High manganese steel for railway frog and method for producing the same

Abstract

The application discloses a high manganese steel for railway frog and a production method thereof, and belongs to the field of high alloy steel. The chemical components of the high manganese steel are C, Si, Mn, Cr, Mo, Ni, Nb, V, Ti, P and S, and the balance is Fe and a small amount of inevitable impurities. The preparation steps include a smelting process and a rolling process. The smelting process includes electric furnace smelting, LF refining, VD treatment, continuous casting and slow cooling process of the cast blank. The rolling process includes heating, rolling, online rapid cooling process and subsequent processes. The application adopts low-P, low-S and micro-alloying design in the composition, strictly controls the contents of O, N and H in the steel during the smelting process, reduces the precipitation of oxides, sulfides, phosphides and carbides in the steel, and improves the fatigue resistance of the high manganese steel. The process route can reduce defects, refine grains, reduce the precipitation of carbides, improve the comprehensive mechanical properties of the high manganese steel, and greatly prolong the service life of the high manganese steel.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of high alloy steel, and relates to a high manganese steel for railway frog and a production method thereof. BACKGROUND

[0002] With the development of high-speed and heavy-load railways in China, the railway transportation system presents the characteristics of high operation speed, large transportation capacity and high frequency of traffic, but due to the short operation time and high requirements of maintenance and repair, higher requirements are also put forward for the structure and material of railway turnout. The frog, as the core component of the turnout, plays an important role in the railway. The traditional high manganese steel structural material has high strength and toughness and excellent work hardening capacity, and can be applied to various severe and complex environments, and is widely used in railways at home and abroad. However, with the requirements of high-speed and heavy-load conditions, more stringent requirements are put forward for the service life and structure of the railway frog. Chinese patent CN 113462991 A discloses a forging or rolling process of an alloyed high manganese steel frog, which has the disadvantages of high alloy cost, high upper limit content of P and S elements, and two-stage heating and forging (or rolling) process, which affects the production rhythm and efficiency.

[0003] At present, the railway frog in China mainly adopts cast high manganese steel material, but the cast high manganese steel has defects such as coarse organization, non-dense, and cavity, which can easily cause peeling and chunking in use, greatly reducing the service life. The rolled high manganese steel can roll the defects and refine the grains in the rolling process, greatly improving the service life. It is urgent to further improve the manufacturing technology of railway frog and research new materials with more excellent performance. SUMMARY

[0004] The purpose of the present application is to provide a high manganese steel for railway frog and a production method thereof.

[0005] Technical scheme: The high manganese steel for railway frog provided by the present application comprises the following chemical components in percentage by weight: C: 1.00-1.30%, Si: 0.30-0.80%, Mn: 12.00-14.00%, Cr: ≤5.00%, Mo: ≤2.00%, Ni: ≤1.00%, Nb: ≤0.10%, V: ≤0.20%, Ti: ≤0.10%, P: ≤0.030%, S: ≤0.010%, and the balance of Fe and a small amount of unavoidable impurities.

[0006] Further, the chemical components of the high manganese steel are as follows in percentage by weight: C: 1.17%, Si: 0.48%, Mn: 12.55%, Cr: 0.06%, Mo: 1.37%, Ni: 0.72%, Nb: 0.006%, V: 0.008%, Ti: 0.006%, P: 0.006%, S: 0.003%, and the balance of Fe and a small amount of unavoidable impurities (O: 0.0014, N: 0.0095, H: 0.0002).

[0007] Further, the chemical components of the high manganese steel are as follows in percentage by weight: C: 1.25%, Si: 0.35%, Mn: 13.79%, Cr: 4.02%, Mo: 0.02%, Ni: 0.02%, Nb: 0.020%, V: 0.046%, Ti: 0.005%, P: 0.005%, S: 0.004%, and the balance of Fe and a small amount of unavoidable impurities (O: 0.0012, N: 0.0092, H: 0.0003).

[0008] Further, the chemical components of the high manganese steel are as follows in percentage by weight: C: 1.03%, Si: 0.56%, Mn: 12.64%, Cr: 1.23%, Mo: 0.55%, Ni: 0.01%, Nb: 0.008%, V: 0.006%, Ti: 0.041%, P: 0.005%, S: 0.003%, and the balance of Fe and a small amount of unavoidable impurities (O: 0.0016, N: 0.0098, H: 0.0001).

[0009] Further, the chemical components of the high manganese steel are as follows in percentage by weight: C: 1.15%, Si: 0.54%, Mn: 13.43%, Cr: 0.04%, Mo: 0.06%, Ni: 0.03%, Nb: 0.080%, V: 0.090%, Ti: 0.073%, P: 0.006%, S: 0.003%, and the balance of Fe and a small amount of unavoidable impurities (O: 0.0017, N: 0.0094, H: 0.0002).

[0010] Further, a production method of the high manganese steel for railway frog is provided, and the preparation steps are as follows:

[0011] (1) smelting process;

[0012] I. Electric furnace smelting: adding molten iron, scrap steel and part of alloy raw materials into the electric furnace to obtain molten steel, and performing P removal treatment to control P: ≤0.030%;

[0013] 2. LF Refining: The molten steel smelted in the electric furnace is transferred to the LF furnace for refining and desulfurization treatment. The sulfur content is controlled to be ≤0.010%, and the alloy element content is adjusted to the required range.

[0014] III. VD Treatment: The refined molten steel is subjected to VD vacuum treatment to reduce the content of O, N, and H in the molten steel, and to control O: ≤0.0030%, N content not greater than 0.0200%, and H: ≤0.0004%, while the molten steel is homogenized at the same time.

[0015] IV. Continuous Casting: Molten steel is transferred to a tundish, and then poured into a crystallizer. Under the action of a straightening machine, the solidified billet shell leaves the crystallizer. During the continuous casting process, electromagnetic stirring is activated and light pressure is applied. The straightening machine's pulling speed is 0.3–0.8 m / min.

[0016] V. Slow Cooling of Billet: To prevent surface cracking, the continuously cast high-manganese steel billet is placed in a slow cooling pit to cool to room temperature;

[0017] (2): Rolling process:

[0018] I. Heating: The heating temperature of the high manganese steel billet is 1180~1260℃, the soaking time is ≥2min / cm, and the total time in the furnace is ≥420min;

[0019] II. Rolling: The high manganese steel billet is rolled directly after exiting the furnace, with a compression ratio of not less than 3 and a final rolling temperature of ≥980℃;

[0020] 3. Online rapid cooling: After rolling, the water temperature is directly cooled online. The water temperature is ≥950℃ and the reddening temperature is ≤300℃.

[0021] IV. Subsequent Processes: Subsequent processes include equal cutting and straightening, etc.

[0022] Beneficial Effects: Compared with the prior art, the features of this invention are: 1. The production process of high-manganese steel for turnouts is simple, the process parameters are easy to control, the production cost is low, and it is suitable for mass production; 2. The high-manganese steel for turnouts of this invention adopts a low P, low S and micro-alloying design, and controls the content of H, O and N, thereby reducing the precipitation of phosphides, sulfides, oxides and carbides, reducing the risk of cracking during rolling, and improving the fatigue life of high-manganese steel; 3. The continuous casting process adopts a light reduction process, and the rolling process... The reduction ratio is controlled above 3, which reduces internal defects in high manganese steel, refines the grain size of high manganese steel, and improves the comprehensive mechanical properties of high manganese steel; 4. The online rapid cooling process can reduce the precipitation of carbides in high manganese steel, avoid the secondary heating and cooling of offline solid solution, shorten the production process, improve production efficiency, and reduce production costs; 5. This invention uses an electric furnace smelting + LF refining + VD treatment + continuous casting + slow cooling of continuous casting billet + heating + rolling + online solid solution process to obtain austenitic high manganese steel for railway frogs. According to GB / T 13925, its grain size rating is not less than level 3, the non-metallic inclusion rating is not greater than 2A and 2B, the undissolved carbide level is not greater than W2, the precipitated carbide level is not greater than X3, and the overheated carbide level is not greater than G1. The high manganese steel has a yield strength ≥400MPa, tensile strength ≥950MPa, elongation after fracture ≥50%, and room temperature impact KU2 ≥250J; 6. Compared with traditional cast high manganese steel products, the service life of the high manganese steel for turnouts of this invention can be increased by more than 2 times. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the metallographic structure of high manganese steel used for the turnout in an embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to embodiments.

[0025] like Figure 1 As shown, Figure 1 This is a metallographic schematic diagram of the high-manganese steel used for the turnout in this invention. The microstructure is austenitic with fine grains, few precipitated carbides, and no undissolved or overheated carbides were found.

[0026] Specifically, the high-manganese steel for railway frogs described in this invention comprises the following chemical components by weight percentage: C: 1.00–1.30%, Si: 0.30–0.80%, Mn: 12.00–14.00%, Cr: ≤5.00%, Mo: ≤2.00%, Ni: ≤1.00%, Nb: ≤0.10%, V: ≤0.20%, Ti: ≤0.10%, P: ≤0.030%, S: ≤0.010%, with the balance being Fe and a small amount of unavoidable impurities.

[0027] Furthermore, a method for producing high-manganese steel for railway frogs includes the following preparation steps:

[0028] (1): Smelting process;

[0029] I. The chemical composition of the high manganese steel in each embodiment of the present invention is shown in Table 1. The electric furnace smelting, LF refining, VD treatment, continuous casting and billet slow cooling process are carried out according to the composition in Table 1.

[0030] Table 1. Chemical composition (wt%) of high-manganese steel in various embodiments of the present invention.

[0031]

[0032]

[0033] 2. The molten steel is transferred to the tundish, and then the molten steel in the tundish is poured into the crystallizer. Under the action of the straightening machine, the solidified billet shell leaves the crystallizer.

[0034] During the continuous casting process, electromagnetic stirring was activated and light pressure was applied. The casting speeds in Examples 1 to 4 were 0.35, 0.52, 0.71, and 0.64 m / min, respectively.

[0035] (2): Rolling process: including heating, rolling, online rapid cooling and subsequent processes;

[0036] I. The heating processes of various embodiments of the present invention are shown in Table 2;

[0037] Table 2 Heating processes of various embodiments of the present invention

[0038] Examples Soak time / min Total heating time / min Heating temperature / °C 1 88 454 1195 2 115 502 1248 3 106 487 1216 4 97 511 1233

[0039] II. The rolling and cooling processes of each embodiment of the present invention are shown in Table 3.

[0040] Table 3 Rolling processes of various embodiments of the present invention

[0041]

[0042] (3): Performance of various aspects

[0043] I. The metallurgical properties of the high-manganese steel in each embodiment of the present invention are shown in Table 4.

[0044] Table 4. Metallurgical properties of high-manganese steel in various embodiments of the present invention.

[0045]

[0046]

[0047] II. The mechanical properties of the high-manganese steel in each embodiment of the present invention are shown in Table 5.

[0048] Table 5 Mechanical properties of high-manganese steel in various embodiments of the present invention

[0049]

[0050] Currently, railway frogs are mainly made of cast high-manganese steel. However, cast high-manganese steel has defects such as coarse microstructure, lack of density, and voids, which easily lead to spalling and chipping during use, significantly reducing its service life. This invention addresses this issue by using high-manganese steel for railway frogs with a low-P, low-S composition and micro-alloying design. During the smelting process, the O, N, and H contents in the steel are strictly controlled, reducing the precipitation of oxides, sulfides, phosphides, and carbides, thus improving the fatigue resistance of the high-manganese steel. The specific process route is electric furnace smelting + LF refining + VD treatment + continuous casting + slow cooling of the continuously cast billet + heating + rolling + online solution treatment. This process route reduces defects, refines grains, reduces carbide precipitation, and improves the comprehensive mechanical properties of the high-manganese steel, greatly extending its service life. This product has been successfully applied to the Shuohuang Railway, and its service life is more than doubled compared to traditional cast high-manganese steel products.

Claims

1. A high-manganese steel for railway frogs, characterized in that, The chemical composition of the high-manganese steel, by weight percentage, is as follows: C: 1.00–1.30%, Si: 0.30–0.80%, Mn: 12.00–14.00%, Cr: ≤5.00%, Mo: ≤2.00%, Ni: ≤1.00%, Nb: ≤0.10%, V: ≤0.20%, Ti: ≤0.10%, P: ≤0.030%, S: ≤0.010%, with the balance being Fe and a small amount of unavoidable impurities; The preparation steps of its production method are as follows: (1) Smelting process; including electric furnace smelting, LF refining, VD treatment, continuous casting and billet slow cooling process; The specific process of the electric furnace smelting process is as follows: molten iron, scrap steel and some alloy raw materials are added to the electric furnace for smelting to obtain molten steel, and then P removal treatment is carried out to control P: ≤0.030%; The specific process of the LF refining process is as follows: the molten steel smelted in the electric furnace is transferred to the LF furnace for refining and desulfurization treatment, the S content is controlled to be ≤0.010%, and the alloy element content is adjusted to the required range. The specific process of the VD treatment is as follows: the refined molten steel is subjected to VD vacuum treatment to reduce the content of O, N and H in the molten steel, and to control O: ≤0.0030%, N content not greater than 0.0200%, H: ≤0.0004%, while the molten steel is homogenized. The specific process of the continuous casting process is as follows: molten steel is transferred to a tundish, and then the molten steel in the tundish is poured into a crystallizer. Under the action of a straightening machine, the solidified billet shell leaves the crystallizer. During the continuous casting process, electromagnetic stirring is activated and light pressure is applied. The straightening machine's pulling speed is 0.3–0.8 m / min. The specific process of the billet slow cooling process is as follows: In order to prevent surface cracking, the continuously cast high manganese steel billet is placed in a slow cooling pit and cooled to room temperature. (2) Rolling process; including heating, rolling, online rapid cooling process and subsequent processes; The specific process of the heating process is as follows: the heating temperature of the high manganese steel billet is 1180~1260℃, the soaking time is ≥2min / cm, and the total time in the furnace is ≥420min; The specific process of the rolling process is as follows: after the high manganese steel billet is taken out of the furnace, it is rolled with a compression ratio of not less than 3 and a final rolling temperature of ≥980℃. The specific process of the online rapid cooling process is as follows: after rolling, online rapid cooling is performed, with a water inlet temperature ≥950℃ and a reddening temperature ≤300℃; The subsequent processes include equal cutting and straightening.

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