Production method for improving nib-shaped fracture of steel wire rod for welding wire

Abstract

The invention relates to a production method for improving nib-shaped fracture of a steel wire rod for a welding wire, which comprises the following steps: firstly, adding molten iron and scrap steel into a converter for smelting to obtain molten steel, sequentially adding ferrosilicon, silicomanganese and lime into the molten steel in the tapping process, and then carrying out LF (ladle furnace) refining; and then carrying out protective casting, then carrying out segmented heating on a steel billet, rolling the steel billet into a wire rod, then carrying out water cooling, cooling and spinning, finally placing the wire rod on a Stelmor slow cooling line for slow cooling, and then sending the wire rod into a heat preservation vestibule for slow cooling. The steel wire rod for the welding wire has good quality and stable mechanical properties from inside to outside through component control and process adjustment and optimization aiming at factors such as carbon segregation and inclusions in the production process, so that the phenomenon that the steel wire rod for the welding wire is fractured in a nib shape in the drawing process is improved, and the drawing efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel rolling production, in particular to a production method for improving the pen-shaped fracture of a steel wire rod for welding wire. Background Art

[0002] In the drawing of welding wire steel, various fracture phenomena often occur, among which a pen-shaped fracture occurs particularly frequently. In addition to the pen-shaped fracture, there are often plastic deformation dimple-shaped tensile sections around it. Further analysis shows that the center is often severely C segregated, and inclusions of varying sizes are accompanied nearby. Therefore, the pen-shaped fracture in drawing is often caused by a combination of multiple factors.

[0003] Invention patent CN117324607A discloses a ladle and a method for efficiently removing inclusions from molten steel, but does not mention the element segregation problem. Invention patent CN113084110A discloses a method for reducing carbon segregation in alloy steel, but mainly solves the C segregation problem by controlling the continuous casting process. The method involves fewer processes and lacks other related process flows in terms of completeness.

[0004] Pencil-tip fracture is a fracture phenomenon that occurs frequently and seriously in wire drawing, and is a problem that needs to be solved urgently in wire drawing. Summary of the invention

[0005] The purpose of the present invention is to provide a production method for improving the pen-shaped fracture of steel wire rod for welding wire, so as to solve the problem of pen-shaped fracture occurring in the drawing process of steel wire rod for welding wire.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention provides a production method for improving the pen-shaped fracture of a steel wire rod for welding wire, comprising the following steps:

[0008] S1: molten steel smelting, adding molten iron and scrap steel into a converter for smelting to obtain molten steel, and adding ferrosilicon-silicon manganese-lime to the molten steel in sequence during the steel tapping process; wherein the scrap steel ratio is 10-15%, and the steel tapping temperature is 1600-1650°C;

[0009] S2: LF refining, lime, ferrosilicon powder and silicon carbide are added in batches for diffusion deoxidation per ton of steel, and the basicity of the final slag is controlled to be 1.5-1.9; after LF arrives at the station, samples are taken when the slag surface is clean and the molten steel temperature is ≥1540℃, and the composition is adjusted according to the sampling, and the sulfur line is fed according to the last sampling to make the S content meet the standard, and the soft blowing time is controlled to be not less than 15min;

[0010] S3: Casting, the molten steel obtained in the refining step is subjected to protective casting, the superheat of the molten steel in the tundish of the open-casting furnace is 25-30°C, the superheat of the molten steel in the tundish of the continuous casting furnace is 15-20°C, when the specification of the ingot is 150*150mm, the pulling speed is 2.39-2.43m / min, when the specification of the ingot is 180*180mm, the pulling speed is 1.58-1.62m / min;

[0011] S4: heating, heating the steel billet obtained in the casting process in sections, wherein the preheating section temperature is 700-800°C, the first section heating temperature is 760-840°C, the second section heating temperature is 890-970°C, and the soaking section temperature is 1060-1090°C. The temperature difference between the head, middle and tail of the steel billet in the heating furnace is controlled to be ≤30°C, wherein the temperature of the tail is 20-25°C higher than that of the head, and the temperature of the head is 5-10°C higher than that of the middle;

[0012] S5: temperature-controlled rolling, rolling the steel billet obtained in the heating step into a wire rod, cooling it with water, and then spinning, wherein the starting rolling temperature is 1000-1020°C, the final rolling temperature is 950-970°C, and the spinning temperature is 900-920°C;

[0013] S6: Slow cooling and heat preservation. The wire rod obtained in the temperature-controlled rolling process is placed on a Stelmor slow cooling line for slow cooling, and then sent into a heat preservation corridor for slow cooling. The Stelmor slow cooling rate is ≤1°C / S, the temperature entering the heat preservation corridor is 730-770°C, the heat preservation time in the heat preservation corridor is 90-150min, and the temperature exiting the heat preservation corridor is ≤300°C.

[0014] Furthermore, the chemical elements of the applicable steel wire rod for welding wire are, in mass percentage, C: 0.06-0.075%, Si: 0.81-0.87%, Mn: 1.41-1.47%, P≤0.023%, S: 0.008-0.015%, A1≤0.010%, Ca≤0.0010%, Ti≤0.10%, Cr≤0.10%, and the balance is Fe and unavoidable impurities.

[0015] Furthermore, in step S1, before the molten iron is smelted, it is also necessary to perform KR desulfurization on the molten iron. The molten iron is taken every 4 minutes to analyze the S content. When the S content is between 0.002% and 0.006%, the desulfurization is stopped and slag removal is performed. The slag removal rate is ≥95%. After KR desulfurization, the molten iron has a C content of 3.8% to 4.2% and an S content of 0.002% to 0.006%.

[0016] Furthermore, in step S1, when the S content of the molten steel is 0.010-0.012%, it is not necessary to add the sulfur-containing slag; when the S content of the molten steel is ≤0.010%, the sulfur-containing slag is added before adding the ferrosilicon alloy to the molten steel.

[0017] Furthermore, in step S1, the element contents of the molten steel at the end point of smelting are: C: 0.03-0.05%, O: 0.003-0.015%, P≤0.015%, S: 0.010-0.012%.

[0018] Furthermore, in step S1, during the steel tapping process, the ladle bottom blowing and stirring are turned on throughout the whole process, the ladle bottom blowing flow rate is 400-500L / min, the obtained slag basicity CaO / SiO2=1.5-1.9, T.Fe+MnO content is 1-3%, and the bottom blowing flow rate at the end of steel tapping is 90-150NL / min.

[0019] Furthermore, in step S2, when the composition is adjusted according to the sampling, when the content of Si and Mn is adjusted, silicon-manganese alloy is used; when only the Si content is adjusted, low-titanium and low-aluminum ferrosilicon is used.

[0020] Furthermore, in step S6, on the Stelmor slow cooling line, the entrance roller speed is 0.152-0.168 m / s, and the exit roller speed is 0.237-0.262 m / s.

[0021] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0022] The present invention adjusts and refines various process parameters of the production process from molten steel smelting to heat preservation and slow cooling to prepare a welding wire steel wire rod with uniform element distribution, few inclusions, a grain size of 8 to 10, and no abnormal structure, thereby solving the problem of pen-shaped fractures occurring during welding wire drawing. DETAILED DESCRIPTION

[0023] 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.

[0024] The present invention provides a production method for improving the pen-shaped fracture of steel wire rod for welding wire, comprising a molten steel smelting process, a LF refining process, a casting process, a heating process, a temperature-controlled rolling process and a slow cooling and heat preservation process. The chemical elements of the steel wire rod for welding wire suitable for the above-mentioned improvement method are as follows by mass percentage: C: 0.06-0.075%, Si: 0.81-0.87%, Mn: 1.41-1.47%, P≤0.023%, S: 0.008-0.015%, A1≤0.010%, Ca≤0.0010%, Ti≤0.10%, Cr≤0.10%, and the balance is Fe and unavoidable impurities.

[0025] Specifically, in the molten steel smelting process, the purpose is to add molten iron and scrap steel into a converter for smelting to obtain molten steel, and in the process of tapping, ferrosilicon-silicon manganese-lime are added to the molten steel in sequence, and ferrosilicon-silicon manganese is used for alloying, and at the same time, whether to add sulfur-containing slag to the molten steel is determined according to the S content in the molten steel; wherein, the scrap steel adopts high-quality steel, the scrap steel ratio is 10-15%, and the smelting end temperature is 1600-1650°C; and the element content of the molten steel at the smelting end point is C: 0.03-0.05%, O: 0.003%-0.015%, P≤0.015%, 0.010%≤S≤0.012%.

[0026] The purpose of controlling the above-mentioned C element content is to reduce the C content within a reasonable range and thus reduce the degree of influence caused by segregation. The purpose of controlling the O element content is to control the number of oxide inclusions generated so as to avoid excessive oxides in the steel billet, which may affect the stability of grain boundaries. However, P and S elements are harmful elements. S is easy to form FeS with a low melting point with Fe, which has hot brittleness, and too high S content is not conducive to subsequent welding, for example, it may cause cracks in the weld. However, on the other hand, a certain amount of S element can improve the hardness, strength and corrosion resistance of the weldment during welding, so the upper and lower limits of the S content are strictly controlled. However, the P element is easy to segregate and form FeP3 with Fe, which significantly reduces the plasticity and toughness, increases the brittleness, and especially the brittle transition temperature of steel increases sharply, causing the cold brittleness of steel. At the same time, it can deteriorate the welding performance of steel, reduce plasticity, and deteriorate the cold bending performance. Therefore, the P and S element contents in the present invention are controlled as follows: P≤0.023%, 0.010%≤S≤0.012%.

[0027] When 1 / 3 of the steel is tapped from the converter, ferrosilicon-silicon manganese-lime is added in the order, and ferrosilicon and silicon manganese are used for alloying, and all the alloy is added before the tapping is completed; when the S content in the molten steel is ≤0.010%, sulfur-containing slag and alloy are added in the order of sulfur-containing slag, ferrosilicon, and high-silicon silicon manganese, and the S content in the molten steel is controlled at 0.010-0.012%, and all the sulfur-containing slag and alloy are added before the tapping is completed, and the ladle bottom blowing and stirring are turned on throughout the tapping process. The ladle bottom blowing during the tapping process is 400-500L / min, and the obtained slag basicity CaO / SiO2=1.5-1.9, T.Fe+MnO content is 0.7-0.9%, and the bottom blowing flow rate is 90-150NL / min at the end of tapping.

[0028] In the LF refining process, due to the large amount of carbon increase during the steel-making process, one of the purposes of LF refining is to adjust the C content. First, slag adjustment is carried out: 2-4kg of lime, 1-1.5kg of ferrosilicon powder, and a small amount of silicon carbide diffusion deoxidation are added in batches per ton of steel, and the argon port is avoided to prevent carbon increase in the molten steel. In the later stage of refining, ferrosilicon powder is floated in small amounts and multiple times to maintain a reducing atmosphere. The basicity of the final slag is controlled at 1.5-1.9. Then adjust the composition: 10 minutes after the LF arrives at the station, the slag surface is clean and the molten steel temperature is ≥1540℃. Samples are taken, and the composition is adjusted in time according to the first sample. According to the last sample of refining, the sulfur line is fed into the internal control range, and soft blowing and stirring are carried out to remove inclusions. The time is not less than 15 minutes. Raw and auxiliary materials are prohibited from being added 8 minutes before steel-making.

[0029] Si is the alloy element that has the strongest effect in promoting graphitization. Whether in liquid or solid steel, Si combines with Fe more strongly than C. The presence of Si in molten steel will reduce the solubility of C. Therefore, the higher the Si content, the lower the C content, and more C will be squeezed out. The C content is reduced, and the C segregation of the ingot will be significantly improved. However, the Si content cannot be too high. Excessive Si will form SiO2 and high-content 2FeO-SiO2 silicate compounds. These spherical non-deformable inclusions will exist in the steel billet and affect the fatigue resistance. Therefore, in the present invention, the Si content in the steel billet is controlled to be 0.81-0.87%.

[0030] For the above-mentioned casting process, the molten steel produced in the above-mentioned LF refining process is subjected to protective casting, the superheat degree of the molten steel in the tundish of the open-casting furnace is 25-30°C, the superheat degree of the molten steel in the tundish of the continuous casting furnace is 15-20°C, the pulling speed is 2.39-2.43m / min when the specification of the ingot is 150*150mm, and the pulling speed is 1.58-1.62m / min when the specification is 180*180mm.

[0031] If the pulling speed of the continuous casting machine is too high, the residence time of the billet in the crystallization will be shortened, the solidification rate of the molten steel will be reduced, the liquid center of the billet will be extended, the liquid phase cavity will be deepened, the nucleation and growth of the equiaxed crystal will be delayed, the columnar crystal area will be expanded, and it will be easy to form bridges and small ingot structures, which will eventually lead to the deterioration of the central structure and shrinkage and axial segregation. If the pulling speed is too low, the amount of molten steel returned to the furnace may be too high, affecting efficiency and output. It has been found in practice that in the production of welding wire steel continuous casting, the pulling speed is 2.39~2.43m / min when the billet specification is 150*150mm, and the pulling speed is 1.58~1.62m / min when the specification is 180*180mm. When the pulling speed fluctuates within this range, a billet with excellent surface quality and internal quality can be formed, and the probability of the protective slag being involved is also extremely low.

[0032] In addition, if the casting temperature is high, the ingot is prone to produce columnar crystals or transgranular structures, resulting in loose center, shrinkage and segregation. The high casting temperature will also make the liquid core longer, causing the billet to bulge, and a cavity with negative pressure axial suction will be generated in the center of the billet, so that the molten steel enriched with solute elements at the end of solidification is sucked into the center of the billet, causing serious segregation. If the casting temperature is too low, it is easy to cause the water inlet of the tundish to freeze, forcing the casting to be interrupted, which is not conducive to the floating of inclusions in the steel and may deteriorate the quality of the billet. Therefore, in the present invention, during the casting process of the steel billet for welding wire, the superheat of the molten steel in the tundish of the open-casting furnace is 25-30°C, and the superheat of the molten steel in the tundish of the continuous casting furnace is 15-20°C. The lower limit of the superheat of the molten steel in the tundish can ensure smooth casting, and at the same time, the floating of inclusions in the steel is good. More importantly, when the molten steel enters the crystallizer at this temperature and the molten steel forms a crust, the unsolidified molten steel in the center of the continuous casting billet is close to the solidus temperature, which can provide a large number of equiaxed crystal nuclei, generate an equiaxed crystal network, organize the formation of columnar crystals, and expand the equiaxed crystal area in the center, which significantly reduces the degree of carbon segregation in the continuous casting billet.

[0033] In the present invention, the water flow rate of the continuous casting machine crystallizer is controlled at 120-130 L / min, the crystallizer liquid level fluctuation range is ±2-3 mm, the crystallizer electromagnetic stirring current is 280-300 A, and the frequency is 2.5 Hz. The molten steel is stirred by electromagnetic stirring, and the current and frequency of the electromagnetic stirring are controlled to promote the upward movement of inclusions and bubbles before the molten steel solidifies, reduce impurities inside the steel billet, and effectively interrupt the columnar crystals at the solidification front of the molten steel, so that they are mixed with the molten steel again and can serve as the core of equiaxed crystals; at the same time, the fluidity of the molten steel is increased, the heat transfer between the solidification phases is improved, the directional growth of the columnar crystals is inhibited, the generation of equiaxed crystals is promoted, and the dendrite segregation is reduced.

[0034] In the present invention, the height of the crystallizer electromagnetic stirrer is 800mm, and its center is located 500mm below the meniscus of the molten steel in the crystallizer. The vibration parameters of the continuous casting machine crystallizer are a vibration range of ±3.3mm and a vibration frequency of 92-99cpm. The electromagnetic stirring stirring position in the crystallizer is set to generate a suitable magnetic induction intensity at the meniscus position to promote the melting and uniform spreading of the protective slag, and to remove the inclusions captured at the front of the solidified dendrite by stirring, so as to promote the floating of the inclusions into the protective slag.

[0035] The water content of the secondary cooling zone of the continuous casting machine is 0.49~0.90L / kg, which is divided into 4 or 5 zones. When the water content is 0.9L / kg, the water distribution ratio of each zone is 40:39:10:7:4:; when the water content is 0.49L / kg, the water distribution ratio of each zone is 26:26:23:25.

[0036] The present invention controls the distribution ratio of each area of ​​the secondary cooling water, on the one hand, provides a reasonable cooling intensity, avoids the secondary water cooling being too weak, resulting in the surface temperature of the ingot being too high and the liquid core being elongated, although the growth of columnar crystals is suppressed and the equiaxed crystal area is increased, but the bulging deformation ability of the ingot shell caused by the static pressure of the molten steel is weakened, resulting in aggravated central segregation and expansion, and at the same time avoids the cooling being too strong, resulting in insufficient time for the elements in the molten steel to be selected and crystallized, which will aggravate the central shrinkage cavity. In addition, a reasonable strong cooling area is provided, the cooling area is extended, the cooling efficiency is maximized, the secondary dendrite spacing is effectively shortened, and the central segregation of elements is suppressed, which has a good effect.

[0037] Through the reasonable setting of various process parameters in casting, there are no horizontal and vertical cracks on the surface of the continuous casting billet, no defects such as shrinkage cavities, and the elements are evenly distributed. The size of inclusions within the range of 0 to 2 mm under the skin of the continuous casting billet is ≥30μm and the density is 0.01 to 0.03 pieces / mm 2 .

[0038] In the above-mentioned heating process, a regenerative blast furnace gas heating furnace is used for segmented heating, the preheating temperature is 700-800°C, the first heating temperature is 760-840°C, the second heating temperature is 890-970°C, and the soaking temperature is 1060-1090°C. By controlling the heating temperature and time, the continuous casting billet is austenitized more fully, the carbon in the steel is diffused more fully, and the surface decarburization caused by the billet staying in the high temperature section of the furnace for a long time is avoided, and the distribution is uniform, which reduces the carbon segregation in the steel.

[0039] In the temperature-controlled rolling process, the starting rolling temperature is set at 1000-1020°C, and the steel billet is successively subjected to rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling to form a wire rod. Specifically, the final rolling temperature is 950-970°C, and the wire is spun at 900-920°C. By controlling the starting rolling temperature of the welding wire steel, rolling at a lower temperature can avoid the abnormal organization caused by coarse austenite grains, reasonably controlling the dissolution of carbides in the steel at the lower limit of the final rolling temperature, and controlling the upper limit of the final rolling temperature to avoid the coarse austenite grains causing a decrease in cross-sectional shrinkage and plasticity. The control of the wire-spinning temperature is studied based on the Si and Mn content in the steel combined with the changes in the CCT image transformation curve. Wire-spinning within this temperature range can obtain iron oxide scale with good appearance and easy removal, avoid secondary oxidation caused by the shedding of iron oxide scale, and obtain the required uniform ferrite + pearlite wire rod structure.

[0040] In the slow cooling and heat preservation process, the present invention adopts a double-speed ratio reducer, and the wire rod obtained in the aforementioned temperature-controlled rolling process is placed on the Stelmor slow cooling line for slow cooling, and then sent to the heat preservation corridor for slow cooling, wherein the Stelmor slow cooling speed is ≤1°C / S, the temperature entering the heat preservation corridor is 730-770°C, the heat preservation time of the heat preservation corridor is 90-150min, and the temperature leaving the heat preservation corridor is ≤300°C. In addition, on the aforementioned Stelmor slow cooling line, the entrance roller speed is 0.152-0.168m / s, the exit roller speed is 0.237-0.262m / s, and the heat preservation covers are all closed during this period.

[0041] By controlling the slow cooling speed, it is ensured that no abnormal structure is produced in the wire rod. At the same time, the slow cooling speed of the inner and outer rings of the wire rod in the insulation corridor is consistent, so that the fine-grained austenite can be transformed and decomposed to obtain uniform ferrite and pearlite structures.

[0042] The present invention will be further described in detail below in conjunction with specific Examples 1 to 4 and Comparative Examples 1 to 3.

[0043] S1--Steel smelting

[0044] The smelting raw materials consisting of desulfurized molten iron and scrap steel are smelted in a 180t converter, wherein the mass percentage of S in each bag of molten iron is 0.002-0.006%. The total loading amount of the smelting raw materials, the weight percentage of molten iron in the smelting raw materials, the smelting time, the mass percentages of C, O, P, and S during steel tapping, and the steel tapping temperature of the above four embodiments and three comparative examples are shown in Table 1:

[0045] Table 1

[0046]

[0047] S2--LF refining

[0048] The molten steel obtained in the molten steel smelting process was refined in the LF furnace, wherein the refining time, slag adjustment time, soft stirring time, final slag basicity, and steel tapping temperature of the four embodiments and three comparative examples are shown in Table 2:

[0049] Table 2

[0050]

[0051] S3--Casting

[0052] The molten steel obtained from the refining process is cast with full protection, including long nozzle argon sealing + immersion nozzle protection casting. During casting, the casting billet is kept at a constant pulling speed, and the crystallizer electromagnetic stirring current is controlled to be 280-300A and the frequency is 2.5Hz. Among them, the superheat of the molten steel in the pouring furnace / continuous pouring furnace tundish, the specific water content, the secondary cooling water distribution ratio and the pulling speed of the billets of different specifications in the four embodiments and three comparative examples are shown in Table 3:

[0053] Table 3

[0054]

[0055]

[0056] S4--Heating

[0057] The obtained steel billet was heated under temperature control in a regenerative gas heating furnace. The preheating section temperature, the first heating section temperature, the second heating section temperature, the soaking section temperature, the holding time, and the maximum temperature difference between the head, the middle and the tail of the steel billet of the four embodiments and the three comparative examples are shown in Table 4:

[0058] Table 4

[0059]

[0060] S5--temperature controlled rolling

[0061] The steel billet obtained in the heating process is descaled by high-pressure water and then rolled into a wire rod. The starting rolling temperature, the final rolling temperature, and the wire laying temperature of the four embodiments and the three comparative examples are shown in Table 5.

[0062] Table 5

[0063]

[0064] S6--Slow cooling and heat preservation

[0065] The wire rod obtained in the temperature-controlled rolling process is kept warm and slowly cooled on the Stelmor slow cooling line, the insulation cover and the fan tuyere are all closed, and the cooling rate of the wire rod in the phase change temperature range is ≤1°C / s. In addition, the inlet roller speed and the outlet roller speed of the Stelmor slow cooling line of the four embodiments and three comparative examples are controlled as shown in Table 6. Among them, the cooling rate of the wire rod in the phase change temperature range can be calculated by testing the temperature between the insulation covers of the wire rod with an infrared thermometer.

[0066] Table 6

[0067]

[0068] Then, the wire rod after slow cooling on the Stettelmo line was sent to the insulation corridor for the second stage of insulation and slow cooling. The temperature entering the insulation corridor, the insulation time of the insulation corridor, and the temperature leaving the insulation corridor of the four embodiments and the three comparative examples are shown in Table 7:

[0069] Table 7

[0070]

[0071] In the present invention, according to the production methods corresponding to the above four embodiments and three comparative examples, the finally prepared steel wire rods for welding wire were inspected, wherein the chemical composition and weight percentage of each finished product are shown in Table 8:

[0072] The chemical composition of the steel billets used in the steel wire rods for welding wire corresponding to Examples 1-4 and Comparative Examples 1-3 is shown in Table 8:

[0073] Table 8: Composition of steel billets used in various embodiments and comparative examples (wt / %)

[0074] C Si Mn P S Al Cr Ca Ti Example 1 0.06 0.81 1.41 0.013 0.008 0.007 0.1 0.0010 0.1 Example 2 0.065 0.84 1.43 0.018 0.010 0.008 0.08 0.0009 0.09 Example 3 0.07 0.87 1.47 0.015 0.012 0.009 0.09 0.0008 0.09 Example 4 0.075 0.86 1.46 0.023 0.015 0.010 0.08 0.0007 0.08 Comparative Example 1 0.092 0.75 1.35 0.029 0.005 0.012 0.18 0.0020 0.18 Comparative Example 2 0.055 0.90 1.60 0.030 0.020 0.015 0.22 0.0015 0.16 Comparative Example 3 0.097 0.92 1.58 0.026 0.023 0.018 0.15 0.0038 0.20

[0075] At the same time, the wire rods prepared in the above embodiments and comparative examples were subjected to performance tests and drawn into welding wires to count the number of breaks per ton, analyze the proportion of pen-shaped breaks in the fracture types, and the spatter during welding. The test results are shown in Table 9.

[0076] Table 9 Performance test results

[0077]

[0078]

[0079] It can be seen from the above embodiments and comparative examples that the steel wire rod for welding wire in the embodiments of the present invention controls the C content in terms of chemical composition to achieve a low content within a range that does not affect other properties, thereby inhibiting C segregation from a key element perspective, controlling the O content to reduce the formation of inclusions, controlling the Ca, Ti and inclusion content and size to improve welding spatter, and controlling the S element content to ensure the quality of the welded parts.

[0080] The optimized process is simultaneously combined to finally produce wire rods with excellent mechanical properties, less inclusions, small shapes, and no abnormal structures. The wire rods are drawn into welding wires for welding with excellent welding properties and very few fractures during drawing.

[0081] In the comparative example, due to C segregation and high content and large inclusions, pen-point fractures and other fractures occurred many times during drawing, and there was also large spatter when the wire was drawn for welding.

[0082] In summary, the present invention controls the content of elements such as O, Si, C, S in the steel billet and controls the content by combining converter, LF refining, casting and other processes, thereby reducing the generation of oxide inclusions, brittle inclusions, and spherical non-deformed inclusions, and improving the fatigue resistance, corrosion resistance and drawing properties of the welding wire steel wire rod. On the other hand, by setting and optimizing process parameters, element segregation, especially central C segregation, is avoided, and finally a welding wire steel wire rod with uniform element distribution, no abnormal structure, few inclusions, excellent mechanical properties, and good drawing performance is obtained, which solves the problem of pen-shaped fractures in welding wire drawing.

[0083] 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 production method for improving the pen-shaped fracture of steel wire rod for welding wire, characterized in that: The steps include: S1: molten steel smelting, adding molten iron and scrap steel into a converter for smelting to obtain molten steel, and adding ferrosilicon-silicon manganese-lime to the molten steel in sequence during the steel tapping process; wherein the scrap steel ratio is 10-15%, and the steel tapping temperature is 1600-1650°C; S2: LF refining, lime, ferrosilicon powder and silicon carbide are added in batches for diffusion deoxidation per ton of steel, and the basicity of the final slag is controlled to be 1.5-1.9; after LF arrives at the station, samples are taken when the slag surface is clean and the molten steel temperature is ≥1540℃, and the composition is adjusted according to the sampling, and the sulfur line is fed according to the last sampling to make the S content meet the standard, and the soft blowing time is controlled to be not less than 15min; S3: Casting, the molten steel obtained in the refining step is subjected to protective casting, the superheat of the molten steel in the tundish of the open-casting furnace is 25-30°C, the superheat of the molten steel in the tundish of the continuous casting furnace is 15-20°C, when the specification of the ingot is 150*150mm, the pulling speed is 2.39-2.43m / min, when the specification of the ingot is 180*180mm, the pulling speed is 1.58-1.62m / min; S4: heating, heating the steel billet obtained in the casting process in sections, wherein the preheating section temperature is 700-800°C, the first section heating temperature is 760-840°C, the second section heating temperature is 890-970°C, and the soaking section temperature is 1060-1090°C. The temperature difference between the head, middle and tail of the steel billet in the heating furnace is controlled to be ≤30°C, wherein the temperature of the tail is 20-25°C higher than that of the head, and the temperature of the head is 5-10°C higher than that of the middle; S5: temperature-controlled rolling, rolling the steel billet obtained in the heating step into a wire rod, cooling it with water, and then spinning, wherein the starting rolling temperature is 1000-1020°C, the final rolling temperature is 950-970°C, and the spinning temperature is 900-920°C; S6: Slow cooling and heat preservation. The wire rod obtained in the temperature-controlled rolling process is placed on a Stelmor slow cooling line for slow cooling, and then sent into a heat preservation corridor for slow cooling. The Stelmor slow cooling rate is ≤1°C / S, the temperature entering the heat preservation corridor is 730-770°C, the heat preservation time in the heat preservation corridor is 90-150min, and the temperature exiting the heat preservation corridor is ≤300°C.

2. The production method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: The chemical elements of the applicable steel wire rod for welding wire are calculated in mass percentage as follows: C: 0.06-0.075%, Si: 0.81-0.87%, Mn: 1.41-1.47%, P≤0.023%, S: 0.008-0.015%, A1≤0.010%, Ca≤0.0010%, Ti≤0.10%, Cr≤0.10%, and the balance is Fe and unavoidable impurities.

3. The production method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: In step S1, before the molten iron is smelted, it is also necessary to perform KR desulfurization on the molten iron. The molten iron is taken every 4 minutes to analyze the S content. When the S content is between 0.002% and 0.006%, desulfurization is stopped and slag removal is performed. The slag removal rate is ≥95%. After KR desulfurization, the molten iron has a C of 3.8-4.2% and an S of 0.002-0.006%.

4. The production method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: In step S1, when the S content of the molten steel is 0.010-0.012%, it is not necessary to add the sulfur-containing slag; when the S content of the molten steel is ≤0.010%, the sulfur-containing slag is added before adding the ferrosilicon alloy to the molten steel.

5. The production method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: In step S1, the element contents of the molten steel at the end point of smelting are: C: 0.03-0.05%, O: 0.003-0.015%, P≤0.015%, S: 0.010-0.012%.

6. The production method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: In step S1, during the steel tapping process, the ladle bottom blowing and stirring are turned on throughout the whole process, the ladle bottom blowing flow rate is 400-500L / min, the obtained slag basicity CaO / SiO2=1.5-1.9, T.Fe+MnO content is 1-3%, and the bottom blowing flow rate at the end of steel tapping is 90-150NL / min.

7. The method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: In step S2, when the composition is adjusted according to the sampling, when the content of Si and Mn is adjusted, silicon-manganese alloy is used; when only the content of Si is adjusted, low-titanium and low-aluminum ferrosilicon is used.

8. The production method for improving the pen-shaped fracture of steel wire rod for welding wire according to claim 1, characterized in that: In step S6, on the Stelmor slow cooling line, the entrance roller speed is 0.152-0.168 m / s, and the exit roller speed is 0.237-0.262 m / s.

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