CN109530849B - Welding construction method for carbon steel pipeline in acidic environment - Google Patents

Welding construction method for carbon steel pipeline in acidic environment Download PDF

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CN109530849B
CN109530849B CN201811438028.8A CN201811438028A CN109530849B CN 109530849 B CN109530849 B CN 109530849B CN 201811438028 A CN201811438028 A CN 201811438028A CN 109530849 B CN109530849 B CN 109530849B
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welding
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carbon steel
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CN109530849A (en
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张城
李阳
余尚林
李翔
杜和
杨燕
张圆
肖景安
黄勇
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Sichuan Petroleum Construction Engineering Co Ltd
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Sichuan Petroleum Construction Engineering Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/0026—Arc welding or cutting specially adapted for particular articles or work
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/16—Arc welding or cutting making use of shielding gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K9/00—Arc welding or cutting
    • B23K9/235—Preliminary treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass

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  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Arc Welding In General (AREA)
  • Heat Treatment Of Articles (AREA)

Abstract

The invention provides a welding construction method of a carbon steel pipeline in an acidic environment, which comprises the following steps: controlling the components of the carbon steel pipeline, and performing groove machining on the carbon steel pipe; assembling the carbon steel pipes subjected to groove machining, and preheating the welding port area of the assembled carbon steel pipes; root welding the preheated weld zone area by using a first welding material; carrying out hot welding, filling welding and cover surface welding on the preheated weld zone area by using a second welding material; and carrying out nondestructive testing and postweld heat treatment to complete the welding of the carbon steel pipeline. According to the method, the problem that after the acid carbon steel pipeline is welded, the weld joint is high in performance strength and hardness, so that the weld joint is easy to corrode and crack due to SSC sensitivity can be solved; the method can solve the problems that after the acid carbon steel pipeline is welded, the S, P, O content in the weld joint structure is high, and impurities such as oxide and sulfide are generated to seriously affect the purity of the weld joint, so that the toughness of the weld joint is reduced.

Description

Welding construction method for carbon steel pipeline in acidic environment
Technical Field
The invention belongs to the technical field of welding, and particularly relates to a carbon steel pipeline welding construction method in an acidic environment.
Background
In the petroleum and chemical industry, the production device for treating the hydrogen sulfide-containing medium mostly adopts carbon steel equipment, however, the carbon steel equipment is easily corroded by hydrogen sulfide and damaged, the condition of forced production stop for maintenance can be caused, and the production is very unfavorable. The method for welding the carbon steel pipeline in the acid environment of the petroleum and natural gas has no unified technical requirements all the time, and no mature sulfur-resistant carbon steel pipeline welding related cases exist in China.
Therefore, a welding method which starts from meeting the requirements of corrosion resistance and physical and chemical properties of a welding line in an acid environment, ensures the welding quality of carbon steel in the acid environment by strictly controlling key links such as welding materials, a welding process, postweld heat treatment and the like, better meets the requirements of development of an oil and gas acid gas field and pipeline construction, prolongs the service life of a pipeline and reduces the maintenance and repair costs is urgently needed.
Disclosure of Invention
In view of the deficiencies in the prior art, it is an object of the present invention to address one or more of the problems in the prior art as set forth above. For example, one of the purposes of the invention is to solve the problems that after the acid carbon steel pipeline is welded, the weld joint is high in performance strength and hardness, and is easy to corrode and crack due to SSC sensitivity; the problem of hydrogen induced cracking caused by hydrogen embrittlement of a welding seam due to hydrogen bubbling in the welding seam after the welding of the acid carbon steel pipeline is solved; the problem that after the acid carbon steel pipeline is welded, local tensile stress is generated due to local stress concentration or residual stress concentration, and sulfide stress corrosion cracking is induced under the action of a hydrogen sulfide-containing medium is solved; the method solves the problems that after the acid carbon steel pipeline is welded, the S, P, O content in the weld joint structure is high, and the purity of the weld joint is seriously influenced by impurities such as oxide and sulfide, so that the toughness of the weld joint is reduced.
The invention provides a carbon steel pipeline welding construction method in an acidic environment, wherein the carbon steel pipeline comprises the following chemical components in percentage by mass: less than or equal to 0.16 percent of C, less than or equal to 0.45 percent of Si, less than or equal to 1.65 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.008 percent of S, less than or equal to 0.35 percent of Cu, less than or equal to 0.30 percent of Ni, less than or equal to 0.30 percent of Cr, less than or equal to 0.15 percent of Mo, less than or equal to 0.07 percent of V, less than or equal to 0.05 percent of Nb, less than or equal to 0.060 percent of Al, less than or equal to 0.04 percent of Ti, less than or equal to 0.0005 percent of B, less than or equal to 0.006 percent of Ca, less than or equal to 0.012 percent of N, and the balance of Fe and inevitable impurities; the welding construction method may include the steps of: controlling the components of the carbon steel pipeline, and performing groove machining on the carbon steel pipe; assembling the carbon steel pipes subjected to groove machining, and preheating the welding port area of the assembled carbon steel pipes; root welding the preheated weld zone area by using a first welding material; carrying out hot welding, filling welding and cover surface welding on the preheated weld zone area by using a second welding material; carrying out nondestructive testing and postweld heat treatment to complete carbon steel pipeline welding, wherein the first welding material comprises the following chemical components in percentage by mass: 0.06-0.15% of C, less than or equal to 1.35% of Mn, Si: 0.45 to 0.75 percent of the total weight of the alloy, less than or equal to 0.008 percent of S, less than or equal to 0.020 percent of P, less than or equal to 0.15 percent of Cr, less than or equal to 0.15 percent of Ni and less than or equal to 0.50 percent of Cu; the deposited metal chemical components of the second welding material comprise the following components in percentage by mass: less than or equal to 0.15 percent of C, less than or equal to 1.35 percent of Mn, less than or equal to 0.90 percent of Si, less than or equal to 0.005 percent of S, less than or equal to 0.020 percent of P, less than or equal to 0.20 percent of Cr, less than or equal to 0.30 percent of Ni, less than or equal to 0.30 percent of Mo, and less than or equal to 0.080 percent of V.
In an exemplary embodiment of the welding construction method of the carbon steel pipeline in the acid environment, the yield strength of the first welding material may be 400 to 484MPa, and the tensile strength may be 480 to 570 MPa; the yield strength of the second welding material can be 360 MPa-460 MPa, and the tensile strength can be 450 MPa-550 MPa.
In an exemplary embodiment of the welding construction method of the carbon steel pipeline in the acidic environment, the post-welding heat treatment may include raising the temperature to 380-430 ℃, raising the temperature to 610-640 ℃ at a temperature raising speed of not more than 200 ℃/h, keeping the temperature for a time period t, lowering the temperature to 380-430 ℃ at a temperature lowering speed of not more than 260 ℃/h, and cooling to room temperature, wherein when the thickness of the carbon steel pipeline is not more than 25mm, the temperature keeping time t is 0.8-1.2 h; when the thickness of the carbon steel pipeline wall is more than 25mm, the heat preservation time t is at least (0.8+ (b-25)/25) h to (1.2+ (b-25)/25) h, and b represents the thickness of the carbon steel pipeline wall, and the unit is millimeter.
In an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acidic environment, the groove may be a V-shaped groove, the truncated edge of the groove may be 0.5mm to 1.5mm, the groove angle may be 60 degrees to 70 degrees, and the root gap may be 2.5mm to 3.5 mm.
In an exemplary embodiment of the welding construction method of the carbon steel pipeline in the acid environment, the preheating temperature may be 100-150 ℃, and the preheating width may be 90-110 mm on each side of the welding seam.
In an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acid environment, the root welding can adopt argon arc welding upward welding, and the flow of the shielding gas can be 10L/min-15L/min.
In an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acid environment, the hot welding can adopt shielded metal arc welding, the welding interlayer temperature can be 100-200 ℃, and the welding interval time between the root welding and the hot welding can not exceed 10 min;
in an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acid environment, the filling welding can adopt welding rod arc upward welding, and the welding layer temperature can be 100-200 ℃.
In an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acid environment, the facing welding can adopt electrode arc upward welding.
In an exemplary embodiment of the welding construction method of the carbon steel pipeline in the acid environment, the interval between the nondestructive testing start time and the welding completion time is more than 24 h.
Compared with the prior art, the invention has the beneficial effects that: the problem that after the acid carbon steel pipeline is welded, the weld joint is high in performance strength and hardness, and the weld joint is prone to corrosion cracking due to SSC sensitivity can be solved; the problem of hydrogen induced cracking caused by hydrogen embrittlement of a welding seam due to hydrogen bubbling in the welding seam after the welding of the acid carbon steel pipeline can be solved; the problem that after the acid carbon steel pipeline is welded, local tensile stress is generated due to local stress concentration or residual stress concentration, and sulfide stress corrosion cracking is induced under the action of a hydrogen sulfide-containing medium can be solved; the method can solve the problems that after the acid carbon steel pipeline is welded, the S, P, O content in the weld joint structure is high, and the purity of the weld joint is seriously influenced by impurities such as oxide, sulfide and the like, so that the toughness of the weld joint is reduced.
Drawings
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
fig. 1 is a schematic flow chart illustrating an exemplary embodiment of a welding construction method for carbon steel pipelines in acidic environment according to the present invention.
Fig. 2 shows a welding groove schematic diagram of an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acid environment.
Fig. 3 shows a heat treatment process curve diagram of an exemplary embodiment of the welding construction method of the carbon steel pipeline in the acid environment.
Detailed Description
Hereinafter, a welding construction method of carbon steel pipes in an acid environment according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.
Fig. 1 is a schematic flow chart illustrating an exemplary embodiment of a welding construction method for carbon steel pipelines in acidic environment according to the present invention. Fig. 2 shows a welding groove schematic diagram of an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acid environment. Fig. 3 shows a heat treatment process curve diagram of an exemplary embodiment of the welding construction method of the carbon steel pipeline in the acid environment.
In an exemplary embodiment of the welding construction method for the carbon steel pipeline in the acidic environment of the present invention, as shown in fig. 1, the welding construction method may include:
and step S01, controlling the components of the carbon steel pipeline and performing groove machining on the carbon steel pipe.
In order to improve the resistance of carbon steel to hydrogen sulfide corrosion in an acidic environment, prolong the service life of a pipeline and reduce maintenance, the chemical composition of the carbon steel pipe needs to be controlled. The carbon steel pipe comprises the following chemical components in percentage by mass: less than or equal to 0.16 percent of C, less than or equal to 0.45 percent of Si, less than or equal to 1.65 percent of Mn, less than or equal to 0.02 percent of P, less than or equal to 0.008 percent of S, less than or equal to 0.35 percent of Cu, less than or equal to 0.30 percent of Ni, less than or equal to 0.30 percent of Cr, less than or equal to 0.15 percent of Mo, less than or equal to 0.07 percent of V, less than or equal to 0.05 percent of Nb, less than or equal to 0.060 percent of Al, less than or equal to 0.04 percent of Ti, less than or equal to 0.0005 percent of B, less than or equal to 0.006 percent of Ca, less than or equal to 0.012 percent of N, and the balance of Fe and inevitable impurities. Further, the carbon steel pipe comprises the following chemical components in percentage by mass: less than or equal to 0.14 percent of C, less than or equal to 0.43 percent of Si, less than or equal to 1.59 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.008 percent of S, less than or equal to 0.32 percent of Cu, less than or equal to 0.30 percent of Ni, less than or equal to 0.30 percent of Cr, less than or equal to 0.15 percent of Mo, less than or equal to 0.07 percent of V, less than or equal to 0.05 percent of Nb, less than or equal to 0.060 percent of Al, less than or equal to 0.03 percent of Ti, less than or equal to 0.0005 percent of B, less than or equal to 0.006 percent of Ca, less than or equal to 0.012 percent of N, and the balance of Fe and inevitable impurities.
The microscopic metallographic structure of the carbon steel pipeline is fine-grain pearlite and ferrite. In order to improve the hydrogen sulfide corrosion resistance of the acid pipeline welding seam, the welding material is required to be controlled to have good weldability, the strength, the mechanical property and the chemical composition of the welding seam are controlled to be matched with those of the carbon steel pipeline, and the content of S, P, O in the welding material is controlled to improve the purity of the welding seam, so that the toughness and the plasticity of the welding seam are improved, and the sulfur and hydrogen corrosion resistance and cracking resistance of the welding seam are improved.
In this embodiment, as shown in fig. 2, the groove may be a V-groove. The blunt edge a of the groove can be 0.5-1.5 mm, and further, the blunt edge can be 0.75-1.25 mm. The groove angle β may be 60 ° to 70 °, and further, the groove angle may be 62 ° to 68 °. The root gap b may be 2.5 to 3.5mm, and further, the root gap may be 2.75 to 3.25 mm. The advantage that sets up above-mentioned truncated edge lies in can enough preventing to appear burning through the phenomenon when the root welding, also can avoid the root welding to weld thoroughly. If less than its set lower limit, root burn-through is likely to occur, and if greater than its set upper limit, lack of penetration is likely to occur. The groove angle has the advantages that the weld penetration can be guaranteed, the strength is increased, the process defects are reduced, the deposited metal using amount and the dilution rate of the base metal can be controlled, and the welding accessibility of a welding gun can be guaranteed. If the welding angle is lower than the lower limit value of the set groove angle, the welding gun cannot reach the root to carry out welding, the dilution rate of deposited metal is increased, and process defects are easy to generate; if the amount is higher than the upper limit value, the amount of deposited metal is increased, and the cost is increased.
And step S02, pairing the carbon steel pipes subjected to groove machining, and preheating welded junction areas of the paired carbon steel pipes.
In this embodiment, the preheating temperature may be 100 ℃ to 150 ℃, and further, the preheating temperature may be 115 ℃ to 135 ℃. The preweld preheating at the temperature set by the invention has the advantages that the preheating energy is used for slowing down the cooling speed after welding, so that the diffusion hydrogen in the welding seam is favorably overflowed, the generation of hydrogen-induced cracks is avoided, and the welding seam and a heat affected zone can be prevented from generating hardening tissues to cause brittle fracture. If the temperature range exceeds the set temperature range, the effect of further improving the welded joint is not obvious, on the contrary, not only the metal grains in the welding seam and the heat affected zone are coarse, even widmannstatten structures are generated, but also the heating cost is greatly increased, and the economic benefit is reduced. The preheating should be performed uniformly on both sides and in the circumferential direction of the crater, and local overheating should be prevented. The width of preheating can be 90 mm-110 mm respectively for both sides of the welding seam. Further, the width may be 100mm on both sides of the weld. The set range covers the heat affected zone during welding, namely, a welding seam, a heat affected zone and a base metal, and the preheating of the range can meet the requirements of the welding joint for diffusing hydrogen to overflow and preventing the formation of a hardened structure. If the temperature exceeds the range, the effect of further improving the welded joint is not obvious, but the weld joint and the heat affected zone not only have coarse metal grains and even generate widmannstatten structures, but also cause great increase of heating cost, and the economic benefit is reduced. In the preheating process, a temperature measuring instrument can be adopted to detect the preheating temperature.
In step S03, root welding is performed on the preheated weld notch area with the first welding material.
In this embodiment, the preheating temperature is maintained at 100-150 ℃, and the first welding material can be used to perform root welding by argon arc welding. The flow rate of the shielding gas during root welding can be 10L/min-15L/min. Under certain conditions, the gas flow and the diameter of the nozzle have an optimal range, the gas protection effect is optimal at the moment, the effective protection area is the largest, the flow range can ensure that the airflow stiffness is good, the capacity of removing surrounding air is strong, turbulence is prevented from being generated to cause air to be involved, and the protection effect is reduced. If the flow is too low, the airflow stiffness is not good and the capacity of eliminating ambient air is poor; too high flow rate can produce turbulence and entrainment of air to reduce the protective effect. The shielding gas may be argon (99.99%), although the shielding gas used in the present invention is not limited thereto. When the invention is used for root welding, the welding is divided into a plurality of sections which are symmetrically and uniformly distributed so as to reduce the welding stress.
The deposited metal chemical components of the first welding material comprise the following components in percentage by mass: 0.06-0.15% of C, less than or equal to 1.35% of Mn, Si: 0.45 to 0.75 percent of the total weight of the alloy, less than or equal to 0.008 percent of S, less than or equal to 0.020 percent of P, less than or equal to 0.15 percent of Cr, less than or equal to 0.15 percent of Ni, less than or equal to 0.50 percent of Cu, and the balance of iron and inevitable impurities. Further, the deposited metal chemical composition of the first welding material comprises the following components in percentage by mass: 0.06-0.12% of C, less than or equal to 1.30% of Mn, Si: 0.45 to 0.69 percent of the total weight of the alloy, less than or equal to 0.005 percent of S, less than or equal to 0.014 percent of P, less than or equal to 0.15 percent of Cr, less than or equal to 0.15 percent of Ni and less than or equal to 0.50 percent of Cu.
The yield strength of the first welding material can be 400 MPa-484 MPa, and the tensile strength can be 480 MPa-570 MPa. Furthermore, the yield strength of the first welding material can be 421-463 MPa, and the tensile strength can be 502-548 MPa. The first welding material is mainly used for root welding, and by adopting the welding material with the strength grade higher than that of the base metal, the hidden danger that a welding seam is very weak and stress and even cracking are easily generated due to external influence when root welding is carried out can be avoided, and the risk of corrosion and cracking of the welding seam can be increased under an acidic environment. If the yield strength and the tensile strength of the arrangement are not achieved, the plastic toughness of the welding line is greatly reduced, and the risks of hydrogen induced cracking and sulfide cracking of the welding line in an acid environment are greatly increased.
In this embodiment, in the root welding process, the root welding joint can be smoothly ground to ensure good back formation of the weld joint.
And step S04, performing hot welding, filling welding and cover welding on the preheated welded junction area by using a second welding material.
In the present embodiment, the craters are subjected to thermal welding and filling welding with the second welding material. The deposited metal chemical components of the second welding material comprise the following components in percentage by mass: less than or equal to 0.15 percent of C, less than or equal to 1.35 percent of Mn, less than or equal to 0.90 percent of Si, less than or equal to 0.005 percent of S, less than or equal to 0.020 percent of P, less than or equal to 0.20 percent of Cr, less than or equal to 0.30 percent of Ni, less than or equal to 0.30 percent of Mo, less than or equal to 0.080 percent of V, and the balance of iron and inevitable impurities. Further, the deposited metal chemical composition of the second welding material comprises the following components in percentage by mass: less than or equal to 0.13 percent of C, less than or equal to 1.32 percent of Mn, less than or equal to 0.88 percent of Si, less than or equal to 0.005 percent of S, less than or equal to 0.015 percent of P, less than or equal to 0.20 percent of Cr, less than or equal to 0.29 percent of Ni, less than or equal to 0.30 percent of Mo, and less than or equal to 0.080 percent of V.
The yield strength of the second welding material is 360 MPa-460 MPa, and the tensile strength is 450 MPa-550 MPa. Furthermore, the yield strength of the second welding material can be 367MPa to 445MPa, and the tensile strength can be 456MPa to 538 MPa. The second welding material has the advantages that the strength of the second welding material is matched with that of the base metal in an equal strength mode, so that the plasticity and toughness of the welding line are improved, and the hydrogen induced cracking resistance and sulfide cracking resistance of the welding line in an acidic environment are improved. If the above-mentioned range is exceeded, the weld may have a reduced plastic toughness, thereby reducing the hydrogen-induced cracking resistance and sulfide cracking resistance of the weld in an acidic environment.
In this embodiment, the heat welding should be started as soon as possible after the root welding is completed. For example, the time interval between root welding and hot welding does not exceed 10 min. The hot welding can adopt shielded metal arc welding, the interlayer temperature can be 100-200 ℃, and an infrared thermometer can be used for detecting the interlayer temperature.
The control of the preheating temperature and the interlayer temperature of the welding seam can prevent the formation of a high-hardness microstructure in a heat affected zone, improve the plasticity and toughness of the welding seam and further increase the capability of resisting the corrosion of hydrogen sulfide.
In this embodiment, the filler weld may be an arc up weld using a welding rod. The interlayer temperature during welding can be controlled to be 100-200 ℃. The interlayer temperature is controlled in the range, which is equal to the effect that the previous welding pass plays a preheating role for the next welding pass, thereby not only facilitating the overflow of diffused hydrogen, reducing the cooling speed and avoiding the formation of a hardening structure, but also preventing the metal grains in the welding line and the heat affected zone from being thick due to overhigh temperature and even generating a Widmannstatten structure. When the temperature is lower than the lower limit value of the range, the welding seam is easy to generate temperature internal stress, and simultaneously, the cooling speed is increased, and a hardening structure is easy to generate; above the upper limit of the range, the metal grains in the welding seam and the heat affected zone are coarse and even generate Widmannstatten structures.
In this embodiment, when the wall thickness of the pipeline is thick, the filling welding can adopt multi-pass swing welding to ensure that the molten pool can be effectively protected, and the two sides of the groove should be well fused.
In this embodiment, the electrode should be replaced immediately when the second welding material is found to be red or arcing.
In this embodiment, the facing welding may employ a stick-type arc up welding. The interval time between the filling welding completion time and the cover surface welding starting time has no specific requirement, and the interlayer temperature is 100-200 ℃.
In this embodiment, when the groove is wide, for example, when the width exceeds 14mm, the cover surface welding may adopt row welding, and the subsequent welding seam should cover at least 1/3 of the previous welding seam, and should ensure smooth transition of the welding seam and the base material, and reduce welding stress concentration as much as possible and cover at least 1/3 of the previous welding seam, which not only facilitates detachment of defects such as blowholes in the previous welding seam, but also performs heat treatment on the welding seam, thereby improving plasticity and toughness of the welding seam. If 1/3 of the previous welding seam cannot be covered, the defects such as air holes and the like in the previous welding seam cannot be separated, and the heat treatment effect is not obvious. After the cover surface welding is finished, a steel wire brush can be used for removing slag of the welding seam and splashes on two sides of the welding seam, the appearance quality of the welding seam is checked by using a welding check ruler, and if the standard-exceeding defect exists, the repair treatment is carried out in time.
And step S05, performing nondestructive testing on the welding seam.
In the embodiment, the weld joint is delayed to crack, and the weld joint can be subjected to nondestructive detection after welding is completed for 24h, wherein the nondestructive detection can adopt 100% RT and 100% UT.
In this embodiment, the root weld must not be undercut, and the ray detection should be used to determine the undercut.
In this embodiment, the detection method may employ both the radiation detection and the ultrasonic detection. Meanwhile, ray detection and ultrasonic detection are adopted to detect various defects such as three-dimensional and two-dimensional defects generated in the welding seam to the maximum extent, so that the problem that the hydrogen sulfide resistance of the welding seam is reduced due to missing detection of the defects is avoided as much as possible.
And step S06, performing heat treatment on the welding seam.
In this embodiment, the weld and the 3-fold weld width regions on both sides thereof may be heat treated. The heat treatment is used for reducing the residual stress of the weld joint and increasing the plastic toughness of the weld joint, thereby improving the hydrogen sulfide corrosion resistance of the weld joint. As shown in FIG. 3, first at t1During the time period, the temperature is raised from the ambient temperature to T1，T1May be 380 to 430 ℃ and may further be 386 to 420 ℃ such as 400 ℃. The temperature rise rate can be any value, for example, the temperature rise rate can be 210 ℃/h-240 ℃/h. t is t1The time period can be confirmed according to the temperature rising speed. Heating to a temperature T1Then, with v1Is increased to t by the temperature increase speed of2Is raised to the temperature T at any moment2. The temperature rising speed v1Less than or equal to 200 ℃/h, and further, the temperature rising speed v1185 ℃ per hour or less, for example 180 ℃ per hour. Temperature T2May be 610 ℃ to 640 ℃, further may be 620 ℃ to 630 ℃, and for example, may be 625 ℃. Heating to a temperature T2Thereafter, the heating was stopped and the temperature was maintained for a period of t (t in FIG. 3)3-t2Time period). And after keeping the temperature for t time period, starting cooling treatment. May be given as v2Cooling is performed at a cooling rate of (1). Cooling rate v2260 ℃/h or less, and further, v2240 ℃/h or less, for example, 230 ℃/h. Passing through t4-t3After a period of time, the temperature is cooled to T1I.e. cooled to 380-430 ℃. Then cooled to room temperature.
And when the thickness of the carbon steel pipeline wall is not more than 25mm, the heat preservation time t can be 0.8 h-1.2 h. Further, the heat preservation time can be 0.85 h-1.14 h. For example, it may be 0.9 h. When the wall thickness of the carbon steel pipeline is more than 25mm, the heat preservation time t can be not less than (0.8+ (b-25)/25) h to (1.2+ (b-25)/25) h, wherein b represents the wall thickness of the carbon steel pipeline and has the unit of millimeter.
The heat preservation temperature of the heat treatment is set to be 610-640 ℃, so that the range belongs to high-temperature tempering, tempered sorbite, namely a ferrite and fine-particle cementite mixture can be obtained, the residual internal stress of the welding seam can be reduced, and the plasticity and the toughness of the welding seam can be improved. If it is outside the above range, a structure and phase transformation may occur, thereby changing the mechanical properties of the weld. Further, the heat preservation temperature can be 620-630 ℃, and further, the heat preservation temperature can be 625 ℃.
For the general-diameter carbon steel pipe, the heat preservation time can be 50-70 min. The holding time is set so that not only carbon atoms are uniformly diffused to form an equilibrium structure phase, but also coarse grains are prevented. If the heat preservation time is too short, carbon atoms can not be effectively diffused, and the formed tissue is not uniform; too long a time may cause coarsening of the crystal grain structure. Further, the heat preservation time can be 55-65 min, and further, the heat preservation time can be 60 min.
The rate of temperature rise of the heat treatment to 380 to 430 ℃ or lower is not limited, and the temperature at this temperature or lower has little influence on the diffusion rate of carbon atoms and therefore has little influence on the structure to be formed. The temperature raising rate of 380 to 430 ℃ or higher may be less than 200 ℃/h, for example, 50 to 150 ℃/h. The temperature rise speed is set to facilitate the diffusion of carbon atoms to be more sufficient, so that the components of the grain structure are more uniform, the defects of the grain structure are reduced, and the residual stress is reduced, thereby improving the plasticity and the toughness of the welding line. If the temperature rises too fast, carbon atoms in crystal grains are not sufficiently diffused, so that the structural components are not uniform, the effect of reducing the stress of the welding seam cannot be realized, and the plasticity and the toughness of the welding seam cannot be improved. In the cooling process, the cooling rate of 380-430 ℃ or higher may be less than 260 ℃/h, for example, 65-195 ℃/h. The cooling speed is set, so that ferrite and pearlite structures with good plasticity and toughness can be generated, and the corrosion resistance of the welding seam is improved. If the cooling rate is too high, even exceeding the critical cooling rate of the metal, a martensite structure with high hardness and brittleness may be generated, which greatly reduces the acid corrosion resistance of the weld metal. The cooling speed below 380-430 ℃ is not limited, and because the influence of the cooling speed below 380-430 ℃ on carbon atom diffusion, tissue morphology and stress is small, the construction cost can be controlled and the economic benefit can be improved without controlling the cooling speed.
In this embodiment, the thermal treatment may be performed by a crawler-type or a rope-type electrical heating, for example, the model of the thermal treatment device may be WDK-FS-612060T, the thermal treatment device belongs to a control device which is automatically controlled and selects a programmable sequence input mode, the temperature control and heating power input of the thermal treatment device are performed by an intelligent temperature control device, after the thermal treatment process parameters are input, the whole thermal treatment process is automatically completed according to the input parameters, and the thermal treatment temperature data and the curve can be printed and output, so that the accuracy of the thermal treatment can be effectively ensured.
In conclusion, the method can enable the average value of the crack length rate, the average value of the crack thickness rate and the average value of the crack sensitivity rate of the welding joint to meet the standard and the design requirements in the HIC and SSC performance detection and Hydrogen Induced Cracking (HIC) test of the standard solution; the test piece has no surface crack in a Sulfide Stress Cracking (SSC) test of the welding joint; in practical production application, the corrosion resistance effect of the carbon steel pipeline in an acidic environment is greatly improved, and the leakage rate of the pipeline due to corrosion is reduced; maintenance and repair costs can be reduced.
While the present invention has been described above in connection with the accompanying drawings and exemplary embodiments, it will be apparent to those of ordinary skill in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.

Claims (5)

1. The welding construction method of the carbon steel pipeline in the acidic environment is characterized by comprising the following steps:
the carbon steel pipeline comprises the following chemical components in percentage by mass: c is more than or equal to 0.14% and less than or equal to 0.16%, Si is less than or equal to 0.45%, Mn is less than or equal to 1.65%, P is less than or equal to 0.02%, S is less than or equal to 0.008%, Cu is less than or equal to 0.35%, Ni is less than or equal to 0.30%, Cr is less than or equal to 0.30%, Mo is less than or equal to 0.15%, V is less than or equal to 0.07%, Nb is less than or equal to 0.05%, Al is less than or equal to 0.060%, Ti is less than or equal to 0.04%, B is less than or equal to 0.0005%, Ca is less than or equal to 0.006%, N is less than or equal to 0.012%, and the balance is Fe and inevitable impurities, the metallographic microstructure of the carbon steel pipe is pearlite and ferrite, the groove is a V-type groove, the blunt edge of the groove is 0.5mm to 1.5mm, the angle is 60 to 70%, and the root gap is 2.5mm to 3.5 mm;
assembling the carbon steel pipes subjected to groove machining, and preheating the welding port area of the assembled carbon steel pipes;
carrying out root welding on the preheated weld crater area by using a first welding material, wherein the root welding adopts argon arc welding upward welding, the flow of protective gas is 10-15L/min, and the deposited metal chemical components of the first welding material comprise the following components in percentage by mass: c: 0.12-0.15%, Mn is less than or equal to 1.35%, Si: 0.45-0.75 percent of the first welding material, less than or equal to 0.008 percent of S, less than or equal to 0.020 percent of P, less than or equal to 0.15 percent of Cr, less than or equal to 0.15 percent of Ni, less than or equal to 0.50 percent of Cu, 400-484 MPa of yield strength of the first welding material, and 480-570 MPa of tensile strength;
carrying out hot welding, filling welding and cover surface welding on the preheated weld crater area by using a second welding material, wherein the hot welding adopts shielded metal arc welding, the welding interlayer temperature is 100-200 ℃, the welding interval time between root welding and the hot welding is not more than 10min, and the deposited metal chemical composition of the second welding material comprises the following components in percentage by mass: c is more than or equal to 0.13% and less than or equal to 0.15%, Mn is less than or equal to 1.35%, Si is less than or equal to 0.90%, S is less than or equal to 0.005%, P is less than or equal to 0.020%, Cr is more than or equal to 0.20%, Ni is more than or equal to 0.30%, Mo is more than or equal to 0.30%, V is more than or equal to 0.080%, the yield strength of the second welding material is 360-460 MPa, and the tensile strength is 450-550 MPa;
performing nondestructive testing and postweld heat treatment to complete the welding of the carbon steel pipeline,
the postweld heat treatment comprises the steps of heating to 380-430 ℃, then heating to 610-640 ℃ at a heating rate not higher than 200 ℃/h, keeping the temperature for t time period, then cooling to 380-430 ℃ at a cooling rate not higher than 260 ℃/h, cooling to room temperature, wherein,
when the thickness of the carbon steel pipeline is not more than 25mm, the heat preservation time t is 0.8 h-1.2 h;
when the wall thickness of the carbon steel pipeline is more than 25mm, the heat preservation time t is at least (0.8+ (b-25)/25) h to (1.2+ (b-25)/25) h, and b represents the wall thickness of the carbon steel pipeline and has the unit of millimeter.
2. The welding construction method of the carbon steel pipeline in the acid environment according to claim 1, wherein the preheating temperature is 100-150 ℃, and the preheating width is 90-110 mm on each of two sides of the welding seam.
3. The welding construction method for carbon steel pipelines in acidic environment according to claim 1, wherein the filling welding adopts electrode arc upward welding, and the welding interlayer temperature is 100-200 ℃.
4. The welding construction method for the carbon steel pipeline in the acid environment according to claim 1, wherein the facing welding adopts electrode arc upward welding.
5. The construction method for welding carbon steel pipes in acidic environment according to claim 1, wherein the interval between the nondestructive testing start time and the welding completion time is greater than 24 h.
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