Wire rod for high-strength steel gas shielded welding wire and production method

Abstract

The invention relates to a wire rod for a high-strength steel gas shielded welding wire and a production method. The wire rod comprises the following chemical components in percentage by weight: 0.060%-0.090% of C, 0.52%-0.65% of Si, 1.62%-1.73% of Mn, less than or equal to 0.014% of P, less than or equal to 0.009% of S and 0.060%-0.090% of Ti. The alloy comprises the following components in percentage by weight: 0.50-0.60% of Ni, 0.30-0.40% of Mo, less than or equal to 0.010% of Ca, less than or equal to 0.0060% of N and The method has the advantages that the steel wire rod for the gas shielded welding wire is produced through a converter, LF refining, small square billet continuous casting, heating furnace heating, controlled rolling and controlled cooling rolling and a heat preservation channel. The tensile strength of the wire rod is 743-789 MPa, the elongation is 22%-25.5%, and the requirements for the mechanical property, the drawing property and the welding seam quality of the wire rod are met.

Description

Technical Field

[0001] The invention belongs to the field of welding materials and relates to a wire rod for high-strength steel gas shielded welding wire and a production method. Background Art

[0002] With the progress of steel materials and the improvement of strength levels, the requirements for corresponding high-strength welding materials are gradually increasing. ER50-G5 wire rod for special gas shielded welding wire is a high-end high-quality product of new steel grades, new processes and new technologies. It can be widely used in ships, engineering machinery, boilers and pressure vessels, lifting and transportation equipment, pipelines, heavy-duty vehicles, etc. The domestic demand is 20,000 to 30,000 tons, accounting for about 2.0% of the demand for gas shielded solid welding wire.

[0003] ER50-G5 has a high tensile strength due to its high alloy addition. The wire rod must be recrystallized and annealed before wire making, and the content of high-cost alloy elements Ti, Mo, and Ni in the wire rod is relatively high. Under the production conditions of small square billet continuous casting equipment, a certain amount of aluminum is added to ensure the recovery rate of Ti elements, and a large amount of high-melting-point inclusions such as Al2O3 and MgO-Al2O3 are generated in the molten steel, making the molten steel viscous and easily accumulated at the nozzle to form a nozzle "nodule", resulting in poor surface quality of the continuous casting billet and wire rod, and low yield rate. Summary of the invention

[0004] The purpose of the present invention is to provide a wire rod for high-strength steel gas shielded welding wire and a production method, which can meet the mechanical properties of the wire rod and improve the drawing performance and weld quality. By increasing the content of Mn and Mo to increase the tensile strength, adding a proper amount of Ni element to improve the toughness of the weld, and reducing the content of P and S, the mechanical properties of the weld are stabilized and the crack resistance of the weld is improved.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] A high-strength steel wire rod for gas shielded welding wire comprises the following chemical components by weight percentage:

[0007] C: 0.060%~0.090%, Si: 0.52%~0.65%, Mn: 1.62%~1.73%, P≤0.014%, S≤0.009%, Ti: 0.06 0%~0.090%; Ni: 0.50%~0.60%, Mo: 0.30%~0.40%, Ca≤0.010%, N≤0.0060%, Alt≤0.010%.

[0008] The wire rod has a tensile strength of 743-789 MPa, an elongation of 22%-25.5%, a cross-sectional shrinkage of 64%-70%, and non-metallic inclusions: A+C≤1.5; B+D≤1.5.

[0009] The metallographic structure of the wire rod is: ferrite+pearlite, the volume percentage of ferrite is 85% to 90%, and the volume percentage of pearlite is 10% to 15%.

[0010] The reasons for the selection of ingredients and the mechanism of action of the present invention are described below:

[0011] C: It is the most important strengthening element, but it will strongly deteriorate the plasticity, toughness and weldability. Studies have shown that when the Mn content is high, the cross-sectional shrinkage and elongation of the steel decrease, the cold working performance of the steel deteriorates, and it is not conducive to drawing. In order to obtain good cold drawing performance, the C content is strictly controlled at a low level, and the C content is controlled at 0.060wt% to 0.090wt%.

[0012] Si: Silicon has a strong solid solution strengthening effect and greatly improves the work hardening rate. Too high Si content leads to increased deformation resistance during cold drawing and tends to reduce plastic toughness. At the same time, Si oxidation forms inclusions, which will cause serious damage to the weld. Therefore, the Si content is controlled at 0.52wt% to 0.65wt%.

[0013] Mn: It has the effects of solid solution strengthening and fine grain strengthening, and can improve the strength of steel. If the Si content is too high, the phase transition temperature will be greatly reduced, bainite structure will be easily formed, and the toughness of the steel will be damaged. Considering the basic strength of the steel, the Mn content is controlled at 1.62wt% to 1.73wt%.

[0014] P / S: Phosphorus and sulfur are harmful elements in steel. Phosphorus dissolves in ferrite. Although it can improve the strength and hardness of steel, its biggest harm is serious segregation, increased temper brittleness, and significantly reduced plasticity and toughness of steel, making steel easy to crack during cold processing, which is the so-called "cold brittleness" phenomenon; sulfur reduces the plasticity of steel, increases the brittleness of steel, and deteriorates the quality of steel. P≤0.014%, S≤0.009%.

[0015] Ti: During welding, Ti can combine with N and O to form TiN and TiO particles as crystal nuclei, which prevent the growth of austenite grains during welding heating and refine the austenite grains of the weld. At the same time, it can serve as a phase transformation core during welding cooling to form intracrystalline acicular ferrite, which improves the toughness of the weld. However, if Ti is excessive, a large number of TiC and TiN particles will be formed, which will reduce the toughness. Ti content 0.060% ~ 0.090%

[0016] Ni: helps to improve the toughness of the weld metal and reduce the ductile-brittle transition temperature. Ni: 0.50% to 0.60%

[0017] Mo: A certain amount of Mo in the weld is beneficial to increase the content of acicular ferrite in the weld, reduce proeutectoid ferrite, and refine the ferrite grains, thereby improving the strength and toughness of the weld. Mo: 0.30% to 0.40%

[0018] Ca: Control the Ca content to prevent spatter during welding.

[0019] N: Control the N content to reduce the amount of nitride formed with Ti and ensure smooth drawing. Therefore, N≤0.0060%.

[0020] A method for producing a wire rod for high-strength steel gas shielded welding wire comprises the following process paths:

[0021] Hot metal from blast furnace → hot metal pretreatment → converter smelting → argon blowing from ladle bottom → LF furnace refining → continuous casting → slow cooling of billet → heating in walking beam furnace → rolling process → wire laying → inspection → coiling → slow cooling in insulation channel;

[0022] 1) Converter smelting:

[0023] Molten iron + refined scrap steel are used as raw materials, the molten iron content in the raw materials is 88wt% to 90wt%; 5.8 to 6.2 kg / t of nickel plate and 6.2 to 6.8 kg / t of ferromolybdenum are added with the refined scrap steel, oxygen is blown from top to bottom, the tapping temperature is 1650 to 1680°C, and the weight percentage of C at the tapping end point is 0.040% to 0.050%;

[0024] For converter double slag smelting, P≤0.008wt% for one-time pouring, slag discharge is strictly prohibited;

[0025] Amount of auxiliary materials added per ton of steel: 48-52kg / t of active lime, 18-20kg / t of dolomite, 17.5-19.5kg / t of Australian ore; auxiliary materials are not added in one batch, but in two or three batches;

[0026] Ladle alloying: when 1 / 4 to 1 / 3 of the steel is tapped, lime, pre-deoxidizer and ferroalloy are added for deoxidation and alloying, and the argon blowing time is ≥5min; the target amount of alloy added per ton of steel: low carbon ferromanganese 20kg / t;

[0027] 2) Argon blowing at the bottom of the ladle: static argon blowing time ≥ 8min, temperature before treatment 1585 ~ 1600℃, temperature after treatment 1570 ~ 1590℃, feeding pure calcium cored wire 1 ~ 1.2kg / t after static argon blowing, feeding wire speed 2 ~ 3m / s;

[0028] 3) LF furnace refining: LF refining time 60-80min, full analysis temperature 1560-1600℃;

[0029] Amount of auxiliary materials added per ton of steel: active lime 7.1-7.5kg / t, fluorite 0.55-0.60kg / t, carbide slag 0.45-0.50kg / t, medium carbon ferromanganese 2.4-2.6kg / t, low calcium ferrosilicon 8.5-9.0kg / t, ferrosilicon powder 0.66kg / t, ferrotitanium FeTi70 2.8-3.0kg / t, soft blowing time ≥12min, calcium feeding line 80m-100m;

[0030] 4) Continuous casting: crystallizer electromagnetic stirring current 220 ~ 260A, frequency 4 ~ 6Hz, forward and reverse; terminal electromagnetic stirring current 230 ~ 270A, frequency 4 ~ 8Hz, continuous rotation; continuous casting ladle platform temperature 1595 ~ 1605 ℃, tundish temperature 1555 ~ 1565 ℃, superheat maintained at 25 ~ 35 ℃, casting speed 2.2 ~ 2.4m / min; full process protection casting, crystallizer protective slag using billet low carbon steel protective slag;

[0031] 5) Heating in heating furnace: preheating section 860-900°C, heating section 1080-1120°C, soaking section 1120-1160°C, heating time 1.5-2.5h;

[0032] 6) Rolling process:

[0033] Rough rolling temperature: 990~1030℃; Finishing rolling inlet temperature: 860~900℃; Wire laying temperature: 860~900℃; Air cooling roller speed: Head roller speed: 0.12~0.15m / s; Insulation cover is fully closed;

[0034] 7) Slow cooling in the insulation channel: The slow cooling temperature in the insulation channel is 60-100℃.

[0035] In the LF furnace refining process, white slag operation is performed to control the slag basicity and the oxygen potential in the slag while ensuring the slag fluidity.

[0036] The auxiliary materials described in step 1) are added from the start of blowing in the early stage of smelting to 5 minutes before the end of smelting.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention adopts the production process of "converter + LF refining + billet continuous casting + heating furnace heating + controlled rolling and controlled cold rolling + insulation channel" to produce wire rod for gas shielded welding wire. The composition design increases the content of Mn and Mo to improve the tensile strength, and the toughness of the weld is improved by adding an appropriate amount of Ni element, and the content of P and S is reduced to stabilize the mechanical properties of the weld and improve the crack resistance of the weld. The tensile strength of the wire rod is 743-789MPa, the elongation is 22%-25.5%, the cross-sectional shrinkage is 64%-70%, and the non-metallic inclusions are: A+C≤1.5; B+D≤1.5, which meets the mechanical properties of the wire rod and can also meet the drawing performance and weld quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the metallographic structure diagram of high-strength steel wire rod for gas shielded welding wire. DETAILED DESCRIPTION

[0040] The present invention is described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0041] Chemical composition of high-strength steel gas shielded welding wire wire rod (by weight percentage):

[0042] C: 0.060%~0.090%, Si: 0.52%~0.65%, Mn: 1.62%~1.73%, P≤0.014%, S≤0.009%, Ti: 0.06 0%~0.090%; Ni: 0.50%~0.60%, Mo: 0.30%~0.40%, Ca≤0.010%, N≤0.0060%, Alt≤0.010%.

[0043] See Figure 1 The metallographic structure of the wire rod is: ferrite + pearlite, the volume percentage of ferrite is 85% to 90%, and the volume percentage of pearlite is 10% to 15%. The outer diameter of the wire rod is φ5.5 to φ6.5 mm.

[0044] In order to ensure the quality of high-strength steel wire rod for gas shielded welding wire (ER50-G5), effective measures such as molten steel superheat, billet drawing speed, continuous casting crystallizer electromagnetic stirring and end electromagnetic stirring are used to control defects such as carbon center segregation, billet center looseness or shrinkage. The specific production method includes the following process paths:

[0045] Hot metal from blast furnace → hot metal pretreatment (desulfurization and slag removal) → 120t converter (top and bottom combined blowing) → argon blowing from ladle bottom → LF furnace refining → 150×150mm square billet continuous casting (electromagnetic stirring in crystallizer and electromagnetic stirring at the end of solidification) → slow cooling of billet → heating in walking beam heating furnace → rolling process → wire laying → inspection → coiling → slow cooling in insulation channel → sampling, inspection and judgment → packaging and delivery to warehouse.

[0046] 1. Converter smelting:

[0047] Molten iron + scrap steel: Molten iron content is 88wt%~90wt%, scrap steel is refined scrap steel, slag steel is prohibited, accounting for 10wt%~12wt%; nickel plate 5.9~6.1kg / t, ferromolybdenum 6.4~6.6kg / t are added with refined scrap steel; oxygen top and bottom blowing, tapping temperature is 1650~1680℃, and C content at the tapping end is 0.040%~0.050%;

[0048] For double slag smelting in converter, the target is P≤0.008% in one pouring, and slag discharge is strictly prohibited.

[0049] Amount of auxiliary materials added per ton of steel: 48-52kg / t of active lime, 18-20kg / t of dolomite, and 17.5-19.5kg / t of Australian ore. The time for adding auxiliary materials is from the start of blowing in the early stage of smelting to 5 minutes before the end of smelting. Auxiliary materials are not added in batches, but in two or three batches to prevent splashing caused by intense reaction after concentrated addition.

[0050] Ladle alloying: when 1 / 4 to 1 / 3 of the steel is tapped, lime (for slag formation), pre-deoxidizer and ferroalloy are added for deoxidation and alloying, and the argon blowing time is ≥5min; the target amount of alloy added per ton of steel is: 20kg / t of low-carbon ferromanganese.

[0051] 2. Argon blowing at the bottom of the ladle: static argon blowing time ≥ 8min, temperature before treatment 1585~1600℃, temperature after treatment 1570℃~1590℃, feeding pure calcium cored wire 1~1.2kg / t after static argon blowing, feeding wire speed 2~3m / s;

[0052] 3. LF furnace refining: white slag operation is required. Under the condition of ensuring slag fluidity, the slag basicity and oxygen potential in the slag should be controlled; the molten steel should be tested from time to time and the alloy should be fine-tuned to ensure that the composition of the molten steel meets the standard requirements; the LF refining time is 60 to 80 minutes, and the full analysis temperature is 1560 to 1600°C. The full analysis temperature is the temperature detected during the entire LF furnace refining process.

[0053] The amount of auxiliary materials added per ton of steel: active lime 7.1-7.5kg / t, fluorite 0.55-0.60kg / t, carbide slag 0.45-0.50kg / t, medium carbon ferromanganese 2.4-2.6kg / t, low calcium ferrosilicon 8.5-9.0kg / t, ferrosilicon powder 0.66kg / t, ferrotitanium FeTi70 2.8-3.0kg / t. The molten steel is tested from time to time and the alloy is fine-tuned to ensure that the composition of the molten steel meets the standard requirements. The soft blowing time is ≥12min and the calcium feeding line is 80m-100m.

[0054] 4. Continuous casting: The crystallizer electromagnetic stirring current is 220-260A, the frequency is 4-6Hz, and the rotation is positive and negative; the end electromagnetic stirring current is 230-270A, the frequency is 4-8Hz, and the rotation is continuous; the temperature of the ladle platform for continuous casting is 1595-1605℃, the temperature of the middle ladle is 1555-1565℃, the superheat is maintained at 25-35℃, and the casting speed is 2.2-2.4m / min. The whole process is protected casting, and the crystallizer protective slag uses square billet low-carbon steel protective slag; the billet cutting adopts a combination of automatic and manual methods.

[0055] 5. Heating in heating furnace: preheating section 860-900℃, heating section 1080-1120℃, soaking section 1120-1160℃, heating time 1.5-2.5h (preheating section 25-42min, heating section 40-65min + soaking section 25-42min); the heating furnace uses a walking-beam heating furnace.

[0056] 6. Rolling process:

[0057] Rough rolling temperature: 990~1030℃; finishing rolling entrance temperature: 840~880℃; spinning temperature 860~900℃; air-cooled roller speed: head roller 0.12~0.15m / s; the insulation cover above the air-cooled roller is in a fully closed state, which plays a role in insulation and is conducive to organizational transformation.

[0058] 7. Insulation channel: The insulation channel ensures the temperature of 60-100℃. The insulation channel is effectively utilized to ensure the effective release of tissue stress and internal stress, thereby ensuring the performance of the product and the performance requirements of the cleaning rod.

[0059] 8. Finished product inspection and physical and chemical indicators of finished products

[0060] ⑴ Chemical composition test results (unit: wt%):

[0061]

[0062]

[0063] (2) Result of macroscopic defect inspection of ingot (grade):

[0064]

[0065] ⑶ Mechanical properties (5 components rolled multiple times)

[0066] Example Tensile strength(MPa) Elongation(%) Sectional shrinkage (%) 1 768 25.5 66 1 754 22 69 1 755 25 64 1 758 24.5 68 2 758 22 68 2 786 23 68 3 763 22.5 70 3 753 22 66 3 765 23.5 66 3 743 22.5 66 4 746 22 68 4 764 22 64 5 772 22.5 68 5 780 24 64 5 778 24 66 5 789 23 66

[0067] ⑷Microstructure and non-metallic inclusions:

[0068]

[0069]

[0070] The present invention adopts the production process of "converter + LF refining + billet continuous casting + heating furnace heating + controlled rolling and controlled cold rolling + insulation channel" to produce wire rod for gas shielded welding wire. The composition design increases the content of Mn and Mo to improve the tensile strength, and the toughness of the weld is improved by adding an appropriate amount of Ni element, and the content of P and S is reduced to stabilize the mechanical properties of the weld and improve the crack resistance of the weld. The tensile strength of the wire rod is 743-789MPa, the elongation is 22%-25.5%, the cross-sectional shrinkage is 64%-70%, and the non-metallic inclusions are: A+C≤1.5; B+D≤1.5, which meets the mechanical properties of the wire rod and can also meet the drawing performance and weld quality.

Claims

1. A wire rod for high-strength steel gas shielded welding wire, characterized in that: The chemical components by weight percentage are as follows: C: 0.060%~0.090%, Si: 0.52%~0.65%, Mn: 1.62%~1.73%, P≤0.014%, S≤0.009%, Ti: 0.060%~0.090%; Ni: 0.50% to 0.60%, Mo: 0.30% to 0.40%, Ca≤0.010%, N≤0.0060%, Alt≤0.010%.

2. The high-strength steel gas shielded welding wire wire rod according to claim 1, characterized in that: The wire rod has a tensile strength of 743-789 MPa, an elongation of 22%-25.5%, a cross-sectional shrinkage of 64%-70%, and non-metallic inclusions: A+C≤1.5; B+D≤1.

5.

3. The high-strength steel gas shielded welding wire wire rod according to claim 1, characterized in that: The metallographic structure of the wire rod is: ferrite+pearlite, the volume percentage of ferrite is 85% to 90%, and the volume percentage of pearlite is 10% to 15%.

4. A method for producing a high-strength steel wire rod for gas shielded welding wire according to any one of claims 1 to 3, characterized in that: The following process paths are included: Hot metal from blast furnace → hot metal pretreatment → converter smelting → argon blowing from ladle bottom → LF furnace refining → continuous casting → slow cooling of billet → heating in walking beam furnace → rolling process → wire laying → inspection → coiling → slow cooling in insulation channel; 1) Converter smelting: Molten iron + refined scrap steel are used as raw materials, the molten iron content in the raw materials is 88wt% to 90wt%; 5.8 to 6.2 kg / t of nickel plate and 6.2 to 6.8 kg / t of ferromolybdenum are added with the refined scrap steel, oxygen is blown from top to bottom, the tapping temperature is 1650 to 1680°C, and the weight percentage of C at the tapping end point is 0.040% to 0.050%; For converter double slag smelting, P≤0.008wt% for one-time pouring, slag is strictly prohibited; Amount of auxiliary materials added per ton of steel: 48-52kg / t of active lime, 18-20kg / t of dolomite, 17.5-19.5kg / t of Australian ore; auxiliary materials are not added in one batch, but in two or three batches; Ladle alloying: when 1 / 4 to 1 / 3 of the steel is tapped, lime, pre-deoxidizer and ferroalloy are added for deoxidation and alloying, and the argon blowing time is ≥5min; the target amount of alloy added per ton of steel: low carbon ferromanganese 20kg / t; 2) Argon blowing at the bottom of the ladle: static argon blowing time ≥ 8min, temperature before treatment 1585 ~ 1600℃, temperature after treatment 1570 ~ 1590℃, feeding pure calcium cored wire 1 ~ 1.2kg / t after static argon blowing, feeding wire speed 2 ~ 3m / s; 3) LF furnace refining: LF refining time 60-80min, full analysis temperature 1560-1600℃; Amount of auxiliary materials added per ton of steel: active lime 7.1-7.5kg / t, fluorite 0.55-0.60kg / t, carbide slag 0.45-0.50kg / t, medium carbon ferromanganese 2.4-2.6kg / t, low calcium ferrosilicon 8.5-9.0kg / t, ferrosilicon powder 0.66kg / t, ferrotitanium FeTi70 2.8-3.0kg / t, soft blowing time ≥12min, calcium feeding line 80m-100m; 4) Continuous casting: crystallizer electromagnetic stirring current 220 ~ 260A, frequency 4 ~ 6Hz, forward and reverse; terminal electromagnetic stirring current 230 ~ 270A, frequency 4 ~ 8Hz, continuous rotation; continuous casting ladle platform temperature 1595 ~ 1605 ℃, tundish temperature 1555 ~ 1565 ℃, superheat maintained at 25 ~ 35 ℃, casting speed 2.2 ~ 2.4m / min; The whole process is protected casting, and the mold protection slag uses the square billet low carbon steel protection slag; 5) Heating in heating furnace: preheating section 860-900°C, heating section 1080-1120°C, soaking section 1120-1160°C, heating time 1.5-2.5h; 6) Rolling process: Rough rolling temperature: 990~1030℃; Finishing rolling inlet temperature: 860~900℃; Wire laying temperature: 860~900℃; Air-cooled roller speed: Head roller speed: 0.12~0.15m / s; The thermal insulation cover is in the fully closed state; 7) Slow cooling in the insulation channel: The slow cooling temperature in the insulation channel is 60-100℃.

5. The method for producing a high-strength steel gas shielded welding wire according to claim 4, characterized in that: The white slag operation is performed during the LF furnace refining process to control the slag basicity and the oxygen potential in the slag while ensuring the slag fluidity.

6. The method for producing a high-strength steel gas shielded welding wire according to claim 4, characterized in that: The auxiliary materials described in step 1) are added from the start of blowing in the early stage of smelting to 5 minutes before the end of smelting.

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