High-strength extremely-low-temperature welding material wire rod and manufacturing method and application thereof

Abstract

The invention relates to the technical field of ferrous metallurgy, in particular to a high-strength extremely-low-temperature welding material wire rod and a manufacturing method and application thereof.The manufacturing method comprises the steps that molten steel smelting is conducted according to chemical components and percentages of the high-strength extremely-low-temperature welding material wire rod, a square billet is manufactured in a forging and rolling mode after die casting, the square billet is heated and subjected to heat preservation for 4.5-6 h, and then the square billet is rolled into a first-diameter wire rod; cooling after rolling, uncoiling a wire rod, reducing the diameter from a first diameter to a second diameter through three times of drawing, annealing, reducing the diameter from the second diameter to a third diameter through three times of drawing after annealing, and finally performing finish drawing to a fourth diameter. The high-manganese steel liquid hydrogen storage tank welding material can be used for producing the high-manganese steel liquid hydrogen storage tank welding material, is matched with high-manganese steel welding and is good in forming, the content of Mn in formed weld metal is 24-28 wt%, the situation that due to large-range diffusion of the manganese element, the structure and performance near a fusion line are greatly different is avoided, and the extremely-low-temperature service mechanical performance of the weld metal is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of steel metallurgy, in particular to a high-strength ultra-low-temperature welding material wire rod and a manufacturing method and application thereof. BACKGROUND

[0002] Global energy shortage and environmental problems are increasingly prominent, and the development and utilization of low-carbon, clean and renewable energy is imminent. Hydrogen energy is considered as the most potential energy in the 21st century due to its wide source, high heat value, zero carbon emission and renewable characteristics. Liquid hydrogen storage has the greatest development potential due to its advantages of high hydrogen storage density, high filling efficiency and good safety, and the industrialization application of low-temperature liquid hydrogen storage and transportation needs to be promoted.

[0003] Safe storage and transportation of hydrogen is a key link of national energy strategy, and liquid hydrogen storage tank is the core equipment for storage and transportation. Stainless steel liquid hydrogen storage tank materials have been developed in China, and the welding materials used are also stainless steel welding materials. The comprehensive cost is relatively high, and the strength is too low, which limits the use.

[0004] Mn25 low-temperature high-manganese steel realizes low-temperature service by obtaining stable austenite structure with cheap C and Mn elements, and has great development potential in the field of liquid hydrogen. The existing matching welding material is still immature, and there is still no related technology for welding material under liquid hydrogen conditions. SUMMARY

[0005] The present application overcomes the shortcomings of the prior art and provides a high-strength ultra-low-temperature welding material wire rod and a manufacturing method and application thereof, which can be used for the production of high-manganese steel liquid hydrogen storage tank welding materials, and can be matched with high-manganese steel welding to form a good shape. The Mn content in the weld metal is 24-28wt%, which avoids large-scale diffusion of manganese elements, resulting in too large difference in microstructure and performance near the fusion line, and ensures the mechanical properties of the weld metal under ultra-low-temperature service.

[0006] In a first aspect, the present application provides a manufacturing method of a high-strength ultra-low-temperature welding material wire rod, comprising the following steps:

[0007] Smelting: smelting molten steel according to the chemical composition and percentage of the high-strength ultra-low-temperature welding material wire rod;

[0008] Making wire rod by rolling: making a bloom by die casting and forging rolling, heating and holding the bloom for 4.5-6 hours, then rolling into a first diameter wire rod, which can ensure the temperature homogenization of the bloom, avoid rolling defects caused by too large temperature difference at different positions in the subsequent heating and rolling process, and cooling after rolling;

[0009] Drawing: unwinding the wire rod, then reducing the diameter from the first diameter to the second diameter by three drawing processes, then annealing, then reducing the diameter from the second diameter to the third diameter by three drawing processes again, and finally fine drawing to the fourth diameter.

[0010] Further, the billet is pretreated before heating and holding, specifically including surface grinding with a depth of not less than 7 mm and chamfering treatment, and surface coating of ZS-1021 high-temperature resistant and oxidation-resistant paint.

[0011] Further, in the process of rolling the billet into a wire rod, the billet is sent into a wire rod rolling unit after heating and holding, and is rolled into a first diameter wire rod at a temperature in a range of 1010-1030℃, which is a temperature interval in which the composition has the best plasticity, so that the rolling resistance can be greatly reduced and the rolling efficiency can be increased.

[0012] Further, the post-rolling cooling includes strong air cooling, which effectively inhibits the precipitation of carbides and ensures the stability of subsequent drawing.

[0013] Further, in the drawing step, the surface oxide is removed by sand belt grinding after unwinding of the wire rod.

[0014] Further, in the drawing step, the annealing process is 780℃ holding for 4 hours and furnace cooling.

[0015] Further, the first diameter is Φ6.5 mm, the second diameter is Φ4.0 mm, the third diameter is Φ2.5 mm, and the fourth diameter is Φ2.4 mm.

[0016] Further, the chemical components and percentages of the high-strength and extremely low-temperature welding material wire rod include: C is 0.28-0.62wt%, Si is 0.01-0.03wt%, Mn is 25.8-30.5wt%, Cr is 1.15-6.23wt%, Ni is 10.5-15.5wt%, Mo is 2.2-3.8wt%, N is 0.15-0.35wt%, Cu≤0.15wt%, Ti≤0.012wt%, V≤0.02wt%, P≤0.002wt%, S≤0.002wt%, and the balance is Fe and inevitable impurities. The present application adopts high-C design, which meets the high-strength requirement while reducing the addition of other alloys and reduces the cost. The Mn element and the C element jointly act to promote the stability of austenite, so that the austenite phase is the initial solidification phase when the weld metal pool solidifies, and is maintained until room temperature, forming a full-austenite structure weld metal. At the same time, the wire rod contains a high content of Ni element, which ensures the austenite structure and obtains good extremely low-temperature strength and toughness, and a too high content of Ni element will increase the cost, and a too low content of Ni element will affect the stability of the austenite structure of the weld. The content of S and P elements is controlled to be P≤0.002wt% and S≤0.002wt%, so as to avoid the occurrence of liquation cracks and reheat cracks in the weld metal.

[0017] In a second aspect, the present application also provides a high-strength and extremely low-temperature welding material wire rod, which is obtained by using the manufacturing method in any one of the first aspect.

[0018] In a third aspect, the application provides the high-strength and extremely low-temperature welding material wire rod of the second aspect as a liquid hydrogen storage tank welding material, the liquid hydrogen storage tank welding material surface is not plated with copper, and is welded by using a welding agent for protection, and the Mn content in the weld metal formed is 24-28 wt%. The Mn content in the weld metal formed by the welding material of the wire rod is 24-28 wt%, which is equivalent to the Mn content of the base material, and during the welding process, the large-scale diffusion of the Mn element is avoided to cause too large differences in the structure and performance near the fusion line, and the mechanical properties of the weld metal at extremely low temperature are ensured.

[0019] The application has the following beneficial effects:

[0020] (1) The high-strength and extremely low-temperature welding material wire rod, the manufacturing method and the application thereof can be used for the production of high-manganese steel liquid hydrogen storage tank welding materials, and can be matched with high-manganese steel welding, and the forming is good, the Mn content in the weld metal formed is 24-28 wt%, the large-scale diffusion of the Mn element is avoided to cause too large differences in the structure and performance near the fusion line, the mechanical properties of the weld metal at extremely low temperature are ensured, and the extremely low-temperature service requirements are met.

[0021] (2) The Mn element and the C element jointly act to promote the stability of the austenite, the austenite phase is used as the initial phase during the solidification of the weld metal melt pool, and is kept until room temperature, and the weld metal with full austenite structure is formed; meanwhile, the wire rod contains a high Ni element, the austenite structure is ensured, and good strength and toughness at extremely low temperature are obtained.

[0022] (3) The manufacturing method of the application places the square billet in a heating furnace for 6 hours at 980 DEG C, and then sends the square billet into a wire rod rolling mill unit, which can ensure the temperature homogenization of the square billet, and can avoid the rolling defects caused by too large temperature differences at different positions during the subsequent heating and rolling; the square billet is rolled into a Φ6.5 mm wire rod at a temperature of 1010-1030 DEG C, which is the best temperature interval for the plasticity of the composition, and after rolling, strong air cooling is performed, which effectively inhibits the precipitation of carbides, and ensures the stability of subsequent drawing. DETAILED DESCRIPTION

[0023] The following examples are only illustrative of the application, and are not limited to the embodiments of the application.

[0024] Example 1

[0025] The chemical components of the high-strength and extremely low-temperature welding material wire rod are as follows: the C content is 0.28 wt%, the Si content is 0.02 wt%, the Mn content is 30.5 wt%, the Cr content is 4.35 wt%, the Ni content is 13.5 wt%, the Mo content is 2.9 wt%, the N content is 0.35 wt%, the Cu content is ≤0.15 wt%, the Ti content is ≤0.012 wt%, the V content is ≤0.02 wt%, the P content is ≤0.002 wt%, the S content is ≤0.002 wt%, and the balance is Fe and unavoidable impurities.

[0026] The steel is smelted with the above chemical composition, and then is made into 150mm square billets by die casting and subsequent forging and rolling. The square billets need to be surface ground with a depth of not less than 7mm and be chamfered. After surface grinding, the square billets are uniformly coated with ZS-1021 high-temperature oxidation-resistant paint, and then are placed in a heating furnace at 980°C for 4.5 hours, and then are sent to a wire rod rolling unit to be rolled into Φ6.5mm wire rods at a temperature of 1010-1030°C. The wire rods are prepared by strong air cooling after rolling.

[0027] The wire rods are drawn by uncoiling and mechanical drawing, and the surface oxide is removed by sand belt grinding. Then, the wire rods are reduced in diameter from Φ6.5mm to Φ4.0mm by three drawing processes, and then are annealed at 780°C for 4 hours and cooled in a furnace. After annealing, the wire rods are reduced in diameter from Φ4.0mm to Φ2.5mm by three drawing processes again, and finally are fine-drawn to Φ2.4mm. The surface of the submerged arc welding material made of the wire rods does not need to be plated with copper. The submerged arc welding material is welded by using flux protection, and can meet the requirements of extremely low-temperature service.

[0028] The welding is performed by using the above method, and the weld is well formed and qualified by flaw detection. The weld has a low-temperature impact of 46, 51 and 52J at -269°C, and meets the use requirements.

[0029] Example 2

[0030] The chemical composition of the high-strength extremely low-temperature welding material wire rod includes C of 0.62wt%, Si of 0.01wt%, Mn of 25.8wt%, Cr of 1.15wt%, Ni of 15.5wt%, Mo of 2.2wt%, N of 0.15wt%, Cu≤0.15wt%, Ti≤0.012wt%, V≤0.02wt%, P≤0.002wt%, S≤0.002wt%, and the balance of Fe and inevitable impurities.

[0031] The steel is smelted with the above chemical composition, and then is made into 150mm square billets by die casting and subsequent forging and rolling. The square billets need to be surface ground with a depth of not less than 7mm and be chamfered. After surface grinding, the square billets are uniformly coated with ZS-1021 high-temperature oxidation-resistant paint, and then are placed in a heating furnace at 980°C for 4.5 hours, and then are sent to a wire rod rolling unit to be rolled into Φ6.5mm wire rods at a temperature of 1010-1030°C. The wire rods are prepared by strong air cooling after rolling.

[0032] The wire rod is drawn by an uncoiling machine, surface oxide is removed by sand belt polishing, then is reduced in diameter from Φ6.5mm to Φ4.0mm by three drawing, then is annealed, the annealing process is 780℃ for 4 hours furnace cooling, after annealing, is again drawn from Φ4.0mm to Φ2.5mm by three drawing, and finally is fine drawn to Φ2.4mm, the surface of the submerged arc welding material made of the wire rod does not need to be plated with copper. The submerged arc welding material is welded by using flux protection, and can meet the requirement of service at extremely low temperature.

[0033] The welding is carried out by using the above method, the weld is well formed, and the flaw detection is qualified. The weld is 34, 40, 37J at -269℃ low temperature impact, and meets the use requirement.

[0034] Example 3

[0035] The chemical components of the high-strength extremely low-temperature welding material wire rod are as follows: C is 0.49wt%, Si is 0.03wt%, Mn is 28.5wt%, Cr is 1.15-6.23wt%, Ni is 10.5wt%, Mo is 3.8wt%, N is 0.22wt%, Cu≤0.15wt%, Ti≤0.012wt%, V≤0.02wt%, P≤0.002wt%, S≤0.002wt%, and the balance is Fe and inevitable impurities.

[0036] The molten steel is smelted by using the above chemical components, and is made into a 150mm square billet by a mode casting and forging rolling mode. The square billet needs to be surface ground, the grinding depth is not less than 7mm, and is chamfered. After grinding, the surface is uniformly coated with ZS-1021 high-temperature resistant and oxidation resistant paint, then the square billet is placed in a heating furnace at 980℃ for 5 hours, and is sent into a wire rod rolling unit at a temperature of 1010-1030℃ to be rolled into a Φ6.5mm wire rod. The wire rod is prepared after strong air cooling.

[0037] The wire rod is drawn by an uncoiling machine, surface oxide is removed by sand belt polishing, then is reduced in diameter from Φ6.5mm to Φ4.0mm by three drawing, then is annealed, the annealing process is 780℃ for 4 hours furnace cooling, after annealing, is again drawn from Φ4.0mm to Φ2.5mm by three drawing, and finally is fine drawn to Φ2.4mm, the surface of the submerged arc welding material made of the wire rod does not need to be plated with copper. The submerged arc welding material is welded by using flux protection, and can meet the requirement of service at extremely low temperature.

[0038] It can be understood that the welding material wire rod in the embodiment contains 25.8-30.5wt% of Mn, and the work hardening is obvious, after the diameter is reduced to a certain specification by drawing, the strength is too high to continue drawing, and needs to be annealed to reduce the strength and draw again.

[0039] The above method is used for welding, and the weld is well formed and qualified in flaw detection. The weld -269 DEG C low temperature impact is 54, 60, 57J, meeting the use requirements.

[0040] The high-strength low-temperature welding material wire rod in the foregoing embodiments 1-3 of the application can be used as liquid hydrogen storage tank welding material, the liquid hydrogen storage tank welding material surface is not plated with copper, and is welded by using flux protection, the Mn content in the weld metal is 24-28wt%, low-temperature service is realized, the low-temperature service mechanical properties of the weld metal are ensured, and great development potential is obtained in the field of liquid hydrogen.

[0041] In addition to the above embodiments, the application can have other implementation manners. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope required by the application.

Claims

1. A method for manufacturing high-strength and ultra-low temperature welding wire rod, characterized in that: The following steps are involved: Smelting: smelting molten steel according to the chemical composition and percentage of high-strength and ultra-low temperature welding wire rod; Billet making and rolling into wire rod: Billets are made by die casting followed by forging and rolling. The billets are heated and kept warm for 4.5 to 6 hours and then rolled into wire rods of the first diameter, which are then cooled after rolling. Drawing: The wire rod is uncoiled and then reduced from the first diameter to the second diameter through three drawing passes, followed by annealing. After annealing, it is again reduced from the second diameter to the third diameter through three drawing passes, and finally finished drawing to the fourth diameter.

2. The manufacturing method according to claim 1, characterized in that Before heating and heat preservation, the billet is pretreated, including surface grinding with a grinding depth of not less than 7mm, chamfering, and surface coating with anti-oxidation coating.

3. The manufacturing method according to claim 1, characterized in that In the process of billet making and rolling into wire rod, the billet is heated and kept warm and then sent to the wire rod rolling unit to be rolled into the first diameter wire rod in the temperature range of 1010-1030°C.

4. The manufacturing method according to claim 1, characterized in that Post-rolling cooling includes forced air cooling.

5. The manufacturing method according to claim 1, characterized in that During the drawing step, the wire rod is uncoiled and then sanded with a sanding belt to remove the surface oxide scale.

6. The manufacturing method according to claim 1, characterized in that In the drawing step, the annealing process is to keep the temperature at 780℃ for 4 hours and then cool the furnace.

7. The manufacturing method according to claim 1, characterized in that The first diameter is Φ6.5 mm, the second diameter is Φ4.0 mm, the third diameter is Φ2.5 mm, and the fourth diameter is Φ2.4 mm.

8. The manufacturing method according to claim 1, characterized in that The chemical components and percentages of the high-strength and ultra-low temperature welding wire rod include: C is 0.28-0.62wt%, Si is 0.01-0.03wt%, Mn is 25.8-30.5wt%, Cr is 1.15-6.23wt%, Ni is 10.5-15.5wt%, Mo is 2.2-3.8wt%, N is 0.15-0.35wt%, Cu≤0.15wt%, Ti≤0.012wt%, V≤0.02wt%, P≤0.002wt%, S≤0.002wt%, and the balance is Fe and unavoidable impurities.

9. A high-strength and ultra-low temperature welding wire rod, characterized in that: The method according to any one of claims 1 to 8 is used for manufacturing.

10. The use of the high-strength and ultra-low temperature welding wire rod as claimed in claim 9 as a welding material for liquid hydrogen storage tanks, characterized in that: The surface of the liquid hydrogen storage tank welding material is not copper-plated, and welding is performed using flux protection. The Mn content in the formed weld metal is 24-28 wt%.