Steel wire rod with excellent drawing performance for welding wire and production method of steel wire rod

Abstract

The invention relates to a steel wire rod with excellent drawing performance for a welding wire. The steel wire rod with excellent drawing performance for the welding wire comprises the following chemical components in percentage by weight: 0.06-0.08% of C; si: 0.81 to 0.87%; mn: 1.41 to 1.47%; p is less than or equal to 0.023%; s: 0.008% to 0.015%; al < = 0.010%; ca < = 0.0010%; Ti < = 0.10%; 0.10% or less of Cr, and the balance Fe and inevitable impurities. The invention further provides a production method of the steel wire rod for the welding wire with the excellent drawing performance, and the steel wire rod for the welding wire with the excellent drawing performance is prepared by sequentially carrying out a heating procedure, a temperature control rolling procedure and a slow cooling procedure. The steel wire rod is uniform in chemical component, good in structure state and excellent in surface quality, the tensile strength ranges from 500 Mpa to 525 Mpa, and the percentage elongation after fracture is larger than or equal to 42%.

Description

Technical Field

[0001] The invention relates to the field of steel material production, and in particular to a steel wire rod for welding wire with excellent drawing performance and a production method thereof. Background Art

[0002] The development of modern engineering technology has increasingly stringent requirements on the strength, toughness, processing performance and other aspects of steel, and has increasingly higher requirements on steel materials. At present, when CO2 gas shielded welding wire steel ER50-6 is usually drawn to Φ0.8mm~Φ1.2mm through rough drawing and fine drawing, it usually breaks during drawing, which seriously affects product quality and production efficiency.

[0003] In the prior art, the drawability is generally improved by reducing the proportion of abnormal tissue in special welding wire steel. Although the proportion of abnormal tissue is controlled, the wire drawing temperature is too low, red rust will appear on the surface of the wire rod, and the iron oxide scale of the wire rod will not be completely removed during drawing, and the surface of the drawn wire will turn black.

[0004] The main problem now is to produce ferrite + pearlite welding wire rods with uniform chemical composition, good surface quality, uniform structure, and at the same time, the wire rods have good appearance and easy-to-peel iron oxide scale, so that downstream customers can obtain high-quality and good-quality wire rods. Summary of the invention

[0005] The object of the present invention is to provide a steel wire rod for welding wire with excellent drawing performance and a production method thereof, so that the quality and drawing performance of the prepared steel wire rod for welding wire are optimized.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: A first aspect of the present invention provides a steel wire rod for welding wire with excellent drawing performance, wherein the chemical composition of the steel wire rod for welding wire with excellent drawing performance is as follows in terms of weight percentage: C: 0.06~0.08%; Si: 0.81~0.87%; Mn: 1.41~1.47%; P≤0.023%; S: 0.008~0.015%; Al≤0.010%; Ca≤0.0010%, Ti≤0.10%; Cr≤0.10%, the balance is Fe and unavoidable impurities.

[0007] The second aspect of the present invention provides a method for producing a steel wire rod with excellent drawing performance for welding wire, wherein the steel wire rod with excellent drawing performance is obtained by sequentially performing a heating process, a temperature-controlled rolling process and a slow cooling process.

[0008] Furthermore, the heating process includes: heating the steel billet in sections, wherein the heating time is 90-110 minutes, the preheating section temperature is 700-800°C, the first heating section temperature is 760-840°C, the second heating section temperature is 890-970°C, and the soaking section temperature is 1060-1090°C.

[0009] Furthermore, the temperature-controlled rolling process includes: descaling the steel billet obtained in the heating process by high-pressure water and rolling it into wire rod, followed by water cooling and spinning, wherein the descaling water pressure is ≥22Mpa; the starting rolling temperature is 1000-1020°C, the final rolling temperature is 950-970°C; and the spinning temperature is 900-915°C.

[0010] Furthermore, the slow cooling process comprises: placing the wire rod obtained in the temperature-controlled rolling process on a Stelmor slow cooling line, hot-coiling and then heat-insulating and slowly cooling; Among them, the coiling temperature is 760~800℃, the temperature entering the insulation corridor is 730~770℃, the insulation slow cooling time is 90~120min, the temperature exiting the insulation corridor is ≤300℃, and the slow cooling rate is ≤1℃ / S.

[0011] Furthermore, on the Stelmor slow cooling line, the entrance roller speed is 0.152~0.168m / s, and the exit roller speed is 0.238~0.262m / s, during which the thermal insulation covers are all closed.

[0012] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: The invention reasonably designs and limits the weight percentage of chemical components in the steel wire rod for welding wire, specifically, C: 0.06-0.08%; Si: 0.81-0.87%; Mn: 1.41-1.47%; P≤0.023%; S: 0.008-0.015%; Al≤0.010%; Ca≤0.0010%, Ti≤0.10%; Cr≤0.10%, and the balance is Fe and inevitable impurities. Thus, a steel wire rod for welding wire with excellent drawing performance is provided, and the prepared wire rod has uniform chemical composition, good organizational state, excellent surface quality, tensile strength of 500-525Mpa, and elongation after fracture ≥35%. DETAILED DESCRIPTION

[0013] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] The present invention provides a steel wire rod for welding wire with excellent drawing performance, and the chemical composition of the steel wire rod for welding wire is calculated by weight percentage: C: 0.06~0.08%; Si: 0.81~0.87%; Mn: 1.41~1.47%; P≤0.023%; S: 0.008~0.015%; Al≤0.010%; Ca≤0.0010%, Ti≤0.10%; Cr≤0.10%, the balance is Fe and unavoidable impurities.

[0015] Specifically, since the addition of C element to steel can improve the hardenability and hardenability of the steel, an increase in C content will lead to cold and hot cracks in the weld, so it is not suitable to be too high. Therefore, in the present invention, the C content is controlled to be 0.06-0.08%.

[0016] Mn and Si are the main alloying elements. Under low carbon conditions, they can improve the strength of steel and ensure the straightness of welding wire. At the same time, they can also serve as deoxidizers to supplement the burning loss during welding, prevent the generation of pores, refine the molten droplets, reduce spatter, and ensure the mechanical properties of the weld. However, the increase of Mn and Si content will also increase the segregation degree and inclusion content in the steel, and banded structure will appear. Higher Mn and Si are also not conducive to drawing, aggravate wire drawing wear, and increase user costs. In addition, if the Mn and Si content in the steel billet is high, the tensile strength is high after hot rolling, the elongation is low, and it is easy to produce a quenched structure that is not easy to draw. Therefore, the content of Mn and Si is controlled at 1.41~1.47% and 0.81~0.87% respectively in the present invention.

[0017] The phosphorus element is a harmful element in steel. The plasticity and toughness of steel with a high phosphorus content are close to zero at low temperatures, resulting in cold brittleness. At the same time, phosphorus can be dissolved in ferrite, which reduces the plasticity of ferrite and increases its strength and hardness. Therefore, the phosphorus content in the present invention is controlled to be ≤0.023%.

[0018] As a harmful element, S element can generate FeS with Fe element. FeS with low melting point is easy to form "hot brittleness", so it is generally required that a certain amount of Mn be contained in the steel so that S and Mn form MnS with a higher melting point to eliminate the harm of FeS. Therefore, in the present invention, the S content is controlled at 0.008-0.015% according to the Mn content in the steel billet.

[0019] High content of Al and Ca elements will lead to large spatter during welding. In addition, Al element will be oxidized to form Al2O3 brittle inclusions, which will be arranged in a row along the rolling direction during rolling, affecting the drawing performance. Therefore, in the present invention, the content of both elements is controlled within a reasonable low range.

[0020] The addition of Ti element can significantly improve the corrosion resistance of steel. Ti element has good corrosion resistance and can form a dense oxide film; in addition, Ti element can also improve the welding performance of steel and reduce the tendency of welding deformation and cracking of steel. Moreover, the addition of Ti can reduce the grain boundary energy of steel, reduce the grain boundary migration and grain boundary diffusion of steel, improve the thermal stability of steel, simultaneously refine the grains of steel, improve the plasticity and toughness of steel, and reduce the brittleness of steel. However, if too much Ti is added, the plasticity and toughness of steel will be reduced, especially in low temperature environment, the effect of titanium on improving the toughness of steel is limited. At the same time, increasing the content of titanium will significantly increase the production cost of steel. The content of titanium is reasonably controlled to achieve the best mechanical properties and economy. Therefore, in the present invention, the content of Ti element is controlled to ≤0.10%.

[0021] The addition of Cr element is beneficial to improve the hardenability of ferroalloy. At the same time, Cr can precipitate fine dispersed carbide particles during the tempering process, which can play a role of dispersion strengthening, thereby improving the strength of the material. In addition, Cr element also has the effect of refining the structure, but too high Cr content will reduce the plasticity and toughness of steel, making it more prone to fatigue fracture and poor durability. Therefore, the present invention controls the Cr content to ≤0.10%.

[0022] The above-mentioned steel wire rod with excellent drawing performance is prepared by sequentially performing a heating process, a temperature-controlled rolling process and a slow cooling process. Specifically, each of the above-mentioned processes is described in detail below.

[0023] (1) Heating process The steel billet is heated in sections using a regenerative blast furnace gas heating furnace, wherein the preheating section temperature is 700~800℃, the first section heating temperature is 760~840℃, the second section heating temperature is 890~970℃, the soaking section temperature is 1060~1090℃, and the heating time is controlled at 90~110min. According to the above-mentioned section heating, it is avoided that the austenite grains are coarse due to too long heating time and too high heating temperature, and mixed crystal structure is easily formed after cooling. The tail temperature of the steel billet is controlled to be 20~30℃ higher than the head temperature. After heating, high-pressure water of ≥22Mpa is used for dephosphorization to ensure that the iron oxide scale on the surface of the steel billet is completely removed. Since the austenite grain size before transformation has a great influence on the phase transformation characteristics, coarse austenite grains will significantly delay the end line of phase transformation, and martensite structure is likely to appear. Therefore, the rolling temperature is strictly controlled at 1000~1020℃ for rolling to avoid coarse austenite grains and abnormal bainite structure. In terms of temperature monitoring and control, an infrared two-color thermometer is used in front of the rough rolling No. 1 rolling mill to strictly monitor the temperature so that timely adjustments can be made when the billet temperature fluctuates.

[0024] (2) Temperature controlled rolling process The steel billet obtained by the heating process is descaled under high-pressure water, and the descaling water pressure is ≥22Mpa to effectively remove the iron oxide scale on the surface of the steel billet. After descaling, the steel billet is rolled, and the rolling temperature is 1000~1020℃, and it undergoes rough rolling, intermediate rolling, pre-finishing rolling, and finishing rolling in sequence. A 1# water tank is set between the pre-finishing mill and the finishing mill. The water tank flow rate is adjusted in a timely and reasonable manner by monitoring the temperature of the rolled piece to adjust the temperature of the rolled piece to ensure that the final rolling temperature is controlled at 950~970℃, avoiding the coarse austenite grains and the formation of bainite structure. Three water tanks are set after the finishing mill to realize closed-loop temperature control, that is, the wire drawing temperature is accurately controlled by adjusting the water pressure, water volume, number of water tanks, and the number of cooling nozzles of each water tank.

[0025] After the final rolling, the wire rod is cooled by water and then spun. The spinning temperature is 900-915°C. The metallographic structure of the wire rod is mainly ferrite + pearlite structure. Due to the high content of Mn and Si in the steel, its "CCT" transformation curve moves to the lower right, delaying and prolonging the transformation time. If the spinning temperature is lower than 900°C, red rust will appear on the surface of the wire rod, affecting the appearance quality, and the wire rod oxide scale will not be removed cleanly during subsequent processing, and the surface of the drawn wire will turn black. If the spinning temperature is too high, more quenching structures will appear in the wire rod structure and the wire rod surface oxide scale will easily fall off, causing secondary oxidation. The wire rod oxide scale will not be removed cleanly, affecting the drawing. Therefore, the spinning temperature is strictly controlled at 900-915°C in the present invention. Within this temperature range, the structure of the wire rod is uniform ferrite + pearlite, and it has good drawing performance.

[0026] (3) Slow cooling process The wire rod obtained by the temperature-controlled rolling process is kept warm and slowly cooled on the Stelmor slow cooling line, and the heat preservation cover and the fan tuyere are all closed. The present invention adopts a delayed slow cooling process, and in order to make the fine-grained austenite of the wire rod transform and decompose to obtain ferrite and pearlite structures, the slow cooling rate is controlled to be ≤1°C / S, ensuring that little or no bainite is generated.

[0027] On the Stelmor slow cooling line, the entrance roller speed is controlled at 0.152~0.168m / s, and the exit roller speed is controlled at 0.238~0.262m / s, during which the insulation covers are all closed. After passing through four sections of slow cooling rollers, hot coiling is carried out, with a coiling temperature of 760~800℃, a temperature of 730~770℃ entering the insulation corridor, an average cooling rate of ≤1℃ / S, a heat preservation time of 90~120min in the insulation corridor, and a temperature of ≤300℃ out of the insulation corridor.

[0028] The specific implementation methods of the present invention are further introduced below by setting Examples 1-3 and Comparative Example 1.

[0029] Example 1 This embodiment provides a steel wire rod for welding wire with excellent drawing performance and a production method thereof, which is prepared by a heating process, a temperature-controlled rolling process and a slow cooling process. The composition control of the wire rod is shown in Table 1, and the specific process parameters are controlled as follows: The steel billet corresponding to the embodiment in Table 1 is placed in a regenerative blast furnace gas heating furnace with a furnace temperature of 1060-1090°C in the soaking section for heating, and then taken out of the furnace after heating for 100 minutes. The heated steel billet is descaled by high-pressure water and then rough rolled, with the start rolling temperature being 1000°C, followed by finishing rolling, with the finishing temperature being controlled at 950°C; cooled to 900°C by water penetration and then wire-spinning; after wire-spinning, it is cooled by slow cooling, with a cooling rate of 0.5°C / s, and the coiling temperature is 800°C, and the steel wire rod for welding wire is obtained. Example 2 This embodiment provides a steel wire rod for welding wire with excellent drawing performance and a production method thereof, which is prepared by a heating process, a temperature-controlled rolling process and a slow cooling process. The composition control of the wire rod is shown in Table 1, and the specific process parameters are controlled as follows: The steel billet corresponding to the embodiment in Table 1 is placed in a regenerative blast furnace gas heating furnace with a furnace temperature of 1060-1090°C in the soaking section for heating, and taken out of the furnace after heating for 90 minutes. The heated steel billet is descaled by high-pressure water and then rough rolled with a start rolling temperature of 1020°C, followed by finishing rolling with a control of the finishing temperature of 970°C; cooled to 915°C by water penetration for wire laying; after wire laying, it is cooled by slow cooling with a cooling rate of 0.8°C / s, the coiling temperature is 760°C, and the steel wire rod for welding wire is obtained. Example 3 This embodiment provides a steel wire rod for welding wire with excellent drawing performance and a production method thereof, which is prepared by a heating process, a temperature-controlled rolling process and a slow cooling process. The composition control of the wire rod is shown in Table 1, and the specific process parameters are controlled as follows: The steel billet corresponding to the embodiment in Table 1 is placed in a regenerative blast furnace gas heating furnace with a furnace temperature of 1060-1090°C in the soaking section for heating, and is taken out of the furnace after heating for 110 minutes. The heated steel billet is descaled by high-pressure water and then rough rolled with a starting rolling temperature of 1010°C, followed by finishing rolling with a finishing temperature of 960°C; it is cooled to 910°C through water penetration for wire laying; after wire laying, it is cooled by slow cooling with a cooling rate of 1°C / s, a coiling temperature of 780°C, and is kept warm and slowly cooled for 100 minutes to obtain the steel wire rod for welding wire.

[0030] Comparative Example 1 This embodiment provides a steel wire rod for welding wire with excellent drawing performance and a production method thereof, which is prepared by a heating process, a temperature-controlled rolling process and a slow cooling process. The composition control of the wire rod is shown in Table 1, and the specific process parameters are controlled as follows: The steel billet corresponding to the embodiment in Table 1 is placed in a regenerative blast furnace gas heating furnace with a furnace temperature of 1060-1090°C in the soaking section for heating, and is taken out of the furnace after heating for 115 minutes. The heated steel billet is descaled by high-pressure water and then rough rolled with a starting rolling temperature of 1050°C, followed by finish rolling with the finishing temperature of the finish rolling controlled at 1000°C; it is cooled to 950°C through water penetration and wire-spinning is performed; after wire-spinning, it is cooled by slow cooling with a cooling rate of 3°C / s, a coiling temperature of 721°C, and is kept warm and slowly cooled for 90 minutes to obtain the steel wire rod for the welding wire.

[0031] Comparative Example 2 This embodiment provides a steel wire rod for welding wire with excellent drawing performance and a production method thereof, which is prepared by a heating process, a temperature-controlled rolling process and a slow cooling process. The composition control of the wire rod is shown in Table 1, and the specific process parameters are controlled as follows: The steel billet corresponding to the embodiment in Table 1 is placed in a regenerative blast furnace gas heating furnace with a furnace temperature of 1060-1090°C in the soaking section for heating, and is taken out of the furnace after heating for 115 minutes. The heated steel billet is descaled by high-pressure water and then rough rolled with a start rolling temperature of 1030°C, followed by finish rolling with a control of the finish rolling end temperature of 980°C; it is cooled to 950°C through water penetration and wire-spinning is performed; after wire-spinning, it is cooled by slow cooling with a cooling rate of 1.5°C / s, a coiling temperature of 741°C, and is kept warm and slowly cooled for 100 minutes to obtain the steel wire rod for the welding wire.

[0032] Comparative Example 3 This embodiment provides a steel wire rod for welding wire with excellent drawing performance and a production method thereof, which is prepared by a heating process, a temperature-controlled rolling process and a slow cooling process. The composition control of the wire rod is shown in Table 1, and the specific process parameters are controlled as follows: The steel billet corresponding to the embodiment in Table 1 is placed in a regenerative blast furnace gas heating furnace with a furnace temperature of 1060-1090°C in the soaking section for heating, and is taken out of the furnace after heating for 150 minutes. The heated steel billet is descaled by high-pressure water and then rough rolled with a starting rolling temperature of 980°C, followed by finish rolling with a control of the finishing temperature of 930°C; it is cooled to 870°C through water penetration and wire is spun; after wire is spun, it is cooled by slow cooling with a cooling rate of 3°C / s, a coiling temperature of 701°C, and is kept warm and slowly cooled for 100 minutes to obtain the steel wire rod for the welding wire.

[0033] Table 1 Chemical composition / % C Si Mn P S Al Cr Ca Ti Example 1 0.06 0.81 1.41 0.023 0.008 0.010 0.10 0.0010 0.100 Example 2 0.08 0.85 1.44 0.020 0.010 0.008 0.06 0.0008 0.070 Example 3 0.07 0.87 1.47 0.010 0.015 0.005 0.01 0.0005 0.050 Comparative Example 1 0.09 0.80 1.35 0.030 0.020 0.015 0.20 0.0150 0.200 Comparative Example 2 0.09 0.9 1.50 0.024 0.018 0.013 0.17 0.0200 0.016 Comparative Example 3 0.09 0.70 1.35 0.025 0.015 0.0012 0.12 0.011 0.013 At the same time, the performance of the wire rods prepared in the above embodiments and comparative examples was tested, and the test results are shown in Table 2.

[0034] Table 2 Performance test results Specification / mm Tensile strength / Mpa Yield strength / Mpa Sectional shrinkage / % Elongation after break / % Bainite volume percentage / % Mechanical stripping rate of iron oxide scale / % Example 1 5.5 516 383 81 36 0 97.2 Example 2 5.5 500 389 81 36 0 97.1 Example 3 5.5 525 381 80 35 0 97.4 Comparative Example 1 5.5 486 360 76 34 5 94.6 Comparative Example 2 5.5 556 368 77 30 3.2 95.2 Comparative Example 3 5.5 470 365 72 35 4.6 95.5 It can be seen from the above embodiments and comparative examples that the cold heading steel wire rod and the preparation method thereof in the embodiments of the present invention are obtained by heating, temperature-controlled rolling and slow cooling of a steel billet with reasonably controlled key elements, and in the above process, the heating time, starting rolling temperature, final rolling temperature, wire drawing temperature, slow cooling speed and other aspects are strictly controlled. After analysis and detection, there is no abnormal structure such as bainite, and the mechanical properties such as tensile strength and yield strength are excellent, which meet the needs of subsequent drawing welding wire and customers. Its excellent mechanical properties and organizational composition and good mechanical stripping rate make it easy to remove the iron oxide scale to obtain welding wire with good surface color during welding wire drawing, and at the same time, the wire breakage rate is ≤0.05 times / ton when the φ5.5mm welding wire steel wire rod is drawn into φ0.8~φ1.2 welding wire, and the maximum drawing speed reaches 30m / s. The welding wire steel wire rods obtained in the comparative examples all have abnormal bainite structures and mixed crystal phenomena of varying degrees due to the key elements in the composition not being within the control range and improper process control during the production process. Among them, the wire rods in comparative example 3 have red rust due to the low wire drawing temperature. The maximum drawing speed of the steel wire rods in the comparative examples is only 22m / s and the wire breakage rate is high.

[0035] In summary, based on the reasonable design of the components and mass percentage of the steel wire rod for welding wire, the prepared wire rod has a tensile strength of 500-525Mpa and an elongation after break of ≥35%. In addition, the present invention takes into account and solves the problems that may occur in the drawing of welding wire steel, such as the fracture effect caused by inclusions, excessive spatter during welding, mold loss, and poor wire feeding. The produced welding wire steel wire rod with excellent drawing performance has a wire breakage rate of ≤0.05 times / ton during drawing in actual applications.

[0036] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A steel wire rod for welding wire with excellent drawing performance, characterized in that: The chemical composition of the steel wire rod with excellent drawing performance is calculated by weight percentage: C: 0.06~0.08%; Si: 0.81~0.87%; Mn: 1.41~1.47%; P≤0.023%; S: 0.008~0.015%; Al≤0.010%; Ca≤0.0010%, Ti≤0.10%; Cr≤0.10%, the balance is Fe and unavoidable impurities.

2. A method for producing a steel wire rod with excellent drawing performance for welding wire as claimed in claim 1, characterized in that: The steel wire rod for welding wire with excellent drawing performance is obtained by sequentially performing a heating process, a temperature-controlled rolling process and a slow cooling process.

3. The method for producing a steel wire rod with excellent drawing performance for welding wire according to claim 2, characterized in that: The heating process includes: heating the steel billet in sections, wherein the heating time is 90-110 minutes, the preheating section temperature is 700-800°C, the first heating section temperature is 760-840°C, the second heating section temperature is 890-970°C, and the soaking section temperature is 1060-1090°C.

4. The method for producing a steel wire rod with excellent drawing performance for welding wire according to claim 2, characterized in that: The temperature-controlled rolling process comprises: descaling the steel billet obtained in the heating process by high-pressure water, rolling it into a wire rod, and then cooling it with water before spinning, wherein the descaling water pressure is ≥22Mpa; the starting rolling temperature is 1000-1020°C, the final rolling temperature is 950-970°C; and the spinning temperature is 900-915°C.

5. The method for producing a steel wire rod with excellent drawing performance for welding wire according to claim 2, characterized in that: The slow cooling process comprises: placing the wire rod obtained in the temperature-controlled rolling process on a Stelmor slow cooling line, hot-coiling and then heat-insulating and slowly cooling; Among them, the coiling temperature is 760~800℃, the temperature entering the insulation corridor is 730~770℃, the insulation slow cooling time is 90~120min, the temperature exiting the insulation corridor is ≤300℃, and the slow cooling rate is ≤1℃ / S.

6. The method for producing a steel wire rod with excellent drawing performance for welding wire according to claim 5, characterized in that: On the Stelmor slow cooling line, the entrance roller speed is 0.152~0.168m / s, and the exit roller speed is 0.238~0.262m / s, during which the thermal insulation covers are all closed.