Steel plate smelting method capable of accurately controlling carbon

Abstract

The invention relates to the technical field of metallurgy, and provides a steel plate smelting method capable of accurately controlling carbon, which comprises the steps of molten iron mixing, converter blowing and continuous casting, detecting the carbon content C1 after converter blowing, tapping, adding a first carburant before tapping, adding a second carburant during tapping, detecting the carbon content C2 after tapping, and driving into a carbon line; the mass sum of the first carburant and the second carburant is C3; the mass ratio of the first carburant to the second carburant is 1: 5, and when C1 is larger than or equal to 0.10 wt%, the first carburant does not need to be added; and the addition amount of the carburant is C3 = (0.21%-C1) * 100 * 0.18 kg / t * the tapping amount. According to the technical scheme, the problems that the carbon content of the steel plate is unstable and the carbon control difficulty is large in the prior art are solved.

Description

Technical Field

[0001] The present invention relates to the field of metallurgical technology, and in particular to a steel plate smelting method with precise carbon control. Background Art

[0002] Rebar has been widely used in engineering construction because of its low price and good comprehensive mechanical properties. With the acceleration of the pace of modernization infrastructure construction, market demand has also increased year by year.

[0003] Carbon is the main strengthening element in rebar and the main element affecting the comprehensive mechanical properties of rebar. As the carbon content increases, the strength and hardness of rebar increase, while the impact toughness decreases. In order to ensure the product quality and service performance of rebar, the carbon content is usually controlled in a narrow range in actual production. The traditional rebar production process includes converter, bottom blowing after the furnace, and continuous casting. It is technically difficult to achieve precise carbon control on the production line without LF refining equipment. The main difficulty of the existing technology is that the carbon increase effect after oxygen decarburization in the converter is unstable, and the subsequent process affects the carbon content, causing composition fluctuations. The process control is difficult, which ultimately affects the product quality.

[0004] Patent CN115058556A discloses a method for precisely controlling the carbon and manganese components of rebar. This method uses small packages of high-carbon ferromanganese and carbon wire to adjust the manganese and carbon in molten steel during the CAS refining process. The narrow component hit rate of rebar can reach more than 99%, but it has low applicability to existing production lines and requires a large amount of cost to transform the production line, and the smelting process cost is relatively high.

[0005] Patent CN112094987A discloses a method for controlling the carbon content of molten steel. Based on the existing control of the converter endpoint, this method appropriately increases the converter endpoint carbon content, adjusts the alloy addition timing when tapping, and allows C and O in the molten steel to further react, thereby achieving the effect of low carbon drawing and effectively reducing the oxygen content in the molten steel. However, the converter low carbon drawing endpoint control method will increase the oxidizability of the molten steel, and the subsequent further reaction of C and O will increase the pressure of post-furnace carbon increase, thereby increasing the investment cost of the carbon increaser.

[0006] Therefore, the present invention provides a rebar smelting and preparation method with precise control of carbon content, which can stably control the carbon content, reduce carbon content fluctuations, and reduce the scrapping of finished products due to unqualified carbon content. Summary of the invention

[0007] The present invention provides a steel plate smelting method with precise carbon control, which solves the problems of unstable carbon content of steel plates and difficulty in carbon control in related technologies.

[0008] The technical solution of the present invention is as follows: The present invention provides a steel plate smelting method with precise carbon control, the smelting method comprising molten iron mixing, converter blowing, and continuous casting; the carbon content C is detected after converter blowing. 1 , tapping, adding a first carburizer before tapping, adding a second carburizer during tapping, and detecting the carbon content C after tapping 2 , driving in carbon wire; The total mass of the first recarburizer and the second recarburizer added is C 3 ; The mass ratio of the first carburizer to the second carburizer is 1:5. 1 When ≥0.10wt%, it is not necessary to add the first recarburizer; The amount of the recarburizer added is C 3 = (0.21% - C 1 )×100×0.18kg / t×steel output.

[0009] As a further technical solution, the recarburizer is carbon powder, and the fixed carbon content in the carbon powder is ≥96%.

[0010] As a further technical solution, the consumption of the carbon wire is (0.25%-C 2 )×100×0.8m / t×steel output.

[0011] As a further technical solution, the steel plate is composed of the following components in weight percentage: C 0.22%~0.25%, Si 0.35%~0.65%, Mn 1.30%~1.55%, P≤0.040%, S≤0.040%, V 0.015%~0.030%, and the rest is Fe and other inevitable impurities.

[0012] As a further technical solution, the converter blowing includes slag splashing, adding scrap steel and molten iron, and oxygen blowing smelting.

[0013] As a further technical solution, the slag splashing method is top blowing nitrogen; the slag splashing time is 2-4 minutes; the amount of scrap steel added is 18%-22% of the mass of the steel plate; the oxygen flow rate in the oxygen blowing smelting is 18000m 3 / h, oxygen pressure is 0.9MPa, and oxygen blowing time is 9~11min.

[0014] In the present invention, top-blown nitrogen is used to splash slag to protect the furnace lining.

[0015] As a further technical solution, the C 1 It is 0.06wt%~0.12wt%; the final temperature of the converter blowing is 1630~1650℃.

[0016] As a further technical solution, auxiliary materials and slag-forming agents are also added to the converter blowing; the amount of the auxiliary materials added is 26-33 kg / t; the amount of the slag-forming agent added is 9-11 kg / t; the auxiliary material is lime; and the slag-forming agent is magnesite.

[0017] As a further technical solution, the mass content of CaO in the lime is ≥85%, and the activity of the lime is ≥360mL.

[0018] As a further technical solution, the mass content of MgO in the magnesite is ≥42%.

[0019] As a further technical solution, a deoxidizer is added before tapping the steel; the amount of the deoxidizer added is 0.8-1.2 kg / t.

[0020] As a further technical solution, alloys are further added during the steel production, and the alloys include ferrosilicon alloy, manganese silicon alloy, and vanadium nitrogen alloy.

[0021] In the present invention, the alloy is added during steel tapping to control the composition of the molten steel after the furnace, and the carbon content in the molten steel after the furnace is controlled to be ≥0.21%. A deoxidizer is added to the molten steel before the alloy is added to adjust the oxidizability of the molten steel, thereby avoiding oxidation reactions of easily oxidizable elements in the alloy and reducing the alloy yield.

[0022] As a further technical solution, the alloy is added during the 1 / 3 to 2 / 3 process of steel tapping.

[0023] As a further technical solution, the addition amount of the ferrosilicon alloy is 0.9-1.3 kg / t; the addition amount of the manganese silicon alloy is 20-25 kg / t; and the addition amount of the vanadium nitrogen alloy is 0.4-0.7 kg / t.

[0024] As a further technical solution, at least one of the following features is also included: The molten iron content S in the molten iron mixing is ≤0.060%, and the temperature of the molten iron after mixing is ≤1350°C; Bottom blowing of nitrogen is also performed during the steel tapping process, and the blowing time of nitrogen is 3 to 5 minutes; The continuous casting adopts large ladle and medium ladle to add covers; The continuous casting speed is 2.6-3.2 m / min.

[0025] The working principle and beneficial effects of the present invention are: In the present invention, the carbon control mode adopts a method of using a carburizer as the main agent and a carbon wire as the auxiliary agent. Through the process route of converter blowing and continuous casting, the carburizer is added before and during steelmaking to improve the sufficiency of the carbon-oxygen reaction and the uniformity of the carbon element in the ladle, thereby achieving precise control of the carbon composition of steel types that do not require refining. This not only meets the application of existing production lines, but also improves the precise control of the carbon composition and solves the problem of unstable carbon control after the furnace.

[0026] In the present invention, by adding a carburizer before and during steel tapping, the cost increase problem caused by increasing the consumption of other strengthening alloys such as manganese is solved, and the cost is saved. The disadvantage of unstable carbon yield in the carburizer is compensated by fine-tuning the carbon line. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0028] Example 1 S1. The molten iron is mixed in the mixing furnace, and the molten iron outlet composition [S] = 0.035%, and the molten iron outlet temperature is 1323℃; S2. Before adding steel materials, nitrogen is blown to splash slag and protect the furnace. The splashing time is 3 minutes. Then scrap steel is added. The scrap steel addition ratio is 21.2%. After adding molten iron, oxygen blowing is carried out for smelting. The oxygen flow rate is 18000m 3 / h, oxygen pressure is 0.9MPa, oxygen blowing time is 9min35s, converter end point carbon content is 0.07wt%, blowing end point temperature is 1644℃; S3. During the converter blowing process, 1610kg lime (CaO=90%, activity=379mL) was added to make slag, and then 650kg slagging agent (MgO=45%) was added; after the converter blowing was completed, steel was tapped (steel output was 60t), 55kg deoxidizer was added before tapping, 55kg ferrosilicon alloy, 1300kg manganese silicon alloy, 26kg vanadium nitrogen alloy were added during 1 / 3 of the tapping process, 25.2kg carbon powder was added before tapping, and 126kg carbon powder was added during tapping. After tapping, the post-furnace composition test was quickly carried out, and the test result was [C]=0.208wt%; S4. According to the post-furnace test results, carbon wire is injected into the ladle through the wire feeder. The carbon wire consumption is 201.6m3. During the entire steel-out process, the ladle is continuously stirred with bottom blowing nitrogen. The nitrogen blowing time is 5 minutes. S5. In the continuous casting step, large and medium ladles were covered to protect the casting throughout the whole process. The continuous casting speed was 3.0 m / min. The carbon content of the medium ladles was detected to be 0.248 wt%, and the carbon recovery rate of the recarburizer was 94%.

[0029] Example 2 S1. The molten iron is mixed in the mixing furnace, and the composition of the molten iron out of the station [S] is 0.027%, and the temperature of the molten iron out of the station is 1311℃; S2. Before adding steel materials, nitrogen is blown to splash slag for 3 minutes. Then scrap steel is added at a ratio of 19.5%. After adding molten iron, oxygen is blown for smelting at an oxygen flow rate of 18000m 3 / h, oxygen pressure is 0.9MPa, oxygen blowing time is 9min50s, converter end point carbon content is 0.06wt%, blowing end point temperature is 1648℃; S3. During the converter blowing process, 1720kg lime (CaO=92%, activity=398mL) was added to make slag, and then 580kg slagging agent (MgO=47%) was added; after the converter blowing was completed, steel was tapped (steel output was 60t), 60kg deoxidizer was added before tapping, 60kg ferrosilicon alloy, 1330kg manganese silicon alloy, 28kg vanadium nitrogen alloy were added during 2 / 3 of the tapping process, 27kg carbon powder was added before tapping, and 135kg carbon powder was added during tapping. After tapping, the post-furnace composition test was quickly carried out, and the test result was [C]=0.202wt%; S4. According to the post-furnace test results, carbon wire is injected into the ladle through the wire feeder, and the carbon wire consumption is 230.4m. During the entire steel-out process, the ladle is continuously stirred with bottom blowing nitrogen, and the nitrogen blowing time is 5min. S5. In the continuous casting step, the large ladle and the medium ladle are covered to protect the pouring throughout the whole process. The continuous casting speed is 3.1m / min. The carbon content of the medium ladle is detected to be 0.25wt%, and the carbon recovery rate of the recarburizer is 93%.

[0030] Comparative Example 1 The only difference between this comparative example and Example 1 is that no carbon wire is driven in after steel tapping; Results: The carbon content detected after the furnace was 0.209wt%, the carbon content detected in the middle package during continuous casting was 0.205wt%, and the carbon recovery rate of the recarburizer was 94.7%.

[0031] Comparative Example 2 The only difference between this comparative example and Example 1 is that 151 kg of carbon powder is added during steel tapping, and no carbon powder is added before steel tapping; Results: The carbon content detected after the furnace was 0.199wt%, the carbon content detected in the middle package during continuous casting was 0.24wt%, and the carbon recovery rate of the recarburizer was 87.9%.

[0032] Comparative Example 3 The only difference between this comparative example and Example 1 is that 151 kg of carbon powder is added during steel tapping, no carbon powder is added before steel tapping, and no carbon wire is driven in after steel tapping; Results: The carbon content detected after the furnace was 0.20wt%, the carbon content detected in the middle package during continuous casting was 0.197wt%, and the carbon recovery rate of the recarburizer was 88.6%.

[0033] Compared with Comparative Examples 1 to 3, in Examples 1 to 2, a carburizer is added before and during steel tapping, and a carbon wire is driven into the steel after tapping. The carbon content of the middle package is measured to be within 0.22wt% to 0.25wt%, and the carbon recovery rate of the carburizer is above 93%. This indicates that the carburizer is added before and during steel tapping, and the carbon wire is driven into the steel after tapping, which improves the precise control of the carbon component and the carbon recovery rate in the carburizer, and solves the problem of unstable carbon control after the furnace.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A steel plate smelting method with precise carbon control, characterized in that: It includes molten iron mixing, converter blowing, and continuous casting; after converter blowing, the carbon content C1 is detected, steel is tapped, a first carburizer is added before steel tapping, a second carburizer is added during steel tapping, and after steel tapping, the carbon content C2 is detected and a carbon wire is punched; The added mass of the first recarburizer and the second recarburizer is C3; The mass ratio of the first recarburizer to the second recarburizer is 1:5, and when C1≥0.10wt%, the first recarburizer does not need to be added; The added amount of the recarburizer is C3=(0.21%-C1)×100×0.18kg / t×steel output.

2. A steel plate smelting method with precise carbon control according to claim 1, characterized in that: The consumption of the carbon wire is (0.25%-C2)×100×0.8m / t×steel output.

3. The method for smelting a steel plate with precise carbon control according to claim 1, characterized in that: The steel plate is composed of the following components by weight percentage: C 0.22%-0.25%, Si 0.35%-0.65%, Mn 1.30%-1.55%, P≤0.040%, S≤0.040%, V 0.015%-0.030%, and the rest is Fe and other inevitable impurities.

4. The method for smelting steel plates with precise carbon control according to claim 1, characterized in that: The converter blowing includes slag splashing, adding scrap steel and molten iron, and oxygen blowing smelting.

5. The method for smelting steel plates with precise carbon control according to claim 4, characterized in that: The slag splashing method is top-blowing nitrogen; the slag splashing time is 2-4 minutes; the amount of scrap steel added is 18%-22% of the mass of the steel plate; the oxygen flow rate in the oxygen blowing smelting is 18000m 3 / h, oxygen pressure is 0.9MPa, and oxygen blowing time is 9~11min.

6. The method for smelting steel plates with precise carbon control according to claim 4, characterized in that: The C1 is 0.06wt%~0.12wt%; the converter blowing end temperature is 1630~1650℃.

7. The method for smelting steel plates with precise carbon control according to claim 4, characterized in that: Auxiliary materials and slagging agents are also added during the converter blowing; the amount of the auxiliary materials added is 26-33 kg / t; the amount of the slagging agent added is 9-11 kg / t; the auxiliary material is lime; and the slagging agent is magnesite.

8. The method for smelting steel plates with precise carbon control according to claim 1, characterized in that: A deoxidizer is also added before tapping; the amount of the deoxidizer added is 0.8-1.2 kg / t.

9. The method for smelting steel plates with precise carbon control according to claim 1, characterized in that: Alloys are also added during the steel production, including ferrosilicon alloy, manganese silicon alloy, and vanadium nitrogen alloy; the addition amount of the ferrosilicon alloy is 0.9-1.3 kg / t; the addition amount of the manganese silicon alloy is 20-25 kg / t; and the addition amount of the vanadium nitrogen alloy is 0.4-0.7 kg / t.

10. The method for smelting steel plates with precise carbon control according to claim 1, characterized in that: Also includes at least one of the following features: The molten iron content S in the molten iron mixing is ≤0.060%, and the temperature of the molten iron after mixing is ≤1350°C; Bottom blowing of nitrogen is also performed during the steel tapping process, and the blowing time of nitrogen is 3 to 5 minutes; The continuous casting adopts large ladle and medium ladle to add covers; The continuous casting speed is 2.6-3.2 m / min.