Fine pearlite corrosion-resistant hot-rolled saw blade steel and production method

Abstract

The application discloses a fine pearlite corrosion-resistant hot-rolled saw blade steel, which is characterized by the following components and wt%: C: 0.45-0.82%, Si: 0.16-0.47%, Mn: 0.20-1.20%, Cr: 0.20-1.00%, V: 0.01-0.06%, P: less than or equal to 0.010%, and S: less than or equal to 0.005%. The production method comprises the following steps: after conventional smelting, the cast billet is obtained; the cast billet is heated; after dephosphorization, rough rolling is performed; finishing rolling is performed; laminar flow cooling is performed; and coiling is performed. In the application, the stone is not stained by rust during cutting, the saw blade has no flaky rust layer, the extremely small inclusions reduce the risk of fracture during use, the fatigue performance of the saw blade is improved, the pearlite group size is 20-30 um, the pearlite sheet spacing size is 20-50 nm, the corrosion primary cell is prevented, and the tensile strength of the saw blade is greater than or equal to 900 MPa.

Description

Technical Field

[0001] This invention relates to a tool steel and its production method, specifically to a fine pearlitic corrosion-resistant hot-rolled saw blade steel and its production method. Background Technology

[0002] Diamond saw blades are primarily used for cutting stone. The base material is made of saw blade steel, which is circulated in cooling and dust-removing water during use. This makes them susceptible to corrosion from chloride ions in the water, reducing the blade's lifespan by up to 50%, causing stone to become contaminated and degraded by rust products, and posing a safety hazard due to breakage during use. To improve the corrosion resistance of saw blade steel, methods such as adding corrosion-resistant alloys, applying corrosion-resistant coatings, and surface oxidation treatments are commonly used, but these methods all have drawbacks, including increased costs and limited effectiveness. Therefore, the development of a corrosion-resistant saw blade steel is urgently needed.

[0003] Search results:

[0004] Chinese Patent Publication No. CN1069772A discloses "A High-Strength, Wear-Resistant, and Corrosion-Resistant Nickel-Chromium Based Alloy." Its composition involves a large amount of chromium, molybdenum, and tungsten dissolved in the matrix to form a high-strength alloy strengthened by intermetallic compounds. It exhibits a tensile strength ≥600MPa and a hardness ≥50HRC, achieving the performance characteristics of cobalt-based alloys. The metallurgical process is simple, and the production cost is low, making it particularly suitable for casting rods, welding supports, as a hardfacing alloy material, and for precision casting various parts and molds. The chemical composition (by weight percentage) of the alloy is: 0.02% carbon, 25–30% molybdenum, 12–18% tungsten, 25–35% chromium, and 30–40% nickel. Impurities include silicon, iron, manganese, and aluminum.

[0005] Chinese Patent Publication No. CN1162653A discloses a "Production Process of Ferritic Stainless Steel with Improved Corrosion Resistance". It is produced in the form of a flat billet, with the following composition by weight percentage: 18% < Chromium < 27%, 1% < Molybdenum < 3%, 1% < Nickel < 3%, Manganese < 1%, Silicon < 1%, Carbon < 0.030%, Nitrogen < 0.030%, 0.075% < Titanium < 0.20%, 0.20% < Niobium < 0.50%, Sulfur < 0.01%, Phosphorus < 0.1%, with the remainder being iron and impurities from the smelting of materials necessary for production. The production process consists of two steps: first, cooling to 900°C at a rate of 400°C to 600°C / hour; then, rapid cooling at a rate of 1200°C to 1400°C / hour.

[0006] Chinese Patent Publication No. CN1112964A discloses a salt bath composition suitable for forming an Fe3O4 layer on the surface of ferrous metal parts, including nitrided ferrous metal parts, to protect the underlying iron from corrosion. This protective layer, which is deep black, is impermeable, has good crystallization order, and has a corrosion potential greater than 1000 mV. The composition includes at least nitrate anions, sodium, and lithium cations, with the weight percentage of lithium ions relative to the salt bath between 0.1% and 5%, preferably between 0.5% and 1.75%.

[0007] Chinese Patent Publication No. CN1099811A discloses a method for nitriding ferrous metals, which not only achieves the surface properties of direct nitriding but also simultaneously achieves the effects of post-nitriding oxidation. The method involves immersing the component in a molten salt bath for an appropriate time. The molten salt bath typically contains alkali metal carbonates and cyanates, as well as a small amount of sulfur-containing substances. The component has a positive potential relative to the reverse electrode in contact with the salt bath. A low-to-high current flows from the component through the salt bath to the reverse electrode, and the concentration of cyanide formed by the side reaction is maintained below 6%. Advantageously, a constant current is used, typically with a current density of 300-800 A / m², a temperature of 450-650°C, and a treatment time of 10-150 minutes.

[0008] Chinese Patent Publication No. CN1211286A discloses "A Molten Zn-Al-Mg Electroplated Steel Sheet with Good Corrosion Resistance and Surface Appearance." This describes a molten Zn-based electroplated steel sheet with a Zn-Al-Mg electroplating layer formed on its surface. The layer consists of Al: 4.0–10 wt%, Mg: 1.0–4.0 wt%, with the balance being Zn and unavoidable impurities. This electroplating layer has a metallic structure in which a [primary Al phase] or [primary Al phase] and [Zn single phase] are mixed within a [ternary eutectic structure of Al / Zn / Zn2Mg]. To obtain an electroplating layer with this metallic structure, in a continuous molten electroplating apparatus, the cooling rate of the electroplating layer adhering to the strip drawn from the electroplating bath and the temperature of the electroplating bath are appropriately controlled, / or appropriate amounts of Ti and B are added to the electroplating bath. The morphology of the Mg-containing oxide film formed during the period until the electroplated layer solidifies can be controlled, or an appropriate amount of Be can be added to the electroplating bath to suppress the generation of the stripe pattern characteristic of the electroplated steel sheet.

[0009] The above-mentioned literature has the disadvantages of high alloy content and high production cost. It also uses oxidation and nitriding to form a surface protective layer to increase corrosion resistance, or electroplating to form a surface coating to improve corrosion resistance. All three methods have the disadvantage of requiring additional saw blade processing technology. Moreover, wear, damage and contamination are still likely to occur on the stone cutting surface, affecting the quality of the stone cutting surface. This will also lead to poor corrosion protection effect and low strength, which is far from meeting the needs of users. Summary of the Invention

[0010] This invention aims to overcome the shortcomings of existing technologies, such as high cost, contamination of the cut surface of stone, and low strength. It provides a method for producing fine pearlitic corrosion-resistant hot-rolled saw blade steel that, without increasing the process or alloying elements, prevents rust contamination of the stone during cutting, produces saw blades without flaky rust layers, minimizes inclusions to reduce the risk of breakage during use, improves the fatigue performance of the saw blade, has pearlite cluster size of 20-30µm, pearlite lamellar spacing of 20-50nm to prevent corrosion galvanic cells, and a tensile strength ≥900MPa.

[0011] Measures to achieve the above objectives:

[0012] A fine pearlitic corrosion-resistant hot-rolled saw blade steel has the following composition and weight percentage content: C: 0.45-0.82%, Si: 0.16-0.47%, Mn: 0.20-1.20%, Cr: 0.20-1.00%, V: 0.01-0.06%, P≤0.010%, S≤0.005%, with the remainder being iron and unavoidable impurities; the microstructure of the hot-rolled plate is pearlitic, with pearlite cluster size of 20-30 μm and pearlite lamellar spacing of 20-50 nm; tensile strength ≥900 MPa.

[0013] A method for producing a fine pearlitic corrosion-resistant hot-rolled saw blade steel, comprising the following steps:

[0014] 1) After conventional smelting, the billet is continuously cast into a billet, and the continuous casting temperature is controlled at 1460~1508℃, the cooling water flow of the continuous casting crystallizer is 5000~7000L / min, and the solidification cooling rate of the billet is not less than 100℃ / s.

[0015] 2) Heat the billet and control the billet temperature upon entering the furnace at 800–1000℃, and the billet heating temperature at 1100℃–.

[0016] 1160℃, billet time in furnace is 15-51 min, soaking temperature is 1100-1160℃, and the temperature difference in the width direction is...

[0017] <10℃;

[0018] 3) After dephosphorization, 7 passes of rough rolling are performed, and the single-pass reduction rate of the first and second passes is controlled to be no less than 55%, and the austenite grain size of the crystal refinement is controlled to be ≥6.

[0019] 4) Perform finish rolling and control the final rolling temperature at 800–920℃;

[0020] 5) Perform laminar flow cooling, cooling to the coiling temperature at a cooling rate of 100-80℃ / s and controlling the austenite grain size to be no less than grade 7;

[0021] 6) Perform winding, control the winding temperature at 350-600℃, and control the pearlite interlayer spacing at 20-50nm.

[0022] Preferably, the final rolling temperature is controlled at 815–890°C.

[0023] Preferably, the laminar flow cooling rate is 92–87 °C / s.

[0024] Preferably, the winding temperature is 415–550°C, and the pearlite interlayer spacing is controlled to be 20–35 nm.

[0025] The role and mechanism of each component and main process in this invention

[0026] C: Carbon in steel mainly plays a role in improving the strength and hardenability of the steel. In hot-rolled structures, carbon exists in the form of carbides, forming pearlite, bainite, etc. After quenching, carbon exists in a solid solution state, and the structure undergoes phase transformation strengthening. After tempering, carbides precipitate, playing a precipitation strengthening role. Too high a carbon content will reduce the plasticity and toughness of the steel, while too low a carbon content will reduce the hardenability of the steel, which is not conducive to the heat treatment of saw blades. Therefore, it is controlled at 0.45% to 0.82%.

[0027] Silicon (Si): In steel, silicon enhances strength through solid solution strengthening and refines the interlamellar spacing of pearlite. However, it reduces plasticity and toughness, and increases surface defects in hot-rolled plates. Silicon is a major deoxidizer, typically containing above 0.1% in steel; therefore, the Si content is controlled between 0.16% and 0.47%.

[0028] Mn: Manganese in steel increases the strength of the steel and combines with sulfur (S) in the steel to form MnS, thus eliminating the influence of sulfur. Mn is a good deoxidizer and can effectively refine pearlite; therefore, the Mn content is controlled at 0.20–1.20%.

[0029] Cr: Chromium can improve strength, hardenability and tempering resistance, and reduce the decarburized layer of hot-rolled plates. However, chromium will significantly increase the banded structure of steel and affect the uniformity of the structure. Therefore, the Cr content is controlled between 0.20 and 1.00%.

[0030] V: Vanadium can refine the grain structure, improve strength and toughness, and also improve tempering resistance. In this invention, the V content is controlled at 0.01-0.06%.

[0031] The reason why this invention controls the continuous casting temperature to be between 1460 and 1508°C, the cooling water flow rate of the continuous casting crystallizer to be between 5000 and 7000 L / min, and the solidification cooling rate of the billet to be no less than 100°C / s is that a faster cooling rate can control the segregation of the billet and prevent defects such as banded structures and central martensite caused by segregation from affecting the performance of the finished product.

[0032] The reason why the argon flow rate is controlled at 30-100 L / min for 5-10 minutes in this invention is that argon blowing at this flow rate allows inclusions in molten steel to float to the surface and be discharged, reducing the level of inclusions and preventing the formation of large particle inclusions.

[0033] The reason why this invention controls the billet entry temperature to be 800-1000℃, the billet heating temperature to be 1100℃-1160℃, the billet time in the furnace to be 15-51 min, the homogenization temperature to be 1100-1160℃, and the temperature difference in the width direction to be <10℃ is that increasing the billet temperature reduces the rolling force of hot rolling, and improving the temperature uniformity can improve the stability of hot rolling and optimize the thickness and shape of the hot-rolled plate.

[0034] The reason why the single-pass reduction rate of the first and second passes is not less than 55% is that the grains can be refined under rapid high pressure, which provides a basis for the refinement of the finished product grain size and the refinement of the inter-wafer spacing.

[0035] The reason why the final rolling temperature is controlled at 800-920℃ is that the hot-rolled plate can achieve complete recrystallization at this temperature, preventing deformation structure from causing plate shape difference and uneven structure.

[0036] The reason why the cooling rate is controlled at 100-80℃ / s in this invention is that this rapid cooling rate can prevent the formation of ferrite and coarse pearlite, and can prepare for the finished product to refine the pearlite size and pearlite lamellar spacing.

[0037] The reason why the winding temperature is controlled at 350-600℃ and the pearlite lamellar spacing is controlled at 20-50nm is that low-temperature phase transformation can refine the pearlite lamellar spacing. The refined pearlite structure will dissolve more fully in the final heat treatment process, forming a large number of fine residual carbides, which can fully refine the structure of the heat-treated finished product.

[0038] Compared with the prior art, this invention, without increasing the process or alloying elements, ensures that the stone is not contaminated by rust when cutting stone, the saw blade has no flaky rust layer, and the minimal inclusions reduce the risk of breakage during use, improve the fatigue performance of the saw blade, the pearlite cluster size is 20-30um, the pearlite lamellar spacing is 20-50nm, preventing the formation of corrosion galvanic cells, and the tensile strength of the saw blade is ≥900MPa. Attached Figure Description

[0039] Figure 1 The image shows the metallographic structure of the hot-rolled steel plate of this invention. Detailed Implementation

[0040] The present invention will now be described in detail:

[0041] Table 1 is a list of chemical components for each embodiment, i.e., comparative example, of the present invention;

[0042] Table 2 is a list of the main hot-rolled plate production process parameters for each embodiment and comparative example of the present invention;

[0043] Table 3 lists the test results and corrosion resistance of the manufactured saw blades for each embodiment and comparative example of the present invention.

[0044] The various embodiments of the present invention are produced according to the following steps.

[0045] 1) After conventional smelting, the billet is continuously cast into a billet, and the continuous casting temperature is controlled at 1460~1508℃, the cooling water flow of the continuous casting crystallizer is 5000~7000L / min, and the solidification cooling rate of the billet is not less than 100℃ / s.

[0046] 2) Heat the billet and control the billet temperature entering the furnace at 800–1000℃, the billet heating temperature at 1100℃–1160℃, the billet time in the furnace at 15–51 min, the soaking temperature at 1100–1160℃, and the temperature difference in the width direction.

[0047] <10℃;

[0048] 3) After dephosphorization, 7 passes of rough rolling are performed, and the single-pass reduction rate of the first and second passes is controlled to be no less than 55%, and the austenite grain size of the crystal refinement is controlled to be ≥6.

[0049] 4) Perform finish rolling and control the final rolling temperature at 800–920℃;

[0050] 5) Perform laminar flow cooling, cooling to the coiling temperature at a cooling rate of 100-80℃ / s and controlling the austenite grain size to be no less than grade 7;

[0051] 6) Perform winding, control the winding temperature at 350-600℃, and control the pearlite interlayer spacing at 20-50nm.

[0052] Table 1. List of chemical components (wt%) of various embodiments and comparative examples of the present invention.

[0053]

[0054] Table 2. List of main hot-rolled plate production process parameters for each embodiment and comparative example of the present invention.

[0055]

[0056] Table 3 lists the test results and corrosion resistance of the saw blades manufactured according to various embodiments and comparative examples of the present invention.

[0057]

[0058]

[0059] As can be seen from Table 3, the pearlite clusters and interlaminar spacing of the steel plate of the present invention are small, and the saw blades produced after heat treatment have no corrosion products during use and will not contaminate the stone, thus realizing the production of corrosion-resistant saw blades.

[0060] This specific embodiment is merely a best example and is not intended to limit the implementation of the technical solution of the present invention.

Claims

1. A method for producing a fine pearlitic corrosion-resistant hot-rolled saw blade steel, comprising the following steps: 1) After conventional smelting, the billet is continuously cast into a billet, and the continuous casting temperature is controlled at 1460~1508℃, the cooling water flow of the continuous casting crystallizer is 5000~7000L / min, and the solidification cooling rate of the billet is not less than 100℃ / s. 2) Heat the billet and control the billet temperature in the furnace at 800-950℃, the billet heating temperature at 1120℃-1140℃, the billet time in the furnace at 15-51 min, the soaking temperature at 1100-1160℃, and the temperature difference in the width direction at <10℃. 3) After dephosphorization, 7 passes of rough rolling are performed, and the single-pass reduction rate of the first and second passes is controlled to be no less than 55%, and the austenite grain size of the crystal refinement is controlled to be ≥6. 4) Perform finish rolling and control the final rolling temperature at 800–840℃; 5) Perform laminar flow cooling, cooling to the coiling temperature at a cooling rate of 100-80℃ / s and controlling the austenite grain size to be no less than grade 7; 6) Perform winding, controlling the winding temperature at 350–550℃ and the pearlite interlaminar spacing at 20–50 nm; The fine pearlitic corrosion-resistant hot-rolled saw blade steel has the following composition and weight percentage content: C: 0.45-0.82%, Si: 0.16-0.47%, Mn: 0.80-1.20%, Cr: 0.68-1.00%, V: 0.01-0.06%, P≤0.010%, S≤0.005%, with the remainder being iron and unavoidable impurities; the metallographic structure of the hot-rolled plate is pearlitic, with pearlite cluster size of 20-30 μm and pearlite lamellar spacing of 20-50 nm; tensile strength ≥900 MPa.

2. The method for producing a fine pearlitic corrosion-resistant hot-rolled saw blade steel as described in claim 1, characterized in that: The laminar flow cooling rate is 92–87 °C / s.

3. The method for producing a fine pearlitic corrosion-resistant hot-rolled saw blade steel as described in claim 1, characterized in that: The winding temperature is between 415 and 550°C, and the pearlite interlayer spacing is controlled between 20 and 35 nm.

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