commonly known as black pipe. It is a welded steel pipe used for conveying general lower pressure fluids such as water, gas, air, oil and heating steam and other purposes. The thickness of the steel pipe is divided into ordinary steel pipe and thick steel pipe; the pipe end form is divided into non-threaded steel pipe (light pipe) and threaded steel pipe. The specification of the steel pipe is expressed by the nominal diameter (mm), and the nominal diameter is an approximate value of the inner diameter. It is customary to use inches, such as 11/2. The welded steel pipe for low-pressure fluid transportation is mainly used as a raw pipe for galvanized welded steel pipe for low-pressure fluid transportation, in addition to being directly used for conveying fluid.
2. Galvanized welded steel pipe for low pressure fluid transportation (GB/T3091-1993) is also called galvanized electric welded steel pipe, commonly known as white tube. It is a hot dip galvanizing (furnace welding or electric welding) steel pipe for transporting water, gas, air oil, heating steam, warm water and other general lower pressure fluids or other purposes. The thickness of the steel pipe is divided into ordinary galvanized steel pipe and thick galvanized steel pipe; the connection end form is divided into non-thread galvanized steel pipe and threaded galvanized steel pipe. The specification of the steel pipe is expressed by the nominal diameter (mm), and the nominal diameter is an approximate value of the inner diameter. It is customary to use inches, such as 11/2.
3. Ordinary carbon steel wire casing (GB3640-88) is a steel pipe used to protect electric wires in electrical installation projects such as industrial and civil construction, installation machinery and equipment.
4. Straight seam electric welded steel pipe (YB242-63) is a steel pipe whose weld is parallel to the longitudinal direction of the steel pipe. Usually divided into metric electric welded steel pipe, welded thin-walled pipe, transformer cooling oil pipe and so on.
5. General spiral spiral submerged arc welded steel pipe (SY5037-2000) for low-pressure fluid transportation is made of hot-rolled steel strip coil for tube blank, regular temperature spiral forming, double-sided automatic submerged arc welding or single-sided welding method. Submerged arc welded steel pipes for general low-pressure fluid transportation such as water, gas, air and steam.
6. Spiral welded steel pipe for pile (SY5040-2000) is made of hot-rolled steel strip as tube blank, which is often spiral-formed by double-sided submerged arc welding or high-frequency welding. It is used for civil engineering structures and docks. Steel pipes for foundation piles such as bridges.
3. Stainless steel pipe material standard
GB2270-80 stainless steel seamless steel pipe
GB/T14976-94 stainless steel seamless pipe for fluid transportation
GB/T14975-94 stainless steel seamless steel pipe for structure
GB13296-91 Stainless steel seamless steel pipe for boilers and heat exchangers
(GJB2608-96)(YB676-73) Structural steel thick-walled seamless steel pipe for aviation
(GJB2296-95)(YB678-71) Aerospace stainless steel seamless pipe
(YB/T679-97)(YB679-71) 18A hollow rivet thin-walled seamless steel pipe for aviation
(GJB2609-96)(YB680-71) Thin-walled seamless steel pipe for aviation
(YB/T681-97)(YB681-71) Aeronautical conduit 20A thin-walled seamless steel pipe
GB3090-82 stainless steel small diameter steel pipe
GB5310-95 seamless steel pipe for high pressure boiler
GB3087-82 low and medium pressure seamless steel pipe
GB3089-92 stainless acid and acid resistant thin wall seamless steel pipe
GB9948-88 petroleum cracking seamless steel pipe
ASTM A213 Ferritic and austenitic alloy steel seamless tubes for boilers and heat exchangers
ASTM A269 General purpose austenitic stainless steel seamless steel pipe and welded steel pipe
ASTM A312 austenitic stainless steel seamless steel pipe welded steel pipe welded steel pipe
General requirements for ASTM A450 carbon steel, ferritic and austenitic alloy steel tubes
General requirements for ASTM A530 special purpose ferritic and alloy steels
ASTM A789 generally requires carbon austenitic stainless steel seamless steel tubes and welded steel tubes
JIS G3456-88 Stainless steel tube for mechanical structure
JIS G3448-88 Stainless steel pipe for ordinary pipes
JIS G3459-88 stainless steel pipe for pipes
JIS G3463-88 Stainless steel tube for boilers and heat exchangers
Q/HYAD 101-91 Seamless long steel pipe for chemical industry (0Cr18NI11T)
Q/HYAD 103-91 00Cr18Ni5MO3Si2 duplex stainless steel seamless pipe
[15CrMo alloy steel pipe knowledge]:
15crmo alloy steel pipe: steel-based pearlite heat-resistant steel, which has high heat strength (δb≥440MPa) and oxidation resistance at high temperature, and has certain resistance to hydrogen corrosion. Due to the high content of Cr, C and other alloying elements in the steel, the hardening tendency of the steel is obvious and the weldability is poor.
15CRMO alloy steel pipe 15CrMo weldability
Welding materials: For the working characteristics of 15CrMo steel weldability, based on past experience, we have selected two options for welding test with reference to the welding process card provided by foreign countries.
Solution I: Welding preheating, using ER80S-B2L welding wire, T1G welding base, E8018-B2 welding rod, electrode arc welding cover surface, local heat treatment after welding. Scheme II: ER80S-B2L welding wire, T1G welding base, E309Mo-16 electrode, welding rod filling arc welding cover, no heat treatment after welding. The chemical composition and mechanical properties of the welding wire and welding rod are shown in Table 1.
15crmo alloy steel pipe chemical composition: Material C Si Mn Mo Cr
15CrMo 0.12~0.18 0.17~0.37 0.40~0.70 0.40~0.55 0.80~1.10
Chemical composition and mechanical properties of welding materials
Model C Mn Si Cr Ni Mo SP δb/Mpa δ,%
ER80S-B2L≤0.05 0.70.41.2 <0.20.5 ≤0.025 ≤0.025 ≤500 25
E8018-B2 0.070.7 0.3 1.1 0.5 ≤0.04 ≤0.03 550 19
E309Mo-16≤0.12 0.5～2.5 0.9 22.0～25.0 12.0～14.0 2.0～3.0≤0.025≤0.035 550 25
Preparation before welding
The test piece is made of 15CrMo steel pipe, the specification is φ325×25, and the groove type and size are shown in Figure 1.
Prior to welding, an angle grinder was used to polish the inside and outside of the groove and the edge of the groove to a thickness of 50 mm to expose the metallic luster, and then cleaned with acetone.
The test piece is a horizontal fixed position, the matching gap is 4mm, and six points are uniformly spot-welded along the circumference by manual tungsten argon arc welding, and the length of each point is not less than 20mm. The electrode is baked according to the specifications in Table 2.
2 electrode baking specifications
Welding rod type baking temperature holding time
E8018-B2 300 °C 2h
E309Mo-16 150 °C 1.5h
3 welding process parameters
According to the scheme I, preheating is required before welding, and the formula for calculating the preheating temperature is proposed according to Tto-Bessyo et al.
To=350√[C]-0.25(°C) where To is the preheating temperature, °C.
[C]=[C]x [C]p [C]p=0.005S[C]x
[C]x=C (Mn Cr)/9 Ni/18 7Mo/90
[C]x - component carbon equivalent;
[C]p——size carbon equivalent; S——test piece thickness (S=25mm in this paper);
[C]x=C (Mn Cr)/9 7/90Mo=0.361
[C]p=0.045 then To=138°C
Therefore, the preheating temperature was selected to be 150 °C. The test piece is heated by the oxygen-acetylene flame. Firstly, the temperature of the surface of the test piece is roughly judged by the temperature measuring pen (estimated by the change of the color of the handwriting), and finally measured by a semiconductor thermometer, and at least three points should be selected for the measurement point. In order to ensure that the test piece as a whole meets the required preheating temperature.
When welding, the first layer is made of manual tungsten argon arc welding. In order to avoid the depression on the back of the weld at the anvil weld, the inner wire is used for wire feeding, that is, the wire is fed from the pipe through the gap. The remaining layers are electrode-welded, welding 6 layers, one weld bead per weld. The welding process parameters of Scheme I and Scheme II are shown in Tables 3 and 4. Solder according to the scheme I
3 Scheme I welding process parameters
Weld name welding method welding material welding material specification / mm welding current / A arc voltage / V preheating and interlayer temperature heat treatment specifications
Tungsten plate argon arc welding ER80S-B2L φ2.4 110 12
Filled layer electrode arc welding E8018-B2 φ3.2 5 85～90 23～25150°C 715. ×75min
Cover surface electrode arc welding E8018-B2 φ3.2 5 85～90 23～25
3 welding procedure parameters of scheme II
Weld name welding method welding material welding material specification / mm welding current / A arc voltage / V preheating and interlayer temperature heat treatment specifications
Tungsten plate argon arc welding ER80S-B2L φ2.4 110 12
Filled layer electrode arc welding E309Mo-16 φ3.2 90～95 22～24 / /
Cover surface electrode arc welding E309Mo-16 φ3.2 90～95 22～24
When connecting, the interlayer temperature should not be lower than 150 °C. In order to prevent the cooling of the test piece caused by interrupting the welding, the two welders should be alternately operated during the welding, and the insulation and cold cooling measures should be taken immediately after the welding.
Welding procedure qualification test
After the test piece is welded, 100% ultrasonic flaw detection shall be carried out according to JB4730-94 "Non-destructive testing of pressure vessels", and the weld bead grade I is qualified. According to JB4708 "Steel Pressure Vessel Welding Process Evaluation" standard, the welding procedure qualification test is carried out. The evaluation results are shown in Table 5.
4 Welding procedure qualification test results
Test protocol tensile test bending test impact toughness test aky (J/cm2)
Tensile strength δb/Mpa fracture site bending angle surface bending back weld seam fusion line heat affected zone (HAZ)
Option I 550/530 Base metal 50. Qualified 84.8 162 135.6
Scheme II 525/520 Base metal 50. Qualified 79.4 109.2 96.7
It can be seen from the tensile test results that the tensile specimens of the two schemes are all broken in the base metal, indicating that the tensile strength of the weld is higher than that of the base metal; the bending test is all qualified, indicating that the weld has good plasticity. According to the impact toughness test results in Table 5, the impact toughness of the scheme I is significantly higher than that of the scheme II, which proves that the post-weld heat treatment specification of the scheme I is ideal, and the high-temperature tempering not only achieves the purpose of improving joint structure and performance, but also makes the toughness The strength is matched properly. From the results of mechanical properties at room temperature, the two recommended welding process solutions can be used for on-site construction. Scheme I uses an electrode that is close to the composition of the base metal. The weld performance is matched with the base metal. The weld should have high heat strength, and the weld seam is not easily damaged after long-term use at high temperatures. The difficulty is that the post-weld heat treatment specification is stricter, and the tempering temperature and holding time and improper heating and cooling speed control may cause the weld bead performance to decrease. Scheme II uses austenitic stainless steel welding rod welding, although the post-weld heat treatment can be omitted, but due to the different expansion coefficient of the weld and the base metal, carbon diffusion and migration can occur during long-term high-temperature work, which easily leads to the weld in the fusion zone. Destruction occurred. Therefore, from the perspective of reliability of use, it is safer to use the scheme I in the field.
in conclusion
It is feasible to use two welding schemes for welding 15CrMo steel thick-walled high-pressure pipes. In order to ensure that the weld bead performance is matched with the base metal and has high heat strength, the effect of the scheme I is better, and the key is to strictly control the post-weld heat treatment process.
Although Scheme II can eliminate the post-weld heat treatment, the possibility of weld migration at the high temperature and the weld seam is not negligible. Therefore, it can only be used cautiously when heat treatment cannot be performed after welding.
Steel pipe weight calculation formula: [(outer diameter - wall thickness) * wall thickness] * 0.02466 = kg / m (weight per meter)
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