Wire rod for high-quality rubber tube steel wire and preparation method of wire rod

Abstract

The invention discloses a wire rod for a high-quality rubber tube steel wire and a preparation method of the wire rod. The wire rod comprises the following components in percentage by mass: 0.80%-0.84% of C, 0.10%-0.20% of Si, 0.50%-0.60% of Mn, less than or equal to 0.014% of P, 0.0030%-0.010% of S, 0.0020%-0.0045% of total oxygen, 0.0005%-0.0015% of Als, 0.0001%-0.0010% of Nb, 0.0004%-0.0010% of Co, 0.01%-0.10% of Cr and the balance of iron and inevitable impurities. Through the design of the chemical components and the production process of the wire rod, the strength difference of the prepared wire rod is smaller than or equal to 35 MPa, the hardness difference of the cross section of the wire rod is smaller than or equal to 40 HV1, and the requirement for the long fatigue life of a rubber tube steel wire is met.

Description

Technical Field

[0001] The invention relates to the technical field of materials and metallurgy, and more specifically, to a wire rod for high-quality hose steel wire and a preparation method thereof. Background Art

[0002] High carbon steel wire rods are widely used in the production of steel cords, tire bead wires, automotive control wires, hose wires, etc. The strength uniformity of high-strength hose wires has an important influence on the service performance of the wires. Hose wires with large strength differences will cause the fatigue life of the hoses to decrease after being made into hoses, affecting the service performance of the products.

[0003] The Chinese patent with application number CN202310976619.5 discloses a wire rod for ultra-high strength hot-dip galvanized steel wire rope and a production method thereof, wherein the chemical composition by mass percentage is: C: 0.85-0.88%, Si: 0.18-0.25%, Mn: 0.50-0.55%, Cr: ≤0.05%, P≤0.012%, S≤0.008%, Ni≤0.05%, Cu≤0.05%, Mo≤0.03%, Al≤0.0020%, Ti≤0.0012%, O≤0.0030%, N≤0.0050%, and the remainder is Fe and unavoidable impurities. During production, the process of molten steel smelting, LF refining, continuous casting and steel rolling can produce ultra-high strength hot-dip galvanized steel wire rope wire rods, which can improve the strength of the wire rods while solving the problems of wire rod core segregation, insufficient network cementite and troostite content. However, the wire rod composition design and production process design were not carried out from the perspective of controlling the uniformity of the strength of the hose steel wire.

[0004] With the increasing requirements for equipment service performance in the manufacturing field, there is an urgent need to design a high-quality hose steel wire wire rod that can improve the uniformity of steel wire strength so that the hose steel wire has a longer fatigue life and meets the requirements for equipment fatigue life in the equipment manufacturing field. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects of the prior art and provide a high-quality wire rod for hose steel wire and a preparation method thereof. By means of the chemical composition of the wire rod and the production process design, the strength difference of the hose steel wire made of the wire rod is reduced to meet the requirement of higher fatigue life of the hose steel wire.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A high-quality wire rod for hose steel wire comprises the following components in percentage by mass: C: 0.80%-0.84%, Si: 0.10%-0.20%, Mn: 0.50%-0.60%, P≤0.014%, S: 0.0030%-0.010%, total oxygen: 0.0020%-0.0045%, Als: 0.0005%-0.0015%, Nb: 0.0001%-0.0010%, Co: 0.0004%-0.0010%, Cr: 0.01%-0.10%, and the balance is iron and inevitable impurities.

[0008] The present invention also discloses a method for preparing the high-quality wire rod for hose steel wire as described above, comprising the following steps: converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, and wire rod cooling;

[0009] In the converter smelting, scrap steel and molten iron are used as furnace materials, and the scrap steel ratio is 5% to 15%;

[0010] In the continuous casting, the molten steel subjected to the LF refining treatment is continuously cast to obtain a continuously cast ingot;

[0011] During the continuous casting billet heating and continuous rolling, the continuous casting billet produced in the continuous casting process is sent into a heating furnace for heating, and the heated continuous casting billet is continuously rolled, and the final rolling temperature is 920° C. to 990° C.;

[0012] In the wire rod rolling, the steel billet after continuous rolling is heated in a heating furnace, and then subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire laying in sequence;

[0013] During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain the wire rod for the steel cord.

[0014] Implementing the embodiments of the present invention will have the following beneficial effects:

[0015] The present invention designs an optimal component system and adopts smelting, continuous casting billet heating and continuous rolling, rolling, cooling and other production processes that match the alloy composition to obtain a wire rod with a strength difference of ≤35MPa and a cross-sectional hardness difference of ≤40HV1, which meets the requirements of a higher fatigue life of the hose steel wire. At the same time, the preparation method of the present invention has the characteristics of low production cost and strong process applicability, which is conducive to its production and promotion and application, and has significant social benefits. DETAILED DESCRIPTION

[0016] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0017] 1. Chemical composition and mechanical properties

[0018] The invention discloses a high-quality wire rod for rubber hose steel wire, comprising the following components in mass percentage: C: 0.80%-0.84%, Si: 0.10%-0.20%, Mn: 0.50%-0.60%, P≤0.014%, S: 0.0030%-0.010%, total oxygen: 0.0020%-0.0045%, Als: 0.0005%-0.0015%, Nb: 0.0001%-0.0010%, Co: 0.0004%-0.0010%, Cr: 0.01%-0.10%, and the balance is iron and inevitable impurities.

[0019] Specifically, the mechanism of action of each alloy component in the wire rod of the present invention is as follows:

[0020] Carbon is the main element that controls the strength of the wire rod. If the carbon content of the wire rod is too low, it cannot meet the user's requirements for the strength of the hose steel wire. If the content is too high, the strength of the hose steel wire will exceed the user's requirements; therefore, the carbon content in the present invention is controlled to be 0.80% to 0.84%.

[0021] Silicon element increases the eutectoid transformation temperature of steel, causes pearlite to transform in the high temperature zone, and makes the pearlite structure of the wire rod coarse, which is not conducive to the complex deformation of the steel wire. Low silicon content will result in insufficient deoxidation of the molten steel; excessive silicon content in the steel will cause coarse silicate inclusions in the steel, resulting in cracking or breaking of the hose steel wire during drawing. Therefore, the silicon content in the present invention is controlled at 0.10% to 0.20%.

[0022] Manganese is an element that improves the strength of wire rods, so that the steel wire meets the user's tensile strength requirements; manganese has the effect of reducing the eutectoid transformation temperature of steel, refining the pearlite structure of wire rods, improving the coordinated deformation ability of wire rods at different parts during the processing of hose steel wires, and improving the strength uniformity of hose steel wires. However, excessive manganese content causes band segregation in wire rods, increasing the wire breakage rate of hose steel wires processed by wire rods. Therefore, the manganese content in the present invention is controlled at 0.50% to 0.60%.

[0023] Phosphorus is easy to form band segregation in the wire rod, reducing the coordinated deformation ability of different parts of the wire rod during the steel wire processing, causing cracking, drawing and breaking of the hose steel wire, and reducing the strength uniformity of the hose steel wire. Therefore, the phosphorus content in the present invention is controlled to be no higher than 0.014%.

[0024] Since MnS inclusions have good deformation ability, an appropriate amount of sulfur in the steel can reduce the harm of non-deformable inclusions in the steel, prevent the generation of micro cracks caused by inclusions, and improve the strength uniformity of the hose steel wire. However, a higher sulfur content in the steel reduces the cold working performance of the wire rod. Therefore, the sulfur content in the present invention is controlled at 0.0030% to 0.010%.

[0025] When the oxygen content is high, the inclusions in the steel are large in size, which easily leads to the appearance of micro cracks in the process of wire rod processing and causes the steel wire to crack. When the oxygen content is low, the inclusions in the wire rod have poor deformation ability, and cracks are easy to appear between the inclusions and the matrix, which is not conducive to the processing of tire bead hose steel wire; therefore, the total oxygen content of the wire rod in the present invention is controlled at 0.0020% to 0.0045%.

[0026] When the acid-soluble aluminum content is high, the Al2O3 content of the inclusions in the steel increases, which is easy to cause cracking during the processing of the hose steel wire. When the acid-soluble aluminum content in the wire rod is too low, the melting point of the inclusions in the steel is high, which is not conducive to the processing of the hose steel wire. Therefore, the acid-soluble aluminum content of the present invention is controlled at 0.0005% to 0.0015%.

[0027] A high niobium content causes severe hardening of the wire rod during the steel wire processing, resulting in cracking and breakage of the hose steel wire during drawing. However, an appropriate niobium content prevents grain coarsening during the heating process of the steel billet, ensures that the wire rod structure meets the requirements of the hose steel wire processing, and improves the strength uniformity of the hose steel wire. Therefore, the niobium content of the present invention is controlled at 0.0001% to 0.0010%.

[0028] The cobalt element increases the precipitation temperature of proeutectoid ferrite, reduces the level of Widmanstatten structure in the wire rod, improves the uniform deformation performance of the wire rod, and is conducive to improving the uniformity of the strength of the hose steel wire. The cobalt element is dissolved in the steel to improve the strength of the steel. However, the cobalt content in the steel should not be too high to prevent the higher wire rod strength from reducing the drawing performance of the wire rod. Therefore, the cobalt content in the present invention is controlled at 0.0004% to 0.0010%.

[0029] Chromium improves the hardenability of the wire rod, refines the wire rod structure, and is beneficial to improving the uniformity of the mechanical properties of the hose steel wire made of the wire rod. However, too high a chromium content deteriorates the processing performance of the wire rod. Therefore, the chromium content of the present invention is controlled to be 0.01% to 0.1%.

[0030] In a specific embodiment, the ferrite grain size of the wire rod of the present invention is ≤30μm; the size distribution of the ferrite grains of the wire rod is: particle size ≤5μm, accounting for 62% to 68% of the number; particle size ≤10μm, accounting for 78% to 84% of the number; particle size ≤15μm, accounting for 83% to 92% of the number.

[0031] In a specific embodiment, the pearlite lamellae spacing at the surface of the wire rod of the present invention is 0.10μm to 0.15μm, the pearlite lamellae spacing at 1 / 4 diameter from the surface is 0.13μm to 0.18μm, and the pearlite lamellae spacing at the core is 0.15μm to 0.22μm.

[0032] In a specific embodiment, the carbon segregation index at the surface of the wire rod of the present invention is ≤1.05, the carbon segregation index at 1 / 4 diameter from the surface is ≤1.08, and the carbon segregation index at the core of the wire rod is ≤1.14.

[0033] In a specific embodiment, the strength difference of the wire rod is ≤35 MPa, and the hardness difference of the cross section of the wire rod is ≤40 HV1.

[0034] 2. Production technology

[0035] The present invention also discloses a method for preparing high-quality wire rod for hose steel wire as in any embodiment of the present invention, comprising the following steps: converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, and wire rod cooling.

[0036] Further, the method specifically includes the following steps:

[0037] S1. In converter smelting, scrap steel and molten iron are used as furnace charge, and the proportion of scrap steel is 5% to 15%.

[0038] In S2 and LF refining, the molten steel treated by LF refining is continuously cast to obtain a continuously cast ingot.

[0039] In a specific embodiment, the molten steel after the converter smelting enters the LF furnace for refining treatment, the refining temperature of the LF furnace is 1450° C. to 1540° C., and the refining time is 30 min to 50 min.

[0040] S3. During continuous casting, the molten steel subjected to LF refining treatment is continuously cast to obtain a continuously cast ingot.

[0041] In a specific embodiment, the cross-sectional size of the continuous casting billet is (250-300) mm×(350-400) mm; the surface temperature of the edge of the continuous casting billet during the straightening process is 900°C-930°C, and the temperature of the corner of the continuous casting billet is 790°C-830°C; the size of inclusions in the molten steel after the converter is ≤100μm, the size of inclusions after refining treatment in the LF furnace is ≤50μm, and the size of inclusions in the molten steel at the tundish is ≤40μm.

[0042] S4. During the continuous casting billet heating and continuous rolling, the continuous casting billet off the line in the continuous casting process is sent to a heating furnace for heating, and the heated continuous casting billet is continuously rolled, and the final rolling temperature of the continuous rolling is 920°C to 990°C.

[0043] In a specific embodiment, the total furnace heating time of the continuous casting billet is 3.5h to 4.5h; the preheating section temperature is 980℃ to 1080℃, the heating section temperature is 1150℃ to 1180℃, the soaking section temperature is 1200℃ to 1220℃, and the billet soaking section insulation time is 40min to 50min.

[0044] S5. During the wire rod rolling, the steel billet after continuous rolling is heated in a heating furnace, and then sequentially subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire drawing.

[0045] In a specific embodiment, during the wire rod rolling, the wire rod is produced by a square billet, the total furnace time of the billet is 140min-160min, the temperature of the soaking section is 1100℃-1150℃, the insulation time of the billet soaking section is 30min-50min, the high temperature diffusion of the billet is used to reduce the segregation of elements such as carbon and manganese, and control the grain size of the billet; the residual oxygen content of the heating furnace is 3%-9%, and the atmosphere pressure in the furnace is 2Pa-12Pa; after the billet is heated, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling, and then the wire rod spinning operation is carried out; the pre-finishing rolling temperature of the wire rod is 985℃-1005℃; the finishing rolling temperature is 890℃-930℃; the temperature of the double module is 880℃-940℃; the wire rod spinning temperature is 910℃-940℃. The higher spinning temperature of the wire rod increases the cooling rate of the wire rod on the air-cooled roller, laying the foundation for controlling the final organization of the wire rod. The wire rod rolling specifications are 5.0mm~6.5mm.

[0046] S6. During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain high-quality wire rod for hose steel wire.

[0047] In a specific embodiment, during the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning, the cementite precipitation temperature of the wire rod is controlled to be 700°C to 730°C, the cooling rate of the wire rod is 15°C / s to 25°C / s, the undercooling degree of the wire rod austenite to pearlite phase transformation is controlled to be 80°C to 120°C, and the phase transformation time is 12s to 18s. After final cooling, the wire rod cord steel wire rod is mainly composed of sorbite structure, which is convenient for users to draw steel wires.

[0048] The following are specific embodiments

[0049] Examples 1-6

[0050] The chemical composition, preparation process and performance parameters of the wire rods of Examples 1-6 of the present invention are shown in Table 1.

[0051] Table 1 Chemical composition, preparation process and performance parameters of wire rods of Examples 1-6

[0052]

[0053]

[0054] According to the above results, the present invention has carried out a large number of systematic experimental studies from the aspects of alloy element screening and proportioning, converter smelting, LF refining, continuous casting, continuous casting billet heating and continuous rolling, wire rod rolling, wire rod cooling process design optimization, etc., and finally determined the component system and its manufacturing process that can meet the purpose of the present invention, and finally obtained a high-quality wire rod for hose steel wire with a strength difference of ≤35MPa and a cross-sectional hardness difference of ≤40HV1.

[0055] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-quality wire rod for hose steel wire, characterized in that: The following components are included in mass percentage: C: 0.80%~0.84%, Si: 0.10%~0.20%, Mn: 0.50%~0.60%, P≤0.014%, S: 0.0030%~0.010%, total oxygen: 0.0020%~0.0045%, Als: 0.0005%~0.0015%, Nb: 0.0001%~0.0010%, Co: 0.0004%~0.0010%, Cr: 0.01%~0.10%, and the balance is iron and inevitable impurities.

2. The high-quality hose steel wire rod according to claim 1, characterized in that: Wire rod ferrite grain size ≤30μm; The size distribution of wire rod ferrite grains is as follows: particle size ≤5μm, accounting for 62% to 68% in number; particle size ≤10μm, accounting for 78% to 84% in number; particle size ≤15μm, accounting for 83% to 92% in number.

3. The high-quality hose steel wire wire according to claim 1, characterized in that: The pearlite lamellar spacing at the surface of the wire rod is 0.10μm~0.15μm, the pearlite lamellar spacing at 1 / 4 diameter from the surface is 0.13μm~0.18μm, and the pearlite lamellar spacing at the center is 0.15μm~0.22μm.

4. The high-quality hose steel wire wire according to claim 1, characterized in that: The carbon segregation index at the surface of the wire rod is ≤1.05, the carbon segregation index at a distance of 1 / 4 of the diameter from the surface is ≤1.08, and the carbon segregation index at the center of the wire rod is ≤1.14; The strength difference of wire rod is ≤35MPa, and the hardness difference of wire rod cross section is ≤40HV1.

5. A method for preparing a high-quality hose steel wire wire according to any one of claims 1 to 4, characterized in that: The following steps are involved: Converter smelting, LF refining, continuous casting, continuous casting billet heating and rolling, wire rod rolling, wire rod cooling; In the converter smelting, scrap steel and molten iron are used as furnace materials, and the scrap steel ratio is 5% to 15%; In the continuous casting, the molten steel subjected to the LF refining treatment is continuously cast to obtain a continuously cast ingot; During the continuous casting billet heating and continuous rolling, the continuous casting billet produced in the continuous casting process is sent into a heating furnace for heating, and the heated continuous casting billet is continuously rolled, and the final rolling temperature is 920° C. to 990° C.; In the wire rod rolling, the steel billet after continuous rolling is heated in a heating furnace, and then subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling, and wire laying in sequence; During the cooling of the wire rod, the wire rod is cooled on an air-cooled roller after spinning to obtain the wire rod for the steel cord.

6. The preparation method according to claim 5, characterized in that: In the LF refining, the molten steel discharged from the converter smelting enters the LF furnace for refining treatment. The refining temperature of the LF furnace is 1450° C. to 1540° C., and the refining time is 30 min to 50 min.

7. The preparation method according to claim 5, characterized in that: In the continuous casting, the cross-sectional size of the continuous casting billet is (250-300) mm×(350-400) mm; the surface temperature of the edge of the continuous casting billet during the straightening process is 900°C-930°C, and the temperature of the corner of the continuous casting billet is 790°C-830°C; the size of the molten steel inclusions at the rear of the converter is ≤100 μm, the size of the inclusions after the LF furnace refining treatment is ≤50 μm, and the size of the molten steel inclusions at the tundish position is ≤40 μm.

8. The preparation method according to claim 5, characterized in that: During the continuous casting billet heating and continuous rolling, the total heating time of the continuous casting billet in the furnace is 3.5h to 4.5h; the preheating section temperature is 980℃ to 1080℃, the heating section temperature is 1150℃ to 1180℃, the soaking section temperature is 1200℃ to 1220℃, and the billet soaking section insulation time is 40min to 50min.

9. The preparation method according to claim 5, characterized in that: In the wire rod rolling, the total furnace time of the steel billet is 140min-160min, the temperature of the soaking section is 1100℃-1150℃, and the insulation time of the steel billet soaking section is 30min-50min; the residual oxygen content of the heating furnace is 3%-9%, and the atmosphere pressure in the furnace is 2Pa-12Pa; after the steel billet is heated, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling before the wire rod spinning operation is performed; the pre-finishing rolling temperature of the wire rod is 985℃-1005℃; the finishing rolling temperature is 890℃-930℃; the temperature of the wire rod entering the double module is 880℃-940℃; and the wire rod spinning temperature is 910℃-940℃. The wire rod specification is 5.0mm-6.5mm.

10. The preparation method according to claim 5, characterized in that: During the wire rod cooling, the wire rod is cooled on an air-cooled roller after spinning, the cementite precipitation temperature of the wire rod is controlled to be 700°C to 730°C, the wire rod cooling rate is 15°C / s to 25°C / s, the undercooling degree of the wire rod austenite to pearlite phase transformation is controlled to be 80°C to 120°C, and the phase transformation time is 12s to 18s.

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