Short-process manufacturing method of 3Cr13 high-carbon martensite chromium stainless steel for cutter

Abstract

The invention provides a short-process manufacturing method of 3Cr13 high-carbon martensite chromium stainless steel for a cutter. The 3Cr13 high-carbon martensite chromium stainless steel for the cutter comprises the following chemical components in percentage by weight: 0.29-0.31 wt% of C, less than or equal to 0.45 wt% of Si, 0.50 wt% of Mn, less than or equal to 0.030 wt% of P, less than or equal to 0.008 wt% of S, less than or equal to 0.006 wt% of N, 12.20-12.50 wt% of Cr, less than or equal to 0.20 wt% of Ni and the balance of Fe. The short-process manufacturing method of the 3Cr13 high-carbon martensite chromium stainless steel for the cutter comprises the following steps: smelting 400-series stainless steel waste serving as raw materials in an alloy melting furnace, tapping with slag, carrying out LF (ladle furnace) refining, continuously casting, carrying out hot delivery, carrying out hot rolling, inspecting, blackening, annealing, pickling and obtaining a white-skin finished product. According to the method, the defects of cracks, scabs and pits on the surface of the casting blank are eliminated, and C-type center segregation is smaller than or equal to 1.0 grade.

Description

Technical Field

[0001] This invention relates to the field of steel production and manufacturing, specifically to a short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. Background Technology

[0002] 3Cr13 is a high-carbon chromium stainless steel, a heat-treated, hardenable stainless steel with a high chromium content. This high chromium content forms a passivation film on the steel surface, resulting in high corrosion resistance. The strength of this type of steel is closely related to its carbon content; higher carbon content significantly increases strength, hardness, and wear resistance, while decreasing cold plasticity and toughness. With its high hardness, wear resistance, moderate corrosion resistance, and high cost-effectiveness, 3Cr13 is an ideal material for cutting tools, load-bearing mechanical components, and certain industrial parts.

[0003] In recent years, with the rapid development of the domestic and international economies, the demand for stainless steel has increased dramatically due to consumption upgrades, and higher requirements have also been placed on the quality of stainless steel.

[0004] Table 1 lists the mainstream chemical composition range of 3Cr13 currently on the market. Its core characteristic is the ratio of high carbon (0.26%–0.35%) to medium chromium (12%–14%), resulting in an austenitic phase region in the equilibrium phase diagram. Through heat treatment (quenching + tempering), martensite structure is formed, achieving high strength (tensile strength ≥735MPa) and high hardness (48–53HRC), thus obtaining a material with high strength, high wear resistance, and corrosion resistance. This type of steel has high requirements for surface quality; therefore, the purity of the molten steel, the quality of the cast billet, and the surface quality of the hot-rolled steel coils are all critical. Consequently, the smelting cycle is long, energy consumption is high, and manufacturing costs are high.

[0005] Table 1: Chemical composition of 3Cr13 (wt%)

[0006] steel grades C Si Mn P S Ni Cr 3Cr13 0.26～0.35 ≤1.00 ≤1.00 ≤0.040 ≤0.030 ≤0.60 12.0～14.0

[0007] In summary, the existing technology has the following problems: the existing 3Cr13 high-carbon martensitic chromium stainless steel used for cutting tools has a long smelting cycle, high energy consumption, and high manufacturing cost. Summary of the Invention

[0008] This invention provides a short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools, which shortens the smelting cycle, reduces energy consumption, increases chromium yield, effectively reduces manufacturing costs and improves product quality.

[0009] Therefore, this invention proposes a short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. The chemical composition of the 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools is as follows (weight percentage): C: 0.29-0.31 wt%, Si ≤ 0.45 wt%, Mn: 0.50 wt%, P ≤ 0.030 wt%, S ≤ 0.008 wt%, N ≤ 0.006 wt%, Cr: 12.20-12.50 wt%, Ni: ≤ 0.20 wt%; the balance is Fe and unavoidable trace elements. The process route of the short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools is as follows: raw materials include 400 series stainless steel scrap, alloy melting furnace smelting, slag tapping, LF refining, continuous casting, hot delivery, hot rolling, inspection, black skin, annealing, pickling, and white skin finished product.

[0010] The alloy melting furnace smelting includes: adopting stepped power control and precise process temperature control, as well as the steel tapping and steel retention method. The steel tapping temperature is 1600±10℃, and the amount of steel retained after tapping is 5 to 6 tons.

[0011] The process of tapping steel with slag includes: top slag modification and rapid slag-making process: adding ferrosilicon powder to reduce the oxidizing properties of top slag, adding lime and fluorite according to the ratio, the slag-to-steel ratio is 0.03-0.05, the basicity of top slag is 2.0-2.3, reducing the refining cycle and promoting the flotation and removal of steel inclusions, thereby improving the purity of molten steel;

[0012] In LF refining, a two-stage chromium reduction process is adopted: top slag reduction is carried out before tapping and during LF refining to reduce the Cr2O3 content in the slag and increase the chromium recovery rate.

[0013] This invention also proposes a 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. The chemical composition of this 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools, by weight percentage, is: C: 0.29–0.31 wt%, Si ≤ 0.45 wt%, Mn: 0.50 wt%, P ≤ 0.030 wt%, S ≤ 0.008 wt%, N ≤ 0.006 wt%, Cr: 12.20–12.50 wt%, Ni: ≤ 0.20 wt%; the balance being Fe and unavoidable trace elements. The 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools is manufactured using a short-process manufacturing method.

[0014] Specifically, this invention proposes a 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. The chemical composition (weight percentage) of the 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools is as follows: C: 0.31wt%, Si: 0.43wt%, Mn: 0.35wt%, P: 0.028wt%, S: 0.006wt%, Ni: 0.45wt%, Cr: 12.35%, N: 0.06wt%. The 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools of this invention has no cracks, scabs, or pits on the surface of the cast billet, achieving a C-class center segregation ≤1.0 grade.

[0015] Furthermore, the cutting tool is made of 3Cr13 high-carbon martensitic chromium stainless steel, annealed, with a thickness of 3-5mm, yield strength of 350-400MPa, tensile strength of 500-550MPa, elongation of 22-26%, and hardness (HRBW) of 80-90.

[0016] Furthermore, the cutting tool is made of 3Cr13 high-carbon martensitic chromium stainless steel, annealed, with a thickness of 4mm, yield strength of 356MPa, tensile strength of 516MPa, elongation at break of 25.2%, and hardness (HRBW) of 82.

[0017] This invention optimizes the short-process production of 3Cr13 high-carbon martensitic chromium stainless steel through innovative process design. The alloy melting furnace smelting process adopts stepped power control and steel tapping and retention operations, with power consumption of ≤520kw / h per ton of steel, a smelting cycle of <100min for 70t of scrap steel, and a scrap steel recovery rate of >98.5%. The use of alloy melting furnace slag-carrying tapping method can effectively utilize the top slag of the alloy melting furnace to provide favorable conditions for rapid slag formation in the LF process, shortening the refining cycle by more than 9min. A two-stage chromium reduction technology has been developed, which can reduce the Cr2O3 content in the slag from 15%-18% to 0%. 25%, chromium recovery rate greater than 98.2%, composition hit rate over 98%; optimized protective slag and precise control of secondary cooling intensity to eliminate surface defects such as cracks, scabs, and pits on the billet, achieving Class C center segregation ≤1.0 grade; hot delivery process is adopted, with the surface temperature of the billet entering the furnace >400℃, avoiding the martensitic phase transformation temperature range (200~300℃), hot rolling single-phase zone heating and rolling to reduce post-rolling edge cracks, crack occurrence rate <0.3%, and the slow cooling rate of the steel coil after unloading is 80℃ / h; full annealing process is adopted to maximize the elimination of residual stress and improve the uniformity of the microstructure. Attached Figure Description

[0018] Figure 1 The process-temperature-time control curve is shown in the short-process manufacturing method of 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools of the present invention.

[0019] Figure 2 This is a diagram showing the surface condition of the slab in this invention. Detailed Implementation

[0020] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0021] The purpose of this invention is to provide a short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. This method utilizes an alloy melting furnace (electromagnetic induction furnace) to efficiently melt scrap steel with low energy consumption. The LF process rapidly forms slag to improve the purity of the molten steel. The continuous casting process employs a suitable protective slag and a weak cooling process to improve the internal and external quality of the cast billet. This shortens the smelting cycle, reduces energy consumption, and increases the chromium yield, effectively reducing manufacturing costs and improving product quality.

[0022] The technical solution adopted in this invention is: a 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. The chemical composition of this steel, by weight percentage, is: C: 0.29–0.31 wt%, Si ≤ 0.45 wt%, Mn: 0.50 wt%, P ≤ 0.030 wt%, S ≤ 0.008 wt%, N ≤ 0.006 wt%, Cr: 12.20–12.50 wt%, Ni: ≤ 0.20 wt%; the balance is Fe and unavoidable trace elements. The process route is: 400 series stainless steel scrap → alloy melting furnace → slag-bearing tapping → LF refining → continuous casting → hot delivery → hot rolling → inspection → black skin → annealing → pickling → white skin finished product.

[0023] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0024] A method for using 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools includes the following process steps:

[0025] S1, Scrap Steel Melting Stage

[0026] After selection, the dried 400 series stainless steel scrap is added to the alloy melting furnace in batches. The alloy melting furnace is, for example, an electromagnetic induction furnace or other melting furnace for stainless steel. It uses the principle of electromagnetic induction heating and adjusts the power in stages as the melting progresses to melt the scrap steel. The carbonizing agent is added at 1.0 kg / t, and the final carbon content is controlled at 0.25-0.28%, and the final temperature is controlled at 1600±10℃. In order to shorten the melting cycle of subsequent furnaces, 5-6 tons of high-temperature molten steel can be left in the furnace for preheating and providing basic heat for the scrap steel entering the furnace next.

[0027] S2, the first reduction stage of chromium

[0028] The first reduction stage of chromium is completed during the melting process or before tapping. In order to reduce the slag-making pressure of the next process and reduce the chromium metal oxide in the top slag, ferrosilicon powder can be added at 1.0 to 1.2 kg / t in the later stage of melting in the alloy melting furnace. This can effectively reduce the chromium metal oxide in the slag and improve the fluidity of the steel slag, and the slag-carrying tapping method can be adopted.

[0029] S3, LF process rapid slag formation stage

[0030] After the ladle enters the station, temperature measurement and sampling are carried out first. The slag-to-steel ratio is controlled at 0.03-0.05, the binary basicity of the top slag is controlled at 2.0-2.3, and lime and fluorite are added at 10-14 kg / t and 2-3 kg / t respectively. After the slag-forming auxiliary materials are added, medium-intensity argon blowing is started to slag.

[0031] S4, the second reduction stage of chromium

[0032] During the LF slag-making stage, ferrosilicon powder is added at a rate of 1.0 to 2.0 kg / t to deoxidize the top slag and reduce chromium metal oxides. Slag samples are taken using oxygen tubes for observation. The top slag should ideally turn white after cooling.

[0033] S5, Precise Temperature and Composition Control Stage

[0034] After the second reduction stage of chromium, temperature measurements and sampling are performed to determine whether the steel composition meets the standards or to clarify the required alloys and quantities. After the alloy materials are added, medium-intensity argon blowing for at least 3 minutes is required to ensure alloy melting and uniform steel composition. Subsequently, the temperature is raised to 1580±10℃ using submerged arc welding.

[0035] S6, Steel purity control stage

[0036] After the composition and temperature are adjusted, a soft blowing time of 10 minutes is required, with an exit temperature of 1570±10℃. After exiting the station, at least 15 minutes of sedation is required to promote the full floating of inclusions.

[0037] S7, High-precision control stage of continuous casting

[0038] The superheat is controlled at 20-35℃, the insertion depth of the outlet is 90mm, and 3Cr13 special stainless steel protective slag is used. The taper of the copper plate of the crystallizer is 1.2-1.4% / m, the vibration frequency is 120-150 times / min, the amplitude is ±3mm, the flow rate of the narrow face of the crystallizer is controlled at 220-250L / min, and the flow rate of the wide face is controlled at 1550-1600L / min. The secondary cooling water ratio is controlled at 0.35-0.40L / kg, the surface temperature gradient of the billet in the secondary cooling section is ≤100℃ / m, the surface temperature of the billet before straightening is >850℃, the billet is hot-fed, and the temperature of the billet entering the heating furnace is >400℃.

[0039] S8, Hot Rolling Stage

[0040] The temperature of the slab entering the heating furnace should be above 400℃. To control phase transformation cracks, the heating temperature should not be too high. Heating should be done in the single-phase zone to avoid heating in the two-phase zone. The thickness of the intermediate slab should be 36-38mm, and the thickness of the finished product should be 3-5mm. The amount of cooling water in the roller table and the cooling water in the rolls should be strictly controlled during finishing rolling to prevent the cooling water from splashing onto the surface of the steel strip. Laminar flow cooling should not be used before coiling. When the steel coil comes off the line, use red coil of 200 series steel grade J5 to surround it for slow cooling.

[0041] S9, Annealing Stage

[0042] Using a box furnace with a full annealing process, the metastable martensite structure is transformed into a stable structure (with uniform and fine spherical carbides distributed on a ferrite matrix), which makes the carbides spheroidized and uniformly distributed, improving the uniformity of the structure; eliminating or reducing the residual internal stress generated during hot rolling, giving it good cold working performance.

[0043] Furthermore, the scrap steel in S1 should meet the following requirements: C content below 0.25%, chromium content above 12.0%, and P content below 0.030%. The power of the alloy melting furnace during the melting process should be controlled within 25,000 kW, and the process power should be increased in a step-by-step manner, starting with a decrease, as the melting progresses.

[0044] Furthermore, the deoxidizer—ferrosilicon powder—used in S2 and S4 above should meet the following requirements: C < 0.2% and Si ≥ 68%.

[0045] Furthermore, the medium-intensity argon blowing used in S3 and S5 above should meet the requirement of an argon blowing flow rate of 300L / min and an exposed diameter of molten steel surface of ≤200mm.

[0046] Furthermore, the soft argon blowing used in S6 above should meet the requirement of an argon blowing flow rate of 150L / min and an exposed diameter of molten steel surface of ≤100mm.

[0047] Furthermore, the 3Cr13 special stainless steel protective slag used in the above S7 should meet the following requirements: C (solid) content between 1.40 and 1.45%, melting point between 1100 and 1140°C, melting rate between 20 and 22 seconds (at 1300°C), viscosity between 0.310 and 0.330 Pa·s (at 1300°C), and basicity between 1.10 and 1.20.

[0048] Furthermore, in the above-mentioned S8 step, the preheating section temperature in the heating furnace heating process is 700-800℃, the heating section temperature is 1260-1300℃, the soaking section temperature is 1280-1330℃, the heating time is ≥180min, the initial rolling temperature is 1170-1200℃, the final rolling temperature is 1000-1060℃, the coiling temperature is >880℃, and the cooling rate of the slow cooling process after the steel coil is taken off the line is 80℃ / h.

[0049] Furthermore, in step S9 above, after the hot-rolled coil is put into the furnace during the annealing process, it is rapidly heated to 450-460°C. After the furnace temperature reaches 460°C, it is uniformly heated to 850°C at a rate of 50°C / h and held for 30-35 hours. After the holding period, a segmented cooling method is adopted, and the coil is slowly cooled to 150°C in the furnace. The cooling process requires a time of more than 15 hours. After reaching 150°C, the coil is taken out of the furnace and allowed to cool naturally.

[0050] The main process of this invention:

[0051] 1) Composition Control: A type of 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools. The chemical composition of this steel by weight percentage is: C: 0.29-0.31 wt%, Si ≤ 0.45 wt%, Mn: 0.50 wt%, P ≤ 0.030 wt%, S ≤ 0.008 wt%, N ≤ 0.006 wt%, Cr: 12.20-12.50 wt%, Ni: ≤ 0.20 wt%; the balance is Fe and unavoidable trace elements. The 0.29-0.31 wt% C content can form Cr with chromium. 23 C6 carbides significantly improve the hardness of finished products and enhance the strength of the martensitic matrix through solid solution strengthening; a Cr content of 12.20–12.50 wt% can form a dense Cr2O3 passivation film to improve corrosion resistance, and the synergistic effect of C and Cr can improve various performance indicators of steel.

[0052] 2) High-efficiency and low-energy-consumption alloy melting furnace smelting process: adopts stepped power control and precise process temperature control, as well as steel tapping and steel retention method. The tapping temperature is 1600±10℃, and the amount of steel retained after tapping is 5 to 6 tons.

[0053] 3) Top slag modification and rapid slag-making process: Add ferrosilicon powder to reduce the oxidizing properties of top slag, add lime and fluorite according to the ratio, the slag-to-steel ratio is 0.03-0.05, the basicity of top slag is 2.0-2.3, reduce the refining cycle and promote the removal of inclusions in steel by flotation, thereby improving the purity of molten steel.

[0054] 4) Two-stage chromium reduction process: The top slag is reduced before tapping and during the LF refining process to reduce the Cr2O3 content in the slag and increase the chromium recovery rate.

[0055] 5) High-precision continuous casting control process: The continuous casting production adopts "weak cooling + low superheat + high straightening temperature + hot delivery" and optimizes the performance of protective slag. The casting speed is 0.9~1.1m / min, the superheat is 20~35℃, and the specific water content is 0.35~0.40L / kg. This ensures that the temperature drop of the billet in the section is ≤100℃ / m, reducing the generation of surface cracks on the slab and mitigating central segregation. The surface temperature of the billet before straightening is >850℃, which can avoid the brittle sensitive temperature range. The surface temperature of the slab entering the furnace is between 400~550℃, avoiding the martensitic phase transformation temperature range and reducing the occurrence of phase transformation cracks.

[0056] 6) Hot rolling process: During the heating process of the hot rolling furnace, the heating rate should be avoided to prevent thermal stress cracks; heating in the two-phase region should be avoided, as excessively high process temperatures can easily lead to the precipitation of δ-ferrite (high-temperature ferrite), which reduces thermoplasticity; slow cooling should be adopted to avoid excessively rapid cooling, which can cause high stress due to martensitic transformation and cracking.

[0057] 7) Annealing process: A segmented heating and cooling process is adopted to reduce the hardness of the steel coil, improve its plasticity and toughness, eliminate internal stress and improve the uniformity of the structure. Specific implementation examples:

[0059] A short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel cutting tools, such as... Figure 1 As shown, the horizontal axis represents time in minutes, and the vertical axis represents temperature in degrees Celsius, illustrating the key temperature control nodes and their timing relationships in the steelmaking process from scrap steel smelting to hot billet delivery. The specific process steps are as follows:

[0060] S1, Scrap Steel Melting Stage

[0061] After the top of the alloy melting furnace finishes tapping, 5 tons of high-temperature molten steel are left to preheat the scrap steel for the next furnace. 65 tons of dry scrap stainless steel are added to the furnace in batches. After the first batch of material is added, the initial temperature inside the furnace is 800℃, and the cycle is controlled within 100 minutes. When the amount added is 60 tons, ferrosilicon powder and carbon raiser are added to the furnace at 1.0 kg / t and 1.0~1.2 kg / t respectively. The tapping temperature is controlled at 1600±10℃.

[0062] S2, the first reduction stage of chromium

[0063] The top slag in the later stage of smelting has a high chromium oxide content. Some ferrosilicon powder has been added before tapping. The slag-carrying tapping method and the temperature of 1600℃ can accelerate the reduction of Cr2O3 in the slag. The alloy melting furnace has no oxygen blowing conditions, so the oxygen content in the steel is generally not high. It is mostly caused by oxidation due to contact with oxygen in the air during the smelting process. After the first stage of reduction, the free oxygen content in the steel is between 15 and 25 ppm.

[0064] S3, LF process rapid slag formation stage

[0065] After the ladle arrives at the LF station, lime and fluorite are added at 10-14 kg / t and 2-3 kg / t respectively. Since the molten steel contains its own slag, this reduces the consumption of slag-forming materials and the temperature drop caused by their addition, improving the submerged arc effect and enabling rapid slag formation. The slag-to-steel ratio is controlled at 0.03-0.05, and the binary basicity of the steel and slag is controlled at 2.0-2.3. The slag-forming time at this stage is 13 minutes.

[0066] S4, the second reduction stage of chromium

[0067] After slag formation, ferrosilicon powder is added twice at a ratio of 1.0 to 2.0 kg / t. The argon flow rate is adjusted to 300 L / min and medium-intensity argon blowing is started to promote the reaction at the steel-slag interface and achieve secondary reduction of Cr2O3 in the slag. This process involves blowing argon for 3 minutes. Under this condition, the top slag is a reducing white slag.

[0068] S5, Precise Temperature and Composition Control Stage

[0069] After the second reduction stage of chromium, temperature measurements and sampling are performed to determine whether the steel composition meets the standards or to clarify the required alloying elements and quantities. This steel grade has a large margin in C and Cr, generally requiring the addition of high-carbon ferrochrome to increase carbon and chromium content, depending on the actual situation. After the alloying materials are added, medium-intensity argon blowing for at least 3 minutes is necessary to ensure alloy melting and uniform steel composition. To compensate for the temperature drop caused by the reduction and alloying stages, the temperature needs to be raised again to 1580±10℃ to proceed to the next stage.

[0070] S6, Steel purity control stage

[0071] After the composition and temperature are adjusted, a soft blowing time of 10 minutes is required, with an exit temperature of 1570±10℃. After exiting the station, at least 15 minutes of sedation is required to promote the full floating of inclusions.

[0072] S7, High-precision control stage of continuous casting

[0073] This steel grade is highly sensitive to surface cracks and requires high-performance protective slag with good heat transfer and lubrication capabilities. The flow rate in the narrow face of the crystallizer is controlled at 220–250 L / min; the flow rate in the wide face is controlled at 1550–1600 L / min. The secondary cooling water ratio is controlled at 0.35–0.40 L / kg. The surface temperature gradient of the billet in the secondary cooling section is ≤100℃ / m, and the superheat is controlled at 20–35℃. The process of "weak cooling + low superheat + high straightening temperature" effectively controls center segregation. Controlling the surface temperature of the billet before straightening to 850℃ avoids the brittle-sensitive zone and reduces crack formation. Hot delivery of the billet reduces the risk of cracks caused by martensitic transformation during slab cooling.

[0074] The chemical composition of 3Cr13 martensitic chromium stainless steel, prepared according to the above steps, is shown in Table 2.

[0075] Table 2: Chemical Composition (wt%) of Example Steels Examples 1, 2, and 3 are from the same furnace and have the same composition.

[0076]

[0077] The 3Cr13 martensitic chromium stainless steel was prepared according to the above steps. The surface condition of the slab is shown in the figure. Figure 2The resulting slab surface is free of cracks, scars, and pits; the cross-sectional dimensions of the double-flow slab are 160mm*750mm.

[0078] 3Cr13 martensitic chromium stainless steel was prepared according to the above steps. The process parameters are collected and shown in Table 3.

[0079] Table 3: Collection of process parameters for steelmaking processes in examples 1, 2, and 3. Examples 1, 2, and 3 are from the same furnace and have the same steelmaking process parameters.

[0080]

[0081] In this example, the chromium yield increased from 90.22% to 98.50%, the smelting cycle could be controlled at 98 minutes, and the overall cycle time was shortened by 10 minutes; the average power consumption per ton of steel was 518 kWh, and the power consumption was reduced by more than 10%; the refining cycle was reduced from 50 minutes to 38 minutes; the surface of the slab produced was free of cracks, scabs, and pits, and the central segregation was controllable; the surface quality of the steel strip was good, and there were no defects such as peeling or black lines that would affect the surface quality of the finished tool.

[0082] S8, Hot Rolling Stage

[0083] The slab obtained above is fed into the furnace at a temperature of 480℃. The preheating temperature of the heating furnace is 700-800℃, and slow heating is required to ensure uniform heat penetration and reduce the risk of thermal stress cracking. The heating temperature is 1260-1300℃. At high temperatures, δ-ferrite (high-temperature ferrite) is easily precipitated, which reduces thermoplasticity and may cause edge cracks or surface cracks during rolling. Therefore, the soaking temperature is 1280-1330℃, the heating time is ≥180min, the initial rolling temperature is 1170-1200℃, and the final rolling temperature is 1000-1060℃. The intermediate slab thickness is 36-38mm, and the finished product thickness is 3-5mm. To avoid excessively fast cooling and high stress caused by martensitic transformation, laminar cooling is not used before coiling to ensure that the coiling temperature is above 880℃. After the steel coil is removed from the line, it is cooled slowly, with a required cooling rate of 80℃ / h. The chemical composition of 3Cr13 martensitic chromium stainless steel, prepared according to the above steps, is shown in Table 2.

[0084] S9, Annealing Stage

[0085] After being hot-rolled into the furnace, the temperature is rapidly increased to 450-460℃. Once the furnace temperature reaches 460℃, it is uniformly heated to 850℃ at a rate of 50℃ / h and held for 30-35 hours. After the holding period, a segmented cooling method is adopted, and the temperature is slowly cooled to 150℃ in the furnace. The cooling process requires a time of more than 15 hours. After reaching 150℃, the coil is removed from the furnace and allowed to cool naturally.

[0086] The above steps yield 3Cr13 martensitic chromium stainless steel. Examples 1, 2, and 3 are from the same furnace, with the same composition and steelmaking process parameters. The steelmaking process parameters differ after hot rolling. Their performance parameters are shown in Table 4.

[0087] Table 4: Mechanical Properties of Example Steels (Annealed State)

[0088] Example Specifications / mm Yield strength / MPa Tensile strength / MPa Elongation rate / % Hardness / HRBW Example 1 3.0 362 533 24.3 83 Example 2 4.0 356 516 25.2 82 Example 3 5.0 350 509 24.8 80

[0089] In Example 1, the preheating section temperature of the heating furnace was 780℃, the heating section temperature was 1260℃, the soaking section temperature was 1280℃, the heating time was 210 min, the initial rolling temperature was 1175℃, and a continuous rolling mill with 4 roughing stands and 9 finishing stands was used. The roughing reduction rate was 76.86%, the finishing reduction rate was 98.13%, and the final rolling temperature was 1050℃. The coiling temperature was 890℃, and the cooling rate after the steel coil was removed from the line was 80℃ / h. In the annealing process, after the hot-rolled coil was put into the furnace, it was rapidly heated to 460℃. After the furnace temperature reached 460℃, it was uniformly heated to 850℃ at a rate of 50℃ / h and held at that temperature for 33 hours. It was then slowly cooled to 150℃ in the furnace over a period of 16 hours, and then removed from the furnace and allowed to cool naturally.

[0090] In Example 2, the preheating section temperature of the heating furnace was 780℃, the heating section temperature was 1250℃, the soaking section temperature was 1270℃, the heating time was 210 min, the initial rolling temperature was 1170℃, and a continuous rolling mill with 4 roughing stands and 9 finishing stands was used. The roughing reduction rate was 76.25%, the finishing reduction rate was 89.47%, and the final rolling temperature was 1045℃. The coiling temperature was 880℃, and the cooling rate of the coil after it left the line was 80℃ / h. In the annealing process, after the hot-rolled coil was put into the furnace, it was rapidly heated to 460℃. After the furnace temperature reached 460℃, it was uniformly heated to 850℃ at a rate of 50℃ / h and held at that temperature for 33 hours. It then slowly cooled to 150℃ in the furnace over 16 hours and was removed from the furnace and allowed to cool naturally.

[0091] In Example 3, the preheating section temperature of the heating furnace was 780℃, the heating section temperature was 1250℃, the soaking section temperature was 1270℃, the heating time was 210 min, the initial rolling temperature was 1170℃, and a continuous rolling mill with 4 roughing stands and 9 finishing stands was used. The roughing reduction rate was 75.63%, the finishing reduction rate was 87.18%, and the final rolling temperature was 1045℃. The coiling temperature was 880℃, and the cooling rate of the coil after it left the line was 80℃ / h. In the annealing process, after the hot-rolled coil was put into the furnace, it was rapidly heated to 460℃. After the furnace temperature reached 460℃, it was uniformly heated to 850℃ at a rate of 50℃ / h and held at that temperature for 33 hours. It was then slowly cooled to 150℃ in the furnace over a period of 16 hours, and then removed from the furnace and allowed to cool naturally. The hot-rolled coils are then annealed. The annealed 3Cr13 steel sheet has a yield strength (ReL) of 350–400 MPa, a tensile strength (Rm) of 500–550 MPa, an elongation (A) of 22–26%, and a hardness (HRBW) of 80–90. This provides suitable hardness for subsequent cold working and improves the microstructure, making it suitable for heat treatment (quenching + tempering) or direct use. This significantly enhances the strength and service life of cutting tools, meeting various customer application scenarios. This demonstrates that the short-process smelting technology for 3Cr13 high-carbon martensitic chromium stainless steel is feasible and highly economical, significantly reducing energy consumption and carbon emissions, increasing chromium yield, shortening the smelting cycle, improving product quality, and reducing production costs.

[0092] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools, characterized in that, The chemical composition (by weight percentage) of the 3Cr13 high-carbon martensitic chromium stainless steel used for cutting tools is as follows: C: 0.29–0.31 wt%, Si ≤ 0.45 wt%, Mn: 0.50 wt%, P ≤ 0.030 wt%, S ≤ 0.008 wt%, N ≤ 0.006 wt%, Cr: 12.20–12.50 wt%, Ni: ≤ 0.20 wt%; the balance being Fe and unavoidable trace elements. The process route for the short-process manufacturing method of the 3Cr13 high-carbon martensitic chromium stainless steel used for cutting tools is as follows: raw materials include 400 series stainless steel scrap, alloy melting furnace smelting, slag tapping, LF refining, continuous casting, hot delivery, hot rolling, inspection, black skin, annealing, pickling, and white skin finished product. The alloy melting furnace smelting includes: adopting stepped power control and precise process temperature control, as well as the steel tapping and steel retention method. The steel tapping temperature is 1600±10℃, and the amount of steel retained after tapping is 5 to 6 tons. The process of tapping steel with slag includes: top slag modification and rapid slag-making process: adding ferrosilicon powder to reduce the oxidizing properties of top slag, adding lime and fluorite according to the ratio, the slag-to-steel ratio is 0.03-0.05, the basicity of top slag is 2.0-2.3, reducing the refining cycle and promoting the flotation and removal of steel inclusions, thereby improving the purity of molten steel; In LF refining, a two-stage chromium reduction process is adopted: top slag reduction is carried out before tapping and during LF refining to reduce the Cr2O3 content in the slag and increase the chromium recovery rate.

2. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, The continuous casting process includes: high-precision continuous casting control technology: casting speed 0.9~1.1m / min, superheat 20~35℃, specific water 0.35~0.40L / kg, ensuring that the temperature drop of the billet within the section is ≤100℃ / m, reducing the generation of surface cracks on the billet and mitigating central segregation, and ensuring that the surface temperature of the billet before straightening is >850℃, avoiding the brittle-sensitive temperature range; the surface temperature of the billet entering the furnace is between 400~550℃, avoiding the martensitic phase transformation temperature range, and reducing the occurrence of phase transformation cracks.

3. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, The alloy melting furnace smelting process specifically includes: after the steel is tapped from the upper furnace of the alloy melting furnace, 5 tons of high-temperature molten steel are left to preheat the scrap steel for the lower furnace. 65 tons of dry scrap stainless steel are added into the furnace in batches. After the first batch of material is added, the initial temperature inside the furnace is 800℃, and the cycle is controlled within 100 minutes. When the amount of material added is 60 tons, ferrosilicon powder and carbon raiser are added into the furnace at 1.0 kg / t and 1.0~1.2 kg / t respectively. The tapping temperature is controlled at 1600±10℃.

4. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, In LF refining, the free oxygen content in the steel after the first stage of reduction is between 15 and 25 ppm. In the second reduction stage of chromium: after slag formation, ferrosilicon powder is added twice at a ratio of 1.0 to 2.0 kg / t, and the argon flow rate is adjusted to 300 L / min to start medium-intensity argon blowing to promote the steel-slag interface reaction and achieve the secondary reduction of Cr2O3 in the slag. This process involves blowing argon for 3 minutes, and the top slag under this condition is a reducing white slag.

5. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, LF refining employs rapid slag formation, specifically including: after the ladle arrives at the LF station, lime and fluorite are added at 10-14 kg / t and 2-3 kg / t respectively. Since the molten steel itself carries slag, the consumption of slag-forming materials can be reduced and the temperature drop caused by the addition of slag-forming materials can be minimized, thus improving the submerged arc effect and enabling rapid slag formation. The slag-to-steel ratio is controlled at 0.03-0.05, and the binary basicity of steel and slag is controlled at 2.0-2.

3. The slag formation time at this stage is 13 minutes.

6. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, LF refining specifically includes: the steel purity control stage; after the composition and temperature are adjusted, a soft blowing time of 10 minutes is required, the outlet temperature is 1570±10℃, and at least 15 minutes of calming is required after leaving the station to promote the full flotation of inclusions.

7. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, During continuous casting, the superheat is controlled at 20-35℃, the sprue insertion depth is 90mm, 3Cr13 special stainless steel protective slag is used, the taper of the copper plate in the crystallizer is 1.2-1.4% / m, the vibration frequency is 120-150 times / min, the amplitude is ±3mm, the flow rate of the narrow face of the crystallizer is controlled at 220-250L / min, the flow rate of the wide face is controlled at 1550-1600L / min, the secondary cooling water ratio is controlled at 0.35-0.40L / kg, and the surface temperature gradient of the billet in the secondary cooling section is ≤100℃ / m.

8. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, During hot rolling, the temperature of the slab entering the heating furnace should be above 400℃, the thickness of the intermediate slab should be 36-38mm, and the thickness of the finished product should be 3-5mm.

9. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, In the heating process of the heating furnace, the preheating section temperature is 700-800℃, the heating section temperature is 1260-1300℃, the soaking section temperature is 1280-1330℃, the heating time is ≥180min, the initial rolling temperature is 1170-1200℃, the final rolling temperature is 1000-1060℃, the coiling temperature is >880℃, and the cooling rate of the slow cooling process after the steel coil is taken off the line is 80℃ / h.

10. The short-process manufacturing method for 3Cr13 high-carbon martensitic chromium stainless steel for cutting tools as described in claim 1, characterized in that, In the annealing process, after the hot-rolled coil is put into the furnace, it is rapidly heated to 450-460℃. After the furnace temperature reaches 460℃, it is uniformly heated to 850℃ at a rate of 50℃ / h and held for 30-35h. After the holding time is completed, a segmented cooling method is adopted, and the coil is slowly cooled to 150℃ in the furnace. The cooling process requires a time of more than 15h. After reaching 150℃, the coil is taken out of the furnace and cooled naturally.

Images