A hot-rolled wire rod and a production process for red rust control

Abstract

The present invention relates to a hot-rolled wire rod and a production process for red rust control. The contents of Ni and As are controlled in terms of composition to make the primary scale easy to remove. For wire rods with a Si content exceeding 0.2%, P and rare earth elements are added to reduce the melting point of the fayalite phase. By controlling the water pressure, water volume, and billet temperature of high-pressure water descaling, the primary scale is cleaned thoroughly. In the rolling process, a large reduction ratio is adopted in the early stage and a small reduction ratio in the later stage. By using low water temperature and high spinning temperature, the cooling water volume is reduced, and the cooling water volume of each water tank is reasonably distributed to control the temperature gradient of the wire rod and ensure the adhesion of the scale. The water pressure of the cooling water and the reverse air cleaning pressure are reasonably controlled, and the finishing rolling speed is appropriately reduced to reduce the reaction of the hot rolled piece, water, and air. At the same time, the water quality of the roll cooling water and the water tank cooling water is controlled. Finally, on the Stelmor cooling line, the oxidation of FeO is reduced on the basis of ensuring normal structure, so that the surface quality of the final product is good and no red rust is generated.

Description

Technical Field

[0001] The present invention relates to a hot-rolled wire rod and a production process for red rust control, belonging to the technical fields of iron and steel metallurgy and steel rolling. Background Art

[0002] With the increasingly fierce competition in the steel market, users' requirements for the surface quality of wire rod products are becoming stricter. During the high-temperature rolling and subsequent cooling processes of the wire rod, chemical reactions occur when the surface contacts with air, generating scale. The scale is composed of FeO, Fe2O3, and Fe3O4 in a certain proportion, usually gray or bluish-gray. However, under certain conditions, when the proportion of Fe2O3 is relatively high, the scale on the surface of the wire rod is red, which is usually called the red rust on the surface of the wire rod.

[0003] The red rust on the surface of the wire rod will have an adverse impact on the quality of the finished wire rod: First, it causes the appearance quality of the product to deteriorate and affects the product image. Second, the red rust on the surface will have an adverse impact on mechanical descaling or acid pickling descaling in the subsequent processing, resulting in difficult descaling or an increase in acid consumption during acid pickling, leading to wire breakage during drawing, an increase in the consumption of drawing dies, and even having varying degrees of impact on the fatigue performance of the steel wire.

[0004] In order to control red rust to ensure good quality of the finished product surface, an application with publication number CN109355453A discloses a production method for red rust on the surface of hot-rolled strip steel. By controlling the Si content in the molten steel to be 0.159 - 0.185%, and controlling key parameters such as the conductivity, pH value, and reverse air purge pressure of the cooling water, the problem of easy generation of red rust in wire rod production is solved. However, for high-strength steel wire rods, it is necessary to add more than 0.2% of Si element to play the roles of solution strengthening, improving the hardenability of austenite, and improving the purity of ferrite. In terms of composition, the existing technology controls the Si content in the steel below 0.2%. However, for Si elements above 0.2%, no method for controlling red rust is given. An application with publication number CN115922155A discloses a production method for removing red rust on the surface of wire rod steel. It uses low-temperature heating, controls the rolling temperature, adopts a fast roller path process in the air-cooling line to increase the loop density, and rapidly cools to improve the problem of red rust on the surface of finished low-carbon steel wire rods. However, for some steel grades, using low-temperature heating with too low heating temperature is likely to cause incomplete penetration of the steel billet and uneven temperature of the steel billet, ultimately resulting in unqualified properties of the wire rod. On the one hand, low-temperature rolling is likely to cause cracks and fractures in the scale, leading to rapid oxygen diffusion, and FeO is continuously oxidized to Fe2O3 and Fe3O4, resulting in serious red rust on the surface of the wire rod. On the other hand, low-temperature rolling is limited by the production line equipment, and some production line equipment cannot achieve low-temperature rolling. An application with publication number CN107962070A discloses a rolling process for eliminating red rust on the surface of high-speed wire rods. By controlling the grease content in the turbidity circulating water, adjusting the entry temperature of the finishing mill and the spinning temperature, and increasing the reverse purge pressure, etc., the red rust on the surface of high-speed wire rods is controlled at a low level, and the oil and gas injection amount is reduced, the oil and gas consumption is reduced, and the cost is reduced, achieving good surface quality of high-speed wire rods under the condition of oil and gas lubrication. However, in addition to the grease content in the turbidity circulating water affecting red rust, the chloride ion content, pH value, conductivity, etc. will also affect red rust.

[0005] The mechanism of red rust generation is relatively complex, involving high-temperature oxidation corrosion, high-temperature electrochemical corrosion, etc. Therefore, in the rolling process, multiple factors need to be considered, such as reasonably designing the composition, optimizing the rolling process parameters, and controlling the quality of the cooling water, etc., to make the surface quality of the final wire rod good and no red rust is generated. Summary of the Invention

[0006] The present invention provides a hot-rolled wire rod and a production process for red rust control, which are controlled in terms of composition and the whole rolling process, so that the surface quality of the final product is good and no red rust is generated.

[0007] The technical solution adopted by the present invention to solve its technical problems is:

[0008] A hot-rolled wire rod, the chemical composition of the wire rod is determined according to the Si content, in terms of mass percentage,

[0009] When 0.06% ≤ Si < 0.2%, C is 0.06 - 0.82%, Mn is 0.3 - 0.6%, P ≤ 0.02%, S ≤ 0.015%, Ni ≤ 0.014%, As ≤ 0.015%, Ni + As ≤ 0.02%, and the rest is Fe and inevitable impurities;

[0010] When 0.2% ≤ Si ≤ 0.3%, C is 0.25 - 0.82%, Mn is 0.3 - 0.6%, P is 0.05% - 0.06%, S ≤ 0.015%, Ni ≤ 0.014%, As ≤ 0.015%, Ni + As ≤ 0.02%, REM is 0.02 - 0.03%, and the rest is Fe and inevitable impurities, where REM is one or two or three of the rare earth elements Ce, Sc, and Y;

[0011] For the red rust control production process of the hot-rolled wire rod, it specifically includes the following steps:

[0012] Step S1, heating the steel billet. Feed the steel billet into the heating furnace, adopt segmented heating, and set different stage temperatures according to different silicon contents until the steel billet is heated to the preset temperature that meets rolling.

[0013] Step S2, descaling with high-pressure water. On each of the four sides of the spraying beam, three nozzles are installed on each side. Set the water pressure of the nozzle located in the middle position to be 18 - 20 MPa, and the water pressure of the other two nozzles to be 15 - 17 MPa. The inclination angle range between the nozzle central axis and the steel billet normal line is 15 - 18°, and the linear distance between the nozzle and the steel billet surface is 150 - 160 mm. Use the nozzles to spray high-pressure water onto the steel billet surface to peel off and wash away the scale.

[0014] Step S3, rough rolling. Use the rolls of the rough rolling mill to roll the steel billet in multiple passes, subjecting the steel billet to large deformation rolling, where the elongation coefficient of each pass is set to be 1.4 - 1.5.

[0015] Step S4, medium rolling. Roll the steel billet in multiple passes on the medium rolling mill to reduce the cross-sectional size of the steel after rough rolling, where the elongation coefficient of each pass is set to be 1.4 - 1.5.

[0016] Step S5, continue to roll the steel billet. After pre-finishing rolling, set up two water tanks, spray water on the wire rod for cooling. Set the water pressure of the water tanks to be 3 - 5 Mpa, the water volume of each water tank to be 200 - 300 L / min, the water pressure of the roll cooling water to be 5.5 - 7 bar, and the water volume to be 500 - 700 L / min.

[0017] Step S6, finish rolling. Continuously roll the wire rod on the finish rolling mill, and set the elongation coefficient of each pass of finish rolling to be 1.2 - 1.25.

[0018] In step S7, after finish rolling, water cooling is carried out. Six water tanks are set, and three of them are turned on. The water volume of each water tank is set to 600 - 800 L / min, the water pressure of the roll cooling water is 3.5 - 6 bar, and the reverse air cleaning pressure is 4 - 7 bar;

[0019] In step S8, wire laying is carried out;

[0020] In step S9, Stelmor air cooling is carried out, and the cooling speed is set according to the different carbon contents and different temperature ranges of the wire rod;

[0021] In step S10, coiling is carried out, and the air-cooled wire rod is collected into coils;

[0022] In step S11, packing is carried out, and the wire rod coils are bundled and fixed using packaging materials;

[0023] Furthermore, in step S1, when 0.06% ≤ Si < 0.2%, the preheating section temperature of the heating furnace is set to 800 - 900 °C, the heating section temperature is set to 880 - 980 °C, and the soaking section temperature is set to 1040 - 1140 °C;

[0024] When 0.2% ≤ Si ≤ 0.3%, the preheating section temperature of the heating furnace is set to 910 - 960 °C, the heating section temperature is set to 1060 - 1100 °C, and the soaking section temperature is set to 1130 - 1170 °C;

[0025] The heating time of the steel billet in the heating furnace lasts for 90 - 100 min. The preheating section and soaking section of the heating furnace are maintained in a reducing atmosphere, and the heating section is maintained in an oxidizing atmosphere. The through-strip temperature difference of the steel billet is controlled ≤ 30 °C;

[0026] Furthermore, in step S3, the water pressure of the roll cooling water for rough rolling is set to 6 - 8 bar, and the water volume is 1200 - 1500 L / min;

[0027] In step S4, the water pressure of the roll cooling water for medium rolling is set to 6 - 8 bar, and the water volume is 1200 - 1500 L / min;

[0028] In step S6, the water pressure of the roll cooling water for finish rolling is set to 5.5 - 7 bar, the water volume is 500 - 700 L / min, and the final rolling speed ≥ 105 m / s;

[0029] Furthermore, in steps S3 - S7, the specific settings of each index in the water quality of the cooling water are as follows: chloride ion ≤ 100 mg / L, calcium and magnesium ions ≤ 250 mg / L, dissolved oxygen ≤ 0.2 mg / L, conductivity ≤ 1000 us / cm, pH value range is 7.0 - 8.0, suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, grease ≤ 0.3 mg / L, total iron ≤ 1.0 mg / L, total phosphorus ≤ 0.5 mg / L, and water temperature is 15 - 25 °C;

[0030] Further, the water quality in the water tank and the water quality of the roll cooling water are optimized respectively. Among them, the indexes of the water quality in the water tank are set as follows: chloride ion ≤ 70 mg / L, calcium and magnesium ions ≤ 250 mg / L, dissolved oxygen ≤ 0.1 mg / L, conductivity ≤ 900 us / cm, pH value range is 7.0 - 8.0, suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, grease ≤ 0.3 mg / L, total iron ≤ 0.8 mg / L, total phosphorus ≤ 0.5 mg / L, water temperature is 15 - 20 °C;

[0031] The indexes of the roll cooling water quality are set as follows: chloride ion ≤ 80 mg / L, calcium and magnesium ions ≤ 200 mg / L, conductivity ≤ 800 us / cm, pH value range is 7.0 - 7.5, suspended solids ≤ 4 mg / L, turbidity ≤ 4 NTU, grease ≤ 0.1 mg / L, total phosphorus ≤ 0.3 mg / L, water temperature is 20 - 25 °C;

[0032] Further, in step S7, the six water tanks set are numbered in sequence as No. 1 water tank, No. 2 water tank... No. 6 water tank, and the three opened water tanks are No. 1 water tank, No. 3 water tank and No. 5 water tank respectively;

[0033] Further, in step S8, the setting range of the wire laying temperature is 880 - 940 °C;

[0034] Further, in step S9, when the wire rod temperature range is 450 - 600 °C, the cooling rate of air cooling is set to 3.5 - 5.5 °C / s;

[0035] When the wire rod temperature > 600 °C, the cooling rate of the steel with a carbon content of 0.06% - 0.25% is set to 1.5 - 2.5 °C / s, the cooling rate of the steel with a carbon content of 0.25% - 0.6% is set to 4 - 9 °C / s, and the cooling rate of the steel with a carbon content of 0.6% - 0.82% is set to 11 - 15 °C / s.

[0036] Through the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. For the hot-rolled wire rod provided by the present invention, the contents of Ni and As are strictly controlled in terms of composition, reducing the enrichment of the two at the interface between the oxide layer and the matrix, making the primary scale easy to remove;

[0038] 2. For the hot-rolled wire rod provided by the present invention, considering the working conditions when the Si content is greater than 0.2%, P element is added in the composition to reduce the melting temperature of fayalite and reduce the adhesion of the scale. By controlling the water pressure, water volume and billet temperature of high-pressure water descaling, the primary scale is removed cleanly. At the same time, rare earth elements are added to inhibit the segregation of P element at the grain boundary and avoid cold brittleness of the steel;

[0039] 3. The red rust control production process provided by the present invention adopts a large reduction ratio in the early stage and a small reduction ratio in the later stage during the rolling process to avoid the rupture and oxidation of the oxide scale. By adopting a low water temperature and a high wire-spinning temperature, the cooling water volume is reduced, and the cooling water volume of each water tank is reasonably distributed to control the temperature gradient of the wire rod and ensure the adhesion of the mill scale;

[0040] 4. The red rust control production process provided by the present invention reasonably controls the cooling water pressure and the reverse air cleaning pressure, appropriately reduces the finishing rolling speed, and reduces the reaction of hot rolled pieces, water and air at high temperature; at the same time, strictly controls the water quality of the roll cooling water and the water tank cooling water to avoid accelerating corrosion and causing red rust. Finally, on the basis of ensuring normal structure on the Stelmor cooling line, the oxidation of FeO is reduced, so that the surface quality of the final product is good and no red rust is generated. Brief Description of the Drawings

[0041] The present invention will be further described below with reference to the drawings and embodiments.

[0042] Figure 1 is the wire rod produced according to the embodiment provided by the present invention;

[0043] Figure 2 is the wire rod produced according to the comparative example provided by the present invention. Detailed Embodiments

[0044] The present invention will now be further described in detail with reference to the drawings.

[0045] The mechanism of red rust generation is relatively complex. Substantially, it is a diffusion process of the formation of the oxide layer on the surface of the wire rod. Fe diffuses outward from the matrix, and O diffuses inward from the outside. When Fe reacts with O attached to the surface of the matrix to form FeO, FeO is further oxidized to form Fe3O4, and Fe3O4 continues to be oxidized to form Fe2O3; steel materials will undergo oxidation reactions with both O2 and H2O. When steel materials coexist with air and water at high temperatures, reactions will occur to form Fe2O3. Therefore, if red rust generation is to be avoided, it is actually necessary to reduce the generation amount of Fe2O3.

[0046] In order to solve the above problems, this application considers various factors, reasonably designs the composition, optimizes the rolling process parameters, controls the water quality of the cooling water, etc., so that the surface quality of the final wire rod is good and no red rust is generated.

[0047] As described in the background art, the prior art does not give a method for controlling red rust when the Si element content is above 0.2%. Therefore, the chemical composition of the hot rolled wire rod provided by this application is designed differently according to different Si contents, in mass percentage,

[0048] When 0.06% ≤ Si < 0.2%, C is 0.06 - 0.82%, Mn is 0.3 - 0.6%, P ≤ 0.02%, S ≤ 0.015%, Ni ≤ 0.014%, As ≤ 0.015%, Ni + As ≤ 0.02%, and the balance is Fe and inevitable impurities. When 0.2% ≤ Si ≤ 0.3%, C is 0.25 - 0.82%, Mn is 0.3 - 0.6%, P is 0.05% - 0.06%, S ≤ 0.015%, Ni ≤ 0.014%, As ≤ 0.015%, Ni + As ≤ 0.02%, REM is 0.02 - 0.03%, and the balance is Fe and inevitable impurities, where REM is one or two or three of rare earth elements Ce, Sc, and Y.

[0049] The innovative design in the above components is first to control the contents of Ni and As. As residual elements in the wire rod, during the cooling process or the secondary heating process, due to selective oxidation, Ni and As elements are mainly enriched between the oxide layer and the matrix, making it difficult to remove the oxide layer. During the rolling process, the scale enters the workpiece, resulting in surface defects or roll wear, and eventually prone to the generation of red rust. Another reason is that the market demand for green and low-carbon electric furnace steel products is increasing. Therefore, the contents of residual elements such as Ni and As in the steel increase with the increase of the scrap ratio. Ni and As elements are mainly enriched between the oxide layer and the matrix, also making it difficult to remove the FeO layer. Therefore, in the component design, the contents of these two elements are controlled as Ni ≤ 0.014%, As ≤ 0.015%, and Ni + As ≤ 0.02%.

[0050] Secondly, for wire rods with Si content above 0.2%, as an important solid solution strengthening element in steel, Si can improve the strength of ferrite. It is also an important deoxidizer, which helps reduce the oxygen content in steel and decrease inclusions. At the same time, Si has the effect of inhibiting the formation of network cementite. When the Si content in steel is ≥ 0.2%, during high-temperature heating, Si is prone to diffuse to the interface between FeO and the steel surface and form a molten liquefied film composed of FeO and Fe2SiO4. When the billet temperature drops below 1173 °C, this liquefied film will undergo a eutectic reaction to generate fayalite (Fe2SiO4), which forms an anchor-like morphology after solidification, pinning the FeO layer and increasing the adhesion of the scale. The pinned FeO is difficult to be completely removed during descaling, and the residual FeO causes the formation of Fe2O3, resulting in an increase in the proportion of Fe2O3 after oxidation and the generation of red rust. Therefore, P element is added in the composition design of this application. Generally, P is a harmful element in steel, which will increase the cold brittleness of steel. However, P will form Fe3(PO4)2 or P2O5 on the metal surface. The presence of the Fe3(PO4)2 phase can lower the melting temperature of the Fe2SiO4 phase. When the descaling temperature is higher than the melting temperature of the Fe2SiO4 phase, the Fe2SiO4 phase is in a liquid state, and the liquid-phase Fe2SiO4 separates and destroys the adhesion of the scale, making it very easy to remove. And both Fe3(PO4)2 and P2O5 will decompose or vaporize above 950 °C. Therefore, when the Si content in steel is 0.06% - 0.2%, the P content is controlled at P ≤ 0.02%, and when 0.2% ≤ Si ≤ 0.3%, the P element is controlled at 0.05 - 0.06%.

[0051] Compared with the P content added in the traditional process, the content added in this application is slightly higher. Considering the possible segregation problem, in the composition design with Si content ≥ 0.2%, rare earth elements (REM) are added. Rare earth elements can inhibit the segregation of P element at the grain boundary, strengthen the grain boundary, and improve the strength and toughness of the wire rod. It can be used as the nucleation point of pearlite phase transformation, increasing the nucleation number and refining the pearlite lamellar spacing. At the same time, rare earth elements can deform the oxides and sulfides in the molten steel to generate small, nearly spherical rare earth compounds, improving the drawing performance and corrosion resistance. However, if the content of rare earth elements is too high, the number of inclusions will increase and the generated composite compounds will aggregate into larger particles, forming string-like inclusions after rolling, deteriorating the performance of the wire rod. The rare earth content in this application is controlled at 0.02 - 0.03%.

[0052] As for other component designs, for example, carbon is the most basic strengthening element in steel. As the C content increases, the strength and hardness of the steel increase, while the toughness decreases. Therefore, the C content is designed to be 0.06 - 0.82%. Manganese plays a role in solid solution strengthening and fine grain strengthening in steel. It can stabilize austenite, enhance hardenability, improve the strength and low-temperature toughness of the steel, and is beneficial to reducing the brittle-ductile transition temperature of the steel. Therefore, the Mn content is designed to be 0.3 - 0.6%. Sulfur is a harmful impurity element, and the lower the content, the better. Therefore, the S content in the wire rod is controlled to be ≤0.015%.

[0053] In addition to designing the chemical composition of the wire rod, corresponding designs also need to be carried out for the entire rolling process. There are several stages in the wire rod production process where scale is likely to be generated. In the heating furnace, the surface of the steel billet comes into contact with the high-temperature furnace gas and undergoes an oxidation reaction to form primary scale. During the rolling process, especially in the rough rolling stage, the scale on the surface of the steel billet may be broken or peeled off by the roll, and at the same time, new scale will continue to form. The scale generated in this process becomes secondary scale. In the finish rolling process, due to the relatively high rolling temperature and large deformation, the formation rate of scale is relatively fast. The scale in this process is tertiary scale. After coiling, quaternary scale will be formed. Therefore, the entire rolling process needs to be controlled to avoid the generation of red rust.

[0054] The red rust control production process provided for the hot-rolled wire rod specifically includes the following steps:

[0055] Step S1, heating the steel billet. The steel billet is sent into the heating furnace, and the heating time of the steel billet in the heating furnace lasts for 90 - 100 min. The entire heating process uses sectional heating. In the preheating section, a reducing atmosphere is used, and the temperature is slowly increased to reduce the thermal stress on the surface and core and inhibit the further formation of scale. In the heating section, the temperature is rapidly increased to reduce the oxidation of the steel billet surface. In the soaking section, the temperature of the steel is relatively high, and a reducing atmosphere is used to avoid further oxidation. At the same time, the through-strip temperature difference of the steel billet is controlled so that the temperature difference of the steel billet is controlled within 30°C. If the heating temperature is uneven and the through-strip temperature difference is large, the scale at the high-temperature part is thick and dense, while the scale at the low-temperature part is thin and easy to fall off, which cannot protect the matrix. When the through-strip temperature difference of the wire rod exceeds 60°C, red rust can clearly be seen on the surface of the wire rod.

[0056] When carrying out sectional heating, different-stage temperatures are also set according to different silicon contents. This is because when 0.06% ≤ Si < 0.2%, low-temperature heating is used in the steel billet heating process to make the heating temperature below the melting point of the fayalite phase, avoiding the melting of fayalite and the solidification and pinning of the FeO layer, making it difficult to remove the primary scale completely during the descaling process. When 0.2% ≤ Si ≤ 0.3%, high-temperature heating is used in the steel billet heating process to make the heating temperature above the melting point of the fayalite phase. Subsequently, during the high-pressure water descaling process, the temperature of the steel billet is controlled above the melting point of fayalite, and it is removed using high-pressure water descaling.

[0057] Specifically, when 0.06% ≤ Si < 0.2%, the preheating section temperature of the heating furnace is set at 800 - 900 °C, the heating section temperature is set at 880 - 980 °C, and the soaking section temperature is set at 1040 - 1140 °C; when 0.2% ≤ Si ≤ 0.3%, the preheating section temperature of the heating furnace is set at 910 - 960 °C, the heating section temperature is set at 1060 - 1100 °C, and the soaking section temperature is set at 1130 - 1170 °C.

[0058] Step S2: High-pressure water descaling. High-pressure water is sprayed onto the surface of the billet using nozzles to peel off and wash away the scale. Considering that when 0.06% ≤ Si < 0.2%, the surface temperature of the billet is 1030 - 1130 °C and the corner temperature is 1020 - 1120 °C; when 0.2% ≤ Si ≤ 0.3%, the surface temperature of the billet ≥ 1120 °C and the corner temperature ≥ 1110 °C. Especially when the Si content is greater than 0.2%, by adding element P, the melting temperature of fayalite is reduced. When the descaling temperature is higher than the melting temperature of the Fe2SiO4 phase, the Fe2SiO4 phase is in a liquid state and is removed using high-pressure water. Since the temperature drop at the corners of the billet is large, parameters such as the nozzle pressure, angle, and distance during high-pressure water descaling are controlled to keep the surface temperature and corner temperature of the billet above the melting temperature of the Fe2SiO4 phase and ensure that the scale is completely removed to avoid the residue of FeO and the generation of red rust.

[0059] Regarding parameters such as the nozzle pressure, angle, and distance, specifically, three nozzles are installed on each of the four sides of the spray beam. The water pressure of the nozzle located in the middle position is set at 18 - 20 MPa, and the water pressure of the other two nozzles is set at 15 - 17 MPa. The inclination range between the nozzle axis and the normal of the billet is 15 - 18°, and the linear distance between the nozzle and the surface of the billet is 150 - 160 mm.

[0060] Step S3: Rough rolling. The billet is rolled in multiple passes using the rolls of the rough rolling mill to subject the billet to large deformation. Among them, the elongation coefficient for each pass is set at 1.4 - 1.5; Step S4: Medium rolling. The billet is rolled in multiple passes on the medium rolling mill to reduce the cross-sectional size of the steel after rough rolling. Among them, the elongation coefficient for each pass is set at 1.4 - 1.5. During the rough rolling and medium rolling stages, the water pressure of the roll cooling water is set at 6 - 8 bar, and the water volume is 1200 - 1500 L / min.

[0061] Step S5: Continue to roll the billet. After pre-finishing rolling, two water tanks are set up to spray water on the wire rod for cooling. The water pressure of the water tanks is set at 3 - 5 Mpa, the water volume of each water tank is 200 - 300 L / min, the water pressure of the roll cooling water is 5.5 - 7 bar, and the water volume is 500 - 700 L / min;

[0062] Step S6, finish rolling. Continuously roll the wire rod on the finish rolling mill. Set the elongation coefficient for each pass of finish rolling to be 1.2 - 1.25, the final rolling speed ≥ 105 m / s, the water pressure of the roll cooling water to be 5.5 - 7 bar, and the water volume to be 500 - 700 L / min.

[0063] The design means for controlling the rolling process to avoid the generation of red rust in Steps S3 - S6 are mainly described from the following parts. Since the plastic deformation abilities of the oxide scale and the substrate are different, large reduction ratios can be used in rough rolling and intermediate rolling to uniformly deform the iron oxide scale, making it thinner and enhancing its adhesion to the substrate, so that cracks or peeling are not likely to occur and it will not peel off and be pressed into the substrate to cause defects. Small reduction ratios are used in finish rolling to reduce the deformation amount of the oxide scale and avoid the rupture of the oxide scale. Because the finish rolling temperature is lower than the rough rolling temperature, the plasticity of the FeO component in the iron oxide scale decreases at low temperatures. If a large reduction ratio is used in finish rolling, it is easy to cause the rupture of the oxide scale, increasing the contact area with air, thus greatly accelerating the reaction of FeO → Fe3O4 → Fe2O3 and increasing the generation amount of Fe2O3, resulting in red rust on the surface of the final wire rod. In the finish rolling process, low water temperature and high spinning temperature can be used to reduce the water volume in the water tank after finish rolling and evenly distribute the water volume in the water tank, avoiding too large a temperature gradient of the wire rod during water cooling, ensuring the adhesion of the iron oxide scale on the surface of the substrate, and making the surface temperature of the wire rod uniform in the recovery section. If the cooling rate of the previous water tank is too fast, the surface temperature of the oxide scale will be greatly reduced and it will be easy to peel off, accelerating the oxidation reaction in the oxygen-rich environment of the recovery section or the next water tank and easily generating red rust.

[0064] Step S7, water cooling after finish rolling. Set six water tanks and turn on three of them. Number the six set water tanks in sequence as No. 1 water tank, No. 2 water tank... No. 6 water tank. The three turned-on water tanks are No. 1 water tank, No. 3 water tank, and No. 5 water tank to ensure that the water volume can be evenly distributed. Set the water volume of each water tank to be 600 - 800 L / min, the water pressure of the roll cooling water to be 3.5 - 6 bar, and the reverse air cleaning pressure to be 4 - 7 bar. Appropriately increase the final rolling speed. The lower the final rolling speed, the longer the coexistence time of the hot rolled piece, water, and air, which means the longer the reaction time for Fe, O2, and H2O to generate Fe2O3, and the more obvious the red floating rust on the surface of the wire rod.

[0065] Cooling water is involved in the rolling process of Steps S3 - S7. Here, the optimization of the control of each index in the cooling water quality is first given, that is, set the chloride ion ≤ 100 mg / L, calcium and magnesium ions ≤ 250 mg / L, dissolved oxygen ≤ 0.2 mg / L, conductivity ≤ 1000 us / cm, pH value range 7.0 - 8.0, suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, grease ≤ 0.3 mg / L, total iron ≤ 1.0 mg / L, total phosphorus ≤ 0.5 mg / L, and water temperature 15 - 25 °C.

[0066] Next, a specific explanation is made for the above component designs. The higher the chloride ion content in the cooling water, the more severe the corrosion of the steel. This is because chloride ions can attack the surface of the steel, promote the corrosion reaction, and have strong penetrability, easily penetrating the protective film on the metal surface and causing corrosion. High temperature causes the moisture on the surface of the steel billet to evaporate instantaneously. After the chlorinated electrolyte in the cooling water crystallizes, it adheres to the surface of the specimen. After the wire rod cools, the humid air makes the surface of the wire rod wet, and the chlorinated electrolyte dissolves, forming an electrolyte solution with a very high chloride ion content on the surface of the steel billet, and rust gradually appears on the surface of the steel plate. Therefore, in this application, the chloride ions need to be controlled at ≤100 mg / L. When the concentrations of calcium and magnesium ions are too high, they will combine with CO3 2- 、SO4 2- silicate radicals, etc. to form scale and deposit on the metal surface, destroying the integrity and compactness of the passivation film and providing a pitting corrosion source for the corrosion of other inorganic ions. Therefore, in this application, the calcium and magnesium ions need to be controlled at ≤250 mg / L. Dissolved oxygen content Since oxygen is a depolarizer, generally speaking, the more oxygen in the water, the more severe the corrosion of steel. Therefore, in this application, the dissolved oxygen needs to be controlled at ≤0.2 mg / L. The conductivity of the cooling water directly affects the corrosion rate of the steel. Cooling water with a high conductivity means that there are more ions in the water. These ions play a role in conducting electricity during the electrochemical corrosion process and accelerate the corrosion of the steel. Specifically, cooling water with a high conductivity contains more chloride ions, making the steel more vulnerable to corrosion. Therefore, in this application, the conductivity needs to be controlled at ≤1000 us / cm. The smaller the pH value of the cooling water, the stronger the acidity, and the faster the corrosion of the metal. In a weakly alkaline solution, under the condition of the same chloride ion concentration, the intervention of OH - makes OH - and Cl - compete for adsorption on the material surface, inhibiting Cl -Erosion of the material surface. Therefore, keeping the pH value of the cooling water weakly alkaline can effectively alleviate the corrosion of the steel plate surface, and the pH value needs to be controlled within 7.0 - 8.0. High levels of suspended solids, impurities, and oil content in the cooling water will reduce the thermal conductivity of the cooling water, hinder heat transfer, reduce the cooling capacity, promote the formation of a steam film on the surface of the wire rod, accelerate the reaction between the metal on the wire rod surface and the steam, and thus promote the formation of red rust on the wire rod surface. Therefore, in this application, the water quality of the cooling water needs to be controlled such that the suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, and oil ≤ 0.3 mg / L. The total iron content in the steel mill cooling water has a significant impact on the corrosion of the wire rod. Iron ions are a kind of fouling substance in water. High concentrations of total iron will promote the growth of iron bacteria, form microbial corrosion, and at the same time cause galvanic corrosion, accelerating the corrosion rate. High concentrations of total iron will promote the corrosion process, cause damage to pipelines and equipment, and reduce the equipment life. When the total phosphorus content is too high, it will not only cause eutrophication of the water body, but also easily lead to the accumulation of scale, thereby reducing the cooling efficiency. Therefore, in this application, the water quality of the cooling water needs to be controlled such that the total iron ≤ 1.0 mg / L and the total phosphorus ≤ 0.5 mg / L.

[0067] Furthermore, both the rolling mill rolls and the water tank are related to the cooling water. Among them, the cooling water for the rolling mill rolls is used to cool the roll rings by spraying cooling water during the steel billet rolling process. Reasonable control of parameters such as the water pressure, water volume, water temperature, and water quality of the rolling mill roll cooling water is required. If the water pressure and water volume are too large, it is easy for the water to splash out from the roll surface, and the actual water volume of the cooling water is insufficient, while causing waste at the same time. If the water pressure is too low, the cooling effect on the roll surface is not good, and it is easy to cause cracks on the rolling mill roll surface, resulting in the cracking of the roll rings. Due to the presence of rolling mill roll lubricant, it is necessary to strictly control the oil, suspended solids, turbidity, etc. in the cooling water to avoid insufficient cooling capacity of the cooling water. At the same time, strictly control indicators such as chloride ions, calcium and magnesium ions, conductivity, and total phosphorus content to prevent the cooling water from impacting the rolling mill rolls for a long time, causing corrosion to the rolling mill rolls, scaling on the heat transfer surface, affecting the heat exchange effect, and increasing the surface roughness of the billet, promoting the generation of subsequent red rust. Therefore, the various indicators of the water quality of the rolling mill roll cooling water are set as follows: chloride ions ≤ 80 mg / L, calcium and magnesium ions ≤ 200 mg / L, conductivity ≤ 800 us / cm, pH value range is 7.0 - 7.5, suspended solids ≤ 4 mg / L, turbidity ≤ 4 NTU, oil ≤ 0.1 mg / L, total phosphorus ≤ 0.3 mg / L, and water temperature is 20 - 25 °C.

[0068] The cooling water in the water tank cools the wire rod to reach the set spinning temperature. Similarly, the water quality of the cooling water in the water tank is optimized to improve the cooling capacity and reduce the corrosion reaction rate. By separately controlling the rolling mill and the cooling water in the water tank, the generation of red rust is effectively reduced. Therefore, the indicators of the water quality in the water tank are set as follows: chloride ion ≤ 70 mg / L, calcium and magnesium ions ≤ 250 mg / L, dissolved oxygen ≤ 0.1 mg / L, conductivity ≤ 900 us / cm, pH value range is 7.0 - 8.0, suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, grease ≤ 0.3 mg / L, total iron ≤ 0.8 mg / L, total phosphorus ≤ 0.5 mg / L, and water temperature is 15 - 20 °C.

[0069] Step S8, spinning, set the spinning temperature range to 880 - 940 °C.

[0070] Step S9, Stelmor air cooling, set the cooling rate according to different carbon contents and different temperature ranges of the wire rod; when the wire rod temperature range is 450 - 600 °C, set the air cooling rate to 3.5 - 5.5 °C / s; when the wire rod temperature > 600 °C, for steel with a carbon content of 0.06% - 0.25%, set the cooling rate to 1.5 - 2.5 °C / s, for steel with a carbon content of 0.25% - 0.6%, set the cooling rate to 4 - 9 °C / s, and for steel with a carbon content of 0.6% - 0.82%, set the cooling rate to 11 - 15 °C / s.

[0071] Adopt an appropriate cooling rate above 600 °C to ensure the normal structure of the wire rod and avoid the appearance of abnormal structures. Accelerate the cooling rate at 450 - 600 °C to avoid the decomposition of FeO and the generation of red rust.

[0072] Step S10, coiling, collect the air-cooled wire rod into coils.

[0073] Step S11, packing, use packaging materials to bundle and fix the wire rod coils.

[0074] The final wire rod specification is 5.5 - 7 mm.

[0075] Examples and comparative examples

[0076] To verify the feasibility and superiority of the hot-rolled wire rod and red rust control production process provided by this application, this application provides examples and comparative examples. The examples take the silicon element in the wire rod exceeding 0.2% as the object.

[0077] Examples

[0078] The wire rod disclosed in this embodiment has a specification of 6.5 mm. The chemical composition of the wire rod includes, by mass percentage: C: 0.45%, Si: 0.22%, Mn: 0.58%, P: 0.058%, S: 0.012%, Cr: 0.035%, As: 0.004%, Ni+As: 0.016%, Ce: 0.025%, and the rest are Fe and inevitable impurities;

[0079] The production process flow for controlling red rust of the wire rod includes: billet heating - high-pressure water descaling - rough rolling - medium rolling - pre-finishing rolling - water cooling - finishing rolling - water cooling - laying head - Stelmor air cooling - coiling - packing.

[0080] (1) For billet heating, sectional heating is adopted. The temperature of the preheating section is: 920 °C, the temperature of the heating section is: 1070 °C, the temperature of the soaking section is: 1130 °C, and the residence time in the furnace is 95 min; a reducing atmosphere is maintained in the preheating section and the soaking section in the furnace, and an oxidizing atmosphere is maintained in the heating section. The through-strip temperature difference of the billet is 20 °C.

[0081] (2) High-pressure water descaling: On each of the four sides of the spray beam, there are 3 identical high-pressure water descaling nozzles on each side. The water pressure of the middle nozzle is controlled at 19 MPa, and the water pressure of the two nozzles on both sides is controlled at 16 MPa. The inclination angle of the nozzle central axis with respect to the normal direction of the billet is 16°, and the straight-line distance from the nozzle to the surface of the square billet is 155 mm, so that the surface temperature of the billet is 1120 °C and the corner temperature is 1110 °C.

[0082] (3) Rough rolling and medium rolling: The elongation coefficient of each pass: 1.4 - 1.45, the water pressure of the roll cooling water is 7 bar, and the water volume is 1350 L / min.

[0083] (4) Pre-finishing rolling: After pre-finishing rolling, two water tanks are opened. The water pressure of the water tanks is: 4 Mpa, and the water volume of each water tank is 240 L / min.

[0084] (5) Finishing rolling: The elongation coefficient of each pass in finishing rolling: 1.2 ~ 1.22, and the final rolling speed is 112 m / s.

[0085] (6) Water cooling: There are a total of 6 water tanks after finishing rolling. Open the No. 1 water tank, No. 3 water tank, and No. 5 water tank. The water volume is evenly distributed, and the water volume of each water tank is 650 L / min. The water pressure of the cooling water is: 4 bar, and the reverse air scavenging pressure is: 5.5 bar.

[0086] (7) The water pressure of the roll cooling water for pre-finishing rolling and finishing rolling is 6 bar, and the water volume is 600 L / min.

[0087] (8) Roller cooling water chloride ion: 75 mg / L, calcium and magnesium ions: 180 mg / L, conductivity: 750 us / cm, pH value: 7, suspended matter: 4 mg / L, turbidity: 4 NTU, grease: 0.08 mg / L, total phosphorus: 0.28 mg / L, water temperature: 20°C.

[0088] (9) Cooling water in the water tank: chloride ion: 65 mg / L, calcium and magnesium ions: 210 mg / L, dissolved oxygen: 0.05 mg / L, conductivity: 800 us / cm, pH value: 7, suspended solids: 8 mg / L, turbidity: 8 NTU, oil: 0.1 mg / L, total iron: 0.5 mg / L, total phosphorus: 0.3 mg / L, water temperature: 17 °C.

[0089] (10) Spinning temperature: 900℃.

[0090] (11) Stelmore air cooling: When the wire rod temperature is greater than 600°C, the cooling rate is 5.5°C / s; when the wire rod temperature is between 450-600°C, the cooling rate is 4°C / s.

[0091] The obtained finished wire rod roll is as follows Figure 1 shown.

[0092] Comparative Example:

[0093] The wire rod disclosed in this comparative example has a specification of 6.5 mm, and the chemical composition of the wire rod includes, by mass percentage: C: 0.45%, Si: 0.21%, Mn: 0.58%, P: 0.018%, S: 0.012%, Ni: 0.03%, As: 0.02%, Ni+As: 0.05%, and the rest is Fe and unavoidable impurities;

[0094] The production process flow of wire rod red rust control includes: billet heating - high-pressure water dephosphorization - rough rolling - intermediate rolling - pre-finishing rolling - water cooling - finishing rolling - water cooling - wire laying - Stelmor air cooling - coiling - packaging.

[0095] (1) The billet is heated in sections, with the preheating section temperature at 900°C, the heating section temperature at 980°C, the soaking section temperature at 1050°C, and the furnace time at 80 min. The preheating section and soaking section are kept in a reducing atmosphere, the heating section atmosphere is kept in an oxidizing atmosphere, and the temperature difference of the billet is 40°C.

[0096] (2) High-pressure water dephosphorization: There are three identical high-pressure water descaling nozzles on each of the four sides of the spray beam. The water pressure of the middle nozzle is controlled at 10 MPa, and the water pressure of the two nozzles on both sides is controlled at 10 MPa. The inclination angle between the center axis of the nozzle and the normal direction of the billet is 20°, and the straight-line distance from the nozzle to the billet surface is 170 mm, so that the surface temperature of the billet is 1040°C and the corner temperature is 1020°C.

[0097] (3) Rough rolling and intermediate rolling: The elongation coefficient for each pass is 1.2 - 1.25, the water pressure of the roll cooling water is 4.5 bar, and the water volume is 1000 L / min.

[0098] (4) Pre-finishing rolling: After pre-finishing rolling, 1 water tank is opened. The water pressure of the water tank is 6 Mpa, and the water volume of the water tank is 580 L / min.

[0099] (5) Finishing rolling: The elongation coefficient for each pass in finishing rolling is 1.4 - 1.45, and the final rolling speed is 110 m / s.

[0100] (6) Water cooling: There are a total of 6 water tanks after finishing rolling. The No. 1 water tank, No. 3 water tank, and No. 5 water tank are opened. The water volumes of the water tanks are 1200 L / min, 1000 L / min, and 100 L / min respectively. The water pressure of the cooling water is 3 bar, and the reverse air cleaning pressure is 3 bar.

[0101] (7) The water pressure of the roll cooling water for pre-finishing rolling and finishing rolling is 4 bar, and the water volume is 400 L / min.

[0102] (8) Chloride ions in the roll cooling water: 150 mg / L, calcium and magnesium ions: 300 mg / L, conductivity: 1500 us / cm, pH value: 8.5, suspended solids: 15 mg / L, turbidity: 10 NTU, oil: 3 mg / L, total phosphorus: 1.5 mg / L, water temperature: 28 °C.

[0103] (9) Chloride ions in the water tank cooling water: 120 mg / L, calcium and magnesium ions: 270 mg / L, dissolved oxygen: 0.5 mg / L, conductivity: 1200 us / cm, pH value: 6.5, suspended solids: 15 mg / L, turbidity: 13 NTU, oil: 5 mg / L, total iron: 2.5 mg / L, total phosphorus: 4 mg / L, water temperature: 25 °C.

[0104] (10) Spinning temperature: 880 °C.

[0105] (11) Stelmor air cooling: When the temperature of the wire rod is greater than 600 °C, the cooling rate is 8 °C / s. When the wire rod temperature is between 450 - 600 °C, the cooling rate is 2 °C / s.

[0106] The obtained finished coil of the wire rod is as Figure 2 shown.

[0107] By comparison Figure 1 and Figure 2 it can be known that the surface quality of the wire rod produced according to the example is good and there is no red rust, while the surface of the wire rod produced according to the comparative example has serious red rust.

[0108] In summary, for the hot-rolled wire rod and the production process for red rust control provided in this application, the contents of Ni and As are controlled in terms of composition to make the primary scale easy to remove. For wire rods with Si content greater than 0.2%, P and rare earth elements are added to lower the melting point of the fayalite phase. By controlling the water pressure, water volume, and billet temperature of high-pressure water descaling, the primary scale is removed completely. In the rolling process, large reduction ratios are used in the early stage and small reduction ratios in the later stage to avoid the rupture and oxidation of the scale. By using low water temperature and high laying head temperature, the cooling water volume is reduced, and the cooling water volume of each water tank is reasonably distributed to control the temperature gradient of the wire rod and ensure the adhesion of the mill scale. The water pressure of the cooling water and the reverse air cleaning pressure are reasonably controlled, and the finishing rolling speed is appropriately reduced to reduce the reaction of hot rolled pieces, water, and air at high temperature. At the same time, the water quality of the roll cooling water and the water tank cooling water is strictly controlled to avoid accelerating corrosion and causing red rust. Finally, on the basis of ensuring normal structure on the Stelmor cooling line, the oxidation of FeO is reduced, so that the surface quality of the final product is good and no red rust is generated.

[0109] Those skilled in the art of this technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as the general understanding of those of ordinary skill in the field to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as here.

[0110] The meaning of "and / or" as described in this application refers to the situation where each exists alone or both exist simultaneously.

[0111] The meaning of "connection" as described in this application can be a direct connection between components or an indirect connection between components through other components.

[0112] Taking the above ideal embodiments of the present invention as inspiration, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A production process for controlling red rust of hot-rolled wire rods, characterized in that: The chemical composition of the wire rods is determined according to the Si content. By mass percentage, When 0.06% ≤ Si < 0.2%, C is 0.06 - 0.82%, Mn is 0.3 - 0.6%, P ≤ 0.02%, S ≤ 0.015%, Ni ≤ 0.014%, As ≤ 0.015%, Ni + As ≤ 0.02%, and the rest are Fe and unavoidable impurities; When 0.2% ≤ Si ≤ 0.3%, C is 0.25 - 0.82%, Mn is 0.3 - 0.6%, P is 0.05% - 0.06%, S ≤ 0.015%, Ni ≤ 0.014%, As ≤ 0.015%, Ni + As ≤ 0.02%, REM is 0.02 - 0.03%, and the rest are Fe and unavoidable impurities, where REM is one or two or three of the rare earth elements Ce, Sc, and Y; Specifically, it includes the following steps: Step S1, heating the billet. The billet is fed into a heating furnace and heated in sections, and different-stage temperatures are set according to different silicon contents until the billet is heated to the preset temperature for rolling; Step S2, high-pressure water descaling. Three nozzles are installed on each of the four sides of the spraying beam. The water pressure of the nozzle located in the middle position is set to 18 - 20 MPa, and the water pressure of the other two nozzles is 15 - 17 MPa. The inclination angle range between the central axis of the nozzle and the normal line of the billet is 15 - 18°, and the linear distance between the nozzle and the billet surface is 150 - 160 mm; The high-pressure water is sprayed onto the billet surface by the nozzles to peel off and wash away the scale; Step S3, rough rolling. The billet is rolled in multiple passes using the rolls of the rough rolling mill, and the billet is rolled with a large deformation amount. Among them, the elongation coefficient of each pass is set to 1.4 - 1.5; Step S4, intermediate rolling. The billet is rolled in multiple passes on the intermediate rolling mill to reduce the cross-sectional size of the steel after rough rolling. Among them, the elongation coefficient of each pass is set to 1.4 - 1.5; Step S5, continue to roll the billet. After pre-finishing rolling, two water tanks are set up, and water is sprayed on the wire rods for cooling. The water pressure of the water tanks is set to 3 - 5 Mpa, the water volume of each water tank is 200 - 300 L / min, the water pressure of the roll cooling water is 5.5 - 7 bar, and the water volume is 500 - 700 L / min; Step S6, finish rolling. The wire rods are continuously rolled on the finish rolling mill, and the elongation coefficient of each pass of finish rolling is set to 1.2 - 1.25; Step S7, water cooling after finish rolling. Six water tanks are set up, and three of them are opened. The water volume of each water tank is set to 600 - 800 L / min, the water pressure of the roll cooling water is 3.5 - 6 bar, and the reverse air scavenging pressure is 4 - 7 bar; Step S8, laying; Step S9, Stelmor air cooling. The cooling speed is set according to different carbon contents and different temperature ranges of the wire rods; When the temperature range of the wire rods is 450 - 600 °C, the cooling speed of air cooling is set to 3.5 - 5.5 °C / s; When the temperature of the wire rod > 600 °C, the cooling rate of the steel with a carbon content of 0.06% - 0.25% is set to 1.5 - 2.5 °C / s, the cooling rate of the steel with a carbon content of 0.25% - 0.6% is set to 4 - 9 °C / s, and the cooling rate of the steel with a carbon content of 0.6% - 0.82% is set to 11 - 15 °C / s; Step S10, coil collecting, collecting the air-cooled wire rods into coils; Step S11, packing, using packaging materials to bundle and fix the wire rod coils.

2. The production process for controlling red rust of hot-rolled wire rods according to claim 1, characterized in that: In step S1, when 0.06% ≤ Si < 0.2%, the preheating section temperature of the heating furnace is set to 800 - 900 °C, the heating section temperature is set to 880 - 980 °C, and the soaking section temperature is set to 1040 - 1140 °C; When 0.2% ≤ Si ≤ 0.3%, the preheating section temperature of the heating furnace is set to 910 - 960 °C, the heating section temperature is set to 1060 - 1100 °C, and the soaking section temperature is set to 1130 - 1170 °C; The heating time of the steel billet in the heating furnace lasts for 90 - 100 min, maintaining a reducing atmosphere in the preheating section and soaking section of the heating furnace, and an oxidizing atmosphere in the heating section, controlling the through-strip temperature difference of the steel billet ≤ 30 °C.

3. The red rust control production process of the hot-rolled wire rod according to claim 1, characterized in that: In step S3, the water pressure of the roll cooling water for rough rolling is set to 6 - 8 bar, and the water volume is set to 1200 - 1500 L / min; In step S4, the water pressure of the roll cooling water for medium rolling is set to 6 - 8 bar, and the water volume is set to 1200 - 1500 L / min; In step S6, the water pressure of the roll cooling water for finish rolling is set to 5.5 - 7 bar, the water volume is set to 500 - 700 L / min, and the finish rolling speed ≥ 105 m / s.

4. The red rust control production process of the hot-rolled wire rod according to claim 3, characterized in that: In steps S3 - S7, the specific settings of each index in the water quality of the cooling water are as follows: chloride ion ≤ 100 mg / L, calcium and magnesium ions ≤ 250 mg / L, dissolved oxygen ≤ 0.2 mg / L, conductivity ≤ 1000 us / cm, pH value range is 7.0 - 8.0, suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, grease ≤ 0.3 mg / L, total iron ≤ 1.0 mg / L, total phosphorus ≤ 0.5 mg / L, and water temperature is 15 - 25 °C.

5. The production process for controlling red rust of hot-rolled wire rods according to claim 4, characterized in that: Optimize the water quality in the water tank and the water quality of the roll cooling water respectively. Among them, the settings of each index of the water quality in the water tank are: chloride ion ≤ 70 mg / L, calcium and magnesium ions ≤ 250 mg / L, dissolved oxygen ≤ 0.1 mg / L, conductivity ≤ 900 us / cm, pH value range is 7.0 - 8.0, suspended solids ≤ 10 mg / L, turbidity ≤ 10 NTU, grease ≤ 0.3 mg / L, total iron ≤ 0.8 mg / L, total phosphorus ≤ 0.5 mg / L, and water temperature is 15 - 20 °C; The settings of each index of the water quality of the roll cooling water are: chloride ion ≤ 80 mg / L, calcium and magnesium ions ≤ 200 mg / L, conductivity ≤ 800 us / cm, pH value range is 7.0 - 7.5, suspended solids ≤ 4 mg / L, turbidity ≤ 4 NTU, grease ≤ 0.1 mg / L, total phosphorus ≤ 0.3 mg / L, and water temperature is 20 - 25 °C.

6. The red rust control production process of the hot-rolled wire rod according to claim 1, characterized in that: In step S7, the six set water tanks are sequentially numbered as water tank No. 1, water tank No. 2, water tank No. 3, water tank No. 4, water tank No. 5, and water tank No. 6, and the three opened water tanks are water tank No. 1, water tank No. 3, and water tank No.

5.

7. The red rust control production process of the hot-rolled wire rod according to claim 1, characterized in that: In step S8, the setting range of the wire spitting temperature is 880 - 940 °C.

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