Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a consumable electrode gas shielded welding flux-cored wire which can be used for all-position welding and has high welding efficiency and is used for ultralow-temperature high-manganese steel; when the protection of the Ar-rich mixed gas is adopted, the weld metal formed under the protection of gas-slag combination has good forming, low air hole sensitivity and excellent low-temperature toughness, the strength is matched with the ultralow-temperature high manganese steel, and the technical requirements on the strength and ultralow-temperature toughness of the welded LNG storage tank suitable for the working temperature of 196 ℃ below zero can be met.
In order to achieve the purpose, the invention adopts the technical scheme that: the gas metal arc welding flux-cored wire for the ultralow-temperature high-manganese steel is composed of 65-70 wt% of steel strips and 30-35 wt% of flux-cored powder.
The chemical components of the steel strip are as follows: c is 0.10-0.20 wt%; si is 0.01-0.05 wt%; mn is 3-7 wt%; p is less than or equal to 0.002 wt%; s is less than or equal to 0.001 wt%; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: the rutile accounts for 28-34 wt%; 2-4 wt% of zircon sand; 2-4 wt% of potassium titanate; the electrolytic manganese accounts for 20-25 wt%; 8-15 wt% of nickel powder; 8-12 wt% of high-carbon ferrochrome; the balance being iron powder.
The preparation method of the gas metal arc welding flux-cored wire for the ultralow-temperature high-manganese steel comprises the following steps: and rolling the steel strip into a U-shaped tube, adding the flux-cored powder into the U-shaped tube, then performing joint closing, wire drawing and reducing, wire winding, surface treatment and layer winding to prepare the consumable electrode gas shielded welding flux-cored wire for the ultralow-temperature high manganese steel.
The purity of the rutile is more than or equal to 99 percent, and the granularity of the rutile is less than or equal to 0.3 mm.
The purity of the zircon sand is more than or equal to 99 percent, and the granularity of the zircon sand is less than or equal to 0.3 mm.
The purity of the potassium titanate is more than or equal to 99 percent, and the granularity of the potassium titanate is less than or equal to 0.3 mm.
The purity of the electrolytic manganese is more than or equal to 99 percent, and the granularity of the electrolytic manganese is less than or equal to 0.3 mm.
The purity of the nickel powder is more than or equal to 99 percent, and the granularity of the nickel powder is less than or equal to 0.3 mm.
The high-carbon ferrochrome comprises the following chemical components: 84-86 wt% of Cr, 10-12 wt% of C and the balance of iron and inevitable impurities; the grain size of the high-carbon ferrochrome is less than or equal to 0.30 mm.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following positive effects:
the component system of the powder of the medicine core adopted by the invention contains rutile and zircon sand, and has the function of adjusting the melting point and viscosity of the slag. When the composite addition amount of the two is small, the adjusting effect is not obvious; when the addition amount is high, weld metal formability is rather deteriorated. Therefore, the content of rutile in the powder core is 28-34 wt%, the content of zircon sand is 2-4 wt%, the welding efficiency is improved, on the one hand, the fluidity of liquid metal is enhanced, the formability of weld metal is improved, and all-position welding is realized; on the other hand, a layer of thin covering slag is formed in the welding process, the air hole sensitivity of the welding seam metal is reduced, and the quality of the welding seam metal is ensured.
The powder of the medicine core adopted by the invention contains potassium titanate, which mainly plays a role in stabilizing electric arcs. The content of potassium titanate in the powder core is 2-4 wt%, so that good arc stability is ensured; further, the formability of the weld metal is ensured during all-position welding, and the welding process performance is improved.
According to the invention, the mode of common transition of alloy elements by using the steel strip and the powder is adopted, the Mn content of the formed weld metal is 24-26 wt%, and is equivalent to that of the parent metal, so that the component system basically identical to that of the parent metal is ensured. When a welding joint is formed, the change of the structure and the performance near a fusion line formed by the diffusion of a manganese element is avoided, and the ultralow-temperature mechanical property of the welding line metal is ensured.
The manganese element and the carbon element in the invention are austenite forming elements, and the two elements act together to ensure that when a weld metal molten pool is solidified, an austenite phase is taken as a solidification initial phase and is kept to room temperature, so that the weld metal with a full austenite structure is formed. When the carbon element content in the welding seam is too low, the yield strength of the welding seam is not enough; when the content of the carbon element is too high, coarse carbides are generated in the welding seam to influence the toughness. When the manganese content is too low, a single austenite structure is not formed sufficiently; when the manganese content is too high, the tensile strength is lowered. Meanwhile, in the invention, the steel strip contains 0.10-0.20 wt% of C and 3-7 wt% of Mn, the flux core contains 8-12 wt% of high-carbon ferrochrome and 20-25 wt% of electrolytic manganese, thereby ensuring austenite structure and obtaining good ultralow-temperature toughness. The nickel element is an austenite forming element, and the cost is increased due to the excessively high content of the nickel element; too low a content may affect the austenitic stability of the weld. Therefore, the Ni content in the drug core powder is 8-15 wt%, and the full austenite structure is ensured and the good ultralow-temperature toughness is obtained on the premise of ensuring the low element cost.
In the invention, the existence of impurity elements of sulfur and phosphorus enables weld metal to generate liquefaction cracks and reheating cracks, so the content of the sulfur and phosphorus elements is strictly controlled as follows: p is less than or equal to 0.002 wt% and S is less than or equal to 0.001 wt%. By purifying the molten steel, the P and S contents of the welding wire are reduced to the minimum, the hot cracking tendency caused by P, S segregation is avoided, and the good weld metal quality is ensured.
The steel strip contains Si element, so that the steel strip plays a role in solid solution strengthening on one hand and plays a role in adjusting the viscosity of liquid metal in a molten pool on the other hand. The Si content in the weld metal is too high, so that the strength is improved, but the ultralow-temperature toughness is reduced; the Si content in the weld metal is too low, so that the function of adjusting the viscosity of the liquid metal in a molten pool cannot be realized. Therefore, the Si content in the steel strip is 0.01-0.05 wt%, the strength of the weld metal is guaranteed, the viscosity of the liquid metal is well adjusted, and the formability of the weld metal during all-position welding is improved.
The gas metal arc welding flux-cored wire for the ultra-low temperature high manganese steel prepared by the invention is used for gas metal arc welding of the ultra-low temperature high manganese steel, and weld metal forms a full austenite structure, so that excellent ultra-low temperature toughness is ensured, and the impact energy A at-196 ℃ is highkv70-110J; sufficient strength is also ensured: the yield strength is 400-480 MPa, the tensile strength is 600-720 MPa, the elongation A is 38-41%, and the strength requirement and the ultra-low temperature toughness requirement of the ultra-low temperature high manganese steel at the working temperature of-196 ℃ are met.
Therefore, the technology of the invention can form a layer of thin covering slag in the welding process, and when the protection of the Ar-rich mixed gas is adopted, the formed welding seam metal has good forming and lower air hole sensitivity under the combined protection of the gas and the slag, can be used for all-position welding, and has high welding efficiency; the formed weld metal has the characteristics of ultralow temperature and high toughness, the strength is matched with the ultralow temperature high manganese steel, and the welded joint has the mechanical properties of high strength and excellent ultralow temperature toughness and can meet the technical requirements on the strength and ultralow temperature toughness of the welded LNG storage tank applicable to the working temperature of-196 ℃.
Detailed Description
The invention is further described with reference to specific embodiments, without limiting its scope.
A flux-cored wire for gas metal arc welding of ultralow temperature high manganese steel. The gas metal arc welding flux-cored wire for the ultralow-temperature high-manganese steel comprises 65-wt 70% of steel strip and 30-35 wt% of flux-cored powder.
The chemical components of the steel strip are as follows: c is 0.10-0.20 wt%; si is 0.01-0.05 wt%; mn is 3-7 wt%; p is less than or equal to 0.002 wt%; s is less than or equal to 0.001 wt%; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: the rutile accounts for 28-34 wt%; 2-4 wt% of zircon sand; 2-4 wt% of potassium titanate; the electrolytic manganese accounts for 20-25 wt%; 8-15 wt% of nickel powder; 8-12 wt% of high-carbon ferrochrome; the balance being iron powder.
The purity of the rutile is more than or equal to 99 percent.
The purity of the zircon sand is more than or equal to 99 percent.
The purity of the potassium titanate is more than or equal to 99 percent.
The purity of the electrolytic manganese is more than or equal to 99%.
The purity of the nickel powder is more than or equal to 99%.
The high-carbon ferrochrome comprises the following chemical components: 84-86 wt% of Cr, 10-12 wt% of C and the balance of iron and inevitable impurities.
The chemical components of the ultralow-temperature high-manganese steel in the specific embodiment are as follows: 0.40 to 0.50 wt% of C, 0.10 to 0.20 wt% of Si, 20 to 28 wt% of Mn, 0.01 to 0.08 wt% of N, 0.005 wt% or less of P, and 0.003 wt% or less of S. The mechanical properties of the 25Mn ultralow-temperature steel are as follows: the yield strength is more than or equal to 400MPa, the tensile strength is more than or equal to 660MPa, and the elongation A is more than or equal to 40 percent; impact energy A at-196 DEG Ckv≥54J。
The following technical parameters or features are the same in each example of the present embodiment:
the preparation method of the gas metal arc welding flux-cored wire for the ultralow-temperature high-manganese steel comprises the following steps: and rolling the steel strip into a U-shaped tube, adding the flux-cored powder into the U-shaped tube, then performing joint closing, wire drawing and reducing, wire winding, surface treatment and layer winding to prepare the consumable electrode gas shielded welding flux-cored wire for the ultralow-temperature high manganese steel.
The particle size of the rutile is less than or equal to 0.3 mm;
the granularity of the zircon sand is less than or equal to 0.3 mm;
the granularity of the potassium titanate is less than or equal to 0.3 mm;
the granularity of the electrolytic manganese is less than or equal to 0.3 mm;
the particle size of the nickel powder is less than or equal to 0.3 mm;
the grain size of the high-carbon ferrochrome is less than or equal to 0.30 mm.
The diameter of the gas metal arc welding flux-cored wire is phi 1.2 mm; welding ultra-low temperature high manganese steel with the thickness of 20mm by adopting a consumable electrode gas shielded welding method; the groove type of the test plate of the ultra-low temperature high manganese steel is X-shaped, and the angle of a single-side groove is 30 degrees.
When the specific embodiment is used for welding: adopting Ar-rich mixed gas for protection, wherein the proportion of the Ar-rich mixed gas is 80 vol% of argon and 20 vol% of CO2The flow rate of the Ar-rich mixed gas is 16-18L/min; the welding current is 230-240A, the arc voltage is 28-30V, the welding speed is 24-26 cm/min, and the welding line energy is 16-18 kJ/cm.
The detailed description is omitted in the embodiments.
Example 1
A flux-cored wire for gas metal arc welding of ultralow temperature high manganese steel. The gas metal arc welding flux-cored wire for ultralow-temperature high-manganese steel in the embodiment of the invention consists of 65 wt% of steel strip and 35 wt% of flux-cored powder.
The chemical components of the steel strip are as follows: c is 0.20 wt%; si is 0.05 wt%; mn is 7 wt%; p is 0.002 wt%; s is 0.001 wt%; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: rutile was 34 wt%; 4 wt% of zircon sand; 4 wt% of potassium titanate; electrolytic manganese is 25 wt%; 15 wt% of nickel powder; 12 wt% of high-carbon ferrochrome; the balance being iron powder.
The rutile has a purity of 99.4%.
The purity of the zircon sand is 99.5 percent.
The purity of the potassium titanate was 99.5%.
The purity of the electrolytic manganese is 99.5%.
The purity of the nickel powder is 99.4%.
The high-carbon ferrochrome comprises the following chemical components: 84 wt% of Cr, 12 wt% of C, and the balance of iron and inevitable impurities.
The ultralow-temperature high manganese steel comprises the following chemical components: 0.45 wt% of C, 0.10 wt% of Si, 28 wt% of Mn, 0.05 wt% of N, 0.004 wt% of P and 0.003 wt% of S. The mechanical properties of the 25Mn ultralow-temperature steel are as follows: the yield strength is 475MPa, the tensile strength is 710MPa, and the elongation A is 41 percent; impact energy A at-196 DEG CkvIs 75J.
The welded weld metal microstructure and mechanical properties of the embodiment are detected and analyzed: the weld metal is a fully austenitic structure; no solidification crack and reheating crack are generated; the yield strength of the weld metal is 480MPa, the tensile strength is 720MPa, the elongation A is 38 percent, and the average value A of the impact energy at the temperature of-196 DEG Ckv=72J。
Example 2
A flux-cored wire for gas metal arc welding of ultralow temperature high manganese steel. The gas metal arc welding flux-cored wire for ultralow-temperature high-manganese steel in the embodiment of the invention consists of 70 wt% of steel strip and 30 wt% of flux-cored powder.
The chemical components of the steel strip are as follows: c is 0.16 wt%; si is 0.03 wt%; mn is 4 wt%; p is 0.002 wt%; s is 0.001 wt%; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: rutile is 32 wt%; zircon sand 3 wt%; 3 wt% of potassium titanate; electrolytic manganese 23 wt%; 11 wt% of nickel powder; 10 wt% of high-carbon ferrochrome; the balance being iron powder.
The rutile has a purity of 99.2%.
The purity of the zircon sand is 99.2%.
The purity of the potassium titanate was 99.3%.
The purity of the electrolytic manganese is 99.4%.
The purity of the nickel powder is 99.2%.
The high-carbon ferrochrome comprises the following chemical components: 85 wt% of Cr, 11 wt% of C, and the balance of iron and inevitable impurities.
The ultralow-temperature high manganese steel comprises the following chemical components: 0.50 wt% of C, 0.20 wt% of Si, 26 wt% of Mn, 0.08 wt% of N, 0.004 wt% of P and 0.002 wt% of S. The mechanical properties of the 25Mn ultralow-temperature steel are as follows: the yield strength is 450MPa, the tensile strength is 675MPa, and the elongation A is 40 percent; impact energy A at-196 DEG CkvIs 102J.
The welded weld metal microstructure and mechanical properties of the embodiment are detected and analyzed: the weld metal is a fully austenitic structure; no solidification crack and reheating crack are generated; the yield strength of the weld metal is 460MPa, the tensile strength is 675MPa, the elongation A is 40 percent, and the average value A of the impact energy at the temperature of-196 DEG Ckv=90J。
Example 3
A flux-cored wire for gas metal arc welding of ultralow temperature high manganese steel. The gas metal arc welding flux-cored wire for ultralow-temperature high-manganese steel in the embodiment of the invention consists of 68 wt% of steel strip and 32 wt% of flux-cored powder.
The chemical components of the steel strip are as follows: c is 0.10 wt%; si is 0.01 wt%; mn is 3 wt%; p is 0.002 wt%; s is 0.001 wt%; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: rutile is 28 wt%; 2 wt% of zircon sand; 2 wt% of potassium titanate; electrolytic manganese accounts for 20 wt%; 8 wt% of nickel powder; 8 wt% of high-carbon ferrochrome; the balance being iron powder.
The rutile has a purity of 99.0%.
The purity of the zircon sand is 99.0%.
The purity of the potassium titanate was 99.1%.
The purity of the electrolytic manganese is 99.0%.
The purity of the nickel powder is 99.0%.
The high-carbon ferrochrome comprises the following chemical components: 86 wt% of Cr, 10 wt% of C, and the balance of iron and inevitable impurities.
The ultralow-temperature high manganese steel comprises the following chemical components: 0.40 wt% of C, 0.15 wt% of Si, 20 wt% of Mn, 0.01 wt% of N, 0.003 wt% of P and 0.002 wt% of S. The above-mentionedThe mechanical properties of the 25Mn ultralow-temperature steel are as follows: the yield strength is 445MPa, the tensile strength is 610MPa, and the elongation A is 42 percent; impact energy A at-196 DEG CkvIs 125J.
The welded weld metal microstructure and mechanical properties of the embodiment are detected and analyzed: the weld metal is a fully austenitic structure; no solidification crack and reheating crack are generated; the yield strength of the weld metal is 420MPa, the tensile strength is 620MPa, the elongation A is 41 percent, and the average value A of the impact energy at the temperature of-196 DEG Ckv=110J。
Compared with the prior art, the specific implementation mode has the following positive effects:
the component system of the powder core adopted by the embodiment contains rutile and zircon sand, and has the function of adjusting the melting point and viscosity of the slag. When the composite addition amount of the two is small, the adjusting effect is not obvious; when the addition amount is high, weld metal formability is rather deteriorated. Therefore, the content of rutile in the powder core of the embodiment is 28-34 wt%, and the content of zircon sand is 2-4 wt%, so that the welding efficiency is improved, on one hand, the fluidity of liquid metal is enhanced, the formability of weld metal is improved, and all-position welding is realized; on the other hand, a layer of thin covering slag is formed in the welding process, the air hole sensitivity of the welding seam metal is reduced, and the quality of the welding seam metal is ensured.
The core powder used in this embodiment contains potassium titanate, which mainly serves to stabilize the arc. The content of potassium titanate in the powder core of the specific embodiment is 2-4 wt%, so that good arc stability is ensured; further, the formability of the weld metal is ensured during all-position welding, and the welding process performance is improved.
In the embodiment, the mode that the steel strip and the powder are jointly used for transition of alloy elements is adopted, the Mn content of the formed weld metal is 24-26 wt%, and is equivalent to that of the base metal, so that the basically same component system as the base metal is ensured. When a welding joint is formed, the change of the structure and the performance near a fusion line formed by the diffusion of a manganese element is avoided, and the ultralow-temperature mechanical property of the welding line metal is ensured.
In the embodiment, the manganese element and the carbon element are both austenite forming elements, and the two elements act together to enable the austenite phase to be a solidification initial phase and to be kept to room temperature when the weld metal molten pool is solidified, so that the weld metal with a full austenite structure is formed. When the carbon element content in the welding seam is too low, the yield strength of the welding seam is not enough; when the content of the carbon element is too high, coarse carbides are generated in the welding seam to influence the toughness. When the manganese content is too low, a single austenite structure is not formed sufficiently; when the manganese content is too high, the tensile strength is lowered. Meanwhile, in the specific embodiment, the steel strip contains 0.10-0.20 wt% of C and 3-7 wt% of Mn, the flux core contains 8-12 wt% of high-carbon ferrochrome and 20-25 wt% of electrolytic manganese, an austenite structure is guaranteed, and good ultralow-temperature toughness is obtained. The nickel element is an austenite forming element, and the cost is increased due to the excessively high content of the nickel element; too low a content may affect the austenitic stability of the weld. Therefore, the Ni content in the powder core of the embodiment is 8-15 wt%, and the full austenite structure is ensured and the good ultralow-temperature toughness is obtained under the precondition of ensuring lower element cost.
In the embodiment, the existence of the impurity elements of sulfur and phosphorus enables the weld metal to generate a liquefaction crack and a reheating crack, so the embodiment strictly controls the contents of the sulfur and phosphorus elements: p is less than or equal to 0.002 wt% and S is less than or equal to 0.001 wt%. By purifying the molten steel, the P and S contents of the welding wire are reduced to the minimum, the hot cracking tendency caused by P, S segregation is avoided, and the good weld metal quality is ensured.
The steel strip of the embodiment contains Si element, so that the steel strip plays a role in solid solution strengthening on one hand and plays a role in adjusting the viscosity of liquid metal in a molten pool on the other hand. The Si content in the weld metal is too high, so that the strength is improved, but the ultralow-temperature toughness is reduced; the Si content in the weld metal is too low, so that the function of adjusting the viscosity of the liquid metal in a molten pool cannot be realized. Therefore, the content of Si in the steel strip is 0.01-0.05 wt%, the strength of the weld metal is ensured, the viscosity of the liquid metal is well adjusted, and the formability of the weld metal during all-position welding is improved.
The high manganese steel prepared by the embodiment for ultralow temperatureThe gas metal arc welding flux-cored wire is used for gas metal arc welding of ultralow-temperature high manganese steel, and weld metal forms a full austenite structure, so that excellent ultralow-temperature toughness is ensured, and the impact energy A is low at the temperature of-196 DEG Ckv70-110J; sufficient strength is also ensured: the yield strength is 400-480 MPa, the tensile strength is 600-720 MPa, the elongation A is 38-41%, and the mechanical property requirement and the ultra-low temperature toughness requirement of the ultra-low temperature high manganese steel at the working temperature of-196 ℃ are met.
Therefore, a layer of thin covering slag can be formed in the welding process by the technology of the specific embodiment, and when the protection of Ar-rich gas is adopted, the formed weld metal has good forming and low air hole sensitivity under the protection of gas-slag combination, can be used for all-position welding, and has high welding efficiency; the formed weld metal has the characteristics of ultralow temperature and high toughness, the strength is matched with the ultralow temperature high manganese steel, and the welded joint has the mechanical properties of high strength and excellent ultralow temperature toughness and can meet the technical requirements on the strength and ultralow temperature toughness of the welded LNG storage tank applicable to the working temperature of-196 ℃.