Titanium-niobium composite microalloying nitrogen-controlled 82B wire rod and preparation method

Abstract

The invention provides a titanium-niobium composite microalloying nitrogen-controlled 82B wire rod and a preparation method, and relates to the technical field of high-carbon hard wire production. The diameter of the 82B wire rod ranges from 11 mm to 12.5 mm, and the 82B wire rod is prepared from, by mass, 0.80%-0.85% of C, 0.60%-0.90% of Mn, 0.12%-0.32% of Si, 0.010%-0.015% of N, 0.020%-0.030% of Ti, 0.010%-0.015% of Nb, smaller than or equal to 0.025% of S, smaller than or equal to 0.025% of P, smaller than or equal to 0.20% of Cu and smaller than or equal to 0.20% of Ni. And the balance of Fe and inevitable impurities. The titanium-niobium composite microalloying nitrogen-controlled 82B wire rod is prepared by reasonably selecting Ti and Nb to be compositely added, continuously casting to form a blank and performing temperature-controlled cold rolling; the method is simple and easy to operate, wide in application range and beneficial to industrial large-scale production and popularization.

Description

Technical Field

[0001] The invention relates to the technical field of high carbon hard wire production, in particular to a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod and a preparation method thereof. Background Art

[0002] As a common high-carbon hard wire, 82B wire rod is widely used in mechanical processing, construction engineering and other fields. Short-process smelting has gradually become an important production mode in the steel industry due to its advantages such as short production cycle and low energy consumption. However, in the process of short-process production of high-carbon hard wire, the nitrogen content in the steel is relatively high, which can easily lead to problems such as poor plasticity, excessive work hardening rate, and increased wire breakage rate during subsequent cold drawing. Therefore, how to effectively control the adverse effects of nitrogen on steel performance has become one of the key technologies to improve the quality of short-process 82B.

[0003] As a strong nitride-forming element in steel, Ti is often used to improve the adverse effects of nitrogen on steel. However, the addition of Ti easily forms micron-sized square Ti (C, N), which is detrimental to the plasticity of 82B.

[0004] Chinese patent CN102876983A discloses a production process of 82B wire rod for high-strength prestressed steel wire and its wire rod, which refines the grains, improves the metallographic structure, and obtains a high sorbite rate by optimizing the chemical composition design of 82B wire rod for high-strength prestressed steel wire, adjusting the heating system of the heating furnace before rolling, and adopting controlled rolling and controlled cooling technology; however, there are many alloy elements to choose from, the cost is high, the operation process is complicated, and the operation is difficult.

[0005] Chinese patent CN107815607A discloses a micro-alloyed construction steel wire rod containing V, Nb, Ti, and Cr and its LF furnace production method. The alloying elements are still relatively large, and the nitrogen content in the micro-alloy is adjusted by feeding a N-containing cored wire into the LF furnace. The nitrogen-fixing elements are V, Nb, and Ti. The micron-sized square carbonitride points formed after the addition may destroy the continuity of the steel matrix, resulting in stress concentration when subjected to force, thereby reducing the plasticity of the steel.

[0006] Chinese patent CN116174479A discloses a production process for controlling the brittle fracture of 82B wire rod. It is necessary to solve the brittle fracture problem by accelerating the release of residual stress without changing the existing process route. The operation process is complicated and difficult, and it is difficult to predict whether the mechanical properties of the prepared wire rod can be effectively controlled.

[0007] Chinese patent CN104001741A discloses a method for controlled cooling of small-sized high-Cr 82B wire rod after rolling, which is mainly for controlled cooling of SWRH82B wire rod after rolling. It is necessary to control the spinning temperature, cooling speed before phase change after rolling, phase change temperature range, cooling speed in phase change zone, and base speed of Stelmor roller entrance section. The control process is complicated, many influencing factors need to be considered, the cost is high, and the efficiency is low. Summary of the invention

[0008] In order to solve the problem that the 82B wire rod in the prior art cannot effectively control the adverse effects of nitrogen on steel properties, specifically, micron-sized square Ti (C, N) will reduce the plasticity of 82B. Although it can be improved by adding alloy elements, there are technical problems such as high alloy element cost and difficulty in accurately controlling the organizational structure; and there is also improvement through preparation process, but it will make the operation process complicated, difficult to control, and many influencing factors are difficult to adjust. The present invention proposes a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod and a preparation method that can solve the above problems. The technical scheme is as follows:

[0009] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 11-12.5 mm, and the composition contents are as follows by mass percentage: C 0.80-0.85%, Mn 0.60-0.90%, Si 0.12-0.32%, N 0.010-0.015%, Ti 0.020-0.030%, Nb 0.010-0.015%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0010] Optionally, in the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the pearlite interlamellar spacing is 150-170nm, the pearlite nodule size is 4.5-5.5μm, and the Soxhletization rate is ≥92%.

[0011] Optionally, the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod has a tensile strength of 1250-1350 MPa, a cross-sectional shrinkage of 35-40%, an elongation after fracture of ≥12%, and a strain hardening index of ≤0.220.

[0012] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0013] S1. Raw material weighing: weigh all scrap steel raw materials, ferrotitanium and ferroniobium according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control;

[0014] S2, electric furnace nitrogen controlled smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace, and ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0015] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0016] S4, continuous casting into billets: the S3 refined molten steel is temperature controlled and continuously poured to obtain 82B continuous casting billets;

[0017] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling to obtain SWRH82B wire rod.

[0018] Optionally, the S1 ferrotitanium is at least one of FeTi30, FeTi40 and FeTi70, and the ferroniobium is at least one of FeNb50, FeNb60 and FeNb70.

[0019] Optionally, the heating temperature of the S2 electric furnace is ≥1600°C.

[0020] Optionally, the temperature of the S4 refined molten steel is controlled to be 1600° C., and the continuously cast billet is a square billet with a size of 150×150 mm.

[0021] Optionally, the heating temperature of the S5 steel billet is 1080-1120°C, the rolling temperature is 1040-1080°C, the wire laying temperature is 900-940°C, and the rolling speed is 30-35m / s. After rolling, the steel billet is cooled by air using the Stelmo air cooling line, the total length of the air cooling line is 90m, the air cooling speed at the 0-40m position is 8-10°C / s, and the position at 40-90m is cooled naturally.

[0022] Technical principle of the present invention:

[0023] The present invention converts the solid-solution nitrogen in the SWRH82B wire rod into the combined nitrogen in the nitride by Ti and Nb nitrogen fixation, thereby eliminating the plastic damage of SWRH82B caused by the solid-solution N atoms. The addition of Ti element alone will produce micron-scale square Ti (C, N), and the square precipitates destroy the continuity of the matrix, which has an adverse effect on the cold drawing of steel. After adding the Nb element, the interaction between Nb and Ti delays the precipitation of the precipitate phase, slows down the diffusion of atoms and inhibits the growth of precipitates, so the precipitates change from micron-scale Ti (C, N) to nanometer-scale (Nb, Ti) (C, N), and at the same time, the microalloy carbonitride pins the grain boundary. The nitride is formed during the steel smelting process and is not dissolved during the subsequent heat treatment process. The fine dispersed nitride pins the grain boundary, inhibits the growth of austenite, reduces the pearlite lamellar spacing and pearlite spherule size of the SWRH82B wire rod, and significantly reduces carbon emissions compared to the traditional long-process SWRH82B wire rod while improving its plastic toughness.

[0024] Compared with the prior art, the above technical solution has at least the following beneficial effects:

[0025] The above scheme, the present invention proposes a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod and a preparation method, which can solve the problem that the 82B wire rod in the prior art cannot effectively control the adverse effects of nitrogen on the performance of steel, specifically, micron-level square Ti (C, N) will reduce the plasticity of 82B. Although it can be improved by adding alloy elements, there are technical problems such as high alloy element cost and difficulty in accurately controlling the organizational structure; and there is also a technical problem that it can be improved through the preparation process, but it will make the operation process complicated, difficult to control, and there are many influencing factors that are difficult to adjust.

[0026] The present invention transforms the solid-solution nitrogen element in the steel into a (Ti, Nb) (C, N) precipitation phase by reasonably selecting the composite addition of Ti and Nb elements. Compared with adding only the Ti element, the composite addition of Ti and Nb elements refines the size of the precipitation phase, significantly reduces the content of micron-level square Ti (C, N) and improves the plasticity and toughness of 82B.

[0027] The present invention uses continuous casting to form billets and temperature-controlled cold rolling to control the rolling temperature and the spinning temperature to obtain a structure with a stable pearlite ball size and pearlite lamellar spacing. In addition, a controlled cooling method is used after rolling to quickly cool the pearlite balls and lamellars after spinning to avoid the appearance of network secondary cementite, and natural cooling after rapid cooling prevents the appearance of abnormal martensite structure.

[0028] Compared with the production of SWRH82B by an electric furnace using recycled steel raw materials without Ti and B nitrogen fixation, the present invention completely eliminates the plastic damage of the SWRH82B wire rod caused by excessively high N content, and also increases the tensile strength by 50-100 MPa.

[0029] The titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod prepared by the present invention has a tensile strength of 1250-1350 MPa, a cross-sectional shrinkage of 35-40%, an elongation after fracture of ≥12%, and a strain hardening index of ≤0.220.

[0030] In summary, compared with other traditional methods, the method of the present invention prepares titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod by reasonably selecting Ti and Nb composite addition, continuous casting into billets and temperature-controlled cold rolling, which not only reduces the particle size of carbonitrides, but also synergistically improves strength and plasticity; the method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, high in efficiency, wide in application range, and conducive to large-scale industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0032] Figure 1 This is an optical microstructure diagram of a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to Example 1 of the present invention;

[0033] Figure 2 This is an optical microstructure diagram of a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to Example 2 of the present invention;

[0034] Figure 3 This is an optical microstructure diagram of a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to Example 3 of the present invention;

[0035] Figure 4 This is an optical microstructure diagram of a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to Example 4 of the present invention;

[0036] Figure 5 This is an optical microstructure diagram of a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to Example 5 of the present invention;

[0037] Figure 6 This is an optical microstructure diagram of a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to Example 6 of the present invention;

[0038] Figure 7 is an optical microstructure diagram of the 82B wire rod of Comparative Example 1 of the present invention;

[0039] Figure 8 It is an optical microstructure diagram of the 82B wire rod of comparative example 2 of the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0041] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0042] In the embodiments of the present invention, "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction between them is not emphasized, the meanings they intend to express are consistent.

[0043] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0044] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0045] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 11-12.5 mm, and the composition contents are as follows by mass percentage: C 0.80-0.85%, Mn 0.60-0.90%, Si 0.12-0.32%, N 0.010-0.015%, Ti 0.020-0.030%, Nb 0.010-0.015%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0046] In particular, in the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the pearlite interlamellar spacing is 150-170nm, the pearlite nodule size is 4.5-5.5μm, and the Soxhletization rate is ≥92%.

[0047] In particular, the tensile strength of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 1250-1350 MPa, the cross-sectional shrinkage is 35-40%, the elongation after fracture is ≥12%, and the strain hardening index is ≤0.220.

[0048] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0049] S1. Raw material weighing: weigh all scrap steel raw materials, ferrotitanium and ferroniobium according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control;

[0050] S2, electric furnace nitrogen controlled smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace, and ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0051] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0052] S4, continuous casting into billets: the S3 refined molten steel is temperature controlled and continuously poured to obtain 82B continuous casting billets;

[0053] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling to obtain SWRH82B wire rod.

[0054] Particularly, the S1 ferrotitanium is at least one of FeTi30, FeTi40 and FeTi70, and the ferroniobium is at least one of FeNb50, FeNb60 and FeNb70.

[0055] In particular, the heating temperature of the S2 electric furnace is ≥1600°C.

[0056] In particular, the temperature of the S4 refined molten steel is controlled to be 1600°C, and the continuously cast billet is a square billet with a size of 150×150 mm.

[0057] In particular, the heating temperature of S5 steel billet is 1080-1120℃, the rolling temperature is 1040-1080℃, the wire laying temperature is 900-940℃, and the rolling speed is 30-35m / s. After rolling, the steel billet is cooled by Stelmo air cooling line, the total length of the air cooling line is 90m, the air cooling speed at 0-40m is 8-10℃ / s, and the position at 40-90m is naturally cooled.

[0058] Example 1

[0059] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 12-13 mm, and the composition contents are as follows by mass percentage: C 0.82%, Mn 0.67%, Si 0.12%, N 0.010%, Ti 0.022%, Nb 0.013%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0060] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0061] S1. Raw material weighing: according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control, all scrap steel raw materials, ferrotitanium and ferroniobium are weighed; wherein ferrotitanium is FeTi30 and ferroniobium is FeNb50;

[0062] S2, electric furnace smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace. After the steel is melted into molten steel, ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0063] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0064] S4, continuous casting: The S3 refined molten steel is temperature controlled and then continuously poured. The temperature of the molten steel is 1600°C after temperature control to obtain 82B continuous casting slabs. The 82B continuous casting slabs are square slabs with a size of 150×150 mm.

[0065] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling. After being kept at 1100℃ for 1h, rolling is carried out. The starting rolling temperature is 1060℃, the rolling rate is 32m / s, the spinning temperature is 920℃, and after rolling, a 90m air-cooling line is used. The air-cooling speed at 0-40m is 8-10℃ / s, and the position at 40-90m is naturally cooled to obtain SWRH82B wire rod.

[0066] Example 2

[0067] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 12.5 mm, and the composition contents are as follows by mass percentage: C 0.81%, Mn 0.68%, Si 0.12%, N 0.011%, Ti0.024%, Nb 0.012%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0068] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0069] S1. Raw material weighing: according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control, all scrap steel raw materials, ferrotitanium and ferroniobium are weighed; wherein ferrotitanium is FeTi40 and ferroniobium is FeNb60;

[0070] S2, electric furnace smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace. After the steel is melted into molten steel, ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0071] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0072] S4, continuous casting: The S3 refined molten steel is temperature controlled and then continuously poured. The temperature of the molten steel is 1600°C after temperature control to obtain 82B continuous casting slabs. The 82B continuous casting slabs are square slabs with a size of 150×150 mm.

[0073] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling. After being kept at 1100°C for 1h, rolling is performed. The starting rolling temperature is 1040°C, the rolling rate is 30m / s, the wire drawing temperature is 900°C, and after rolling, a 90m air-cooling line is used. The air-cooling speed at the 0-40m position is 8-10°C / s, and the position at 40-90m is naturally cooled to obtain SWRH82B wire rod.

[0074] Example 3

[0075] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 12.5 mm, and the composition contents are as follows by mass percentage: C 0.83%, Mn 0.80%, Si 0.21%, N 0.014%, Ti0.028%, Nb 0.016%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0076] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0077] S1. Raw material weighing: according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control, all scrap steel raw materials, ferrotitanium and ferroniobium are weighed; wherein ferrotitanium is FeTi70 and ferroniobium is FeNb70;

[0078] S2, electric furnace smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace. After the steel is melted into molten steel, ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0079] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0080] S4, continuous casting: The S3 refined molten steel is temperature controlled and then continuously poured. The temperature of the molten steel is 1600°C after temperature control to obtain 82B continuous casting slabs. The 82B continuous casting slabs are square slabs with a size of 150×150 mm.

[0081] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling. After being kept at 1100℃ for 1h, rolling is carried out. The starting rolling temperature is 1080℃, the rolling rate is 35m / s, the spinning temperature is 940℃, and a 90m air-cooling line is used after rolling. The air-cooling speed at the 0-40m position is 8-10℃ / s, and the position at 40-90m is naturally cooled to obtain SWRH82B wire rod.

[0082] Example 4

[0083] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 11.0 mm, and the composition contents are as follows by mass percentage: C 0.83%, Mn 0.84%, Si 0.31%, N 0.013%, Ti0.025%, Nb 0.013%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0084] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0085] S1. Raw material weighing: according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control, all scrap steel raw materials, ferrotitanium and ferroniobium are weighed; wherein ferrotitanium is FeTi30 and ferroniobium is FeNb50;

[0086] S2, electric furnace smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace. After the steel is melted into molten steel, ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0087] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0088] S4, continuous casting: The S3 refined molten steel is temperature controlled and then continuously poured. The temperature of the molten steel is 1600°C after temperature control to obtain 82B continuous casting slabs. The 82B continuous casting slabs are square slabs with a size of 150×150 mm.

[0089] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling. After being kept at 1120°C for 1h, rolling is performed. The starting rolling temperature is 1060°C, the rolling rate is 33m / s, the spinning temperature is 940°C, and a 90m air-cooling line is used after rolling. The air-cooling speed at the 0-40m position is 8-10°C / s, and the position at 40-90m is naturally cooled to obtain SWRH82B wire rod.

[0090] Example 5

[0091] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 11.0 mm, and the composition contents are as follows by mass percentage: C 0.80%, Mn 0.60%, Si 0.21%, N 0.014%, Ti0.028%, Nb 0.016%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0092] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0093] S1. Raw material weighing: according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control, all scrap steel raw materials, ferrotitanium and ferroniobium are weighed; wherein ferrotitanium is FeTi70 and ferroniobium is FeNb70;

[0094] S2, electric furnace smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace. After the steel is melted into molten steel, ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0095] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0096] S4, continuous casting: The S3 refined molten steel is temperature controlled and then continuously poured. The temperature of the molten steel is 1600°C after temperature control to obtain 82B continuous casting slabs. The 82B continuous casting slabs are square slabs with a size of 150×150 mm.

[0097] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling. After being kept at 1120°C for 1h, rolling is performed. The starting rolling temperature is 1060°C, the rolling rate is 35m / s, the spinning temperature is 920°C, and after rolling, a 90m air-cooling line is used. The air-cooling speed at the 0-40m position is 8-10°C / s, and the position at 40-90m is naturally cooled to obtain SWRH82B wire rod.

[0098] Example 6

[0099] A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, wherein the diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 11.0 mm, and the composition contents are as follows by mass percentage: C 0.82%, Mn 0.82%, Si 0.29%, N 0.014%, Ti0.028%, Nb 0.016%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest are Fe and unavoidable impurities.

[0100] A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps:

[0101] S1. Raw material weighing: according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control, all scrap steel raw materials, ferrotitanium and ferroniobium are weighed; wherein ferrotitanium is FeTi70 and ferroniobium is FeNb70;

[0102] S2, electric furnace smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace. After the steel is melted into molten steel, ferrotitanium and ferroniobium are added to obtain primary molten steel;

[0103] S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag;

[0104] S4, continuous casting: The S3 refined molten steel is temperature controlled and then continuously poured. The temperature of the molten steel is 1600°C after temperature control to obtain 82B continuous casting slabs. The 82B continuous casting slabs are square slabs with a size of 150×150 mm.

[0105] S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling. After being kept at 1100℃ for 1h, rolling is carried out. The starting rolling temperature is 1050℃, the rolling rate is 34m / s, the spinning temperature is 925℃, and after rolling, a 90m air-cooling line is used. The air-cooling speed at 0-40m is 8-10℃ / s, and the position at 40-90m is naturally cooled to obtain SWRH82B wire rod.

[0106] Comparative Example 1

[0107] A 82B wire rod, the diameter of the 82B wire rod is 12-13 mm, and the composition content is as follows by mass percentage: C 0.82%, Mn 0.67%, Si 0.12%, N 0.010%, Ti 0.021%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest is Fe and unavoidable impurities.

[0108] The preparation method of the 82B wire rod comprises the following steps:

[0109] S1. Raw material weighing: weigh all scrap steel raw materials and ferrotitanium according to the chemical composition content of 82B wire rod; wherein ferrotitanium is FeTi70;

[0110] The remaining smelting, ladle refining, continuous casting and rolling processes are the same as those in Example 1.

[0111] Comparative Example 2

[0112] A 82B wire rod, the diameter of the 82B wire rod is 12-13 mm, and the composition content is as follows by mass percentage: C 0.81%, Mn 0.66%, Si 0.14%, N 0.012%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest is Fe and unavoidable impurities.

[0113] The preparation method of the 82B wire rod comprises the following steps:

[0114] S1. Raw material weighing: weigh the whole scrap steel raw material according to the chemical composition content of 82B wire rod

[0115] The remaining smelting, ladle refining, continuous casting and rolling processes are the same as those in Example 1.

[0116] The following performance tests were performed on the embodiments and comparative examples:

[0117] (1) Microstructure: The microstructure parameters of the SWRH82B wire rod of Example 1 and Comparative Examples 1 and 2 were measured according to the standards such as GB / T13298 Metal Microstructure Test Method, YB / T169 Metallographic Test Method for Solenite Content in High Carbon Steel Wire Rod, and YB / T 4411-2014 Method for Evaluating Central Martensite in High Carbon Steel Wire Rod. Figure 1-8 They are optical microstructure diagrams of Examples 1-6 and Comparative Examples 1-2, and the statistical results of specific microstructure parameters are shown in Table 1.

[0118] (2) Mechanical properties: The strength of Examples 1-6 and Comparative Examples 1-2 was tested according to the standard "GB / T 228.3-2019 Tensile Test of Metal Materials". The results are shown in Table 2.

[0119] The microstructural parameters of specific embodiments 1-6 and comparative examples 1 and 2 are compared as shown in Table 1 below, and the mechanical properties are compared as shown in Table 2 below:

[0120] Table 1

[0121] serial number Martensitic Grade Soxhlet ratio / % Pearlite interlamellar spacing / nm Pearlite ball size / μm Example 1 0 97.2 153.2 4.75 Example 2 0 96.2 156.3 5.42 Example 3 0 96.4 157.3 5.21 Example 4 0 95.9 158.9 5.31 Example 5 0 96.2 156.4 5.20 Example 6 0 96.3 167.8 5.16 Comparative Example 1 0 86.2 186.3 8.13 Comparative Example 2 0 85.3 187.6 9.23

[0122] Table 2

[0123] serial number Tensile strength / MPa Elongation after break / % Sectional shrinkage / % Work hardening rate Example 1 1321 12.9 39.1 0.211 Example 2 1316 12.3 35.1 0.213 Example 3 1295 12.4 37.2 0.215 Example 4 1269 12.3 36.5 0.216 Example 5 1286 12.5 38.2 0.216 Example 6 1301 12.4 36.2 0.214 Comparative Example 1 1156 8.9 26.5 0.218 Comparative Example 2 1136 7.1 18.9 0.232

[0124] The above scheme, the present invention proposes a titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod and a preparation method, which can solve the problem that the 82B wire rod in the prior art cannot effectively control the adverse effects of nitrogen on the performance of steel, specifically, micron-level square Ti (C, N) will reduce the plasticity of 82B. Although it can be improved by adding alloy elements, there are technical problems such as high alloy element cost and difficulty in accurately controlling the organizational structure; and there is also a technical problem that it can be improved through the preparation process, but it will make the operation process complicated, difficult to control, and there are many influencing factors that are difficult to adjust.

[0125] The present invention transforms the solid-solution nitrogen element in the steel into a (Ti, Nb) (C, N) precipitation phase by reasonably selecting the composite addition of Ti and Nb elements. Compared with adding only the Ti element, the composite addition of Ti and Nb elements refines the size of the precipitation phase, significantly reduces the content of micron-level square Ti (C, N) and improves the plasticity and toughness of 82B.

[0126] The present invention uses continuous casting to form billets and temperature-controlled cold rolling to control the rolling temperature and the spinning temperature to obtain a structure with a stable pearlite ball size and pearlite lamellar spacing. In addition, a controlled cooling method is used after rolling to quickly cool the pearlite balls and lamellars after spinning to avoid the appearance of network secondary cementite, and natural cooling after rapid cooling prevents the appearance of abnormal martensite structure.

[0127] Compared with the production of SWRH82B by an electric furnace using recycled steel raw materials without Ti and B nitrogen fixation, the present invention completely eliminates the plastic damage of the SWRH82B wire rod caused by excessively high N content, and also increases the tensile strength by 50-100 MPa.

[0128] The titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod prepared by the present invention has a tensile strength of 1250-1350 MPa, a cross-sectional shrinkage of 35-40%, an elongation after fracture of ≥12%, and a strain hardening index of ≤0.220.

[0129] In summary, compared with other traditional methods, the method of the present invention prepares titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod by reasonably selecting Ti and Nb composite addition, continuous casting into billets and temperature-controlled cold rolling, which not only reduces the particle size of carbonitrides, but also synergistically improves strength and plasticity; the method is simple and easy to operate, green and environmentally friendly, low in cost, short in process, high in efficiency, wide in application range, and conducive to large-scale industrial production and promotion.

[0130] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0131] In the present invention, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or multiple.

[0132] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0133] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, characterized in that: The diameter of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 11-12.5 mm, and the composition content is calculated by mass percentage as follows: C 0.80-0.85%, Mn 0.60-0.90%, Si 0.12-0.32%, N 0.010-0.015%, Ti 0.020-0.030%, Nb 0.010-0.015%, S≤0.025%, P≤0.025%, Cu≤0.20%, Ni≤0.20%; the rest is Fe and unavoidable impurities.

2. The titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to claim 1, characterized in that: In the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod, the pearlite interlamellar spacing is 150-170nm, the pearlite nodule size is 4.5-5.5μm, and the Soxhletization rate is ≥92%.

3. The titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to claim 1, characterized in that: The tensile strength of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod is 1250-1350 MPa, the cross-sectional shrinkage is 35-40%, the elongation after fracture is ≥12%, and the strain hardening index is ≤0.

220.

4. A method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to any one of claims 1 to 3, characterized in that: The preparation method of the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod comprises the following steps: S1. Raw material weighing: weigh all scrap steel raw materials, ferrotitanium and ferroniobium according to the chemical composition content of 82B wire rod of titanium-niobium composite microalloying and nitrogen control; S2, electric furnace nitrogen controlled smelting: After the raw materials in S1 are weighed, the whole scrap steel raw materials are smelted in an electric furnace, and ferrotitanium and ferroniobium are added to obtain primary molten steel; S3, ladle refining: transfer S2 molten steel to the ladle for deoxidation, add aluminum beans according to the deoxidation situation, and obtain refined molten steel and refined slag; S4, continuous casting into billets: the S3 refined molten steel is temperature controlled and continuously poured to obtain 82B continuous casting billets; S5. Temperature-controlled cold rolling: The S482B continuous casting billet is subjected to temperature-controlled cold rolling to obtain SWRH82B wire rod.

5. The method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to claim 4, characterized in that: S1 titanium iron is at least one of FeTi30, FeTi40 and FeTi70, and niobium iron is at least one of FeNb50, FeNb60 and FeNb70.

6. The method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to claim 4, characterized in that: S2 electric furnace heating temperature ≥1600℃.

7. The method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to claim 4, characterized in that: The temperature of S4 refined molten steel is controlled at 1600℃, and the continuous casting billet is a square billet with a size of 150×150mm.

8. The method for preparing the titanium-niobium composite microalloyed nitrogen-controlled 82B wire rod according to claim 4, characterized in that: The heating temperature of S5 steel billet is 1080-1120℃, the rolling temperature is 1040-1080℃, the wire drawing temperature is 900-940℃, and the rolling speed is 30-35m / s. After rolling, it is air-cooled by Stelmo air-cooling line with a total length of 90m. The air-cooling speed at 0-40m is 8-10℃ / s, and natural cooling is carried out at 40-90m.

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