A production process of low-carbon low-silicon aluminum-containing steel billet

Abstract

The present application relates to a kind of billet low-carbon low-silicon aluminum-containing steel production process, its preparation procedure includes the steps of molten iron pretreatment, converter, LF refining and continuous casting, wherein converter process is: control oxygen content, endpoint oxygen is 550~700ppm, aluminum content is controlled as 0.010%~0.040%, endpoint temperature is ≥1640 ℃;LF refining process is: using micro-positive pressure operation, calcium carbide is added in batches, buried arc slagging, fast slagging, when deoxidizing, aluminum particle needs to be added in multiple times, less and frequent, secondary aluminum adjustment ensures soft argon blowing time ≥5 minutes.The method is reasonably designed by converter+LF refining process in production process, solve the phenomenon of billet low-carbon low-silicon aluminum-containing steel production process C and Si, also guarantee the castability of molten steel.The prepared billet low-carbon low-silicon aluminum-containing steel C:≤0.07%, Si:≤0.09%, Als:0.020~0.045%, meet the quality requirements of billet low-carbon low-silicon aluminum-containing steel.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical material preparation, specifically relating to a production process for low-carbon, low-silicon aluminum-containing steel billets. Background Technology

[0002] Cold heading steel wire rod is generally made of low- and medium-carbon high-quality carbon structural steel and alloy structural steel. Its products are mainly used in the automotive, shipbuilding, equipment manufacturing, electronics, home appliance, bicycle, tool, light steel structure, and construction industries. It is the main raw material for cold heading steel forming and can be used to manufacture fasteners and connectors (such as bolts, nuts, screws, rivets, etc.) through cold heading. It is one of the high-end, high-value-added brand steel grades in high-speed wire rod products.

[0003] Low-carbon, low-silicon aluminum-containing steel has advantages such as strict chemical composition requirements, stable composition, low levels of harmful elements, high steel purity, high dimensional accuracy, few surface defects, and stable cold heading performance. Without heat treatment, the parts deform significantly during the cold heading process, and the forming speed is fast. To avoid defects such as cracks, the wire rod should have low tensile strength and a small performance fluctuation range. This results in high processing efficiency and reduces wear and tear on the user's molds.

[0004] Therefore, the development of a billet low-carbon, low-silicon aluminum-containing steel that can guarantee both low-carbon and low-silicon composition requirements and castability, while also meeting quality requirements, and thus enabling mass industrial production of billet low-carbon, low-silicon aluminum-containing steel, has significant economic value and broad market prospects. Summary of the Invention

[0005] To achieve the above objectives, this invention provides a production process for low-carbon, low-silicon, aluminum-containing steel billets. The process involves a rational design of the converter + LF refining process, addressing the issues of carbon increase and silicon reversion during the production of low-carbon, low-silicon, aluminum-containing steel billets, while also ensuring the castability of the molten steel. This process meets the quality requirements for low-carbon, low-silicon, aluminum-containing steel billets.

[0006] The specific details of the invention are as follows:

[0007] This invention provides a production process for low-carbon, low-silicon, aluminum-containing steel billets. The preparation process of the low-carbon, low-silicon, aluminum-containing steel billets includes the steps of hot metal pretreatment, converter, LF refining, and continuous casting. The converter process involves controlling the oxygen content, with an endpoint oxygen level of 550–700 ppm, controlling the aluminum content to 0.010%–0.040%, and setting the endpoint temperature ≥1640℃ to avoid low temperatures, which can lead to poor decarburization due to argon blowing and stirring, resulting in high carbon content.

[0008] The LF refining process involves: micro-positive pressure operation, batch addition of calcium carbide, submerged arc slag formation, and rapid slag formation, which facilitates the flotation of inclusions and ensures the castability of molten steel and product quality. During the later deoxidation stage, aluminum granules must be added in multiple small, frequent additions; concentrated addition of aluminum granules to adjust the composition while simultaneously deoxidizing is prohibited, as this is a primary means of controlling the return of Si to the molten steel. Secondary aluminum adjustment ensures a soft-blowing argon time of ≥5 minutes.

[0009] Furthermore, in the converter process, if the oxygen content is <700ppm, the converter is executed according to the carbon deoxidation process, and the oxygen content is fixed at 3-5ppm after argon blowing for 3 minutes. Aluminum wire is added according to the fixed oxygen value; if the oxygen content is ≥700ppm, the aluminum deoxidation alloying process is executed.

[0010] Preferably, in the converter process, the aluminum content is controlled to be 0.010% to 0.025%.

[0011] Preferably, the aluminum particles are added ≥3 times.

[0012] Preferably, the amount of aluminum granules added is 20-30 kg / t.

[0013] Furthermore, the billet low-carbon low-silicon aluminum-containing steel prepared using the above production process has the following properties: C: ≤0.07%, Si: ≤0.09%, and Als: 0.020–0.045%.

[0014] The beneficial effects of this invention are as follows:

[0015] ①This invention solves the problem of increased carbon and reversion of silicon in the production process of low-carbon, low-silicon aluminum-containing steel billets by rationally designing the converter + LF refining process, while also ensuring the castability of molten steel.

[0016] ② It meets the product quality requirements for low-carbon, low-silicon aluminum-containing steel billets in terms of chemical composition, mechanical properties, metallographic structure, non-metallic inclusions, and 1 / 3 cold upsetting. Attached Figure Description

[0017] Figure 1 This is a metallographic diagram of Embodiment 1 of the present invention.

[0018] Figure 2 This is a 1 / 3 cold top upsetting diagram of Embodiment 1 of the present invention. Detailed Implementation

[0019] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the present invention, but do not limit the invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0020] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0021] Example 1

[0022] After the molten iron pretreatment step, it is smelted in a converter. Low-carbon, low-silicon, aluminum-containing billet steel with an endpoint oxygen content of 550–700 ppm is selected. The carbon deoxidation process is followed, with argon blowing at the argon station for 3 minutes to set the oxygen content to 3–5 ppm, and the aluminum content controlled at 0.010%. The LF refining furnace operates under slight positive pressure. Slag formation begins during slag formation, requiring rapid slag formation (green slag after the first energization, white slag after the second energization). During the later deoxidation stage, aluminum particles are added in four batches: 20 kg / t, 25 kg / t, 25 kg / t, and 20 kg / t respectively. The soft argon blowing time is 7 minutes.

[0023] Example 2

[0024] After the molten iron pretreatment step, the steel is smelted in a converter. Low-carbon, low-silicon, aluminum-containing billets with an oxygen content ≥700ppm are selected. The aluminum deoxidation and alloying process is followed. After argon blowing for 3 minutes, the oxygen content is set at 4ppm, and the aluminum content is controlled at 0.020%. The LF refining furnace operates under slight positive pressure. Slag formation begins during slag formation, requiring rapid slag formation (green slag after the first energization, white slag after the second energization). During the later deoxidation stage, aluminum particles are added in three batches: 30kg / t, 20kg / t, and 20kg / t respectively. The soft argon blowing time is 6 minutes.

[0025] Example 3

[0026] After the molten iron pretreatment step, it is smelted in a converter. Low-carbon, low-silicon, aluminum-containing billet steel with an oxygen content of 550-700 ppm is selected. The carbon deoxidation process is carried out, and the oxygen content is fixed at 4 ppm after argon blowing for 3 minutes. The aluminum content is controlled at 0.015%. The LF refining furnace is operated under slight positive pressure. Slag formation begins during slag formation, requiring rapid slag formation (green slag after the first energization and white slag after the second energization). During the later deoxidation, aluminum particles are added in three batches, at 20 kg / t, 30 kg / t, and 20 kg / t respectively. The soft argon blowing time is 5 minutes.

[0027] Example 4

[0028] After the molten iron pretreatment step, it is smelted in a converter. Low-carbon, low-silicon, aluminum-containing billet steel with an oxygen content of 550-700 ppm is selected. The carbon deoxidation process is carried out, and the oxygen content is fixed at 5 ppm after argon blowing for 3 minutes. The aluminum content is controlled at 0.025%. The LF refining furnace is operated under slight positive pressure. Slag formation begins during slag formation, requiring rapid slag formation (green slag after the first energization and white slag after the second energization). During the later deoxidation, aluminum particles are added in three batches, at 20 kg / t, 25 kg / t, and 20 kg / t respectively. The soft argon blowing time is 6 minutes.

[0029] Product inspection and performance testing

[0030] The final products of Examples 1-4 were subjected to chemical composition testing, low-magnification defect testing of the cast billet, mechanical properties testing, microstructure testing, non-metallic inclusion testing, and cold upsetting testing, respectively. The test results are shown in Tables (1)-(4). Figure 1 and Figure 2 As shown:

[0031] Table (1) Results of Chemical Composition Tests:

[0032] standard ≤0.07 ≤0.09 0.020～0.045 Example 1 0.07 0.06 0.035 Example 2 0.06 0.07 0.039 Example 3 0.07 0.05 0.044 Example 4 0.07 0.04 0.039

[0033] Table (2) Results of low-magnification defect inspection of cast billets:

[0034]

[0035]

[0036] Table (3) Mechanical Properties

[0037] 350 40.5 79 352 43 78 360 42.5 77 366 43 78

[0038] Table (4) Microstructure and non-metallic inclusions:

[0039]

[0040] From Tables (1) to (4) and Figure 1 and Figure 2 The test results show that the production process of low-carbon, low-silicon aluminum-containing steel billets enables the products to meet the user's quality requirements.

Claims

1. A process for producing low-carbon, low-silicon aluminum-containing steel billets, characterized in that: The preparation process of the billet low-carbon low-silicon aluminum-containing steel includes the steps of hot metal pretreatment, converter, LF refining and continuous casting. The converter process is as follows: oxygen content is controlled, the final oxygen content is 550-700 ppm, the aluminum content is controlled at 0.010%-0.040%, and the final temperature is ≥1640℃. The LF refining process is as follows: micro-positive pressure operation, calcium carbide is added in batches, submerged arc slag formation is carried out, slag is formed quickly, aluminum particles need to be added in multiple times during deoxidation, adding small amounts frequently, and secondary aluminum adjustment to ensure that the soft blowing argon time is ≥5 minutes. The billet low-carbon, low-silicon aluminum-containing steel has the following composition: C: ≤0.07%, Si: ≤0.09%, Als: 0.020~0.045%.

2. The process according to claim 1, characterized in that: In the converter process, if the oxygen content is <700ppm, the converter is executed according to the carbon deoxidation process. After blowing argon for 3 minutes, the oxygen content is fixed at 3-5ppm, and aluminum wire is added according to the fixed oxygen value. If the oxygen content is ≥700ppm, the aluminum deoxidation alloying process is executed.

3. The process according to claim 1, characterized in that: In the converter process, the aluminum content is controlled to be 0.010% to 0.025%.

4. The process according to claim 1, characterized in that: The aluminum particles are added ≥3 times.

5. The process according to claim 1, characterized in that: The amount of aluminum granules added is 20-30 kg / t.

Images