Wind power anchor steel and production method for increasing tempered troostite content of wind power anchor steel

Abstract

The present invention provides a steel for wind power anchor bolts and a production method for increasing the tempered troostite content of the steel for wind power anchor bolts, the components of which are: carbon 0.40-0.43%, silicon 0.23-0.28%, manganese 0.72-0.77%, chromium 1.06-1.11%, molybdenum 0.17-0.20%, aluminum 0.010-0.030%, phosphorus ≤0.015%, sulfur ≤0.010%, and the remainder is iron and unavoidable impurities. Compared with the prior art, the present invention improves the quality of steel for anchor bolts by optimizing continuous casting parameters. First, the hardenability of the steel is guaranteed to meet the requirements of the central organization under the premise of optimal composition through component design; second, the component segregation of the steel is reduced by optimizing the continuous casting electric stirring parameters, and the negative segregation of the product is reduced. The steel of Φ45 mm and below produced by the present invention meets the requirement of ≥92% tempered troostite content at the edge and center of the anchor bolt.

Description

Technical Field

[0001] The invention belongs to the technical field of steel for wind power anchor bolts, and specifically relates to steel for wind power anchor bolts and a production method for increasing the tempered troostite content of the steel for wind power anchor bolts. Background Art

[0002] Wind power anchor bolts are specially used to fix wind turbines. They are usually made of high-strength steel to maintain the stability of wind turbines. The anchor bolts are required to have tensile strength ≥1040MPa, yield strength ≥940MPa, elongation ≥9%, cross-sectional shrinkage ≥48%, and -40℃ impact energy ≥27J. At the same time, in order to ensure the fatigue performance of the anchor bolts, the tempered troostite content of the cross section is required to be ≥90%.

[0003] At present, the mechanical properties of wind power anchor bolts meet the requirements, but the hardenability at the center is insufficient, resulting in the tempered bainite content at the center not meeting the requirement of ≥90%.

[0004] The patent with publication number CN 112359274 A published on February 12, 2021, discloses a high-strength round steel for wind power anchor bolts and its manufacturing method. The disclosed technical solution is: composition: C: 0.36-0.46%, Mn: 0.70-1.10%, Si: ≤0.25%, Mo: 0.15-0.35%, Cr: 0.90-1.45%, Ni: ≤0.30%, Al: 0.015-0.030%, P: ≤0.015%, S: ≤0.015%, and the rest is Fe and unavoidable impurities. It improves the steel purity and mechanical properties of round steel for wind power anchor bolts after heat treatment through smelting continuous casting, pile cooling, heating, descaling rolling, ultrasonic and magnetic leakage testing through optimization of chemical composition ratio and reasonable design of manufacturing process. However, there is no disclosure on how to increase the content of center tempered troostite. Summary of the invention

[0005] The purpose of the present invention is to provide a steel for wind power anchor bolts and a production method for increasing the tempered troostite content of the steel for wind power anchor bolts, and to ensure that the hardenability of the steel material can meet the requirements of the central organization through component design and continuous casting method optimization.

[0006] The specific technical solutions of the present invention are as follows:

[0007] A steel for wind power anchor bolts, comprising the following components in percentage by mass:

[0008] Carbon 0.40-0.43%, silicon 0.23-0.28%, manganese 0.72-0.77%, chromium 1.06-1.11%, molybdenum 0.17-0.20%, aluminum 0.010-0.030%, phosphorus ≤0.015%, sulfur ≤0.010%, and the balance is iron and unavoidable impurities.

[0009] After heat treatment, the steel for wind power anchor bolts has an area content of tempered bainite on the surface of the product of ≥92%, preferably 92-97% on the surface, with the remainder being ferrite and bainite; the tempered bainite content in the center of the product is ≥92%, preferably 92-97% on the center, with the remainder being ferrite and bainite.

[0010] The diameter of the wind power anchor steel is Φ≤45mm.

[0011] After heat treatment, the tensile strength of the produced wind power anchor steel is ≥1130MPa, the yield strength is ≥1040MPa, the elongation is ≥15%, the cross-sectional shrinkage is ≥58%, and the impact energy at -40℃ is ≥80J.

[0012] The present invention provides a production method for increasing the tempered troostite content of steel for wind power anchor bolts, comprising the following process flow:

[0013] Converter - LF refining - continuous casting - heating - rolling - heat treatment;

[0014] The converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

[0015] In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

[0016] The continuous casting is to continuously cast a square billet of 180 mm×180 mm;

[0017] Furthermore, in the continuous casting, the electromagnetic stirring of the crystallizer is controlled: the current is 290-310A, the frequency is 4HZ; the electromagnetic pulse stirring (PMO) voltage is 240-270V, the frequency is 17HZ; the terminal electromagnetic stirring current is 140-160A, the frequency is 10HZ.

[0018] The continuous casting is controlled at a constant casting speed of 1.7 m / min.

[0019] The heating furnace controls the soaking zone temperature to 1100-1160°C;

[0020] The rolling starts at a temperature of 1050±15°C.

[0021] The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

[0022] Compared with the prior art, the present invention improves the quality of anchor bolt steel by optimizing continuous casting parameters. First, the hardenability of the steel is guaranteed to meet the requirements of the central organization under the premise of optimal composition through composition design; second, the composition segregation of the steel is reduced by optimizing the continuous casting electric stirring parameters, and the negative segregation of the product is reduced. The steel of Φ45mm and below produced by the present invention meets the requirement that the tempered troostite content at the edge and center of the anchor bolt is ≥92%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the edge organization diagram of the product in Example 1;

[0024] Figure 2 This is the organizational chart of the product center in Example 1;

[0025] Figure 3 This is the edge organization diagram of the product in Example 2;

[0026] Figure 4 This is the organizational chart of the product center in Example 2;

[0027] Figure 5 This is the edge organization diagram of the product in Example 3;

[0028] Figure 6 This is the organizational chart of the product center in Example 3;

[0029] Figure 7 This is the edge organization diagram of the product of comparative example 1;

[0030] Figure 8 This is the product center organization chart of Comparative Example 1;

[0031] Fig. 9 This is the edge organization diagram of the product of comparative example 2;

[0032] Fig.10 This is the product center organization chart of Comparative Example 2. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. 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.

[0034] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0035] Example 1-Example 3

[0036] A steel for wind power anchor bolts includes the following mass percentage components: as shown in Table 1, the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0037] Comparative Example 1-Comparative Example 2

[0038] A steel for wind power anchor bolts includes the following mass percentage components: as shown in Table 1, the remainder not shown in Table 1 is Fe and unavoidable impurities.

[0039] Table 1 Composition content (wt%) of steel for wind power anchor bolts in various embodiments and comparative examples

[0040]

[0041] The production method of wind power anchor steel described in Example 1 includes the following process flow:

[0042] Converter - LF refining - continuous casting - heating - rolling - heat treatment;

[0043] Wherein, the converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

[0044] In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

[0045] The continuous casting is to continuously cast a square billet of 180 mm×180 mm;

[0046] Furthermore, in the continuous casting, the electromagnetic stirring of the crystallizer is controlled: the current is 300A, the frequency is 4HZ; the electromagnetic pulse stirring (PMO) voltage is 240V, the frequency is 17HZ; the terminal electromagnetic stirring current is 150A, the frequency is 10HZ; and the continuous casting constant pulling speed is controlled to be 1.7m / min.

[0047] In the heating, the temperature of the soaking section of the heating furnace is controlled to be 1130°C;

[0048] The rolling starts at a temperature of 1054°C.

[0049] The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

[0050] The production method of wind power anchor steel described in Example 2 includes the following process flow: converter - LF refining - continuous casting - heating - rolling - heat treatment;

[0051] Wherein, the converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

[0052] In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

[0053] The continuous casting is to continuously cast a square billet of 180 mm×180 mm;

[0054] Furthermore, in the continuous casting, the electromagnetic stirring of the crystallizer is controlled: the current is 300A, the frequency is 4HZ; the electromagnetic pulse stirring (PMO) voltage is 240V, the frequency is 17HZ; the terminal electromagnetic stirring current is 150A, the frequency is 10HZ; and the continuous casting constant pulling speed is controlled to be 1.7m / min.

[0055] The heating furnace controls the soaking zone temperature to 1120°C;

[0056] The rolling starts at a temperature of 1050°C.

[0057] The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

[0058] The production method of wind power anchor steel described in Example 3 includes the following process flow: converter - LF refining - continuous casting - heating - rolling - heat treatment;

[0059] Wherein, the converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

[0060] In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

[0061] The continuous casting is to continuously cast a square billet of 180 mm×180 mm;

[0062] Furthermore, in the continuous casting, the electromagnetic stirring of the crystallizer is controlled: the current is 300A, the frequency is 4HZ; the electromagnetic pulse stirring (PMO) voltage is 240V, the frequency is 17HZ; the terminal electromagnetic stirring current is 150A, the frequency is 10HZ; and the continuous casting constant pulling speed is controlled to be 1.7m / min.

[0063] In the heating, the temperature of the soaking section of the heating furnace is controlled to be 1145°C;

[0064] The rolling starts at a temperature of 1058°C.

[0065] The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

[0066] The production method of wind power anchor steel described in Comparative Example 1 includes the following process flow: converter - LF refining - continuous casting - heating - rolling - heat treatment;

[0067] Wherein, the converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

[0068] In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

[0069] The continuous casting is to continuously cast a square billet of 180 mm×180 mm;

[0070] Furthermore, in the continuous casting, the electromagnetic stirring of the crystallizer is controlled: the current is 300A, the frequency is 4HZ; the electromagnetic pulse stirring (PMO) voltage is 240V, the frequency is 17HZ; the terminal electromagnetic stirring current is 150A, the frequency is 10HZ; and the continuous casting constant pulling speed is controlled to be 1.7m / min.

[0071] In the heating, the temperature of the soaking section of the heating furnace is controlled to be 1140°C;

[0072] The rolling starts at a temperature of 1058°C.

[0073] The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

[0074] The production method of wind power anchor steel described in Comparative Example 2 includes the following process flow: converter - LF refining - continuous casting - heating - rolling - heat treatment;

[0075] Wherein, the converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

[0076] In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

[0077] The continuous casting is to continuously cast a square billet of 180 mm×180 mm;

[0078] Furthermore, in the continuous casting, the electromagnetic stirring of the crystallizer is controlled: the current is 300A and the frequency is 4HZ; the terminal electromagnetic stirring current is 150A and the frequency is 10HZ; and the continuous casting constant pulling speed is controlled to be 1.7m / min. The pulsed electromagnetic stirring (PMO) process is not used.

[0079] In the heating, the temperature of the soaking section of the heating furnace is controlled to be 1130°C;

[0080] The rolling starts at a temperature of 1055°C.

[0081] The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

[0082] The surface (edge) and center structures of the products produced in each embodiment and comparative example are as follows: Figure 1-Figure 10 shown.

[0083] The tempered troostite content of the product produced in Example 1 is 97% at the edge; the tempered troostite content at the center is 92%;

[0084] The tempered troostite content of the product produced in Example 2 is 96% at the edge; the tempered troostite content at the center is 93%;

[0085] The tempered troostite content at the edge of the product produced in Example 3 is 96%; the tempered troostite content at the center is 94%;

[0086] In the production of Comparative Example 1, the Cr and Mo components were low, resulting in insufficient hardenability of the product, causing the edge tempered troostite content to meet the requirement of 93%, but the center tempered troostite content was only 76%;

[0087] In the production of Comparative Example 2, the magnetic pulse stirring was turned off, resulting in negative segregation of the center components of the product, causing the center tempered troostite content to be only 78%, and the edge tempered troostite content to be 90%, which met the requirements.

[0088] The performance of each embodiment and comparative example was tested in accordance with standard number GB / 228.1 "Metallic material tensile test Part 1: Room temperature test method" and GB / T229 "Metallic material Charpy pendulum impact test method", and the results are shown in Table 2.

[0089] Table 2 Performance of various embodiments and comparative examples.

[0090]

[0091] The underlined data above do not meet the requirements of the present invention.

[0092] The description of the above embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A steel for wind power anchor bolt, characterized in that: The wind power anchor steel includes the following components in percentage by mass: Carbon 0.40-0.43%, silicon 0.23-0.28%, manganese 0.72-0.77%, chromium 1.06-1.11%, molybdenum 0.17-0.20%, aluminum 0.010-0.030%, phosphorus ≤0.015%, sulfur ≤0.010%, and the balance is iron and unavoidable impurities.

2. The steel for wind power anchor bolt according to claim 1, characterized in that: After the wind power anchor steel is heat treated, the tempered bainite area content of the product surface is ≥92%, and the tempered bainite area content of the product center is ≥92%.

3. A production method for increasing the tempered troostite content of the wind power anchor steel according to claim 1 or 2, characterized in that: The production method comprises the following process flow: Converter—LF refining—continuous casting—heating—rolling—heat treatment.

4. The production method according to claim 3, characterized in that: The converter adopts high-draw supplementary blowing to control the converter end point composition C≥0.08% and P≤0.008%.

5. The production method according to claim 3, characterized in that: In the LF refining, lime, refining slag and slag-reducing agent are added to ensure that the refining slag has good fluidity and basicity R≥3.0, and the white slag retention time is ≥20 minutes.

6. The production method according to claim 3, characterized in that: The continuous casting controls the electromagnetic stirring of the crystallizer: the current is 290-310A, the frequency is 4HZ; the electromagnetic pulse stirring (PMO) voltage is 240-270V, the frequency is 17HZ; the terminal electromagnetic stirring current is 140-160A, the frequency is 10HZ.

7. The production method according to claim 3, characterized in that: The continuous casting is controlled at a constant casting speed of 1.7 m / min.

8. The production method according to claim 3, characterized in that: For the heating, the temperature of the soaking section of the heating furnace is controlled at 1100-1160°C.

9. The production method according to claim 3, characterized in that: The rolling starts at a temperature of 1050±15°C.

10. The production method according to claim 3, characterized in that: The heat treatment is specifically as follows: quenching at 880°C, keeping warm for 90 minutes, and then water cooling; and then tempering at 615°C, keeping warm for 120 minutes, and then water cooling.

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