Low-temperature-resistant cast steel material and preparation method thereof

Abstract

The invention relates to a low-temperature-resistant cast steel material which comprises the following chemical components in percentage by weight: 0.10-0.40% of C; 0.4 to 0.8 percent of Si; mn: 0.7-1.5%; S: less than or equal to 0.2%; p < = 0.2%; cr: 0.05 to 0.35%; 0.1 to 0.5 percent of Ni; 0.05% to 0.25% of Mo; 0.005% to 0.030% of Nb; 0.1-0.5% of Cu, and the balance Fe and inevitable impurity elements; the preparation method comprises the following steps: pouring by adopting an EBT + LF + VD mode, normalizing a casting subjected to rough machining at 900 + / -10 DEG C, preserving heat for a period of time, and then air-cooling to below 200 DEG C; and then tempering treatment is conducted at the temperature of 600 + / -10 DEG C, and furnace cooling is conducted to the room temperature after heat preservation is conducted for a period of time. The strength, ductility and toughness and impact performance of the casting can be improved.

Description

Technical Field

[0001] This invention relates to the field of low-temperature resistant materials, specifically to a low-temperature resistant cast steel material and its preparation method. Background Technology

[0002] With the continuous development of global industry, low-temperature, high-altitude regions, rich in mineral resources such as iron ore, copper ore, and gold ore, have become key areas for development. However, extreme climates place extremely high demands on the performance and reliability of mechanical equipment. Currently, most mining equipment on the market, such as crushers, are designed and manufactured primarily for normal temperature environments, with insufficient consideration given to their adaptability to the special environments of cold, high-altitude regions. In low-temperature environments, the physical and mechanical properties of materials change significantly, leading to problems such as brittle fracture and cracks in key components, which in turn affects the load-bearing capacity and service life of the mechanical equipment.

[0003] While existing technologies have improved the properties of cast steel by adding elements such as molybdenum and vanadium, there is still significant room for improvement in the balance between ultra-low temperature ductility and toughness under harsh conditions involving both ultra-low temperatures (such as below -40°C) and extreme impact loads. The current technological bottleneck lies in how to further unlock the strength potential of materials without sacrificing toughness. Summary of the Invention

[0004] To address the above problems, this invention proposes a low-temperature resistant cast steel material and its preparation method. The cast steel material can maintain stable performance under low-temperature conditions. The specific technical solution is as follows: A low-temperature resistant cast steel material has the following chemical composition by weight percentage: C: 0.10-0.40%; Si: 0.4-0.8%; Mn: 0.7-1.5%; S≤0.2%; P≤0.2%; Cr: 0.05-0.35%; Ni: 0.1-0.5%; Mo: 0.05-0.25%; Nb: 0.005-0.030%; Cu: 0.1-0.5%, with the remainder being Fe and unavoidable impurity elements. Its preparation method includes: casting using EBT+LF+VD, followed by normalizing the rough-machined casting at 900±10℃, holding at that temperature for a period, and then air-cooling to below 200℃; subsequently, tempering at 600±10℃, holding at that temperature for a period, and then furnace-cooling to room temperature.

[0005] Optionally, during preparation, the normalizing treatment is followed by a 4-hour holding time, and the tempering treatment is followed by a 3-hour holding time.

[0006] Optionally, the chemical composition by weight percentage is as follows: C: 0.15-0.24%; Si: 0.5-0.8%; Mn: 1.0-1.2%; S≤0.2%; P≤0.2%; Cr: 0.1-0.3%; Ni: 0.3-0.4%; Mo: 0.10-0.20%; Nb: 0.010-0.030%; Cu: 0.2-0.3%, with the remainder being Fe and unavoidable impurity elements.

[0007] Optionally, the chemical composition by weight percentage is as follows: C: 0.15-0.40%; Si: 0.4-0.8%; Mn: 0.7-1.5%; S≤0.2%; P≤0.2%; Cr: 0.05-0.35%; Ni: 0.1-0.5%; Mo: 0.05-0.25%; Nb: 0.005-0.030%; Cu: 0.1-0.5%, with the remainder being Fe and unavoidable impurity elements.

[0008] Optionally, the chemical composition by weight percentage is as follows: C: 0.17-0.19%; Si: 0.43-0.45%; Mn: 0.8-0.85%; S≤0.01%; P≤0.012%; Cr: 0.21-0.34%; Ni: 0.18-0.19%; Mo: 0.15-0.17%; Nb: 0.01-0.015%; Cu: 0.2-0.35%, with the remainder being Fe and unavoidable impurity elements.

[0009] The beneficial effects of this invention are as follows: 1. Microalloying element nitrogen (Nb) can promote the formation of NbC and Nb(C, N) carbides and carbonitrides during solidification, and simultaneously promote the formation of NbC precipitates during normalizing and tempering. Solid-solution Nb can lower the austenite transformation temperature. The Nb carbides and carbonitrides formed during solidification can act as nuclei for heterogeneous ferrite formation during the austenite transformation, while Nb precipitates can hinder austenite grain coarsening during normalizing. Nb can effectively refine the grain size and microstructure of low-carbon cast steel. Furthermore, microalloying low-carbon cast steel with Nb can simultaneously improve its strength and impact toughness.

[0010] 2. After normalizing and tempering treatment, the comprehensive mechanical properties are excellent. The mechanical properties are: minimum tensile strength 540MPa, minimum yield strength 330MPa, elongation ≥30%, impact value Akv (room temperature) ≥55J, impact value Akv (-20℃) ≥15J, and impact value Akv (-40℃) ≥9J. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 These are microscopic images of the fracture surface of the GS-20Mn5 casting described in the embodiment at different temperatures; Figure 2 These are microscopic images of the fracture surfaces of the low-temperature resistant cast steel castings described in the embodiments at different temperatures; Figure 3 This is a comparison chart of the grain size of the low-temperature resistant cast steel material casting described in the example and the ASTM A27GR70-40 casting. Detailed Implementation

[0013] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0014] The present invention provides the following specific implementation schemes: Example 1: This invention provides a low-temperature resistant cast steel material, the chemical composition of which by weight percentage is: C: 0.17%; Si: 0.43%; Mn: 0.8%; S≤0.01%; P≤0.012%; Cr: 0.21%; Ni: 0.18%; Mo: 0.15%; Nb: 0.01%; Cu: 0.35%, with the remainder being Fe and unavoidable impurity elements.

[0015] The lower frame of the gyratory crusher was prepared using this material. The preparation method included: casting using EBT+LF+VD, and then subjecting the rough-machined casting to normalizing at 900±10℃, holding for 4 hours and then air-cooling to below 200℃; subsequently, tempering was performed at 600±10℃, holding for 3 hours and then furnace-cooled to room temperature.

[0016] Example 2: This invention provides a low-temperature resistant cast steel material, the chemical composition of which by weight percentage is: C: 0.19%; Si: 0.45%; Mn: 0.85%; S≤0.01%; P≤0.012%; Cr: 0.34%; Ni: 0.19%; Mo: 0.17%; Nb: 0.015%; Cu: 0.2%, with the remainder being Fe and unavoidable impurity elements.

[0017] The upper frame of the gyratory crusher was prepared using this material. The preparation method included: casting using EBT+LF+VD, and then subjecting the rough-machined casting to normalizing at 900±10℃, holding for 4 hours and then air-cooling to below 200℃; subsequently, tempering was performed at 600±10℃, holding for 3 hours and then furnace-cooled to room temperature.

[0018] like Figure 1-2 As shown in the figure (a is room temperature, b is -20℃, c is -40℃), the fracture surface of the present invention is more uneven than that of GS-20Mn5 under different temperature conditions, indicating that the present invention has better mechanical properties under low temperature conditions.

[0019] like Figure 3 The grain size shown is that of ASTM A27GR70-40, indicating that the grain size of the present invention is higher than that of ASTM A27GR70-40.

[0020] The strengthening mechanism of the microalloying element nitrogen (Nb) in low-carbon cast steel is mainly through grain refinement and precipitation strengthening, while Nb dissolved in the ferrite matrix can play a solid solution strengthening role. Furthermore, Nb microalloying elements may also have a certain modifying effect on the morphology and size of inclusions. Therefore, Nb can effectively improve the microstructure of cast steel and enhance its mechanical properties. The microalloying element Nb can effectively refine the grain and pearlite particle structure of low-carbon cast steel.

[0021] Microalloying element nitrogen (Nb) can promote the formation of NbC and Nb(C, N) carbides and carbonitrides during solidification, and simultaneously promote the formation of NbC precipitates during normalizing and tempering. Solid-solution Nb can lower the austenite transformation temperature, and the Nb carbides and carbonitrides formed during solidification can act as nuclei for heterogeneous ferrite formation during the austenite transformation, while Nb precipitates can hinder austenite grain coarsening during normalizing. Nb can effectively refine the grain size and microstructure of low-carbon cast steel. Furthermore, microalloying low-carbon cast steel with Nb can simultaneously improve its strength and impact toughness.

[0022] The material in this invention exhibits excellent comprehensive mechanical properties after normalizing and tempering treatment. The mechanical properties are as follows: minimum tensile strength 540MPa, minimum yield strength 330MPa, elongation ≥30%, impact value Akv (room temperature) ≥55J, impact value Akv (-20℃) ≥15J, and impact value Akv (-40℃) ≥9J.

[0023] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A low-temperature resistant cast steel material, characterized in that, Its chemical composition by weight percentage is as follows: C: 0.10-0.40%; Si: 0.4-0.8%; Mn: 0.7-1.5%; S≤0.2%; P≤0.2%; Cr: 0.05-0.35%; Ni: 0.1-0.5%; Mo: 0.05-0.25%; Nb: 0.005-0.030%; Cu: 0.1-0.5%, with the remainder being Fe and unavoidable impurity elements; The preparation method includes: casting using EBT+LF+VD, and then normalizing the rough-machined casting at 900±10℃, holding it at that temperature for a period of time, and then air-cooling it to below 200℃; then tempering it at 600±10℃, holding it at that temperature for a period of time, and then furnace-cooling it to room temperature.

2. The low-temperature resistant cast steel material according to claim 1, characterized in that: During preparation, the normalizing treatment is followed by holding at a constant temperature for 4 hours, and the tempering treatment is followed by holding at a constant temperature for 3 hours.

3. The low-temperature resistant cast steel material according to claim 1, characterized in that, Its chemical composition by weight percentage is as follows: C: 0.15-0.24%; Si: 0.5-0.8%; Mn: 1.0-1.2%; S≤0.2%; P≤0.2%; Cr: 0.1-0.3%; Ni: 0.3-0.4%; Mo: 0.10-0.20%; Nb: 0.010-0.030%; Cu: 0.2-0.3%, with the remainder being Fe and unavoidable impurity elements.

4. The low-temperature resistant cast steel material according to claim 1, characterized in that, Its chemical composition by weight percentage is as follows: C: 0.15-0.40%; Si: 0.4-0.8%; Mn: 0.7-1.5%; S≤0.2%; P≤0.2%; Cr: 0.05-0.35%; Ni: 0.1-0.5%; Mo: 0.05-0.25%; Nb: 0.005-0.030%; Cu: 0.1-0.5%, with the remainder being Fe and unavoidable impurity elements.

5. The low-temperature resistant cast steel material according to claim 1, characterized in that, Its chemical composition by weight percentage is as follows: C: 0.17-0.19%; Si: 0.43-0.45%; Mn: 0.8-0.85%; S≤0.01%; P≤0.012%; Cr: 0.21-0.34%; Ni: 0.18-0.19%; Mo: 0.15-0.17%; Nb: 0.01-0.015%; Cu: 0.2-0.35%, with the remainder being Fe and unavoidable impurity elements.

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