Carbon composition control method for L415 pipeline steel

Abstract

The present invention relates to a method for controlling the carbon content of L415 pipeline steel, belonging to the field of steelmaking. The method adopts a process route of combined blowing converter → LF refining → RH refining → continuous casting. The present invention provides a method for controlling the carbon content of L415 pipeline steel, which adopts a process route of converter steelmaking, LF refining, RH refining, and continuous casting to obtain molten steel with qualified composition and temperature, thereby resolving the dependence of L415 pipeline steel on low-carbon ferrochrome, ensuring smooth production scheduling of L415 pipeline steel, and reducing production costs. The present invention provides a method for controlling the carbon content of L415 pipeline steel. Through system planning, the carbon content at the converter endpoint is controlled at 0.03-0.04%, low-carbon ferromanganese, ferrosilicon, and ferromolybdenum are used for steel tapping, high-carbon ferrochrome, ferroniobium, and ferrotitanium are used in the LF refining process, and submerged arc operation is performed throughout the process, thereby achieving the purpose of controlling the carbon content of L415 pipeline steel to ≤0.08%.

Description

Technical Field

[0001] The invention belongs to the field of steelmaking and relates to a method for controlling the carbon composition of L415 pipeline steel. Background Art

[0002] In terms of composition design, L415 pipeline steel adopts a low-carbon approach, typically using low-carbon alloys such as manganese-silicon alloy, metallic manganese, and low-carbon ferrochrome. Generally, manganese-silicon alloy is used with silicon and manganese, and low-carbon ferrochrome is used with chromium. Low-carbon ferrochrome is expensive and not a commonly available alloy. Furthermore, the lack of production planning for L415 pipeline steel makes procurement of low-carbon ferrochrome difficult and leads to long procurement cycles, which impacts the delivery cycle of L415. Using high-carbon ferrochrome to control the carbon content of L415 pipeline steel within an acceptable range is a difficult point in controlling L415 pipeline steel and a key focus of L415 pipeline steel production. Therefore, a method for controlling the carbon content of L415 pipeline steel is urgently needed. Summary of the Invention

[0003] In view of this, the object of the present invention is to provide a method for controlling the carbon composition of L415 pipeline steel to solve the dependence of L415 pipeline steel on low-carbon ferrochrome.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A method for controlling the carbon content of L415 pipeline steel adopts a process route of combined blowing converter → LF refining → RH refining → continuous casting.

[0006] Optionally, in the combined converter blowing step, molten iron and scrap steel are loaded into a converter for converter oxygen blowing smelting to obtain converter smelting molten steel.

[0007] Optionally, in the combined blowing converter step, the total charge amount is 235t, the iron-steel ratio is controlled at 850-930kg / furnace, the converter end oxygen is 600-800ppm, the steel tapping temperature is 1610℃-1650℃, and the end carbon is 0.03-0.04%.

[0008] Optionally, in the combined blowing converter step, alumina, low carbon ferromanganese, ferrosilicon and ferromolybdenum are added during the steel tapping process.

[0009] Optionally, during the LF refining step, composition fine-tuning and chromium alloying operations are performed, sampling is performed after the first heating of the LF process, and composition fine-tuning and chromium alloying are performed based on the sampling results.

[0010] Optionally, during the LF refining step, 1000-1200 kg / furnace of metallurgical lime, 150-250 kg / furnace of molten refining slag, and 150-250 kg / furnace of aluminum slag balls are added during the process, and submerged arc operation is performed throughout the process to control carbon increase during the LF heating process.

[0011] Optionally, in the LF refining step, the carbon content is controlled to be ≤0.05% after the first heating is completed.

[0012] Optionally, in the LF refining step, high carbon ferrochrome is added after the heating is completed, the chromium content is controlled to be ≤0.15%, and the carbon is increased by 0.016-0.018%.

[0013] Optionally, in the LF refining step, after the high carbon ferrochrome is added, the carbon content of the molten steel is controlled at 0.06-0.07%.

[0014] Optionally, after the LF refining step, the molten steel is sent to the RH refining and degassing treatment without adjusting the composition. After the RH refining is completed, continuous casting is carried out to cast into steel billets, and then sent to the medium and heavy plate production line to be rolled into L415 pipeline steel plates.

[0015] The beneficial effects of the present invention are:

[0016] 1. The present invention provides a method for controlling the carbon composition of L415 pipeline steel. The method adopts a process route of converter steelmaking, LF refining, RH refining, and continuous casting to obtain molten steel with qualified composition and temperature. This solves the dependence of L415 pipeline steel on low-carbon ferrochrome, ensures smooth production scheduling of L415 pipeline steel, and reduces production costs.

[0017] 2. The present invention provides a method for controlling the carbon content of L415 pipeline steel. Through system planning, the carbon content of the converter end point is controlled at 0.03-0.04%. Low-carbon ferromanganese, ferrosilicon, and ferromolybdenum are used for tapping, and high-carbon ferrochromium, ferroniobium, and ferrotitanium are used in the LF refining process. Submerged arc operation is carried out throughout the process, achieving the purpose of controlling the carbon content of L415 pipeline steel to ≤0.08%.

[0018] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0020] L415 pipeline steel adopts the production process of molten iron desulfurization → top and bottom combined blowing converter → LF refining → RH vacuum refining → continuous casting → medium and thick plate. The composition requirements of L415 pipeline steel are carbon: 0.05% to 0.10%; silicon: 0.10% to 0.35%; manganese: 1.40% to 1.67%; phosphorus ≤ 0.014%, sulfur ≤ 0.007%; acid-soluble aluminum: 0.015% to 0.050%; chromium: 0.10% to 0.30%; titanium: 0.010% to 0.020%; niobium: 0.035% to 0.060%; molybdenum: ≤ 0.30%; Pcm < 0.21%. The present invention uses high-carbon ferrochrome, low-carbon ferromanganese, and ferrosilicon to adjust the carbon, manganese, and silicon contents of L415 pipeline steel. The carbon content of the L415 pipeline steel can be controlled to be ≤0.08%, the manganese content to be controlled to be 1.50±0.05%, and the silicon content to be ≤0.20%, thereby meeting a target control requirement of a carbon content of ≤0.08%. This avoids the situation in which the production of L415 pipeline steel is forced to be postponed due to a long low-carbon ferrochrome procurement cycle. This provides another alloy adjustment solution, solves the problem of temporary scheduling difficulties in the L415 production plan, and ensures the smooth implementation of the L415 pipeline steel production plan. The method has high practical promotion value.

[0021] The main points of the present invention include:

[0022] ① According to the carbon composition requirements of L415 pipeline steel, the converter end point carbon is controlled at 0.03-0.04%, and the end point oxygen is controlled within ≤800ppm.

[0023] ② According to the composition requirements of L415 pipeline steel, the chromium content is controlled within the standard limit, about 0.15%, and 3.10kg / ton of high-carbon ferrochrome is used. The high-carbon ferrochrome content is 6.45%, the carbon content is increased by 0.018%, and the chromium content is increased by 0.16%.

[0024] ③The final manganese content of L415 pipeline steel is 0.05%. Low carbon ferromanganese and ferrosilicon are used to match manganese and silicon during the steel tapping process. 19.89 kg / t of low carbon ferromanganese and 3.279 kg / t of ferrosilicon are added.

[0025] ④ During the steel-making process, 750±50kg / furnace of LF metallurgical lime is added. During the LF refining process, 1000±100kg / furnace of LF metallurgical lime, 200-300kg / furnace of electric molten refining slag, and 200-300kg / furnace of aluminum slag balls are added. White slag refining is carried out throughout the entire process, and the carbon increase in the LF refining process is controlled to be ≤0.02%. Under this mode, the carbon content of L415 pipeline steel is ≤0.08%, which can meet the carbon content control requirements.

[0026] The present invention provides a method for controlling the carbon content of L415 pipeline steel. The method adopts a process route of 210t combined blowing converter → LF refining → RH refining → continuous casting, and adopts the following smelting process, specifically:

[0027] 1. Load molten iron and scrap steel into a converter for oxygen-blowing smelting to obtain converter-smelted molten steel. The total charge is 235 tons, with an iron-to-steel ratio of 850-930 kg / furnace. The converter's endpoint oxygen concentration is 600-800 ppm, the tapping temperature is 1610°C-1650°C, and the endpoint carbon concentration is 0.03-0.04%.

[0028] 2. Taiwan aluminum, low carbon ferromanganese, ferrosilicon and ferromolybdenum are added during the steel-making process.

[0029] 3. The molten steel is subjected to LF refining, where it undergoes compositional fine-tuning and chromium alloying. Sampling is performed after the first LF heating step, and compositional fine-tuning and chromium alloying are performed based on the sampling results. During the LF refining process, 1000-1200 kg of metallurgical lime, 150-250 kg of molten refining slag, and 150-250 kg of aluminum slag balls are added per furnace. Submerged arc operation is employed throughout the entire process, and carbon increase is controlled during the LF heating process. After the first LF heating step, the carbon content is controlled to ≤0.05%. After the heating step, high-carbon ferrochrome is added, with the chromium content controlled to ≤0.15%, and carbon increase is achieved by 0.016-0.018%. After the addition of high-carbon ferrochrome, the carbon content of the molten steel is controlled to 0.06-0.07%.

[0030] 4. The molten steel from LF station is sent to RH refining and degassing treatment without adjusting the composition. After RH refining, it is continuously cast into steel billets and then sent to the medium and heavy plate production line to be rolled into L415 pipeline steel plates.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for controlling the carbon content of L415 pipeline steel, characterized by: This method adopts the process route of combined blowing converter → LF refining → RH refining → continuous casting; In the combined-blowing converter step, molten iron and scrap steel are loaded into the converter for converter oxygen blowing smelting to obtain converter smelting molten steel; In the combined-blowing converter step, the total charge is 235t, the iron-steel ratio is controlled at 850-930kg / furnace, the converter end oxygen is ≤800ppm, the tapping temperature is 1610℃-1650℃, and the end carbon is 0.03-0.04%; In the combined blowing converter step, alumina, low carbon ferromanganese, ferrosilicon and ferromolybdenum are added during the tapping process; During the LF refining step, fine-tuning of composition and chromium alloying are carried out. Sampling is performed after the first heating in the LF process, and fine-tuning of composition and chromium alloying are carried out based on the sampling results. During the LF refining step, 1000-1200 kg of metallurgical lime, 150-250 kg of molten refining slag, and 150-250 kg of aluminum slag balls are added to the furnace. The entire process is submerged arc operation to control the carbon increase during the LF heating process. In the LF refining step, the carbon content is controlled to ≤0.05% after the first heating; In the LF refining step, high carbon ferrochrome is added after the heating is completed, the chromium content is controlled to be ≤0.15%, and the carbon is increased by 0.016~0.018%.

2. The method for controlling the carbon content of L415 pipeline steel according to claim 1, characterized in that: In the LF refining step, after high carbon ferrochrome is added, the carbon content of the molten steel is controlled at 0.06-0.07%.

3. The method for controlling the carbon content of L415 pipeline steel according to claim 1, characterized in that: After the LF refining step, the molten steel is sent to the RH refining and degassing treatment without adjusting the composition. After the RH refining is completed, continuous casting is carried out to cast into steel billets, and then sent to the medium and heavy plate production line to be rolled into L415 pipeline steel plates.