ER70S-6 welding wire steel and production method thereof

Abstract

The invention relates to the technical field of welding wire steel production, and discloses ER70S-6 welding wire steel and a production method thereof, and the ER70S-6 welding wire steel comprises the following chemical components: 0.06-0.09 wt% of C, 0.82-0.88 wt% of Si, 1.43-1.50 wt% of Mn, 0.005-0.015 wt% of S, less than or equal to 0.015 wt% of P, less than or equal to 0.015 wt% of S, less than or equal to 0.015 wt% of S and the balance of Fe. By accurately controlling the contents of C, Si, Mn, S and P and the contents of gases O, N and H in the ER70S-6 welding wire steel, the cleanliness of molten steel is improved, and then the ER70S-6 welding wire steel provided by the invention can improve the low-temperature impact toughness of a welding seam, reduce the crack sensitivity of the welding seam, prevent splashing and ensure the strength and welding quality of a welding joint.

Description

Technical Field

[0001] The invention relates to the technical field of welding wire steel production, and in particular to an ER70S-6 welding wire steel and a production method thereof. Background Art

[0002] Welding wire is a metal wire welding material used as filler metal or as a conductor during the welding process. In gas welding and tungsten inert gas shielded arc welding, welding wire is used as filler metal; in submerged arc welding, electroslag welding and other metal electrode gas shielded arc welding, welding wire is both filler metal and conductive electrode.

[0003] ER70S-6 steel for gas shielded welding wire mainly adopts wire rods with specifications of φ5.5mm and φ6.5mm, which are cold drawn to φ0.8mm~φ1.2mm by downstream welding wire factories. Due to the large number of drawing passes and large cold working deformation, most welding wire manufacturers do not have an intermediate annealing process, so they put forward very high requirements on the cold deformation ability of the wire rod. The surface of the welding wire should remain smooth without defects such as burrs, scratches, and rust. In addition, the chemical composition range of the ER70S-6 welding wire steel wire rod standard is relatively large. Without strict optimization and control, its comprehensive performance is difficult to meet the user's use requirements. Some residual elements and inclusions with low melting points and volatile at high temperatures will seriously affect the welding operation, weld quality and aesthetics of the welding wire, and these elements have not been included in the standard optimization control, which makes it difficult for the welding wire wire rod produced according to the standard to meet market demand. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems in the prior art to a certain extent, and provides an ER70S-6 welding wire steel, the quality and performance of which are optimized, and can significantly improve the welding quality.

[0005] In order to achieve the above-mentioned object, the present invention provides an ER70S-6 welding wire steel, comprising the following chemical components: C: 0.06-0.09 wt %, Si: 0.82-0.88 wt %, Mn: 1.43-1.50 wt %, S: 0.005-0.015 wt %, and P≤0.015 wt %.

[0006] Preferably, the content of O is ≤50 ppm, the content of N is ≤50 ppm, and the content of H is ≤1.5 ppm.

[0007] Preferably, the Ca content is controlled within 15 ppm.

[0008] The present invention also provides a production method of ER70S-6 welding wire steel, which adopts an LD converter-LF refining-continuous casting process.

[0009] Preferably, the production method specifically comprises the following steps:

[0010] S1, blowing molten steel through a top and bottom double-blowing converter, wherein the content of C in the molten steel after blowing is 0.03-0.06% by weight, the content of P is ≤0.02% by weight, and the content of S is ≤0.02% by weight, and then tapping;

[0011] S2, the molten steel after blowing in step S1 is hoisted to the LF refining process, the number of composition adjustments is reduced, the hit rate of the end composition is improved, and the composition adjustment uses low aluminum and low calcium materials;

[0012] The argon pressure of the LF process parameter is 4 bar, which can achieve precise control of sulfur content;

[0013] S3, argon blowing and stirring: except for adjusting the composition, large overturning is prohibited to ensure positive pressure in the furnace and reduce nitrogen and oxygen absorption by molten steel; LF refining cycle is 35-40min, soft blowing time is 15-20min for the first furnace, and 10-15min for the continuous casting furnace;

[0014] S4, continuous casting and pouring speed is 1.6m / min, target superheat is 20-35℃, distribution ratio is 32:35:19:14; crystallizer electromagnetic stirring control current is 300A, frequency is 4Hz; terminal current stirring control current is 100A, frequency is 10Hz.

[0015] Preferably, in step S1, low calcium, low aluminum and low carbon ferromanganese is used during deoxidation and alloying to achieve deep deoxidation of molten steel and reduce the introduction of C, Ca and Al elements.

[0016] Preferably, in step S3, the liquid phase temperature is 1515°C; the ladle temperature is controlled: the first furnace is 1605-1615°C, and the continuous casting furnace is 1575-1590°C; the superheat of the molten steel in the tundish is 20-35°C.

[0017] Preferably, the production method also includes: during the casting process, the casing time of the large ladle is controlled within 3 minutes to reduce the bare pouring time of molten steel; special welding wire steel covering agent is added to the middle ladle in time to avoid the liquid surface of the middle ladle being exposed to the air; and an integral nozzle is used to prevent the molten steel from inhaling air during the casting process.

[0018] Preferably, the production method further comprises: during the casting process, controlling the liquid level fluctuation to within ±3 mm.

[0019] Preferably, the production method further comprises: cold or hot rolling of the ingot off-line.

[0020] Through the above technical scheme, the cleanliness of molten steel is improved by accurately controlling the contents of C, Si, Mn, S, P and the contents of gases O, N and H in ER70S-6 welding wire steel. Furthermore, the ER70S-6 welding wire steel provided by the present invention can improve the low-temperature impact toughness of the weld, reduce the crack sensitivity of the weld, prevent spatter, and ensure the strength of the weld joint and the welding quality. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0022] The invention provides an ER70S-6 welding wire steel, which comprises the following chemical components: C: 0.06-0.09 wt %, Si: 0.82-0.88 wt %, Mn: 1.43-1.50 wt %, S: 0.005-0.015 wt %, and P≤0.015 wt %.

[0023] In the ER70S-6 welding wire steel provided by the present invention, the content of O is ≤50ppm, the content of N is ≤50ppm, and the content of H is ≤1.5ppm.

[0024] In the ER70S-6 welding wire steel provided by the present invention, the content of Ca is controlled within 15 ppm.

[0025] The inventors of the present application have found that in order to ensure the strength and welding quality of the welded joint, the carbon content of the welding material must be controlled within a narrow range; Si and Mn are jointly deoxidized to generate MnO.SiO2 with a low melting point and low density, which condenses into large pieces of slag in the weld molten pool and floats out, thereby achieving a good deoxidation effect. The remaining Si and Mn after deoxidation remain in the weld as alloy elements to compensate for the oxidation and burning of Si and Mn during the welding process, thereby ensuring the chemical composition requirements, strength and mechanical properties such as low-temperature impact toughness of the weld; and Mn can also combine with S to generate MnS that is easily deformed during the rolling process, significantly reducing or even eliminating the harmful effects of the S element, thereby achieving the purpose of reducing the tendency of hot cracks in the weld. However, a certain amount of Mn is contained in the weld. A large amount of S can also increase the flowability of the weld steel liquid, which is beneficial to improving the weld quality, so reasonable control of the S content can improve the weld quality; in addition, the inventors of the present application also found that effectively controlling the content of O and H in ER70S-6 welding wire steel is the key to improving welding performance; and, Ca is very easy to combine with O in ER70S-6 welding wire steel, and the formed CaO will increase the surface tension of the molten droplet, and has high aggregation on the surface of the molten droplet, and is easy to gather at the tip of the molten droplet. Since the arc has the characteristic of being pro-oxidant, the force area of ​​the molten droplet is reduced and the force is uneven, which leads to unstable molten droplets and prone to spattering during welding. Therefore, the Ca content is generally controlled within 15ppm.

[0026] The inventors of the present application have discovered that by precisely controlling the contents of C, Si, Mn, S, P and the contents of gases O, N and H in ER70S-6 welding wire steel, it is possible to improve the low-temperature impact toughness of the weld and reduce the crack sensitivity of the weld, prevent spattering during welding, and ensure the strength of the weld joint and the welding quality.

[0027] The present invention also provides a production method of ER70S-6 welding wire steel, which adopts the LD converter-LF refining-continuous casting process. The specific process includes: converter → LF furnace refining → continuous casting billet → walking beam heating furnace heating → high-pressure water descaling → unit rolling → diameter measuring instrument diameter measuring → wire laying machine wire laying → cooling line controlled cooling → coiling → sampling inspection, trimming → bundling → weighing, hanging → unloading → storage. In the present invention, the production of ER70S-6 welding wire steel in the present invention is achieved by controlling the initial conditions of the molten steel when the converter leaves the station, combining theoretical analysis and precise control of LF refining conditions.

[0028] In the present invention, the production method specifically comprises the following steps:

[0029] S1, blowing molten steel through a top and bottom double-blowing converter, wherein the content of C in the molten steel after blowing is 0.03-0.06% by weight, the content of P is ≤0.02% by weight, and the content of S is ≤0.02% by weight, and then tapping;

[0030] Among them, C, S, and P belong to the narrow range of component control, which reduces the final carbon content and residual element content; low calcium, low aluminum, and low carbon ferromanganese are used during deoxidation and alloying to achieve deep deoxidation of molten steel and reduce the introduction of C, Ca, and Al elements.

[0031] S2. The molten steel after blowing in step S1 is hoisted to the LF refining process to reduce the number of composition adjustments and improve the hit rate of the final composition. Low aluminum and low calcium materials are used for composition adjustment. The sulfur content of the finished product is controlled within a reasonable range. The sulfur content of the molten steel entering the LF and the sulfur content of the finished product are required. The refining sulfur line recovery rate is calculated through big data statistics. When the refining argon pressure is 3-6 bar, the sulfur line recovery rate is the highest. Therefore, the LF process parameter argon pressure is determined to be 4 bar to achieve precise control of the sulfur content.

[0032] S3, argon blowing and stirring: except for adjusting the composition, no large-scale overturning is allowed to ensure positive pressure in the furnace, effectively reducing nitrogen and oxygen absorption by molten steel; LF refining cycle is 35-40min, which should be noted that this time does not include soft blowing outside the furnace; soft blowing time for the first furnace is 15-20min, and for continuous casting furnaces is 10-15min. Refine the process control O, N measures and argon blowing and stirring to reduce the Ca, Al content and gas O, N content in molten steel;

[0033] In addition, in step S3, temperature control: liquid phase temperature is 1515°C; ladle temperature is controlled: first furnace is 1605-1615°C, continuous casting furnace is 1575-1590°C; superheat of molten steel in tundish is 20-35°C.

[0034] S4, continuous casting and pouring speed is 1.6m / min, target superheat is 20-35℃, distribution ratio is 32:35:19:14; protective slag model is special protective slag for welding wire steel; crystallizer electromagnetic stirring control current is 300A, frequency is 4Hz; end current stirring control current is 100A, frequency is 10Hz.

[0035] During the casting process, the casing time of the large ladle is controlled within 3 minutes to reduce the bare pouring time of molten steel; special welding wire steel covering agent is added to the middle ladle in time to avoid the liquid surface of the middle ladle being exposed to the air; an integral nozzle is used to prevent the molten steel from inhaling air during the casting process; and the liquid level fluctuation is controlled within ±3mm.

[0036] The ingots are stacked for cooling or sent hot for rolling.

[0037] The production method provided by the present invention can accurately control the contents of C, Si, Mn, S, P and the contents of gases O, N and H in molten steel, improve the cleanliness of molten steel, and the continuous casting protection casting adopted can ensure the castability of molten steel. The ER70S-6 welding wire steel produced based on the production method provided by the present invention can improve the low-temperature impact toughness of the weld, reduce the crack sensitivity of the weld, prevent splashing, and ensure the strength and welding quality of the welded joint; the production method provided by the present invention also has the advantages of safety, reliability and easy operation, and can successfully develop high-quality ER70S-6 welding wire steel.

[0038] Example 1

[0039] This example provides an ER70S-6 welding wire steel, the components of which are:

[0040] C: 0.070 wt%, Si: 0.083 wt%, Mn: 1.45 wt%, P: 0.012 wt%, S: 0.007 wt%, Cu: 0.022 wt%, Cr: 0.072 wt%, Ni: 0.0058 wt%, Mo: 0.012 wt%, V: 0.008 wt%, Al: 0.005 wt%, Ca: 0.0007 wt%, of which O: 23.5 ppm, N: 32 ppm, H: 1.2 ppm; the rest is Fe.

[0041] The production method of ER70S-6 welding wire steel provided in this example comprises the following steps:

[0042] S1, blowing molten steel through a top and bottom double-blowing converter, wherein the content of C in the molten steel after blowing is 0.03-0.06% by weight, the content of P is ≤0.02% by weight, and the content of S is ≤0.02% by weight, and then tapping;

[0043] Among them, C, S, and P belong to the narrow range of component control, which reduces the final carbon content and residual element content; low calcium, low aluminum, and low carbon ferromanganese are used during deoxidation and alloying to achieve deep deoxidation of molten steel and reduce the introduction of C, Ca, and Al elements.

[0044] S2. The molten steel after blowing in step S1 is hoisted to the LF refining process to reduce the number of composition adjustments and improve the hit rate of the final composition. Low aluminum and low calcium materials are used for composition adjustment. The sulfur content of the finished product is controlled within a reasonable range. The sulfur content of the molten steel entering the LF and the sulfur content of the finished product are required. The refining sulfur line recovery rate is calculated through big data statistics. When the refining argon pressure is 3-6 bar, the sulfur line recovery rate is the highest. Therefore, the LF process parameter argon pressure is determined to be 4 bar to achieve precise control of the sulfur content.

[0045] S3, argon blowing and stirring: except for adjusting the composition, large-scale overturning is prohibited to ensure positive pressure in the furnace and effectively reduce nitrogen and oxygen absorption by molten steel; the LF refining cycle is 40 minutes, which should be noted that this time does not include soft blowing outside the furnace; the soft blowing time is 15 minutes for the first furnace and 15 minutes for the continuous casting furnace. The process control O and N measures and argon blowing and stirring are refined to reduce the Ca and Al content in the molten steel and the O and N content in the gas;

[0046] In addition, in step S3, the temperature is controlled as follows: the liquid phase temperature is 1515°C; the ladle temperature is controlled as follows: the first furnace is 1610°C, the continuous casting furnace is 1580°C; the superheat of the molten steel in the tundish is 30°C.

[0047] S4, continuous casting and pouring speed is 1.6m / min, target superheat is 25℃, distribution ratio is 32:35:19:14; protective slag model is special protective slag for welding wire steel; crystallizer electromagnetic stirring control current is 300A, frequency is 4Hz; end current stirring control current is 100A, frequency is 10Hz.

[0048] During the casting process, the casing time of the large ladle is controlled within 3 minutes to reduce the bare pouring time of molten steel; special welding wire steel covering agent is added to the middle ladle in time to avoid the liquid surface of the middle ladle being exposed to the air; an integral nozzle is used to prevent the molten steel from inhaling air during the casting process; and the liquid level fluctuation is controlled within ±3mm.

[0049] The ingots are stacked for cooling or sent hot for rolling.

[0050] After testing, the performance of the ER70S-6 welding wire steel provided in this example is greatly improved compared with the existing ER70S-6 welding wire steel. Specifically, the tensile strength is increased from 530MPa to 570MPa; the yield strength is increased from 450MPa to 490MPa; the elongation is increased from 20% to 30%, and the impact performance is increased to 70J compared with 60J of the traditional process at -20℃.

[0051] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An ER70S-6 welding wire steel, characterized in that: Includes the following chemical components: C: 0.06-0.09 wt%, Si: 0.82-0.88 wt%, Mn: 1.43-1.50 wt%, S: 0.005-0.015 wt%, P≤0.015 wt%.

2. The ER70S-6 welding wire steel according to claim 1, characterized in that: The O content is ≤50ppm, the N content is ≤50ppm, and the H content is ≤1.5ppm.

3. The ER70S-6 welding wire steel according to claim 1 or 2, characterized in that: The Ca content is controlled within 15ppm.

4. A method for producing ER70S-6 welding wire steel, characterized in that: The production method adopts the LD converter-LF refining-continuous casting process.

5. The production method according to claim 4, characterized in that: The production method specifically comprises the following steps: S1, blowing molten steel through a top and bottom double-blowing converter, wherein the content of C in the molten steel after blowing is 0.03-0.06% by weight, the content of P is ≤0.02% by weight, and the content of S is ≤0.02% by weight, and then tapping; S2, the molten steel after blowing in step S1 is hoisted to the LF refining process, the number of composition adjustments is reduced, the hit rate of the end composition is improved, and the composition adjustment uses low aluminum and low calcium materials; The argon pressure of the LF process parameter is 4 bar, which can achieve precise control of sulfur content; S3, argon blowing and stirring: except for adjusting the composition, large overturning is prohibited to ensure positive pressure in the furnace and reduce nitrogen and oxygen absorption by molten steel; LF refining cycle is 35-40min, soft blowing time is 15-20min for the first furnace, and 10-15min for the continuous casting furnace; S4, continuous casting and pouring speed is 1.6m / min, target superheat is 20-35℃, distribution ratio is 32:35:19:14; crystallizer electromagnetic stirring control current is 300A, frequency is 4Hz; terminal current stirring control current is 100A, frequency is 10Hz.

6. The production method according to claim 5, characterized in that In step S1, low calcium, low aluminum and low carbon ferromanganese are used during deoxidation and alloying to achieve deep deoxidation of molten steel and reduce the introduction of C, Ca and Al elements.

7. The production method according to claim 5, characterized in that: In step S3, the liquid phase temperature is 1515°C; the ladle temperature is controlled: the first furnace is 1605-1615°C, and the continuous casting furnace is 1575-1590°C; the superheat of the molten steel in the tundish is 20-35°C.

8. The production method according to claim 5, characterized in that: The production method also includes: during the casting process, the casing time of the large ladle is controlled within 3 minutes to reduce the bare pouring time of molten steel; a special welding wire steel covering agent is added to the middle ladle in time to avoid the liquid surface of the middle ladle being exposed to the air; and an integral nozzle is used to prevent the molten steel from inhaling air during the casting process.

9. The production method according to claim 8, characterized in that: The production method further comprises: during the casting process, controlling the liquid level fluctuation to be within ±3 mm.

10. The production method according to claim 5, characterized in that: The production method further comprises: cold or hot rolling of the ingot off-line stack.