阅读说明：本技术 一种风电法兰用钢s355nl商品坯的生产方法 (Production method of steel S355NL commodity blank for wind power flange ) 是由 刘志国 李鑫 丁晓志 让丽军 李立英 于 2021-07-02 设计创作，主要内容包括：本发明公开了一种风电法兰用钢S355NL商品坯的生产方法,包括：保证铸机恒过热度和恒拉速；钢水过热度需保证在15～28℃之间；拉速稳定在0.7-0.9m/min；结晶器宽侧水量4500L/min,窄侧水量370L/min,结晶器水温36±2℃；二冷水比水量0.57L/公斤钢,二冷水温维持在25±3℃；电磁搅拌参数：电流380A,频率5Hz；轻压下设置在6、7、8三个段,每段压2mm；切割后的铸坯立即放入缓冷区缓冷。本发简单、易于操作,不需要铸坯经过热处理就可消除铸坯残存内部应力,解决了S355NL商品坯在电锯切割时断裂的问题。(The invention discloses a production method of a steel S355NL commodity blank for a wind power flange, which comprises the following steps: ensuring the constant superheat degree and the constant drawing speed of the casting machine; the superheat degree of the molten steel is required to be ensured to be between 15 and 28 ℃; the pulling speed is stabilized at 0.7-0.9 m/min; the water quantity of the wide side of the crystallizer is 4500L/min, the water quantity of the narrow side of the crystallizer is 370L/min, and the water temperature of the crystallizer is 36 +/-2 ℃; the specific water amount of the secondary cooling water is 0.57L/kg of steel, and the temperature of the secondary cooling water is maintained at 25 +/-3 ℃; electromagnetic stirring parameters: current 380A, frequency 5 Hz; the soft pressing is arranged at three sections of 6, 7 and 8, and each section presses 2 mm; and immediately placing the cut casting blank into a slow cooling area for slow cooling. The method is simple and easy to operate, residual internal stress of the casting blank can be eliminated without heat treatment of the casting blank, and the problem that the commercial blank of S355NL is broken when being cut by an electric saw is solved.)

1. A production method of a commercial billet of steel S355NL for wind power flanges is characterized by comprising the following steps:

(1) optimizing casting parameters of a casting machine process and improving center segregation of a casting blank, wherein the casting machine process comprises the following steps: the technological parameters of superheat degree, pulling speed, electromagnetic stirring, soft pressing position and pressing amount, crystallizer water amount and secondary cooling water amount are optimized:

ensuring the constant superheat degree and the constant drawing speed of the casting machine; the superheat degree of the molten steel is required to be ensured to be between 15 and 28 ℃; the pulling speed is stabilized at 0.7-0.9 m/min;

the water quantity of the wide side of the crystallizer is 4500L/min, the water quantity of the narrow side of the crystallizer is 370L/min, and the water temperature of the crystallizer is 36 +/-2 ℃;

the specific water amount of the secondary cooling water is 0.57L/kg of steel, and the temperature of the secondary cooling water is maintained at 25 +/-3 ℃;

electromagnetic stirring parameters: current 380A, frequency 5 Hz;

the soft pressing is arranged at three sections of 6, 7 and 8, and each section presses 2 mm;

(2) immediately placing the cut casting blank into a slow cooling area for slow cooling:

the off-line plate blanks are intensively placed in a slow cooling area, the periphery of a place with good heat insulation performance of the blank warehouse is surrounded by refractory brick walls, the height of each wall is 4 m, and the hot blanks are intensively placed to slow down the cooling of the casting blanks and eliminate internal stress; and (4) placing the blanks in each stack to the highest position, placing the blanks in a concentrated manner, and slowly cooling for more than 72 hours.

2. The production method of the steel for wind power flanges S355NL commodity blank according to claim 1, wherein the nozzle is ensured to be free from blockage in the sector section.

3. The production method of the steel S355NL for the wind power flange as claimed in claim 1, wherein the pressure at 6-12 stages is as follows, the fluctuation is not more than 10 bar:

4. the production method of the commercial billet of the steel S355NL for the wind power flange as claimed in claim 1, wherein the steel S355NL for the wind power flange comprises the following components by mass percent:

0.15-0.17% of C, 0.2-0.3% of Si, 1.35-1.45% of Mn, 0-0.008% of P, 0-0.003% of S, 0.022-0.037% of Alt, 0.022-0.035% of Als, 0.032-0.042% of Nb, 0.045-0.055% of V, 0.001-0.0025% of Ca and 0-0.005% of N, wherein the Fe and inevitable impurities are contained in the alloy.

Technical Field

The invention relates to the technical field of continuous casting in the metallurgical industry, in particular to a production method of a steel S355NL commodity blank for a wind power flange.

Background

In recent years, the wind power generation installed capacity in the world is in a rapid growth trend, and as long as 2021 and 2 months, the installed capacity of wind power generation in China is 2.8 hundred million kilowatts, which is increased by 34.3 percent on a par. With the rapid growth of wind power generation, the market demand for wind power towers is increasing, and the importance of key connecting pieces of the wind power towers, namely wind power tower flanges, is also gaining more and more attention. The wind power tower flange is a key connecting piece, a supporting piece and a stress piece of the wind power tower and is an important part of wind power generation equipment. S355NL casting blank is used as steel for wind power flanges, and is required to have good internal and external quality and good comprehensive mechanical property, and the center segregation is detected to reach C class by low power.

The flange forging by using the casting blank is that a mother blank is cut into standard blocks, then the standard blocks are forged to manufacture a blank ring, and the blank ring is rolled, thermally treated and finely processed to obtain a wind power flange ring forging, the forged blank is thermally treated, and the forging is processed into a wind power flange workpiece according with the size by using a ring rolling machine.

The method adopted by a flange manufacturer when cutting a casting blank is flame cutting or electric saw cutting, if the produced casting blank has a crack source on the surface or inside due to improper technical measures or residual stress in the casting blank is not released, the casting blank can be broken in the cutting process, and if a 5000-ton S355NL commodity blank of a certain wind power flange manufacturer is supplied by a steel-clad wide plate casting machine in 2018, the casting blank is broken in the cutting process, so that the steel clad is compensated for a large amount.

Many manufacturers release the residual internal stress of the casting blank by a method of heat treatment of the commercial blank, which does not cause the problem of casting blank fracture during cutting, but requires heat treatment, thus the manufacturing cost of the casting blank is obviously increased.

The production methods of the steel S355NL for the wind power tower barrel flange are researched, but the low-temperature impact property, the welding property and the like of the steel plate are ensured through a heat treatment process after the steel plate is rolled from a casting blank, and the internal and external quality of the casting blank is ensured to be rarely mentioned when the steel plate is cast into a commercial blank from S355 NL.

The Chinese patent with the application number of 201910004206.4 discloses a normalizing S355NL-Z35 super-thick steel plate and a 120mm low-alloy super-thick plate developed by a manufacturing method through continuous casting billet rolling and a normalizing heat treatment process, and the product has good low-temperature impact property, internal quality and welding property. However, how to reduce the center segregation is not described in how to ensure the surface quality of the S355NL ingot.

The Chinese patent with the application number of 201910220422.2 discloses a low-carbon-equivalent S355NL normalized thick plate for wind power and a production method thereof, and discloses a low-carbon-equivalent steel plate which has low-temperature impact property of-50 ℃ after being normalized and simultaneously has yield strength and tensile strength meeting standard requirements. Also, how to reduce the center segregation is not described as to how to secure the surface quality of the S355NL ingot.

The Chinese patent with the application number of 201610460071.9 discloses a 250mm thick S355NL low-carbon high-toughness low-alloy steel plate and a manufacturing method thereof, wherein the steel plate is produced by adopting a continuous casting billet with the thickness of 450mm, and the steel plate has excellent low-temperature impact property and good comprehensive mechanical property after being normalized after being rolled into the steel plate. The invention also does not describe how to guarantee the surface quality of the S355NL casting blank and how to reduce the center segregation.

The invention is different from the invention in that the invention adopts the optimized casting machine process parameters to achieve the purpose of ensuring the internal and external quality of the casting blank, the casting blank is directly sold to a wind power manufacturer as a commodity blank, and then the wind power manufacturer cuts and forges the casting blank into a flange.

Disclosure of Invention

The invention aims to provide a production method of a steel S355NL commodity blank for a wind power flange, which reduces the occurrence rate of product defects and improves the qualification rate of product quality and market share; the method is simple and easy to operate, residual internal stress of the casting blank can be eliminated without heat treatment of the casting blank, and the problem that the commercial blank of S355NL is broken when cut by an electric saw is solved.

In order to solve the technical problems, the invention adopts the following technical scheme:

the invention relates to a production method of a steel S355NL commodity blank for a wind power flange, which comprises the following steps:

(1) optimizing casting parameters of a casting machine process and improving center segregation of a casting blank, wherein the casting machine process comprises the following steps: the technological parameters of superheat degree, pulling speed, electromagnetic stirring, soft pressing position and pressing amount, crystallizer water amount and secondary cooling water amount are optimized:

ensuring the constant superheat degree and the constant drawing speed of the casting machine; the superheat degree of the molten steel is required to be ensured to be between 15 and 28 ℃; the pulling speed is stabilized at 0.7-0.9m/min, preferably 0.8 m/min;

the water quantity of the wide side of the crystallizer is 4500L/min, the water quantity of the narrow side of the crystallizer is 370L/min, and the water temperature of the crystallizer is 36 +/-2 ℃;

the specific water amount of the secondary cooling water is 0.57L/kg of steel, and the temperature of the secondary cooling water is maintained at 25 +/-3 ℃;

electromagnetic stirring parameters: current 380A, frequency 5 Hz.

The soft pressing is arranged at three sections of 6, 7 and 8, and each section presses 2 mm;

(2) immediately placing the cut casting blank into a slow cooling area for slow cooling:

the off-line plate blanks are intensively placed in a slow cooling area, the periphery of a place with good heat insulation performance of the blank warehouse is surrounded by refractory brick walls, the height of each wall is 4 m, and the hot blanks are intensively placed to slow down the cooling of the casting blanks and eliminate internal stress; and (4) placing the blanks in each stack to the highest position, placing the blanks in a concentrated manner, and slowly cooling for more than 72 hours.

Furthermore, the fan-shaped section is ensured to have no nozzle blockage.

Further, the pressure of 6-12 sections is as the following table, the fluctuation is not more than 10 bar:

further, the wind power flange steel S355NL comprises the following components in percentage by mass:

0.15-0.17% of C, 0.2-0.3% of Si, 1.35-1.45% of Mn, 0-0.008% of P, 0-0.003% of S, 0.022-0.037% of Alt, 0.022-0.035% of Als, 0.032-0.042% of Nb, 0.045-0.055% of V, 0.001-0.0025% of Ca and 0-0.005% of N, wherein the Fe and inevitable impurities are contained in the alloy.

Compared with the prior art, the invention has the beneficial technical effects that:

the invention ensures the internal and external quality of the casting blank, has good surface quality and lighter center segregation, is in C series in low-power detection, can effectively eliminate internal stress, and has no over-cutting fracture phenomenon after being supplied to wind power flange manufacturers. The production method of the S355NL wind power flange steel commodity blank is good in surface quality, light in center segregation, free of heat treatment and suitable for large-scale popularization and use, and internal residual stress is fully eliminated.

Drawings

The invention is further illustrated in the following description with reference to the drawings.

FIG. 1 is a photomicrograph of example 1;

FIG. 2 is a photomicrograph of example 2;

FIG. 3 is a photomicrograph of example 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments.

Example 1:

the 2200 x 300 section is adopted, the spray bar of the sector section is carefully checked whether the spray bar is blocked before casting, and if the spray bar is blocked, the spray bar is immediately replaced. The casting method comprises the following chemical components:

0.16 percent of C, 0.20 percent of Si, 1.36 percent of Mn, 0.007 percent of P, 0.003 percent of S, 0.028 percent of Alt, 0.026 percent of Als, 0.038 percent of Nb, 0.048 percent of V, 0.0019 percent of Ca and 0.0028 percent of N; the water flow of the wide side of the crystallizer is 4500L/min, the water flow of the narrow side of the crystallizer is 370L/min, and the water temperature of the crystallizer is 34 ℃; the temperature of secondary cooling water is maintained at 22 ℃; the drawing speed is kept at 0.8m/min, and the specific water amount is 0.57L/kg of steel; the superheat degree of the molten steel is 15 ℃; electromagnetic stirring current 380A, frequency 5 Hz; the soft pressing is arranged at three sections of 6, 7 and 8, and each section presses 2 mm; the pressure at 6-12 sections is as follows:

directly inserting the slabs to a slow cooling area after cutting, and intensively stacking, wherein 12 slabs are placed in each stack, namely 3.6 meters, and the slow cooling time is 72 hours. And (3) checking the surface quality of the plate blank to be free of cracks, obtaining a macroscopic result C2.0, feeding back the macroscopic result to a wind power factory as shown in figure 1, and using the macroscopic result normally, wherein the fracture phenomenon does not occur during cutting.

Example 2:

the 2200 x 300 section is adopted, the spray bar of the sector section is carefully checked whether the spray bar is blocked before casting, and if the spray bar is blocked, the spray bar is immediately replaced. The casting method comprises the following chemical components: 0.15 percent of C, 0.28 percent of Si, 1.42 percent of Mn, 0.005 percent of P, 0.002 percent of S, 0.023 percent of Alt, 0.021 percent of Als, 0.033 percent of Nb, 0.052 percent of V, 0.0021 percent of Ca and 0.0032 percent of N; the water flow of the wide side of the crystallizer is 4500L/min, the water flow of the narrow side of the crystallizer is 370L/min, and the water temperature of the crystallizer is 38 ℃; the temperature of secondary cooling water is maintained at 28 ℃; the drawing speed is kept at 0.8m/min, and the specific water amount is 0.57L/kg of steel; the superheat degree of the molten steel is 27 ℃; electromagnetic stirring current 380A, frequency 5 Hz; the soft pressing is arranged at three sections of 6, 7 and 8, and each section presses 2 mm; the pressure at 6-12 sections is as follows:

directly inserting the slabs to a slow cooling area after cutting, and intensively stacking, wherein 12 slabs are placed in each stack, namely 3.6 meters, and the slow cooling time is 72 hours. And (3) checking the surface quality of the plate blank to be free of cracks, obtaining a macroscopic result C3.0, and feeding back and using the macroscopic picture as shown in figure 2 after the macroscopic picture is supplied to a wind power factory to be normal, wherein the fracture phenomenon does not occur during cutting.

Example 3:

the 2200 x 300 section is adopted, the spray bar of the sector section is carefully checked whether the spray bar is blocked before casting, and if the spray bar is blocked, the spray bar is immediately replaced. The casting method comprises the following chemical components: 0.17 percent of C, 0.24 percent of Si, 1.40 percent of Mn, 0.006 percent of P, 0.002 percent of S, 0.035 percent of Alt, 0.033 percent of Als, 0.041 percent of Nb, 0.048 percent of V, 0.0015 percent of Ca and 0.0026 percent of N; the water flow of the wide side of the crystallizer is 4500L/min, the water flow of the narrow side of the crystallizer is 370L/min, and the water temperature of the crystallizer is 36 ℃; keeping the temperature of secondary cooling water at 25 ℃; the drawing speed is kept at 0.8m/min, and the specific water amount is 0.57L/kg of steel; the superheat degree of the molten steel is 21 ℃; electromagnetic stirring current 380A, frequency 5 Hz; the soft pressing is arranged at three sections of 6, 7 and 8, and each section presses 2 mm; the pressure at 6-12 sections is as follows:

directly inserting the slabs to a slow cooling area after cutting, and intensively stacking, wherein 12 slabs are placed in each stack, namely 3.6 meters, and the slow cooling time is 72 hours. And (3) checking the surface quality of the plate blank to be free of cracks, obtaining a macroscopic result C3.0, and feeding back the macroscopic result to a wind power factory to be normal in use after the macroscopic result is shown in a picture 3, wherein the fracture phenomenon does not occur during cutting.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.