A steel tube for a cannonball and a method of manufacturing the same

Abstract

The present application relates to a kind of steel pipes for cannonball and its preparation method, with mass percentage, the steel pipes for cannonball include: C 0.29-0.31wt%, Si 0.23-0.27wt%, Mn 1.33-1.37wt%, Ti 0.01-0.02wt%, Al 0.005-0.015wt%, the balance is Fe and inevitable impurities.The present application is by optimizing the C, Si, Mn content in chemical composition, and a certain amount of Ti element is added in steel body, the grain structure in steel is refined, the mechanical properties of steel pipe for cannonball are significantly stabilized, can satisfy as the high performance requirement of steel pipe for cannonball.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a steel pipe for artillery shells and its preparation method. Background Technology

[0002] Steel pipes for artillery shells are crucial components in military products, forming a major part of various artillery systems. They are widely used in tanks, mortars, howitzers, and other self-propelled anti-aircraft guns, operating in harsh environments. These steel pipes must withstand the impact of the primer ignition during shell firing to ensure the stable operation of the artillery system, requiring a long service life. Therefore, stringent requirements are placed on the raw materials used in their manufacture.

[0003] CN 115369332A discloses a martensitic aging ultra-high strength steel and its preparation method. The raw materials for preparing this martensitic aging ultra-high strength steel include the following components in parts by weight: C≤0.005%, Mn≤0.05%, Si≤0.05%, S≤0.002%, P≤0.005%, Ni 18.5-19.5%, Co 9.5-10.0%, Mo 5.0-6.0%, Ti 0.7-0.90%, Al≤0.20%, H≤0.00005%, O≤0.0010%, N≤0.0010%, with the balance being Fe and other unavoidable impurities. By adjusting the chemical composition and reducing the content of residual elements, the ultra-high strength steel exhibits a greater martensitic structure at room temperature, thereby improving the steel's strength, plasticity, and toughness.

[0004] CN 113025914A discloses a high-performance online quenched high-strength steel pipe and its production method. The chemical composition of the high-performance online quenched high-strength steel pipe includes, by mass fraction: C: 0.1-0.3%, Si: 0.1-0.8%, Mn: 0.4-2.0%, P: 0.001-0.015%, S: 0.001-0.015%, Al: 0.001-0.05%, Ti: 0.005-0.05%, O: 0.001-0.01%, N: 0.003-0.012%, B: 0.0005-0.005%, Ca+Mg: 0.001-0.01%, and B+Ca+Mg: 0.002-0.012%, with the balance being Fe and unavoidable impurities.

[0005] CN 115838904A discloses a method for manufacturing a high-strength, high-toughness seamless steel pipe with a strength of 850 MPa. The chemical composition of the steel, by weight percentage, is C = 0.18%–0.23%, Si = 0.20%–0.35%, Mn = 1.55%–1.75%, Ni ≤ 0.25%, Cr = 0.10%–0.30%, Mo ≤ 0.05%, Nb = 0.02%–0.035%, V ≤ 0.03%, Ti = 0.01%–0.035%, Al = 0.010%–0.05%, B = 0.001%–0.003%, P ≤ 0.015%, S ≤ 0.005%, N ≤ 0.010%, CEV ≤ 0.55%, with the remainder being Fe and unavoidable impurities. The process steps include: passing the raw materials sequentially through electric furnace smelting, ladle refining, vacuum degassing in a VD furnace or RH furnace, and continuous casting to obtain billets; wherein electromagnetic stirring is carried out during the continuous casting process; the billets are rolled to obtain hot-rolled steel pipes, and the rolling process is carried out in a pipe rolling mill; the hot-rolled steel pipes are then heat-treated.

[0006] The steel bodies provided in the above inventions all have high tensile strength and yield strength, but poor plasticity, and are prone to cracking when used as steel pipes for artillery shells.

[0007] To address the shortcomings of existing technologies, there is a need to provide a steel pipe for artillery shells that has high tensile strength and yield strength, good plasticity, and fine grains. Summary of the Invention

[0008] The purpose of this invention is to provide a steel pipe for artillery shells and its preparation method. By designing the content of C, Si, and Mn in the chemical composition of the steel body and introducing an appropriate amount of Ti element, the grain structure in the steel body is effectively refined, and the mechanical properties of the steel pipe for artillery shells are further stabilized.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a steel pipe for artillery shells, wherein, by weight percentage, the steel pipe for artillery shells comprises: C 0.29-0.31wt%, Si 0.23-0.27wt%, Mn 1.33-1.37wt%, Ti 0.01-0.02wt%, Al 0.005-0.015wt%, with the balance being Fe and unavoidable impurities.

[0011] This invention optimizes the C, Si, and Mn content in the steel pipe for artillery shells and adds a certain amount of Ti element to the steel body, thereby controlling the compositional segregation of the billet, refining the grain structure in the steel, improving the internal structure of the steel pipe, significantly stabilizing the mechanical properties of the steel pipe for artillery shells, and saving energy consumption and production costs.

[0012] The mass percentage of carbon in the steel pipe for the projectile is 0.29-0.31 wt%, for example, it can be 0.29 wt%, 0.295 wt%, 0.3 wt%, 0.305 wt%, or 0.31 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] Carbon (C) is the most economical strengthening element. Controlling the C content within a reasonable range can ensure that the resulting steel pipes for artillery shells have good strength and toughness. Too high or too low C content will have an adverse effect on the properties of the steel.

[0014] The mass percentage of Si in the steel pipe for the projectile is 0.23-0.27 wt%, for example, it can be 0.23 wt%, 0.24 wt%, 0.25 wt%, 0.26 wt% or 0.27 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Si can improve the mechanical properties and cold deformation hardening rate of steel, thereby enhancing the wear resistance of steel. However, excessive Si content will reduce the toughness of steel. Therefore, this invention controls it to 0.23-0.27 wt%.

[0016] The mass percentage of Mn in the steel pipe for the projectile is 1.33-1.37 wt%, for example, it can be 1.33 wt%, 1.34 wt%, 1.35 wt%, 1.36 wt% or 1.37 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] Mn is a low-cost element that is prone to segregation. However, when the finished steel is produced by rolling continuously cast round billets, the segregation and banded structure caused by Mn can be greatly reduced. Therefore, the Mn content in this application can be appropriately increased to enhance the strength of the steel and the deoxidation effect of Si and Al.

[0018] The mass percentage of Ti in the steel pipe for the projectile is 0.01-0.02 wt%, for example, it can be 0.01 wt%, 0.012 wt%, 0.015 wt%, 0.018 wt% or 0.02 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] In this invention, an appropriate amount of Ti element is introduced for microalloying treatment, which can significantly refine the grains. However, if the Ti content is too high, it will form large TiN compounds, which will have an adverse effect on the quality of the steel body and the grain refinement. Therefore, this invention controls its content at 0.01-0.02 wt%.

[0020] The mass percentage of Al in the steel pipe for the projectile is 0.005-0.015 wt%, for example, it can be 0.005 wt%, 0.008 wt%, 0.01 wt%, 0.012 wt% or 0.015 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Al can deoxidize and refine grains, but if the Al content is too high, it is easy to generate inclusions in the steel body. Therefore, the present invention controls its content at 0.005-0.015wt%.

[0022] Preferably, the total mass percentage of Ti+Al in the steel pipe for the projectile is 0.018-0.032wt%, for example, it can be 0.018wt%, 0.02wt%, 0.025wt%, 0.03wt% or 0.032wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] In this invention, the total mass percentage of Ti+Al is limited. Since both Ti and Al have the effect of refining grains, their synergistic effect can further refine the grain structure and significantly improve the mechanical properties of the steel pipe for artillery shells. However, if the total mass percentage of the two exceeds the limit, it will have a negative impact on the overall performance of the steel pipe for artillery shells.

[0024] Preferably, the unavoidable impurities contain: P ≤ 0.02 wt% and S ≤ 0.01 wt%.

[0025] The unavoidable impurities include P ≤ 0.02 wt%, which can be, for example, 0.02 wt%, 0.018 wt%, 0.015 wt%, 0.012 wt%, or 0.01 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] The unavoidable impurities have S ≤ 0.01 wt%, for example, 0.01 wt%, 0.008 wt%, 0.005 wt%, 0.003 wt%, or 0.001 wt%, but are not limited to the listed values. Other unlisted values ​​within the range also apply.

[0027] In a second aspect, the present invention provides a method for preparing a steel pipe for artillery shells as described in the first aspect, the method comprising:

[0028] The molten iron from the blast furnace is smelted in a converter, refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile.

[0029] The preparation method provided by this invention effectively controls the internal structure of the steel pipe for artillery shells through reasonable smelting, continuous casting and rolling process design, improves the mechanical properties of the steel body, enables the finished steel pipe for artillery shells to meet specific performance requirements and ensures its quality stability.

[0030] Preferably, the final temperature of the converter smelting is 1620-1630℃, for example, it can be 1620℃, 1622℃, 1625℃, 1628℃ or 1630℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the white slag holding time of the ladle refining is 20-25 minutes, for example, it can be 20 minutes, 21 minutes, 22 minutes, 23 minutes or 25 minutes, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] Preferably, the superheat of the continuous casting is 25-30°C, for example, it can be 25°C, 26°C, 27°C, 28°C or 30°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the casting speed is 0.75-1 m / min, for example, it can be 0.75 m / min, 0.8 m / min, 0.9 m / min, 0.95 m / min or 1 m / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the initial rolling temperature is 1220-1260℃, for example, it can be 1220℃, 1230℃, 1240℃, 1250℃ or 1260℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the final rolling temperature is 900-950℃, for example, 900℃, 910℃, 920℃, 940℃ or 950℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Controlling the final rolling temperature within a reasonable range can refine the grain structure and improve the properties of the steel.

[0037] As a preferred embodiment of the preparation method described in the second aspect of the present invention, the preparation method includes:

[0038] The molten iron in the formula is smelted in a converter to a final temperature of 1620-1630℃, then refined in a ladle, continuously cast, rolled and finished to obtain the steel pipe for the projectile.

[0039] The white slag holding time for ladle refining is 20-25 min; the superheat of continuous casting is 25-30℃, and the casting speed is 0.75-1 m / min; the initial rolling temperature of rolling is 1220-1260℃, and the final rolling temperature is 900-950℃.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The steel pipe for artillery shells provided by this invention optimizes the content of C, Si, and Mn in the chemical composition and adds a certain amount of Ti element to the steel body, thereby controlling the compositional segregation of the billet, refining the grain structure in the steel, improving the internal structure of the steel pipe, and significantly stabilizing the mechanical properties of the steel pipe for artillery shells. The yield strength can reach 410 MPa, the tensile strength can reach 650 MPa, and the elongation is 22.0-29.0%, which can meet the high-performance requirements of steel pipes for artillery shells. Detailed Implementation

[0042] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0043] Example 1

[0044] This embodiment provides a steel pipe for artillery shells, comprising, by mass percentage: 0.3wt% C, 0.25wt% Si, 1.35wt% Mn, 0.015wt% Ti, 0.01wt% Al, with the balance being Fe and unavoidable impurities; the total mass percentage of Ti+Al in the steel pipe is 0.025wt%; the unavoidable impurities include: 0.015wt% P and 0.005wt% S.

[0045] The method for preparing the steel pipe for the projectile includes:

[0046] The molten iron from the blast furnace is smelted in a converter to a final temperature of 1625℃, then refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile.

[0047] The white slag holding time for ladle refining is 22 min; the superheat of continuous casting is 27℃ and the casting speed is 0.95 m / min; the initial rolling temperature is 1240℃ and the final rolling temperature is 920℃.

[0048] Example 2

[0049] This embodiment provides a steel pipe for artillery shells, comprising, by mass percentage: 0.305wt% C, 0.26wt% Si, 1.36wt% Mn, 0.018wt% Ti, 0.012wt% Al, with the balance being Fe and unavoidable impurities; the total mass percentage of Ti+Al in the steel pipe is 0.03wt%; the unavoidable impurities include: 0.012wt% P and 0.003wt% S.

[0050] The method for preparing the steel pipe for the projectile includes:

[0051] The molten iron from the blast furnace is smelted in a converter to a final temperature of 1628℃, then refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile.

[0052] The white slag holding time for ladle refining is 23 min; the superheat of continuous casting is 28℃ and the casting speed is 0.9 m / min; the initial rolling temperature is 1230℃ and the final rolling temperature is 910℃.

[0053] Example 3

[0054] This embodiment provides a steel pipe for artillery shells, comprising, by mass percentage: 0.295wt% C, 0.24wt% Si, 1.34wt% Mn, 0.012wt% Ti, 0.008wt% Al, with the balance being Fe and unavoidable impurities; the total mass percentage of Ti+Al in the steel pipe is 0.02wt%; the unavoidable impurities include: 0.018wt% P and 0.008wt% S.

[0055] The method for preparing the steel pipe for the projectile includes:

[0056] The molten iron from the blast furnace is smelted in a converter to a final temperature of 1622℃, then refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile.

[0057] The white slag holding time for ladle refining is 21 min; the superheat of continuous casting is 26℃ and the casting speed is 0.8 m / min; the initial rolling temperature is 1250℃ and the final rolling temperature is 930℃.

[0058] Example 4

[0059] This embodiment provides a steel pipe for artillery shells, comprising, by mass percentage: 0.31wt% C, 0.27wt% Si, 1.37wt% Mn, 0.02wt% Ti, 0.015wt% Al, with the balance being Fe and unavoidable impurities; the total mass percentage of Ti+Al in the steel pipe is 0.035wt%; the unavoidable impurities include: 0.01wt% P and 0.001wt% S.

[0060] The method for preparing the steel pipe for the projectile includes:

[0061] The molten iron from the blast furnace is smelted in a converter to a final temperature of 1630℃, then refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile.

[0062] The white slag holding time for ladle refining is 25 min; the superheat of continuous casting is 30℃ and the casting speed is 0.75 m / min; the initial rolling temperature is 1220℃ and the final rolling temperature is 900℃.

[0063] Example 5

[0064] This embodiment provides a steel pipe for artillery shells, comprising, by mass percentage: 0.29wt% C, 0.23wt% Si, 1.33wt% Mn, 0.01wt% Ti, 0.005wt% Al, with the balance being Fe and unavoidable impurities; the total mass percentage of Ti+Al in the steel pipe is 0.015wt%; the unavoidable impurities include: 0.02wt% P and 0.01wt% S.

[0065] The method for preparing the steel pipe for the projectile includes:

[0066] The molten iron from the blast furnace is smelted in a converter to a final temperature of 1620℃, then refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile.

[0067] The white slag holding time for ladle refining is 20 min; the superheat of continuous casting is 25℃ and the casting speed is 1 m / min; the initial rolling temperature of rolling is 1260℃ and the final rolling temperature is 950℃.

[0068] Example 6

[0069] This embodiment provides a steel pipe for artillery shells. The difference between the preparation method of the steel pipe for artillery shells and that of Embodiment 1 is that, except for adjusting the final rolling temperature to 850°C, the rest is the same as that of Embodiment 1.

[0070] Example 7

[0071] This embodiment provides a steel pipe for artillery shells. The difference between the preparation method of the steel pipe for artillery shells and that of Embodiment 1 is that, except for adjusting the final rolling temperature to 980°C, the rest is the same as that of Embodiment 1.

[0072] Comparative Example 1

[0073] This comparative example provides a steel pipe for artillery shells. The difference from Example 1 is that the mass percentage of Ti in the steel pipe for artillery shells is adjusted to 0.005 wt%, the mass percentage of Al is adjusted to 0.002 wt%, and the total mass percentage of Ti+Al is adjusted to 0.007 wt%. All other aspects are the same as in Example 1.

[0074] Comparative Example 2

[0075] This comparative example provides a steel pipe for artillery shells. The difference from Example 1 is that the mass percentage of Ti in the steel pipe for artillery shells is adjusted to 0.025 wt%, the mass percentage of Al is adjusted to 0.02 wt%, and the total mass percentage of Ti+Al is adjusted to 0.045 wt%. All other aspects are the same as in Example 1.

[0076] Comparative Example 3

[0077] This comparative example provides a steel pipe for artillery shells. The difference from Example 1 is that the mass percentage of Mn in the steel pipe for artillery shells is adjusted to 1.3 wt%, while the rest are the same as in Example 1.

[0078] Comparative Example 4

[0079] This comparative example provides a steel pipe for artillery shells. The difference from Example 1 is that the mass percentage of Mn in the steel pipe for artillery shells is adjusted to 1.4 wt%, while the rest are the same as in Example 1.

[0080] The steel pipes for projectiles provided in Examples 1-7 and Comparative Examples 1-4 were tested for mechanical properties according to ASTM A370, and the results are shown in Table 1.

[0081] The steel pipes for artillery shells provided in Examples 1-7 and Comparative Examples 1-4 were evaluated for banded grain size according to GB / T13299 and GB / T6394, and the results are shown in Table 2.

[0082] Table 1

[0083] Tensile strength (MPa) Yield strength (MPa) Elongation (%) Example 1 650 410 29.0 Example 2 633 402 27.5 Example 3 636 398 26 Example 4 640 405 23.0 Example 5 627 394 23.0 Example 6 628 385 21.0 Example 7 590 345 25.0 Comparative Example 1 627 393 22.5 Comparative Example 2 616 372 24.5 Comparative Example 3 625 385 23.5 Comparative Example 4 635 398 25.5

[0084] Table 2

[0085] Strip (level) Grain size (grade) Example 1 1.5 8 Example 2 2.0 7 Example 3 2.0 6 Example 4 2.5 6 Example 5 2.0 6 Example 6 2.5 7 Example 7 2.0 7 Comparative Example 1 2.0 6 Comparative Example 2 2.0 7 Comparative Example 3 2.0 7 Comparative Example 4 2.0 7

[0086] As can be seen from Tables 1 and 2, the steel pipe for artillery shells provided by the present invention refines the grain structure in the steel, improves the internal structure of the steel pipe, significantly stabilizes the mechanical properties of the steel pipe for artillery shells, and can meet the high-performance requirements of the steel pipe for artillery shells.

[0087] A comparison of Example 1 with Examples 6 and 7 shows that excessively high or low final rolling temperatures can cause changes in strength and toughness. A comparison of Example 1 with Comparative Examples 1 and 2 shows that when the Ti and Al contents exceed the specified range and the total Ti+Al content also exceeds the specified range, the strength and toughness of the steel pipe for the projectile will change. A comparison of Example 1 with Comparative Examples 3 and 4 shows that when the Mn content exceeds the specified range, the overall performance of the steel decreases.

[0088] In summary, the shell steel pipe provided by this invention optimizes the C, Si, and Mn content in its chemical composition and adds a certain amount of Ti to the steel body, thereby controlling the compositional segregation of the billet, refining the grain structure in the steel, improving the internal structure of the steel pipe, and significantly stabilizing the mechanical properties of the shell steel pipe. The yield strength can reach 410 MPa, the tensile strength can reach 650 MPa, and the elongation is 22.0-29.0%, which can meet the high-performance requirements of shell steel pipes.

[0089] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A steel pipe for artillery shells, characterized in that, The steel pipe for the projectile, by weight percentage, comprises: C 0.29-0.31wt%, Si 0.23-0.27wt%, Mn 1.33-1.37wt%, Ti 0.01-0.018wt%, Al 0.005-0.008wt%, balance Fe and unavoidable impurities; The steel pipe for the projectile is prepared by the following method, which includes: smelting molten iron in a blast furnace in a formula amount in sequence through a converter, refining in a ladle, continuous casting, rolling and finishing to obtain the steel pipe for the projectile; the final rolling temperature is 900-950℃.

2. The steel pipe for artillery shells according to claim 1, characterized in that, The total mass percentage of Ti+Al in the steel pipe used for the projectile is 0.018-0.026 wt%.

3. The steel pipe for artillery shells according to claim 1, characterized in that, Of the unavoidable impurities: P ≤ 0.02 wt%, S ≤ 0.01 wt%.

4. A method for preparing a steel pipe for artillery shells as described in any one of claims 1-3, characterized in that, The preparation method includes: The molten iron from the blast furnace is smelted in a converter, refined in a ladle, continuously cast, rolled, and finished to obtain the steel pipe for the projectile; the final rolling temperature is 900-950℃.

5. The preparation method according to claim 4, characterized in that, The final temperature of the converter smelting is 1620-1630℃.

6. The preparation method according to claim 4, characterized in that, The white slag from the ladle refining process is held for 20-25 minutes.

7. The preparation method according to claim 4, characterized in that, The superheat of the continuous casting is 25-30℃.

8. The preparation method according to claim 4, characterized in that, The casting speed is 0.75-1 m / min.

9. The preparation method according to claim 4, characterized in that, The initial rolling temperature is 1220-1260℃.

10. The preparation method according to claim 4, characterized in that, The preparation method includes: The molten iron in the formula is smelted in a converter to a final temperature of 1620-1630℃, then refined in a ladle, continuously cast, rolled and finished to obtain the steel pipe for the projectile. The white slag holding time for ladle refining is 20-25 min; the superheat of continuous casting is 25-30℃, and the casting speed is 0.75-1 m / min; the initial rolling temperature of rolling is 1220-1260℃, and the final rolling temperature is 900-950℃.