阅读说明：本技术 一种使用大方坯生产60n钢轨的方法 (Method for producing 60N steel rail by using bloom ) 是由 边影 赵桂英 薛虎东 郑瑞 董捷 王慧军 苏航 王嘉伟 于 2021-07-22 设计创作，主要内容包括：本发明公开了一种使用大方坯生产60N钢轨的方法,对真空处理及连铸的主要工艺参数进行了优化,其他工艺过程控制仍沿用原有的控制策略,工艺路线:铁水预处理(KR)→顶底复吹转炉→LF+VD精炼→大方坯铸机(320mm×415mm,M－EMS,动态轻压下)→轨梁厂轧制。轧制后对试制的3炉320mm×415mm铸坯及成品轨进行检验,钢坯硫印检验结果均为0、1级,工艺控制稳定。铸坯低倍最大为1级,没有裂纹、皮下气泡等缺陷,铸坯低倍良好。(The invention discloses a method for producing a 60N steel rail by using a bloom, which optimizes main process parameters of vacuum treatment and continuous casting, and adopts the original control strategy for controlling other process processes, wherein the process route comprises molten iron pretreatment (KR) → top-bottom combined blowing converter → LF + VD refining → bloom caster (320mm × 415mm, M-EMS, dynamic soft reduction) → rolling in a rail beam plant. And (3) testing the trial-produced casting blank and finished product rail with the thickness of 320mm multiplied by 415mm in a 3 furnace after rolling, wherein the test results of the sulfur prints of the steel blank are all 0 grade and 1 grade, and the process control is stable. The maximum low power of the casting blank is 1 grade, the defects of cracks, subcutaneous bubbles and the like are avoided, and the casting blank is good at low power.)

1. A method of producing a 60N rail from a bloom, comprising:

1) pretreating molten iron: the fluctuation range of the P content in the molten iron components is 0.146-0.148%, and the S content is 0.051%;

2) smelting in a converter: the converter end point adopts medium carbon steel, the carbon content of converter tapping is in the range of 0.08-0.11%, and the P content of the converter tapping is in the range of 0.009-0.013%;

3) refining in an LF furnace: according to production requirements, LF adopts refining slag with medium alkalinity and strong reducibility to process molten steel, relevant process parameters are determined according to the components and temperature of molten steel in position for processing, the requirements of white slag operation are met according to the requirements, and the components and temperature of molten steel out of position meet VD processing requirements;

4) VD vacuum degassing: the VD vacuum treatment soft blowing time is more than 15min, the average time is 19min, the sedation time after soft blowing is 21-35min, and the average time is 28 min;

5) continuous casting: the superheat degree of the continuous casting molten steel is between 16 ℃ and 25 ℃, the fluctuation range is small, and the constant drawing speed is adopted; the chemical composition and the gas content of the finished product both meet the requirements of TB/T2344-;

6) rolling: heating a steel billet by using a walking beam type heating furnace, formulating a heating process, ensuring a higher initial rolling temperature as much as possible, and simultaneously preventing the billet from being scrapped due to overburning caused by overhigh temperature; the initial rolling temperature in the rolling process is controlled to be 1100-1130 ℃.

2. The method of claim 1 wherein the billet is heated to a temperature as shown in the following table:

Technical Field

The invention relates to a method for producing a 60N steel rail by using a bloom.

Background

The U75V 60N hectometer hot rolled steel rail produced by steel cladding always adopts a casting blank of 280mm multiplied by 380mm, in order to search and improve the quality and the production capacity of the steel rail, a 320mm multiplied by 415mm section large square billet is used for producing the 60N steel rail, the compression ratio of the steel rail is increased (from 13.7 to 17.1), and the compactness of the steel rail is improved. In addition, a casting blank with a section of 320mm multiplied by 415mm is adopted, so that not only is the blank shape for producing the steel rail added, but also the pressure of a casting machine can be relieved, and the production capacity of the steel rail is improved.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a method for producing a 60N steel rail by using a bloom, which reduces the pressure of a casting machine and improves the production capacity of the steel rail.

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

the invention relates to a method for producing a 60N steel rail by using a bloom, which comprises the following steps:

1) pretreating molten iron: the fluctuation range of the P content in the molten iron components is 0.146-0.148%, and the S content is 0.051%;

2) smelting in a converter: the converter end point adopts medium carbon steel, the carbon content of converter tapping is in the range of 0.08-0.11%, and the P content of the converter tapping is in the range of 0.009-0.013%;

3) refining in an LF furnace: according to production requirements, LF adopts refining slag with medium alkalinity and strong reducibility to process molten steel, relevant process parameters are determined according to the components and temperature of molten steel in position for processing, the requirements of white slag operation are met according to the requirements, and the components and temperature of molten steel out of position meet VD processing requirements;

4) VD vacuum degassing: the VD vacuum treatment soft blowing time is more than 15min, the average time is 19min, the sedation time after soft blowing is 21-35min, and the average time is 28 min;

5) continuous casting: the superheat degree of the continuous casting molten steel is between 16 ℃ and 25 ℃, the fluctuation range is small, and the constant drawing speed is adopted; the chemical composition and the gas content of the finished product both meet the requirements of TB/T2344-;

6) rolling: heating a steel billet by using a walking beam type heating furnace, formulating a heating process, ensuring a higher initial rolling temperature as much as possible, and simultaneously preventing the billet from being scrapped due to overburning caused by overhigh temperature; the initial rolling temperature in the rolling process is controlled to be 1100-1130 ℃.

Further, the billet was heated to the temperature shown in the following table:

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

the hundred-meter 60N heavy rail is produced by adopting a casting machine with a section of 320mm multiplied by 415mm, the steel grade adopts U75V, and the continuous casting slab is changed from 280mm multiplied by 380mm to 320mm multiplied by 415 mm. Compared with the existing heavy rail blank production process in a steel plant, the equipment difference between the vacuum treatment process and the continuous casting process is larger. Aiming at the change, the main technological parameters of vacuum treatment and continuous casting are optimized, and the original control strategy is still used for controlling other technological processes. The process route is molten iron pretreatment (KR) → top-bottom combined blown converter → LF + VD refining → bloom caster (320mm × 415mm, M-EMS, dynamic soft reduction) → rolling in a rail beam factory. And (3) testing the trial-produced casting blank and finished product rail with the thickness of 320mm multiplied by 415mm in a 3 furnace after rolling, wherein the test results of the sulfur prints of the steel blank are all 0 grade and 1 grade, and the process control is stable. The maximum low power of the casting blank is 1 grade, the defects of cracks, subcutaneous bubbles and the like are avoided, and the casting blank is good at low power. And then carrying out detailed detection on indexes such as non-metallic inclusions, conventional tensile property, tread hardness, grain size, macrostructure, steel rail impact energy and the like of the rail head, the rail web and the rail bottom of the 3-furnace finished steel rail according to the TB/T2344-2012 standard requirements, wherein detection results show that various conventional properties and special properties of the 320mm multiplied by 415mm section casting blank rolled steel rail meet the TB/T2344-2012 standard requirements. Compared with the 60N steel rail produced by casting blanks with the thickness of 280mm multiplied by 380mm, the grain size of the steel rail is improved, the low-power obviously improved trend is achieved, the center porosity of the rail web is reduced, the tread hardness of the steel rail is improved, and the transverse impact power of the rail web is improved.

Drawings

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

FIG. 1 is a distribution diagram of normal temperature rail web impact power;

FIG. 2 is a distribution diagram of the rail web impact power at-20 ℃.

Detailed Description

A method of producing a 60N rail using a bloom, comprising:

1) pretreating molten iron: the fluctuation range of the P content in the molten iron is 0.146-0.148%, the S content is 0.051%, and the fluctuation range of the P, S content in the molten iron is smaller, so that the smelting requirement can be met. The specific components and temperatures are shown in Table 1.

TABLE 1 composition and temperature of charged molten iron

Smelting number	Si/％	Mn/％	P/％	S/％	Temperature/. degree.C
						16304661	0.57	0.52	0.148	0.051	1315
16103430	0.57	0.52	0.148	0.051	1315
						16103431	0.59	0.53	0.146	0.051	1317

2) Smelting in a converter: the converter end point adopts medium carbon steel, the carbon content of converter tapping is in the range of 0.08-0.11%, and the P content of the converter tapping is in the range of 0.009-0.013%, so as to meet the requirements.

3) Refining in an LF furnace: according to production requirements, LF adopts refining slag with medium alkalinity and strong reducibility to process molten steel, relevant process parameters are determined according to the components and temperature of molten steel in position for processing, the requirements of white slag operation are met according to the requirements, and the components and temperature of molten steel out of position meet VD processing requirements.

4) VD vacuum degassing: the VD vacuum treatment soft blowing time is more than 15min, the average time is 19min, the sedation time after soft blowing is 21-35min (the requirement is more than 10min), and the average time is 28 min.

5) Continuous casting: the superheat degree of the continuous casting molten steel is 16-25 ℃, the fluctuation range is small, and the constant drawing speed is adopted. The chemical composition and the gas content of the finished product both meet the requirements of TB/T2344-. The specific components are shown in Table 2

TABLE 2 composition and gas content of the continuously cast product

6) Casting blank sulfur mark and low power: after the U75V rail steel is smelted and continuously cast, a continuous casting billet is taken from each furnace for sulfur print inspection, the sulfur print inspection results of the billet are all 0 and 1 grade according to the rating of the casting billet acceptance standard, and the process control is stable. The maximum low power of the casting blank is 1 grade, no defects such as cracks and subcutaneous bubbles exist, the casting blank is good in low power, and specific inspection results are shown in tables 3 and 4.

TABLE 3 Low power test results for continuous casting slabs

TABLE 4 Low power test results for continuous casting slabs

7) Rolling: a walking beam type heating furnace is used for heating steel billets in a rail beam factory, a heating process is formulated to ensure a high initial rolling temperature as much as possible, and simultaneously, the situation that the blanks are scrapped due to overburning caused by overhigh temperature is prevented. The initial rolling temperature in the rolling process is controlled to be 1100-1130 ℃. The specific heating schedule is shown in Table 5

TABLE 5 Steel billet heating System deg.C

After rolling, performing detailed detection on indexes such as non-metallic inclusions, conventional tensile property, tread hardness, grain size, steel rail impact power and the like on a finished steel rail head, a rail web and a rail bottom of a tested 3-furnace finished steel rail according to the TB/T2344-2012 standard requirements, wherein detection results show that the conventional properties and the special properties of the steel rail rolled by the casting blank with the section of 320mm multiplied by 415mm meet the TB/T2344-2012 standard requirements, and the detection results are superior to the quality of the steel rail produced by the casting blank with the section of 280mm multiplied by 380 mm. The specific test results are shown in tables 6 to 8.

TABLE 6 test results of tensile Properties of rails

TABLE 7 Tread hardness test results HBW of rails

TABLE 8 grade of non-metallic inclusions in rails

Transverse and longitudinal impact samples are taken from the rail web of the steel rail produced by casting blanks with the thickness of 320mm multiplied by 415mm and casting blanks with the thickness of 280mm multiplied by 380mm respectively, and the impact energy is tested at normal temperature and the temperature of minus 20 ℃. The 1# represents the rail produced from a slab of 320 mm. times.415 mm billet, the 2# represents the rail produced from a slab of 280 mm. times.380 mm billet, the results are shown in Table 9,

TABLE 9 impact energy of rail J

As can be seen from fig. 1 and 2, at normal temperature and-20 ℃, the longitudinal impact energy 1# and 2# of the rail web are equivalent, and no obvious difference exists, but the transverse impact energy 1# of the rail web is superior to 2# and the result is obvious.

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.