Cerium-containing austenitic free-cutting steel and method for producing the same

Abstract

The application discloses a cerium-containing austenitic free-cutting steel and a preparation method thereof. The cerium-containing austenitic free-cutting steel contains, in percentage by mass, 0.1-0.4% of C, 1.5-2.0% of Mn, 0.1-0.3% of Si, 6.0-8.0% of Ni, 15.0-17.0% of Cr, 0.1-0.2% of Mo, 0.1-0.5% of S, 0.001-0.3% of Ce, and the rest is Fe and inevitable impurities. The cerium element is reasonably added in the austenitic free-cutting steel, the morphology, size, length-width ratio and distribution of sulfides in the free-cutting stainless steel are effectively controlled and improved, the free-cutting stainless steel has not only good cutting performance, but also very good mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a cerium-containing austenitic free-cutting steel and its preparation method. Background Technology

[0002] Free-cutting steel refers to alloy steel in which one or more free-cutting elements such as sulfur, phosphorus, lead, calcium, selenium, and tellurium are added to improve machinability. Based on the different free-cutting elements contained, free-cutting steel can be classified into sulfur-based free-cutting steel, lead-based free-cutting steel, titanium-based free-cutting steel, and composite free-cutting steel, etc. Sulfur-based free-cutting steel is mainly used in complex components such as bolts, nuts, pipe fittings, automotive brake parts, spring seats, and molds. These complex components require machining on CNC machine tools. To extend tool life, reduce machining costs, and improve production efficiency, the steel must possess good machinability. In sulfur-based free-cutting steel, sulfur mainly exists in the form of manganese sulfide. Manganese sulfide inclusions can act as stress concentration sources, inducing numerous microcracks in the matrix, reducing cutting resistance, and causing the steel to easily break chips during turning.

[0003] Sims and Dahle were the first to classify manganese sulfide in steel castings, dividing it into three categories based on its morphology and distribution: Category I: spherical composite inclusions, randomly distributed, found in steels not deoxidized with aluminum; Category II: short rod-shaped inclusions, distributed in chains or networks along grain boundaries, found in steels deoxidized with a small amount of aluminum; Category III: blocky inclusions, randomly distributed, found in steels with high aluminum content and residual aluminum; later researchers added Category IV: dendritic sulfides. Oikawa et al. studied the influence of alloying elements on the morphology of manganese sulfide in free-cutting steels and classified manganese sulfide as follows: [1] spherical (Category I), formed by segregation reaction; [2] short rod-shaped or dendritic (Category II), formed by eutectic reaction; [3] irregular shape (Category III), generated by pseudoeutectic reaction.

[0004] The size, morphology, and distribution of manganese sulfide in sulfur-containing free-machining steels have a significant impact on the mechanical properties of the steel. To obtain optimal machinability, it is desirable to obtain spherical or spindle-shaped sulfide inclusions with a small aspect ratio during production. Elongated, strip-shaped manganese sulfide inclusions with an aspect ratio exceeding 4:1 not only disrupt the continuity of the matrix but also cause chip adhesion, reducing the surface quality of the workpiece. However, current technologies have failed to effectively control the morphology of sulfides in high-sulfur austenitic free-machining stainless steels. Summary of the Invention

[0005] The main objective of this invention is to provide a cerium-containing austenitic free-cutting steel and its preparation method, so as to solve the problem that the prior art has failed to effectively control the sulfide morphology in high-sulfur austenitic free-cutting stainless steel.

[0006] According to one aspect of the invention, a cerium-containing austenitic free-cutting steel is provided, comprising, by mass percentage: 0.1–0.4% C, 1.5–2.0% Mn, 0.1–0.3% Si, 6.0–8.0% Ni, 15.0–17.0% Cr, 0.1–0.2% Mo, 0.1–0.5% S, 0.001–0.3% Ce, with the remainder being Fe and unavoidable impurities.

[0007] According to one embodiment of the present invention, the proportion of sulfides with an aspect ratio ≤3 in the cerium-containing austenitic free-cutting steel is more than 88%.

[0008] According to one embodiment of the present invention, the cerium-containing austenitic free-cutting steel has a tensile strength ≥500MPa, a yield strength ≥250MPa, a reduction of area ≥15%, an elongation after fracture ≥10%, and an impact toughness ≥15J.

[0009] According to one embodiment of the present invention, the cerium-containing austenitic free-cutting steel contains 0.001 to 0.02% Ce by mass percentage.

[0010] According to one embodiment of the present invention, the cerium-containing austenitic free-cutting steel contains 0.1 to 0.3% S by mass percentage.

[0011] According to another aspect of the present invention, a method for preparing the cerium-containing austenitic free-cutting steel as described above is provided, comprising: sequentially performing batching, smelting, casting, and heat treatment to obtain the cerium-containing austenitic free-cutting steel.

[0012] According to one embodiment of the present invention, a medium-frequency induction furnace is used for melting.

[0013] According to one embodiment of the present invention, the smelting temperature is 1450-1650°C and the tapping temperature is 1550-1650°C.

[0014] According to one embodiment of the present invention, heat treatment includes:

[0015] First, homogenize the material at a temperature of 1200–1250℃ for 3–5 hours.

[0016] Then, a solution treatment is performed at a temperature of 1100–1200℃ for 1–2 hours.

[0017] Finally, an aging treatment is performed at a temperature of 300–600℃ for 1–5 hours.

[0018] According to one embodiment of the present invention, before casting, the method further includes: molding with water glass sand, hardening the sand mold by blowing carbon dioxide, then coating the inner wall of the sand mold with paint, and drying it to obtain a sand mold for casting.

[0019] In the technical solution of this invention, by reasonably adding cerium to austenitic free-cutting steel, the morphology, size, aspect ratio and distribution of sulfides in free-cutting stainless steel can be effectively controlled and improved, so that free-cutting stainless steel not only has good cutting performance, but also very good mechanical properties. Attached Figure Description

[0020] 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.

[0021] Figure 1 The stress-strain curve of the cerium-containing austenitic free-cutting steel of Embodiment 1 of the present invention is shown.

[0022] Figure 2 The stress-strain curve of the cerium-containing austenitic free-cutting steel of Embodiment 2 of the present invention is shown.

[0023] Figure 3 The SEM morphology of sulfides in the cerium-containing austenitic free-cutting steel of Example 1 of the present invention is shown;

[0024] Figure 4 The SEM morphology of sulfides in the cerium-containing austenitic free-cutting steel of Example 2 of the present invention is shown;

[0025] Figure 5 The cutting chips of cerium-containing austenitic free-cutting steel of Embodiment 1 of the present invention are shown at a rotation speed of 180 r / min;

[0026] Figure 6 The cutting chips of the cerium-containing austenitic free-cutting steel of Embodiment 2 of the present invention are shown at a rotation speed of 180 r / min. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0028] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0029] This invention proposes a cerium-containing austenitic free-cutting steel, which, by mass percentage, comprises: 0.1–0.4% C, 1.5–2.0% Mn, 0.1–0.3% Si, 6.0–8.0% Ni, 15.0–17.0% Cr, 0.1–0.2% Mo, 0.1–0.5% S, 0.001–0.3% Ce, with the remainder being Fe and unavoidable impurities.

[0030] In embodiments of the present invention, by rationally adding cerium to austenitic free-cutting steel, the morphology, size, aspect ratio, and distribution of sulfides in free-cutting stainless steel can be effectively controlled and improved, giving the free-cutting stainless steel not only good cutting performance but also excellent mechanical properties. In some embodiments, the proportion of sulfides with an aspect ratio ≤3 in the cerium-containing austenitic free-cutting steel reaches more than 88%. In some embodiments, the cerium-containing austenitic free-cutting steel has a tensile strength ≥500MPa, a yield strength ≥250MPa, a reduction of area ≥15%, an elongation after fracture ≥10%, and an impact toughness ≥15J, exhibiting a good balance between strength and cutting performance.

[0031] The following explains the effects of various alloying elements in this invention on the machinability and mechanical properties of cerium-containing austenitic free-machining steel:

[0032] Carbon (C) is one of the key elements for improving the strength and hardness of austenitic free-machining stainless steel. The carbon content directly affects the steel's strength, plasticity, toughness, and weldability. Controlling the carbon content to 0.1%–0.4% is most beneficial for the machinability and mechanical properties of free-machining stainless steel. When the carbon content in the steel is too low, the ferrite content increases, leading to a decrease in the steel's strength and hardness. Because the steel is too soft and tough, cutting chips easily stick to the tool, reducing its machinability. Conversely, when the carbon content in the steel is too high, its hardness increases, which also causes tool wear and reduces the steel's machinability. Therefore, the carbon content in this invention is controlled within the range of 0.1%–0.4%.

[0033] Mn: Manganese is one of the important elements for improving the machinability of free-machining stainless steel. Manganese readily combines with sulfur to form manganese sulfide, which is the most important free-machining phase in free-machining stainless steel. Excessive manganese content increases the strength and toughness of the steel but reduces its machinability, while insufficient manganese content results in less manganese sulfide formation, which is detrimental to improving machinability. Therefore, in this invention, the Mn content is controlled within the range of 1.5% to 2.0%.

[0034] Silicon (Si) primarily functions as a deoxidizer in free-machining stainless steel, controlling its oxygen content and improving its yield strength and work hardening rate. It also affects sulfide inclusion deformation and machinability. Excessive silicon content can lead to silicate inclusions, causing tool wear and reducing cutting performance. Furthermore, high silicon content can result in the formation of a large amount of oxide scale during hot working, reducing the surface quality of the steel and promoting phosphorus precipitation from the matrix, forming phosphide films at grain boundaries and worsening the steel's hot workability. Therefore, it is necessary to rationally control the silicon content in free-machining stainless steel. In this invention, the Si content is controlled within the range of 0.1% to 0.3%.

[0035] Ni: Nickel is an excellent corrosion-resistant material and an important alloying element for free-cutting steels. Nickel can both improve the strength of steel and maintain its good ductility and toughness. Nickel is an austenite-forming element in steel, enabling the material to achieve a pure austenitic structure. In this invention, the Ni content is controlled within the range of 6.0% to 8.0%.

[0036] Cr: The main role of chromium in steel is to improve its corrosion resistance. Chromium also improves the hardenability of steel, giving it better overall mechanical properties after quenching and tempering. Chromium also increases the strength of steel, especially when other alloying elements are added. However, excessive chromium content in steel increases its hardness, which can negatively impact its machinability. Therefore, in this invention, the Cr content is controlled within the range of 15% to 17%.

[0037] Sulfur (S) is the most abundant free-machining element in free-machining stainless steel. It mainly exists in the steel matrix as sulfides, and the size, content, morphology, and distribution of these sulfides directly affect the steel's machinability. When the sulfur content is below 0.1%, sufficient sulfides cannot be formed in the steel, failing to meet the requirements for high machinability. Conversely, when the sulfur content exceeds 0.5%, its hot workability decreases, and it easily leads to sulfur segregation in the center of the ingot. Therefore, in this invention, the S content is controlled within the range of 0.1% to 0.5%.

[0038] Mo: Molybdenum can refine the grain size of steel, improving hardenability and hot strength. When molybdenum coexists with chromium and manganese, it can reduce or suppress temper brittleness caused by other elements. Therefore, the Mo content in this invention is controlled within the range of 0.1% to 0.2%.

[0039] Ce: Cerium is classified as a lanthanide element. Its main role in free-machining stainless steel is to form oxides with oxygen and rare-earth oxysulfides with sulfur and manganese, improving the distribution and morphology of sulfides and thus enhancing the steel's machinability. Cerium also improves the steel's ductility and toughness, as well as its oxidation and corrosion resistance; its oxidation resistance surpasses that of silicon, aluminum, and titanium. Cerium also improves the fluidity of steel, resulting in a denser and purer microstructure. However, cerium is expensive, and its addition increases production costs; therefore, its content should be minimized while meeting performance requirements. Thus, in this invention, the Ce content is controlled within the range of 0.001% to 0.3%.

[0040] In some embodiments, the cerium-containing austenitic free-cutting steel contains 0.001 to 0.02% Ce by weight.

[0041] In some embodiments, the cerium-containing austenitic free-cutting steel contains 0.1 to 0.3% S by mass percentage.

[0042] The present invention also proposes a method for preparing the cerium-containing austenitic free-cutting steel as described above, comprising: sequentially performing batching, smelting, casting, and heat treatment to obtain the cerium-containing austenitic free-cutting steel.

[0043] In some embodiments, a medium-frequency induction furnace is used for melting. Melting in a medium-frequency induction furnace is highly applicable in actual production, enabling large-scale production. Compared to vacuum furnace smelting, medium-frequency induction furnace melting is simpler to operate, has higher production efficiency, saves energy, and reduces costs.

[0044] In some embodiments, the melting temperature is 1450℃~1650℃ and the tapping temperature is 1550~1650℃.

[0045] In some embodiments, the heat treatment includes: first, homogenization treatment at a temperature of 1200–1250°C for 3–5 hours; then, solution treatment at a temperature of 1100–1200°C for 1–2 hours; and finally, aging treatment at a temperature of 300–600°C for 1–5 hours.

[0046] In some embodiments, before casting, the method further includes: molding with water glass sand, hardening the sand mold by blowing carbon dioxide, then coating the inner wall of the sand mold with paint, and drying it to obtain a sand mold for casting.

[0047] In some embodiments, a method for preparing cerium-containing austenitic free-cutting steel includes the following steps:

[0048] 1) Ingredients: High-purity iron, electrolytic manganese, ferrosilicon, nickel plate, ferrochrome, ferromolybdenum, high-sulfur pig iron, carbon raiser, and rare earth cerium are used as raw materials, and the ingredients are prepared according to the required composition of cerium-containing austenitic free-cutting steel; wherein the carbon raiser can be artificial graphite, natural graphite and / or coke.

[0049] 2) Molding: Water glass sand is used for molding. The sand mold is hardened by blowing carbon dioxide. Then, paint is applied to the inner wall of the sand mold. After drying, it is ready for pouring.

[0050] 3) Melting: The material is melted in a medium-frequency induction furnace at atmospheric pressure of 1450-1650℃ to obtain liquid alloy steel.

[0051] 4) Casting: Increase power and raise the temperature to 1550-1650℃ before tapping the steel; after deoxidation and slag removal, pour the alloy solution into the sand mold and air cool to obtain cast steel;

[0052] 5) Heat treatment: The heat treatment of cast steel is carried out in a muffle furnace. First, homogenization is performed at a temperature of 1200-1250℃ for 3-5 hours, followed by air cooling to room temperature. Then, solution treatment is performed at a temperature of 1100-1200℃ for 1-2 hours, followed by air cooling to room temperature. Finally, aging treatment is performed at a temperature of 300-600℃ for 1-5 hours, followed by air cooling to room temperature, resulting in cerium-containing austenitic free-machining steel ingots.

[0053] In other cerium-containing austenitic free-cutting steels produced using the above method, the proportion of sulfides with an aspect ratio ≤3 reaches over 88%, giving them excellent machinability. Furthermore, they exhibit tensile strength ≥500MPa, yield strength ≥250MPa, reduction of area ≥15%, elongation after fracture ≥10%, and impact toughness ≥15J, demonstrating good mechanical properties. Moreover, the heat treatment process of this invention is simple, and the raw materials are widely available, which helps reduce the production cost of cerium-containing austenitic free-cutting steels.

[0054] The cerium-containing austenitic free-cutting steel prepared by this invention is suitable for manufacturing parts for industries such as automobiles, high-speed rail, home appliances and office equipment. It can effectively reduce machining costs, improve production efficiency and product competitiveness, has good application prospects, and is conducive to achieving energy conservation and emission reduction.

[0055] The following description is based on specific embodiments.

[0056] Example 1

[0057] The target composition for the design of cerium-containing austenitic free-cutting steel, by mass percentage, is: C: 0.35%, Mn: 1.8%, Si: 0.15%, Ni: 7.8%, Cr: 16.2%, Mo: 0.2%, S: 0.17%, Ce: 0.005%, with the remainder being Fe and unavoidable impurities.

[0058] Step 1: Ingredients

[0059] The raw materials are high-purity iron, electrolytic manganese, ferrosilicon, nickel plate, ferrochrome, ferromolybdenum, high-sulfur pig iron, carbon raiser, and rare earth cerium. The raw materials are formulated according to the required composition of cerium-containing austenitic free-cutting steel. The composition of the raw materials is shown in Table 1.

[0060] Table 1: Raw material composition (wt%) for Example 1

[0061] Mn Si Ni C S Mo Cr Ce La High-purity iron 0.04 0.012 0 0.003 0.005 0 0 0 0 Electrolytic manganese 99.58 0.015 0 0 0.100 0 0 0 0 Ferrosilicon 0 72.10 0 0.100 0.016 0 0 0 0 Nickel plate 0 0 99.98 0 0 0 0 0 0 Carbon raiser 0 0 0 97.50 0 0 0 0 0 Ferrochrome 0 1.32 0 0.06 0.03 0 58.2 0 0 Ferromolybdenum 0 0.07 0 0.05 0 58.73 0 0 0 Rare earth cerium 0 0 0 0 0 0 0 63.5 33.5 High-sulfur pig iron 0.2 0.5 0 0.12 26 0 0 0 0

[0062] Step Two: Styling

[0063] In this embodiment, water glass sand is used for molding, and the sand mold mix ratio is shown in Table 2. Before molding, the sand is first dry-mixed and then wet-mixed. During the sand mixing process, the amount of water glass added is carefully controlled to ensure the strength of the sand mold and prevent unnecessary waste. Then it is used for molding. After the mold is formed, several evenly spaced air holes are punched in the mold, and the sand mold is hardened by blowing carbon dioxide. After the sand mold is completely hardened, the mold is removed, and finally, refractory material is applied, awaiting casting.

[0064] Table 2: Sand mold proportions in Example 1

[0065]

[0066]

[0067] Step 3: Smelting

[0068] First, the required high-purity iron is added to the medium-frequency induction furnace. Then, the furnace's safety is checked, and power is supplied to begin the smelting stage. Once the high-purity iron is completely melted into a liquid state, alloying materials (pre-weighed electrolytic manganese, ferrosilicon, nickel plates, ferrochrome, ferromolybdenum, high-sulfur pig iron, carbon raiser, and rare earth cerium) are added to enter the alloying stage. After the alloy is completely melted into a liquid state, the refining stage begins, with a melting time of 20 minutes. The alloy composition is analyzed, and adjustments are made to the amount of alloying materials added.

[0069] Step 4: Pouring

[0070] Once the target composition is achieved, the power is increased to raise the temperature to 1580℃ before tapping the steel; the alloy solution is poured into a sand mold and then air-cooled to obtain the casting;

[0071] Step 5: Heat Treatment

[0072] The heat treatment of the casting is carried out in a muffle furnace. First, homogenization is performed at 1200℃ for 5 hours and then air-cooled to room temperature. Then, solution treatment is performed at 1150℃ for 2 hours and then air-cooled to room temperature. Finally, aging treatment is performed at 550℃ for 3 hours and then air-cooled to room temperature to obtain a cerium-containing austenitic free-cutting steel ingot.

[0073] Example 2

[0074] Cerium-containing austenitic free-cutting steel was prepared using a method similar to that in Example 1, except that:

[0075] The target composition of the cerium-containing austenitic free-cutting steel in Example 2, by mass percentage, was: C: 0.32%, Mn: 1.8%, Si: 0.25%, Ni: 7.8%, Cr: 16%, Mo: 0.2%, S: 0.2%, Ce: 0.008%, with the remainder being Fe and unavoidable impurities. The homogenization temperature of the casting was 1230°C, the solution temperature was 1100°C, the aging temperature was 600°C, and the aging time was 2.5 hours.

[0076] The actual composition of the cerium-containing austenitic free-cutting steels prepared in Examples 1 and 2 is shown in Table 3.

[0077] Table 3: Actual composition (wt%) of the cerium-containing austenitic free-cutting steels prepared in Examples 1 and 2

[0078]

[0079]

[0080] The free-cutting steel was prepared according to the national standard GB / T228.1-2010, and tensile test bars with a diameter of 5 mm were made. The mechanical properties of the specimens were determined by a universal tensile testing machine. Room temperature tensile and Charpy impact tests were conducted using an MTS Landmark 370 electro-hydraulic servo universal testing machine and an MTS falling weight impact testing machine to determine the mechanical properties of the samples. The mechanical properties of the cerium-containing austenitic free-cutting steels of Examples 1 and 2 are shown in Table 4.

[0081] Table 4: Mechanical properties of cerium-containing austenitic free-cutting steels from Examples 1 and 2

[0082]

[0083] Figure 1 The stress-strain curve of the cerium-containing austenitic free-machining steel obtained in Example 1 is shown below. Figure 2 The stress-strain curves for the cerium-containing austenitic free-machining steel obtained in Example 2 are shown in Table 4. Figure 1 and Figure 2It can be seen that the tensile strength of Examples 1 and 2 is ≥500MPa, the yield strength is ≥250MPa, the reduction of area is ≥15%, and the elongation after fracture is ≥10%, which shows that they have good mechanical properties.

[0084] Referring to GB / T 30834-2022, "Evaluation and Statistical Scanning Electron Microscopy of Non-metallic Inclusions in Steel," Phenom Partical X-ray scanning electron microscopy was used to statistically analyze manganese sulfide in the cerium-containing austenitic free-cutting steels of Examples 1 and 2. The statistical analysis area for each sample was 8.0 mm². 2 Table 5 shows the aspect ratio statistics of manganese sulfide in the cerium-containing austenitic free-cutting steels of Examples 1 and 2. As shown in Table 5, the proportion of manganese sulfide with an aspect ratio ≤3 in both Examples 1 and 2 is greater than 88%.

[0085] Table 5: Statistical analysis of the aspect ratio of manganese sulfide in cerium-containing austenitic free-cutting steels of Examples 1 and 2

[0086]

[0087]

[0088] Figure 3 The image shows the SEM morphology of the sulfides in the cerium-containing austenitic free-machining steel of Example 1. Figure 4 The SEM morphology of the sulfides in the cerium-containing austenitic free-machining steel of Example 2 is shown below. Figure 3 and Figure 4 It can be seen that the sulfide inclusions in cerium-containing austenitic free-cutting steel are mostly spherical or short rod-shaped, distributed in a chain or network pattern, and are small and relatively uniformly distributed. The morphology and size of the sulfides help to improve the machinability of the material.

[0089] Figure 5 The cutting chips of the cerium-containing austenitic free-cutting steel in Example 1 at a speed of 180 r / min are shown. Figure 6 The cutting chips of the cerium-containing austenitic free-cutting steel in Example 2 at a rotation speed of 180 r / min are from... Figure 5 and Figure 6 It can be seen that the cerium-containing austenitic free-cutting steels of Examples 1 and 2 exhibit good chip breaking during the cutting process and have good cutting performance.

[0090] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A cerium-containing austenitic free-cutting steel, characterized in that, By mass percentage, it contains: 0.32–0.4% C, 1.5–2.0% Mn, 0.1–0.3% Si, 7.82–8.0% Ni, 15.0–17.0% Cr, 0.1–0.2% Mo, 0.1–0.5% S, 0.001–0.02% Ce, with the remainder being Fe and unavoidable impurities; The proportion of sulfides with an aspect ratio ≤3 in the cerium-containing austenitic free-cutting steel is over 88%. The cerium-containing austenitic free-cutting steel has a tensile strength ≥500MPa, a yield strength ≥250MPa, a reduction of area ≥15%, an elongation after fracture ≥10%, and an impact toughness ≥15J.

2. The cerium-containing austenitic free-cutting steel according to claim 1, characterized in that, The cerium-containing austenitic free-cutting steel contains 0.001 to 0.0082% Ce by mass percentage.

3. The cerium-containing austenitic free-cutting steel according to claim 1, characterized in that, The cerium-containing austenitic free-cutting steel contains 0.1 to 0.3% S by mass percentage.

4. A method for preparing cerium-containing austenitic free-cutting steel as described in any one of claims 1-3, characterized in that, include: The process involves batching, smelting, casting, and heat treatment in sequence to obtain the cerium-containing austenitic free-cutting steel.

5. The method according to claim 4, characterized in that, A medium-frequency induction furnace is used for smelting.

6. The method according to claim 4, characterized in that, The smelting temperature is 1450~1650℃, and the tapping temperature is 1550~1650℃.

7. The method according to claim 4, characterized in that, Heat treatment includes: First, homogenize the material at a temperature of 1200–1250℃ for 3–5 hours. Then, a solution treatment is performed at a temperature of 1100–1200℃ for 1–2 hours. Finally, an aging treatment is performed at a temperature of 300–600℃ for 1–5 hours.

8. The method according to claim 4, characterized in that, Before casting, the method further includes: molding with water glass sand, hardening the sand mold by blowing carbon dioxide, then coating the inner wall of the sand mold with paint, and drying it to obtain a sand mold for casting.

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