1100MPa high carbon steel wire rod for Z-shaped steel wire production and its production process

Abstract

The invention discloses a 1100MPa grade high carbon steel wire rod for producing Z-shaped steel wire and a production process thereof. The chemical composition of the wire rod is as follows: [C] 0.80% to 0.84%, [Si] 0.10% to 0.20%, [Mn] 0.55% to 0.60%, [P] ≤ 0.015%, [S] 0.0030% to 0.010%, total oxygen 0.0010% to 0.0020%, [Als] 0.0003% to 0.0012%, [Nb] 0.0001% to 0.0010%, [Co] 0.0004% to 0.0010%, and [Mg] 0.0002% to 0.0010%. The production process includes molten steel smelting and continuous casting, continuous casting billet heating and rolling, wire rod rolling, and wire rod cooling. Through chemical composition and process control, the wire rod tensile strength is 1040-1140MPa, and the area reduction rate is 25%-35%; the Widmanstatten structure is ≤1.0 level, and the banded structure is ≤1.0 level; the troostite content of the wire rod reaches 80%-90%, and the troostite content is ≤5%; the proeutectoid cementite of the wire rod is ≤0.5 level, and the thickness of the proeutectoid cementite is between 0.1 and 0.5μm, which meets the production requirements of users' Z-type steel wire.

Description

Technical Field

[0001] The invention relates to a 1100MPa high-carbon steel wire rod for producing Z-shaped steel wire and a production process thereof, belonging to the technical field of wire rods. Background Art

[0002] Z-shaped steel wire is widely used in cableways, bridges and offshore platform mooring cables. The deformation of the Z-shaped steel wire in the process of preparing the wire rod is large and uneven, which can easily lead to local stress concentration in the wire, forming microcracks and causing the wire to crack. Therefore, the quality requirements for the raw material wire rod in the preparation of Z-shaped steel wire are very stringent. With the tightening of national energy-saving and environmental protection policies, the raw materials for Z-shaped steel wire are also developing towards high strength. The 1100MPa grade high carbon steel wire rod used for Z-shaped steel wire has high strength, and the cracking tendency of the steel wire in the Z-shaped steel wire processing process is aggravated. It is necessary to carry out a comprehensive design in terms of chemical composition and organizational state to meet the user's requirements.

[0003] The Chinese patent application with application (patent) number CN201610622809.7 discloses "a method for producing high-strength Z-shaped steel wire". The raw material is produced by wire rod with a diameter of φ12.5mm, steel grade 82B, and a sorbite content of more than 85%. The total compression rate of the steel wire drawing is 77.6%. The drawing is produced by a nine-pass diameter drawing machine, the reel diameter is Φ1270mm, and the mold box uses a rotating mold box. The maximum speed of the finished reel is 2m / s. During the drawing process, the temperature of the steel wire on the first and second reels of the wire drawing machine does not exceed 90°C, and the temperature of the steel wire on the remaining reels does not exceed 120°C. All electrical connections are cut out. The steel wire of the present invention has good appearance quality, high tensile strength, greatly improved torsion and bending performance of the steel wire, and various mechanical properties meet the technical requirements.

[0004] The patent focuses on the processing technology of special-shaped steel wire and mentions the chemical composition and organizational state of the raw material wire rod. The organization of the wire rod shown in the patent is troostite, and its content reaches 85%. The above patent does not recognize the influence of Widmanstatten organization, banded organization, etc. on the deformation performance of 1100MPa grade high carbon steel wire rod for Z-shaped steel wire, nor does it make a new design of 1100MPa grade high carbon steel wire rod for Z-shaped steel wire from the perspective of chemical composition. Summary of the invention

[0005] The purpose of the present invention is to provide a 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production and a production process thereof. Through the design of chemical composition and production process, the chemical composition, tensile strength, area reduction rate, Widmanstatten structure, banded structure and other indicators of the wire rod meet the production requirements of users for high-strength Z-shaped steel wire.

[0006] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0007] The invention discloses a 1100MPa grade high carbon steel wire rod produced by a Z-shaped steel wire, wherein the chemical composition is as follows by mass percentage: [C] 0.80% to 0.84%, [Si] 0.10% to 0.20%, [Mn] 0.55% to 0.60%, [P] ≤ 0.015%, [S] 0.0030% to 0.010%, total oxygen 0.0010% to 0.0020%, [Als] 0.0003% to 0.0012%, [Nb] 0.0001% to 0.0010%, [Co] 0.0004% to 0.0010%, [Mg] 0.0002% to 0.0010%, and the balance is Fe and unavoidable impurities.

[0008] Furthermore, in the chemical composition of the wire rod, [Nb]+[Mg] is 0.0005% to 0.0016%.

[0009] Furthermore, the wire rod rolling diameter is 8-10 mm, the wire rod tensile strength is 1040-1140 MPa, and the area reduction rate is 25%-35%.

[0010] Furthermore, the wire rod Widmanstatten structure is ≤ level 1.0, and the banded structure is ≤ level 1.0.

[0011] Furthermore, the troostite content of the wire rod reaches 80% to 90%, and the troostite content is ≤5%.

[0012] Furthermore, the pro-eutectoid cementite of the wire rod is ≤0.5 level, and the thickness of the pro-eutectoid cementite is between 0.1 and 0.5 um.

[0013] A production process of 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production, including molten steel smelting and continuous casting, continuous casting billet heating and rolling, wire rod rolling, wire rod cooling, wherein:

[0014] Heating and rolling of continuous casting billet: The total heating time of continuous casting billet in the furnace is 3.5-4.4h; the temperature of the soaking section is controlled at 1200-1260℃, and the holding time is 40-50min; after heating, continuous casting billet is continuously rolled, and the final rolling temperature is controlled at 880-980℃;

[0015] Wire rod rolling: the total furnace time of continuous rolling billet is 150-160min, the temperature of soaking section is 1120-1150℃, and the holding time of soaking section is 40-55min; after heating, it goes through rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling and double module rolling, and then the wire rod spinning operation is carried out; the pre-finishing rolling temperature of wire rod is 985-1005℃, the finishing rolling temperature is 890-930℃, the double module temperature is 880-940℃, and the wire rod spinning temperature is controlled at 900-940℃;

[0016] Wire rod cooling: After spinning, the wire rod is cooled on an air-cooled roller, and the cementite precipitation start temperature of the wire rod is controlled at 730-760°C. In this temperature range, the cooling rate of the wire rod is controlled at 15-25°C / s. The supercooling degree of the wire rod austenite to pearlite phase transformation is controlled at 80-120°C, and the phase transformation time is controlled at 12-18s. The wire rod is mainly composed of troostite structure, and the content reaches 80%-90%.

[0017] Furthermore, the continuous rolling billet is heated to 900-930°C before soaking, and the pearlite content in the core of the billet is 10%-15%; the continuous rolling billet is heated to 1000-1020°C, and the austenite content in the core of the billet is 95%-100%.

[0018] Furthermore, the cross-sectional size of the continuous casting billet is (250-300) mm*(350-400) mm, the surface temperature of the edge of the continuous casting billet during the straightening process is 900-930°C, and the temperature of the corner of the continuous casting billet is 790-830°C; the cross-sectional size of the continuous rolling billet is (140-180) mm*(140-180) mm, and the austenite grain size is 35-80 μm.

[0019] Furthermore, the molten steel is smelted by molten iron + scrap steel, the proportion of scrap steel is 5% to 15%, and the oxygen activity of the molten steel after smelting is controlled at 70 to 140 ppm; LF refining is adopted after the molten steel is smelted, the refining time is controlled at 30 to 50 minutes, and the refining temperature is controlled at 1450 to 1560°C; argon stirring is carried out during the molten steel refining process, and the argon flow rate is controlled at 200 to 500NL / min.

[0020] Compared with the prior art, the beneficial effects of the present invention are: the wire rod produced by the patented technology of the present invention has a tensile strength of 1040-1140MPa, a surface reduction rate of 25%-35%; the Widmanstatten structure is ≤1.0 level, and the banded structure is ≤1.0 level; the troostite content of the wire rod reaches 80%-90%, and the troostite content is ≤5%; the proeutectoid cementite of the wire rod is ≤0.5 level, and the thickness of the proeutectoid cementite is between 0.1 and 0.5μm, which meets the production requirements of users for Z-type steel wire. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] The chemical composition design principles of the wire rod of the present invention are as follows (by mass percentage):

[0023] The chemical composition of the wire rod suitable for the present invention is as follows: [C] 0.80%~0.84%, [Si] 0.10%~0.20%, [Mn] 0.55%~0.60%, [P]≤0.015%, [S] 0.0030%~0.010%, total oxygen 0.0010%~0.0020%, [Als] 0.0003%~0.0012%, [Nb] 0.0001%~0.0010%, [Co] 0.0004%~0.0010%, [Mg] 0.0002%~0.0010%, [Nb]+[Mg] 0.0005%~0.0016%, and the balance is Fe and unavoidable impurities.

[0024] The tensile strength of the wire rod is 1040~1140MPa, and the surface shrinkage is 25%~35%.

[0025] The reasons for setting the chemical composition range of the wire rod of the present invention are as follows.

[0026] Carbon: Carbon is the main element that controls the strength of the wire rod. If the carbon content of the wire rod is too low, it cannot meet the strength requirements of the user for the steel wire. If the content is too high, the strength of the steel wire will exceed the user's requirements; at the same time, a higher carbon content will increase the wire breakage rate during the drawing process of the wire rod, and the user's scrap rate will increase. Therefore, the carbon content in the present invention is controlled at 0.80% to 0.84%.

[0027] Silicon: Silicon is the main deoxidizing element in high carbon steel. Low silicon content will result in insufficient deoxidation of the molten steel; excessive silicon content in the steel will cause coarse silicate inclusions to appear in the steel, which is easy to cause cracks between the inclusions and the matrix during the processing of the Z-shaped steel wire, resulting in cracking or breaking of the steel wire. Silicon increases the eutectoid transformation temperature of the steel, causes pearlite to transform in the high temperature zone, and makes the pearlite structure of the wire rod coarse, which is not conducive to the complex deformation of the Z-shaped steel wire. Therefore, the silicon content in the present invention is controlled at 0.10% to 0.20%.

[0028] Manganese: Manganese is an element that improves the strength of the wire, so that the steel wire meets the user's tensile strength requirements; manganese has the effect of reducing the eutectoid transformation temperature of steel, refining the pearlite structure of the wire rod, and improving the coordinated deformation ability of the wire rod at different parts during the Z-shaped steel wire processing. Therefore, the manganese content in the present invention is controlled at 0.55% to 0.60%.

[0029] Phosphorus: Phosphorus is easy to form band segregation in the wire rod, which reduces the coordinated deformation ability of different parts of the wire rod during the Z-shaped steel wire processing and causes cracking and breaking of the steel wire. Therefore, the phosphorus content in the present invention is controlled to be ≤0.015%.

[0030] Sulfur: A higher sulfur content in steel reduces the cold working performance of the wire rod and is prone to cause delamination and cracking of the wire rod during the Z-shaped steel wire processing process. Since MnS inclusions have good deformation ability, an appropriate amount of sulfur in the steel can reduce the harm of non-deformable inclusions in the steel and prevent the generation of micro cracks caused by inclusions. Therefore, the sulfur content in the present invention is controlled at 0.0030% to 0.010%.

[0031] Oxygen: When the oxygen content is low, the inclusions in the wire rod have a high melting point and poor deformation ability, and cracks are easy to appear between the inclusions and the matrix, which is not conducive to the processing of Z-shaped steel wire; when the oxygen content is high, the inclusions in the steel are large in size, which is easy to cause micro cracks in the process of wire rod processing Z-shaped steel wire, causing the steel wire to crack. Therefore, the total oxygen content of the wire rod in the present invention is controlled at 0.0010% to 0.0020%.

[0032] Acid-soluble aluminum: When the acid-soluble aluminum content in the wire rod is too low, the melting point of the inclusions in the steel is high, and the deformation ability of the inclusions decreases, which is not conducive to the processing of the Z-shaped steel wire. When the acid-soluble aluminum content is high, the Al2O3 content of the inclusions in the steel increases, which is easy to cause cracking during the processing of the Z-shaped steel wire. Therefore, the acid-soluble aluminum content of the present invention is controlled at 0.0003% to 0.0012%.

[0033] Niobium: Niobium element uses undissolved compounds to hinder the coarsening of steel billet grains during the heating process of the steel billet, ensuring that the wire rod structure meets the Z-type steel wire processing requirements. However, a higher niobium content causes severe work hardening of the wire rod during the steel wire processing process, and the coordinated deformation ability of different parts of the wire rod decreases, which easily leads to cracking and breaking of the steel wire. Therefore, the niobium content of the present invention is controlled at 0.0001% to 0.0010%.

[0034] Cobalt: Cobalt is dissolved in steel to improve its strength. However, the cobalt content in steel should not be too high to prevent the higher wire rod strength from reducing the drawing and deformation properties of the wire rod. Cobalt increases the precipitation temperature of proeutectoid ferrite, increases the transformation temperature of austenite to pearlite, inhibits the appearance of Widmanstätten structure in the wire rod, reduces the content of troostite in the wire rod, and improves the uniform deformation performance of the wire rod. Therefore, the cobalt content in the present invention is controlled at 0.0004% to 0.0010%.

[0035] Magnesium: Magnesium controls the oxygen content in steel and also controls the type of inclusions in steel. A higher magnesium content causes magnesium-aluminum spinel inclusions to appear in the steel, reducing the processing performance of the wire rod. An appropriate amount of magnesium content in steel improves the deformation performance of inclusions, expands the area with higher inclusion deformation, and is conducive to improving the coordinated deformation ability of the wire rod. Therefore, the magnesium content of the present invention is controlled at 0.0002% to 0.0010%.

[0036] In order to prevent the niobium and magnesium elements from not fully exerting their effects and to prevent excessive niobium and magnesium content from reducing the coordinated deformation capacity of the wire rod, the present invention controls [Nb] + [Mg] to 0.0005% to 0.0016%.

[0037] The production process of the wire rod comprises the following steps:

[0038] Liquid steel smelting and continuous casting: Liquid steel is smelted by molten iron + scrap steel, the proportion of scrap steel is 5% to 15%, and the oxygen activity of liquid steel after smelting is controlled at 70 to 140ppm. LF refining is adopted after molten steel smelting. The refining time of molten steel in LF furnace is controlled at 30 to 50min, and the refining temperature is controlled at 1450 to 1560℃. Argon stirring is carried out during the refining process of liquid steel, and the argon flow rate is controlled at 200 to 500NL / min. The refined liquid steel is continuously cast, and the cross-sectional size of the continuous casting billet is (250 to 300) mm*(350 to 400) mm. The surface temperature of the edge of the continuous casting billet during the straightening process is 900 to 930℃, and the temperature of the corner of the continuous casting billet is 790℃ to 830℃.

[0039] Heating and rolling of continuous casting billet: The total furnace time for continuous casting billet heating is 3.5-4.4h. The temperature of the soaking section is controlled at 1200-1260℃. The holding time of the billet soaking section is 40-50min. After heating, the continuous casting billet is continuously rolled, and the final rolling temperature is controlled at 880-980℃. The austenite grain size of the continuous rolling billet is 35-80μm;

[0040] Wire rod rolling: The total furnace time of the continuous rolling billet is 150-160 minutes, the temperature of the soaking section is 1120-1150°C, and the holding time of the soaking section of the continuous rolling billet is 40-55 minutes. Through the high-temperature diffusion of the billet, the segregation of elements such as carbon and manganese is reduced, and the grain size of the billet is controlled; the continuous rolling billet is heated to 900-930°C, and the pearlite content in the core of the billet is 10%-15%; the continuous rolling billet is heated to 1000-1020°C, and the austenite content in the core of the billet is 95%-100%. After the billet is heated, it is subjected to rough rolling, intermediate rolling, pre-finishing rolling, finishing rolling and double module rolling before the wire rod extrusion operation. The pre-finishing rolling temperature of the wire rod is 985-1005°C; the finishing rolling temperature is 890-930°C; the double module temperature is 880-940°C. The wire rod extrusion temperature is controlled at 900-940°C. The higher wire rod spinning temperature can increase the cooling speed of the wire rod on the air-cooled roller, laying the foundation for controlling the final structure of the wire rod. The wire rod rolling specification is 8 to 10 mm.

[0041] Wire rod cooling: After spinning, the wire rod is cooled on the air-cooled roller, and the cementite precipitation temperature of the wire rod is controlled at 730-760℃. In this temperature range, the cooling rate of the wire rod is controlled at 15-25℃ / s. The undercooling degree of the austenite to pearlite phase transformation of the wire rod is controlled at 80-120℃, and the phase transformation time is controlled at 12-18s. After final cooling, the wire rod cord steel wire rod is mainly composed of sorbite structure, with a content of 80%-90%, which is conducive to the user's wire drawing.

[0042] Examples of the present invention are described below.

[0043]

[0044]

[0045]

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production, characterized in that: The chemical composition of the wire rod is as follows by mass percentage: [C] 0.80% to 0.83%, [Si] 0.10% to 0.17%, [Mn] 0.55% to 0.58%, [P] ≤ 0.015%, [S] 0.0030% to 0.0092%, total oxygen 0.0010% to 0.0020%, [Als] 0.0003% to 0.0012%, [Nb] 0.0001% to 0.0010%, [Co] 0.0004% to 0.0010%, [Mg] 0.0002% to 0.0010%, [Nb] + [Mg] 0.0005% to 0.0016%, the balance is Fe and unavoidable impurities; the production process includes molten steel smelting and continuous casting, continuous casting billet heating and rolling, wire rod rolling, wire rod cooling, among which, Wire rod rolling: the total furnace time of continuous rolling billet is 150-160min, the temperature of soaking section is 1120-1150℃, and the holding time of soaking section is 40-55min; after heating, rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling are carried out, and the wire rod spinning operation is carried out; the pre-finishing rolling temperature of wire rod is 985-1005℃, the finishing rolling temperature is 890-930℃, the double module temperature is 880-940℃, and the wire rod spinning temperature is controlled at 900-940℃; Wire rod cooling: After spinning, the wire rod is cooled on an air-cooled roller. The cementite precipitation temperature of the wire rod is controlled at 730-760°C. In this temperature range, the cooling rate of the wire rod is controlled at 15-25°C / s. The supercooling degree of the austenite to pearlite phase transformation of the wire rod is controlled at 80-120°C, and the phase transformation time is controlled at 12-18s. The wire rod is mainly composed of troostite structure, and the content reaches 80%-90%.

2. The 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 1, characterized in that: The rolled wire rod diameter is 8 to 10 mm, the wire rod tensile strength is 1040 to 1140 MPa, and the surface reduction rate is 25% to 35%.

3. The 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 1, characterized in that: The wire rod Widmanstatten structure is ≤1.0 level, and the banded structure is ≤1.0 level.

4. The 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 1, characterized in that: The troostite content of the wire rod reaches 80% to 90%, and the troostite content is ≤5%.

5. The 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 1, characterized in that: The proeutectoid cementite of the wire rod is ≤0.5 level, and the thickness of the proeutectoid cementite is between 0.1 and 0.5um.

6. A production process of 1100 MPa grade high carbon steel wire rod for Z-shaped steel wire production according to any one of claims 1 to 5, comprising molten steel smelting and continuous casting, continuous casting billet heating and rolling, wire rod rolling, and wire rod cooling, characterized in that: Heating and rolling of continuous casting billet: The total heating time of continuous casting billet in the furnace is 3.5-4.4h; the temperature of the soaking section is controlled at 1200-1260℃, and the holding time is 40-50min; after heating, continuous casting billet is continuously rolled, and the final rolling temperature is controlled at 880-980℃; Wire rod rolling: the total furnace time of continuous rolling billet is 150-160min, the temperature of soaking section is 1120-1150℃, and the holding time of soaking section is 40-55min; after heating, rough rolling, intermediate rolling, pre-finishing rolling and finishing rolling are carried out, and the wire rod spinning operation is carried out; the pre-finishing rolling temperature of wire rod is 985-1005℃, the finishing rolling temperature is 890-930℃, the double module temperature is 880-940℃, and the wire rod spinning temperature is controlled at 900-940℃; Wire rod cooling: After spinning, the wire rod is cooled on an air-cooled roller. The cementite precipitation temperature of the wire rod is controlled at 730-760°C. In this temperature range, the cooling rate of the wire rod is controlled at 15-25°C / s. The supercooling degree of the austenite to pearlite phase transformation of the wire rod is controlled at 80-120°C, and the phase transformation time is controlled at 12-18s. The wire rod is mainly composed of troostite structure, and the content reaches 80%-90%.

7. The production process of 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 6, characterized in that: The continuous rolled billet is heated to 900-930°C before soaking, and the pearlite content in the core of the billet is 10%-15%; the continuous rolled billet is heated to 1000-1020°C, and the austenite content in the core of the billet is 95%-100%.

8. The production process of 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 6, characterized in that: The cross-sectional size of the continuous casting billet is (250-300) mm*(350-400) mm, the surface temperature of the edge of the continuous casting billet during the straightening process is 900-930°C, and the temperature of the corner of the continuous casting billet is 790-830°C; the cross-sectional size of the continuous rolling billet is (140-180) mm*(140-180) mm, and the austenite grain size is 35-80 μm.

9. The production process of 1100MPa grade high carbon steel wire rod for Z-shaped steel wire production according to claim 6, characterized in that: The molten steel is smelted by molten iron + scrap steel, the proportion of scrap steel is 5% ~ 15%, and the oxygen activity of the molten steel after smelting is controlled at 70 ~ 140ppm; LF refining is adopted after smelting of the molten steel, the refining time is controlled at 30 ~ 50min, and the refining temperature is controlled at 1450 ~ 1560℃; argon stirring is carried out during the molten steel refining process, and the argon flow rate is controlled at 200 ~ 500NL / min.

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