An ultrahigh-strength high-carbon steel wire rod and a method for manufacturing the same

Abstract

The application discloses a kind of ultra-high strength high-carbon steel wire rod and preparation method thereof, wire rod includes the following mass percentage components: C:0.89%~0.93%, Si:0.10%~0.20%, Mn:0.25%~0.40%, P≤0.015%, S:0.0055%~0.017%, N:0.0015%~0.0045%, As:0.0008%~0.0025%, Cr:0.1%~0.3%, Ca:0.0002%~0.0008%, Mo:0.0010%~0.0040%, total oxygen:0.0010%~0.0030%, Als:0.0001%~0.0005%, and the balance is iron and inevitable impurities.The wire rod produced by the application has a reticular cementite precipitation level ≤1 grade, a reticular cementite thickness ≤500 nm, and a thickness standard deviation ≤50 nm.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials and metallurgy, and more particularly, to a kind of ultra-high strength high carbon steel wire rod and its preparation method. BACKGROUND

[0002] Ultra-high strength high carbon steel wire rod is widely used in the field of steel cord and steel wire rope. For ultra-high strength high carbon steel wire rod, the network cementite in the wire rod structure is a kind of brittle structure, and the existence of network cementite destroys the continuous and uniform deformation ability of the matrix, which is easy to cause stress concentration during drawing and plying, thereby causing wire breakage. At the same time, if there is network cementite structure in the core of the wire rod, the internal quality defects of the produced steel wire cannot be discovered in time and applied to engineering, which will bring serious safety hazards to the bearing capacity of the engineering. Therefore, in order to prevent the wire rod from breaking due to the excessive coarseness of the network cementite, it is necessary to strictly control the network cementite in the structure of the ultra-high strength high carbon steel wire rod.

[0003] In order to control the precipitation of network cementite, a lot of research has been done by technical personnel, for example, application No. 202110722840.9 discloses a network cementite elimination method for super eutectoid steel wire rod, which comprises: unwinding the super eutectoid steel wire rod with network cementite, the diameter of the wire rod is greater than or equal to 10 mm and the network cementite rating is less than or equal to 3.5 grade, or the diameter of the wire rod is less than 10 mm and the network cementite rating is less than or equal to 4 grade; then introducing it into a heating furnace and keeping it in the temperature equalizing section of the heating furnace for more than 4 min and less than 10 min, the temperature T of the temperature equalizing section is maintained at 100-150℃ above the Accm of the wire rod; transferring the wire rod from the heating furnace to the salt bath tank next to the heating furnace, and carrying out salt bath for 30-120 s, the temperature T of the molten salt in the salt bath tank is maintained at 80-120℃ below the Ar1 of the wire rod; after the wire rod leaves the salt bath tank, it is naturally air-cooled to room temperature, and the obtained wire rod has network cementite. This patent focuses on the control method of network cementite of wire rod, which mainly uses salt bath process to control the network cementite of wire rod, but the process cost is high.

[0004] Therefore, under the current situation of fierce market competition, it is of great significance to study how to economically solve the problem of network cementite control of ultra-high strength high carbon steel wire rod, so as to meet the application requirements of high-strength steel wire market customers. SUMMARY

[0005] The present application aims to overcome the above-mentioned defects existing in the prior art, and provides an ultra-high strength high carbon steel wire rod and its preparation method and application. Through the production process of "converter smelting + LF refining + continuous casting + continuous rolling + heating + rolling + cooling" combined with low-cost alloy design, the network cementite precipitation rating of the produced ultra-high strength high carbon steel wire rod is less than or equal to 1 grade, the thickness of the network cementite is less than or equal to 500 nm, and the thickness standard deviation is less than or equal to 50 nm.

[0006] Satisfy the user's drawing performance requirements of ultra-high strength high carbon steel wire rod.

[0007] To achieve the above object, the technical scheme of the present application is as follows:

[0008] An ultra-high strength high carbon steel wire rod, comprising the following components in mass percentage: C: 0.89%~0.93%, Si: 0.10%~0.20%, Mn: 0.25%~0.40%, P≤0.015%, S: 0.0055%~0.017%, N: 0.0015%~0.0045%, As: 0.0008%~0.0025%, Cr: 0.1%~0.3%, Ca: 0.0002%~0.0008%, Mo: 0.0010%~0.0040%, total oxygen: 0.0010%~0.0030%, Als: 0.0001%~0.0005%, and the balance being iron and inevitable impurities.

[0009] The present application also discloses a preparation method of the ultra-high strength high carbon steel wire rod, comprising the following steps: converter smelting, LF refining, continuous casting, continuous rolling, heating, wire rod rolling and wire rod cooling.

[0010] In the LF refining, the molten steel after tapping in the converter smelting is refined in the LF furnace, the LF furnace refining temperature is 1500℃~1550℃, and the refining time is 40min~55min.

[0011] In the continuous casting, the molten steel after the LF refining is continuously cast, the continuous casting tundish superheat is ≤25℃; the continuous casting crystallizer electromagnetic stirring current intensity is 400A~600A, and the frequency is 1Hz~4Hz; the intermittent electromagnetic stirring is adopted, the continuous stirring time is 10s~30s, and the interval time to continuous stirring time ratio is 0.40~0.55, so as to obtain the continuous casting billet.

[0012] In the continuous rolling, the continuous casting billet after the continuous casting process is continuously rolled, the total heating time of the continuous casting billet is 3.5h~4.5h, the soaking section temperature is 1200℃~1260℃, and the soaking section time is 40min~60min; the continuous casting billet opening rolling temperature is 950℃~1000℃, and the final rolling temperature is 800℃~850℃.

[0013] In the heating, the continuously rolled steel billet is heated through the heating furnace, the soaking section temperature is 1050℃~1155℃, the soaking time is 60min~80min, the temperature difference between the surface and the core of the continuously rolled billet is ≤40℃, and the temperature difference between the head and the tail of the continuously rolled billet is ≤50℃.

[0014] In the wire rod rolling, the continuously casted billets are subjected to high-pressure water descaling treatment, and then sequentially subjected to rough rolling, intermediate rolling, pre-precision rolling, precision rolling and double-module rolling.

[0015] In the wire rod cooling, the wire rod after wire drawing is subjected to cooling at a cooling speed of 10-20℃ / s to obtain the ultra-high strength high-carbon steel wire rod.

[0016] The implementation of the embodiment of the present application has the following beneficial effects:

[0017] (1) The present application can effectively improve the quality of the ultra-high strength high-carbon steel wire rod, and through the production process of “converter smelting + LF refining + continuous casting + continuous rolling + heating + rolling + cooling” combined with low-cost alloy design, the microstructure of the wire rod is optimized, and the ultra-high strength high-carbon steel wire rod with high strength, reduced network cementite and good drawing performance is produced.

[0018] (2) The ultra-high strength high-carbon steel wire rod produced by the production method provided by the present application has excellent drawing performance, the network cementite precipitation level is ≤1 level, the network cementite thickness is ≤500nm, and the thickness standard deviation is ≤50nm. It helps to reduce the wire breaking rate during drawing, improve the drawing production efficiency, meet the drawing performance requirements of the user for the wire rod, effectively avoid the wire breaking phenomenon during drawing of the wire rod, and significantly improve the product market competitiveness.

[0019] (3) The process of the present application is based on conventional production equipment, and has the characteristics of strong process applicability and control, without additional investment. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with specific embodiments, but in no way limits the present application.

[0021] I. Chemical composition and mechanical properties

[0022] The present application discloses an ultra-high strength high-carbon steel wire rod, which comprises the following components in mass percentage: C: 0.89%-0.93%, Si: 0.10%-0.20%, Mn: 0.25%-0.40%, P≤0.015%, S: 0.0055%-0.017%, N: 0.0015%-0.0045%, As: 0.0008%-0.0025%, Cr: 0.1%-0.3%, Ca: 0.0002%-0.0008%, Mo: 0.0010%-0.0040%, total oxygen: 0.0010%-0.0030%, Als: 0.0001%-0.0005%, and the balance is iron and unavoidable impurities.

[0023] Specifically, the mechanism of each alloy component in the wire rod of the present application is as follows:

[0024] Too low carbon content in the wire rod cannot meet the strength requirement of the user when drawing the steel wire, and too high carbon content will make the strength of the wire rod and the steel wire exceed the standard requirement; therefore, the carbon content is controlled in 0.89% to 0.93% in the application.

[0025] Silicon is the main deoxidizing element in the high carbon steel, and low silicon content will cause insufficient deoxidization of the molten steel; the silicon element is a ferrite strengthening element, and too high silicon content will reduce the drawing performance of the wire rod; therefore, the silicon content is controlled in 0.10% to 0.20% in the application.

[0026] Manganese element has the elements of controlling the strength and phase transition characteristics of the wire rod. Manganese element reduces the eutectoid transformation temperature of the steel, so that the pearlite transformation of the wire rod occurs in the low temperature zone. Manganese is also an element for increasing the strength of the wire rod. However, too high manganese content will significantly harden the wire rod, which is not conducive to improving the cold working performance of the wire rod. Therefore, the manganese content is controlled in 0.25% to 0.40% in the application.

[0027] Phosphorus is a harmful element in the steel, and the lower the content is, the better. In the application, the phosphorus content is ≤0.015%.

[0028] Sulfur forms MnS with manganese element in the steel, which plays a role in reducing the harm of other oxide and nitride inclusions in the steel. However, the content should not be too high. Coarse MnS inclusions reduce the drawing performance of the wire rod. Therefore, the sulfur content is controlled in 0.0055% to 0.017% in the application.

[0029] Nitrogen element significantly increases the work hardening of the wire rod in the drawing and torsion process, and therefore, the nitrogen content is controlled in 0.0015% to 0.0045% in the application.

[0030] Arsenic is easy to enrich at the grain boundary of the steel, which reduces the system energy and stabilizes the austenite. However, too high arsenic content in the steel will reduce the drawing performance of the wire rod. In the application, the arsenic content is controlled in 0.0008% to 0.0025%.

[0031] Calcium element has a modification effect on the inclusion composition in the steel, and Al2O3-CaO and CaS-MnS and complex inclusions are formed, and the inclusions are relatively round and small in size. In the application, the calcium element is controlled in the range of 0.0002% to 0.0008%.

[0032] Molybdenum element has a solid solution strengthening effect on ferrite, and also improves the stability of carbide, so it has a favorable effect on improving the strength of the steel. In the application, the molybdenum content is controlled in 0.0010% to 0.0040%.

[0033] The chromium element can play a role in controlling the pearlite interlamellar spacing of the wire rod, improving the tensile strength of the wire rod, improving the plasticity and drawing performance of the wire rod, and improving the corrosion resistance. Too high chromium content will significantly harden the wire rod during drawing. The chromium content in the present patent is controlled at 0.1% to 0.3%.

[0034] The acid-soluble aluminum controls the composition of inclusions in the steel to be in the low melting point region. In the present invention, the acid-soluble aluminum is 0.0001% to 0.0005%. The effect of oxygen element in the steel is similar to that of acid-soluble aluminum, and is controlled at 0.0010% to 0.0030%.

[0035] In a specific embodiment, the wire rod pearlite ball size is ≤23 μm; wherein the number of wire rod pearlite ball size ≥15 μm accounts for 10% to 15%.

[0036] In a specific embodiment, the number of local orientation difference ≥15° of the grains on both sides of the grain boundary in the wire rod organization accounts for 15% to 25%.

[0037] In a specific embodiment, the wire rod has a network of cementite precipitation level ≤1 level, a network of cementite thickness ≤500 nm, and a thickness standard deviation ≤50 nm.

[0038] II. Production process technology

[0039] The present application also discloses a preparation method of the ultra-high strength high-carbon steel wire rod according to any embodiment of the present application, comprising the following steps: converter smelting, LF refining, continuous casting, continuous rolling, heating, wire rod rolling and wire rod cooling.

[0040] Further, specifically comprising the following steps:

[0041] S1, in the converter smelting, scrap steel and molten iron are used as the furnace charge, and the mass percentage of scrap steel in the furnace charge is 3% to 10%.

[0042] S2, in the LF refining, the molten steel after tapping in the converter smelting is put into the LF furnace for refining treatment, the LF furnace refining temperature is 1500°C to 1550°C, and the refining time is 40 min to 55 min.

[0043] In a specific embodiment, in the LF refining, argon stirring is carried out during the refining period, the argon stirring intensity is 300 NL / min to 400 NL / min; and 18 min to 22 min before the end of the LF refining, the argon flow is adjusted to 100 NL / min to 250 NL / min.

[0044] S3, in the continuous casting, the molten steel treated by LF refining is continuously cast, the overheat of the tundish is ≤25℃; the current intensity of the electromagnetic stirring of the continuous casting crystallizer is 400A-600A, and the frequency is 1Hz-4Hz; the intermittent electromagnetic stirring is adopted, the continuous stirring time is 10s-30s, and the ratio of the interval time to the continuous stirring time is 0.40-0.55, so that the continuous casting billet is obtained.

[0045] S4, in the continuous rolling, the continuous casting billet discharged in the continuous casting process is continuously rolled, the total heating time of the continuous casting billet is 3.5h-4.5h, the temperature of the soaking section is 1200℃-1260℃, and the time of the soaking section is 40min-60min; the open rolling temperature of the continuous casting billet is 950℃-1000℃, and the finish rolling temperature is 800℃-850℃.

[0046] S5, in the heating, the continuous rolling billet is heated through a heating furnace, the temperature of the soaking section is 1050℃-1155℃, the soaking time is 60min-80min, the temperature difference between the surface and the core of the continuous rolling billet is ≤40℃, and the temperature difference between the head and the tail of the continuous rolling billet is ≤50℃.

[0047] S6, in the wire rod rolling, the continuous rolling billet is treated by high-pressure water descaling, and then sequentially passes through rough rolling, intermediate rolling, pre-precision rolling, precision rolling and double-module rolling.

[0048] In an embodiment, the descaling pressure of the high-pressure water descaling treatment is 13MPa-16MPa; the wire rod exit temperature of the pre-precision rolling is 900℃-950℃, the cooling water flow rate of the exit of the pre-precision rolling is 50m 3 / h-80m 3 / h; the entry temperature of the precision rolling is 900℃-930℃; the rolling temperature of the rolled piece when exiting the double-module rolling mill is 880℃-900℃, the cooling water flow rate of the exit of the double-module is 40m 3 / h-70m 3 / h, and the wire drawing temperature is 860℃-880℃.

[0049] S6, in the wire rod cooling, the wire rod is cooled at a cooling speed of 10℃ / s-20℃ / s after wire drawing, so that the ultra-high strength high-carbon steel wire rod is obtained.

[0050] Further, the application also discloses an application of the ultra-high strength high-carbon steel wire rod in preparing an ultra-high strength steel wire.

[0051] In an embodiment, the diameter of the steel wire is 1.7mm-1.8mm; the pearlite ball size of the steel wire is 10μm-15μm; the pearlite interlamellar spacing of the steel wire is 0.07μm-0.075μm; and the hardness difference of the steel wire cross section along the diameter direction is ≤30HV.

[0052] The following is a specific embodiment

[0053] Examples 1-6

[0054] The chemical composition, preparation process and performance parameters of the wire rod of examples 1-6 of the present application are shown in table 1.

[0055] Table 1 Chemical composition, preparation process and performance parameters of the wire rod of examples 1-6

[0056]

[0057]

[0058]

[0059] According to the above results, by controlling the process parameters of the steel wire rod with carbon content of 0.89% to 0.93%, reasonably designing the relevant parameters of continuous casting, continuous rolling heating, rolling and cooling process, the ultra-high strength high carbon steel wire rod produced has excellent drawing performance, the reticular cementite precipitation level is ≤1 grade, the reticular cementite thickness is ≤500nm, and the thickness standard deviation is ≤50nm, which helps to reduce the drawing breakage rate, improve the drawing production efficiency, meet the drawing performance requirements of the user for the wire rod, and the production method is efficient and low in cost without using salt bath process.

[0060] The above described examples only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as limiting the scope of the patent application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims.

Claims

1. An ultra-high strength high carbon steel rod characterized in that, Comprise the following components by mass percentage: C: 0.89%~0.93%, Si: 0.10%~0.20%, Mn: 0.25%~0.40%, P≤0.015%, S: 0.0055%~0.011%, N: 0.0021%~0.0045%, As: 0.0008%~0.0025%, Cr: 0.1%~0.3%, Ca: 0.0002%~0.0008%, Mo: 0.0023%~0.0040%, total oxygen: 0.0010%~0.0030%, Als: 0.0001%~0.0005%, and the balance of iron and inevitable impurities; The spheroidal graphite ball size of the wire rod is ≤23μm; wherein the number of spheroidal graphite ball size ≥15μm accounts for 10%~15%; The number of local orientation difference ≥15° of the grain boundary on both sides of the grain in the wire rod structure accounts for 15%~25%; The network cementite precipitation level of the wire rod is ≤1 level, the network cementite thickness is ≤500nm, and the thickness standard deviation is ≤50nm; The preparation method of the super-high-strength high-carbon steel wire rod comprises the following steps: converter smelting, LF refining, continuous casting, continuous rolling, heating, wire rod rolling and wire rod cooling; In the LF refining, the molten steel after tapping in the converter smelting is refined in the LF furnace, the LF furnace refining temperature is 1500℃~1550℃, and the refining time is 40min~55min; In the continuous casting, the molten steel refined by the LF refining is continuously cast, the continuous casting tundish superheat is ≤25℃; the continuous casting crystallizer electromagnetic stirring current intensity is 400A~600A, and the frequency is 1Hz~4Hz; the intermittent electromagnetic stirring is adopted, the continuous stirring time is 10s~30s, and the interval time to continuous stirring time ratio is 0.40~0.55, to obtain the continuous casting billet; In the continuous rolling, the continuous casting billet offline in the continuous casting process is continuously rolled, the total heating time of the continuous casting billet is 3.5h~4.5h, the soaking section temperature is 1200℃~1260℃, and the soaking section time is 40min~60min; the continuous casting billet opening rolling temperature is 950℃~1000℃, and the final rolling temperature is 800℃~850℃; In the heating, the continuously rolled steel billet is heated by a heating furnace, the soaking section temperature is 1050℃~1155℃, the soaking time is 60min~80min, the temperature difference between the surface and the core of the continuously rolled billet is ≤40℃, and the temperature difference between the head and the tail of the continuously rolled billet is ≤50℃; In the wire rod rolling, the continuously rolled steel billet is treated by high-pressure water descaling, and then sequentially passes through rough rolling, intermediate rolling, pre-precision rolling, precision rolling and double module rolling; In the wire rod cooling, the wire rod after wire drawing is cooled at a cooling speed of 10℃ / s~20℃ / s to obtain the super-high-strength high-carbon steel wire rod.

2. The ultra-high strength high carbon steel rod of claim 1, wherein, In the converter smelting, scrap steel and molten iron are used as furnace charge, and the mass percentage of scrap steel in the furnace charge is 3%~10%.

3. The ultra-high strength high carbon steel rod of claim 1, wherein, In the LF refining, argon stirring is carried out during the refining, and the argon stirring intensity is 300 NL / min to 400 NL / min; 18 min to 22 min before the end of the LF refining, the argon flow is adjusted to 100 NL / min to 250 NL / min.

4. The ultra-high strength high carbon steel rod of claim 1, wherein, In the wire rod rolling process, the descaling pressure of the high-pressure water descaling treatment is 13MPa to 16MPa; the wire rod exiting the pre-finishing rolling temperature is 900℃ to 950℃, and the cooling water flow rate exiting the pre-finishing rolling is 50m³ / h. 3 / h~80m 3 / h; the entry temperature into the finishing mill is 900℃~930℃; the rolling temperature of the rolled piece exiting the double-module mill is 880℃~900℃, and the cooling water flow rate exiting the double-module mill is 40m³ / h. 3 / h~70m 3 / h, spinning temperature 860℃~880℃.

Images