Search

CN-117737567-B - Sulfur-control smelting method for ER50-6S welding wire steel

CN117737567BCN 117737567 BCN117737567 BCN 117737567BCN-117737567-B

Abstract

The invention discloses a sulfur-controlled smelting method for welding wire steel ER50-6S, wherein the mass content of the welding wire steel ER is 0.008-0.015%, the smelting process flow comprises KR desulfurization, converter smelting, LF refining and continuous casting, converter tapping, when the content of S in molten steel is 0.010-0.015%, after 25%, alloy is added according to the sequence of ferrosilicon and high silicon-manganese, before the tapping is finished, alloy is completely added, when the content of S in molten steel is less than or equal to 0.010%, sulfur-containing slag, ferrosilicon and high silicon-manganese are sequentially added, sulfur-containing slag and alloy are completely added, then calcium silicate is added to synthesize slag before the tapping is finished, ladle bottom blowing stirring is carried out in the whole tapping process, the obtained slag basicity CaO/SiO 2 =0.4-0.7, T.Fe+MnO content is 3-5%, then the ladle is conveyed to LF refining treatment, after the LF refining station enters, caO/SiO 2 =0.9-1.2, T.Fe+MnO content is 2.5-4.5%, then the ladle is electrified, and then the ladle is adjusted to be in a bottom blowing stirring mode until the continuous casting is finished, and the bottom blowing stirring is finished. The invention obtains the low-cost sulfur increasing effect, and the stability of the sulfur content in the molten steel is further enhanced.

Inventors

  • ZHAO TIANHUA
  • YANG XIAOCHENG
  • DING ZHENTAO
  • CAI SHOUGUI
  • LI PENG
  • GENG ZHENJIE
  • CHENG TIANLE
  • Zhang Sishuang

Assignees

  • 常熟市龙腾特种钢有限公司

Dates

Publication Date
20260512
Application Date
20231228

Claims (7)

  1. 1. A sulfur-controlled smelting method for welding wire steel ER50-6S is characterized by comprising, by mass, 0.06-0.09% of C, 0.8-1.0% of Si, 1.4-1.7% of Mn, less than or equal to 0.02% of P, 0.008-0.015% of S, less than or equal to 0.005% of Alt, less than or equal to 0.0008% of T.Ca and other unavoidable components; the smelting process flow comprises KR desulfurization, converter smelting, LF refining and continuous casting, and comprises the following steps of: Step 1, KR desulfurization, wherein after KR desulfurization is carried out on molten iron, 4.1-4.5% of molten iron C and 0.003-0.008% of S are obtained, and the temperature is 1300-1360 ℃; Smelting in a converter, namely adding desulfurized molten iron and high-quality scrap steel into the converter for smelting, wherein the ratio of the scrap steel is 15-20%, the molten steel C at the smelting end point of the converter is 0.03-0.06%, O is 0.040-0.075%, P is less than or equal to 0.018%, S is less than or equal to 0.015%, the temperature is more than 1630 ℃, the alkalinity CaO/SiO2=2.5-3.0 and T.Fe is 13-18%; Tapping in a converter, when the S content in molten steel is 0.010-0.015%, adding alloy according to the sequence of ferrosilicon and high silicon-manganese after the converter taps 25%, adding sulfur-containing slag and alloy according to the sequence of sulfur-containing slag, ferrosilicon and high silicon-manganese before tapping is finished, when the S content in molten steel is less than or equal to 0.010%, adding sulfur-containing slag and alloy before tapping is finished, adding calcium silicate synthetic slag, fully opening ladle bottom blowing and stirring in the whole tapping process, stirring for 3-5min after the synthetic slag is added, obtaining slag basicity CaO/SiO 2 = 0.4-0.7, and the content of T.Fe+MnO is 3-5%, and then carrying out LF refining treatment; Step 4, LF refining, in-station LF refining, sampling and measuring molten steel and slag chemical components, carrying out ladle bottom blowing stirring, after molten steel and slag components are tested out, adding low-titanium low-aluminum ferrosilicon and manganese metal into the molten steel according to target components of steel types to adjust the molten steel components to reach the target components, adding lime and silicon carbide to adjust the slag components to obtain slag basicity CaO/SiO 2 =0.9-1.2 and content of T.Fe+MnO of 2.5-4.5%, then starting electrifying and heating to enable the temperature of the molten steel to reach a target value, then adjusting the ladle bottom blowing to be in a soft stirring mode, and carrying out continuous casting and pouring on the molten steel after soft stirring is finished; and 5, continuous casting protection pouring.
  2. 2. The sulfur-controlled smelting method for welding wire steel ER50-6S according to claim 1, wherein in the step 1, molten iron samples are taken at intervals of 3-5min to analyze the S content in the KR desulfurization process, and when the S content is 0.003-0.008%, desulfurization is stopped, slag removal treatment is performed, and the slag removal rate is more than or equal to 95%.
  3. 3. The sulfur-controlled smelting method of welding wire steel ER50-6S according to claim 1, wherein in the step 2, the content of S in the high-quality scrap steel is 0.005-0.015%, the content of P is less than or equal to 0.02%, and the balance is Fe and other unavoidable components.
  4. 4. The sulfur-controlled smelting method for welding wire steel ER50-6S according to claim 1, wherein in the step 3, the alloy comprises 70-75% of Si, less than or equal to 0.025% of P, less than or equal to 0.015% of S, the balance of Fe and other unavoidable components, 25-30% of high-silicon manganese, 62-67% of Mn, less than or equal to 0.015% of P, less than or equal to 0.01% of S, the balance of Fe and other unavoidable components, 2.5-5.5% of S, 3-10mm of CaO/SiO 2 =0.3-0.5, and other unavoidable components, wherein the grain size is more than or equal to 90%, the maximum of which is not more than 20mm, the calcium silicate synthetic slag comprises 45-55% of CaO, 35-45% of SiO 2 , 5-10% of MgO, and the balance of unavoidable components.
  5. 5. The sulfur-controlled smelting method for welding wire steel ER50-6S according to claim 1, wherein in the step 3, 4.5-5.5kg/t of ferrosilicon, 17-19kg/t of high silicon manganese, 2.5-3.5kg/t of sulfur-containing slag, 10-15kg/t of calcium silicate synthetic slag are added in the tapping process, the ladle bottom blowing is 400-500L/min in the tapping process, and the bottom blowing flow is 300-400NL/min at the tapping end.
  6. 6. The method for sulfur-controlled smelting of steel ER50-6S for welding wire according to claim 1, wherein in the step 4, lime is more than or equal to 95% CaO and other unavoidable components, and silicon carbide is more than or equal to 98% SiC and other unavoidable components.
  7. 7. The sulfur-controlled smelting method for welding wire steel ER50-6S according to claim 1, wherein in the step 4, the LF refining inbound temperature is more than or equal to 1560 ℃, the ladle bottom blowing flow in the non-operation stage of the LF refining process is 100-150NL/min, the alloy adding stage, the ladle bottom blowing flow is 200-250NL/min, the lime and silicon carbide adding stage and the slag component adjusting stage, the ladle bottom blowing flow is 150-200NL/min, the electrifying heating stage adopts the ladle bottom blowing flow of 200-250NL/min, the ladle bottom blowing flow in the soft stirring stage is 50-100NL/min, and the soft stirring time is more than or equal to 20min.

Description

Sulfur-control smelting method for ER50-6S welding wire steel The invention relates to a sulfur-control smelting method for welding wire steel ER50-6S, belonging to the technical field of welding wire steel smelting. Background Sulfur is usually controlled as a harmful element in the steel smelting, and sulfur is hardly dissolved in the steel and forms a compound with iron, and in the steel, feS and Fe form a eutectic with a low melting point (a melting point of 985 ℃) which is called hot shortness because of melting and cracking of the eutectic distributed in grain boundaries when the steel is hot worked at around 1200 ℃. In the steel for welding, too high sulfur is extremely liable to cause segregation in the weld joint, and low-melting eutectic is formed, so that cracks or embrittlement are formed in the weld joint. The welding wire steel ER50-6S needs to control the S content in molten steel to be 0.008-0.015%, the sulfur content is low, the fluidity of a molten pool of a finished welding rod in the welding process is poor, the problem of thermal brittleness of a welding position can be caused by overhigh sulfur content, the welding effect and performance are affected, the range of the S content in the steel is small, and the control difficulty is very high. In particular, in the later stage of LF smelting process, desulfurization is serious, and sulfur elements are required to be added in a sulfur line proportion. The smelting process technology designed and developed by the invention solves the key technical problem of the stability of the ER50-6S sulfur content control of the welding wire steel. Disclosure of Invention In order to solve the problems, the invention discloses a sulfur-control smelting method for welding wire steel ER50-6S, which comprises the following specific technical scheme: A sulfur-controlled smelting method for welding wire steel ER50-6S comprises, by mass, 0.06-0.09% of C, 0.8-1.0% of Si, 1.4-1.7% of Mn, less than or equal to 0.02% of P, 0.008-0.015% of S, less than or equal to 0.005% of Alt, less than or equal to 0.0008% of T.Ca and other unavoidable components; the smelting process flow comprises KR desulfurization, converter smelting, LF refining and continuous casting, and comprises the following steps of: Step 1, KR desulfurization, wherein after KR desulfurization is carried out on molten iron, 4.1-4.5% of molten iron C and 0.003-0.008% of S are obtained, and the temperature is 1300-1360 ℃; Smelting in a converter, namely adding desulfurized molten iron and high-quality scrap steel into the converter for smelting, wherein the ratio of the scrap steel is 15-20%, the molten steel C at the smelting end point of the converter is 0.03-0.06%, O is 0.040-0.075%, P is less than or equal to 0.018%, S is less than or equal to 0.015%, the temperature is more than 1630 ℃, the alkalinity CaO/SiO2=2.5-3.0 and T.Fe is 13-18%; Tapping in a converter, when the S content in molten steel is 0.010-0.015%, adding alloy according to the sequence of ferrosilicon and high silicon-manganese after the converter taps 25%, adding sulfur-containing slag and alloy according to the sequence of sulfur-containing slag, ferrosilicon and high silicon-manganese before tapping is finished, when the S content in molten steel is less than or equal to 0.010%, adding sulfur-containing slag and alloy before tapping is finished, adding calcium silicate synthetic slag, fully opening ladle bottom blowing and stirring in the whole tapping process, stirring for 3-5min after the synthetic slag is added, obtaining slag basicity CaO/SiO 2 = 0.4-0.7, and the content of T.Fe+MnO is 3-5%, and then carrying out LF refining treatment; Step 4, LF refining, in-station LF refining, sampling and measuring molten steel and slag chemical components, carrying out ladle bottom blowing stirring, after molten steel and slag components are tested out, adding low-titanium low-aluminum ferrosilicon and manganese metal into the molten steel according to target components of steel types to adjust the molten steel components to reach the target components, adding lime and silicon carbide to adjust the slag components to obtain slag basicity CaO/SiO 2 =0.9-1.2 and content of T.Fe+MnO of 2.5-4.5%, then starting electrifying and heating to enable the temperature of the molten steel to reach a target value, then adjusting the ladle bottom blowing to be in a soft stirring mode, and carrying out continuous casting and pouring on the molten steel after soft stirring is finished; and 5, continuous casting protection pouring. Further, in the step 1, in the KR desulfurization process, molten iron samples are taken at intervals of 3-5min to analyze the S content, and when the S content is 0.003-0.008%, the desulfurization is stopped, and the slag removal treatment is performed, wherein the slag removal rate is not less than 95%. Further, in the step 2, the high-quality scrap steel contains 0.005-0.015% of S, less than or equal to 0.02% of P, and the ba