CN109295384B - Free-cutting steel containing sulfur, tin and tellurium and preparation method thereof - Google Patents
Free-cutting steel containing sulfur, tin and tellurium and preparation method thereof Download PDFInfo
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- CN109295384B CN109295384B CN201811006633.8A CN201811006633A CN109295384B CN 109295384 B CN109295384 B CN 109295384B CN 201811006633 A CN201811006633 A CN 201811006633A CN 109295384 B CN109295384 B CN 109295384B
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Abstract
The invention discloses a free-cutting steel containing sulfur, tin and tellurium and a manufacturing method thereof, wherein the mass percentages of Mn, S and Te in the steel meet Mn/Te >20, and 0.05< Te/S < 0.30. The production process of the steel grade comprises the following steps: converter smelting → LF furnace refining → continuous casting → heating furnace heating → rolling, cooling → slow cooling, wherein the free-cutting element Sn is added in the form of tin-containing scrap steel during converter tapping or in the form of tin ingot at the final stage of refining, and the free-cutting element Te is added in the form of tellurium powder cored wire at the final stage of refining. The invention provides the super free-cutting steel which takes S, Sn and Te ternary free-cutting elements as the common leading factor, and not only ensures the good mechanical property of the steel, but also obtains the excellent free-cutting property through proper component regulation and control and proper proportion of Mn, S and Te elements, and provides the component proportion and the production process of a super free-cutting steel product so as to meet the production requirements of parts which need to be precisely machined and cut at high speed.
Description
Technical Field
The invention relates to free-cutting steel and a preparation method thereof, in particular to free-cutting structural steel containing tellurium and a preparation method thereof, which are applied to the technical field of ferrous metallurgy.
Background
Free-cutting steel refers to a type of steel in which a certain amount of free-cutting elements are added to improve the cutting performance of the steel. The free-cutting steel is mainly used for producing parts which have strict requirements on dimensional accuracy and roughness and relatively lower requirements on mechanical properties, and is widely applied to the fields of instruments and meters, watch parts, automobiles, machine tools, aviation, aerospace, satellites, electronic equipment and the like. With the rapid development of automation, high speed and precision of cutting processing, the proportion of machining cost in the manufacturing cost of parts is higher and higher, sometimes even reaching 40% -60% of the manufacturing cost of parts, and the market urgently needs steel with excellent cutting performance to reduce the machining cost.
Although China is a big country for steel production, free-cutting steel in China starts late, the varieties, the yield, the technology, the quality stability and the variety of the free-cutting steel have great differences compared with foreign countries, the amount of the free-cutting steel in China is only one million tons in 2017, which is less than 1/3 of the yield of Japanese free-cutting steel, and many high-end free-cutting steel varieties need to be imported.
The sulfur series and lead series free-cutting steel are two kinds of free-cutting steel which are widely applied at present. The lead free-cutting steel has good cutting performance, but lead is a recognized non-environment-friendly substance, and lead steam generated in the production process has great harm to the health of workers; after lead enters the product, the lead is not easy to remove due to stable chemical property, and the lead is harmful to the reuse of waste steel, so that the European Union clearly prohibits the addition of lead in steel. Therefore, various iron and steel companies in the world are moving toward lead-free-cutting steel.
The cutting performance of the chalcogenide free-cutting steel is increased along with the increase of the content of sulfur, but the chalcogenide free-cutting steel is difficult to achieve good cutting performance, and under the same condition, the cutting performance is 30-40% different from that of the lead free-cutting steel. Too high a sulphur content will also lead to deformation of the sulphides in the steel in the rolling direction, resulting in anisotropy of the properties of the steel, reducing the mechanical properties of the steel. Therefore, the development and production of environmentally friendly high performance lead-free-cutting steel becomes an important direction for the development of free-cutting steel and a technical problem to be solved urgently.
Tin and lead are in the same main group and have similar physical and chemical properties, and are one of the free cutting elements. The tin-containing steel has a brittle valley at a temperature of about 275 ℃, and when the tin-containing steel is subjected to cutting processing, the steel tends to be brittle fracture when the cutting temperature (250-400 ℃) is near the brittle valley, so that chip breaking is easily generated in the cutting process, and the cutting performance of the steel is improved. The tin has high boiling point, low vapor pressure, difficult volatilization and no toxicity, and the production and the use of the free-cutting steel can not generate adverse effect on the ecological environment, so the steel is considered as a new green and environment-friendly steel. The tin has wide resources and proper price and is an ideal substitute element for lead. However, a relatively low tin content makes it difficult to achieve a relatively high machinability, while a high tin content causes segregation of tin at austenite grain boundaries during hot rolling, which causes material brittleness and adversely affects process properties.
Tellurium and sulfur are in the same main group and have similar physical and chemical properties, and are usually used in the production of some super-free-cutting steels, and play a role in modifying manganese sulfide inclusions in the steel, so that the manganese sulfide inclusions are converted into spherical or spindle shapes, and the cutting performance of the steel is improved. A small amount of MnTe formed in the steel can play a role in lubrication in the cutting process, thereby improving the cutting performance. The use amount of tellurium is small, the effect of improving the cutting performance of steel is obvious, but the price of tellurium is higher, and the production cost is obviously increased due to a large addition amount.
Chinese patent publication No. CN1540022A discloses tin-containing free-cutting structural steel, which is characterized in that: the steel is added with high-content tin (0.09-0.25 wt%), and the steel comprises the following components: 0.05 to 0.50% of C, 0 to 0.4% of Si, 0.3 to 2.0% of Mn, 0 to 2.0% of Cr, 0.005 to 0.35% of S, 0.005 to 0.050% of P, 0.09 to 0.25% of Sn, 0.001 to 0.010% of O and the balance of Fe. The steel contains a certain amount of Sn, so that the cutting performance is improved to a certain extent, but the steel still belongs to common free-cutting steel, and cannot meet the production requirement of parts needing ultrahigh cutting performance.
Chinese patent publication No. CN106978570A discloses a free-cutting steel with high tin content and a preparation method thereof, which is characterized in that the alloying of Mo, W and rare earth element La is performed on the free-cutting steel to solve the problem of the current hot brittleness of the free-cutting steel caused by overhigh tin content. The free-cutting steel comprises the following basic chemical elements in percentage by mass: 0.02-0.77% of C, 0.01-0.10% of Si, 0.30-1.50% of Mn, 0-0.035% of S, 0-0.025% of P, 0.05-0.35% of Sn, 0.2-0.75% of Mo, 0.4-2.25% of W, 0.002-0.020% of La and the balance of iron and inevitable impurities. In order to obtain better cutting performance, the Sn addition amount is higher, the addition types of alloy elements are more, the content is high, the complexity of the preparation process is increased, the energy consumption is improved, and the cost is increased.
Chinese patent publication No. CN101597725A discloses free-cutting chromium stainless steel for ball-point pen tips, which is characterized in that: the matrix is Fe, and the other components are as follows: less than or equal to 0.03 percent of C, less than or equal to 1.00 percent of Si, less than or equal to 2.00 percent of Mn, less than or equal to 0.5 percent of S, less than or equal to 0.05 percent of P, 19-21 percent of Cr, 1.5-2.5 percent of Mo, 0.10-0.30 percent of Pb, 0.01-0.07 percent of Te and more than or equal to 50ppm of O. It contains an alloying element Pb, which, although increasing the machinability of the steel, is toxic and environmentally polluting.
Chinese patent publication No. CN105088106A discloses a composite free-cutting steel containing tin and bismuth, which comprises the following main components in percentage by weight: 0.06 to 0.09 percent of C, less than or equal to 0.10 percent of Si, 1.30 to 1.60 percent of Mn, 0.08 to 0.12 percent of P, 0.35 to 0.45 percent of S, 0.003 percent of Bi and 0.1 percent of Sn. Although the steel has better cutting performance, the oxidation burning loss and evaporation of Bi are huge in the smelting process, the yield of Bi is lower, the industrial production cost is high, the difficulty is high, and cracks of Bi-containing casting blanks are obvious.
In summary, free-cutting steel is an important special steel, and has irreplaceable effect in the production and processing processes of some precision parts. With the rapid development of automation, high speed and precision of cutting processing, the traditional free-cutting steel cannot meet the production requirement of high-precision products, and the existing Pb-containing free-cutting steel with high cutting performance faces the pressure of environmental protection, so that the application is limited.
Disclosure of Invention
In order to solve the problems of the prior art, the invention aims to overcome the defects of the prior art, provide the free-cutting steel containing the sulfur, the tin and the tellurium and the preparation method thereof, and provide the environment-friendly free-cutting steel containing the sulfur, the tin and the tellurium, and the invention further improves the cutting performance of the steel by adding a proper amount of Sn and Te on the basis of the sulfur-containing steel in order to obtain ultrahigh free-cutting performance. On the premise of ensuring environmental protection, the lead-containing free-cutting steel is better than the lead-containing free-cutting steel, so as to meet the increasing requirements of precise parts and mass rapid production. The invention takes S, Sn, Te ternary free-cutting elements as common leading 'super' free-cutting steel, and also ensures good mechanical property of the steel and obtains excellent free-cutting property through proper component regulation and control and proper proportion of Mn, S, Te elements, and provides the component proportion and the production process of a super free-cutting steel product so as to meet the production requirements of parts needing precision machining and high-speed cutting machining.
In order to achieve the purpose, the invention adopts the following technical scheme:
the free-cutting steel containing sulfur, tin and tellurium comprises the following components in percentage by mass: 0.05 to 0.50 percent of C, less than or equal to 0.15 percent of Si, 0.8 to 1.5 percent of Mn, less than or equal to 0.10 percent of P, 0.20 to 0.35 percent of S, 0.05 to 0.20 percent of Sn, 0.005 to 0.050 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te also meet the requirement that Mn/Te is more than 20 and 0.05< Te/S < 0.30.
As the preferred technical scheme of the invention, the free-cutting steel containing the sulfur, the tin and the tellurium comprises the following components in percentage by mass: 0.06-0.30% of C, less than or equal to 0.13% of Si, 0.9-1.4% of Mn, less than or equal to 0.09% of P, 0.20-0.30% of S, 0.06-0.18% of Sn, 0.008-0.040% of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te are required to satisfy Mn/Te >22, and 0.07< Te/S < 0.28.
As a further preferable technical scheme of the invention, the composition elements and the mass percentage content of the elements are as follows: 0.07 to 0.22 percent of C, less than or equal to 0.10 percent of Si, 1.0 to 1.3 percent of Mn, less than or equal to 0.08 percent of P, 0.25 to 0.30 percent of S, 0.08 to 0.16 percent of Sn, 0.010 to 0.035 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te are required to satisfy Mn/Te >25, and 0.08< Te/S < 0.25.
As a preferred technical scheme of the invention, the composite material comprises the following components in percentage by mass: 0.08 to 0.12 percent of C, less than or equal to 0.11 percent of Si, 1.1 to 1.15 percent of Mn, less than or equal to 0.09 percent of P, 0.24 to 0.28 percent of S, 0.14 to 0.16 percent of Sn, 0.015 to 0.020 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te are required to satisfy Mn/Te >57, and 0.06< Te/S < 0.08.
The invention relates to a preparation method of free-cutting steel containing sulfur, tin and tellurium, which comprises the following process flows of: converter smelting → LF furnace refining → continuous casting → heating furnace heating → rolling, cooling → slow cooling; wherein, the free-cutting element Sn is added in the form of tin-containing scrap steel when tapping from a converter, or is added in the form of tin ingots at the last refining stage of an LF (ladle furnace), and the free-cutting element Te is added in the form of tellurium powder cored wires at the last refining stage of the LF.
As a preferred technical scheme of the invention, the preparation method of the free-cutting steel containing the sulfur, tin and tellurium comprises the following steps:
(1) smelting in a converter: the molten iron of the converter is not desulfurized, only decarbonized and dephosphorized, the adding amount of lime is adjusted and controlled according to the silicon and phosphorus contents of the molten iron, and the phosphorus content of the tapped molten steel is controlled to be not higher than 0.10 percent; adding silicon-manganese alloy and slag charge during tapping 1/4, and carrying out weak deoxidation, wherein the total oxygen content is controlled to be 60-150 ppm; adding tin-containing waste steel for alloying during tapping, or adding no tin-containing waste steel during tapping, and then alloying in the subsequent LF furnace refining process;
(2) refining in an LF furnace: adding refining slag and submerged arc slag, adding ferrosilicon and silicon carbide to deoxidize the slag surface of the molten steel, controlling the pressure of argon blowing after electrifying according to the standard requirement that the molten steel does not turn over the slag surface, and adding ferrosilicon, high-carbon ferromanganese and tellurium powder core-spun yarns into the molten steel for alloying after white slag treatment; if tin-containing scrap steel is not added during tapping in the step (1), adding a tin ingot in an LF furnace refining link for alloying; adding iron sulfide to control the sulfur content, controlling the alloying refining time to be not less than 30min, and keeping the white slag refining time to be not less than 15 min;
(3) the continuous casting process comprises the following steps: high-sulfur covering slag is adopted for protective casting in the continuous casting process, the temperature of a tundish is controlled to be 1530-1550 ℃, the continuous casting drawing speed is controlled to be 0.70-1.0 m/min, secondary cooling water is weakly cooled, the cooling intensity is regulated, and the specific water amount in a secondary cooling area is controlled to be 0.18-0.30 ton of water/ton of steel so as to ensure the quality of a continuous casting blank;
(4) a casting blank heating system: carrying out hot feeding on the continuous casting blank, heating the continuous casting blank to 1150-1200 ℃ in a heating furnace, and controlling the total heating time according to the thickness of the casting blank to 0.95-1.05 min/mm;
(5) casting blank rolling and cooling process: rolling in a recrystallization zone, wherein the initial rolling temperature is 1150-1200 ℃, the final rolling temperature is more than or equal to 980 ℃, and air cooling is carried out after rolling;
(6) the slow cooling process comprises the following steps: and (3) slowly cooling the hot rolled steel in a heat preservation box at 720-760 ℃, and controlling the slow cooling time to be more than or equal to 48 hours, thereby obtaining the free-cutting steel containing sulfur, tin and tellurium.
The principle of the invention is as follows:
the influence of the element components on the cutting performance of the free-cutting steel containing sulfur, tin and tellurium in the invention is as follows:
c: the strength, plasticity, toughness, welding performance and the like of the steel are directly influenced by the carbon content. The increase of the carbon content can significantly improve the strength of the steel, and a certain amount of carbon content in the steel is required to ensure that the steel has sufficient hardness, but the carbon content is too high, so that the abrasion of the steel is serious, and the machinability is poor. In addition, carbon easily forms carbide with Mo, Fe, Cr, and the like. The secondary hardening effect generated by the precipitation of alloy carbides during tempering can further improve the hardness of the material. The carbon content of the free-cutting steel containing sulfur, tin and tellurium is within the range of 0.05-0.50%.
Si: silicon as a deoxidizer can control the degree of deoxidation, thereby affecting the deformation of inclusions in the steel and the machinability of the steel. Silicon can strongly improve the hardenability of a carburized layer, but is easy to generate grain boundary oxidation in the carburization process to form black net defects; with the increase of the addition amount of alloy elements, the martensite point of the steel is reduced, so that a large amount of residual austenite is contained in a hardened penetration layer, the fatigue performance and the wear resistance of the material are influenced, and the cutting performance of the material is deteriorated. The silicon content of the free-cutting steel containing S, Sn and Te is controlled below 0.15 percent.
Mn: manganese can improve the nucleation work and the transformation activation energy of pearlite and reduce the nucleation rate and the growth speed of the pearlite. Manganese and carbide thereof are dissolved in austenite, so that the isothermal transformation curve of the austenite is shifted to the right, the stability of the undercooled austenite is improved, the pearlite transformation is inhibited, and the hardenability is improved. MnS generated from manganese and sulfur in steel is an important free-cutting phase and may help improve cutting performance. In order to ensure good cutting performance and mechanical property, the content of manganese in the free-cutting steel containing sulfur, tin and tellurium is controlled to be within the range of 0.8-1.5%.
P: for structural steels, phosphorus is generally considered a detrimental element, but its dissolution in ferrite can improve the strength of the material. Therefore, in order to avoid the cold brittleness of phosphorus, the phosphorus content is generally controlled to be 0.10% or less, but phosphorus has an effect of improving the free cutting ability of steel, and therefore, the phosphorus content of the free cutting steel containing S, Sn, Te according to the present invention is controlled to be 0.10% or less.
S: sulfur is one of main free-cutting elements, and the cutting performance index of the steel is obviously improved along with the increase of the sulfur content in the steel. However, too high a sulfur content also causes the sulfides in the steel to deform in the rolling direction, resulting in anisotropy of the properties of the steel and lowering of the mechanical properties of the steel. Therefore, the sulfur content of the free-cutting steel containing the sulfur, the tin and the tellurium is controlled to be 0.20-0.35 percent.
Sn: tin and iron are mutually soluble in a high-temperature liquid state, and the maximum solubility in solid alpha-Fe reaches 17.7 percent. However, as the temperature decreases, the solubility of tin in steel decreases, and the solid solubility of Sn in α -Fe decreases sharply at 200 ℃ or lower, theoretically resulting in FeSn. But Sn diffuses very slowly, and Sn exists in a solid solution form without obvious macrosegregation; only a small portion of FeSn is formed, but in practice it is difficult to detect. Tin-containing steels have a brittle valley at around 275 c. When the cutting temperature is in the vicinity of the brittle valley at the time of cutting, the steel tends to be brittle-fractured, and chip breaking is easily generated during the cutting, thereby improving the cutting performance of the steel. However, when the content of tin is high, the material brittleness caused by the segregation of tin at austenite grain boundaries has a harmful effect on the process performance. Therefore, the content of tin in the free-cutting steel containing the sulfur, tin and tellurium is controlled to be 0.05-0.20%.
Te: part of tellurium is usually dissolved in MnS, and forms MnTe and wraps the MnS after saturation is reached. The solid solution state and the coating state of MnTe can lead MnS to be included and spheroidized, which is beneficial to improving the cutting performance and simultaneously avoids the anisotropy of the steel performance. The cutting force can be reduced in the cutting process, the surface roughness of a workpiece is reduced, the service life of the cutter is prolonged, and the like. The addition of a small amount of tellurium can obviously improve the cutting performance of the steel without influencing the mechanical strength of the steel. However, when the content of Te exceeds 0.1%, the plasticity and impact toughness of the steel are deteriorated. In order to obtain good cutting performance and not influence the mechanical performance of the steel, the tellurium content of the free-cutting steel containing the sulfur, tin and tellurium is 0.005-0.050%.
When Mn/Te in the steel is less than 10, iron telluride is formed in the steel, and cold-hot intergranular embrittlement of the steel may occur. Therefore, the contents of Mn and Te in the free-cutting steel containing S, Sn and Te according to the present invention should satisfy Mn/Te > 20.
When the content of Te in steel is small, Te is mainly dissolved in MnS inclusions in a solid solution, and the aspect ratio of the MnS inclusions is gradually reduced as the content of Te increases. When the Te content is saturated in MnS inclusions, MnTe is formed and wraps the MnS inclusions, so that MnS deformation can be inhibited in the hot working process and the lubricating effect can be achieved in the cutting process. The solid solution degree of Te in MnS is usually measured by the ratio of Te/S, and a certain ratio of Te/S is required to ensure a better MnS inclusion form and to have a favorable effect on the cutting process. Meanwhile, the cost of Te is considered, and the content of Te is not suitable to be excessively increased. The content of Te and S in the free-cutting steel containing S, Sn and Te of the invention is required to meet 0.05< Te/S < 0.30.
The sulfur-tin-tellurium-containing free-cutting steel produced by the process of the invention mainly contains MnS with Te in solid solution or MnS-coated MnS composite inclusion in addition to a certain amount of MnS, CaO and SiO2，Al2O3And composite inclusions with the same composition. Solid solution of Te can reduce the length-width ratio of MnS inclusions, is beneficial to improving the cutting performance and can also reduce the anisotropy of the performance of steel caused by long-strip MnS inclusions. MnTe can wrap MnS, thereby avoiding MnS deformation in the hot working process, playing a role in lubrication in the cutting process and being beneficial to improving the cutting performance of steel. Sn has higher solid solubility in high-temperature solid steel, but has low solubility at room temperature, so that the solid solubility of Sn in steel is sharply reduced in the cooling process, a certain amount of segregation is easily generated at a crystal boundary, and the function of making the crystal boundary brittle can be realized, thereby improving the cutting performance of steel.
Compared with the prior art, the invention has the following obvious and prominent substantive characteristics and remarkable advantages:
1. the invention provides an environment-friendly sulfur-tin-tellurium-containing free-cutting steel, which is used for further improving the cutting performance of the steel by adding a proper amount of Sn and Te on the basis of the sulfur-containing steel in order to obtain ultrahigh free-cutting performance;
2. the material of the sulfur-tin-tellurium-containing free-cutting steel has uniform transverse and longitudinal hardness, the average difference is not more than 10 percent, the material is uniform, and the quality is high;
3. when the sulfur-tin-tellurium-containing free-cutting steel is used for cutting, no chip accumulation phenomenon exists in the processing process, the chips are short and curled C-shaped chips, the surface of a processed workpiece is smooth and clean, the roughness is small, and the purpose of remarkably improving the cutting performance of steel is realized; under the condition of the same other components, the free-cutting steel containing the sulfur, the tin and the tellurium has better cutting performance than the traditional free-cutting steel containing the sulfur and the lead.
Drawings
FIG. 1 is a gold phase diagram of a SnTe containing steel for free-cutting steel containing SnTe according to an embodiment of the present invention.
FIG. 2 is an SEM of an inclusion in a S-Sn-Te containing free-cutting steel according to an embodiment of the present invention.
FIG. 3 is an SEM of another inclusion in a S-Sn-Te containing free-cutting steel according to an embodiment of the present invention.
FIG. 4 is a chip morphology of a free-cutting steel containing SnTe according to an embodiment of the present invention.
FIG. 5 is a chip morphology diagram of a prior art sulfur-lead-containing steel.
FIG. 6 is a gold phase diagram of a SnTe-containing steel of a SnTe-containing free-cutting steel according to example II of the present invention.
FIG. 7 is an SEM of an inclusion in a sulfur-tin-tellurium-containing free-cutting steel of example II of the present invention.
FIG. 8 is an SEM of another inclusion in a S-Sn-Te containing free-cutting steel according to example II of the present invention.
Detailed Description
The above-described scheme is further illustrated below with reference to specific embodiments, which are detailed below:
example one
In this example, a free-cutting steel containing S, Sn and Te, which contains C, Si, Mn, P, S, Sn and Te, and the balance of Fe and unavoidable impurities, contained the constituent elements and the contents of the elements in percentage by mass as shown in Table 1 below.
TABLE 1 main chemical composition control of free-cutting steel containing S, Sn and Te
The preparation method of the free-cutting steel containing S, Sn and Te comprises the following steps:
(1) smelting in a converter: the molten iron of the converter is not desulfurized, only decarbonized and dephosphorized, the adding amount of lime is adjusted and controlled according to the silicon and phosphorus contents of the molten iron, and the phosphorus content of the tapped molten steel is controlled to be not higher than 0.09%; when discharging 1/4, adding silicon-manganese alloy, tin-containing waste steel and slag charge, carrying out weak deoxidation, and controlling the total oxygen content at 150 ppm;
(2) refining in an LF furnace: adding refining slag and submerged arc slag, adding ferrosilicon and silicon carbide to deoxidize the slag surface of the molten steel, controlling the pressure of argon blowing after electrifying according to the standard requirement that the molten steel does not turn over the slag surface, and adding ferrosilicon, high-carbon ferromanganese and tellurium powder core-spun yarns into the molten steel for alloying after white slag treatment; adding iron sulfide to control the sulfur content, controlling the alloying refining time to be 35min, and keeping the white slag refining time to be 22 min;
(3) the continuous casting process comprises the following steps: high-sulfur covering slag is adopted for protective casting in the continuous casting process, the temperature of a tundish is controlled at 1530 ℃, the continuous casting drawing speed is controlled at 0.8m/min, secondary cooling water is weakly cooled, the cooling intensity is regulated and controlled, and the specific water amount in a secondary cooling area is controlled to be 0.20 ton of water/ton of steel so as to ensure the quality of a continuous casting blank;
(4) a casting blank heating system: carrying out hot feeding on the continuous casting blank, heating the continuous casting blank to 1150 ℃ in a heating furnace, and controlling the total heating time according to the thickness of the casting blank of 1.0 min/mm;
(5) casting blank rolling and cooling process: rolling in a recrystallization zone at the initial rolling temperature of 1150 ℃ and the final rolling temperature of 980 ℃, and then cooling in air;
(6) the slow cooling process comprises the following steps: and (3) slowly cooling the hot rolled steel in a heat preservation box at 720 ℃, and controlling the slow cooling time to be 50 hours, thereby obtaining the free-cutting steel containing the sulfur, tin and tellurium.
Experimental test analysis:
as a result of microscopic examination and observation of the free-cutting steel containing S, Sn and Te in the present example, as shown in FIGS. 1 to 3, MnS formed by Mn and S in the steel is an important free-cutting phase, which helps to improve the cutting performance. Part of tellurium is dissolved in MnS in a solid mode, and MnTe is formed after saturation is achieved and wraps the MnS. The solid solution state and the coating state of MnTe can lead MnS inclusion to develop towards spheroidization, which is beneficial to improving the cutting performance and simultaneously avoids the anisotropy of the steel performance. The S-Sn-Te containing free-cutting steel material of the embodiment has relatively uniform transverse and longitudinal hardness, and the average difference is not more than 10%.
The cutting experiment test is carried out on the free-cutting steel containing sulfur, tin and tellurium in the embodiment, referring to fig. 4 and 5, when the free-cutting steel containing sulfur, tin and tellurium in the embodiment is subjected to cutting machining, the machining process has no chip accumulation phenomenon, chips are short and curled C-shaped chips, and the machined workpiece has smooth surface, small roughness and excellent cutting performance. Fig. 5 is a chip morphology diagram of a sulfur-lead-containing steel in the prior art, and compared with the chip of the sulfur-lead-containing steel in the prior art, the C-shaped chip cut by the sulfur-tin-tellurium-containing free-cutting steel of the embodiment is shorter, and the C-shaped chip is more finely crushed, which indicates that the cutting performance of the sulfur-tin-tellurium-containing free-cutting steel of the present invention is more excellent than that of the conventional sulfur-lead-containing free-cutting steel.
The free-cutting steel containing the sulfur, tin and tellurium is environment-friendly high-performance lead-free-cutting steel, contains a super-free-cutting element Te, and further improves the cutting performance of the steel by regulating and controlling the form of manganese sulfide inclusions in the steel, so that the super-free-cutting steel is formed. The embodiment does not need higher addition amount of Sn, thereby avoiding the problem of overlarge hot brittleness of steel; the addition of Te can meet the requirement of high cutting performance, and the addition amount of Te is small, and the process is simple and convenient. In the embodiment, Sn is used for replacing Pb, so that the better cutting performance of the steel is ensured, meanwhile, the harm of Pb to human health and the environment is avoided, and the environment is protected. In the embodiment, the tellurium powder cored wire is adopted for wire feeding alloying, so that Te is not easy to oxidize and burn, the yield is high, and the production is easy. And Te can promote sulfide to be mixed into a spherical shape or a spindle shape, so that the condition that the sulfide becomes a thin strip in the rolling process is avoided, and the anisotropy of the steel performance is reduced.
Example two
This embodiment is substantially the same as the first embodiment, and is characterized in that:
in this example, a free-cutting steel containing S, Sn and Te, which contains C, Si, Mn, P, S, Sn and Te, and the balance of Fe and unavoidable impurities, contained the constituent elements and the contents of the elements in percentage by mass as shown in Table 1 below.
TABLE 2 control of the chemical composition of free-cutting steel containing S, Sn, Te in example II
The preparation method of the free-cutting steel containing S, Sn and Te comprises the following steps:
(1) smelting in a converter: the molten iron of the converter is not desulfurized, only decarbonized and dephosphorized, the adding amount of lime is adjusted and controlled according to the silicon and phosphorus contents of the molten iron, and the phosphorus content of the tapped molten steel is controlled to be not higher than 0.05 percent; adding silicon-manganese alloy and slag charge when tapping 1/4, and carrying out weak deoxidation, wherein the total oxygen content is controlled at 70 ppm;
(2) refining in an LF furnace: adding refining slag and submerged arc slag, adding ferrosilicon and silicon carbide to deoxidize the slag surface of the molten steel, controlling the pressure of argon blowing after electrifying according to the standard requirement that the molten steel does not turn over the slag surface, and adding ferrosilicon, high-carbon ferromanganese, tellurium powder core-spun yarns and tin ingots into the molten steel for alloying after white slag treatment; adding iron sulfide to control the sulfur content, controlling the alloying refining time to be 40min, and keeping the white slag refining time to be 20 min;
(3) the continuous casting process comprises the following steps: high-sulfur covering slag is adopted for protective casting in the continuous casting process, the temperature of a tundish is controlled at 1550 ℃, the continuous casting drawing speed is controlled at 0.9m/min, secondary cooling water is weakly cooled, the cooling intensity is regulated and controlled, and the specific water amount in a secondary cooling area is controlled to be 0.25 ton of water/ton of steel so as to ensure the quality of a continuous casting blank;
(4) a casting blank heating system: hot feeding the continuous casting blank, heating the continuous casting blank in a heating furnace to 1200 ℃, and controlling the total heating time according to the thickness of the casting blank of 1.02 min/mm;
(5) casting blank rolling and cooling process: rolling in a recrystallization zone at the initial rolling temperature of 1200 ℃ and the final rolling temperature of 980 ℃, and then cooling in air;
(6) the slow cooling process comprises the following steps: and (3) slowly cooling the hot rolled steel in a heat preservation box at 760 ℃, and controlling the slow cooling time to be 55 hours, thereby obtaining the free-cutting steel containing the sulfur, tin and tellurium.
Experimental test analysis:
as shown in FIGS. 6 to 8, MnS formed by Mn and S in the steel is an important free-cutting phase, which helps to improve the machinability. Part of tellurium is dissolved in MnS in a solid mode, and MnTe is formed after saturation is achieved and wraps the MnS. The solid solution state and the coating state of MnTe can lead MnS to be included and spheroidized, which is beneficial to improving the cutting performance and simultaneously avoids the anisotropy of the steel performance. The S-Sn-Te containing free-cutting steel material of the embodiment has relatively uniform transverse and longitudinal hardness, and the average difference is not more than 10%.
When the sulfur-tin-tellurium-containing free-cutting steel is subjected to cutting machining, no chip accumulation phenomenon exists in the machining process, the chips are short and curled C-shaped chips, and the machined workpiece is smooth in surface, small in roughness and excellent in cutting performance.
EXAMPLE III
This embodiment is substantially the same as the previous embodiment, and is characterized in that:
in this example, the sulfur-tin-tellurium-containing free-cutting steel of the present example, whose constituent elements and their element mass percentage contents are shown in Table 3 below, contained C, Si, Mn, P, S, Sn, Te, and the balance being iron and unavoidable impurities.
TABLE 3 control of the main chemical composition of free-cutting steel containing S, Sn, Te in the examples
The preparation method of the free-cutting steel containing S, Sn and Te comprises the following steps:
(1) smelting in a converter: the molten iron of the converter is not desulfurized, only decarbonized and dephosphorized, the adding amount of lime is adjusted and controlled according to the silicon and phosphorus contents of the molten iron, and the phosphorus content of the tapped molten steel is controlled to be not higher than 0.08 percent; when discharging 1/4, adding silicon-manganese alloy, tin-containing waste steel and slag charge, carrying out weak deoxidation, and controlling the total oxygen content at 60 ppm;
(2) refining in an LF furnace: adding refining slag and submerged arc slag, adding ferrosilicon and silicon carbide to deoxidize the slag surface of the molten steel, controlling the pressure of argon blowing after electrifying according to the standard requirement that the molten steel does not turn over the slag surface, and adding ferrosilicon, high-carbon ferromanganese and tellurium powder core-spun yarns into the molten steel for alloying after white slag treatment; adding iron sulfide to control the sulfur content, controlling the alloying refining time to be 35min, and keeping the white slag refining time to be 22 min;
(3) the continuous casting process comprises the following steps: high-sulfur covering slag is adopted for protective casting in the continuous casting process, the temperature of a tundish is controlled at 1530 ℃, the continuous casting drawing speed is controlled at 0.8m/min, secondary cooling water is weakly cooled, the cooling intensity is regulated and controlled, and the specific water amount in a secondary cooling area is controlled to be 0.30 ton of water/ton of steel so as to ensure the quality of a continuous casting blank;
(4) a casting blank heating system: carrying out hot feeding on the continuous casting blank, heating the continuous casting blank to 1150 ℃ in a heating furnace, and controlling the total heating time according to the thickness of the casting blank of 1.0 min/mm;
(5) casting blank rolling and cooling process: rolling in a recrystallization zone at the initial rolling temperature of 1150 ℃ and the final rolling temperature of 980 ℃, and then cooling in air;
(6) the slow cooling process comprises the following steps: and (3) slowly cooling the hot rolled steel in a heat preservation box at 720 ℃, and controlling the slow cooling time to be 50 hours, thereby obtaining the free-cutting steel containing the sulfur, tin and tellurium.
Experimental test analysis:
mn in the free-cutting steel containing S, Sn and Te in the embodiment and MnS generated by S in the steel are important free-cutting phases, and can help to improve the cutting performance. Part of tellurium is dissolved in MnS in a solid mode, and MnTe is formed after saturation is achieved and wraps the MnS. The solid solution state and the coating state of MnTe can lead MnS to be included and spheroidized, which is beneficial to improving the cutting performance and simultaneously avoids the anisotropy of the steel performance. The S-Sn-Te containing free-cutting steel material of the embodiment has relatively uniform transverse and longitudinal hardness, and the average difference is not more than 10%. When the sulfur-tin-tellurium-containing free-cutting steel is subjected to cutting machining, no chip accumulation phenomenon exists in the machining process, the chips are short and curled C-shaped chips, and the machined workpiece is smooth in surface, small in roughness and excellent in cutting performance.
Example four
This embodiment is substantially the same as the previous embodiment, and is characterized in that:
in this example, the sulfur-tin-tellurium-containing free-cutting steel of the present example, whose constituent elements and their element mass percentage contents are shown in Table 4 below, contained C, Si, Mn, P, S, Sn, Te, and the balance being iron and unavoidable impurities.
TABLE 4 control of main chemical composition of free-cutting steel containing S, Sn, Te in example IV
The preparation method of the free-cutting steel containing S, Sn and Te comprises the following steps:
(1) smelting in a converter: the molten iron of the converter is not desulfurized, only decarbonized and dephosphorized, the adding amount of lime is adjusted and controlled according to the silicon and phosphorus contents of the molten iron, and the phosphorus content of the tapped molten steel is controlled to be not higher than 0.08 percent; when discharging 1/4, adding silicon-manganese alloy, tin-containing waste steel and slag charge, carrying out weak deoxidation, and controlling the total oxygen content at 60 ppm;
(2) refining in an LF furnace: adding refining slag and submerged arc slag, adding ferrosilicon and silicon carbide to deoxidize the slag surface of the molten steel, controlling the pressure of argon blowing after electrifying according to the standard requirement that the molten steel does not turn over the slag surface, and adding ferrosilicon, high-carbon ferromanganese and tellurium powder core-spun yarns into the molten steel for alloying after white slag treatment; adding iron sulfide to control the sulfur content, controlling the alloying refining time to be 35min, and keeping the white slag refining time to be 22 min;
(3) the continuous casting process comprises the following steps: high-sulfur covering slag is adopted for protective casting in the continuous casting process, the temperature of a tundish is controlled at 1530 ℃, the continuous casting drawing speed is controlled at 0.8m/min, secondary cooling water is weakly cooled, the cooling intensity is regulated and controlled, and the specific water amount in a secondary cooling area is controlled to be 0.30 ton of water/ton of steel so as to ensure the quality of a continuous casting blank;
(4) a casting blank heating system: carrying out hot feeding on the continuous casting blank, heating the continuous casting blank to 1150 ℃ in a heating furnace, and controlling the total heating time according to the thickness of the casting blank of 1.0 min/mm;
(5) casting blank rolling and cooling process: rolling in a recrystallization zone at the initial rolling temperature of 1150 ℃ and the final rolling temperature of 980 ℃, and then cooling in air;
(6) the slow cooling process comprises the following steps: and (3) slowly cooling the hot rolled steel in a heat preservation box at 720 ℃, and controlling the slow cooling time to be 50 hours, thereby obtaining the free-cutting steel containing the sulfur, tin and tellurium.
Experimental test analysis:
mn in the free-cutting steel containing S, Sn and Te in the embodiment and MnS generated by S in the steel are important free-cutting phases, and can help to improve the cutting performance. Part of tellurium is dissolved in MnS in a solid mode, and MnTe is formed after saturation is achieved and wraps the MnS. The solid solution state and the coating state of MnTe can lead MnS to be included and spheroidized, which is beneficial to improving the cutting performance and simultaneously avoids the anisotropy of the steel performance. The S-Sn-Te containing free-cutting steel material of the embodiment has relatively uniform transverse and longitudinal hardness, and the average difference is not more than 10%. When the sulfur-tin-tellurium-containing free-cutting steel is subjected to cutting machining, no chip accumulation phenomenon exists in the machining process, the chips are short and curled C-shaped chips, and the machined workpiece is smooth in surface, small in roughness and excellent in cutting performance.
In summary, the production process of the free-cutting steel containing S, Sn and Te according to the embodiment of the invention comprises the following steps: converter smelting → LF furnace refining → continuous casting → heating furnace heating → rolling, cooling → slow cooling, wherein the free-cutting element Sn is added in the form of tin-containing scrap steel during converter tapping or in the form of tin ingot at the final stage of refining, and the free-cutting element Te is added in the form of tellurium powder cored wire at the final stage of refining. In the embodiment of the invention, the super free-cutting steel which takes the S, Sn and Te ternary free-cutting elements as the common leading factor ensures the good mechanical property of the steel and obtains the excellent free-cutting property through proper component regulation and control and proper proportion of the Mn, S and Te elements, and provides the component proportion and the production process of the super free-cutting steel product so as to meet the production requirements of parts which need to be precisely machined and cut at high speed.
While the embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above embodiments, but various changes may be made therein according to the purpose of the invention, and any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principles of the present invention shall be equivalent substitutions, so long as the purpose of the present invention is met, and all such changes and modifications shall fall within the scope of the present invention without departing from the technical principles and inventive concepts of the free-cutting steel containing S, Sn, Te and the method for manufacturing the same.
Claims (5)
1. The free-cutting steel containing sulfur, tin and tellurium is characterized by comprising the following components in percentage by mass: 0.05 to 0.50 percent of C, less than or equal to 0.15 percent of Si, 0.8 to 1.5 percent of Mn, less than or equal to 0.10 percent of P, 0.20 to 0.35 percent of S, 0.05 to 0.20 percent of Sn, 0.005 to 0.050 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te also satisfy the relation of Mn/Te >20, and 0.05< Te/S < 0.30; the preparation process flow of the free-cutting steel containing sulfur, tin and tellurium is as follows: converter smelting → LF furnace refining → continuous casting → heating furnace heating → rolling, cooling → slow cooling; wherein, the free-cutting element Sn is added in the form of tin-containing scrap steel when tapping from a converter, or is added in the form of tin ingots at the last refining stage of an LF (ladle furnace), and the free-cutting element Te is added in the form of tellurium powder cored wires at the last refining stage of the LF.
2. The free-cutting steel containing sulfur, tin and tellurium as claimed in claim 1, wherein: the composite material comprises the following components in percentage by mass: 0.06 to 0.30 percent of C, less than or equal to 0.13 percent of Si, 0.9 to 1.4 percent of Mn, less than or equal to 0.09 percent of P, 0.20 to 0.30 percent of S, 0.06 to 0.18 percent of Sn, 0.008 to 0.040 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te also satisfy the relation of Mn/Te >22 and 0.07< Te/S < 0.28.
3. The free-cutting steel containing sulfur, tin and tellurium as claimed in claim 2, characterized in that: the composite material comprises the following components in percentage by mass: 0.07 to 0.22 percent of C, less than or equal to 0.10 percent of Si, 1.0 to 1.3 percent of Mn, less than or equal to 0.08 percent of P, 0.25 to 0.30 percent of S, 0.08 to 0.16 percent of Sn, 0.010 to 0.035 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te also satisfy the relation of Mn/Te >25 and 0.08< Te/S < 0.25.
4. The free-cutting steel containing sulfur, tin and tellurium as claimed in claim 1, wherein: the composite material comprises the following components in percentage by mass: 0.08 to 0.12 percent of C, less than or equal to 0.11 percent of Si, 1.1 to 1.15 percent of Mn, less than or equal to 0.09 percent of P, 0.24 to 0.28 percent of S, 0.14 to 0.16 percent of Sn, 0.015 to 0.020 percent of Te and the balance of iron and inevitable impurities, wherein the mass percentages of Mn, S and Te also satisfy the relation Mn/Te >57, and 0.06< Te/S < 0.08.
5. The method for producing a sulfur-tin-tellurium-containing free-cutting steel as set forth in claim 1, comprising the steps of:
(1) smelting in a converter: the molten iron of the converter is not desulfurized, only decarbonized and dephosphorized, the adding amount of lime is adjusted and controlled according to the silicon and phosphorus contents of the molten iron, and the phosphorus content of the tapped molten steel is controlled to be not higher than 0.10 percent; adding silicon-manganese alloy and slag charge during tapping 1/4, and carrying out weak deoxidation, wherein the total oxygen content is controlled to be 60-150 ppm; adding tin-containing waste steel for alloying during tapping, or adding no tin-containing waste steel during tapping, and then alloying in the subsequent LF furnace refining process;
(2) refining in an LF furnace: adding refining slag and submerged arc slag, adding ferrosilicon and silicon carbide to deoxidize the slag surface of the molten steel, controlling the pressure of argon blowing after electrifying according to the standard requirement that the molten steel does not turn over the slag surface, and adding ferrosilicon, high-carbon ferromanganese and tellurium powder core-spun yarns into the molten steel for alloying after white slag treatment; adding iron sulfide to control the sulfur content, controlling the alloying refining time to be not less than 30min, and keeping the white slag refining time to be not less than 15 min; if tin-containing scrap steel is not added during tapping in the step (1), adding a tin ingot in an LF furnace refining link for alloying;
(3) the continuous casting process comprises the following steps: high-sulfur covering slag is adopted for protective casting in the continuous casting process, the temperature of a tundish is controlled to be 1530-1550 ℃, the continuous casting drawing speed is controlled to be 0.70-1.0 m/min, secondary cooling water is weakly cooled, the cooling intensity is regulated, and the specific water amount in a secondary cooling area is controlled to be 0.18-0.30 ton of water/ton of steel so as to ensure the quality of a continuous casting blank;
(4) a casting blank heating system: carrying out hot feeding on the continuous casting blank, heating the continuous casting blank to 1150-1200 ℃ in a heating furnace, and controlling the total heating time according to the thickness of the casting blank to 0.95-1.05 min/mm;
(5) casting blank rolling and cooling process: rolling in a recrystallization zone, wherein the initial rolling temperature is 1150-1200 ℃, the final rolling temperature is more than or equal to 980 ℃, and air cooling is carried out after rolling;
(6) the slow cooling process comprises the following steps: and (3) slowly cooling the hot rolled steel in a heat preservation box at 720-760 ℃, and controlling the slow cooling time to be more than or equal to 48 hours, thereby obtaining the free-cutting steel containing sulfur, tin and tellurium.
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| CN109971918B (en) * | 2019-04-09 | 2021-01-12 | 上海大学 | Bismuth-tellurium composite adding process method for free-cutting steel |
| CN110117693B (en) * | 2019-04-09 | 2021-02-23 | 上海大学 | Tellurium addition process method of tellurium-containing free-cutting steel |
| CN110306101B (en) * | 2019-07-04 | 2020-08-11 | 北京首钢吉泰安新材料有限公司 | Sulfur alloying method for high-sulfur free-cutting stainless steel for smelting ball pen point by three-phase lined electroslag furnace |
| CN111187996B (en) * | 2020-01-21 | 2021-07-20 | 鞍钢股份有限公司 | Medium-carbon sulfur-selenium-containing wire rod for free-cutting steel and manufacturing method thereof |
| CN112063923B (en) * | 2020-09-07 | 2022-03-22 | 成都先进金属材料产业技术研究院股份有限公司 | 1300 MPa-grade RE-containing chalcogenide free-cutting steel 60mm bar and preparation method thereof |
| CN113462984B (en) * | 2021-07-16 | 2022-07-22 | 浙江青山钢铁有限公司 | High-corrosion-resistance super-free-cutting soft magnet ferrite stainless steel wire rod and preparation method thereof |
| CN113684420B (en) * | 2021-08-17 | 2022-06-24 | 浙江青山钢铁有限公司 | Calcium-tellurium-rare earth composite treated super free-cutting stainless steel and preparation method thereof |
| CN113913704B (en) * | 2021-12-13 | 2022-03-11 | 北京科技大学 | Tellurium-sulfur co-processed aluminum deoxidized steel and preparation method and application thereof |
| CN114250417B (en) * | 2021-12-17 | 2022-06-21 | 广东韶钢松山股份有限公司 | Tellurium-containing medium-carbon high-sulfur free-cutting steel, wire rod and production method of wire rod |
| CN114908216B (en) * | 2022-04-26 | 2023-09-01 | 东风商用车有限公司 | Bismuth tellurium adding method for free cutting steel, free cutting carburizing steel and application thereof |
| CN115216693A (en) * | 2022-07-13 | 2022-10-21 | 山西太钢不锈钢股份有限公司 | Lead-free-cutting stainless steel and preparation method thereof |
| CN115386800B (en) * | 2022-08-30 | 2023-10-20 | 鞍钢股份有限公司 | Low-carbon high-manganese-sulfur environment-friendly free-cutting steel and manufacturing method thereof |
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