Production method of steel for manufacturing welding stud after cold heading with mark of ML5Al

Abstract

The invention discloses a production method for manufacturing welding stud steel after cold heading with the mark of ML5Al. The main production process comprises the steps of blast furnace molten iron pretreatment, converter top and bottom combined blowing smelting, LF refining, 150mm * 150mm continuous casting of small square billets, slow cooling for 48 hours and rolling in a long material factory. The method comprises the steps of billet heating, high-pressure water descaling, rough rolling, intermediate rolling, finish rolling, cooling water tank control, spinning, stelmor cooling, coil collecting, trimming, sampling inspection, collecting and bundling, weighing and finished wire rod obtaining. The welding stud made of the ML15Al cold heading steel has high strength, good toughness and shear resistance, the tensile strength can be stabilized within 450 MPa, the area reduction rate is larger than or equal to 50%, the percentage elongation after fracture is larger than or equal to 30%, and the product size and appearance are free of defects. And various complex and harsh wind power construction working condition requirements can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy and rolling, and in particular relates to a production method of steel with a grade of ML5Al for making welding studs after cold heading. Background Art

[0002] Cold heading steel is a type of steel designed for cold heading process. They must have excellent mechanical properties and processing characteristics to withstand the high pressure and large deformation during cold heading process. This type of steel usually has high yield strength and good plasticity, which enables them to be cold pressed without breaking. The surface finish and dimensional accuracy of cold heading steel are also crucial, because these characteristics directly affect the quality and performance of the final product. ML15Al cold heading steel has good cold plastic deformation ability and can be processed by upsetting, punching, stretching and other processes through dies at room temperature to make parts of various shapes and sizes. Welding nails, also known as studs or shear nails, are a type of connector widely used in steel structures. They are usually used to connect components such as steel plates or steel beams together to improve the strength and stability of the overall structure. Welding nails made of ML15Al cold heading steel have high strength, good toughness and shear resistance, and can meet various complex and demanding working conditions. The welding nails made of ML15Al cold heading steel invented in this article are mainly used for connecting and fixing anchor plates in wind power towers. The excellent performance and wide application fields of ML15Al make it an indispensable part of wind power engineering. Summary of the invention

[0003] The purpose of the present invention is to provide a production method for producing welding nail steel with a grade of ML5Al cold heading, so that the welding nail made of ML15Al cold heading steel has high strength, good toughness and shear resistance, can stabilize the tensile strength within 450MPa, the area reduction rate is greater than or equal to 50%, the elongation after fracture is greater than or equal to 30%, and the product size and appearance have no defects, and can meet various complex and harsh wind power construction working conditions.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention discloses a production method for producing steel for welding nails after cold heading with a grade of ML5Al, and the main production process includes: blast furnace molten iron - molten iron pretreatment - converter top and bottom blowing smelting - LF refining - small square billet continuous casting 150mm*150mm - slow cooling for 48 hours - long product factory rolling; billet heating - high-pressure water descaling - rough rolling - medium rolling - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod; the characteristics are:

[0006] The key points of desulfurization process control are:

[0007] The materials used must be dry and free of inclusions. Special scrap steel is preferred, with 10 to 20 tons of scrap steel.

[0008] Key points of converter process control:

[0009] Low-high-low gun position control is adopted, and the gun position is 1.1-1.5m; single slag or double slag is adopted according to the molten iron conditions, the end point basicity is controlled at 2.7-3.5, the end point control target C≥0.06%, T≥1610℃; the final deoxidation adopts Al deoxidation;

[0010] Key points for controlling the refining process:

[0011] Refining in-situ heating for 8min-10min, according to the slag surface of molten steel in place, according to the in-situ temperature and production sequence, further heating time is estimated, the heating efficiency is calculated at 4℃ / min, and lime is added during the heating process; after lifting the electrode each time, dip the slag sample, add lime according to the color and viscosity of the slag, and add 2-3 bags of aluminum particles, each bag of 10KG aluminum particles, to the lower electrode until the white slag is formed before the temperature is raised;

[0012] Key points for continuous casting process control:

[0013] Before the first ladle is poured, argon gas is filled into the tundish for more than 3 minutes to purge and replace the air to reduce oxidation of molten steel; after the tundish car is centered, the large ladle can be poured, and the covering agent can be added when the molten steel in the tundish reaches 12 tons. It is not allowed to add it too early to avoid mixing slag and carbon increase; the liquid level in the impact zone of the T-shaped mouth of the tundish must not leak red during the pouring process; the liquid level of the tundish is controlled at 750-800mm during normal pouring; the normal pouring liquid level is not allowed to be lower than 400mm, and the stop pouring liquid level is not less than 250mm; the submerged nozzle is replaced every 5-6 hours. If the submerged nozzle has any abnormal reaction during the pouring process, it should be replaced immediately; the submerged nozzle of the tundish must be aligned with the upper mouth of the crystallizer, with a deviation of ≤5mm, and protected by an argon sealing ring;

[0014] Steel rolling improvement plan:

[0015] 1) The heating temperature of the heating furnace is increased from 1080℃-1160℃ to 1100℃-1180℃ to fully austenitize the billet structure;

[0016] 2) Due to the production of large-size coils of φ18mm-φ22mm, the rough rolling temperature is adjusted to 950±30℃, the finishing rolling temperature is adjusted to 930±20℃, and the wire laying temperature is increased from 880±20℃ to 900±20℃. The main purpose of increasing the wire laying temperature is to ensure the clean removal of the iron oxide scale;

[0017] 3) The opening degree of the heat preservation cover is changed from fully closed to open every three;

[0018] 4) The speed of the slow cooling line roller is set as follows: entrance 0.46m / s, first section 0.47m / s, second section 0.48m / s, third section 0.49m / s, fourth section 0.54m / s, fifth section 0.55m / s, sixth section 0.60m / s, seventh section 0.64m / s, eighth section 0.64m / s, exit 0.66m / s.

[0019] Furthermore, the mass percentage chemical composition of the steel with the grade ML5Al for making welding studs after cold heading is: C: 0.13-0.18%; Si: 0.07-0.10%; Mn: 0.30-0.60%; P≤0.025%; S: ≤0.025%; residual element Ni≤0.25%; Cr≤0.25%; Cu≤0.20%, and the remainder is Fe and a small amount of impurity elements.

[0020] Furthermore, the amount of deoxidizer added is: 80% aluminum iron 200-300kg / furnace.

[0021] Furthermore, it also includes: 5) Check the rolling equipment in advance to prevent the roller ring groove from falling off, the guide guard from being installed skewed, the imported guide guard from being broken or severely worn, and the guide guard from being improperly installed and designed, to ensure that there are no scratches on the product surface.

[0022] Furthermore, the mechanical properties of the product are stable and meet the following requirements: tensile strength ≤ 450MPa, surface shrinkage ≥ 50%, and elongation after break ≥ 30%.

[0023] Compared with the prior art, the beneficial technical effects of the present invention are:

[0024] The method of the present invention makes the welding nail made of ML15Al cold heading steel have high strength, good toughness and shear resistance, and can stabilize the tensile strength within 450MPa, the area shrinkage is greater than or equal to 50%, the elongation after fracture is greater than or equal to 30%, and the product size and appearance have no defects, which can meet various complex and harsh wind power construction working conditions. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments.

[0026] 1. Strictly control the size and surface quality of the finished product, as shown in the following table:

[0027]

[0028] 2. The results of constant pulling speed control are shown in the following table:

[0029]

[0030]

[0031] Through the implementation of the steelmaking continuous casting improvement plan, the improved continuous casting billet drawing speed is stably controlled, preventing the occurrence of corner cracks, inter-cracks and central shrinkage holes during the continuous casting process.

[0032] All five groups of experiments were produced using the following rolling parameters, the specific parameters are shown in the following table:

[0033] Rolling process parameters of each embodiment:

[0034]

[0035] The chemical compositions of the embodiments are shown in the following table:

[0036]

[0037] 3. The improvement of the stability of the product's mechanical properties is shown in the following table.

[0038]

[0039] Through the implementation of the steel rolling improvement plan, the mechanical properties of the products fully meet the design requirements.

[0040] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A production method for making welding nail steel with the grade of ML5Al after cold heading, the main production process: blast furnace molten iron - molten iron pretreatment - converter top and bottom blowing smelting - LF refining - small square billet continuous casting 150mm*150mm - slow cooling for 48 hours - long product factory rolling; billet heating - high-pressure water descaling - rough rolling - medium rolling - finishing rolling - controlled cooling water tank - wire laying - Stelmor cooling - coiling - trimming - sampling inspection - collection and bundling - weighing - finished wire rod; it is characterized by: The key points of desulfurization process control are: The materials used must be dry and free of inclusions. Special scrap steel is preferred, with 10 to 20 tons of scrap steel. Key points of converter process control: Low-high-low gun position control is adopted, and the gun position is 1.1-1.5m; single slag or double slag is adopted according to the molten iron conditions, the end point basicity is controlled at 2.7-3.5, the end point control target C≥0.06%, T≥1610℃; the final deoxidation adopts Al deoxidation; Key points for controlling the refining process: Refining in-situ heating for 8min-10min, according to the slag surface of molten steel, the in-situ temperature and production sequence, the further heating time is estimated, the heating efficiency is calculated at 4℃ / min, and lime is added during the heating process; after lifting the electrode each time, dip the slag sample, add lime according to the color and viscosity of the slag, and add 2-3 bags of aluminum particles of 10KG each bag to the lower electrode until the white slag is formed before the temperature is raised; Key points for continuous casting process control: Before the first ladle is poured, argon gas is filled into the tundish for more than 3 minutes to purge and replace the air to reduce oxidation of molten steel; after the tundish car is centered, the large ladle can be poured, and the covering agent can be added when the molten steel in the tundish reaches 12 tons. It is not allowed to add it too early to avoid mixing slag and carbon increase; the liquid level in the impact zone of the T-shaped mouth of the tundish must not leak red during the pouring process; the liquid level of the tundish is controlled at 750-800mm during normal pouring; the normal pouring liquid level is not allowed to be lower than 400mm, and the stop pouring liquid level is not less than 250mm; the submerged nozzle is replaced every 5-6 hours. If the submerged nozzle has any abnormal reaction during the pouring process, it should be replaced immediately; the submerged nozzle of the tundish must be aligned with the upper mouth of the crystallizer, with a deviation of ≤5mm, and protected by an argon sealing ring; Steel rolling improvement plan: 1) The heating temperature of the heating furnace is increased from 1080℃-1160℃ to 1100℃-1180℃ to fully austenitize the billet structure; 2) Due to the production of large-size coils of φ18mm-φ22mm, the rough rolling temperature is adjusted to 950±30℃, the finishing rolling temperature is adjusted to 930±20℃, and the wire laying temperature is increased from 880±20℃ to 900±20℃. The main purpose of increasing the wire laying temperature is to ensure the clean removal of the iron oxide scale; 3) The opening degree of the heat preservation cover is changed from all closed to open every three; 4) The speed of the slow cooling line roller is set as follows: entrance 0.46m / s, first section 0.47m / s, second section 0.48m / s, third section 0.49m / s, fourth section 0.54m / s, fifth section 0.55m / s, sixth section 0.60m / s, seventh section 0.64m / s, eighth section 0.64m / s, exit 0.66m / s.

2. The production method of steel for welding studs after cold heading with a grade of ML5Al according to claim 1 is characterized in that: The steel with the grade of ML5Al used for making welding studs after cold heading has the following chemical compositions by mass percentage: C: 0.13-0.18%; Si: 0.07-0.10%; Mn: 0.30-0.60%; P≤0.025%; S: ≤0.025%; residual element Ni ≤0.25%; Cr ≤0.25%; Cu ≤0.20%, the balance is Fe and a small amount of impurity elements.

3. The production method of steel for welding studs after cold heading with a grade of ML5Al according to claim 1 is characterized in that: Deoxidizer addition amount: 80% aluminum iron 200-300kg / furnace.

4. The production method of steel for welding studs after cold heading with a grade of ML5Al according to claim 1 is characterized in that: Also includes: 5) Check the rolling equipment in advance to prevent problems such as roller ring groove loss, guide guide deviation, imported guide guide breakage, severe wear and tear, and improper guide guide installation design, to ensure that there are no scratches on the product surface.

5. The production method of steel for welding studs after cold heading with a grade of ML5Al according to claim 1 is characterized in that: The mechanical properties of the product are stable and meet the following requirements: tensile strength ≤450MPa, surface shrinkage ≥50%, and elongation after break ≥30%.

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