CN113913689A - Jet high-speed steel without annular segregation and with secondary hardening and manufacturing method thereof - Google Patents
Jet high-speed steel without annular segregation and with secondary hardening and manufacturing method thereof Download PDFInfo
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/36—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.7% by weight of carbon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
- B21J5/002—Hybrid process, e.g. forging following casting
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
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- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C22C33/06—Making ferrous alloys by melting using master alloys
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
Abstract
The invention discloses a jet high-speed steel without annular segregation and with secondary hardening and a manufacturing method thereof, relating to the component design and the preparation technology of jet deposition high-vanadium niobium-containing wear-resistant high-speed steel, wherein the components comprise the following components in percentage by mass: carbon: 0.80-2.00%, tungsten: 0.00-9.00%, molybdenum: 1.00-9.00%, chromium: 4.00-6.00%, vanadium: 3.00 to 10.00%, niobium: 0.50 to 3.00%, silicon: 0.20 to 0.35%, manganese: 0.50-0.90%, sulfur: less than or equal to 0.040%, phosphorus: less than or equal to 0.040%, oxygen: 0.005-0.015%, nitrogen: 0.030 to 0.040%, and the balance being iron and inevitable impurities. The process comprises the following steps: the method comprises the following steps: preparing a smelting raw material according to the components; step two: intermediate frequency induction smelting: step three: atomizing, spraying and depositing; step four: forging; step five: and (6) heat treatment.
Description
Technical Field
The invention belongs to the field of jet deposition, powder metallurgy and rapid solidification high-speed steel, and particularly relates to jet high-speed steel without annular segregation and with secondary hardening and a manufacturing method thereof.
Background
The high-speed steel is high-alloy ledeburite steel containing more than 20% of alloy elements, has high hardness, excellent wear resistance, red hardness and high-temperature hardness, and has better toughness, so the high-speed steel is widely applied to the field of cutting machining and has a main position on multi-edge cutters (especially complex and precise cutters) and cutting machining tools subjected to impact and vibration. The composition of the carbide is high alloy martensite structure, incompletely dissolved primary carbide and secondary precipitated carbide. In order to avoid the shedding of carbides during wear and to withstand the high temperatures generated during cutting, the martensitic structure must have high hardness and temper resistance. The wear resistance is mainly determined by vanadium-based particulate carbides on the substrate. Primary W, Mo, V and secondary precipitated carbides contribute to improved wear resistance and stable hardness at operating temperatures up to 500 ℃.
The structure of the conventional smelting high-speed steel can realize the performances, but due to the limitation of the cooling speed, the higher carbon content and alloy content in the steel bring problems, so that the macro segregation is serious, and coarse ledeburite eutectic structures are easy to form among dendrites. In order to improve the properties of high-speed steel, the microstructure must be refined, and some degree of hot working is required. However, the primary carbides in the traditional as-cast structure are in coarse net distribution, and the serious coarse primary carbide segregation is difficult to eliminate through subsequent hot forging or hot rolling, so that the wear resistance, the ductility, the toughness and the cutting performance of the cutter are seriously influenced. Although the powder metallurgy process can better overcome the defects of the traditional smelting process, the structure of the high-speed steel is refined and uniform, the process is complex, the working procedure is complicated, and the manufacturing cost is greatly increased.
The spray forming technology is a high and new technology for preparing massive compact metal materials by using a rapid solidification method, has the advantages of semi-solid forming, near-net-shape forming, rapid solidification forming and the like, and effectively combines atomization and deposition. In the spray forming process, the alloy melt is broken under the impact action of high-speed high-pressure inert gas when flowing out of the guide pipe, the alloy melt is atomized to form dispersed small droplets of 10-200 mu m, the small droplets are subjected to strong heat exchange with surrounding gas in the high-speed flight process, overheating and crystallization latent heat are rapidly released and deposited on a substrate, and the alloy cooling speed is 102～104K/s. The faster the cooling rate, the smaller the degree of alloy segregation, grain size and carbide size. The high cooling speed in the atomization process enables the structure to be greatly refined, and the special deposition process enables dendrites formed in the semi-solid particles to be broken and remelted and finally become isometric crystals, so that the uniformity of the structure is improved. Therefore, the spray forming material has the characteristics of uniform, fine and equiaxial grain structure and the like, and avoids the macrosegregation of alloying elements. Compared with the traditional smelting high-speed steel, the spray forming high-speed steel has fine structure, higher toughness and better hot workability; compared with powder metallurgy high-speed steel, the spray forming high-speed steel can obtain a refined structure equivalent to the spray forming high-speed steel, reduces working procedures and reduces cost.
The special process advantages (such as high cooling speed, macro segregation inhibition, structure refinement, solid solubility improvement and the like) of the jet deposition have great application potential in the preparation of high alloy steel, and the toughness of the material can be greatly improved. The spray deposition state structure consists of fine and uniform isometric crystals, and grain boundary carbide particles are fine in size and are distributed in a dispersion mode. At present, spray forming has been widely and effectively applied to the preparation of copper alloy, aluminum alloy, magnesium alloy, titanium alloy, high-temperature alloy, steel and composite material, but is still unsatisfactory in the aspect of manufacturing high-carbon high-alloy high-speed steel, and most of spray-deposited high-speed steel products at home and abroad have the following two serious quality defects:
(a) the segregation of coarse carbide ring belts with uncontrollable positions occurs after forging, so that the material structure is seriously uneven, stress concentration is easy to generate, and the brittleness is increased;
(b) after quenching and three tempering treatments, the hardness is gradually reduced, and secondary hardening is avoided, so that the hardness, the wear resistance and the service life of the material are low.
The two problems seriously hinder the application and development of the spray deposition high-speed steel, and in order to meet the use requirement of the high-performance high-speed steel, the special design of the chemical components of the novel spray forming high-speed steel and the manufacturing process thereof are urgently needed, and the two technical problems are solved at the same time.
Disclosure of Invention
The invention aims to provide a jet high-speed steel without annular segregation and with secondary hardening and a manufacturing method thereof, and provides a jet-deposited high-vanadium niobium-containing wear-resistant high-speed steel and a preparation technology thereof, wherein the specific technical scheme is as follows:
the invention provides a jet high-speed steel without annular segregation and with secondary hardening, which comprises the following components in percentage by mass: carbon: 0.80-2.00%, tungsten: 0.00-9.00%, molybdenum: 1.00-9.00%, chromium: 4.00-6.00%, vanadium: 3.00 to 10.00%, niobium: 0.50 to 3.00%, silicon: 0.20 to 0.35%, manganese: 0.50-0.90%, sulfur: less than or equal to 0.040%, phosphorus: less than or equal to 0.040%, oxygen: 0.005-0.015%, nitrogen: 0.030 to 0.040%, and the balance of iron and inevitable impurities, wherein the main metal element components are all mixed according to an alloy form except iron.
The invention is further improved in that: the alloy is in the form of one or more of ferrotungsten, ferromolybdenum, ferrochromium, ferrovanadium and ferroniobium.
The invention also provides a jet high-speed steel without annular segregation and with secondary hardening and a manufacturing method thereof: the process comprises the following steps:
the method comprises the following steps: preparing a smelting raw material according to the components;
step two: intermediate frequency induction smelting:
(1) smelting in an induction furnace, selecting high-purity fused corundum as a ramming material of the induction furnace, enabling a tilting angle of a crucible to be-15-105 degrees, sequentially adding industrial pure iron, ferrotungsten and ferromolybdenum, adding a silicon-calcium line/calcium line after furnace burden is fully melted to be molten, carrying out slagging, deoxidation and inclusion removal, carrying out deslagging for 2-3 times, then sequentially adding ferrochromium, ferrovanadium, graphite and ferroniobium, and carrying out final deoxidation half an hour before discharging; chromium, vanadium and other alloy elements are added in the later stage of melting, pre-deoxidation is carried out before ferrochrome and ferrovanadium are added, ferroniobium is added finally, the high-temperature retention time is reduced as much as possible after the addition, final deoxidation is carried out half an hour before discharging, and the frequency is reduced slightly at the same time, so that the electromagnetic stirring effect in the induction furnace is reduced, the sedation is facilitated, the floating removal of inclusions is promoted, and the falling off of a furnace lining due to strong scouring and corrosion is avoided;
(2) determining and controlling the smelting temperature, the tapping temperature and the atomizing temperature according to the melting point of the alloy;
(3) pouring molten steel from a smelting furnace into a tundish which is pre-gas/electric heated;
step three: atomized spray deposition
(1) Preparing a spray ingot in 4-ton spray forming equipment by adopting a main and auxiliary two-stage annular non-limiting double-nozzle double-scanning nitrogen atomization deposition system;
(2) molten steel slowly flows into the tundish from the water outlet channel of the induction furnace at a constant speed, so that the quantity of the molten steel in the tundish flowing into the induction furnace is equal to that of the molten steel flowing out of the flow guide pipe, and the liquid level of the tundish is ensured to be equal to the height of the liquid level all the time; meanwhile, the overheating temperature of the molten alloy in the tundish is selected to be between 100 and 180 ℃, and the molten steel in the tundish is kept isothermal all the time;
(3) the molten steel flows out through a draft tube at the bottom of the tundish, is atomized into molten alloy fine droplets by high-pressure nitrogen from an atomizing nozzle, and is sprayed on a rotary alumina ceramic base plate which is 450-500 mm away from an atomizer;
step four: forging
Carrying out free forging on the spray deposition ingot at the temperature of 1150-950 ℃ in a forging ratio of 4: 1;
step five: thermal treatment
(1) Placing the forged jet high-speed steel in a horizontal annealing furnace for annealing, heating to 800-900 ℃ for 30-60 min, slowly cooling to 500-600 ℃ along with the furnace, taking out of the furnace, and air cooling to room temperature;
(2) and performing oil quenching on the annealed jet high-speed steel or placing the annealed jet high-speed steel in a calcium salt bath furnace for heating and quenching, cleaning a quenched part, placing the quenched part in a box furnace or a nitrate salt bath furnace for tempering, taking the tempered part out of the furnace, performing air cooling to room temperature, and greatly reducing the content of residual austenite by adopting a heat treatment process of quenching at 1110-1180 ℃ for 10min and tempering at 540-560 ℃ for 60min for three times.
The invention is further improved in that: in the second step, the rated steel loading amount is 4 tons, a 4-ton intermediate frequency furnace is adopted for induction heating smelting, the melting temperature is 1400-plus-1600 ℃, the superheat degree is 100-plus-180 ℃, the molten steel is properly kept warm after being melted down, and the molten steel is poured into a preheating tundish after deslagging.
The invention is further improved in that: spraying the mixture on a rotary alumina ceramic substrate which is 450-500 mm away from the atomizer in the third step, and preheating the mixture to 200-400 ℃.
The invention is further improved in that: and in the third step, a main secondary annular hole type non-limiting nozzle and an auxiliary secondary annular hole type non-limiting nozzle are adopted, the N nitrogen atomization pressure is 1-4 MPa, and the deposition distance is 450-500 mm.
The invention is further improved in that: the main process parameters of the used spray deposition are as follows: superheat temperature: 100-180 ℃; diameter of the flow guide pipe: 6.0-7.0 mm; nozzle exit diameter: 1.0-2.0 mm; nozzle scanning angle: +/-5.0-7.0 degrees; nozzle scanning frequency: 15-17 Hz; preheating temperature of the basal disc: 200-400 ℃; rotating speed of the base plate: 1.8-2.0 r/s; atomization pressure: 1-4 MPa; jet distance: 450-500 mm; nitrogen/melt: 0.3 to 0.5m3/Kg。
The invention is further improved in that: and step four, hot forging the deposited sprayed steel, heating to 1150-1170 ℃, and keeping the temperature for 30min, wherein the forging temperature is 1120-1150 ℃, and the final forging temperature is not lower than 950 ℃.
The invention is further improved in that: and in the fourth step, the spray forged steel is subjected to heat treatment, heated to 800-900 ℃ for 30-60 min for annealing, then the annealed spray forged steel is heated to 1110-1180 ℃ for 10min for quenching, and immediately tempered for three times at 540-560 ℃ for 60 min.
The invention has the beneficial effects that:
1. the spray deposition of low vanadium tungsten molybdenum high speed steel (for example, tungsten and molybdenum total content is 9%) can form coarse primary carbide M due to existence of a certain content of tungsten and molybdenum2C or M6C, causing carbide ring segregation with different bandwidths, as shown in figures 1-2;
2. the high-vanadium high-speed steel (such as vanadium content of more than 5%) is sprayed and deposited, because vanadium forms fine pre-eutectic carbide MC, eutectic carbide M is inhibited2C or M6C is precipitated and grown to eliminate the ring segregation of carbide. However, after quenching, the hardness of the jet high-speed steel is gradually reduced along with the increase of the tempering times, the abrasive wear resistance is also reduced along with the hardness, and the secondary hardening phenomenon does not occur. The high-speed steel with high vanadium content deposited by spraying has higher tendency of forming the prior eutectic carbide vanadium carbide in the solidification period, the vanadium carbide can be separated out in large quantity, is not easy to dissolve in quenching heating, reduces the carbon content in solid solution after austenitizing, causes insufficient carbon content in the solid solution, reduces the separation of secondary precipitated carbide, causes the reduction of secondary hardening capacity, and ensures that the hardness of the steel after quenching and tempering is lower than the hardness of the steel after quenching and tempering at first;
3. compared with vanadium, niobium has stronger affinity with carbon, so that the niobium-containing high-speed steel is easier to replace V to form MC type pre-eutectic carbide, VC is inhibited, NbC is preferentially separated out, more V is dissolved into a matrix, the matrix has enough carbon and vanadium contents, secondary precipitation of carbide is facilitated, and secondary hardening is promoted.
According to the analysis, vanadium is the most carbide-forming element in high-speed steel, part of vanadium is dissolved in the matrix, part of vanadium forms MC carbide, and eutectic carbide M is inhibited2C or M6The precipitation and growth of C avoid the annular segregation of coarse carbide. Niobium is also an element strongly promoting the formation of MC phase in high-speed steel, and on one hand, Nb is mainly used for replacing V and is dissolved in MC type carbide, so that V-rich MC type carbide in high-speed steel is converted into V-Nb composite MC carbideMore V is dissolved in the matrix in a solid mode, and the secondary hardening capacity of the material is improved; on the other hand, NbC is precipitated at a high temperature and is precipitated from the melt before eutectic reaction. As the spray deposition process is used as a rapid solidification technology, the growth of primary carbides can be well inhibited, so that the advantageous effect of Nb can be effectively exerted. Of course, the content of niobium should not be too high. Otherwise, niobium carbide is too coarse and deteriorates the mechanical properties of the material. Since Nb does not participate in secondary hardening, a certain V content must be secured. Therefore, by using an appropriate amount of Nb, the hardness, wear resistance and thermal stability of the high-speed steel can be improved without lowering the secondary hardening performance.
Drawings
FIG. 1 is a macroscopic cross-sectional morphology of a conventional as-forged and as-annealed ingot, with a distinct annular segregation band visible.
FIG. 2 shows the microstructure of the inner portion of a conventional as-forged and as-annealed ingot with larger carbide grain size in the annular segregation zone.
FIG. 3 shows the microstructure of the quenched and tempered spray ingot of the present invention, which has no ring segregation and fine and uniform carbide particles.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention.
Example 1
The embodiment provides a jet high-speed steel without annular segregation and with secondary hardening, which comprises the following components in percentage by mass: carbon: 1.70%, molybdenum: 3.00%, chromium: 6.00%, vanadium: 8.00%, niobium: 2.50%, silicon: 0.20 to 0.35%, manganese: 0.50-0.90%, sulfur: less than or equal to 0.040%, phosphorus: less than or equal to 0.040%, oxygen: 0.005-0.015%, nitrogen: 0.030-0.040%, and the balance of iron and inevitable impurities, wherein the main metal element components except iron are all mixed according to an alloy form, and the alloy form is one or more of ferromolybdenum, ferrochromium, ferrovanadium and ferroniobium.
The process comprises the following steps:
the method comprises the following steps: preparing a smelting raw material according to the components;
step two: intermediate frequency induction smelting:
(1) induction heating and smelting in a 4-ton intermediate frequency furnace, wherein the tilting angle of a crucible is-15-105 degrees, sequentially adding industrial pure iron and ferromolybdenum, adding a silicon-calcium wire after furnace charges are fully melted to be molten, carrying out slagging, deoxidation and impurity removal, carrying out slag removal for 2-3 times, and then sequentially adding ferrochromium, ferrovanadium and graphite. Alloy elements such as chromium, vanadium and the like are required to be added in the later stage of melting, pre-deoxidation is carried out before ferrochrome and ferrovanadium are added, ferroniobium is added finally, the high-temperature retention time is reduced as much as possible after the addition, final deoxidation is carried out half an hour before discharging, and meanwhile, the frequency is slightly reduced so as to reduce the electromagnetic stirring effect in the induction furnace, facilitate the sedation, promote the removal of inclusions and prevent the falling of a furnace lining;
(2) the smelting melting temperature is 1560-1580 ℃, and the tapping temperature is 1560 ℃;
(3) pouring molten steel from a smelting furnace into a tundish which is heated by pre-gas;
step three: atomized spray deposition
(1) Preparing a spray ingot in 4-ton spray forming equipment by adopting a main and auxiliary two-stage annular non-limiting double-nozzle double-scanning nitrogen atomization deposition system;
(2) molten steel slowly flows into the tundish from the water outlet channel of the induction furnace at a constant speed, so that the quantity of the molten steel in the tundish flowing into the induction furnace is equal to that of the molten steel flowing out of the flow guide pipe, and the liquid level of the tundish is ensured to be equal to the height of the liquid level all the time; the overheating temperature is 160 ℃, the temperature of the molten alloy in the tundish is 1500 ℃, and the constant temperature of the molten steel in the tundish is maintained all the time;
(3) molten steel flows out through a draft tube at the bottom of the tundish, is atomized into molten alloy fine droplets by high-pressure nitrogen from an atomizing nozzle, and is sprayed on a rotary ceramic deposition disc which is 450-500 mm away from an atomizer, the ceramic disc is preheated to 200-400 ℃ by gas heating, and the atomizing and spraying temperature is kept at 1500 ℃ all the time;
in a double-nozzle double-scanning atomization injection system, the diameter of a steel nozzle outlet is 1.0mm, the diameter of a guide pipe is 6.0mm, the atomization pressure of nitrogen is 2.5MPa, the deposition distance is 450-500 mm, atomized supercooled liquid drops are sprayed and deposited on a rotary alumina receiving base plate, and are directly solidified to form a high-density columnar deposition ingot with the diameter of 480mm and the height of 1800mm, and the relative density of the columnar deposition ingot is as high as 99.5% of the theoretical density. The yield of the deposited ingot is about 87 percent, the shape is complete, the surface has no macroscopic defects, the internal structure consists of uniform and fine isometric crystals, and the grain size is about 15 mu m.
Step four: forging
And (3) carrying out hot forging on the deposition-state spray ingot, keeping the temperature at 1140 ℃ for 30min, and keeping the forging temperature at 1120 ℃ and the final forging temperature at not lower than 950 ℃. Free forging was used at a 4: 1 forging ratio to eliminate micro-porosity and voids and to increase the relative density to 100% of theoretical density.
Step five: thermal treatment
(1) And immediately returning and heating to 800-900 ℃ for 30-60 min after forging, annealing, slowly cooling to 500-600 ℃ along with the furnace, discharging, and air cooling to room temperature.
The internal structure of the annealed spray-forged high-speed steel does not have a micro-porous pore and a coarse carbide annular segregation zone, the alloy elements do not have macrosegregation, the structure is fine and uniform, the carbide particles are fine in size, regular in shape and uniform in distribution;
(2) and (3) oil quenching the annealed spray-forged high-speed steel, immediately tempering, discharging from the furnace, air cooling to room temperature, and adopting a heat treatment system of quenching at 1120 ℃ for three times, namely 10min and tempering at 550 ℃ for three times, so as to reduce the content of the residual austenite.
The structure of the quenched and tempered spray-forged high-speed steel consists of tempered martensite, residual austenite and alloy carbide, the grains are uniform and fine, and the carbide is uniformly and dispersedly distributed (less than 4 mu m). The hardness of the spray-forged steel after quenching is 62-64 HRC, secondary hardening occurs during tempering, and the tempering hardness is increased to 64-66 HRC.
In the jet-deposited high-vanadium niobium-containing wear-resistant high-speed steel without carbide annular segregation and with secondary hardening, the addition of niobium enables NbC preferentially precipitated to inhibit a part of VC eutectic carbide which is not easy to dissolve from being precipitated, increases the contents of carbon and vanadium in solid solution after austenitizing, and ensures the contents of carbon and vanadium required by secondary hardening to be enough. If the steel is free of niobium, there is no secondary hardening effect; high vanadium addition, sufficient amount of precipitated VC inhibits M2C or M6C, precipitation and growth of eutectic carbide, and elimination of annular segregation of carbide; because a large amount of primary MC type carbide (with the size of 2-4 mu m) precipitated by grain boundaries and high-hardness secondary carbide hard particles (with the size of less than 1 mu m) precipitated in the grains are finer in size and are distributed in a dispersing way, the jet high-speed steel has high wear resistance; the rapid solidification ensures that the carbide has good shape and uniform distribution, and improves the impact toughness of the sprayed high-speed steel.
Example 2
The embodiment provides a jet high-speed steel without annular segregation and with secondary hardening and a manufacturing method thereof, wherein the jet high-speed steel comprises the following components in percentage by mass: carbon: 1.80%, tungsten: 6.00%, molybdenum: 5.00%, chromium: 4.00%, vanadium: 6.00%, niobium: 2.00%, silicon: 0.20 to 0.35%, manganese: 0.50-0.90%, sulfur: less than or equal to 0.040%, phosphorus: less than or equal to 0.040%, oxygen: 0.005-0.015%, nitrogen: 0.030-0.040%, and the balance of iron and inevitable impurities, wherein the main metal element components except iron are all mixed according to an alloy form, and the alloy form is one or more of ferrotungsten, ferromolybdenum, ferrochromium, ferrovanadium and ferroniobium.
The process comprises the following steps:
the method comprises the following steps: preparing a smelting raw material according to the components;
step two: intermediate frequency induction smelting:
(1) induction heating and smelting in a 4-ton intermediate frequency furnace, wherein the tilting angle of a crucible is-15-105 degrees, sequentially adding industrial pure iron, ferrotungsten and ferromolybdenum until furnace burden is fully melted to be clear, adding calcium wires, carrying out slagging, deoxidation and inclusion removal, carrying out slag removal for 2-3 times, and then sequentially adding ferrochrome, ferrovanadium and graphite. Alloy elements such as chromium, vanadium and the like are required to be added in the later stage of melting, pre-deoxidation is carried out before ferrochrome and ferrovanadium are added, ferroniobium is added finally, the high-temperature retention time is reduced as much as possible after the addition, final deoxidation is carried out half an hour before discharging, and meanwhile, the frequency is slightly reduced so as to reduce the electromagnetic stirring effect in the induction furnace, facilitate the sedation, promote the removal of inclusions and prevent the falling of a furnace lining;
(2) the smelting melting temperature is 1500-1510 ℃, and the tapping temperature is 1500 ℃;
(3) pouring molten steel from a smelting furnace into a tundish which is heated by pre-gas;
step three: atomized spray deposition
(1) Preparing a spray ingot in 4-ton spray forming equipment by adopting a main and auxiliary two-stage annular non-limiting double-nozzle double-scanning nitrogen atomization deposition system;
(2) molten steel slowly flows into the tundish from the water outlet channel of the induction furnace at a constant speed, so that the quantity of the molten steel in the tundish flowing into the induction furnace is equal to that of the molten steel flowing out of the flow guide pipe, and the liquid level of the tundish is ensured to be equal to the height of the liquid level all the time; the overheating temperature is selected to be 150 ℃, the temperature of the molten alloy in the tundish is 1450 ℃, and the constant temperature of the molten steel in the tundish is maintained all the time;
(3) the molten steel flows out through a draft tube at the bottom of the tundish, is atomized into molten alloy fine droplets by high-pressure nitrogen from an atomizing nozzle, and is sprayed on a rotary ceramic deposition disc (preheated to 200-400 ℃ through gas heating) which is 450-500 mm away from an atomizer, wherein the atomizing spraying temperature is always kept at 1450 ℃;
in a double-nozzle double-scanning atomization injection system, the diameter of a nozzle outlet is 1.2mm, the diameter of a guide pipe is 6.5mm, the atomization pressure of nitrogen is 1.8MPa, the deposition distance is 450-500 mm, atomized supercooled liquid drops are sprayed and deposited on a rotary alumina receiving base plate, and are directly solidified to form a high-density columnar deposition ingot with the diameter of 500mm and the height of 2000mm, and the relative density of the high-density columnar deposition ingot is up to 99.7% of the theoretical density. The yield of the deposited ingot is about 85 percent, the shape is complete, the surface has no macroscopic defects, the internal structure consists of uniform and fine isometric crystals, and the grain size is about 20 mu m.
Step four: forging
And (3) carrying out hot forging on the deposition-state spray ingot, keeping the temperature at 1170 ℃ for 30min, and keeping the forging temperature at 1150 ℃ and the final forging temperature at not lower than 950 ℃. Free forging was used at a 4: 1 forging ratio to eliminate micro-porosity and voids and to increase the relative density to 100% of theoretical density.
Step five: thermal treatment
(1) And immediately returning and heating to 800-900 ℃ for 30-60 min after forging, annealing, slowly cooling to 500-600 ℃ along with the furnace, discharging, and air cooling to room temperature.
Metallographic and scanning electron microscope analysis shows that the internal structure of the annealed spray-forged high-speed steel has no loose pore distribution and no large carbide annular segregation zone, the alloy elements have no macrosegregation, the structure is fine and uniform, the carbide particles are fine in size, the shape is regular, and the distribution is uniform;
(2) and performing oil quenching on the annealed spray-forged high-speed steel or placing the annealed spray-forged high-speed steel in a calcium salt bath furnace containing a deoxidizer for heating and quenching, cleaning a quenched part, placing the quenched part in a box furnace or a nitrate salt bath furnace for tempering, discharging the tempered part out of the furnace, cooling the tempered part to room temperature, and reducing the residual austenite to a very low level by adopting a heat treatment process of three tempering at 1150 ℃ multiplied by 10min and 560 ℃ multiplied by 60 min.
The structure of the quenched and tempered spray-forged high-speed steel consists of tempered martensite, residual austenite and alloy carbide, the grains are uniform and fine, and the carbide is uniformly and dispersedly distributed (less than 5 mu m), which is shown in figure 3. The hardness of the spray-forged steel after quenching is 64-66 HRC, an obvious secondary hardening effect is generated during tempering, the tempering hardness is increased to 66-69 HRC, the hardness of 59HRC can be still maintained during tempering at 650 ℃, and the thermal stability of the structure is better. This is because the spray deposition rapid solidification causes a high content of alloy elements dissolved in the matrix and a high amount of carbides dissolved in austenite during quenching heating, and alloy elements such as C, W, Mo, Cr, V, etc. dissolved in the quenched matrix delay the precipitation of fine secondary carbides at a high temperature and inhibit the growth of secondary precipitated carbides due to a large amount of nucleation.
The spray-deposited high-vanadium niobium-containing wear-resistant high-speed steel without carbide annular segregation and with secondary hardening can effectively eliminate macro-segregation, refine the structure, increase the initial precipitation temperature of MC type pre-eutectic carbide by adding Nb, and precipitate a large amount of Nb-rich MC type carbide phase before eutectic reaction, and has small size and uniform distribution along the grain boundary. A large amount of C is consumed by the precipitation of a large amount of MC phase, the contents of C and alloy elements in the residual liquid phase are reduced, the eutectic reaction is inhibited, and M2C、M6The number of the C sheet layers is reduced, the thickness of the C sheet layers is thinned, decomposition is generated in the hot forging process, and the tissue uniformity is improved. As more alloying elements are dissolved in the spray-forged high-speed steel during quenching, the speed of the hardness rising along with the temperature is higher during the tempering process, and the peak hardness value is 69 HRC. Therefore, the spray forging after the heat treatment is highThe steel has no carbide ring segregation and promotes secondary hardening.
Because of the dispersed and distributed niobium and vanadium-containing MC type primary carbides, the abrasive wear resistance of the high-speed steel under low temperature and low load can be greatly improved; the precipitated secondary carbide which is dispersed and distributed has strong agglomeration resistance, slows down the reduction speed of high-temperature hardness, and can effectively improve the oxidation wear resistance of the high-speed steel at the high temperature of 500 ℃ and under high load, so the spray-forged high-speed steel after heat treatment can greatly improve the wear resistance, has better toughness, and can be used as a cutter and a high-wear-resistant part (such as a roller, a roller ring, a lining plate and the like).
The jet deposited high speed steel without carbide annular deviation and with secondary hardening can be further optimized according to different practical applications:
(1) according to the requirement of high wear resistance of a working condition, the number of MC type carbides is increased, the vanadium-carbon content is increased and the vanadium-carbon ratio is adjusted, the limit of carbon-vanadium content in the traditional smelting high-speed steel is broken through, and the high-carbon and high-vanadium steel is developed towards the direction of high carbon and high vanadium (such as V & gt 5% wt);
(2) different matrix structures are obtained through heat treatment to meet the service performance under different working conditions: for general abrasive wear, a martensite or bainite matrix may be chosen; for wear resistant parts subjected to high impacts or high temperatures, an austenitic matrix may be chosen.
Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing detailed description, or equivalent changes may be made in some of the features of the embodiments described above. All equivalent structures made by using the contents of the specification and the attached drawings of the invention can be directly or indirectly applied to other related technical fields, and are also within the protection scope of the patent of the invention.
Claims (9)
1. A jet high-speed steel without annular segregation and having secondary hardening is characterized in that: the components of the material comprise the following components in percentage by mass: carbon: 0.80-2.00%, tungsten: 0.00-9.00%, molybdenum: 1.00-9.00%, chromium: 4.00-6.00%, vanadium: 3.00 to 10.00%, niobium: 0.50 to 3.00%, silicon: 0.20 to 0.35%, manganese: 0.50-0.90%, sulfur: less than or equal to 0.040%, phosphorus: less than or equal to 0.040%, oxygen: 0.005-0.015%, nitrogen: 0.030 to 0.040%, and the balance of iron and inevitable impurities, wherein the main metal element components are all mixed according to an alloy form except iron.
2. The steel according to claim 1, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening property, and the steel is characterized in that: the alloy is in the form of one or more of ferrotungsten, ferromolybdenum, ferrochromium, ferrovanadium and ferroniobium.
3. The steel for jet high speed without annular segregation and having secondary hardening according to any of claims 1 to 2, characterized in that: the process comprises the following steps:
the method comprises the following steps: preparing a smelting raw material according to the components;
step two: intermediate frequency induction smelting:
(1) smelting in an induction furnace, selecting high-purity fused corundum as a ramming material of the induction furnace, enabling a tilting angle of a crucible to be-15-105 degrees, sequentially adding industrial pure iron, ferrotungsten and ferromolybdenum, adding a silicon-calcium line/calcium line after furnace burden is fully melted to be molten, carrying out slagging, deoxidation and inclusion removal, carrying out deslagging for 2-3 times, then sequentially adding ferrochromium, ferrovanadium, graphite and ferroniobium, and carrying out final deoxidation half an hour before discharging;
(2) determining and controlling the smelting temperature and the tapping temperature according to the melting point of the alloy;
(3) pouring molten steel from a smelting furnace into a tundish which is preheated by gas/electricity;
step three: atomized spray deposition
(1) Preparing a spray ingot in 4-ton spray forming equipment by adopting a main and auxiliary two-stage annular non-limiting double-nozzle double-scanning nitrogen atomization deposition system;
(2) molten steel slowly flows into the tundish from the water outlet channel of the induction furnace at a constant speed, so that the quantity of the molten steel in the tundish flowing into the induction furnace is equal to that of the molten steel flowing out of the flow guide pipe, and the liquid level of the tundish is ensured to be equal to the height of the liquid level all the time; meanwhile, the overheating temperature of the molten alloy in the tundish is selected to be between 100 and 180 ℃, and the molten steel in the tundish is kept isothermal all the time;
(3) the molten steel flows out through a flow guide pipe at the bottom of the tundish, is atomized into molten alloy fine droplets by high-pressure nitrogen from an atomizing nozzle, and is sprayed on a rotary ceramic deposition disc which is 450-500 mm away from an atomizer (preheated to 200-400 ℃ by gas/electricity), wherein the atomizing and spraying temperature is required to be the temperature of an alloy liquid phase line plus the superheat degree;
step four: forging
Carrying out free forging on the spray deposition ingot at the temperature of 1150-950 ℃ in a forging ratio of 4: 1 to eliminate micro-porosity and pores;
step five: thermal treatment
(1) Placing the forged jet high-speed steel in a horizontal annealing furnace for annealing, heating to 800-900 ℃ for 30-60 min, slowly cooling to 500-600 ℃ along with the furnace, taking out of the furnace, and air cooling to room temperature;
(2) and carrying out oil quenching on the annealed jet high-speed steel or placing the annealed jet high-speed steel in a calcium salt bath furnace containing a deoxidizer for heating and quenching, cleaning a quenched part, placing the quenched part in a box furnace or a nitrate salt bath furnace for tempering, then discharging the tempered part from the furnace and air cooling the tempered part to room temperature, and reducing the residual austenite to a very low level by adopting a heat treatment process of three tempering at 1110-1180 ℃ for 10min and 540-560 ℃ for 60 min.
4. The steel according to claim 3, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening effect, and the method comprises: in the second step, the rated steel loading is 4 tons, a 4-ton intermediate frequency furnace is adopted for induction heating smelting, the molten steel is properly kept warm after being melted down, and the molten steel is poured into a tundish which is pre-gas/electric heated after deslagging.
5. The steel according to claim 3, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening effect, and the method comprises: in the third step, the mixture is sprayed on a rotary alumina ceramic disc which is 450-500 mm away from the atomizer and is preheated to 200-400 ℃ by gas/electric heating.
6. The steel according to claim 3, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening effect, and the method comprises: and in the third step, a main secondary annular hole type non-limiting nozzle and an auxiliary secondary annular hole type non-limiting nozzle are adopted, the nitrogen atomization pressure is 1-4 MPa, and the deposition distance is 450-500 mm.
7. The steel according to claim 6, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening effect, and the method comprises: the main process parameters of the used spray deposition are as follows: superheat temperature: 100-180 ℃; diameter of the flow guide pipe: 6.0-7.0 mm; nozzle exit diameter: 1.0-2.0 mm; nozzle scanning angle: +/-5.0-7.0 degrees; nozzle scanning frequency: 15-17 Hz; preheating temperature of a deposition disc: 200-400 ℃; rotating speed of the deposition disc: 1.8-2.0 r/s; atomization pressure: 1-4 MPa; jet distance: 450-500 mm; nitrogen/melt: 0.3 to 0.5m3/Kg。
8. The steel according to claim 3, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening effect, and the method comprises: the hot forging process of the deposition-state spray ingot in the fourth step comprises the following steps: keeping the temperature of 1150-1170 ℃ for 30min, wherein the forging starting temperature is 1120-1150 ℃, the final forging temperature is not lower than 950 ℃, and the forging ratio is 4: 1.
9. The steel according to claim 3, wherein the steel is a jet high-speed steel having no annular segregation and having a secondary hardening effect, and the method comprises: the heat treatment process of the spray forged steel in the fourth step comprises the following steps: annealing: heating to 800-900 ℃ for 30-60 min, slowly cooling to 500-600 ℃ along with the furnace, discharging, and air cooling to room temperature; quenching and tempering: heating to 1110-1180 ℃ for 10min quenching and 540-560 ℃ for 60min three times of high-temperature tempering.
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