Heat-treatment-free alloy cutter head casting production process

Abstract

The invention provides a heat treatment-free alloy cutterhead casting production process, which belongs to the technical field of alloys, and comprises the following steps: S1, alloy smelting: adopting vacuum induction smelting; s2, melt purification is conducted, Ar + 0.5% Cl2 mixed gas is rotationally blown into the melt, dehydrogenation and desulfurization are conducted, and filtering is conducted; s3, directional solidification casting; s4, surface strengthening; a cutting edge martensite and core austenite gradient structure is directly formed through combination of vacuum melting and directional solidification, the component adding proportion of the cutterhead is optimized, the tensile strength and hardness of the cutterhead are increased by 9.4% and 8.6% respectively compared with those of an alloy before optimization, the problems of deformation and cracking caused by traditional quenching are solved, the machining time is shortened, the yield is increased, and the production cost is reduced. High-temperature tempering is replaced with low-temperature strengthening and toughening, the abrasion resistance of the cutting edge is improved, energy consumption is reduced, regenerated stainless steel is combined with electromagnetic separation, the raw material cost is reduced, high-value utilization of regenerated materials is achieved, and cost reduction and carbon reduction synergism is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of alloys, in particular to a production process of alloy cutter head castings free of heat treatment. Background Art

[0002] As a core component of engineering machinery such as shield machines and tunnel boring machines, cutterheads must withstand high stress, impact loads, and complex wear conditions for long periods of time, placing extremely high demands on their mechanical properties, dimensional accuracy, and service life. The production process for traditional alloy cutterhead castings typically includes alloy smelting, casting, heat treatment, and machining. First, wear-resistant alloys such as high-manganese steel and high-chromium cast iron are smelted in a medium-frequency induction furnace or electric arc furnace. The cutterhead blank is then formed through sand casting or precision casting. The casting is then quenched and tempered to refine the grain size, eliminate internal stress, and improve overall performance. Finally, the heat-treated casting undergoes finishing processes such as cutting and drilling.

[0003] However, the heat treatment process is sensitive to parameters such as the quenching medium, heating rate, and holding time, which can easily lead to uneven hardness of the casting, residual stress concentration, and even cracking or deformation, affecting the dimensional accuracy and service stability of the cutter disc. In addition, heat treatment consumes a large amount of energy (such as natural gas and electricity), and the cycle is as long as dozens of hours, which significantly increases production costs. In addition, the waste gas and wastewater generated during the quenching process require additional treatment, which will cause environmental pollution and is not in line with the trend of green manufacturing. In view of the above problems, the present invention proposes a heat-treatment-free alloy cutter disc casting production process, which aims to improve the mechanical properties of the cutter disc, including strength, toughness, wear resistance and comprehensive service performance, while simplifying the production process and reducing energy consumption and costs. Summary of the Invention

[0004] The purpose of the present invention is to solve the above problems in the existing technology and to propose a production process for alloy cutter head castings that does not require heat treatment.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A production process for alloy cutter head castings free of heat treatment, comprising:

[0007] S1. Alloy melting: Mn 10%-15%, Cr 12%-18%, Ni 5%-8%, RE 0.1%-0.3%, Ti 0.05%-0.1%, Nb 0.02%-0.05%, the balance being Fe and unavoidable impurities, by vacuum induction melting (VIM) at 1550-1600°C with a vacuum degree of ≤10-2Pa;

[0008] S2, melt purification, rotating blowing Ar + 0.5% Cl2 mixed gas into the melt, dehydrogenation to [H] ≤ 0.12ml / 100g, desulfurization to [S] ≤ 0.005%, and filtering through 30ppi alumina foam ceramic;

[0009] S3, directional solidification casting, the purified melt is injected into the mold preheated to the gradient temperature, wherein the temperature of the cutting edge area is 500 ° C, and the temperature of the center area is 300 ° C. The mold is filled by low-pressure differential casting with a pressure of 0.4-0.6 MPa. The annular water cooling system is started simultaneously and the cooling rate is controlled at 15-25 K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core;

[0010] S4. Surface strengthening: The casting is shot peened with 0.3 mm steel shot to a coverage rate of 200%, and then baked at 180-200°C for 30 minutes to induce the formation of 10-50 nm carbides on the surface.

[0011] Through vacuum melting + directional solidification (15-25K / s cooling rate), the gradient structure of cutting edge martensite (HV350-400) and core austenite is directly formed, eliminating the quenching process and the risk of deformation and cracking (the traditional quenching deformation is 0.3-0.5mm), which reflects the essence of heat treatment-free. Among them, baking at 180-200℃ replaces high-temperature tempering to induce the formation of 10-50nm (Cr, Mn) on the surface. 23 C6 carbide improves wear resistance and has no temper brittleness; Mn / Ni is used to stabilize austenite to form a core toughness reserve, increasing the elongation of the casting; RE is used to refine the grains, thereby improving fatigue life.

[0012] Preferably, in step S1, the RE is La / Ce mixed rare earth, which is added in the form of RE-Mg alloy wire and is preheated and dehumidified at 200°C for 2h before being added to facilitate the suppression of Mg vapor explosion during the smelting process.

[0013] Preferably, in step S3, the annular water cooling system comprises radially distributed copper pipe water channels, the cooling water flow rate in the area 5 mm away from the cutting edge is 20-25 L / min, and the flow rate in the central area is 8-12 L / min;

[0014] Among them, the cutting edge area has a high flow rate (20-25L / min) and a cooling rate of >22K / s, which is convenient for ensuring the martensitic phase transformation (rapid crossing of the Ms point); the center area has a low flow rate (8-12L / min) and a gentle cooling rate, which avoids thermal stress cracks and helps reduce the scrap rate.

[0015] Preferably, step S4 also includes a PVD coating process, in which a TiAlN / AlCrN multilayer composite coating (single layer thickness 2-3 μm, total thickness 8-10 μm) is deposited on the cutting edge surface, and the deposition temperature is ≤450°C, so as to improve the bonding strength, enhance the anti-peeling property, increase the heat resistance, and adapt to high-speed dry cutting.

[0016] Preferably, in step S1, the raw material contains 30%-50% recycled stainless steel, and Cu / Pb impurities are removed by electromagnetic separation before smelting, so that the Cu / Pb impurities are less than or equal to 0.03%, thereby avoiding grain boundary embrittlement, making the elongation fluctuation less than 5%, and reducing costs and carbon emissions.

[0017] Preferably, in step S3, the porosity of the casting is ≤0.5%, the grain size is ≤20 μm, and the component segregation is ≤±2%.

[0018] Preferably, step S4 further includes modular assembly, machining a dovetail groove on the cutter head substrate, embedding a SiC-p / Al composite blade with a SiC volume fraction of 15%, and achieving metallurgical bonding through laser cladding.

[0019] Preferably, in step S2, the LiMCA technology is used to monitor the melt inclusion content online to be less than or equal to 0.02 mm 2 / kg, and automatically starts secondary purification when it exceeds the standard, which greatly reduces the scrap rate, replaces manual sampling and testing, and improves work efficiency.

[0020] Preferably, the alloy cutter head casting presents a hardness gradient from the cutting edge to the core, and the (Cr, Mn) is distributed within 1mm of the cutting edge. 23 C6 carbide;

[0021] Among them, the surface of the alloy cutter head casting is HV350-400, and the core is HV180-220;

[0022] Among them, the cutter disc base is provided with radial weight-reducing grooves, the groove depth is 30%-40% of the disc thickness, the groove wall is pre-set with diversion protrusions, the protrusion height is 0.5-1mm, and the overall weight reduction is ≥15%.

[0023] Compared with the existing technology, this heat treatment-free alloy cutter head casting production process has the following beneficial effects:

[0024] 1. The present invention provides a production process for alloy cutter disc castings that does not require heat treatment. Through vacuum melting combined with directional solidification, a gradient structure of martensite at the cutting edge and austenite at the core is directly formed, eliminating the quenching process, solving the deformation and cracking problems caused by traditional quenching, increasing the tensile strength of the product, and improving the yield rate.

[0025] 2. The present invention provides a heat treatment-free alloy cutter head casting production process, which uses low temperature toughening instead of high temperature tempering, and bakes at 180-200℃ to induce the precipitation of 10-50nm (Cr, Mn) on the surface. 23 C6 carbide replaces 500-600℃ tempering, improves the mechanical properties of the cutter head, reduces energy consumption, and avoids the risk of sensitization corrosion.

[0026] 3. The present invention provides a heat-treatment-free alloy cutter disc casting production process, which achieves high-value utilization of recycled materials, synergistically reduces costs and carbon emissions, uses 30-50% recycled stainless steel, and combines it with electromagnetic sorting, thereby reducing raw material costs and carbon emissions, breaking through the dilemma of recycled materials being limited to low-end applications.

[0027] 4. The present invention provides a heat treatment-free alloy cutter head casting production process, which adopts full-process digital quality control to achieve "zero defect" manufacturing, and uses LiMCA online monitoring + automatic secondary purification to ensure that the melt inclusions are ≤0.02mm 2 / kg, which reduces the scrap rate, replaces manual inspection, and greatly improves production efficiency.

[0028] 5. The present invention provides a production process for alloy cutter disc castings that does not require heat treatment. The hardness gradient between the cutting edge and the core matches the wear resistance and impact resistance requirements. It is equipped with radial weight-reducing grooves and guide protrusions to improve heat dissipation efficiency, extend the cutting life beyond industry standards, optimize dynamic stiffness, and suppress high-speed cutting vibration.

[0029] In summary, the present invention provides a production process for alloy cutter disc castings that does not require heat treatment. Through vacuum melting combined with directional solidification, a gradient structure of cutting edge martensite and core austenite is directly formed, and the proportion of cutter disc component addition is optimized, so that the tensile strength and hardness of the cutter disc are increased by 9.4% and 8.6% respectively compared with the alloy before optimization. It solves the deformation and cracking problems caused by traditional quenching, reduces processing hours, and improves the yield rate. It also uses low-temperature strengthening instead of high-temperature tempering to improve the wear resistance of the cutting edge and reduce energy consumption. It uses recycled stainless steel combined with electromagnetic sorting to reduce raw material costs, realize high-value utilization of recycled materials, and achieve synergistic cost reduction and carbon reduction. DETAILED DESCRIPTION

[0030] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments. Specific embodiment one:

[0032] A production process for alloy cutter head castings free of heat treatment, comprising:

[0033] S1. Alloy melting: Mn 10%-15%, Cr 12%-18%, Ni 5%-8%, RE 0.1%-0.3%, Ti 0.05%-0.1%, Nb 0.02%-0.05%, the balance being Fe and unavoidable impurities, by vacuum induction melting (VIM) at 1550-1600°C with a vacuum degree of ≤10-2Pa;

[0034] The RE is La / Ce mixed rare earth, added in the form of RE-Mg alloy wire, and is preheated and dehumidified at 200° C. for 2 hours before addition to facilitate suppression of Mg vapor explosion during the smelting process.

[0035] The raw materials contain 30%-50% recycled stainless steel. Before smelting, Cu / Pb impurities are removed by electromagnetic separation, so that the Cu / Pb impurities are less than or equal to 0.03%, thereby avoiding grain boundary embrittlement, making the elongation fluctuation less than 5%, and being able to reduce costs and carbon emissions.

[0036] S2, melt purification, rotating spray Ar + 0.5% Cl2 mixed gas into the melt, dehydrogenation to [H] ≤ 0.12ml / 100g, desulfurization to [S] ≤ 0.005%, and filtered through 30ppi alumina foam ceramics, using LiMCA technology to monitor the melt inclusion content online to be less than or equal to 0.02mm 2 / kg, and automatically starts secondary purification when it exceeds the standard, which greatly reduces the scrap rate, replaces manual sampling and testing, and improves work efficiency.

[0037] S3, directional solidification casting, the purified melt is injected into the mold preheated to the gradient temperature (500 ℃ in the cutting edge area → 300 ℃ in the center area), and the low-pressure differential casting is used to fill the mold with a pressure of 0.4-0.6MPa. The annular water cooling system is started simultaneously, and the cooling rate is controlled to 15-25K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core. The porosity of the casting is ≤0.5%, the grain size is ≤20μm, and the composition segregation is ≤±2%.

[0038] The annular water cooling system includes radially distributed copper pipe water channels. The cooling water flow rate in the area 5 mm away from the cutting edge is 20-25 L / min, and the flow rate in the central area is 8-12 L / min. Among them, the cutting edge area has a high flow rate (20-25 L / min) and a cooling rate of >22 K / s, which is convenient for ensuring martensitic phase transformation (rapid crossing of the Ms point); the central area has a low flow rate (8-12 L / min) and a gentle cooling rate, which avoids thermal stress cracks and helps reduce the scrap rate.

[0039] S4. Surface strengthening: The casting is shot peened (0.3 mm steel shot, 200% coverage), and then baked at 180-200° C. for 30 min to induce the formation of 10-50 nm carbides on the surface.

[0040] Through vacuum melting + directional solidification (15-25K / s cooling rate), the gradient structure of cutting edge martensite (HV350-400) and core austenite is directly formed, eliminating the quenching process and the risk of deformation and cracking (the traditional quenching deformation is 0.3-0.5mm), which reflects the essence of heat treatment-free. Among them, baking at 180-200℃ replaces high-temperature tempering to induce the formation of 10-50nm (Cr, Mn) on the surface. 23 C6 carbide improves wear resistance (HV increased by 15%) and has no temper brittleness (impact energy > 100J); Mn / Ni is used to stabilize austenite to form a core toughness reserve, increasing the elongation of the casting, and RE is used to refine the grains, thereby improving fatigue life.

[0041] It also includes a PVD coating process, which deposits a TiAlN / AlCrN multi-layer composite coating (single layer thickness 2-3μm, total thickness 8-10μm) on the cutting edge surface. The deposition temperature is ≤450℃, which is convenient for improving bonding strength, enhancing anti-peeling properties, increasing heat resistance, and adapting to high-speed dry cutting.

[0042] It also includes modular assembly, machining dovetail grooves in the cutterhead substrate, embedding SiC-p / Al composite inserts with a SiC volume fraction of 15%, and achieving metallurgical bonding through laser cladding.

[0043] Among them, the alloy cutter head casting presents a hardness gradient from the cutting edge to the core (surface HV350-400 → core HV180-220), and the (Cr, Mn) content of 10-50nm is distributed within 1mm of the cutting edge. 23 C6 carbide. In addition, the cutter disc base is provided with radial weight-reducing grooves, the groove depth is 30%-40% of the disc thickness, the groove wall is preset with guide protrusions, the protrusion height is 0.5-1mm, and the overall weight reduction is ≥15%. Specific embodiment two:

[0045] Specific Example 2 is a test on the effect of the Mn content on the tensile strength and elongation of the test alloy mentioned in Specific Example 1, to clarify the optimal addition amount of Mn. The content of Specific Example 2 is as follows:

[0046] The addition amounts of each component are: Mn 10%-15%, Cr 12%, Ni 5%, RE 0.2%, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, and the balance is Fe and unavoidable impurities;

[0047] Specifically, the addition amount of Mn is 11.0%, 13.0%, and 15.0%.

[0048] Vacuum induction melting (VIM) was used to melt at 1550-1600℃, with a vacuum degree of ≤10-2Pa. Ar+0.5% Cl2 mixed gas was blown into the melt in a rotary manner to dehydrogenate to [H]≤0.12ml / 100g and desulfurize to [S]≤0.005%. The melt was then filtered through 30ppi alumina foam ceramics. LiMCA technology was used to monitor the melt inclusion content online to ensure that it was less than or equal to 0.02mm. 2 / kg, and automatically start secondary purification when it exceeds the standard; inject the purified melt into a mold preheated to a gradient temperature (500℃ in the cutting edge area → 300℃ in the center area), adopt low-pressure differential casting to fill the mold, the pressure is 0.4-0.6MPa, and the annular water cooling system is started simultaneously to control the cooling rate to 15-25K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core. The casting is shot peened (0.3mm steel shot, coverage rate 200%) and then baked at 180-200℃ for 30min to induce the formation of 10-50nm carbides on the surface.

[0049] The room temperature tensile test was carried out using an electronic universal testing machine. The specimens were processed into dumbbell-shaped standard tensile specimens (gauge length φ10 mm × 35 mm) according to GB / T228.1 standard. The tensile rate was set to 1.0 mm / min with reference to ASTM E8 standard. The stress-strain curve was collected in real time by an extensometer until the specimen broke.

[0050] As can be seen from the table below, when the Mn content is 11.0%, the austenite stability is insufficient, the Mn / Ni equivalent ratio is low, and 5-8% of δ-ferrite remains in the core, which weakens the strength but improves the plasticity; when the Mn content is increased to 11.0%, the Mn equivalent is approximately equal to 14.2, which completely suppresses the δ-ferrite, increases the proportion of martensite on the cutting edge, and significantly strengthens the nano-carbide dispersion, achieving the best strength-toughness balance; when the Mn content continues to increase to 15.0%, the tensile strength does not increase significantly. The high Mn content promotes deformation twinning, but leads to grain boundary segregation of MnS inclusions, a decrease in elongation, and work hardening dominates.

[0051] When Mn content increases from 11% to 15%, the Mn equivalent increases from 11.7 to 15.9, completely eliminating δ-ferrite and increasing the volume fraction of martensite in the cutting edge from 55% to 75%, thereby improving the tensile strength of the test alloy. Under cooling conditions of 15-25K / s, due to the synergistic effect of the cooling rate, the high Mn (15%) alloy forms lath-bundle refined martensite in the cutting edge, with a dislocation density of 10 15 m -2, the strength is increased by 12% compared to conventional quenching. When the Mn content exceeds 13%, the S impurity tends to form MnS chain inclusions, becoming a crack source, and micropores gather around the MnS. In addition, high Mn content exacerbates dendritic segregation, with the concentration of the Mn-enriched zone in the central area reaching 17.5%. The local elongation difference is greater than 8%. At a Mn content of 15%, a clear yield plateau appears on the true stress-strain curve, and necking occurs prematurely, resulting in a work hardening effect.

[0052] Table 1 Effect of Mn content on tensile strength and elongation of alloy

[0053]

[0054] In summary, the Mn addition amount was determined to be 13%, and subsequent process screening tests were carried out. Specific embodiment three:

[0056] Specific Example 3 is a test on the effect of Cr content on the tensile strength and elongation of the test alloy mentioned in Specific Example 1, to clarify the optimal addition amount of Cr. The content of Specific Example 3 is as follows:

[0057] The addition amounts of each component are: Mn 13%, Cr 12%-18%, Ni 5%, RE 0.2%, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, and the balance is Fe and unavoidable impurities;

[0058] Specifically, the addition amount of Cr is 12.0%, 14.0%, 16.0%, and 18.0%.

[0059] Vacuum induction melting (VIM) was used to melt at 1550-1600℃, with a vacuum degree of ≤10-2Pa. Ar+0.5% Cl2 mixed gas was blown into the melt in a rotary manner to dehydrogenate to [H]≤0.12ml / 100g and desulfurize to [S]≤0.005%. The melt was then filtered through 30ppi alumina foam ceramics. LiMCA technology was used to monitor the melt inclusion content online to ensure that it was less than or equal to 0.02mm. 2 / kg, and automatically start secondary purification when it exceeds the standard; inject the purified melt into a mold preheated to a gradient temperature (500℃ in the cutting edge area → 300℃ in the center area), adopt low-pressure differential casting to fill the mold, the pressure is 0.4-0.6MPa, and the annular water cooling system is started simultaneously to control the cooling rate to 15-25K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core. The casting is shot peened (0.3mm steel shot, coverage rate 200%) and then baked at 180-200℃ for 30min to induce the formation of 10-50nm carbides on the surface.

[0060] The room temperature tensile test was carried out using an electronic universal testing machine. The specimens were processed into dumbbell-shaped standard tensile specimens (gauge length φ10 mm × 35 mm) according to GB / T228.1 standard. The tensile rate was set to 1.0 mm / min with reference to ASTM E8 standard. The stress-strain curve was collected in real time by an extensometer until the specimen broke.

[0061] It can be seen from the table that when the Cr content increases from 12% to 14%, it is the stage of strength increase. Cr dissolves into the austenite matrix, increases the lattice distortion, and increases the resistance to dislocation movement. Specifically, every 1% of Cr contributes about 20-25MPa strength gain; when the Cr content is 14%, (Cr, Mn) 23 C6 nanocarbide has the best dispersion, and due to the activation of shot peening and baking process, the strengthening increment reaches 120-150MPa. When the Cr content increases from 14% to 18%, the strength decreases. This is due to the negative effect of δ-ferrite. When the Cr content is greater than 15%, the chromium equivalent exceeds the critical value of 16.5, resulting in the increase of δ-ferrite ratio from <1% to 8-10%. The soft ferrite reduces the overall strength, offsetting the solid solution strengthening benefits of Cr. In addition, there is also the risk of carbide coarsening. High Cr promotes the formation of grain boundary M 23 C6 carbides grow and become crack sources, reducing the effective load-bearing area. Due to the sudden change in properties between the martensite zone at the cutting edge and the austenite in the core, stress concentrates in the transition zone, leading to edge fracture. When the Cr content exceeds 16%, δ-ferrite and coarse carbides weaken the core, causing fracture to regress to the middle of the gauge length, resulting in specimen failure in the middle.

[0062] Table 2 Effect of Cr content on tensile strength and elongation of alloy

[0063]

[0064] In summary, the Mn addition amount was determined to be 13% and the Cr addition amount was determined to be 14.0%, and subsequent process screening tests were carried out. Specific embodiment four:

[0066] Specific Example 4 is a test on the effect of Ni content on the tensile strength and elongation of the test alloy mentioned in Specific Example 1, to clarify the optimal addition amount of Ni. The content of Specific Example 4 is as follows:

[0067] The addition amounts of each component are: Mn 13%, Cr 14%, Ni 5%-8%, RE 0.2%, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, and the balance is Fe and unavoidable impurities;

[0068] Specifically, the addition amount of Ni is 5.0%, 6.5%, and 8.0%.

[0069] Vacuum induction melting (VIM) was used to melt at 1550-1600℃, with a vacuum degree of ≤10-2Pa. Ar+0.5% Cl2 mixed gas was blown into the melt in a rotary manner to dehydrogenate to [H]≤0.12ml / 100g and desulfurize to [S]≤0.005%. The melt was then filtered through 30ppi alumina foam ceramics. LiMCA technology was used to monitor the melt inclusion content online to ensure that it was less than or equal to 0.02mm. 2 / kg, and automatically start secondary purification when it exceeds the standard; inject the purified melt into a mold preheated to a gradient temperature (500℃ in the cutting edge area → 300℃ in the center area), adopt low-pressure differential casting to fill the mold, the pressure is 0.4-0.6MPa, and the annular water cooling system is started simultaneously to control the cooling rate to 15-25K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core. The casting is shot peened (0.3mm steel shot, coverage rate 200%) and then baked at 180-200℃ for 30min to induce the formation of 10-50nm carbides on the surface.

[0070] The room temperature tensile test was carried out using an electronic universal testing machine. The specimens were processed into dumbbell-shaped standard tensile specimens (gauge length φ10 mm × 35 mm) according to GB / T228.1 standard. The tensile rate was set to 1.0 mm / min with reference to ASTM E8 standard. The stress-strain curve was collected in real time by an extensometer until the specimen broke.

[0071] It can be seen from the table that the tensile strength decreases with the increase of Ni. When the Ni content is 5.0%, the austenite stability is insufficient. At this time, the Ni equivalent is about 10.2. During cooling, the martensite transformation rate in the cutting edge area is as high as 70%, and the peak strength reaches 766MPa. When the Ni content is 8.0%, Ni acts as a strong austenite stabilizer, inhibiting the martensite phase transformation. The proportion of martensite at the cutting edge is reduced to 45%, the solid solution strengthening effect is weakened, and the strength is reduced. In addition, high Ni content may reduce carbon activity, and shot peening-induced (Cr, Mn) 23 The amount of C6 nanocarbide precipitation decreases, and the strengthening increment is lost by about 40MPa. The elongation increases first and then stabilizes with the increase of Ni. When the Ni content increases from 5.0% to 6.5%, the elongation increases from 26.6% to 28.6%. This is because Ni improves the toughness of the austenite phase, reduces δ-ferrite, and delays necking. When the Ni content increases from 6.5% to 8.0%, the elongation increases further, but the increase rate slows down. This may be because the excessive Ni leads to an increase in the stacking fault energy, the deformation mechanism shifts from dislocation slip to twinning, and the uniform elongation is limited.

[0072] Table 3 Effect of Ni content on tensile strength and elongation of alloy

[0073]

[0074] In summary, the Mn addition amount is determined to be 13%, the Cr addition amount is determined to be 14.0%, and the Ni addition amount is determined to be 5.0%. Specific embodiment five:

[0076] Specific embodiment 5 is a test on the critical effect of RE microalloying mentioned in specific embodiment 4, with alloy composition: Mn 13%, Cr 14%, Ni 5, RE 0.2%, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, the balance being Fe and unavoidable impurities, recorded as Group A (RE-0.2%); Mn 13%, Cr 14%, Ni 5, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, the balance being Fe and unavoidable impurities, recorded as Group B (without RE); Mn 13%, Cr 14%, Ni 5, RE 0.4%, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, the balance being Fe and unavoidable impurities, recorded as Group C (RE-0.4%).

[0077] Vacuum induction melting (VIM) was used to melt at 1550-1600℃, with a vacuum degree of ≤10-2Pa. Ar+0.5% Cl2 mixed gas was blown into the melt in a rotary manner to dehydrogenate to [H]≤0.12ml / 100g and desulfurize to [S]≤0.005%. The melt was then filtered through 30ppi alumina foam ceramics. LiMCA technology was used to monitor the melt inclusion content online to ensure that it was less than or equal to 0.02mm. 2 / kg, and automatically start secondary purification when it exceeds the standard; inject the purified melt into a mold preheated to a gradient temperature (500℃ in the cutting edge area → 300℃ in the center area), adopt low-pressure differential casting to fill the mold, the pressure is 0.4-0.6MPa, and the annular water cooling system is started simultaneously to control the cooling rate to 15-25K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core. The casting is shot peened (0.3mm steel shot, coverage rate 200%) and then baked at 180-200℃ for 30min to induce the formation of 10-50nm carbides on the surface.

[0078] Table 4 RE microalloying critical effect

[0079]

[0080] The table above shows that 0.2% RE (Group A) is optimal, reducing the sintering rate by 33% compared to Group B. This reduces grain size to 12 μm, resulting in a tensile strength of 766 MPa, a 4.9% increase compared to Group B, and a -40°C impact energy of 38 J, a 36% increase compared to Group B. When RE is 0.4% (Group C), coarse oxides reduce the impact energy by 13% compared to Group A, but elongation is lost by 8% due to micropore proliferation. In 42% recycled stainless steel, with S ≤ 0.005% and RE = 0.2%, a sulfide nodularization rate of > 90% can be achieved, eliminating the need for additional Ca / Mg treatment and demonstrating compatibility with recycled materials. Specific embodiment six:

[0082] Specific Example 6 is a mechanical property test test of the initial alloy and the optimized alloy mentioned in Specific Examples 1 to 5. The content of Specific Example 6 is as follows:

[0083] Initial alloy composition: Mn 10%, Cr 12%, Ni 5%, RE 0.2%, Ti 0.05%, Nb 0.03%, 42% recycled stainless steel, the balance is Fe and unavoidable impurities;

[0084] The optimized alloy composition is: Mn13%, Cr14%, Ni5%, RE0.2%, Ti0.05%, Nb0.03%, 42% recycled stainless steel, the balance is Fe and unavoidable impurities;

[0085] Vacuum induction melting (VIM) was used to melt at 1550-1600℃, with a vacuum degree of ≤10-2Pa. Ar+0.5% Cl2 mixed gas was blown into the melt in a rotary manner to dehydrogenate to [H]≤0.12ml / 100g and desulfurize to [S]≤0.005%. The melt was then filtered through 30ppi alumina foam ceramics. LiMCA technology was used to monitor the melt inclusion content online to ensure that it was less than or equal to 0.02mm. 2 / kg, and automatically start secondary purification when it exceeds the standard; inject the purified melt into a mold preheated to a gradient temperature (500℃ in the cutting edge area → 300℃ in the center area), adopt low-pressure differential casting to fill the mold, the pressure is 0.4-0.6MPa, and the annular water cooling system is started simultaneously to control the cooling rate to 15-25K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core. The casting is shot peened (0.3mm steel shot, coverage rate 200%) and then baked at 180-200℃ for 30min to induce the formation of 10-50nm carbides on the surface.

[0086] The Vickers hardness of the alloy was measured using a digital microhardness tester with a test load of 1 kg and a dwell time of 15 seconds. The average of eight measurements was taken as the hardness value of the specimen. Tensile testing was performed using an electronic universal testing machine. The tensile specimens were processed into dumbbell-shaped standard tensile specimens (gauge length φ10 mm × 35 mm) according to GB / T228.1. The tensile rate was set at 1.0 mm / min according to ASTM E8. Stress-strain curves were collected in real time using an extensometer until the specimens fractured.

[0087] Based on the above, the mechanical properties of the optimized alloy have been significantly improved, specifically the tensile strength increased to 766MPa, the elongation was 26.6%, and the hardness was increased to HV380. The tensile strength and hardness increased by 9.4% and 8.6% respectively compared with the alloy before optimization.

[0088] Conclusion: From the above results, it can be seen that the optimized alloy composition: Mn13%, Cr14%, Ni5, RE0.2%, Ti0.05%, Nb0.03%, 42% recycled stainless steel, the balance is Fe and unavoidable impurities, has significant advantages in mechanical properties, specifically the tensile strength is increased to 766MPa, the elongation is 26.6%, and the hardness is increased to HV380. The tensile strength and hardness are increased by 9.4% and 8.6% respectively compared with the alloy before optimization.

[0089] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. A production process for alloy cutter head castings that does not require heat treatment, characterized in that: include: S1. Alloy melting: Mn 10%-15%, Cr 12%-18%, Ni 5%-8%, RE 0.1%-0.3%, Ti 0.05%-0.1%, Nb 0.02%-0.05%, the balance being Fe and unavoidable impurities, using vacuum induction melting at 1550-1600°C, with a vacuum degree of ≤10-2Pa; S2, melt purification, rotating blowing Ar + 0.5% Cl2 mixed gas into the melt, dehydrogenation to [H] ≤ 0.12ml / 100g, desulfurization to [S] ≤ 0.005%, and filtering through 30ppi alumina foam ceramic; S3, directional solidification casting, the purified melt is injected into the mold preheated to the gradient temperature, wherein the temperature of the cutting edge area is 500 ° C, and the temperature of the center area is 300 ° C. The mold is filled by low-pressure differential casting with a pressure of 0.4-0.6 MPa. The annular water cooling system is started simultaneously and the cooling rate is controlled at 15-25 K / s to form a gradient structure of fine-grained martensite at the cutting edge and austenite in the core; S4. Surface strengthening: The casting is shot peened with 0.3 mm steel shot to a coverage rate of 200%, and then baked at 180-200°C for 30 minutes to induce the formation of 10-50 nm carbides on the surface.

2. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S1, the RE is La / Ce mixed rare earth, which is added in the form of RE-Mg alloy wire and is preheated and dehumidified at 200°C for 2h before being added.

3. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S3, the annular water cooling system includes radially distributed copper pipe water channels, the cooling water flow rate in the area 5 mm away from the cutting edge is 20-25 L / min, and the flow rate in the central area is 8-12 L / min.

4. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S4, a PVD coating process is also included to deposit a TiAlN / AlCrN multilayer composite coating on the cutting edge surface; The thickness of the single layer is 2-3 μm, the total thickness is 8-10 μm, and the deposition temperature is ≤450°C.

5. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S1, the raw material contains 30%-50% recycled stainless steel, and is subjected to electromagnetic separation to remove Cu / Pb impurities before smelting, and the impurity content is controlled to be less than or equal to 0.03%.

6. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S3 , the casting has a porosity of ≤0.5%, a grain size of ≤20 μm, and a component segregation of ≤±2%.

7. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S4, modular assembly is also included, a dovetail groove is processed on the cutter head substrate, a SiC-p / Al composite blade is embedded, and the SiC volume fraction is 15%, and metallurgical bonding is achieved by laser cladding.

8. The process for producing alloy cutter head castings without heat treatment according to claim 1, characterized in that: In step S2, the LiMCA technology is used to monitor the melt inclusion content online to be less than or equal to 0.02 mm. 2 / kg, and automatically start secondary purification when it exceeds the standard.

9. A process for producing alloy cutter head castings without heat treatment according to any one of claims 1 to 8, characterized in that: The alloy cutter head casting presents a hardness gradient from the cutting edge to the core, and 10-50nm (Cr, Mn) is distributed within 1mm of the cutting edge. 23 C6 carbide; Among them, the surface of the alloy cutter head casting is HV350-400, and the core is HV180-220; Among them, the cutter disc base is provided with radial weight-reducing grooves, the groove depth is 30%-40% of the disc thickness, the groove wall is pre-set with diversion protrusions, the protrusion height is 0.5-1mm, and the overall weight reduction is ≥15%.

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