Fatigue-resistant high-carbon steel wire and method of manufacturing the same

Abstract

The present application discloses a kind of fatigue-resistant high-carbon steel wire, it contains Fe and inevitable impurities, in addition also contains the following each chemical element with mass percentage content as follows: C:0.60~0.90%, Si:1.00~3.00%, Mn:0.45~1.00%, Cr:0.45~1.00%, Ni:0.10~0.30%, Ti:0.01~0.20%, Cu:0.05~0.50%, (La+Ce):0.01~0.10%. Correspondingly, the present application also discloses the manufacturing method of the above wire rod.The present application can obtain excellent fatigue resistance based on high-carbon steel by reasonable chemical composition design and organization control.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of steel and its preparation method, and more particularly to a kind of wire rod and its preparation method. BACKGROUND

[0002] Hardness, fatigue performance is the important index for judging the pros and cons of steel material, in general, the higher the hardness, the better the wear resistance of material, and the product service life is higher.On the other hand, many mechanical tool parts, in addition to having high hardness, due to the torsional shear force for a long time, there is a certain requirement for torsional fatigue performance.

[0003] At present, the torsional fatigue performance of steel material research mainly concentrates in the field of low carbon steel, and the research on high carbon steel is less.

[0004] For example, the publication number CN 110760748 A, the publication date is February 7, 2020, and the name is "a spring steel with excellent fatigue life and its manufacturing method", Chinese patent document, discloses a kind of spring steel with excellent fatigue life and its manufacturing method, the material alloy composition is: C: 0.52~0.62%, Si: 1.20~1.45%, Mn: 0.25~0.75%, Cr: 0.30~0.80%, V: 0.01~0.15%, Nb: 0.001~0.05%, N: 0.001~0.009%, O: 0.0005~0.0040%, P≤0.015%, S≤0.015%, Al≤0.0045%, while satisfying 0.02≤(2Nb+V) / (20N+C)≤0.40.However, the carbon content of this technical solution is low, and the torsional performance is not involved.

[0005] For example, the publication number CN107419175A, the publication date is December 1, 2017, and the name is "economic tool steel with good fatigue life and its production method", Chinese patent document, discloses a kind of economic tool steel production method with good fatigue life, the material alloy composition is: C: 0.75~1.00%, Si: 0.15~0.35%, Mn: 0.50~1.20%, Cr: 0.30~1.10%, V: 0.05~0.20%, Alt≤0.040%, P≤0.020%, S≤0.010%, N≤0.006%, after hot rolling annealing, obtain uniform granular pearlite structure, after quenching, tempering, obtain fine tempered martensite structure.However, this technical solution is only suitable for plate, and is not suitable for wire rod. SUMMARY

[0006] One of the purposes of the present application is to provide a kind of fatigue-resistant high-carbon steel wire, which is based on high-carbon steel, and by optimizing the design of alloy composition, it realizes the regulation of organization by specific process, so as to obtain excellent torsional fracture resistance, which can be effectively applied to high-end products in mechanical industry.

[0007] In order to achieve the above-mentioned purpose, the present application provides a kind of fatigue-resistant high-carbon steel wire, which contains Fe and inevitable impurities, and further contains the following chemical elements with mass percentage as follows:

[0008] C: 0.60-0.90%, Si: 1.00-3.00%, Mn: 0.45-1.00%, Cr: 0.45-1.00%, Ni: 0.10-0.30%, Ti: 0.01-0.20%, Cu: 0.05-0.50%, (La+Ce): 0.01-0.10%.

[0009] Further, the present application also provides a kind of fatigue-resistant high-carbon steel wire, and the mass percentage of each chemical element is as follows:

[0010] C: 0.60-0.90%, Si: 1.00-3.00%, Mn: 0.45-1.00%, Cr: 0.45-1.00%, Ni: 0.10-0.30%, Ti: 0.01-0.20%, Cu: 0.05-0.50%, (La+Ce): 0.01-0.10%; the balance is Fe and other inevitable impurities.

[0011] In the fatigue-resistant high-carbon steel wire described in the present application, the design principle of each chemical element is as follows:

[0012] C: In the fatigue-resistant high-carbon steel wire described in the present application, C is the most important element, on the one hand, C element in steel can play a solid solution strengthening effect, on the other hand, C element can form various carbides. It should be noted that when the content of C element in steel is too low, it is difficult to ensure the hardness and wear resistance of steel; while when the content of C element in steel is too high, it will adversely affect the toughness of steel, making the segregation difficult to control, increasing the difficulty of smelting and rolling, and easy to produce abnormal organization such as reticular carbide. Considering the influence of C element on the performance of fatigue-resistant high-carbon steel wire in the present technical solution, the mass percentage of C in the fatigue-resistant high-carbon steel wire described in the present application is controlled between 0.60-0.90%.

[0013] Si: In the fatigue-resistant high-carbon steel wire rod described in the present application, Si is a non-carbide-forming element. Si has a strong solid solution strengthening effect in steel, which can effectively improve the hardness of tool steel. However, it should be noted that the content of Si in steel should not be too high, because too high content of Si in steel will reduce the toughness of the steel. Therefore, in the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of Si is controlled between 1.00-3.00%.

[0014] Mn: In the fatigue-resistant high-carbon steel wire rod described in the present application, Mn can effectively improve the hardenability of steel, improve the stability of austenite, delay pearlite transformation, and improve impact toughness. Considering the requirement of hardenability of the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of Mn is controlled between 0.45-1.00%.

[0015] Cr: In the fatigue-resistant high-carbon steel wire rod described in the present application, Cr can effectively improve the hardenability, hardenability and tempering stability of steel. As a carbide-forming element, Cr can form carbides with C in steel and also can be solid-solution strengthened in ferrite. Therefore, considering its strengthening effect and production cost, in the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of Cr is controlled between 0.45-1.00%.

[0016] Ni: In the fatigue-resistant high-carbon steel wire rod described in the present application, the main role of Ni in steel is to reduce the brittle transition temperature at low temperature, which can improve the strength of steel without significantly reducing the toughness, and also can improve the corrosion resistance of steel, reduce the notch sensitivity of steel and improve the fatigue performance. Considering the beneficial effects of Ni and cost, in the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of Ni can be controlled between 0.10-0.30%.

[0017] Ti: In the fatigue-resistant high-carbon steel wire rod described in the present application, Ti can be added as a micro-alloying element in steel, as a strong carbonitride-forming element, which mainly plays a role in refining grains, which can improve the hardness of steel while improving the toughness. Therefore, in the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of Ti can be controlled between 0.01-0.20%.

[0018] Cu: In the fatigue-resistant high-carbon steel wire rod described in the present application, Cu can improve the corrosion resistance of steel, but too high content of Cu will lead to decrease of hot workability and manufacturability of steel. Therefore, in the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of Cu can be controlled between 0.05-0.50%.

[0019] La, Ce: In the fatigue-resistant high-carbon steel wire rod described in the present application, La and Ce have purifying and obvious modifying effects. The cleanliness of the steel is continuously improved, and the micro-alloying effect of rare earth elements is increasingly prominent. The micro-alloying of rare earth includes the solid solution strengthening of trace rare earth elements, the interaction of rare earth elements with other solute elements and compounds, the existence state, size, morphology and distribution of rare earth elements, especially the segregation at grain boundaries, and the influence of rare earth on the surface and matrix structure of the steel. In the fatigue-resistant high-carbon steel wire rod described in the present application, the mass percentage of (La+Ce) can be controlled to be 0.01-0.10%.

[0020] Further, in the fatigue-resistant high-carbon steel wire rod described in the present application, among other unavoidable impurities: P≤0.015%, S≤0.015%.

[0021] Under the condition that the technical conditions permit, in order to obtain a steel material with better performance and higher quality, the content of impurity elements in the fatigue-resistant high-carbon steel wire rod should be reduced as much as possible. In the present application, the unavoidable impurities are mainly P and S. Both impurity elements P and S are prone to segregation at grain boundaries, which reduces the toughness of the steel and has a greater impact on the cold working performance of the steel. Based on this, in some embodiments, P≤0.015% and S≤0.015% can be controlled.

[0022] Further, in the fatigue-resistant high-carbon steel wire rod described in the present application, the microstructure in the hot-rolled state is upper bainite + martensite.

[0023] Further, in the fatigue-resistant high-carbon steel wire rod described in the present application, the microstructure after isothermal heat treatment of quenching and tempering is lower bainite.

[0024] Further, the torsional strength of the fatigue-resistant high-carbon steel wire rod described in the present application is >1700 MPa, and the torsional fatigue life is >10000 times.

[0025] Another object of the present application is to provide a manufacturing method of a fatigue-resistant high-carbon steel wire rod, which adopts a relatively simple processing process and can obtain a wire rod with excellent fatigue resistance.

[0026] Based on the above object, the present application also provides a manufacturing method of a fatigue-resistant high-carbon steel wire rod, which comprises the following steps:

[0027] smelting and casting;

[0028] rolling into a rod;

[0029] Stelmor fan cooling: the cooling rate of the rod is controlled to be 0.3-2 ℃ / s by using a Stelmor air cooling line;

[0030] spheroidizing annealing;

[0031] drawing.

[0032] The manufacturing method of the fatigue-resistant high-carbon steel wire rod according to the present application can obtain the wire rod with a diameter of 5.5-28 mm by means of smelting, casting, rolling into a wire rod and controlling the cooling technology in combination with the alloy component design.

[0033] In the present application, the cooling rate of the wire rod is controlled to be 0.3-2 ℃ / s by adopting the slow cooling measures of the Stelmor fan cooling after rolling into a wire rod.

[0034] In some embodiments, the specific operation can be: closing all the fans and covering the heat preservation cover by means of the Stelmor air cooling line.

[0035] Further, in the manufacturing method according to the present application, the time of the wire rod in the heat preservation cover is controlled to be 600-800 s and the temperature of the wire rod out of the heat preservation cover is controlled to be 540-780 ℃ in the Stelmor fan cooling step. At this time, the hot-rolled state structure of the wire rod is upper bainite + martensite.

[0036] Then, the fatigue-resistant high-carbon steel wire rod can be obtained by spheroidizing annealing and drawing process.

[0037] Further, in the manufacturing method according to the present application, the drawing step is followed by a quenching and tempering isothermal heat treatment, in which the wire rod is heated to an austenitizing temperature of 820-960 ℃, kept for 0.5-1 h, then cooled to an isothermal temperature in a salt bath for isothermal treatment, wherein the isothermal temperature is 200-400 ℃ and the isothermal time is 2-5 h.

[0038] Further, in the manufacturing method according to the present application, the cooling speed in the salt bath is 10-50 ℃ / s.

[0039] The fatigue-resistant high-carbon steel wire rod with a torsional strength of > 1700 MPa and a torsional fatigue life of > 10000 times can be obtained by subsequent quenching and tempering isothermal heat treatment.

[0040] The fatigue-resistant high-carbon steel wire rod according to the present application has the following advantages and beneficial effects:

[0041] The fatigue-resistant high-carbon steel wire rod according to the present application can obtain excellent fatigue resistance based on high-carbon steel, and can achieve a torsional strength of > 1700 MPa and a torsional fatigue life of > 10000 times, thereby effectively applying to high-end products in the mechanical industry, filling the gap in the domestic market in this field and improving the processing level of the mechanical industry. DETAILED DESCRIPTION

[0042] The fatigue-resistant high-carbon steel wire rod and the manufacturing method thereof according to the present application will be further explained and described below in combination with specific embodiments, however, the explanation and description do not constitute undue limitation on the technical solutions of the present application.

[0043] The fatigue-resistant high-carbon steel wires of Examples 1-8 were prepared by the following steps:

[0044] (1) Smelting and casting.

[0045] (2) Rolling into a wire rod: the wire rod specification is φ5.5-28mm, and the chemical composition is shown in Table 1.

[0046] (3) Stelmor fan cooling: all the fans are closed and covered with a heat preservation cover to control the cooling rate of the wire rod to be 0.3-2℃ / s; the time of the wire rod in the heat preservation cover is controlled to be 600-800s, and the temperature of the wire rod out of the heat preservation cover is 540-780℃.

[0047] (4) Offline spheroidizing annealing: the wire rod is heated to 760-840℃ with the furnace, and is kept for 4-6h, and then is cooled to 710-750℃ at a speed of 10-50℃ / h, and is kept for 4-7h, and then is cooled to below 600℃ at a speed of 10-50℃ / h and is discharged.

[0048] (5) Drawing.

[0049] (6) Quenching and tempering isothermal heat treatment: the wire rod is heated to an austenitizing temperature of 820-960℃, and is kept for 0.5-1h, and then is quickly put into a salt bath and cooled to an isothermal temperature for isothermal treatment, the isothermal temperature is 200-400℃, and the isothermal time is 2-5h.

[0050] In some embodiments, the cooling speed of the wire rod in the salt bath is 10-50℃ / s.

[0051] Table 1 lists the mass percentage of each chemical element of the fatigue-resistant high-carbon steel wires of Examples 1-8.

[0052] Table 1. (wt%, the balance is Fe and other unavoidable impurities except P and S)

[0053]

[0054]

[0055] Table 2 lists the specific process parameters of the fatigue-resistant high-carbon steel wires of Examples 1-8 in the above steps.

[0056] Table 2.

[0057]

[0058] The wires of Examples 1-8 are sampled in their hot-rolled state and quenched and tempered state respectively, and the microstructure analysis is carried out by using the metal microstructure testing method (GB / T 13298-201), and it is found that the microstructure of the hot-rolled state is upper bainite + martensite. The microstructure after the quenching and tempering isothermal heat treatment is lower bainite.

[0059] In addition, the fatigue-resistant high-carbon steel wires of Examples 1-8 after the quenching and tempering isothermally treated by the above process steps are sampled respectively, and relevant performance tests are carried out, and the obtained performance test results are listed in Table 3.

[0060] The specific detection method is as follows: according to the relevant provisions of GB / T 10128-2007 "Metallic Materials Room Temperature Torsion Test Method", the test sample size is φ7mm, the total length is 150mm, the gauge length is 50mm, the torsion speed is 30° / min, and the test temperature is room temperature.

[0061] Table 3 lists the relevant performance test results of the fatigue-resistant high-carbon steel wires of Examples 1-8.

[0062] Table 3.

[0063]

[0064]

[0065] As shown in Table 3, the torsional strength of the wires in Examples 1-8 is all >1700MPa, and the fatigue frequency is all >10000 times. This shows that it not only has good torsional strength, but also has quite excellent fatigue resistance. Therefore, the fatigue-resistant high-carbon steel wire of the present application has significant advantages in torsional strength and fatigue resistance, and can be effectively applied to high-end products in the mechanical industry.

[0066] In addition, the combination mode of each technical feature in the present application is not limited to the combination mode described in the claims of the present application or the combination mode described in the specific embodiments, and all the technical features described in the present application can be freely combined or combined in any mode, unless contradictory to each other.

[0067] It should also be noted that the above-mentioned examples are only specific embodiments of the present application. Obviously, the present application is not limited to the above examples, and similar changes or modifications made from the content disclosed in the present application are directly derived or easily conceived by those skilled in the art, and should all belong to the protection scope of the present application.

Claims

1. A fatigue resistant high carbon steel wire, characterized by, The mass percentage of each chemical element is: C: 0.60-0.90%, Si: 1.00-3.00%, Mn: 0.45-1.00%, Cr: 0.45-1.00%, Ni: 0.10-0.30%, Ti: 0.01-0.20%, Cu: 0.05-0.50%, (La+Ce): 0.01-0.10%; The balance is Fe and other inevitable impurities; The hot-rolled microstructure of the fatigue-resistant high-carbon steel wire rod is upper bainite + martensite, and the microstructure after quenching and tempering isothermal heat treatment is lower bainite; The torsional strength of the fatigue-resistant high-carbon steel wire rod is > 1700 MPa, and the torsional fatigue life is > 10,000 times.

2. The fatigue resistant high carbon steel wire of claim 1, wherein, Among the other inevitable impurities: P ≤ 0.015%, S ≤ 0.015%.

3. The method of manufacturing a fatigue-resistant high-carbon steel wire rod according to any one of claims 1-2, characterized in that, It includes the steps of: Smelting and casting; Rolled into a rod; Stelmor fan cooling: the cooling rate of the rod is controlled to be 0.3-2 ℃ / s by using a Stelmor air cooling line; Spheroidizing annealing; Drawing.

4. The production method according to claim 3, wherein After the drawing step, it further includes quenching and tempering isothermal heat treatment: the wire rod is heated to an austenitizing temperature of 820-960 ℃, held for 0.5-1 h, then cooled in a salt bath to an isothermal temperature for isothermal treatment, wherein the isothermal temperature is 200-400 ℃, and the isothermal time is 2-5 h.

5. The production method according to claim 4, wherein In the Stelmor fan cooling step, the time of the rod in the holding cover is controlled to be 600-800 s, and the temperature out of the holding cover is 540-780 ℃.

6. The production method according to claim 4, wherein The cooling speed in the salt bath is 10-50 ℃ / s.

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