Method for preparing welding wire steel ER70S-6X at low cost

Abstract

The invention discloses a low-cost method for preparing welding wire steel ER70S-6X, which comprises the following steps: step 1, preparing high-quality scrap steel and molten iron with S in less than or equal to 0.030%; secondly, the molten iron and the high-quality scrap steel in the first step are fed into a top-bottom combined blowing converter to be subjected to converter blowing; thirdly, the molten steel treated in the converter procedure in the second step is fed into an LF ladle refining furnace to be refined, and SiCaBa or SiFe or SiMn is adopted for deoxidation in the refining process; and fourthly, the molten steel treated through the refining procedure in the third step is fed into a square billet continuous casting machine, square billets are produced, and the welding wire steel ER70S-6X is obtained. According to the method, the C content of the molten steel at the end point of the converter is controlled to be 0.04% or below mainly by exerting the advantages of the top-bottom combined blowing high-capacity converter, meanwhile, expensive low-carbon ferromanganese is replaced with low-price SiFe and SiMn alloy, the cost is greatly reduced, it is ensured that the components of the molten steel reach the control standard, and the cost is reduced by 70 yuan per ton of steel or above on the year-on-year basis.

Description

Technical Field

[0001] The invention relates to the technical field of welding wire steel preparation, and in particular to a low-cost welding wire steel preparation method. Background Art

[0002] Carbon dioxide gas shielded welding is mainly used in machinery manufacturing, automobile industry, container pressure vessels, shipbuilding and other fields. It has the advantages of low welding cost, high efficiency, good weld formation and strong operability. Welding wire steel ER70S-6X is the main raw material for making carbon dioxide shielded solid welding wire. With the promotion and application of China's welding automation technology and the continuous improvement of welding quality requirements, the market demand for welding wire steel ER70S-6X has been increasing year by year. However, the existing preparation method of welding wire steel ER70S-6X requires the use of high-priced low-carbon ferromanganese to ensure that the molten steel composition meets the control standard, but its preparation cost is relatively high, which is not conducive to increasing the market share of this welding wire steel. Summary of the invention

[0003] The purpose of the present invention is to provide a method for preparing low-cost welding wire steel ER70S-6X wire rod, so as to solve the technical problem that the existing preparation method needs to use high-priced low-carbon ferromanganese, resulting in high preparation cost.

[0004] To achieve its purpose, the present invention adopts the following technical solutions: A method for preparing welding wire steel ER70S-6X at low cost comprises the following steps: Step 1: prepare high-quality scrap steel and molten iron, wherein S in the molten iron is ≤ 0.030%; Step 2: feeding the molten iron in step 1 into a top and bottom double-blown converter for converter blowing, using SiCaBa, SiFe or SiMn for deoxidation and alloying; Step 3, sending the molten steel treated in the converter process in step 2 to the LF ladle refining furnace for refining; Step 4: Feed the molten steel processed in the refining process in step 3 into a billet continuous casting machine to produce billets to obtain welding wire steel ER70S-6X.

[0005] As a further improvement of the technical solution of the present invention, the converter blowing process in step 2 is specifically as follows: S1, converter assembly is controlled at 132±1 tons, molten iron 116 tons, high-quality scrap steel 16 tons; S2, the amount of lime added is calculated according to the Si content of the molten iron, so that the basicity of the slag is controlled to 3.0, and the converter bottom blowing adopts the nitrogen-argon switching mode; S3, during converter blowing, the temperature of molten steel is controlled at 1650-1670℃, and the oxygen is determined by deep blowing at the end low lance position for more than 2 minutes, and the end oxygen is controlled within 600PPm; S4, slag is controlled during the steel-making process. The converter adopts slide plate slag blocking technology and the slag amount is controlled within 400kg. When the steel-making amount is 1 / 3 of the molten steel, SiFe and SiMn are added with the steel flow. When the steel-making amount is 4 / 5 of the molten steel, SiCaBa is added, and the amount added is about 150kg / furnace.

[0006] Furthermore, the molten steel treated in the converter process in step 2 is fed into the LF ladle refining furnace, small-grained lime and fluorite are added during the refining process for slag making, and SiFe and SiMn are used for alloy fine-tuning.

[0007] Furthermore, 200 kg / furnace of small-grained lime is added to the molten steel when it is fed into the LF ladle refining furnace, and argon is blown and stirred for 3-5 minutes after the steel is tapped, and the liquid surface opening is adjusted to 200-300 mm.

[0008] Furthermore, the refining furnace process in step 3 is specifically as follows: S1, the temperature of molten steel entering LF ladle refining furnace is ≥1550℃, 400kg of active lime and 100kg of fluorite are added in batches for desulfurization; S2, LF ladle refining furnace adopts micro-positive pressure operation. After slag formation, cheap SiMn is used to replace low-carbon ferromanganese for alloy fine-tuning to reduce costs; S3, during the refining process, the slag is controlled to be grayish white (FeO+MnO) ≤ 2%, and the slag basicity is controlled at 2.0-2.5; S4, before leaving the station, clean blowing is performed for more than 8 minutes to determine the oxygen, and a carbon-free covering agent with a carbon content of less than 0.5% is added to obtain molten steel leaving the station.

[0009] Furthermore, the composition of the outgoing molten steel, measured by weight percentage, includes C 0.04-0.06%, Si 0.80-0.95%, Mn 1.40-1.60%, P≤0.020%, and S≤0.020%.

[0010] Furthermore, the continuous casting process in step 4 is specifically as follows: The liquidus temperature is 1515℃, the normal tundish temperature is 1535~1555℃, special protective slag for welding wire steel and carbon-free covering agent are added, and the whole process of argon sealing flow protection pouring is adopted; the pouring and drawing speed is 2.4-2.6m / min.

[0011] Furthermore, the water volume in the mold during the continuous casting process is controlled to be 125-135 m 3 / h, the secondary cooling water adopts strong cooling method, and the specific water volume is 1.72~1.76L / kg.

[0012] Furthermore, the time of the converter process in step 2 is controlled within 38 to 42 minutes; the time of the refining furnace process in step 3 is controlled within 40 to 55 minutes; and the time of the continuous casting process in step 4 is controlled within 40 to 50 minutes.

[0013] Compared with the existing method for preparing welding wire steel ER70S-6X wire rod, the beneficial effects of the present invention are: 1. The present invention takes advantage of the top and bottom combined blowing large-capacity converter to ensure that the C content of the converter end molten steel is controlled below 0.06%. At the same time, low-priced SiFe and SiMn alloys are used instead of expensive low-carbon ferromanganese to achieve a significant reduction in cost and ensure that the composition of the molten steel meets the control standard, achieving a year-on-year cost reduction of more than 70 yuan / ton of steel; 2. A reasonable cooling mode is adopted in the continuous casting process to ensure the quality of the ingot while achieving high-speed casting. The defects such as center segregation, center porosity, and internal cracks of the ingot are below level 1.0. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The present invention is a process flow chart of the method for preparing welding wire steel ER70S-6X at low cost. DETAILED DESCRIPTION

[0015] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The embodiments are only used to explain the present invention and are not used to limit the scope of the present invention. The present invention is described in more detail by way of example with reference to the accompanying drawings in the following paragraphs. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0016] Example 1 A method for preparing welding wire steel ER70S-6X at low cost comprises the following steps: Step 1, preparing high-quality scrap steel and molten iron, wherein the S content in the molten iron is 0.030%; Step 2, sending the molten iron in step 1 into a top and bottom double-blown converter for converter blowing; The converter process is as follows: S1, converter total load 132 tons, hot metal 116 tons, high-quality scrap steel 16 tons; S2, the amount of lime added is calculated according to the Si content of the molten iron, so that the basicity of the slag is controlled to 3.0, and the converter bottom blowing adopts the nitrogen-argon switching mode; S3, the temperature of the steel in the converter blowing is controlled at 1650℃, and the end point low lance deep blowing is used for more than 2 minutes to determine the oxygen; S4, the sliding plate slag blocking technology is used to control the slag during the steel tapping process. When the steel tapping amount is 1 / 3 of the molten iron, SiFe is added with the steel flow. When the steel tapping amount is 4 / 5 of the molten iron, SiCaBa is added. The added amount is 150kg / furnace. The molten steel treated in the converter process of step 2 is sent to the LF ladle refining furnace. During the refining process, 200 kg / furnace of small-grained lime is added. After tapping, argon is blown and stirred for 3 minutes, and the liquid level is adjusted to 200 mm. Step 3: sending the molten steel after the converter process in step 2 to the LF ladle refining furnace for refining, adding small lime and fluorite for slag making during the refining process, and using SiFe and SiMn for alloy fine-tuning; The refining furnace process in step 3 is as follows: S1, the temperature of molten steel entering LF ladle refining furnace is 1550℃, 400kg of active lime and 100kg of fluorite are added in batches; S2, LF ladle refining furnace adopts micro-positive pressure operation. After slag formation, low-priced SiMn is selected to replace high-priced low-carbon ferromanganese for fine-tuning of the composition according to the composition of the refined molten steel; S3, the refining process controls the slag to be off-white, and the slag basicity is controlled at 2.0; S4, before leaving the station, clean blowing for more than 8 minutes to determine oxygen, and add carbon-free covering agent with C content less than 0.5% to obtain molten steel. The components of the molten steel are calculated by weight percentage, including C 0.04%, Si 0.80%, Mn 1.40%, P 0.020%, S0.020%; Step 4: Feed the molten iron processed in the refining process in step 3 into a billet continuous casting machine to produce billets to obtain welding wire steel ER70S-6X.

[0017] The continuous casting process is as follows: The liquidus temperature is 1515℃, the normal tundish temperature is 1530℃, the whole process of argon sealing flow protection casting is adopted, the casting process uses special protective slag for welding steel crystallizer, and the tundish uses carbon-free covering agent to cover the tundish steel liquid surface; the casting speed is 2.4m / min, keep stable, control the large ladle filling margin, and strictly prohibit large ladle slag. The water volume of the crystallizer in the continuous casting process is controlled to 125m 3 / h, the secondary cooling water adopts the second type of cooling method, and the specific water volume is 1.72L / kg.

[0018] The present invention strictly controls the refining cycle to within 50 minutes, thereby reducing the energy medium consumption in the refining process. At the same time, continuous casting achieves high-speed casting by optimizing the matching relationship between the ladle temperature in the molten steel and the casting speed of the casting machine. The normal casting speed of the casting machine can reach 2.6 m / min, which is about 0.5 to 0.6 m / min higher than the average casting speed of other plants.

[0019] Example 2 The difference between Example 2 and Example 1 is that in step 2, the temperature of the steel in the converter blowing is controlled at 1660°C; after the steel is tapped, argon is blown and stirred for 4 minutes, and the liquid level is adjusted to 250mm; in step 3, in the refining furnace process, the slag basicity is controlled at 2.3; in step 4, in the continuous casting process, the normal tundish temperature is 1540°C, the casting speed is 2.5m / min, and the water volume of the crystallizer is controlled to 130m 3 / h, the secondary cooling water adopts strong cooling method, and the specific water volume is 1.74L / kg; The final outgoing molten steel composition of Example 2, by weight percentage, contains C 0.05%, Si 0.87%, Mn 1.50%, P 0.190%, and S 0.180%.

[0020] Example 3 The difference between Example 3 and Example 1 is that in step 2, the temperature of the steel in the converter blowing is controlled at 1670°C; after the steel is tapped, argon is blown and stirred for 5 minutes, and the liquid level is adjusted to 300mm; in step 3, in the refining furnace process, the slag basicity is controlled at 2.5; in step 4, in the continuous casting process, the normal tundish temperature is 1550°C, the casting speed is 2.6m / min, and the water volume of the crystallizer is controlled to 135m 3 / h, the secondary cooling water adopts strong cooling method, and the specific water volume is 1.76L / kg; The final outgoing molten steel composition of Example 3, by weight percentage, contains C 0.06%, Si 0.95%, Mn 1.60%, P 0.180%, and S 0.020%.

[0021] The converter of the present invention focuses on controlling the carbon content of the steel to ensure that the C content is below 0.06%. At the same time, through alloy optimization, low-priced SiFe and SiMn alloys are used to replace expensive low-carbon ferromanganese, thereby significantly reducing costs. The comparison table of the alloy cost of Example 1 of the present invention and the original solution using low-carbon ferromanganese is as follows: According to the above calculation, the cost of producing welding wire steel alloy according to the present invention is reduced by 71.9 yuan / ton of steel compared with the original solution. The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the field can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing welding wire steel ER70S-6X at low cost, characterized in that: The following steps are involved: Step 1: prepare high-quality scrap steel and molten iron, wherein S in the molten iron is ≤ 0.030%; Step 2: feeding the molten iron in step 1 into a top and bottom double-blown converter for converter blowing, using SiCaBa, SiFe or SiMn for deoxidation and alloying; Step 3, sending the molten steel treated in the converter process in step 2 to the LF ladle refining furnace for refining; Step 4: Feed the molten steel processed in the refining process in step 3 into a billet continuous casting machine to produce billets to obtain welding wire steel ER70S-6X.

2. The method for preparing welding wire steel ER70S-6X at low cost according to claim 1, characterized in that: The converter blowing process in step 2 is specifically as follows: S1, converter assembly is controlled at 132±1 tons, molten iron 116 tons, high-quality scrap steel 16 tons; S2, the amount of lime added is calculated according to the Si content of the molten iron, so that the basicity of the slag is controlled to 3.0, and the converter bottom blowing adopts the nitrogen-argon switching mode; S3, during converter blowing, the temperature of molten steel is controlled at 1650-1670℃, and the oxygen is determined by deep blowing at the end low lance position for more than 2 minutes, and the end oxygen is controlled within 600PPm; S4, slag is controlled during the steel-making process. The converter adopts slide plate slag blocking technology and the slag amount is controlled within 400kg. When the steel-making amount is 1 / 3 of the molten steel, SiFe and SiMn are added with the steel flow. When the steel-making amount is 4 / 5 of the molten steel, SiCaBa is added, and the amount added is about 150kg / furnace.

3. A method for preparing welding wire steel ER70S-6X at low cost according to claim 1 or 2, characterized in that: The molten steel treated in the converter process in step 2 is sent to the LF ladle refining furnace. During the refining process, small-grained lime and fluorite are added for slag making, and SiFe and SiMn are used for alloy fine-tuning.

4. The method for preparing welding wire steel ER70S-6X at low cost according to claim 3, characterized in that: When the molten steel is fed into the LF ladle refining furnace, 200 kg of small-grained lime is added per furnace. After the steel is tapped, argon is blown and stirred for 3-5 minutes, and the liquid surface opening is adjusted to 200-300 mm.

5. A method for preparing welding wire steel ER70S-6X at low cost according to any one of claims 1, 2 and 4, characterized in that: The refining furnace process in step 3 is as follows: S1, the temperature of molten steel entering LF ladle refining furnace is ≥1550℃, 400kg of active lime and 100kg of fluorite are added in batches for desulfurization; S2, LF ladle refining furnace adopts slightly positive pressure operation, and after slag formation, SiMn is selected for alloy fine-tuning; S3, during the refining process, the slag is controlled to be grayish white (FeO+MnO) ≤ 2%, and the slag basicity is controlled at 2.0-2.5; S4, before leaving the station, clean blowing is performed for more than 8 minutes to determine the oxygen, and a carbon-free covering agent with a carbon content of less than 0.5% is added to obtain molten steel leaving the station.

6. The method for preparing welding wire steel ER70S-6X at low cost according to claim 5, characterized in that: The composition of the molten steel leaving the station, measured by weight percentage, contains C 0.04-0.06%, Si 0.80-0.95%, Mn 1.40-1.60%, P≤0.020%, and S≤0.020%.

7. The method for preparing welding wire steel ER70S-6X at low cost according to claim 6, characterized in that: The continuous casting process in step 4 is specifically as follows: The liquidus temperature is 1515℃, the normal tundish temperature is 1535~1555℃, special protective slag for welding wire steel and carbon-free covering agent are added, and the whole process of argon sealing and injection flow protection casting is adopted.

8. The method for preparing welding wire steel ER70S-6X at low cost according to claim 7, characterized in that: The pouring speed is 2.4-2.6 m / min.

9. The method for preparing welding wire steel ER70S-6X at low cost according to claim 8, characterized in that: The water volume in the mold during the continuous casting process is controlled at 125-135m 3 / h, the secondary cooling water adopts strong cooling method, and the specific water volume is 1.72~1.76L / kg.

10. A method for preparing welding wire steel ER70S-6X at low cost according to any one of claims 1-2 and 6-9, characterized in that: The time of the converter process in step 2 is controlled within 38 to 42 minutes; the time of the refining furnace process in step 3 is controlled within 40 to 55 minutes; and the time of the continuous casting process in step 4 is controlled within 40 to 50 minutes.

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