Method for cutting off the riser of a super-thick chromium-molybdenum steel ingot

Abstract

The application discloses a method for cutting a riser of a super-large-thickness chromium-molybdenum steel ingot, and particularly relates to the following steps: adopting a variable-pressure and variable-speed cutting process to cut; the variable-pressure cutting is as follows: during the cutting process, the natural gas pressure is 0.2-0.4 MPa, the initial oxygen pressure is 0.5-0.7 MPa, then the oxygen pressure is gradually increased, when the cutting reaches the center, the oxygen pressure is 1.0-1.2 MPa, then the oxygen pressure is gradually decreased, and when the cutting is finished, the pressure is 0.5-0.7 MPa; the variable-speed cutting is as follows: during the cutting process, the initial cutting speed is 0.7-0.9 m / min, then the cutting speed is gradually decreased, when the cutting reaches the center, the cutting speed is 0.4-0.6 m / min, then the cutting speed is gradually increased, and when the cutting is finished, the cutting speed is 0.7-0.9 m / min. By adopting the method, the cutting surface quality is good, and there are no defects such as cutting blasting and sawtooth, the quality of the edge of the rolled steel plate is good, and defects such as notches and bursting are controlled within 3%.

Description

Technical Field

[0001] The invention belongs to the technical field of iron and steel metallurgy, and in particular relates to a method for cutting a riser of a super-thick chromium-molybdenum steel ingot. Background Art

[0002] Chromium-molybdenum steel plates are commonly used in the manufacture of petrochemical and coal chemical equipment. As these facilities evolve toward larger, more intensive, and more sophisticated production, more and more of them require upgrades, placing increasingly stringent demands on the steel used in these equipment. This demand for thicker and wider plates is coupled with a rolling reduction ratio of ≥3 to ensure internal quality. For these thick plates, conventional continuous casting ingots are no longer sufficient, forcing them to be produced from ingots.

[0003] Due to the high content of chromium-molybdenum alloying elements, direct rolling from ingots can easily lead to surface defects such as cracks, dents, cambers, and warps on the steel plates. These defects can increase the number of subsequent production steps, severely impacting the production schedule. More seriously, they can cause production delays and significant economic losses.

[0004] For chromium-molybdenum steel plates, which are produced from ingots, the risers must be cut off before rolling to ensure smooth furnace loading. The quality of the cutting edge significantly impacts the quality of the steel plate's rolling. Cutting defects such as blasting and sawtooth can result in minor edge shape defects and, in severe cases, directly cause the plate to be out of shape. Furthermore, the thicker the ingot, the more difficult it is to cut. The presence of a certain amount of compositional segregation, porosity, and shrinkage defects at the riser of the ingot increases the risk of defects during the cutting process. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for cutting a riser of a super-thick chromium-molybdenum steel ingot to improve the cutting quality and reduce cutting defects such as blasting and notches.

[0006] A method for cutting a riser opening of a super-thick chromium-molybdenum steel ingot comprises the following steps: cutting is performed using a variable pressure and variable speed cutting process.

[0007] The variable pressure cutting: during the cutting process, the natural gas pressure is 0.2-0.4MPa, the oxygen pressure is initially 0.5-0.7MPa, and then gradually increases. When cutting to the center, the oxygen pressure is 1.0-1.2MPa, and then gradually decreases. When the cutting ends, the pressure is 0.5-0.7MPa.

[0008] The variable speed cutting: during the cutting process, the initial cutting speed is 0.7-0.9 m / min, then gradually decreases, the cutting speed is 0.4-0.6 m / min when cutting to the center, then gradually increases, and the cutting speed is 0.7-0.9 m / min when the cutting is finished.

[0009] Further, the method of the application, wherein, before cutting, the surface of the blank is baked by using a gas cutting machine, during the baking process, the natural gas pressure is 0.1-0.2 MPa, the oxygen pressure is 0.3-0.6 MPa, and the baking speed of the gas cutting machine is 3-5 m / min.

[0010] Further, the method of the application, wherein, during cutting, the cutting line is 50-150 mm away from the riser line.

[0011] Further, the method of the application, wherein, during the cutting process, the nozzle is 30-50 mm away from the steel plate.

[0012] Further, the method of the application, wherein, during the casting of the steel ingot, the molten steel is poured to the position 50-70 mm away from the upper edge of the riser to start adding rice husk, and the total amount of rice husk is 50-100 kg.

[0013] The method for cutting the riser of the blank of the super-large thickness chromium-molybdenum steel ingot, during the cutting process, a variable pressure and variable speed cutting process is used, the cutting speed and the oxygen pressure of the cutting trolley are adjusted in the area where the composition segregation is more serious in the middle of the riser width, the cutting quality is improved under the premise of ensuring the cutting speed; before cutting, the surface of the blank is baked, which can effectively remove the iron oxide scale on the surface of the blank and avoid cutting quality problems caused by surface defects; the cutting line is accurately positioned, and the distance of the nozzle from the steel plate is controlled, which can effectively improve the cutting quality, the amount of rice husk is controlled during the casting process, the heat preservation effect of the riser during the solidification process is strengthened, and the composition segregation is effectively improved.

[0014] The beneficial effects produced by the above technical solutions are: 1) the cutting surface quality is good, there are no cutting blasting, serrations and other defects, the quality of the edge of the rolled steel plate is good, and the probability of defects such as notches and bursting is controlled within 3%; 2) the thickness of the blank cutting can reach 600-700 mm; 3) the above production method only innovates the production process, without increasing equipment investment. Embodiment

[0015] The application will be further described in detail below in combination with specific embodiments. Embodiment 1

[0016] In this embodiment, the chromium-molybdenum steel ingot is blanked, the thickness of the blank is 600 mm, and the composition of the blank is shown in Table 1.

[0017] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 70 mm from the upper edge of the riser, and the total amount of rice husks used was 100 kg.

[0018] The riser cutting method of this embodiment is as follows:

[0019] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.2MPa, the oxygen pressure is 0.6MPa, and the baking speed of the gas cutting machine is 5m / min.

[0020] During the cutting process, the cutting line is 150mm from the riser line, the nozzle is 50mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0021] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.4MPa, and the oxygen pressure is initially 0.7MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.2MPa, and then gradually decreases. When the cutting ends, the pressure is 0.7MPa.

[0022] Variable speed cutting: During the cutting process, the initial cutting speed is 0.9m / min, then gradually decreases, the cutting speed is 0.6m / min when cutting to the center, and then gradually increases, and the cutting speed is 0.9m / min at the end of cutting.

[0023] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 2

[0024] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 700 mm. The billet composition is shown in Table 1.

[0025] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 50 mm from the upper edge of the riser, and the total amount of rice husks used was 50 kg.

[0026] The riser cutting method of this embodiment is as follows:

[0027] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.1MPa, the oxygen pressure is 0.3MPa, and the baking speed of the gas cutting machine is 3m / min.

[0028] During the cutting process, the cutting line is 50mm from the riser line, the nozzle is 30mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0029] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.2MPa, and the oxygen pressure is initially 0.5MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.0MPa, and then gradually decreases. When the cutting ends, the pressure is 0.5MPa.

[0030] Variable speed cutting: During the cutting process, the initial cutting speed is 0.7m / min, then gradually decreases. When cutting to the center, the cutting speed is 0.4m / min, and then gradually increases. When the cutting is completed, the cutting speed is 0.7m / min.

[0031] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 3

[0032] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 670 mm. The billet composition is shown in Table 1.

[0033] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 63 mm from the upper edge of the riser, and the total amount of rice husks used was 65 kg.

[0034] The riser cutting method of this embodiment is as follows:

[0035] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.12MPa, the oxygen pressure is 0.36MPa, and the baking speed of the gas cutting machine is 4m / min.

[0036] During the cutting process, the cutting line is 75mm from the riser line, the nozzle is 42mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0037] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.3MPa, and the oxygen pressure is initially 0.6MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.1MPa, and then gradually decreases. When the cutting ends, the pressure is 0.6MPa.

[0038] Variable speed cutting: During the cutting process, the initial cutting speed is 0.8m / min, then gradually decreases. When cutting to the center, the cutting speed is 0.5m / min, and then gradually increases. When the cutting is completed, the cutting speed is 0.8m / min.

[0039] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 4

[0040] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 620 mm. The billet composition is shown in Table 1.

[0041] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 63 mm from the upper edge of the riser, and the total amount of rice husks used was 89 kg.

[0042] The riser cutting method of this embodiment is as follows:

[0043] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.13 MPa, the oxygen pressure is 0.41 MPa, and the baking speed of the gas cutting machine is 3.9 m / min.

[0044] During the cutting process, the cutting line is 108mm from the riser line, the nozzle is 39mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0045] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.34MPa, and the oxygen pressure is initially 0.51MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.06MPa, and then gradually decreases. When the cutting ends, the pressure is 0.53MPa.

[0046] Variable speed cutting: During the cutting process, the initial cutting speed is 0.76m / min, then gradually decreases. When cutting to the center, the cutting speed is 0.52m / min, and then gradually increases. When the cutting is completed, the cutting speed is 0.76m / min.

[0047] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 5

[0048] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 690 mm. The billet composition is shown in Table 1.

[0049] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 63 mm from the upper edge of the riser, and the total amount of rice husks used was 61 kg.

[0050] The riser cutting method of this embodiment is as follows:

[0051] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.17 MPa, the oxygen pressure is 0.43 MPa, and the baking speed of the gas cutting machine is 3.9 m / min.

[0052] During the cutting process, the cutting line is 95mm from the riser line, the nozzle is 39mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0053] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.29MPa, and the oxygen pressure is initially 0.52MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.14MPa, and then gradually decreases. When the cutting ends, the pressure is 0.63MPa.

[0054] Variable speed cutting: During the cutting process, the initial cutting speed is 0.74m / min, then gradually decreases. When cutting to the center, the cutting speed is 0.53m / min, and then gradually increases. When cutting is finished, the cutting speed is 0.82m / min.

[0055] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 6

[0056] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 618 mm. The billet composition is shown in Table 1.

[0057] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 51 mm from the upper edge of the riser, and the total amount of rice husks used was 63 kg.

[0058] The riser cutting method of this embodiment is as follows:

[0059] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.14 MPa, the oxygen pressure is 0.59 MPa, and the baking speed of the gas cutting machine is 4.6 m / min.

[0060] During the cutting process, the cutting line is 124mm from the riser line, the nozzle is 34mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0061] Variable pressure cutting: during the cutting process, the natural gas pressure is 0.31MPa, and the oxygen pressure is initially 0.62MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.03MPa, and then gradually decreases. When the cutting ends, the pressure is 0.63MPa.

[0062] Variable speed cutting: during the cutting process, the initial cutting speed is 0.74m / min, then gradually decreases, the cutting speed is 0.42m / min when cutting to the center, and then gradually increases, and the cutting speed is 0.76m / min at the end of cutting.

[0063] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 7

[0064] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 659 mm. The billet composition is shown in Table 1.

[0065] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 62 mm from the upper edge of the riser, and the total amount of rice husks used was 63 kg.

[0066] The riser cutting method of this embodiment is as follows:

[0067] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.11 MPa, the oxygen pressure is 0.52 MPa, and the baking speed of the gas cutting machine is 4.9 m / min.

[0068] During the cutting process, the cutting line is 112mm from the riser line, the nozzle is 42mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0069] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.33MPa, and the oxygen pressure is initially 0.62MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.07MPa, and then gradually decreases. When the cutting ends, the pressure is 0.54MPa.

[0070] Variable speed cutting: During the cutting process, the initial cutting speed is 0.84m / min, then gradually decreases. When cutting to the center, the cutting speed is 0.49m / min, and then gradually increases. When cutting is finished, the cutting speed is 0.72m / min.

[0071] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2. Example 8

[0072] In this embodiment, the chromium-molybdenum steel ingot is cut into billets with a thickness of 628 mm. The billet composition is shown in Table 1.

[0073] During the casting process of the steel ingot in this embodiment, rice husks were added when the molten steel reached 62 mm from the upper edge of the riser, and the total amount of rice husks used was 89 kg.

[0074] The riser cutting method of this embodiment is as follows:

[0075] Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.15MPa, the oxygen pressure is 0.46MPa, and the baking speed of the gas cutting machine is 3.4m / min.

[0076] During the cutting process, the cutting line is 124mm from the riser line, the nozzle is 42mm from the steel plate, and the variable pressure and variable speed cutting process is used for cutting. Specifically:

[0077] Variable pressure cutting: During the cutting process, the natural gas pressure is 0.31MPa, and the oxygen pressure is initially 0.66MPa, then gradually increases. When cutting to the center, the oxygen pressure is 1.14MPa, and then gradually decreases. When the cutting ends, the pressure is 0.53MPa.

[0078] Variable speed cutting: During the cutting process, the initial cutting speed is 0.71m / min, then gradually decreases. When cutting to the center, the cutting speed is 0.55m / min, and then gradually increases. When cutting is finished, the cutting speed is 0.81m / min.

[0079] The cutting quality of the blank and the quality of the steel plate in this embodiment are shown in Table 2.

[0080] Table 1 Composition of blanks in various examples (wt %)

[0081]

[0082] Table 2 Cutting quality of blanks and steel plates in various examples

[0083]

[0084] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for cutting a riser for a super-thick chromium-molybdenum steel ingot, characterized in that: Cutting is done using variable pressure and variable speed cutting technology; The variable pressure cutting: during the cutting process, the natural gas pressure is 0.2-0.4 MPa, the oxygen pressure is initially 0.5-0.7 MPa, and then gradually increases. When cutting to the center, the oxygen pressure is 1.0-1.2 MPa, and then gradually decreases. When the cutting is completed, the pressure is 0.5-0.7 MPa. The variable speed cutting: during the cutting process, the initial cutting speed is 0.7-0.9 m / min, then gradually decreases, the cutting speed is 0.4-0.6 m / min when cutting to the center, and then gradually increases, and the cutting speed is 0.7-0.9 m / min at the end of cutting; Before cutting, the surface of the blank is baked with a gas cutting machine. During the baking process, the natural gas pressure is 0.1-0.2MPa, the oxygen pressure is 0.3-0.6MPa, and the baking speed of the gas cutting machine is 3-5m / min. When cutting, the cutting line should be 50-150mm from the riser line; During the cutting process, the nozzle is 30-50mm away from the steel plate; During the ingot casting process, rice husks are added when the molten steel reaches 50-70 mm from the upper edge of the riser, with a total amount of 50-100 kg of rice husks. The thickness of the blank is 600-700 mm.

2. The method for cutting a riser for a super-thick chromium-molybdenum steel ingot according to claim 1, characterized in that: The blank composition is C 0.13-0.15%, Si 0.23-0.35%, Mn 0.45-0.60%, Cr 0.90-1.05%, and Mo 0.48-0.55%.

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