Electro-gas welding method of quenched and tempered high-strength steel plate for large oil storage tank pressure vessel

Abstract

The invention discloses an electro-gas welding method of a quenched and tempered high-strength steel plate for a large oil storage tank pressure vessel, which comprises the following steps: 1) when high-strength steel is refined, adding a Ca-Mg-Ce alloy block after refining; (2) when a welding test plate is prepared, a V-shaped groove with the angle of 22.5-34.5 degrees is adopted when the thickness size is smaller than 25 mm; an asymmetric X-shaped groove is adopted above 25 mm, the outer side of the groove angle ranges from 23 degrees to 33 degrees, and the inner side of the groove angle ranges from 48 degrees to 69 degrees; (3) assembling the welding test plates, and reserving an assembling gap; (4) electrogas welding is carried out on one side face of the opening face of the V-shaped groove or the outer side face of the asymmetric X-shaped groove, a side face welding seam is formed, and the other side face of the welding test plate is forcibly cooled; and (5) electrogas welding is conducted on the other face, namely the inner side face, of the asymmetric X-shaped groove, an inner side back face welding seam is formed, and a copper water cooling test block with a notch is additionally arranged on the completed outer side face welding seam for forced cooling. A welding joint has excellent low-temperature toughness; and during heat input welding, the three areas of the joint have high impact toughness reserve and safety margin.

Description

Technical Field

[0001] The invention relates to the field of iron and steel metallurgy, and in particular to a gas-electric vertical welding method for tempered high-strength steel plates for large oil storage tank pressure vessels, and a high-wire energy gas-electric vertical welding method for tempered high-strength steel plates 12MnNiVR for large oil storage tank pressure vessels. Background Art

[0002] 12MnNiVR steel plate has the characteristics of wear resistance, heat resistance and corrosion resistance, and is a material commonly used in large oil storage tank pressure vessels. The construction of large storage tanks and spherical tanks puts higher requirements on the structure of steel plates and their welding technology, including the use of high-efficiency welding with large line energy. Gas-electric vertical welding is one of the efficient welding methods commonly used to increase the welding line energy of 12MnNiVR steel thick plates. In the mid-to-late 1980s, China has begun to introduce gas-electric vertical welding equipment and has been successfully applied in various large-scale oil, natural gas and other storage tank manufacturing industries.

[0003] However, it is difficult to control the welding quality of gas-electric welding, and the toughness of the heat-affected zone is low. In order to improve the microstructure and properties of 12MnNiVR steel gas-electric welding joints, trace elements such as Ti, Nb, Ca, and Mg are added to the steel to improve the welding performance by pinning austenite grains or forming intragranular precipitation. 2 O 3 , and finally developed into today's composite precipitation spheroidization modification control of Ca, Mg oxides or sulfides, which meets the purpose of increasing welding line energy.

[0004] At present, the industrial production and application of steel plates for high heat input welding in my country are mainly in the two fields of crude oil storage tanks and shipbuilding, and there is a lack of steel plate production with a welding line energy greater than 100KJ / cm. The reason is that when domestic enterprises develop steel for high line energy welding, they usually use the traditional TiN particle pinning mechanism of austenite and intragranular ferrite nucleation particles to avoid the coarsening of austenite grains in the heat affected zone of welding, and at the same time, needle-shaped ferrite is formed in the coarse grain zone of the heat affected zone to improve the impact toughness of the coarse grain zone of welding. Using this method, under the condition of effective control of the production process, although the steel plate can withstand the requirement of line energy reaching about 100KJ / cm. However, during the welding heat cycle, when the temperature reaches 1350℃, more than 50% of TiN will dissolve. When the temperature of the fusion line reaches or exceeds 1400℃, the dissolved volume fraction can even reach more than 80%, resulting in a significant weakening of the pinning effect. In addition, the composite precipitation with TiN as the particle is the key factor in the formation of intragranular ferrite. The process of TiN dissolution and secondary precipitation during cooling during welding further weakens the mechanism of TiN as the precipitation particle of composite particles such as MnS, affects the formation of intragranular ferrite in the coarse-grained area, and leads to fluctuations in welding performance.

[0005] Therefore, it is necessary to develop a new type of high-strength steel plate 12MnNiVR high-wire energy gas-electric vertical welding method for large oil storage tank pressure vessels to overcome the above problems. Summary of the invention

[0006] Purpose of the invention: In view of the shortcomings and defects of the prior art, the present invention provides a gas-electric vertical welding method for tempered high-strength steel plates for large oil storage tank pressure vessels, the welding joint Rm ≥ 540MPa, the joint cold bending d = 3a, 180° qualified, the weld impact energy -20℃ KV2 ≥ 57J, the fusion line impact energy -20℃ KV2 ≥ 70J, the heat affected zone (fusion line + 1mm)

[0007] -20℃KV2≥66J; the joint has excellent low-temperature toughness; when increasing the line energy welding, the three zones of the joint have a higher impact toughness reserve and safety margin.

[0008] Technical solution: The present invention provides a gas-electric vertical welding method for tempered high-strength steel plates for large oil storage tank pressure vessels, characterized in that it comprises the following steps:

[0009] 1) Before welding, in order to meet the performance index requirements of high-strength steel plate 12MnNiVR with high line energy, Ca-Mg-Ce alloy blocks are added after refining to make the weight percentage of Ca, Mg and Ce in molten steel ≤0.0005%;

[0010] 2) When preparing the welding test plate, a V-shaped groove with an angle of 22.5° to 34.5° is used for thickness below 25mm; an asymmetric X-shaped groove with an outer groove angle of 23° to 33° and an inner groove angle of 48° to 69° is used for thickness above 25mm; the outer groove depth t = 1 / 2a + 2mm to 4mm is set according to the thickness of the steel plate, where a is the thickness of the steel plate, and no blunt edge is left on the groove;

[0011] 3) Pair the welding test plates, leaving a gap of 3mm to 6mm;

[0012] 4) For the open surface of the V-shaped groove or the outer surface of the asymmetric X-shaped groove, perform gas-electric vertical welding on one side to form a side weld, and install a copper triangular water-cooling test block on the other side of the welding test plate for forced cooling;

[0013] 5) Perform gas-electric vertical welding on the other side of the asymmetric X-shaped groove, i.e., the inner side, to form an inner back weld. A copper water-cooled test block with a notch is installed on the completed outer side weld for forced cooling. Complete the gas-electric vertical welding of the tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels.

[0014] Wherein, the thickness of the quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessel is 20mm to 40mm.

[0015] The chemical composition of the quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels is as follows by weight: C: 0.08% to 0.11%, Si: 0.20% to 0.30%, Mn: 1.37% to 1.53%, P: ≤0.015%, S: ≤0.0050%, Ni: 0.20% to 0.50%, Mo: 0.10% to 0.30%, V: 0.02% to 0.06%, Ti: 0.01% to 0.025%, Alt: 0.025% to 0.035%, and the balance is Fe and unavoidable impurities; when the high-strength steel 12MnNiVR is refined, a Ca-Mg-Ce alloy block is added after refining so that the weight percentages of Ca, Mg and Ce in the molten steel are all ≤0.0005%.

[0016] Among them, the quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels needs to be modulated after hot rolling: the steel plate at room temperature is heated to 900°C to 920°C with the furnace, and the insulation time is extended by 15min to 30min on the basis of the steel billet being burned through, and after being taken out of the furnace, it is immersed in a water tank for quenching; the tempering heat treatment heating temperature is 620°C to 650°C, and the furnace time is 3.3t+30min, where t is the thickness of the steel plate; after the quenching and tempering heat treatment, the metallographic structure obtained is a tempered troostite structure.

[0017] Wherein, in the step 2), the roughness of the processed surface of the welding test plate groove is ≤Ra20.

[0018] After the assembly in step 3) is completed, manual arc welding, CO 2 Gas shielded welding or hydrogen arc welding is used to perform tack welding on both ends and the middle of the completed welding test plate. The weld length of each tack weld is ≥15mm, the weld height is ≥4mm, and the interval length between adjacent tack welds shall not exceed 300mm.

[0019] Wherein, the protective gas in step 4) and step 5) is carbon dioxide gas, CO 2 The gas volume percentage is ≥98%, and the gas flow rate is controlled at 26L / min~28L / min.

[0020] Wherein, in step 4) and step 5), the welding current is 360A-420A, the welding voltage is 36V-41V, and the welding speed is 5cm / min-17cm / min.

[0021] Wherein, the welding line energy of the gas-electric vertical welding in the steps 4) and 5) is ≥100KJ / cm; the welding test plates are paired, and a pairing gap is reserved for front gas-electric vertical welding to form a front weld, and a copper triangular water-cooling test block is installed on the back of the welding test plate for forced cooling; back gas-electric vertical welding is performed to form a back weld, and the completed front weld is installed with a copper water-cooling test block with a notch for forced cooling.

[0022] Among them, the welding joint Rm≥540MPa, the joint cold bending d=3a, 180° qualified, the weld impact energy -20℃ KV2≥57J, the fusion line impact energy -20℃ KV2≥70J, and the heat affected zone -20℃ KV2≥66J.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0024] When the high-strength steel 12MnNiVR of the present invention is refined, a Ca-Mg-Ce alloy block is added after refining, so that the weight percentages of Ca, Mg and Ce in the molten steel are all ≤0.0005%, and the alloy block is used for secondary weak deoxidation and microalloying addition except for aluminum deoxidation. Ca-Mg-Ce has extremely strong affinity with O and S in steel, and is easy to generate oxides, sulfides and composite compounds of Ca-Mg-Ce, with a melting point of more than 3000°C and good thermal stability. The fine and dispersed Ca-Mg-Ce oxygen-sulfur compound second phase particles formed can inhibit the coarsening of austenite at high temperature during high-heat input welding, increase the intracrystalline ferrite nucleation rate, promote the formation of fine needle-shaped ferrite structure in the crystal, and improve the impact performance of the coarse-grained zone of the weld, so as to improve the high-heat input welding.

[0025] The quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels of the present invention needs to be modulated after hot rolling. The measured mechanical properties of the steel plate are ReL≥600MPa, Rm≥670MPa, A≥19%, -20℃ KV2 impact energy≥270J, and the performance is excellent. The welded joint Rm≥540MPa, the joint cold bending d=3a, 180° qualified, the weld impact energy -20℃ KV2≥57J, the fusion line impact energy -20℃ KV2≥70J, and the heat affected zone (fusion line+1mm) -20℃ KV2≥66J. The joint has excellent low-temperature toughness; when the line energy is increased for welding, the three zones of the joint have a higher impact toughness reserve and safety margin. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The welding groove structure of the present invention is shown in FIG. Figure 1 ;

[0027] Figure 2 The welding groove structure of the present invention is shown in FIG. Figure 2 ;

[0028] Figure 3 This is a dispersed precipitation particle diagram of the quenched and tempered high-strength steel plate 12MnNiVR of the present invention;

[0029] Figure 4 It is a dispersed composite precipitation particle diagram of the present invention;

[0030] Figure 5 The microstructure of the quenched and tempered high-strength steel plate 12MnNiVR of the present invention is Figure 1 ;

[0031] Figure 6 The microstructure of the quenched and tempered high-strength steel plate 12MnNiVR of the present invention is Figure 2 ;

[0032] Figure 7 The asymmetric X-groove weld microstructure of the present invention Figure 1 ;

[0033] Figure 8 The asymmetric X-groove weld microstructure of the present invention Figure 2 ;

[0034] Fig. 9 This is a microstructure diagram of the cladding metal cladding line and the coarse grain zone of the present invention, wherein the coarse grain zone is an intracrystalline acicular ferrite structure. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0036] The present invention discloses a gas-electric vertical welding method for tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all considered to be included in the present invention. The method and application of the present invention have been described through preferred embodiments, and relevant personnel can obviously modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0037] For general arc welding, the welding heat input calculation formula is:

[0038] E=ηUI / V(1)

[0039] Where E is heat input, U is voltage, I is current, V is welding speed, and η is thermal efficiency.

[0040] As a welding method, gas-electric vertical welding requires high current density, constant wire feeding and high arc voltage during welding. The melting rate is proportional to the speed of filling metal into the welding groove, which should be equal to the constant wire feeding speed. Therefore, after deduction, the calculation formula for welding heat input of gas-electric vertical welding can also be expressed as:

[0041] E=kiUS(2)

[0042] Where ki is the melting coefficient of welding wire and S is the cross-sectional area of ​​groove.

[0043] The chemical composition of the quenched and tempered high-strength steel plate 12MnNiVR for a large oil storage tank pressure vessel of the present invention is as follows by weight percentage: C: 0.08%-0.11%, Si: 0.20%-0.30%, Mn: 1.37%-1.53%, P: ≤0.015%, S: ≤0.0050%, Ni: 0.20%-0.50%, Mo: 0.10%-0.30%, V: 0.02%-0.06%, Ti: 0.01%-0.025%, Alt: 0.025%-0.035%, and the balance is Fe and inevitable impurities; when the high-strength steel 12MnNiVR is refined, a Ca-Mg-Ce alloy block is added after refining, so that the weight percentages of Ca, Mg and Ce in molten steel are all ≤0.0005%. After hot rolling, the quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels needs to be tempered: the steel plate at room temperature is heated to 900℃~920℃ with the furnace, and the insulation time is extended by 15min~30min on the basis of the steel billet being burned through, and then immersed in a water tank for quenching after being taken out of the furnace; the tempering heat treatment heating temperature is 620℃~650℃, and the furnace time is 3.3t+30min, where t is the thickness of the steel plate; after quenching and tempering heat treatment, the metallographic structure is a tempered sorbite structure. The properties of the steel plate are shown in Table 1.

[0044] Table 1 Mechanical properties of steel plate 12MnNiVR

[0045]

[0046] The development of high heat input energy gas-electric vertical welding is carried out for the typical size specifications and thicknesses of quenched and tempered high-strength steel plate 12MnNiVR: 21.5mm, 32mm, 40mm. The size of the welding test plate is 800mm (rolling direction) × 200mm (width) × 21.5 / 32 / 40mm (thickness); the gas-electric vertical welding (EGW) uses the DW-S60G welding wire with a diameter of Φ1.6mm from Kobelco of Japan, and the shielding gas is CO 2 The chemical composition and mechanical properties of the deposited metal are shown in Table 2 and Table 3.

[0047] Table 2 Chemical composition of deposited metal (Wt%)

[0048]

[0049] Table 3 Mechanical properties of deposited metal

[0050]

[0051] The welding conditions of gas-electrode vertical welding (EGW) are shown in Table 4. After the above-mentioned welding method is implemented, the welded joint is subjected to manual ultrasonic flaw detection and mechanical property testing. The ultrasonic flaw detection result is qualified at level I. The tensile test performance of the gas-electrode vertical welding joint of 21.5mm / 32mm / 40mm thick 12MnNiVR steel plate is shown in Table 5. The impact test performance of each part of the gas-electrode vertical welding joint of 21.5mm / 32mm / 40mm thick 12MnNiVR steel plate is shown in Table 6. The side bending test of the welded joint adopts the bending diameter D=4a (thickness) and the bending angle of 180°. The bending test results show that the test specimen is intact without any cracks or defects.

[0052] Table 4 Test plate welding conditions

[0053]

[0054] Table 5 Welded joint tensile test results

[0055]

[0056] Table 6 Welded joint impact test results

[0057]

[0058]

[0059] It can be seen that the welded joint obtained by the 12MnNiVR steel plate with a thickness of 1.5mm / 32mm / 40mm in Example 2 not only has excellent comprehensive mechanical properties, but also has no welding defects, and the welding process is stable and fast, which can meet the welding construction of metal structures with high performance requirements for welded joints. The above embodiments are only for illustrating the technical ideas of the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical ideas proposed by the present invention fall within the protection scope of the present invention.

Claims

1. A gas-electric vertical welding method for tempered high-strength steel plates for large oil storage tank pressure vessels, characterized in that: The steps include: 1) Before welding, when refining high-strength steel 12MnNiVR, Ca-Mg-Ce alloy blocks are added after refining so that the weight percentages of Ca, Mg and Ce in molten steel are all ≤0.0005%; 2) When preparing the welding test plate, a V-shaped groove with an angle of 22.5° to 34.5° is used for thickness below 25mm; an asymmetric X-shaped groove with an outer groove angle of 23° to 33° and an inner groove angle of 48° to 69° is used for thickness above 25mm; the outer groove depth t = 1 / 2a + 2mm to 4mm is set according to the thickness of the steel plate, where a is the thickness of the steel plate, and no blunt edge is left on the groove; 3) Pair the welding test plates, leaving a gap of 3mm to 6mm; 4) For the open surface of the V-shaped groove or the outer surface of the asymmetric X-shaped groove, perform gas-electric vertical welding on one side to form a side weld, and install a copper triangular water-cooling test block on the other side of the welding test plate for forced cooling; 5) Perform gas-electric vertical welding on the other side of the asymmetric X-shaped groove, i.e., the inner side, to form an inner back weld. A copper water-cooled test block with a notch is installed on the completed outer side weld for forced cooling. Complete the gas-electric vertical welding of the tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels.

2. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: The thickness of the quenched and tempered high-strength steel plate 12MnNiVR for the large oil storage tank pressure vessel is 20 mm to 40 mm.

3. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: The chemical composition of the quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels is as follows by weight percentage: C: 0.08%-0.11%, Si: 0.20%-0.30%, Mn: 1.37%-1.53%, P: ≤0.015%, S: ≤0.0050%, Ni: 0.20%-0.50%, Mo: 0.10%-0.30%, V: 0.02%-0.06%, Ti: 0.01%-0.025%, Alt: 0.025%-0.035%, and the balance is Fe and inevitable impurities; when the high-strength steel 12MnNiVR is refined, a Ca-Mg-Ce alloy block is added after refining, so that the weight percentages of Ca, Mg and Ce in the molten steel are all ≤0.0005%.

4. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 3, characterized in that: The quenched and tempered high-strength steel plate 12MnNiVR for large oil storage tank pressure vessels needs to be tempered after hot rolling: the steel plate at room temperature is heated to 900°C-920°C with the furnace temperature, and the insulation time is extended by 15min-30min on the basis of the steel billet being burned through, and after being taken out of the furnace, it is immersed in a water tank for quenching; the tempering heat treatment heating temperature is 620°C-650°C, and the furnace time is 3.3t+30min, wherein t is the thickness of the steel plate; after the quenching and tempering heat treatment, the metallographic structure obtained is a tempered troostite structure.

5. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: In the step 2), the roughness of the processed surface of the welding test plate groove is ≤ Ra20.

6. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: After the assembly in step 3) is completed, manual arc welding, CO2 gas shielded welding or hydrogen arc welding is used to perform tack welding on both ends and the middle position of the assembled welding test plate. The weld length of each tack weld is ≥15mm, the weld height is ≥4mm, and the interval length between adjacent tack welds does not exceed 300mm.

7. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: In the steps 4) and 5), the protective gas is carbon dioxide gas, the volume percentage of CO2 gas is ≥98%, and the gas flow rate is controlled to be 26L / min to 28L / min.

8. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: In the steps 4) and 5), the welding current is 360A to 420A, the welding voltage is 36V to 41V, and the welding speed is 5cm / min to 17cm / min.

9. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 1, characterized in that: The welding line energy of the gas-electric vertical welding in the steps 4) and 5) is ≥100KJ / cm; the welding test plates are paired, and a pairing gap is reserved for front gas-electric vertical welding to form a front weld, and a copper triangular water-cooling test block is installed on the back of the welding test plate for forced cooling; back gas-electric vertical welding is performed to form a back weld, and the completed front weld is installed with a copper water-cooling test block with a notch for forced cooling.

10. The gas-electrode vertical welding method for quenched and tempered high-strength steel plates for large oil storage tank pressure vessels according to claim 9, characterized in that: The welding joint Rm is ≥540MPa, the joint cold bending d=3a, 180° is qualified, the weld impact energy -20℃ KV2 is ≥57J, the fusion line impact energy -20℃ KV2 is ≥70J, and the heat affected zone -20℃ KV2 is ≥66J.

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