Production method of weather-proof railway base plate type steel four-stand rolling mill

Abstract

The invention discloses a production method of a weather-proof railway base plate type steel four-stand rolling mill, and belongs to the technical field of steel rolling production. According to the technical scheme, the method comprises the following steps: (1) converter smelting process: controlling the alkalinity R value of converter final slag to be not less than 3.0; (2) a continuous casting process: the temperature of a tundish is controlled to be 1535-1545 DEG C, and the pulling speed of a continuous casting billet is 0.7-0.8 m / min; (3) heating: the temperature of a preheating section is less than or equal to 920 DEG C, the temperature of a heating section is 1150-1200 DEG C, and the temperature of a soaking section is 1200-1280 DEG C; and (4) a rolling procedure is conducted, specifically, a four-rack rolling mill is adopted for rolling, two-rack reciprocating rolling is adopted for rough rolling, two-rack single-pass rolling is adopted for finish rolling, the initial rolling temperature is 1070-1120 DEG C, and the finish rolling temperature is 790-800 DEG C. The method has the beneficial effects that the hot-rolled weather-resistant railway base plate is used for replacing a traditional casting railway base plate, the production process of traditional railway base plate profile steel is simplified, and the physical performance and the weather resistance of the railway base plate profile steel are improved.

Description

Technical Field

[0001] The present invention relates to a production method of weather-resistant railway tie plate section steel by a four-stand rolling mill, belonging to the technical field of steel rolling production in the metallurgical industry. Background Art

[0002] Railway tie plate section steel is an indispensable material in railway construction and operation. It is a special steel in the railway track structure. The railway tie plate is composed of a rail seat part and a base part, and is mainly used between the rail and the sleeper. The railway tie plate section steel not only plays a role in supporting and fixing the rail, but also plays an important vibration damping and buffering function in the wheel-rail dynamic system, which helps to improve the operation stability and safety of the railway.

[0003] With the progress of science and technology and the development of railway technology, railway tie plate section steel is developing towards high performance, lightweight and environmental protection. Railway tie plates with high strength, high toughness and corrosion resistance will be more widely used.

[0004] Traditional weather-resistant railway tie plates adopt a casting process, which has problems such as low strength, complex process, low production qualification rate and poor weather resistance effect. Therefore, an invention of a production method of weather-resistant railway tie plate section steel is needed to replace casting with rolling and break the traditional casting process. Summary of the Invention

[0005] The purpose of the present invention is to provide a production method of weather-resistant railway tie plate section steel by a four-stand rolling mill, to replace the traditional cast railway tie plate with a hot-rolled weather-resistant railway tie plate, improve the physical properties and weather resistance of the railway tie plate section steel, and solve the problems existing in the background art.

[0006] The technical solution of the present invention is as follows: A production method of weather-resistant railway tie plate section steel by a four-stand rolling mill. The weather-resistant railway tie plate section steel has the following chemical composition and mass percentage content: C: 0.15 - 0.22%, Mn: 0.30 - 0.50%, Cr: 0.50 - 0.60%, Si: 0.25 - 0.35%, Cu: 0.25 - 0.35%, Ni: 0.30 - 0.40%, P: 0.008 - 0.025%, S ≤ 0.020%, and the balance is Fe and unavoidable impurities. Its production method includes converter smelting, continuous casting, heating, rolling, cooling, straightening, sawing to a fixed length and warehousing processes, wherein: (1) Converter smelting process: controlling the basicity R value of the converter final slag to be not less than 3.0; (2) Continuous casting process: controlling the tundish temperature at 1535 - 1545°C and the continuous casting billet drawing speed at 0.7 - 0.8 m / min; (3) Heating process: the preheating section temperature ≤ 920°C, the heating section temperature 1150 - 1200°C, and the soaking section temperature 1200 - 1280°C; (4) Rolling process: Four-stand rolling mill is adopted for rolling. Two-stand reciprocating rolling is used for rough rolling, and two-stand single-pass rolling is used for finish rolling. The starting rolling temperature is 1070 - 1120 °C, and the finish rolling temperature is 790 - 800 °C.

[0007] For the above production method of weathering railway tie plate section steel by four-stand rolling mill, in the converter smelting process: Copper and nickel are added into the converter together with scrap steel in the form of metal plates for preliminary melting.

[0008] For the above production method of weathering railway tie plate section steel by four-stand rolling mill, in the heating process: The temperature of the continuous casting billet entering the heating furnace is ≤80 °C. For the above production method of weathering railway tie plate section steel by four-stand rolling mill, in the heating process: The heating time of the continuous casting billet is 2.5 - 3 h.

[0009] For the above production method of weathering railway tie plate section steel by four-stand rolling mill: In the rolling process: The number of rolling passes of the continuous casting billet is 14 passes, among which, the rough rolling is 12 passes and the finish rolling is 2 passes.

[0010] For the above production method of weathering railway tie plate section steel by four-stand rolling mill: In the rolling process: The 1st - 3rd passes are reciprocating rolling box pass, the 4th - 6th passes are split pass, the 7th - 12th passes are extended rough rolling preforming pass, the 13th pass is finish rolling preforming pass, and the 14th pass is finished product pass.

[0011] The beneficial effects of the present invention are: Using hot-rolled weathering railway tie plates to replace traditional cast railway tie plates simplifies the production process of traditional railway tie plate section steel, improves the physical properties and weather resistance of railway tie plate section steel, as well as its stability in the construction and operation of steel railways. Description of the Drawings

[0012] Figure 1 is a schematic diagram of the weathering railway tie plate section steel of the present invention; Figure 2 is a schematic diagram of the box pass of the present invention; Figure 3 is a schematic diagram of the split pass of the present invention; Figure 4 is a schematic diagram of the extended rough rolling preforming pass of the present invention; Figure 5 is a schematic diagram of the finish rolling preforming pass of the present invention; Figure 6 is a schematic diagram of the finished product pass of the present invention; Detailed Embodiments

[0013] The following further illustrates the present invention through examples in conjunction with the attached drawings.

[0014] Refer to the attached Figures 1-6, A production method of weather-resistant railway tie steel by a four-stand rolling mill, the weather-resistant railway tie steel, its chemical composition and mass percentage are: C: 0.15 - 0.22%, Mn: 0.30 - 0.50%, Cr: 0.50 - 0.60%, Si: 0.25 - 0.35%, Cu: 0.25 - 0.35%, Ni: 0.30 - 0.40%, P: 0.008 - 0.025%, S ≤ 0.020%, and the balance is Fe and inevitable impurities. Its production method includes converter smelting, continuous casting, heating, rolling, cooling, straightening, sawing to a fixed length and warehousing processes, among which: (1) Converter smelting process: Control the basicity R value of the converter final slag to be not less than 3.0; (2) Continuous casting process: Control the tundish temperature at 1535 - 1545 °C, and the continuous casting billet drawing speed at 0.7 - 0.8 m / min; (3) Heating process: The preheating section temperature ≤ 920 °C, the heating section temperature 1150 - 1200 °C, and the soaking section temperature 1200 - 1280 °C; (4) Rolling process: Use a four-stand rolling mill for rolling. The rough rolling uses a two-stand reciprocating rolling, and the finish rolling uses a two-stand single-pass rolling. The rolling start temperature is 1070 - 1120 °C, and the finish rolling temperature is 790 - 800 °C.

[0015] In this embodiment, referring to the appendix Figures 1-6 , for this weather-resistant railway tie steel, its chemical composition and mass percentage are: C: 0.15 - 0.22%, Mn: 0.30 - 0.50%, Cr: 0.50 - 0.60%, Si: 0.25 - 0.35%, Cu: 0.25 - 0.35%, Ni: 0.30 - 0.40%, P: 0.008 - 0.025%, S ≤ 0.020%, and the balance is Fe and inevitable impurities. The calculation formula for the weather resistance index I is: I = 26.01(%Cu) + 3.88(%Ni) + 1.20(%Cr) + 1.49(%Si) + 17.28(%P) - 7.29(%Cu)×(%Ni) - 9.10(%Ni)×(%P) - 33.39(%Cu)², as shown in Table 1 specifically.

[0016] Table 1 Chemical composition and mass percentage (%) of weather-resistant railway tie steel in each embodiment

[0017] This weather-resistant railway tie steel, its cross-section consists of a rail seat part and a base part. The width h of the rail seat is 154 mm, and the width H of the base is 355 - 457 mm, as shown in the appendix Figure 1 shown.

[0018] The above production method of the weather-resistant rail tie steel section four-stand rolling mill includes the processes of converter smelting, continuous casting, heating, rolling, cooling, straightening, sawing to fixed length, and warehousing.

[0019] (1) Converter smelting process: Add copper and nickel metal plates together with scrap steel into the converter for preliminary melting; during the melting process, add an appropriate amount of silico-manganese alloy into the converter for alloying treatment; according to the analysis results of the chemical composition of the molten steel, add a deoxidizer into the converter to reduce the oxygen content in the molten steel; when the silicon content is insufficient, supplement an appropriate amount of ferrosilicon into the converter to ensure that the silicon content reaches the predetermined standard; by adjusting the chemical composition of the slag, control the basicity of the converter final slag to ensure that the basicity R value is not less than 3.0; (2) Continuous casting process: The molten steel is injected into the tundish through the sliding gate at the bottom of the ladle. The tundish temperature is controlled at 1535 - 1545 °C, the continuous casting billet drawing speed is 0.7 - 0.8 m / min, and the size of the continuous casting billet out of the mold is 250×460*4000 mm; (3) Heating process: Use a regenerative walking beam heating furnace for heating. The temperature of the continuous casting billet entering the heating furnace is ≤80 °C, the temperature of the preheating section of the billet entering the furnace is ≤920 °C, the heating section temperature is 1150 - 1200 °C, the soaking section temperature is 1200 - 1280 °C, and the heating time is 2.5 - 3 h; (4) Rolling process: Use the pass rolling of a four-stand rolling mill, including 12 passes of rough rolling + 2 passes of finish rolling; for rough rolling, use 2 stands of reciprocating rolling, rolling according to 9 + 3 passes; for finish rolling, use 2 stands of single-pass rolling; the starting rolling temperature is 1070 - 1120 °C, and finish rolling is carried out at a low temperature of 790 - 800 °C; for the rolling pass of the four stands, the 1st - 3rd passes are reciprocating rolling box passes, referring to Appendix Figure 2 ; the 4th - 6th passes are split passes, referring to Appendix Figure 3 ; the 7th - 12th passes are extension rough rolling preforming passes, referring to Appendix Figure 4 ; the 13th pass is the finish rolling preforming pass, referring to Appendix Figure 5 ; the 14th pass is the finished product pass, referring to Appendix Figure 6 ; all the above pass shapes are alternately configured with upper closed passes and lower closed passes, that is, the geometric shapes on both sides of the rolled piece are alternately processed by the pass, and the abnormal spread of the metal in the pass is restricted by the closed pass; (5) Cooling process: After rolling, perform pre-bending of 300 mm at the entrance of the walking beam cooling bed and then cool. Install a blower at the lower end of the cooling bed to cool evenly from bottom to top to room temperature; (6) Straightening process: Use a 9-roll straightening machine for straightening; (7) Sawing to fixed length process: Use a laser fixed-length cold saw to cut the rail tie to a fixed length, and after passing the inspection, store it in the warehouse.

Claims

1. A production method for a weather-resistant railway tie steel four-stand rolling mill, characterized in that: Weather-resistant steel for railway tie plates, the chemical composition and mass percentage content are as follows: C: 0.15 - 0.22%, Mn: 0.30 - 0.50%, Cr: 0.50 - 0.60%, Si: 0.25 - 0.35%, Cu: 0.25 - 0.35%, Ni: 0.30 - 0.40%, P: 0.008 - 0.025%, S ≤ 0.020%, and the balance is Fe and unavoidable impurities. Its production method includes converter smelting, continuous casting, heating, rolling, cooling, straightening, sawing to fixed length, and warehousing processes, where: (1) Converter smelting process: Control the basicity R value of the converter final slag to be not less than 3.0; (2) Continuous casting process: The tundish temperature is controlled at 1535 - 1545°C, and the continuous casting billet casting speed is 0.7 - 0.8 m / min; (3) Heating process: The preheating section temperature ≤ 920°C, the heating section temperature is 1150 - 1200°C, and the soaking section temperature is 1200 - 1280°C; (4) Rolling process: Use a four-stand rolling mill for rolling. The rough rolling uses two stands for reciprocating rolling, and the finish rolling uses two stands for single-pass rolling. The starting rolling temperature is 1070 - 1120°C, and the finish rolling temperature is 790 - 800°C.

2. The production method of a weather-resistant railway tie steel four-stand rolling mill according to claim 1, characterized in that: In the said converter smelting process: Copper and nickel are added to the converter for melting together with scrap steel in the form of metal plates.

3. A production method of a weather-resistant railway tie steel four-stand rolling mill according to claim 1, characterized in that: In the said heating process: The temperature of the continuous casting billet entering the heating furnace ≤ 80°C.

4. A production method of a weather-resistant railway tie steel four-stand rolling mill according to claim 3, characterized in that: In the said heating process: The heating time of the continuous casting billet is 2.5 - 3 h.

5. A production method of a weather-resistant railway tie section steel four-stand rolling mill according to claim 1: The rolling process: The number of rolling passes for continuous casting billets is 14 passes, among which, The rough rolling is 12 passes, and the finish rolling is 2 passes.

6. A production method of a four-stand rolling mill for weather-resistant steel for railway tie plates according to claim 5: In the said rolling process: The 1st - 3rd passes are reciprocating rolling box pass, the 4th - 6th passes are split passes, the 7th - 12th passes are extension rough rolling preforming passes, the 13th pass is the finish rolling preforming pass, and the 14th pass is the finished product pass.

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