Economical high-carbon boron-containing steel wire rod for card clothing and method for manufacturing the same

Abstract

The application relates to an economical high-carbon boron-containing steel wire rod for card clothing and a manufacturing method thereof, and belongs to the field of wire rods. Element components are as follows: C: 0.80%-1.00%, Mn: 0.60%-0.90%, Si: 0.10%-0.40%, P<=0.02%, S<=0.015%, B: 0.001%-0.05%, V: 0.05%-0.50%, and the rest is Fe and inevitable impurities. The steel wire rod with a specification of phi 5.5mm-phi 6.5mm has a tensile strength of 1150-1300Mpa, a surface shrinkage of >40%, a decarburized layer of <=0.06mm, a structure mainly being sorbite with a lamellar spacing of 0.08-0.15um, a grain size reaching more than 7 levels, and a reticular carbide level being <2 levels. The application adds B elements, replaces the addition of other alloys by combining B and V, greatly improves the cooling capacity of the rod, realizes fast cooling at a speed of >25 DEG C / s in a phase transition interval, and thus obtains an economical card clothing steel wire rod with good comprehensive performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a steel wire rod and a manufacturing method thereof, in particular to a high-carbon boron-containing card clothing steel wire rod and a manufacturing method thereof. BACKGROUND

[0002] Card clothing is an important spinning machine part for carding textile fibers, and has extremely high wear resistance requirements, so the composition and process design of the card clothing steel should primarily consider wear resistance. With the rapid development of the textile industry, downstream card clothing manufacturing enterprises have increasingly high performance requirements for card clothing wire rods, and ordinary card clothing wire rods SWRH72B and SWRH82B cannot meet the wear resistance requirements of high-end card clothing. High-end card clothing imported from abroad improves the wear resistance of card clothing by adding micro-alloying elements such as W, V, and Cr in high-carbon steel, but the production cost is very high. Therefore, in order to realize the high-quality and low-cost development of the card clothing industry, it is urgent to develop a new type of economic card clothing steel with better performance.

[0003] The disclosed patent number CN 105838981 A discloses a card clothing steel, specifically relates to the technical field of metal card clothing processing. The metal card clothing uses Nb, Cr, V, and other alloying elements in high-carbon steel to form C and N compounds to refine the grain size, improve the strength and wear resistance. However, the wire rod produced by this invention has high production cost due to the addition of Nb, Cr, and other alloying elements.

[0004] The disclosed patent number CN 110295316 A discloses a textile gassing elastic card clothing steel wire rod and a preparation method thereof, specifically relates to a wire rod and a production method of wet gassing elastic card clothing steel in the textile field. The elastic card clothing optimizes the element design of Mn, Cr, and Al in high-carbon steel and optimizes the process parameters of wire rod preparation to obtain a card clothing steel wire rod with good microstructure and performance, excellent surface and internal quality, and suitable for deep drawing, but the grain size of the wire rod produced by this invention cannot reach level 7.

[0005] The disclosed patent number CN 112899583 A discloses a high-elasticity high-nickel alloy card clothing steel wire rod and a preparation method thereof, specifically relates to a wire rod and a production method of stainless steel wire card clothing. The elastic card clothing adds Ni and rare earth elements to meet the use of card clothing in a humid and weakly alkaline environment, has high elasticity, strong corrosion resistance, and high service life, but the wire rod produced by this invention has high production cost due to the addition of precious alloy and rare earth elements, and does not adapt to the current market trend of cost reduction.

[0006] The disclosed patent number CN 102352469 B discloses an ultra-high strength vanadium-titanium composite micro-alloyed high-carbon steel wire rod and a preparation method thereof, and particularly relates to a production method of the ultra-high strength high-carbon steel wire rod. The high-carbon steel wire rod uses the addition of alloy elements such as Si, Mn, Cr, V, Ti, Cu and Al to improve the strength, but the production cost is high, which is not suitable for the current market trend of cost reduction. SUMMARY

[0007] The purpose of the present application is to provide an economical high-carbon boron-containing steel wire for card clothing, by innovative chemical composition design, adding B and V micro-alloy in high-carbon steel to improve the hardenability of the steel, making up for the reduced hardenability of the hypereutectoid steel (high-carbon steel) due to the high C content, so that the metal card clothing made of the steel wire can achieve the same wear resistance as the W, Cr and V micro-alloy element metal card clothing, while reducing the manufacturing cost of downstream users and improving the market competitiveness of the product.

[0008] The technical solution adopted by the present application to solve the above problems is: an economical high-carbon boron-containing steel wire for card clothing, the element composition mass percentage is C: 0.80%-1.00%, Mn: 0.60%-0.90%, Si: 0.10%-0.40%, P≤0.02%, S≤0.015%, B: 0.001%-0.05%, V: 0.05%-0.50%, and the rest is Fe and unavoidable impurities.

[0009] The chemical element action mechanism of the metal card clothing steel wire of the present application is as follows:

[0010] C is the main strengthening element in steel, which can significantly improve the strength of the steel through solid solution strengthening and precipitation strengthening. With the increase of C content, the strength shows an obvious upward trend, and the hardening of the wire after cold drawing is obvious, which helps to realize the strength of the finished steel wire. The proportion of sorbite in the wire obtained by Stelmor cooling is high when the C content is increased, but the hardenability of the hypereutectoid steel decreases with the increase of C content. Therefore, the C content is controlled at 0.80%-1.00%.

[0011] Si is added as a deoxidizer in steel, reacts with FeO in molten steel to form silicate and is removed, improving the purity of the molten steel. In addition, silicate inclusions in the wire can easily extend and deform along the drawing direction, without causing drawing line breakage hazards. The solid solution strengthening of Si element improves the work hardening rate of the steel, which can significantly deteriorate the cold working performance of the steel, and promotes the grain boundary segregation of elements P and S. Therefore, the weight percentage of Si is 0.10%-0.40%.

[0012] Mn is added as a strong deoxidizer in steel, which can form low-melting-point MnS with S to eliminate the harmful effects of S to some extent. Mn can improve the strength, hardenability and wear resistance of the steel, but with the increase of Mn

[0013] The increase of the content is easy to appear obvious temper brittleness phenomenon, and Mn has the effect of promoting grain growth, therefore the weight percentage of Mn is 0.60%-0.90%.

[0014] The main role of B element is to improve the hardenability of steel, and a small amount of B can improve the hardenability of steel. As a surface active element, B adsorbs on the austenite grain boundary, delays the effect of γ→α transformation, and its segregation on the austenite grain boundary hinders the nucleation of ferrite and is beneficial to the formation of bainite. When the amount of B is less than 0.0005%, the effect of improving the hardenability is very small, and when it is higher than 0.003%, the B phase (Fe3(C, B), Fe23(C, B)6), Fe2B) produced by the steel will precipitate along the austenite grain boundary, resulting in thermal embrittlement phenomenon. The billet passes through high-temperature diffusion, so that the austenite grains grow uniformly, the austenite grain boundary is reduced, and the boride precipitation point is reduced. B and O, N have strong affinity, and have strong interaction with various defects, and can be combined with S and C, and is easy to form various types of inclusions with other elements in the steel. Therefore, the weight percentage of B is 0.001%-0.05%.

[0015] V element is a strong carbide forming element, which generally forms very stable special carbides in steel wire, and the carbides widen the annealing and quenching heating temperature range of the wire, refine the austenite structure, and obtain fine martensite structure after quenching. At the same time, these carbides have very high hardness, and can be dispersedly distributed on the martensite matrix after quenching of the wire, so that a microstructure with good toughness and high wear resistance is obtained, which effectively improves the wear resistance of the wire. However, these small particle carbides with high hardness increase the deformation resistance of the semi-finished product wire during cold rolling, so the addition amount cannot be too much. At the same time, the addition of V content can improve the heat resistance and tempering stability of the wire, therefore the weight percentage of V is 0.05%-0.5%.

[0016] In the present application, the sum of B and V content is 0.051%<B+V<0.55%, and the addition of B and V is to improve the tensile strength of the rod and improve the wear resistance of the wire. The lower limit value is to consider the improvement of the tensile strength of the rod, and the performance of the wire exceeds that of ordinary 82B wire by adding micro-alloying elements; the upper limit value is to consider the production cost and the stability of the heat treatment performance of the wire. Through the comprehensive effect of B+V, a small amount of micro-alloying elements is added, which greatly improves the hardenability of the rod and the wear resistance of the finished wire. Compared with imported W-containing wire steel, the production cost is reduced, and the market competitiveness of the product is improved.

[0017] P element in the card clothing steel belongs to the harmful element, significantly reduces the plasticity and toughness of steel, makes the performance change for the worse. At the same time, phosphorus is easy to produce intracrystalline segregation in the crystallization process, makes the local area phosphorus content high, causes the cold brittle transition temperature to rise, thus the cold brittle occurs. The product needs to meet the customer quenching and tempering process requirements, in order to prevent the material plasticity and toughness to decline and the tempering brittleness phenomenon occurs, need to control P in ≤0.02%.

[0018] S element in the card clothing steel also belongs to the harmful element, reduces the ductility and toughness of steel. In solid state, the solubility of sulfur in iron is very small, but exists in the form of FeS in steel. Because the plasticity of FeS is poor, the steel containing more sulfur is more brittle. More seriously, FeS can form eutectic with Fe, which has low melting point (985℃), and distributes on the grain boundary of austenite. When the steel is heated to about 1200℃ for hot pressure processing, the eutectic on the grain boundary has been dissolved, the grain boundary is destroyed, so that the steel cracks along the grain boundary during processing, i.e. hot brittle. In addition, the sulfide non-metallic inclusions formed by the segregation of sulfur element will form fibrous structure during rolling, which reduces the mechanical properties of high strength steel products. The product needs to be heated at high temperature and rolled with large reduction, so the content of S needs to be strictly controlled ≤0.015%.

[0019] The above-mentioned manufacturing method of economical high-carbon boron-containing steel wire rod for card clothing, the steps include

[0020] (1) Steel smelting: including converter initial smelting, deoxidizing refining and soft argon blowing, preparing materials according to element design, adopting converter smelting, strictly controlling the converter tapping temperature > 1600℃ and the final C% > 0.08%, preventing the over-oxidation of molten steel; then refining in a converter, adopting low alkalinity synthetic slag to ensure sufficient deoxidization and removal of inclusions, and accurately controlling the target composition, in order to ensure the yield of B alloy, adding boron alloy into the molten steel according to the calculated amount after the deoxidization of the molten steel in the refining process, finally sampling and analyzing, slightly adjusting the composition of the molten steel, and then transferring the molten steel to RH furnace for direct argon blowing and stirring, so as to make the inclusions float up and the composition of the molten steel uniform, and ensure the floating of inclusions and the uniformity of the composition of the molten steel;

[0021] (2) Continuous casting: adopting low superheat casting of ≤30℃ molten steel, continuous casting speed: 0.8m / min-1.2m / min, adopting weak cooling in the secondary cooling zone of continuous casting: cooling water consumption 0.15-0.25L / Kg, preventing the corner cracks of the billet, adopting displacement mode for the light reduction of the continuous casting billet, and cooperating with the electromagnetic stirring at the solidification end, so as to ensure that the continuous casting billet has no obvious reduction cracks, center shrinkage and V-type segregation, and ensure the uniformity of the structure and composition of the continuous casting billet;

[0022] (3) the continuous casting billet off-line temperature > 500℃, after off-line, slow cooling is carried out to prevent billet cracking (this is a very critical process for the B-containing steel billet) ;

[0023] (4) wire rod rolling: the billet is subjected to surface treatment to remove surface defects, then the billet is heated to above 1150℃, and kept for above 1 hour before being discharged, high-pressure water descaling is carried out, then rolling is carried out at an opening rolling temperature of 950-1000℃, an entry finishing rolling temperature ≥ 930℃, an entry module temperature ≥ 900℃, the rolling process is divided into above 39 passes, the rolling speed is set to 100-108 m / s, and finally the wire rod is rolled;

[0024] (5) wire laying: the wire laying temperature is 850-900℃;

[0025] (6) Stelmor cooling line air cooling, the air cooling process realizes the transformation of sorbite, the opening degree of the fan is adjusted on line to make the cooling rate of the wire laying temperature to 600℃ be greater than 25℃ / s, due to the addition of B element, the cooling rate of the wire rod is greatly improved, thereby effectively inhibiting the precipitation of net-shaped carbide, when the intermediate point of the wire rod is cooled to 600℃, the wire rod is kept, the keeping time is 70-90s, the sorbite is fully transformed, and low-temperature phase transformation organizations such as troostite and bainite are avoided, and the temperature is reduced to 500℃ before the keeping is exited.

[0026] Preferably, in the continuous casting step, the light reduction of each roller is reduced according to the set value, and is adjusted appropriately in combination with the pressure difference between each flow, the pressure between the rollers is adjusted dynamically according to the thickness of the continuous casting billet, and the reduction of each roller is dynamically adjusted.

[0027] Preferably, in the Stelmor cooling line air cooling step, the opening degrees of the 1-3 fans on the Stelmor cooling line are adjusted, the fans after the 3rd are all closed, the keeping cover is closed, the roller speed is set to 0.85-0.95 m / s, the environment temperature is 10-20℃, the opening degrees of the 1-3 fans are as follows: the 1st: 60-80%, the 2nd: 60-80%, and the 3rd: 30-50%, so as to realize the required wire rod cooling mode.

[0028] Compared with the prior art, the advantages of the present application are that:

[0029] The tensile strength of the steel wire rod with a specification of φ5.5mm-φ6.5mm is 1150-1300Mpa, the area reduction is > 40%, the surface decarburized layer is ≤ 0.06mm, the structure is sorbite with a lamellar spacing of 0.08-0.15μm (the proportion of sorbite in the structure is above 85%, and the rest is ferrite), the grain size reaches above 7 levels, and the net-shaped carbide level is < 2 levels.

[0030] The present application discloses a kind of wire rod, and the proportion of the organization of the wire rod is high, which is suitable for downstream deep drawing, and the finished steel wire has good wear resistance.The wire rod with high alloy content is prone to element segregation, and abnormal organizations such as troostite and martensite appear, which causes wire breakage in the downstream processing process.By adding element B, the cooling capacity of the wire rod is greatly improved, and the above-mentioned phenomenon is avoided, and the stronger cooling capacity enables the tensile strength of the wire rod to be improved, the depth of decarburization layer to be reduced and the level of network to be reduced.The addition of element V forms fine and dispersed carbide particles, which ensures the wear resistance of the wire cloth. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A typical schematic diagram of the wire cloth steel wire rod of the present application is shown in the figure.

[0032] Figure 2 A typical schematic diagram of the wire cloth steel wire rod of the present application is shown in the figure.

[0033] Figure 3 A typical schematic diagram of the wire cloth steel wire rod of the present application is shown in the figure. DETAILED DESCRIPTION

[0034] The present application will be further described in detail below with reference to the accompanying drawings, and the embodiments are exemplary and intended to explain the present application, but cannot be understood as a limitation of the present application.

[0035] A 120t converter is used for smelting, and the tapping temperature is controlled at 1620℃, the end point C% is greater than or equal to 0.10%, then the converter is transferred to a refining furnace for refining, low alkalinity synthetic slag is used for refining to ensure sufficient deoxidization and removal of inclusions, and the target composition is accurately controlled, after refining, the RH vacuum furnace is matched for direct argon blowing and stirring, and through soft argon blowing, inclusions are further removed and the uniformity of the molten steel is ensured; then the molten steel is transferred to a continuous casting station, the continuous casting speed is controlled at 0.8m / min, the cooling water consumption of the secondary cooling zone of the continuous casting is 0.25L / Kg, the total amount of light pressing is 16mm, the end electromagnetic stirring is 1.5HZ / 300A, and the continuous casting billet with a cross-sectional size of 200mm*200mm is poured.

[0036] The continuous casting billet is surface treated to ensure that surface defects are removed cleanly, and then the continuous casting billet is heated to above 1100°C, the residual oxygen content in the furnace is controlled to be below 4%, and the billet is discharged after holding for 1 hour. After high-pressure water descaling, rolling is performed: the open rolling temperature is 1080°C, the entry temperature of the finishing rolling is 930°C, the entry temperature of the module is 900°C, the rolling process is divided into 39 passes, the rolling speed is set to 100 m / s, and the wire rod temperature is controlled to be 880°C; after rolling, the wire rod is air-cooled + slow-cooled on the Stelmor cooling line. In order to achieve balanced cooling rate on the cooling roller, the air volume of the No. 1-3 air fans on the cooling line needs to be adjusted according to the seasonal ambient temperature, the initial roller speed is 0.85 m / s, the ambient temperature is 15°C, and the opening degree of the No. 1-3 air fans is set as follows: No. 1: 70%, No. 2: 70%, and No. 3: 40%. The cooling rate of the wire rod is ensured to be greater than 25°C / s between the wire rod temperature of 880°C and 600°C to suppress the precipitation of net-shaped cementite, the wire rod enters the holding cover after the No. 3 air fan to be held for 75 s to ensure that the sorbite transformation time is long enough to avoid low-temperature phase change organization, and the wire rod forms uniform ferrite + sorbite structure after passing through the air-cooled roller. After the wire rod is discharged, the sample is aged, and the mechanical properties and microstructure of the wire rod are detected. The chemical composition of the implementation case is as follows:

[0037] Sample No. C Si Mn P S Cr Ni Cu V B Sample 1 0.81 0.25 0.72 0.01 0.008 0.05 0.01 0.02 0.14 0.005 Sample 2 0.82 0.26 0.70 0.012 0.007 0.04 0.01 0.03 0.15 0.006

[0038] The test results of the hot-rolled wire rod of the implementation case are as follows:

[0039]

Claims

1. A method for manufacturing an economical high-carbon boron-containing steel wire for needle-like fabric, characterized in that: The elemental composition of this wire, by mass percentage, is as follows: C: 0.80%-1.00%, Mn: 0.60%-0.90%, Si: 0.10%-0.40%, P≤0.02%, S≤0.015%, B: 0.001%-0.05%, V: 0.05%-0.50%, 0.051% < B + V < 0.55%, with the remainder being Fe and unavoidable impurities. (1) Steel smelting: including converter primary smelting, deoxidation refining and soft argon blowing. The materials are prepared according to the element design and the converter smelting is adopted. The converter tapping temperature is strictly controlled to be >1600℃ and the final C% is >0.08% to prevent the steel from over-oxidation. Then it is transferred to the refining furnace for refining. Low basicity synthetic slag is used to ensure sufficient deoxidation and removal of inclusions. At the same time, the target composition is precisely controlled. In order to ensure the yield of B alloy, boron alloy is added before the end of refining. After the steel is deoxidized during the refining process, the amount of B alloy to be added is calculated according to the alloy yield and then added to the steel. Finally, the steel is sampled and analyzed, and the steel composition is finely adjusted so that all elemental components meet the internal control requirements. Then the steel is transferred to the RH furnace and argon gas is blown directly to stir. Soft argon blowing allows the inclusions to float and the steel composition to be homogenized. (2) Continuous casting: molten steel with a low superheat of ≤30℃ is used for casting. The continuous casting speed is 0.8m / min-1.2m / min. The secondary cooling zone of continuous casting adopts weak cooling: the cooling water consumption is 0.15-0.25L / Kg. The continuous casting billet is lightly pressed using displacement mode and is combined with electromagnetic stirring at the end of solidification. (3) The continuous casting billet temperature after casting is >500℃, and it is slowly cooled after casting. (4) Wire rolling: The billet is surface treated to remove surface defects, then heated to above 1150℃ and held for more than 1 hour before being taken out of the furnace. After descaling with high pressure water, it is rolled: the initial rolling temperature is 950-1000℃, the finishing rolling temperature is ≥930℃, the module temperature is ≥900℃, the rolling process is divided into more than 39 passes, the rolling speed is set to 100m / s-108m / s, and finally rolled into wire. (5) Spinning: Spinning temperature 850-900℃; (6) The Stellmore cooling line is air-cooled. The air-cooling process realizes the transformation of sorbite. The opening degree of the fan is adjusted online so that the cooling rate is greater than 25℃ / s between the spinning temperature and 600℃. Due to the addition of element B, the cooling rate of the wire rod is greatly improved. When the middle point of the wire rod is cooled to 600℃, the heat preservation begins. The heat preservation time is 70-90s to ensure that the sorbite undergoes a full phase transformation. The heat preservation ends when the temperature drops to 500℃.

2. The method for manufacturing economical high-carbon boron-containing needle cloth steel wire according to claim 1, characterized in that: The steel wire with a specification of φ5.5mm-φ6.5mm has a tensile strength of 1150-1300Mpa, a shrinkage of area >40%, a decarburized layer ≤0.06mm, a microstructure mainly consisting of sorbite with a lamellar spacing of 0.08-0.15μm, a grain size of grade 7 or above, and a network carbide grade <2.

3. The method for manufacturing economical high-carbon boron-containing needle cloth steel wire according to claim 1, characterized in that: In the continuous casting process, the amount of light reduction of each roller is reduced according to the set value, and is appropriately adjusted in combination with the pressure difference between each flow. Based on the thickness of the continuously cast billet, the pressure between each roller is dynamically adjusted, thereby dynamically regulating the amount of reduction of each roller.

4. The method for manufacturing economical high-carbon boron-containing needle cloth steel wire according to claim 1, characterized in that: In the air-cooling step of the Steilmo cooling line, adjust the opening degree of fans 1-3 on the Steilmo cooling line, and shut down all fans after fan 3 and close the insulation cover at the same time. Set the roller speed to 0.85-0.95m / s, the ambient temperature to 10-20℃, and the opening degree of fans 1-3 to be: fan 1: 60-80%, fan 2: 60-80%, fan 3: 30-50%.

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