CN113235019A - Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar and preparation method thereof - Google Patents
Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar and preparation method thereof Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- 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
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- 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
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
- C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C33/00—Making ferrous alloys
- C22C33/04—Making ferrous alloys by melting
- C22C33/06—Making ferrous alloys by melting using master alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
Abstract
The invention belongs to the technical field of metallurgy, and particularly relates to a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar and a preparation method thereof. The invention aims to solve the technical problem of providing a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar which comprises the following chemical mass percent: 0.3-0.6% of C, 18.0-22.0% of Mn, 5.0-10.0% of Ni, 2.0-6.0% of Al, 5.0-10.0% of Cr, 0.01-0.5% of S, 0.35-0.65% of N, P being less than or equal to 0.01%, and the balance of Fe and inevitable impurities. The invention also provides a preparation method of the steel. The steel has the advantages of easy cutting, low density and the like, and can be well applied to the field of automobiles.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and particularly relates to a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar and a preparation method thereof.
Background
In recent years, the economy and science and technology of China are rapidly developed, the living standard of people is obviously improved, and automobiles become one of the necessities of modern life and are integrated into various aspects of life. However, the content of PM2.5 in the atmosphere is seriously exceeded due to pollutants such as carbon monoxide, nitric oxide and hydrocarbon emitted by automobile exhaust, the quality of the air environment is affected, and physical and psychological health of citizens is directly harmed. According to scientific research, the fuel consumption of an automobile can be reduced by 6 to 8 percent and the exhaust emission can be reduced by 5 to 6 percent when the dead weight of the automobile is reduced by 10 percent; when the consumption of 1L fuel oil is reduced, 2.45kg of carbon dioxide is less discharged, and the pollution of automobile exhaust to the environment can be effectively reduced. Therefore, the light weight of the automobile can effectively relieve the increasingly serious problem of environmental pollution. In the last 30 years, Ton and Korter firstly proposed the concept of low-density steel, and the concept of Fe-Mn-Al series low-density steel is formed by adding manganese and aluminum elements with lower relative molecular mass into iron, and a phase diagram after quenching is made. Ham et Al developed inexpensive Fe-34Mn-10Al-0.76C austenitic low density steel in 1958, the tensile strength of which reached 750 MPa. The newly developed austenitic low-density steel has excellent corrosion resistance and oxidation resistance, and owing to the cost advantage of the low-density steel, Ham et Al propose the use of inexpensive Fe-Mn-Al based low-density steel instead of expensive Cr-Ni stainless steel, which has been the subject of intense research in the automotive industry and steel industry in the last 50 th century.
The free-cutting steel is alloy steel which is added with a certain amount of one or more free-cutting elements such as sulfur, phosphorus, lead, calcium, selenium, tellurium and the like to improve the cutting performance. The chalcogenide free-cutting steel is the free-cutting steel which is the earliest in appearance time, has the largest use amount and the widest application so far, and accounts for more than 70 percent and 90 percent of the total production of free-cutting steel in the world and China respectively. The chalcogenide free-cutting steel is mainly applied to complex parts such as bolts, nuts, pipe joints, automobile braking parts, spring seats, molds and the like, the complex parts need to be cut on a numerical control machine tool, and in order to prolong the service life of a cutter, reduce the processing cost and improve the production efficiency, the steel is required to have good cutting processing performance. The sulfur in the free-cutting steel mainly exists in the form of manganese sulfide, and manganese sulfide inclusions can be used as a stress concentration source to induce a matrix to generate a plurality of micro-cracks, so that the cutting resistance is reduced, the steel is easy to break chips during turning, and the cutting performance of the steel is improved.
Although the traditional low-density steel has lower density, the machinability of the traditional low-density steel cannot effectively form sulfide in a matrix because the traditional low-density steel does not contain higher S element, and the machinability of the steel cannot be improved. Therefore, the more potential development approaches for the light weight of the automobile are as follows: a steel grade integrating low density and easy-cutting performance is developed.
Disclosure of Invention
The invention aims to provide a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar with low density and good cutting performance and a preparation method thereof aiming at the defects of the prior art.
The invention provides a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar which comprises the following chemical mass percent: 0.3-0.6% of C, 18.0-22.0% of Mn, 5.0-10.0% of Ni, 2.0-6.0% of Al, 5.0-10.0% of Cr, 0.01-0.5% of S, 0.35-0.65% of N, P being less than or equal to 0.01%, and the balance of Fe and inevitable impurities.
Preferably, in the Fe-Mn-Al-N-S high-nitrogen low-density free-cutting steel bar, the mass percentage of Al is 3.0-5.0%.
Preferably, in the Fe-Mn-Al-N-S high-nitrogen low-density free-cutting steel bar, the S content is 0.1-0.3% by mass.
Preferably, in the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, the weight percentage of Mn and S satisfies that Mn/S is more than or equal to 140 and less than or equal to 200; the weight percentage of Al and Ni satisfies that the weight percentage of Al + Ni is more than or equal to 10 and less than or equal to 15.
The invention also provides a preparation method of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, which comprises the following steps: proportioning the components of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, smelting the raw materials, pouring to obtain a phi 200-250 mm ingot after smelting, heating the ingot at 1000-1200 ℃ for 30-60 min, forging to form a phi 100-120 mm bar, continuously heating at 1000-1200 ℃ for 20-30 min, taking out and forging to obtain a phi 60-65 mm bar, and air cooling to room temperature.
Further, the preparation method of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar comprises the following steps:
1) preparing materials: high-purity iron, high-sulfur pig iron, electrolytic manganese, a nickel plate, a pure aluminum block, chromium nitride and a carburant are used as raw materials, and ingredients are prepared according to the components of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar;
2) smelting in a vacuum furnace: adding high-purity iron and a nickel plate into a vacuum induction smelting furnace, closing the furnace, vacuumizing, powering to melt the high-purity iron and the nickel plate after the vacuum degree is 1-5 pa, heating to 1500-1510 ℃, flushing argon to 15000-20000 pa after the high-purity iron and the nickel plate are completely melted down, then adding high-sulfur pig iron, electrolytic manganese, a pure aluminum block, chromium nitride and a carburant, refining for 5-10 min after the alloy is completely melted down, and the refining temperature is 1510-1520 ℃; standing after refining is finished;
3) pouring: raising the temperature to 1530-1550 ℃, pouring molten steel into a metal mold with the diameter phi of 200-250 mm, and cooling the molten steel to room temperature to obtain an ingot;
4) forging: heating the ingot to 1000-1200 ℃ for 30-60 min, taking out the ingot, forging the ingot into a bar with the diameter of 100-120 mm, returning the bar to the furnace, continuously heating the bar with the heating temperature of 1000-1200 ℃ for 20-30 min, taking out the bar with the diameter of 60-65 mm, and air-cooling the bar to the room temperature.
In the preparation method of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, the recarburizing agent is artificial graphite, natural graphite or coke.
According to the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, a certain amount of light-weight elements such as Al, Mn and C are added into steel, a novel low-density steel grade can be obtained on the basis of optimizing alloy components, and the weight of an automobile can be effectively reduced on the premise of not sacrificing the strength and rigidity of an automobile structural part; by reasonably adding Mn and S elements into the steel, the appearance, size, length-width ratio and distribution of sulfides in the steel can be effectively controlled and improved, so that the steel has better cutting performance; by reasonably adding N, Ni austenitizing elements, the structure of the steel at room temperature can be stable austenite, so that the steel has good strong plasticity; the steel has very good mechanical properties by matching with a reasonable forging process. The free-cutting stainless steel with high strength and high cutting performance prepared by the invention is suitable for manufacturing parts in industries such as automobiles, high-speed rails, household appliances, office equipment and the like, can effectively reduce the machining cost, and improves the production efficiency and the competitiveness of products.
The invention has simple smelting and forging process, wide raw material source of steel and reduced production cost of high-nitrogen low-density free-cutting steel.
The Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar does not contain Pb, does not pollute the environment and accords with the development strategy of national energy conservation and emission reduction.
The Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar has good cutting performance, so that the application of the steel bar is wider.
The Fe-Mn-Al-N-S high-nitrogen low-density free-cutting steel bar has the tensile strength of more than or equal to 750MPa, the yield strength of more than or equal to 500MPa, the reduction of area of more than or equal to 20 percent, the elongation after fracture of more than or equal to 30 percent, the impact toughness of more than or equal to 20J and good strong plasticity.
The density of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar is less than or equal to 7.35g/cm3The density of the material is 7.8g/cm compared with that of the traditional material3Compared with the prior art, the weight loss effect is more than 5 percent, and the weight loss effect is very good.
The Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar can be applied to important fields of automobiles, high-speed rails, aerospace and the like, and has the advantages of low processing cost, obvious weight reduction effect and good application prospect.
Drawings
FIG. 1 is a phase diagram of 500 times of sulfide in high-nitrogen low-density free-cutting steel according to example 1 of the present invention
FIG. 2 is a phase diagram of 500 times of sulfide in high-nitrogen low-density free-cutting steel according to example 2 of the present invention
FIG. 3 is a stress-strain curve of a high-nitrogen low-density free-cutting steel according to example 1 of the present invention
FIG. 4 is a stress-strain curve of a high-nitrogen low-density free-cutting steel according to example 2 of the present invention
FIG. 5 is an SEM morphology of high-nitrogen low-density free-cutting steel in forged fracture of 1000 times in example 1 of the invention
FIG. 6 is an SEM morphology of high-nitrogen low-density free-cutting steel in forged fracture of 1000 times in example 2 of the invention
FIG. 7 shows chips of high-nitrogen low-density free-cutting steel at a rotation speed of 180r/min according to example 1 of the present invention
FIG. 8 is a cutting chip of high nitrogen low density free-cutting steel of example 2 of the present invention at a rotation speed of 180r/min
Detailed Description
The invention provides a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar which comprises the following chemical mass percent: 0.3-0.6% of C, 18.0-22.0% of Mn, 5.0-10.0% of Ni, 2.0-6.0% of Al, 5.0-10.0% of Cr, 0.01-0.5% of S, 0.35-0.65% of N, P being less than or equal to 0.01%, and the balance of Fe and inevitable impurities.
C: carbon is one of the important elements for improving the strength of steel. When the carbon content in the high-nitrogen low-density free-cutting steel is very low, the ferrite content of the steel is increased, the strength and the hardness of the steel are reduced, and cutting chips are easy to stick to a cutter due to the fact that the steel is too soft, and the cutting performance of the steel is reduced; on the other hand, when the carbon content in the steel is too high, the hardness thereof increases, which also causes wear of the tool and deteriorates the cutting performance of the steel. Therefore, the content of C in the invention is controlled to be 0.3-0.6%.
N: nitrogen is an element that forms and stabilizes austenite very strongly and expands the austenite phase region. Nitrogen can replace part of nickel, reduce the ferrite content in the steel, stabilize austenite, prevent the precipitation of harmful intermetallic phases and even avoid the martensitic transformation under cold working conditions. The nitrogen can improve the strength of the stainless steel obviously without reducing the plasticity and toughness of the material, and can also improve the creep resistance, fatigue resistance, abrasion resistance and yield strength of the steel. Therefore, the content of N in the invention is controlled to be 0.35-0.65%.
Mn: manganese is one of important elements for improving the cutting performance of steel, is easy to combine with sulfur to form manganese sulfide, and is the most important free-cutting phase in high-nitrogen low-density free-cutting steel. The notch effect of manganese sulfide can crack the continuity of the matrix, so that the stress in the cutting process can be released. Manganese sulfide has good plasticity in steel, can play a role in lubricating as a soft phase, reduces the abrasion of a cutter, and can form a layer of Belag film on the surface of the cutter during high-speed cutting, so that the service life of the cutter is prolonged by 3-9 times. Therefore, the Mn content is controlled to be 18.0-22.0 percent in the invention.
Al: solid solution of Al atoms causes the lattice expansion of the Fe matrix, and the density of the steel is reduced by 0.101g/cm per 1% of Al added3The weight can be reduced by about 1.3%. The addition of the alloying element Al lowers the average molar mass of the steel and increases the molar volume of the steel, thereby lowering the density of the steel. At room temperature, Al has higher solid solubility in pure Fe, and the solid solubility can be further increased in the presence of other elements such as C, Mn and the like. Al tends to be the main alloying element of light steel. The Al content of the invention is controlled to be 2.0-6.0%.
Ni: the nickel can improve the strength of the steel and also ensure that the steel has good plasticity and toughness. Statistically, the strength of the steel material can be improved by about 29.41MPa for every 1% increase of nickel, and the nickel can also improve the hardenability of the steel. The Ni content is controlled to be 5.0-10.0%.
S: sulfur is the most important free-cutting element in high-nitrogen low-density free-cutting steel, the sulfur is mainly distributed in a steel matrix in the form of sulfides, and the size, content, morphology and distribution of the sulfides directly influence the cutting performance of the steel. When the sulfur content is low, sulfide with enough content cannot be generated in the steel, and the requirement of high cutting performance cannot be met; on the contrary, when the sulfur content is high, the hot workability is deteriorated and segregation of sulfur element in the center of the ingot is easily caused. Therefore, the S content is controlled to be 0.01-0.5 percent in the invention.
P: phosphorus increases the strength and hardenability of steel, but too high a content thereof decreases the machinability of steel and causes a decrease in hot workability. Therefore, the P content in the present invention is controlled to 0.01% or less.
Cr: the main function of chromium in steel is to improve the corrosion resistance of free-cutting steel, and chromium element can also improve the hardenability of steel, so that the steel has better comprehensive mechanical properties after quenching and tempering; chromium improves the strength of the steel, and particularly has more remarkable effect when other alloy elements are added. Therefore, the Cr content is controlled to be 5.0-10.0 percent in the invention.
Furthermore, in the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, the mass percentage of Al is 3.0-5.0%.
Furthermore, in the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, the mass percentage of S is 0.1-0.3%.
Furthermore, in the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, the weight percentage of Mn and S meets the requirement that Mn/S is more than or equal to 140 and less than or equal to 200; the weight percentage of Al and Ni satisfies that the weight percentage of Al + Ni is more than or equal to 10 and less than or equal to 15.
The invention relates to a preparation method of a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, which comprises the following steps:
1) preparing materials: high-purity iron, high-sulfur pig iron, electrolytic manganese, a nickel plate, a pure aluminum block, chromium nitride and a carburant are used as raw materials, and ingredients are prepared according to the components of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar;
2) smelting in a vacuum furnace: adding high-purity iron and a nickel plate into a vacuum induction smelting furnace, closing the furnace, vacuumizing, powering to slowly melt the high-purity iron and the nickel plate after the vacuum degree is 1-5 pa, heating to 1500-1510 ℃, keeping for 10-20 min, flushing argon to 15000-20000 pa after the high-purity iron and the nickel plate are completely melted down, then adding high-sulfur pig iron, electrolytic manganese, a pure aluminum block, chromium nitride and a carburant, refining for 5-10 min after the alloy is completely melted down, wherein the refining temperature is 1510-1520 ℃; standing for 1-5 min after refining is finished;
3) pouring: increasing power, raising the temperature to 1530-1550 ℃, keeping the temperature for 5-15 min, pouring molten steel into a metal mold with the diameter of 200-250 mm and the length of 400-500 mm, solidifying the molten steel in the furnace, and cooling to room temperature to obtain an ingot of the high-nitrogen low-density free-cutting steel;
4) forging: cutting off a riser and a tail of an ingot before forging, then cutting the ingot into two sections at the middle part, then heating the ingot in a muffle furnace at the heating temperature of 1000-1200 ℃ for 30-60 min, taking out the ingot after heating and heat preservation, forging the ingot on forging equipment into a bar with the diameter of about phi 100-120 mm, then returning the bar to the furnace for heating at the heating temperature of 1000-1200 ℃ for 20-30 min, then taking out the bar with the diameter of 60-65 mm, forging the bar into a bar with the diameter of phi 60-65 mm, and air cooling the bar to room temperature to obtain the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar.
The raw materials and equipment used in the preparation method of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar can be obtained by known approaches, and the operation process can be mastered by those skilled in the art.
According to the technical scheme of the invention, high-purity iron, high-sulfur pig iron, electrolytic manganese, a nickel plate, a pure aluminum block, chromium nitride and a carburant are used as raw materials, the raw materials are proportioned according to the components of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar, the raw materials of the alloys are shown in the table 1, the alloy is smelted to prepare a high-nitrogen low-density free-cutting steel ingot, and the components, the inclusions, the mechanical properties, the fracture morphology of a tensile sample and the like of the steel are detected and analyzed.
TABLE 1 Single material (wt%)
| Mn | Si | Ni | C | S | P | Cr | O | N | Al | |
| High purity iron | 0.04 | 0 | 0 | 0.003 | 0.001 | 0.004 | 0.01 | 0.008 | 0 | 0 |
| High-sulfur pig iron | 0.04 | 0.012 | 0 | 0.003 | 48 | 0.004 | 0 | 0.01 | 0 | 0 |
| Electrolytic manganese | 99.58 | 0.015 | 0 | 0 | 0.100 | 0.010 | 0 | 0 | 0 | 0 |
| |
0 | 1.5 | 0 | 0.03 | 0.04 | 0.03 | 60 | 0.01 | 5.0 | 0 |
| |
0 | 0 | 99.98 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| |
0 | 0 | 0 | 97.50 | 0 | 0 | 0 | 0 | 0 | 0 |
| |
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 99.80 |
Example 1
First, preparing the ingredients
According to the target components: c: 0.5%, Mn: 20.0%, Ni: 8.0%, S: 0.1%, Cr: 7.2%, Al: 4.0%, N: 0.65%, P: the mass of each material was calculated at 0.008% mass. The high-purity iron is weighed by using a 100kg electronic scale, the high-sulfur pig iron, the electrolytic manganese, the nickel plate, the pure aluminum block, the chromium nitride and the carburant are weighed by using a 200g electronic scale, the furnace burden is polished by using a grinding wheel before being weighed, the surface oxide skin of each furnace burden is removed, the furnace burden is dried, and the total weight of each furnace burden is 120 kg. The amounts of the respective raw materials used in example 1 are shown in table 2.
Table 2 example 1 dosage sheet
| Material(s) | Electrolytic manganese | Pure aluminum block | Nickel plate | High-sulfur pig iron | Chromium iron nitride | Carburant | High purity iron |
| Weight/kg | 30.1 | 6.0 | 9.6 | 0.32 | 19.5 | 0.77 | 53.71 |
The second step is that: vacuum furnace smelting
Firstly, adding high-purity iron and a nickel plate into a vacuum induction smelting furnace, then checking the safety of the furnace, closing the furnace, vacuumizing to 3pa, then transmitting power to slowly melt the high-purity iron and the nickel plate, then heating to 1500 ℃ and keeping for 15min, flushing argon 18000pa after the high-purity iron and the nickel plate are completely melted down, then adding high-sulfur pig iron, electrolytic manganese, a pure aluminum block, ferrochromium nitride and a carburant, refining for 5min after all alloy materials are melted down, and the refining temperature is 1515 ℃; standing for 3min after refining;
the third step: pouring
After sampling and detecting components reach the standard, increasing power again, raising the temperature to 1550 ℃ for keeping for 10min, tapping, pouring molten steel into a metal mold with the diameter of 200mm multiplied by 400mm, solidifying and cooling in a vacuum induction furnace, and cooling to room temperature to obtain a high-nitrogen low-density free-cutting steel ingot with the diameter of 200 mm;
the fourth step: forging
Cutting off the riser and tail of the ingot before forging, and obtaining the ingot with the diameter of 200mm multiplied by 150mm after cutting off the middle. And (2) heating the ingot in a muffle furnace at 1100 ℃ for 60min, taking out the ingot after heating, forging the ingot on forging equipment into a bar with the diameter of 100mm, then returning to the furnace for heating at 1100 ℃ for 30min, taking out the bar forged into a bar with the diameter of 60mm, and air-cooling to room temperature to obtain the high-nitrogen low-density free-cutting steel bar with the diameter of 60mm, wherein the composition of the high-nitrogen low-density free-cutting steel bar is shown in example 1 in Table 4.
Example 2
According to the target components: c: 0.55%, Mn: 22.0%, Ni: 6.0%, S: 0.15%, Cr: 7.5%, Al: 6.0%, N: 0.60%, P: the mass of each material (high-purity iron, high-sulfur pig iron, electrolytic manganese, nickel plate, pure aluminum block, chromium nitride, carburant) was calculated at 0.008 mass%. The amounts of the respective raw materials used in example 2 are shown in table 3. The burdening, vacuum furnace melting and pouring are the same as those shown in example 1, except that: cutting off the riser and the tail of the ingot before forging, and obtaining two sections of ingots with the diameter of 200mm multiplied by 140mm after cutting off the middle. And (3) heating a section of ingot in a muffle furnace at 1200 ℃ for 30min, taking out the ingot after heating and heat preservation, forging the ingot into a bar with the diameter of 120mm on forging equipment, then returning to the furnace for heating at 1200 ℃ for 15min, taking out the bar and forging the bar into a bar with the diameter of 60mm, and air-cooling the bar to room temperature to obtain the high-nitrogen low-density free-cutting steel bar with the diameter of 60mm, wherein the composition of the high-nitrogen low-density free-cutting steel bar is shown in example 2 in the table 4.
Table 3 example 2 batch sheet
| Material(s) | Electrolytic manganese | Pure aluminum block | Nickel plate | High-sulfur pig iron | Chromium iron nitride | Carburant | High purity iron |
| Weight/kg | 33.1 | 9.0 | 7.2 | 0.47 | 18 | 0.85 | 51.4 |
Table 4 final alloy compositions of examples 1 and 2
| Element(s) | C | Mn | Ni | Al | Cr | S | N | P |
| Example 1 | 0.51 | 20.2 | 8.1 | 4.0 | 7.2 | 0.11 | 0.65 | 0.009 |
| Example 2 | 0.55 | 22.1 | 5.9 | 6.1 | 7.5 | 0.15 | 0.61 | 0.008 |
FIG. 1 is a graph showing 500 times of a gold phase of sulfide in a high-nitrogen low-density free-cutting steel according to example 1 of the present invention, and FIG. 2 is a graph showing 500 times of a gold phase of sulfide in a high-nitrogen low-density free-cutting steel according to example 2 of the present invention, and it can be seen from FIGS. 1 and 2 that sulfide distribution in a high-nitrogen low-density free-cutting steel according to the present invention is relatively uniform. FIG. 3 is a stress-strain curve of a high-nitrogen low-density free-cutting steel in example 1 of the present invention, and FIG. 4 is a stress-strain curve of a high-nitrogen low-density free-cutting steel in example 2 of the present invention, and it can be seen from FIGS. 3 and 4 that the tensile strength of examples 1 and 2 is not less than 750MPa, the yield strength is not less than 500MPa, the reduction of area is not less than 20%, the elongation after fracture is not less than 30%, the impact toughness is not less than 20J, and the steel has good ductility. FIG. 5 is an SEM topographic map of the forged fracture of the high-nitrogen low-density free-cutting steel of example 1 of the present invention, 1000 times, and FIG. 6 is an SEM topographic map of the forged fracture of the high-nitrogen low-density free-cutting steel of example 2 of the present invention, it can be seen from FIGS. 5 and 6 that pits appear in the fractures of examples 1 and 2, and the high-nitrogen low-density free-cutting steel is ductile fracture and has good ductility and toughness. FIG. 7 shows the chips at a rotation speed of 180r/min for the high-nitrogen low-density free-cutting steel of example 1 of the present invention, FIG. 8 shows the chips at a rotation speed of 180r/min for the high-nitrogen low-density free-cutting steel of example 2 of the present invention, and it can be seen from FIGS. 7 and 8 that the high-nitrogen low-density free-cutting steel of examples 1 and 2 of the present invention has good chip breaking during the cutting process and good cutting performance.
The mechanical properties of the invention in example 1 and example 2 are determined by making a tensile test bar with a diameter of 5mm and a standard V-shaped notched Charpy impact test sample with a diameter of 10mm multiplied by 55mm according to the current national standards of GB/T228.1-2010 and GB/T19748-2005, and performing room temperature tensile and Charpy impact tests through an MTS Landmark 370 electrohydraulic servo universal tester and an MTS drop hammer impact tester. The tensile strength, yield strength, elongation after fracture, reduction of area and impact toughness of examples 1 and 2 are shown in Table 5. As can be seen from Table 5, the Fe-Mn-Al-N-S high-nitrogen low-density free-cutting steel bar has a tensile strength of 750MPa or more, a yield strength of 500MPa or more, a reduction of area of 20% or more, an elongation after fracture of 30% or more, an impact toughness of 20J or more, good strong plasticity, a density of 7.35g/cm or less3Has better low density and cutting performance matching.
TABLE 5 mechanical Properties of examples 1 and 2
Claims (7)
- A Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar is characterized in that: the chemical mass percentage is as follows: 0.3-0.6% of C, 18.0-22.0% of Mn, 5.0-10.0% of Ni, 2.0-6.0% of Al, 5.0-10.0% of Cr, 0.01-0.5% of S, 0.35-0.65% of N, P being less than or equal to 0.01%, and the balance of Fe and inevitable impurities.
- 2. The Fe-Mn-Al-N-S based high-nitrogen low-density free-cutting steel rod material according to claim 1, characterized in that: the mass percentage content of Al is 3.0-5.0%.
- 3. The Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel rod material according to claim 1 or 2, characterized in that: the mass percentage content of S is 0.1-0.3%.
- 4. The Fe-Mn-Al-N-S based high-nitrogen low-density free-cutting steel rod material according to any one of claims 1 to 3, characterized in that: the weight percentage of Mn and S satisfies that Mn/S is more than or equal to 140 and less than or equal to 200; the weight percentage of Al and Ni satisfies that the weight percentage of Al + Ni is more than or equal to 10 and less than or equal to 15.
- 5. The method for producing a Fe-Mn-Al-N-S based high-nitrogen low-density free-cutting steel bar material as claimed in any one of claims 1 to 4, wherein: the method comprises the following steps: the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar material as claimed in any one of claims 1 to 4, wherein the steel bar material is prepared by mixing the components, then melting the raw materials, casting to obtain an ingot with a diameter of 200-250 mm, heating the ingot at 1000-1200 ℃ for 30-60 min, forging to obtain a bar material with a diameter of 100-120 mm, continuing heating at 1000-1200 ℃ for 20-30 min, taking out the bar material, forging to obtain a bar material with a diameter of 60-65 mm, and cooling to room temperature.
- 6. The method for producing a Fe-Mn-Al-N-S system high-nitrogen low-density free-cutting steel bar material according to claim 5, characterized in that: the method comprises the following steps:1) preparing materials: the raw materials of high-purity iron, high-sulfur pig iron, electrolytic manganese, a nickel plate, a pure aluminum block, chromium nitride and a carburant are proportioned according to the requirements of the components of the Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel bar material of any one of claims 1 to 4;2) smelting in a vacuum furnace: adding high-purity iron and a nickel plate into a vacuum induction smelting furnace, closing the furnace, vacuumizing, powering to melt the high-purity iron and the nickel plate after the vacuum degree is 1-5 pa, heating to 1500-1510 ℃, flushing argon to 15000-20000 pa after the high-purity iron and the nickel plate are completely melted down, then adding high-sulfur pig iron, electrolytic manganese, a pure aluminum block, chromium nitride and a carburant, refining for 5-10 min after the alloy is completely melted down, and the refining temperature is 1510-1520 ℃; standing after refining is finished;3) pouring: raising the temperature to 1530-1550 ℃, pouring molten steel into a metal mold with the diameter phi of 200-250 mm, and cooling the molten steel to room temperature to obtain an ingot;4) forging: heating the ingot to 1000-1200 ℃ for 30-60 min, taking out the ingot, forging the ingot into a bar with the diameter of 100-120 mm, returning the bar to the furnace, continuously heating the bar with the heating temperature of 1000-1200 ℃ for 20-30 min, taking out the bar with the diameter of 60-65 mm, and air-cooling the bar to the room temperature.
- 7. The method for producing a Fe-Mn-Al-N-S series high-nitrogen low-density free-cutting steel rod material according to claim 5 or 6, characterized in that: the recarburizing agent is artificial graphite, natural graphite or coke.
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Application publication date: 20210810 |