Production process of a non-repairing medium-carbon alloy spring steel wire and spring steel wire

Abstract

The application relates to the technical field of spring steel wire rods, and particularly discloses a production process of a free-grinding medium-carbon alloy spring steel wire rod and the spring steel wire rod. The production process comprises the following steps: S1, continuously casting to obtain a round billet; S2, heating to obtain a hot round billet; S3, rolling to obtain a primary product; and S4, cooling to obtain a spring steel wire rod. The production process does not need to perform processes such as grinding, spraying or flame peeling on the billet, the large-section round billet is selected, the compression ratio is improved, the weak oxidizing gas and the positive pressure low-temperature heating are matched, and the interaction of the one-time cooling and the heat preservation treatment not only simplifies the process and reduces the cost, but also makes the decarburization layer depth of the spring steel wire rod account for less than 0.3% of the diameter of the spring steel wire rod and the crack depth be less than or equal to 0.15 mm, so that the requirements are met, and remarkable economic benefits are obtained.

Description

Technical Field

[0001] This application relates to the field of spring steel wire technology, and more specifically, to a production process for a grind-free medium carbon alloy spring steel wire and the spring steel wire itself. Background Technology

[0002] Spring steel wire is generally made from medium-carbon alloy steel and high-carbon alloy steel. The medium-carbon alloy steel mainly consists of 60Si2MnA carbon alloy steel and 55SiCrA carbon alloy steel, both of which are silicon-manganese spring steel wires with high strength, elasticity, and hardenability. It is suitable for manufacturing helical springs that withstand large loads and have a wire diameter ≤30mm, as well as heat-resistant springs for non-corrosive media and operating temperatures ≤250℃. It is also suitable for manufacturing large coiled springs that withstand large pressures and alternating loads. Springs made from spring steel wire are widely used in automobiles, suspension systems, construction machinery, engines, and shock absorbers.

[0003] For springs, due to the alternating loads they withstand in the operating environment, high requirements are placed on the surface quality of both the springs and the spring steel wire, especially regarding decarburization layer defects and cracks. The presence of decarburization layer defects reduces surface hardness, making it prone to cracking under alternating stress, leading to premature fatigue failure. Generally, the decarburization layer depth should be ≤0.8% of the spring steel wire diameter. The presence of cracks causes stress concentration on the surface, lowering the fatigue limit and leading to early fatigue fracture. Generally, the crack depth should be ≤0.02mm.

[0004] In related technologies, application number CN202111444816X discloses a production control process for high surface quality 60Si2MnA spring steel, which includes continuous casting to obtain a steel billet, followed by grinding and flaw detection of the billet, with a grinding amount of 1.2-1.6 mm, and then spraying, heating, and rolling to obtain spring steel wire. CN201510630747X discloses a method for reducing the decarburized layer on the surface of high-carbon chromium bearing steel wire, which includes continuous casting to obtain a square billet with a square cross-section and a side length of 160 mm, then grinding the billet with a grinding amount of 0.5-2 mm, and then heating and rolling to obtain spring steel wire. Both of the above technical solutions reduce surface defects in the spring steel wire by grinding the steel billet, thereby reducing the depth of the decarburized layer and the crack depth. The mainstream domestic spring steel wire production process also reduces surface defects of steel billets by grinding or flame peeling, thereby reducing decarburization layer defects and crack defects on the surface of spring steel wire. However, this process is complex and has high input costs. Summary of the Invention

[0005] In order to simplify the production process of spring steel wire and reduce the decarburization layer depth and crack depth of spring steel wire, this application provides a production process and spring steel wire for medium carbon alloy spring steel wire that does not require grinding.

[0006] Firstly, this application provides a production process for grinding-free medium-carbon alloy spring steel wire, employing the following technical solution:

[0007] A production process for grinding-free medium carbon alloy spring steel wire includes the following steps:

[0008] S1. Continuous casting: molten steel is continuously cast to obtain round steel billets with a diameter ≥250mm.

[0009] S2. Heating: Under the conditions of weak oxidizing gas heating, gas excess coefficient of 1.05-1.10, and positive pressure of 5-40Pa, the round steel billet is heated to 1010-1070℃ and held for 100-135min to obtain hot round steel billet;

[0010] The oxygen content in the weak oxidizing gas is 1-2 wt%.

[0011] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 950-1000℃, a finishing rolling temperature of 880-935℃, and a wire drawing temperature of 860-900℃ to obtain the initial finished product.

[0012] S4. Cooling: The initial product is cooled once to 615-640℃ and held for 1.5-2.5 hours. Then it is cooled a second time to 250-300℃ and then cooled to room temperature to obtain spring steel wire with a diameter ≤20mm.

[0013] Optionally, in step S4, the cooling rate of the primary cooling is 14-16℃ / s, and the cooling rate of the secondary cooling is 1-3℃ / s.

[0014] The applicant discovered during actual processing that the corners of square steel billets are prone to a high concentration of inclusions, affecting strength and toughness. Furthermore, the corners are susceptible to deep vibration marks due to bending and straightening processes, impacting the integrity and smoothness of the billet and leading to surface defects. Additionally, decarburization is severe at the corners during heating. During rolling, the corners deform, resulting in lower temperatures on both sides and uneven deformation, which easily leads to folding cracks and cluster cracks, increasing the depth of the decarburized layer and crack depth on the spring steel wire rod surface.

[0015] In the production process of this application, round steel billets are used instead of square steel billets. Round steel billets have excellent chemical composition uniformity. Furthermore, during continuous casting, their small contact area with the second cooling roll reduces defects such as scratches and folds, thus lowering surface defects. Simultaneously, during heating, because they lack end corners and have a relatively small surface area to volume ratio, the decarburization during heating and oxidation is thinner and the decarburization depth is smaller. During rolling, due to their uniform chemical composition distribution, folding cracks and cluster cracks are less likely to occur, effectively reducing decarburization layer defects and crack defects generated during heating, rolling, and cooling.

[0016] Meanwhile, the production process of this application selects round steel billets with a diameter ≥250mm, which have a larger compression ratio and exhibit higher tolerance for decarburization layer defects and crack defects, allowing for direct rolling without grinding or flame peeling. Furthermore, the use of weak oxidizing gas and positive pressure low-temperature heating reduces the impact of oxygen on the surface defects of the round steel billet during heating. It also increases the primary cooling rate and performs heat preservation treatment after primary cooling, reducing the exposure time of the spring steel wire in the high-temperature region, which can also effectively reduce surface defects, making the decarburization layer depth of the spring steel wire ≤0.04mm, the percentage of the decarburization layer depth to the diameter of the spring steel wire <0.3%, and the crack depth ≤0.15mm.

[0017] The production process of this application does not require the investment of equipment such as billet grinding and flame peeling, nor does it require the grinding and flame peeling process of the billet. By selecting large cross-section round billets, increasing the compression ratio, and combining the interaction of weak oxidizing gas and positive pressure low temperature heating, as well as one-time cooling and heat preservation treatment, it not only simplifies the process and reduces costs, but also meets the requirements for decarburization layer defects and crack defects, resulting in significant economic benefits.

[0018] Optionally, the diameter of the round steel billet is 250-300mm, and the diameter of the spring steel wire is 6.5-20mm.

[0019] By adopting the above technical solutions, the diameter of round steel billets and the diameter of spring steel wire are optimized, thereby optimizing the compression ratio and the requirements for decarburization layer defects and crack defects in round steel billets. This facilitates the production of spring steel wire and increases production stability.

[0020] In several implementations, the diameter of the round steel billet is 250 mm, but it can also be set to 250 mm, 270 mm, 280 mm, 290 mm, 300 mm, etc., as needed. In several implementations, the diameter of the spring steel wire is 14 mm, but it can also be set to 6.5 mm, 10 mm, 15 mm, 20 mm, etc., as needed.

[0021] Optionally, the spring steel wire is one of 60Si2MnA carbon alloy steel or 55SiCrA carbon alloy steel.

[0022] Optionally, the molten steel is mainly composed of the following chemical composition by weight percentage: C: 0.54-0.60%, Si: 1.62-1.75%, Mn: 0.69-0.76%, Cr: 0.126-0.129%, Al≤0.015%, Ti≤0.004%, V≤0.005%, Ni≤0.02%, Cu≤0.25%, Mo≤0.02%, P≤0.01%, S≤0.01%, O≤0.0012%, H≤0.0002%, with the balance being Fe.

[0023] By adopting the above technical solution, the chemical composition of 60Si2MnA carbon alloy steel is optimized, which facilitates the production of spring steel wire.

[0024] Optionally, the molten steel is mainly composed of the following chemical composition by weight percentage: C: 0.54-0.56%, Si: 1.41-1.45%, Mn: 0.65-0.69%, Cr: 0.65-0.69%, Al≤0.015%, Ti≤0.004%, V≤0.005%, Ni≤0.02%, Cu≤0.25%, Mo≤0.02%, P≤0.01%, S≤0.01%, O≤0.0012%, H≤0.0002%, with the balance being Fe.

[0025] By adopting the above technical solution, the chemical composition of 55SiCrA carbon alloy steel is optimized, which facilitates the production of spring steel wire.

[0026] Optionally, the weakly oxidizing gas is blast furnace gas.

[0027] Optionally, the blast furnace gas contains 1-2 wt% oxygen, ≤10 wt% carbon dioxide, and ≤10 g / Nm³ of water. 3 .

[0028] By adopting the above technical solution, blast furnace gas is used as the weak oxidizing gas, which facilitates the selection of the weak oxidizing gas. Furthermore, the oxygen percentage, silica percentage, and water content in the blast furnace gas are limited to ensure the depth of the decarburized layer and crack depth on the surface of the spring steel wire, thereby increasing the stability of spring steel wire production.

[0029] Optionally, the temperature of the round steel billet is 550-590℃.

[0030] By adopting the above technical solution, the round steel billet can directly enter the heating process after being cooled to 550-590℃ during the continuous casting stage, without having to cool the round steel billet to 25℃ or 30℃, thus simplifying the process and reducing production costs.

[0031] Secondly, this application provides a spring steel wire, which adopts the following technical solution:

[0032] A spring steel wire, wherein the spring steel wire is manufactured by the aforementioned grinding-free medium carbon alloy spring steel wire production process.

[0033] In summary, this application has at least the following beneficial effects:

[0034] The production process for medium-carbon alloy spring steel wire rod without grinding, as described in this application, eliminates the need for equipment investment in billet grinding and flame peeling, as well as the need for such processes. By selecting large-section round billets, increasing the compression ratio, and combining weak oxidizing gas and positive pressure low-temperature heating with a single cooling and heat preservation treatment, the process is simplified and costs are reduced. Furthermore, the decarburized layer depth of the spring steel wire rod is ≤0.04mm, the percentage of the decarburized layer depth to the diameter of the spring steel wire rod is <0.3%, and the crack depth is ≤0.15mm, meeting the requirements and demonstrating significant economic benefits. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the round steel billet in Embodiment 1 of this application.

[0036] Figure 2 This is a decarburized metallographic image of the spring steel wire in Embodiment 2 of this application.

[0037] Figure 3 This is a decarburized metallographic image of the spring steel wire of Comparative Example 1 of this application. Detailed Implementation

[0038] To make this application easier to understand, the following detailed description will be provided with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of this application. Unless otherwise specified, the raw materials or components used in this application can be obtained commercially or by conventional methods.

[0039] In the process of rolling steel billets into steel wire rods, the decarburization layer depth and crack depth of the steel billet are inherited to the surface of the spring steel wire rod, and affect the decarburization layer depth and crack depth of the spring steel wire rod, and the following relationship exists:

[0040]

[0041] Wherein, d0 is the defect depth of the billet (either the decarburized layer depth or the crack depth);

[0042] d1 is the depth of inherited defects in spring steel wire (either the depth of the decarburized layer or the depth of the crack);

[0043] A0 is the area of ​​the cross-section of the steel billet;

[0044] A1 is the area of ​​the cross-section of the spring steel wire.

[0045] By combining the requirements for the decarburization layer depth and crack depth of spring steel wire, the requirements for the decarburization layer depth of steel billet can be obtained, as shown in Table 1. The requirements for the crack depth of steel billet can also be obtained, as shown in Table 2.

[0046] The square steel billet has a square cross-section, and the side length of the 160 square steel billet is 160mm, while the diameter of the 300 round steel is 300mm.

[0047] Table 1 Requirements for the Decarburization Layer Depth of Steel Billets

[0048]

[0049] Based on Table 1, a comparison between 160 square billets and 300 round billets shows that, while meeting the requirements for the decarburization layer depth in producing qualified spring steel wire, the 300 round billet has a higher tolerance for decarburization layer depth and a defect tolerance 1.38 times that of the 160 square billet.

[0050] Table 2 Requirements for Crack Depth in Steel Billets

[0051]

[0052]

[0053] Based on Table 2, a comparison is made between 160 square billets and 300 round billets. It can be seen that as the diameter of the processed spring steel wire increases, i.e. the compression ratio decreases, the required crack depth of the billet becomes higher. Furthermore, based on the requirement of obtaining qualified spring steel wire with the required crack depth, the 300 round billet has a higher tolerance for crack defects, and its defect tolerance is 1.38 times that of the 160 square billet.

[0054] Combining Tables 1 and 2, it can be seen that the 160mm square billet has a low tolerance for decarburization layer defects and crack defects. If the 160mm square billet is directly rolled, it may be difficult to meet the defect requirements of spring steel wire rod. Therefore, in the existing technology, the 160mm square billet is generally ground or flame-stripped before rolling to meet the defect requirements of spring steel wire rod. The 300mm round billet has a higher tolerance for decarburization layer defects and crack defects, and can be directly rolled without grinding or flame-stripping, while still meeting the requirements of spring steel wire rod.

[0055] Example

[0056] Example 1

[0057] A production process for grinding-free medium-carbon alloy spring steel wire, wherein the spring steel wire obtained is made of 60Si2MnA carbon alloy steel, specifically includes the following steps:

[0058] S1. Continuous Casting: Molten steel is continuously cast at a superheat temperature of 25℃ to obtain round steel billets with a diameter of 250mm. A schematic diagram of the round steel billet structure is shown below. Figure 1 As shown.

[0059] The molten steel is composed of the following chemical composition by weight percentage: C: 0.54%, Si: 1.75%, Mn: 0.76%, Cr: 0.129%, Al: 0.0097%, Ti: 0.0031%, V: 0.0047%, Ni: 0.01%, Cu: 0.02%, Mo: 0.0116%, P: 0.006%, S: 0.007%, O: 0.0010%, H: 0.00020%, with the balance being Fe.

[0060] S2. Heating: Using a one-in-one-out method, the round steel billet is transferred into the heating furnace at a temperature of 550℃. Then, under weak oxidizing gas heating, with a gas excess coefficient of 1.05 and a positive pressure of 15.5Pa, the round steel billet is heated to 1035℃ and held for 115 minutes to obtain a hot round steel billet.

[0061] The weakly oxidizing gas is blast furnace gas, which contains 1.5 wt% oxygen, 8.5 wt% carbon dioxide, and 6 g / Nm³ of water. 3 .

[0062] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 973℃, a finishing rolling temperature of 910℃, and a wire drawing temperature of 886℃ to obtain the initial finished product.

[0063] S4. Cooling: The initial product is cooled once with atomized water to 635℃ and kept at that temperature for 1.5 hours. Then, it is cooled a second time with cold air to 300℃, and then cooled to 25℃ to obtain spring steel wire with a diameter of 14mm.

[0064] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0065] Example 2

[0066] A production process for grinding-free medium-carbon alloy spring steel wire, wherein the spring steel wire obtained is made of 60Si2MnA carbon alloy steel, specifically includes the following steps:

[0067] S1. Continuous casting: Molten steel is continuously cast at an overheating temperature of 25°C to obtain round steel billets with a diameter of 250 mm.

[0068] The molten steel is composed of the following chemical composition by weight percentage: C: 0.56%, Si: 1.66%, Mn: 0.71%, Cr: 0.122%, Al: 0.0104%, Ti: 0.0033%, V: 0.0041%, Ni: 0.01%, Cu: 0.02%, Mo: 0.0114%, P: 0.003%, S: 0.007%, O: 0.0011%, H: 0.00020%, with the balance being Fe.

[0069] S2. Heating: Using a one-in-one-out method, the round steel billet is transferred into the heating furnace at a temperature of 25℃. Then, under weak oxidizing gas heating, with a gas excess coefficient of 1.05 and a positive pressure of 16Pa, the round steel billet is heated to 1027℃ and held for 120 minutes to obtain a hot round steel billet.

[0070] The weakly oxidizing gas is blast furnace gas, which contains 1.5 wt% oxygen, 9.5 wt% carbon dioxide, and 6 g / Nm³ of water. 3 .

[0071] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 995℃, a finishing rolling temperature of 915℃, and a wire drawing temperature of 883℃ to obtain the initial finished product.

[0072] S4. Cooling: The initial product is cooled once with atomized water to 630°C and kept at that temperature for 2 hours. Then, it is cooled a second time with cold air to 300°C, and then cooled to 25°C to obtain spring steel wire with a diameter of 14mm.

[0073] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0074] Example 3

[0075] A production process for grinding-free medium-carbon alloy spring steel wire, wherein the spring steel wire obtained is made of 60Si2MnA carbon alloy steel, specifically includes the following steps:

[0076] S1. Continuous casting: Molten steel is continuously cast at an overheating temperature of 25°C to obtain round steel billets with a diameter of 250 mm.

[0077] The molten steel is composed of the following chemical composition by weight percentage: C: 0.58%, Si: 1.62%, Mn: 0.69%, Cr: 0.126%, Al: 0.0047%, Ti: 0.0029%, V: 0.0044%, Ni: 0.01%, Cu: 0.02%, Mo: 0.0117%, P: 0.004%, S: 0.005%, O: 0.0009%, H: 0.00015%, with the balance being Fe.

[0078] S2. Heating: Using a one-in-one-out method, the round steel billet is transferred into the heating furnace at a temperature of 30℃. Then, under weak oxidizing gas heating, with a gas excess coefficient of 1.05 and a positive pressure of 12Pa, the round steel billet is heated to 1020℃ and held for 125 minutes to obtain a hot round steel billet.

[0079] The weakly oxidizing gas is blast furnace gas, which contains 1.5 wt% oxygen, 9.0 wt% carbon dioxide, and 6 g / Nm³ of water. 3 .

[0080] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 970℃, a finishing rolling temperature of 910℃, and a wire drawing temperature of 880℃ to obtain the initial finished product.

[0081] S4. Cooling: The initial product is cooled once with atomized water to 640℃ and kept at that temperature for 2.5 hours. Then, it is cooled a second time with cold air to 300℃, and then cooled to 25℃ to obtain spring steel wire with a diameter of 14mm.

[0082] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0083] Example 4

[0084] A production process for grinding-free medium-carbon alloy spring steel wire, wherein the spring steel wire obtained is made of 55SiCrA carbon alloy steel, specifically includes the following steps:

[0085] S1. Continuous casting: Molten steel is continuously cast at an overheating temperature of 25°C to obtain round steel billets with a diameter of 250 mm.

[0086] The molten steel is composed of the following chemical composition by weight percentage: C: 0.55%, Si: 1.41%, Mn: 0.68%, Cr: 0.67%, Al: 0.008%, Ti: 0.0016%, V: 0.0043%, Ni: 0.01%, Cu: 0.01%, Mo: 0.0035%, P: 0.009%, S: 0.007%, O: 0.0010%, H: 0.00016%, with the balance being Fe.

[0087] S2. Heating: Using a one-in-one-out method, the round steel billet is transferred into the heating furnace at a temperature of 30℃. Then, under weak oxidizing gas heating, with a gas excess coefficient of 1.10 and a positive pressure of 11Pa, the round steel billet is heated to 1020℃ and held for 118 minutes to obtain a hot round steel billet.

[0088] The weakly oxidizing gas is blast furnace gas, which contains 1.5 wt% oxygen, 8.0 wt% carbon dioxide, and 7 g / Nm³ of water. 3 .

[0089] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 985℃, a finishing rolling temperature of 930℃, and a wire drawing temperature of 895℃ to obtain the initial finished product.

[0090] S4. Cooling: The initial product is cooled once with atomized water to 620°C and kept at that temperature for 2.5 hours. Then, it is cooled a second time with cold air to 300°C, and then cooled to 25°C to obtain spring steel wire with a diameter of 15mm.

[0091] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0092] Example 5

[0093] A production process for grinding-free medium-carbon alloy spring steel wire, wherein the spring steel wire obtained is made of 55SiCrA carbon alloy steel, specifically includes the following steps:

[0094] S1. Continuous casting: Molten steel is continuously cast at an overheating temperature of 25°C to obtain round steel billets with a diameter of 250 mm.

[0095] The molten steel is composed of the following chemical composition by weight percentage: C: 0.56%, Si: 1.42%, Mn: 0.69%, Cr: 0.65%, Al: 0.0078%, Ti: 0.0016%, V: 0.0042%, Ni: 0.01%, Cu: 0.01%, Mo: 0.0024%, P: 0.009%, S: 0.006%, O: 0.0011%, H: 0.00018%, with the balance being Fe.

[0096] S2. Heating: Using a one-in-one-out method, the round steel billet is transferred into the heating furnace at a temperature of 590℃. Then, under weak oxidizing gas heating, with a gas excess coefficient of 1.05 and a positive pressure of 10Pa, the round steel billet is heated to 1017℃ and held for 100 minutes to obtain a hot round steel billet.

[0097] The weakly oxidizing gas is blast furnace gas, which contains 1.5 wt% oxygen, 9.0 wt% carbon dioxide, and 8 g / Nm³ of water. 3 .

[0098] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 990℃, a finishing rolling temperature of 934℃, and a wire drawing temperature of 874℃ to obtain the initial finished product.

[0099] S4. Cooling: The initial product is cooled once with atomized water to 619°C and kept at that temperature for 2 hours. Then, it is cooled a second time with cold air to 300°C, and then cooled to 25°C to obtain spring steel wire with a diameter of 15mm.

[0100] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0101] Example 6

[0102] A production process for grinding-free medium-carbon alloy spring steel wire, wherein the spring steel wire obtained is made of 55SiCrA carbon alloy steel, specifically includes the following steps:

[0103] S1. Continuous casting: Molten steel is continuously cast at an overheating temperature of 25°C to obtain round steel billets with a diameter of 250 mm.

[0104] The molten steel is composed of the following chemical composition by weight percentage: C: 0.54%, Si: 1.45%, Mn: 0.65%, Cr: 0.69%, Al: 0.0074%, Ti: 0.0014%, V: 0.0043%, Ni: 0.01%, Cu: 0.01%, Mo: 0.0019%, P: 0.009%, S: 0.006%, O: 0.0008%, H: 0.00019%, with the balance being Fe.

[0105] S2. Heating: Using a one-in-one-out method, the round steel billet is transferred into the heating furnace at a temperature of 30℃. Then, under weak oxidizing gas heating, with a gas excess coefficient of 1.05 and a positive pressure of 9Pa, the round steel billet is heated to 1017℃ and held for 110 minutes to obtain a hot round steel billet.

[0106] The weakly oxidizing gas is blast furnace gas, which contains 1.5 wt% oxygen, 9.0 wt% carbon dioxide, and 6 g / Nm³ of water. 3 .

[0107] S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 978℃, a finishing rolling temperature of 920℃, and a wire drawing temperature of 884℃ to obtain the initial finished product.

[0108] S4. Cooling: The initial product is cooled once with atomized water to 620°C and kept at that temperature for 1.5 hours. Then, it is cooled a second time with cold air to 300°C and then to 25°C to obtain spring steel wire with a diameter of 15mm.

[0109] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0110] Comparative Example

[0111] Comparative Example 1

[0112] A production process for a non-grinding medium carbon alloy spring steel wire, wherein the spring steel wire obtained by the process is made of 60Si2MnA carbon alloy steel, the difference between this process and Example 2 is that steps S1 and S4 are different.

[0113] Step S1 specifically involves: continuously casting molten steel at an overheating temperature of 25°C to obtain a square billet with a square cross-section and a side length of 160 mm.

[0114] Step S4 is as follows: the initial product is cooled once with atomized water to 630°C and kept at that temperature for 2 hours. Then, it is cooled a second time with cold air to 300°C and then cooled to 25°C to obtain spring steel wire with a diameter of 14mm.

[0115] The cooling rate for primary cooling is 10℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0116] Comparative Example 2

[0117] A production process for a non-grinding medium-carbon alloy spring steel wire, wherein the spring steel wire obtained by the process is made of 60Si2MnA carbon alloy steel, the difference from Example 2 is that step S1 is different.

[0118] Step S1 specifically involves: continuously casting molten steel at an overheating temperature of 25°C to obtain a square billet with a square cross-section and a side length of 160 mm.

[0119] Comparative Example 3

[0120] A production process for a non-grinding medium-carbon alloy spring steel wire, wherein the spring steel wire obtained by the process is made of 60Si2MnA carbon alloy steel, the difference from Example 2 is that step S1 is different.

[0121] Step S1 specifically involves: continuously casting molten steel at an overheating temperature of 25°C to obtain a square billet with a square cross-section and a side length of 230 mm.

[0122] Comparative Example 4

[0123] A production process for a non-grinding medium-carbon alloy spring steel wire, wherein the spring steel wire obtained by the process is made of 60Si2MnA carbon alloy steel, the difference from Example 2 is that step S4 is different.

[0124] Step S4 is as follows: the initial product is cooled once with atomized water to 630°C and kept at that temperature for 2 hours. Then, it is cooled a second time with cold air to 300°C and then cooled to 25°C to obtain spring steel wire with a diameter of 14mm.

[0125] The cooling rate for primary cooling is 10℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0126] Comparative Example 5

[0127] A production process for a non-grinding medium-carbon alloy spring steel wire, wherein the spring steel wire obtained by the process is made of 60Si2MnA carbon alloy steel, the difference from Example 2 is that step S4 is different.

[0128] Step S4 specifically involves: using atomized water to cool the initial product once, reducing the temperature to 630°C, then using cold air for secondary cooling, reducing the temperature to 300°C, and then reducing the temperature to 25°C to obtain spring steel wire with a diameter of 14mm.

[0129] The cooling rate for primary cooling is 15℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0130] Comparative Example 6

[0131] A production process for a non-grinding medium carbon alloy spring steel wire, wherein the spring steel wire obtained by the process is made of 55SiCrA carbon alloy steel, the difference between this process and Example 5 is that steps S1 and S4 are different.

[0132] Step S1 specifically involves: continuously casting molten steel at an overheating temperature of 25°C to obtain a square billet with a square cross-section and a side length of 160 mm.

[0133] Step S4 is as follows: Cooling: The initial product is cooled once with atomized water and the temperature is reduced to 630°C. It is kept at this temperature for 2 hours. Then, it is cooled a second time with cold air and the temperature is reduced to 300°C. After that, the temperature is reduced to 25°C to obtain spring steel wire with a diameter of 15mm.

[0134] The cooling rate for primary cooling is 10℃ / s; the cooling rate for secondary cooling is 2℃ / s.

[0135] Performance testing

[0136] (1) Spring steel wires obtained in Example 2 and Comparative Example 1 were taken respectively, and the decarburized layer of the spring steel wires was detected using an optical microscope. The decarburized metallographic image of the spring steel wire in Example 2 is shown below. Figure 2 The decarburized metallographic image of spring steel wire in Comparative Example 1 is shown below. Figure 3 .

[0137] Combination Figure 2 , Figure 3 The spring steel wire obtained in Comparative Example 1 has obvious decarburization layer defects, while the spring steel wire obtained in Example 2 has almost no decarburization layer defects.

[0138] (2) Spring steel wires obtained in Examples 1-6 and Comparative Examples 1-6 were taken as samples, and the following performance tests were performed on the samples. The test results are shown in Table 3.

[0139] In accordance with GB / T224-2019 "Determination of Decarburization Depth of Steel", the decarburization depth of the sample was tested, and the requirement for the decarburization depth of spring steel wire was: the percentage of the decarburization depth to the diameter of the spring steel wire was ≤0.8%.

[0140] The crack depth of the sample was directly measured using an optical microscope, and the crack depth requirement for spring steel wire was: crack depth ≤ 0.02 mm.

[0141] Table 3 Detection Results

[0142]

[0143] As can be seen from Table 3, the spring steel wire obtained by the production process of this application has a low decarburization layer depth, which is 0.03-0.04 mm and the percentage of the decarburization layer depth to the diameter of the spring steel wire is 0.20-0.27%, indicating a low level of decarburization layer defects. Furthermore, it also has a low crack depth, which is 0.010-0.015 mm, indicating a low level of crack defects and meeting the requirements for both decarburization layer defects and crack defects in spring steel wire.

[0144] Comparing Example 1 with Comparative Examples 1-3, it can be seen that, without grinding or flame peeling of the steel billet, using square steel billets and improving the functional parameters of the production process, although the decarburization layer defect requirement can be met, the crack defect requirement still cannot be met. However, using large-section round steel billets, combined with the interaction of improved production processes, can simultaneously meet both the decarburization layer defect requirement and the crack defect requirement.

[0145] Comparing Example 1 with Comparative Examples 4-5, it can be seen that in step S4, increasing the primary cooling rate and performing heat preservation treatment is beneficial to reducing defects in spring steel wire. Furthermore, when the primary cooling rate is 14-16℃ / s and the heat preservation treatment is 1.5-2.5h, the spring steel wire can exhibit better performance.

[0146] It should be noted that the embodiments described above are only for explaining this application and do not constitute any limitation on this application. This application has been described with reference to typical embodiments, but it should be understood that the terms used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to this application within the scope of the claims, and revisions can be made to the invention without departing from the scope and spirit of this application. Although the application described herein relates to specific methods, materials, and embodiments, it does not mean that this application is limited to the specific examples disclosed herein; on the contrary, this application can be extended to all other methods and applications with the same function.

Claims

1. A production process for grinding-free medium carbon alloy spring steel wire, characterized in that: Includes the following steps: S1. Continuous casting: molten steel is continuously cast to obtain round steel billets with a diameter ≥250mm. S2. Heating: Under the conditions of weak oxidizing gas heating, gas excess coefficient of 1.05-1.10, and positive pressure of 5-40 Pa, the round steel billet is heated to 1010-1070℃ and held for 100-135 min to obtain a hot round steel billet; wherein the oxygen percentage content in the weak oxidizing gas is 1-2 wt%. In step S2, when the round steel billet is transferred into the heating furnace, the temperature is 550-590℃; S3. Rolling: The heated round billet is rolled at an initial rolling temperature of 950-1000℃, a finishing rolling temperature of 880-935℃, and a wire drawing temperature of 860-900℃ to obtain the initial finished product. S4. Cooling: The initial product is cooled once to 615-640℃ and held for 1.5-2.5 hours. Then it is cooled a second time to 250-300℃ and then cooled to room temperature to obtain spring steel wire with a diameter ≤20mm. In step S4, the cooling rate of the first cooling is 14-16℃ / s, and the cooling rate of the second cooling is 1-3℃ / s. The spring steel wire is one of 60Si2MnA carbon alloy steel or 55SiCrA carbon alloy steel.

2. The production process of a grinding-free medium carbon alloy spring steel wire according to claim 1, characterized in that: The diameter of the round steel billet is 250-300mm, and the diameter of the spring steel wire is 6.5-20mm.

3. The production process of a grinding-free medium carbon alloy spring steel wire according to claim 1, characterized in that: The molten steel is mainly composed of the following chemical components by weight percentage: C: 0.54-0.60%, Si: 1.62-1.75%, Mn: 0.69-0.76%, Cr: 0.126-0.129%, Al≤0.015%, Ti≤0.004%, V≤0.005%, Ni≤0.02%, Cu≤0.25%, Mo≤0.02%, P≤0.01%, S≤0.01%, O≤0.0012%, H≤0.0002%, with the balance being Fe.

4. The production process of a grinding-free medium carbon alloy spring steel wire according to claim 1, characterized in that: The molten steel is mainly composed of the following chemical components by weight percentage: C: 0.54-0.56%, Si: 1.41-1.45%, Mn: 0.65-0.69%, Cr: 0.65-0.69%, Al≤0.015%, Ti≤0.004%, V≤0.005%, Ni≤0.02%, Cu≤0.25%, Mo≤0.02%, P≤0.01%, S≤0.01%, O≤0.0012%, H≤0.0002%, with the balance being Fe.

5. The production process of a grinding-free medium carbon alloy spring steel wire according to claim 1, characterized in that: The weakly oxidizing gas is blast furnace gas.

6. The production process of a grinding-free medium carbon alloy spring steel wire according to claim 5, characterized in that: The blast furnace gas contains 1-2 wt% oxygen, ≤10 wt% carbon dioxide, and ≤10 g / Nm³ of water. 3 .

7. A spring steel wire, characterized in that: The spring steel wire is manufactured using the grinding-free medium carbon alloy spring steel wire production process described in any one of claims 1-6.

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