CN112894198A - Self-protection flux-cored wire for ultralow-temperature high-manganese steel - Google Patents
Self-protection flux-cored wire for ultralow-temperature high-manganese steel Download PDFInfo
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- CN112894198A CN112894198A CN202110075043.6A CN202110075043A CN112894198A CN 112894198 A CN112894198 A CN 112894198A CN 202110075043 A CN202110075043 A CN 202110075043A CN 112894198 A CN112894198 A CN 112894198A
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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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
- B23K35/3053—Fe as the principal constituent
- B23K35/3066—Fe as the principal constituent with Ni as next major constituent
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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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
- B23K35/3053—Fe as the principal constituent
- B23K35/3073—Fe as the principal constituent with Mn as next major constituent
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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
- B23K35/00—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting
- B23K35/22—Rods, electrodes, materials, or media, for use in soldering, welding, or cutting characterised by the composition or nature of the material
- B23K35/24—Selection of soldering or welding materials proper
- B23K35/30—Selection of soldering or welding materials proper with the principal constituent melting at less than 1550 degrees C
- B23K35/3053—Fe as the principal constituent
- B23K35/308—Fe as the principal constituent with Cr as next major constituent
- B23K35/3086—Fe as the principal constituent with Cr as next major constituent containing Ni or Mn
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Abstract
The invention relates to a self-protection flux-cored wire for ultralow-temperature high-manganese steel. The technical scheme is as follows: the self-protection flux-cored wire for the ultralow-temperature high-manganese steel consists of 65-70 wt% of steel strip and 30-35 wt% of flux-cored powder; the chemical components of the steel strip are as follows: 0.10-0.20 wt% of C, 0.01-0.05 wt% of Si, 3-7 wt% of Mn, 3-8 wt% of Ni, 3-8 wt% of Cr, less than or equal to 0.002 wt% of P, less than or equal to 0.001 wt% of S, and the balance of Fe and inevitable impurities; the chemical components of the medicine core powder are as follows: 38-42 wt% of barium fluoride, 4-7 wt% of marble, 5-8 wt% of aluminum powder, 2-6 wt% of high-carbon ferrochrome, 34-37 wt% of electrolytic manganese and the balance of Fe. The invention has low preparation cost and simple alloy component system, and can realize all-position welding; the formed weld metal has good forming and excellent low-temperature toughness, the mechanical property is matched with that of the ultralow-temperature high manganese steel, and the technical requirements of the strength and the ultralow-temperature toughness of the welded LNG storage tank at the working temperature of-196 ℃ can be met.
Description
Technical Field
The invention belongs to the technical field of self-protection flux-cored wires. In particular to a self-protection flux-cored wire for ultralow-temperature high manganese steel.
Background
Steel for storage and transportation containers such as Liquefied Natural Gas (LNG) is generally stored at a low temperature of-196 ℃, steel for commercial LNG storage tanks at present is 9Ni steel, and since steel sheet having a nickel content of 9% is expensive, high safety is required for steel for LNG storage and transportation key materials, and reduction in construction cost is also required, development of Ni-reduced steel sheet becomes an important development direction for Ni-based low temperature steel, and thus nickel-saving low temperature steel is developed at home and abroad in succession. In recent years, high manganese steels (having a Mn content of 24 to 26 wt%) have been drawing attention because of their low cost and excellent ductility and toughness in order to reduce the production cost of steels for LNG tanks and the dependence on high-priced nickel elements. Compared with the existing common nickel alloy, the ultralow-temperature high-manganese steel has better weldability, the cost price is only 70-80% of that of nickel alloy steel, and the ultralow-temperature high-manganese steel becomes a preferred material for replacing 9Ni steel and has a larger market prospect.
When manufacturing storage and transportation containers such as LNG, etc., ultra-low temperature high manganese steel, the manual arc welding is the main connection method adopted in China, which accounts for more than 90% of the total connection process, so the manual arc welding technology has received attention of technicians in this field. The patent application (201910008172.6) discloses a low-hydrogen type electrode for manual arc welding suitable for ultralow temperature high manganese steel. However, because the manual arc welding is completely operated manually, the welding production efficiency is low, the labor intensity is high, and the welding quality is controlled by the technique and the operation method of workers to a great extent. In addition, the welding rod is dried before use, and the working procedure and the production cost are increased.
In order to make up for the defects of the manual electric arc welding technology, a self-shielded flux-cored wire efficient welding method can be adopted. The self-protection flux-cored wire can realize all-position welding, is equivalent to an electric welding rod in the aspect of operation flexibility, more importantly, the welding production efficiency is 5-10 times that of the electric welding rod, in addition, extra protective gas and welding flux are not needed, and welding equipment is simple. However, no technology can realize the self-protection flux-cored wire matched with the ultralow-temperature high-manganese steel at present.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a preparation method of a self-shielded flux-cored wire for ultralow-temperature high-manganese steel, which has low cost and simple alloy component system; the weld metal formed by the self-protection flux-cored wire for the ultralow-temperature high-manganese steel has good forming property and excellent low-temperature toughness, and the mechanical property of the self-protection flux-cored wire is matched with that of the ultralow-temperature high-manganese steel; the welding method can be used for all-position welding, has high welding efficiency, and can meet the technical requirements of the strength and ultralow-temperature toughness of the welded LNG storage tank at the working temperature of-196 ℃.
In order to achieve the purpose, the invention adopts the technical scheme that: the self-protection flux-cored wire for the ultralow-temperature high-manganese steel consists of 65-70 wt% of steel strip and 30-35 wt% of flux-cored powder core.
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%; ni accounts for 3-8 wt%; 3-8 wt% of Cr; 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 weight percentage of barium fluoride is 38-42 wt%; 4-7 wt% of marble; 5-8 wt% of aluminum powder; 2-6 wt% of high-carbon ferrochrome; electrolytic manganese accounts for 34-37 wt%; the balance being Fe.
The preparation method of the self-protection flux-cored wire for the ultralow-temperature high-manganese steel comprises the following steps: rolling the steel strip into a U-shaped tube, and adding the medicine core powder into the U-shaped tube; then, performing joint closing, wire drawing and reducing, wire winding, surface treatment and layer winding to prepare the self-shielded flux-cored wire for the ultralow-temperature high-manganese steel.
The purity of the barium fluoride is more than or equal to 99 percent; the particle size of the barium fluoride is 0.15-0.20 mm.
The purity of the marble is more than or equal to 99 percent; the granularity of the marble is less than or equal to 0.3 mm.
The purity of the aluminum powder is more than or equal to 99 percent; the granularity of the aluminum powder is less than or equal to 0.30 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.
The purity of the electrolytic manganese is more than or equal to 99 percent; the granularity of the electrolytic manganese is less than or equal to 0.3 mm.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following positive effects:
the invention has the advantages of low price of the adopted alloy elements, simple alloy component system, low preparation cost and obvious economy. And, compared with the manual welding electrode, the welding production efficiency is improved by 5-10 times.
According to the self-protection flux-cored wire, a mode that a steel belt and a flux core are used for commonly transferring alloy elements is adopted, the Mn content of formed weld metal is 24-26 wt%, the Mn content is equivalent to that of a base metal, a component system basically identical to that of the base metal is guaranteed, when a welding joint is formed, the change of the structure and the performance near a fusion line formed by the diffusion of the Mn element is avoided, and the weld metal is guaranteed to have mechanical properties matched with the base metal.
The manganese element and the carbon element in the invention are austenite forming elements, and when the weld metal molten pool is solidified under the combined action, the austenite phase is taken as a solidification initial phase and is kept to the room temperature, so that the weld metal with a full austenite structure is formed. When the content of carbon in the welding seam is too low, the yield strength of the welding seam is not enough, and when the content of carbon 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, the high-manganese low-nickel alloy system is formed by replacing expensive nickel with manganese, so that the steel strip contains 0.10-0.20 wt% of C and 3-7 wt% of Mn, the flux core contains 2-6 wt% of high-carbon ferrochrome and 34-37 wt% of electrolytic manganese, an austenite structure is guaranteed, good ultralow-temperature toughness is obtained, and the cost is reduced.
The nickel element is an austenite forming element, the cost is increased when the content is too high, and the austenite stability of the welding seam is influenced when the content is too low. Therefore, the Ni content in the steel strip is 3-8 wt%, so that the steel strip not only ensures the all-austenite structure and obtains good ultralow-temperature toughness, but also ensures lower 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, and the welding seam is ensured to have lower hot crack sensitivity.
The chemical composition system of the steel strip contains Cr element, so that the steel strip has the effect of solid solution strengthening, when the Cr element is too high, the strength is improved, and meanwhile, the low-temperature toughness is reduced, and when the Cr element is too low, the solid solution strengthening effect cannot be realized, so that the Cr content in the steel strip is 3-8 wt%, and the strength of weld metal can be improved on the premise of ensuring good low-temperature toughness.
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 molten iron on the other hand. The Si content in the weld metal is too high, so that the low-temperature toughness can be reduced although the strength can be improved; the Si content in the weld metal is too low to play a role in adjusting the viscosity of molten iron, so that the Si content in the steel strip is 0.01-0.05 wt%, the strength is improved, the viscosity of the molten iron is well adjusted, and the all-position weldability of the self-protection flux-cored wire for ultralow-temperature high manganese steel is ensured.
The powder core comprises aluminum powder, high-carbon ferrochrome and electrolytic manganese in a component system, and the C content, the Mn content and the Al content in weld metal are ensured through chemical metallurgical reaction in a welding process so as to form a full-austenite structure. C. When the contents of the three components of Mn and Al are too low, a full austenite structure cannot be formed, and the strength and the low-temperature toughness are reduced; on the other hand, although the low-temperature toughness can be secured, the strength is lowered. Therefore, the aluminum powder content in the powder core is 5-8 wt%, the high-carbon ferrochrome content is 2-6 wt% and the electrolytic manganese content is 34-37 wt%, so that the weld metal structure is fully austenitic, the weld metal has excellent ultralow-temperature toughness and sufficient strength, the solidification temperature range is reduced, solidification cracks are avoided, and the generation of liquefaction cracks and reheating cracks is reduced or prevented.
The component system of the medicinal core powder contains barium fluoride and marble to adjust the fluidity of molten iron. When the content of barium fluoride and marble is too high, molten iron is thinner and the molding is not good; too low, the fluidity of the molten iron cannot be adjusted, and the molding is not good. Therefore, in the powder core, the content of barium fluoride is 38-42 wt%, and the content of marble is 4-7 wt%, so that the fluidity of molten iron can be adjusted, and weld metal can be welded at all positions, and a better weld forming effect is achieved.
The self-protection flux-cored wire prepared by the invention is used for self-protection 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 at-196 ℃ is highkv60-90J; also ensure thatStrength: the yield strength is 400-450 MPa, the tensile strength is 600-690 MPa, the elongation A is 36-43%, and the requirements of strength and ultralow-temperature toughness matched with ultralow-temperature high manganese steel are met.
Therefore, the invention has low preparation cost and simple alloy component system, can realize all-position welding and has high welding production efficiency; the formed weld metal has good forming and excellent low-temperature toughness, the mechanical property is matched with the ultralow-temperature high manganese steel, and the technical requirements on the strength and the ultralow-temperature toughness of the welded LNG storage tank suitable for the working temperature of 196 ℃ below zero can be met.
Detailed Description
The invention is further described with reference to specific embodiments, without limiting its scope.
A self-protection flux-cored wire for ultralow-temperature high-manganese steel. The self-protection flux-cored wire for the ultralow-temperature high-manganese steel in the specific embodiment is composed of 65-70 wt% of steel strip and 30-35 wt% of flux-cored powder core.
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%; ni accounts for 3-8 wt%; 3-8 wt% of Cr; 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 weight percentage of barium fluoride is 38-42 wt%; 4-7 wt% of marble; 5-8 wt% of aluminum powder; 2-6 wt% of high-carbon ferrochrome; electrolytic manganese accounts for 34-37 wt%; the balance being Fe.
The preparation method of the self-protection flux-cored wire for the ultralow-temperature high-manganese steel comprises the following steps: rolling the steel strip into a U-shaped tube, and adding the medicine core powder into the U-shaped tube; then, performing joint closing, wire drawing and reducing, wire winding, surface treatment and layer winding to prepare the self-shielded flux-cored wire for the ultralow-temperature high-manganese steel.
The ultralow-temperature high manganese steel comprises the following chemical components: 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, less than or equal to 0.005 wt% of P, and less than or equal to 0.003 wt% 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 35 percent; -196Impact energy A at DEG Ckv≥54J。
The purity of the barium fluoride is more than or equal to 99 percent.
The purity of the marble is more than or equal to 99 percent.
The purity of the aluminum powder is more than or equal to 99 percent.
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 purity of the electrolytic manganese is more than or equal to 99%.
The following technical parameters or features are the same in each example of the present embodiment:
the preparation method of the self-protection flux-cored wire for the ultralow-temperature high-manganese steel comprises the following steps: rolling the steel strip into a U-shaped tube, and adding the medicine core powder into the U-shaped tube; then, performing joint closing, wire drawing and reducing, wire winding, surface treatment and layer winding to prepare the self-protection flux-cored wire for the ultralow-temperature high-manganese steel;
the granularity of the barium fluoride is 0.15-0.20 mm;
the granularity of the marble is less than or equal to 0.3 mm;
the granularity of the aluminum powder is less than or equal to 0.30 mm;
the grain size of the high-carbon ferrochrome is less than or equal to 0.30 mm;
the granularity of the electrolytic manganese is less than or equal to 0.3 mm;
in the embodiment, the ultra-low temperature high manganese steel with the thickness of 20mm is welded by a self-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.
The detailed description is omitted in the embodiments.
Example 1
A self-protection flux-cored wire for ultralow-temperature high-manganese steel. The diameter of the self-protection flux-cored wire is phi 1.6 mm; the self-shielded flux-cored wire in the embodiment is composed of 65 wt% of steel strip and 35 wt% of flux-cored powder.
The chemical components of the steel strip are as follows: 0.10 wt% of C, 0.03 wt% of Si, 7 wt% of Mn, 0.002 wt% of P, 0.001 wt% of S, 3 wt% of Ni, 6 wt% of Cr, and the balance of Fe and inevitable impurities.
The chemical components of the medicine core powder are as follows: 42 wt% of barium fluoride, 7 wt% of marble, 8 wt% of aluminum powder, 6 wt% of high-carbon ferrochrome, 37 wt% of electrolytic manganese and the balance of Fe.
The purity of the barium fluoride is 99%.
The purity of the marble was 99%.
The purity of the aluminum powder is 99%.
The purity of the electrolytic manganese is 99%.
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: 0.40 wt% of C, 0.15 wt% of Si, 20 wt% of Mn, 0.03 wt% of N, 0.003 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 440MPa, the tensile strength is 680MPa, and the elongation A is 38%; impact energy A at-196 DEG CkvIs 72J.
In the embodiment, the ultra-low temperature high manganese steel with the thickness of 20mm is welded by a self-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. The welding current is 200-220A, the arc voltage is 20-22V, the welding speed is 20-22 cm/min, and the welding line energy is 15-17 kJ/cm.
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 450MPa, the tensile strength is 690MPa, the elongation A is 38 percent, and the average value A of the impact energy at the temperature of-196 DEG Ckv＝60J。
Example 2
A self-protection flux-cored wire for ultralow-temperature high-manganese steel. The procedure of example 1 was followed, except that:
the self-shielded flux-cored wire in the embodiment is composed 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 0.15 wt%; si is 0.01 wt%; mn is 5 wt%; p is 0.001 wt%; s is 0.001 wt%; ni is 6 wt%; 8 wt% of Cr; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: 41 wt% of barium fluoride, 6 wt% of marble, 6 wt% of aluminum powder, 5 wt% of high-carbon ferrochrome, 35 wt% of electrolytic manganese and the balance of Fe.
The purity of the barium fluoride is 99.1%.
The purity of the marble was 99.2%.
The purity of the aluminum powder is 99.2%.
The purity of the electrolytic manganese is 99.1%.
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, 0.10 wt% of Si, 28 wt% of Mn, 0.01 wt% of N, 0.003 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 450MPa, the tensile strength is 660MPa, and the elongation A is 40%; impact energy A at-196 DEG CkvIs 72J.
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 440MPa, 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＝75J。
Example 3
A self-protection flux-cored wire for ultralow-temperature high-manganese steel. The procedure of example 1 was followed, except that:
the self-shielded flux-cored wire in the embodiment is composed 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 0.20 wt%; si is 0.05 wt%; mn is 3 wt%; p is 0.001 wt%; s is 0.001 wt%; ni is 8 wt%; 3 wt% of Cr; the balance being Fe and unavoidable impurities.
The chemical components of the medicine core powder are as follows: the barium fluoride accounts for 38 wt%; 4 wt% of marble; 5 wt% of aluminum powder; 2 wt% of high-carbon ferrochromium; electrolytic manganese is 34 wt%; the balance being Fe.
The purity of the barium fluoride is 99.3%.
The purity of the marble was 99.4%.
The purity of the aluminum powder is 99%. 4.
The purity of the electrolytic manganese is 99.3%.
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: 0.45 wt% of C, 0.20 wt% of Si, 24 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 405MPa, the tensile strength is 680MPa, and the elongation A is 42%; 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 400MPa, the tensile strength is 635MPa, the elongation A is 43 percent, and the average value A of the impact energy at the temperature of-196 ℃ iskv＝90J。
Compared with the prior art, the specific implementation mode has the following positive effects:
the alloy elements adopted by the embodiment have low price, simple alloy component system, low preparation cost and obvious economy. And, compared with the manual welding electrode, the welding production efficiency is improved by 5-10 times.
According to the self-protection flux-cored wire, the mode that the steel strip and the flux core are used for commonly transferring alloy elements is adopted, the Mn content of formed weld metal is 24-26 wt%, the Mn content is equivalent to that of a base metal, a component system basically identical to that of the base metal is guaranteed, when a welding joint is formed, the change of the structure and the performance of the weld metal near a fusion line formed by the diffusion of the Mn element is avoided, and the weld metal is guaranteed to have the mechanical property matched with the base metal.
In the embodiment, the manganese element and the carbon element are both austenite forming elements, and when the weld metal molten pool is solidified under the combined action, the austenite phase is taken as a solidification initial phase and is kept to the room temperature, so that the weld metal with a full austenite structure is formed. When the content of carbon in the welding seam is too low, the yield strength of the welding seam is not enough, and when the content of carbon 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, the manganese replaces expensive nickel to form a high-manganese low-nickel alloy system, so that the steel strip contains 0.10-0.20 wt% of C and 3-7 wt% of Mn, the flux core contains 2-6 wt% of high-carbon ferrochrome and 34-37 wt% of electrolytic manganese, an austenite structure is guaranteed, good ultralow-temperature toughness is obtained, and the cost is reduced.
The nickel element is an austenite forming element, the cost is increased when the content is too high, and the austenite stability of the welding seam is influenced when the content is too low. Therefore, the Ni content in the steel strip of the embodiment is 3-8 wt%, so that not only is the fully austenitic structure ensured, and good ultralow-temperature toughness is obtained, but also lower element cost is ensured.
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, and the welding seam is ensured to have lower hot crack sensitivity.
The chemical composition system of the steel strip of the embodiment contains Cr element, which plays a role in solid solution strengthening, when the Cr element is too high, the strength is improved, and simultaneously, the low-temperature toughness is reduced, and when the Cr element is too low, the solid solution strengthening is not achieved, so that the Cr content in the steel strip of the embodiment is 3-8 wt%, and the strength of the weld metal can be improved on the premise of ensuring good low-temperature toughness.
The steel strip of the embodiment contains Si, which plays a role in solid solution strengthening on one hand and adjusting the viscosity of molten iron on the other hand. The Si content in the weld metal is too high, so that the low-temperature toughness can be reduced although the strength can be improved; the Si content in the weld metal is too low to play a role in adjusting the viscosity of the molten iron, so that the Si content in the steel strip in the embodiment is 0.01-0.05 wt%, the strength is improved, the viscosity of the molten iron is well adjusted, and the all-position weldability of the welding wire is ensured.
The component system of the powder core of the embodiment contains aluminum powder, high-carbon ferrochrome and electrolytic manganese, and the C content, the Mn content and the Al content in weld metal are ensured through chemical metallurgical reaction in the welding process so as to form a full-austenite structure. C. When the contents of the three components of Mn and Al are too low, a full austenite structure cannot be formed, and the strength and the low-temperature toughness are reduced; on the other hand, although the low-temperature toughness can be secured, the strength is lowered. Therefore, in the powder core of the embodiment, the content of the aluminum powder is 5-8 wt%, the content of the high-carbon ferrochrome is 2-6 wt% and the content of the electrolytic manganese is 34-37 wt%, so that the weld metal structure is fully austenitic, the weld metal has excellent ultralow-temperature toughness and sufficient strength, the solidification temperature range is reduced, solidification cracks are avoided, and the occurrence of liquefaction cracks and reheating cracks is reduced or prevented.
The ingredient system of the powder core of the embodiment contains barium fluoride and marble to adjust the fluidity of molten iron. When the content of barium fluoride and marble is too high, molten iron is thinner and the molding is not good; too low, the fluidity of the molten iron cannot be adjusted, and the molding is not good. Therefore, in the powder core of the embodiment, the content of barium fluoride is 38-42 wt%, and the content of marble is 4-7 wt%, so that the fluidity of molten iron can be adjusted, and the weld metal can be welded at all positions, and a better weld forming effect can be achieved.
The self-protection flux-cored wire prepared by the specific embodiment is used for self-protection 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 at-196 ℃ is highkv60-90J; sufficient strength is also ensured: the yield strength is 400-450 MPa, the tensile strength is 600-690 MPa, the elongation A is 36-43%, and the requirements of strength and ultralow-temperature toughness matched with ultralow-temperature high manganese steel are met.
Therefore, the specific embodiment has low preparation cost and simple alloy component system, can realize all-position welding, and has high welding production efficiency; the formed weld metal has good forming and excellent low-temperature toughness, the mechanical property is matched with the ultralow-temperature high manganese steel, and the technical requirements on the strength and the ultralow-temperature toughness of the welded LNG storage tank suitable for the working temperature of 196 ℃ below zero can be met.
Claims (6)
1. The utility model provides a self preservation protects flux cored wire for ultra-low temperature high manganese steel, a self preservation protects flux cored wire for ultra-low temperature high manganese steel comprises 65 ~ 70 wt% steel band and 30 ~ 35 wt% powder, its characterized in that:
the chemical components of the steel strip are as follows: 0.10-0.20 wt% of C, 0.01-0.05 wt% of Si, 3-7 wt% of Mn, 3-8 wt% of Ni, 3-8 wt% of Cr, less than or equal to 0.002 wt% of P, less than or equal to 0.001 wt% of S, and the balance of Fe and inevitable impurities;
the chemical components of the medicine core powder are as follows: 38-42 wt% of barium fluoride, 4-7 wt% of marble, 5-8 wt% of aluminum powder, 2-6 wt% of high-carbon ferrochrome, 34-37 wt% of electrolytic manganese and the balance of Fe;
the preparation method of the self-protection flux-cored wire for the ultralow-temperature high-manganese steel comprises the following steps: rolling the steel strip into a U-shaped tube, and adding the medicine core powder into the U-shaped tube; then, performing joint closing, wire drawing and reducing, wire winding, surface treatment and layer winding to prepare the self-shielded flux-cored wire for the ultralow-temperature high-manganese steel.
2. The self-shielded flux-cored wire for ultra-low temperature high manganese steel according to claim 1, wherein the purity of barium fluoride is not less than 99%, and the particle size of barium fluoride is 0.15-0.20 mm.
3. The self-shielded flux-cored wire for ultra-low temperature high manganese steel according to claim 1, wherein the purity of the marble is not less than 99%, and the grain size of the marble is not more than 0.3 mm.
4. The self-shielded flux-cored wire for ultra-low temperature high manganese steel of claim 1, wherein the purity of the aluminum powder is not less than 99%, and the particle size of the aluminum powder is not more than 0.30 mm.
5. The self-shielded flux-cored welding wire for ultra-low temperature high manganese steel of claim 1, wherein the chemical composition of the high carbon ferrochrome is: 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.
6. The self-shielded flux-cored wire for ultra-low temperature high manganese steel of claim 1, wherein the purity of the electrolytic manganese is not less than 99%, and the particle size of the electrolytic manganese is not more than 0.3 mm.
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