CN117431467A - Production method of non-quenched and tempered steel for shaft - Google Patents
Production method of non-quenched and tempered steel for shaft Download PDFInfo
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 106
- 239000010959 steel Substances 0.000 title claims abstract description 106
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 17
- 238000005096 rolling process Methods 0.000 claims abstract description 31
- 238000001816 cooling Methods 0.000 claims abstract description 21
- 238000009749 continuous casting Methods 0.000 claims abstract description 11
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- 239000000126 substance Substances 0.000 claims abstract description 7
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 7
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 6
- 239000012535 impurity Substances 0.000 claims abstract description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 6
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 27
- 238000005266 casting Methods 0.000 claims description 20
- 238000010438 heat treatment Methods 0.000 claims description 16
- 238000000137 annealing Methods 0.000 claims description 15
- 238000007670 refining Methods 0.000 claims description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 10
- 238000001514 detection method Methods 0.000 claims description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000002893 slag Substances 0.000 claims description 7
- 238000003723 Smelting Methods 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 5
- 239000006247 magnetic powder Substances 0.000 claims description 5
- 238000004321 preservation Methods 0.000 claims description 5
- 238000010079 rubber tapping Methods 0.000 claims description 5
- 238000002791 soaking Methods 0.000 claims description 5
- 238000009489 vacuum treatment Methods 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 238000004886 process control Methods 0.000 claims description 2
- 238000005496 tempering Methods 0.000 abstract description 12
- 229910052742 iron Inorganic materials 0.000 abstract description 6
- 239000000463 material Substances 0.000 abstract description 6
- 238000010791 quenching Methods 0.000 abstract description 6
- 230000000171 quenching effect Effects 0.000 abstract description 6
- 229910052799 carbon Inorganic materials 0.000 abstract description 5
- 238000005516 engineering process Methods 0.000 abstract description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 abstract description 3
- 238000013461 design Methods 0.000 abstract description 3
- 229910045601 alloy Inorganic materials 0.000 abstract description 2
- 239000000956 alloy Substances 0.000 abstract description 2
- 238000005098 hot rolling Methods 0.000 abstract 1
- 238000005728 strengthening Methods 0.000 description 7
- 229910000859 α-Fe Inorganic materials 0.000 description 6
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 238000005204 segregation Methods 0.000 description 4
- 239000002344 surface layer Substances 0.000 description 4
- 229910052720 vanadium Inorganic materials 0.000 description 4
- 229910000954 Medium-carbon steel Inorganic materials 0.000 description 3
- 238000007664 blowing Methods 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 150000001247 metal acetylides Chemical class 0.000 description 3
- 150000004767 nitrides Chemical class 0.000 description 3
- 238000010587 phase diagram Methods 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 239000010955 niobium Substances 0.000 description 2
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 229910052719 titanium Inorganic materials 0.000 description 2
- 239000010936 titanium Substances 0.000 description 2
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 2
- 229910000617 Mangalloy Inorganic materials 0.000 description 1
- 229910000746 Structural steel Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical class [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- PMHQVHHXPFUNSP-UHFFFAOYSA-M copper(1+);methylsulfanylmethane;bromide Chemical compound Br[Cu].CSC PMHQVHHXPFUNSP-UHFFFAOYSA-M 0.000 description 1
- 229910052593 corundum Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011143 downstream manufacturing Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 238000009849 vacuum degassing Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
- 229910001845 yogo sapphire Inorganic materials 0.000 description 1
Classifications
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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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/10—Handling in a vacuum
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
- C21D1/30—Stress-relieving
-
- 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
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
-
- 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
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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
-
- 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- 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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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Child & Adolescent Psychology (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Abstract
The production process of non-quenched and tempered steel for shaft includes the technological steps of converter, LF furnace, RH furnace, continuous casting, hot rolling, and the steel has chemical components of C=0.37-0.44 wt%, si=0.17-0.37 wt%, mn=0.5-0.8 wt%, P not more than 0.030 wt%, S not more than 0.030 wt%, cr=0.90-1.1 wt%, al=0.005-0.025 wt%, N=0.003-0.008 wt%, H not more than 0.0002 wt%, O not more than 0.0020 wt%, and Fe and essential impurity for the rest. The invention adopts the design of medium carbon low alloy components, strictly controls the purity of molten steel, adopts the novel technology of high-temperature high-pressure rolling, controlled rolling and controlled cooling and the novel technology of online quenching tempering, and develops the non-tempering steel for the shaft to reach the 40Cr strength and plasticity index of the tempering material, and the produced steel is made into the motor shaft equiaxed parts by trial, can meet the strength performance requirement without carrying out the whole-section tempering treatment of the parts, and can be widely used for manufacturing motor shaft products.
Description
Technical Field
The invention belongs to the technical field of metallurgy, and relates to a production method of energy-saving environment-friendly high-toughness turning non-quenched and tempered steel.
Background
At present, the motor shaft parts are generally subjected to tempering heat treatment turning by adopting medium carbon structural steel, for example, 40Cr is subjected to tempering heat treatment, the tempering cost is high, the production efficiency is lower, the energy consumption is increased and the environment is polluted due to the tempering process, and meanwhile, some waste products are lost, so that the current energy-saving and environment-friendly requirements are not met. Therefore, in recent years, various enterprises develop non-quenched and tempered steel in shaft and rod applications, namely, vanadium, titanium and niobium microalloying elements are added on the basis of medium-carbon manganese steel, and fine carbides and nitrides precipitated by the microalloying elements of vanadium, titanium and niobium are utilized to strengthen the steel, so that the steel achieves the strength of quenched and tempered steel when quenching and tempering are not performed.
Various performance indexes such as the strength of non-quenched and tempered steel produced by each steel mill at present can reach the level of 40Cr quenched and tempered steel, but the economic benefit is poor, obvious economic benefit is not generated by the steel mill and downstream processing enterprises, and the effect is not obvious in product use and popularization. Therefore, development of a non-quenched and tempered steel for motor shafts with a diameter of 20-99 mm, which is suitable in cost and can meet the use performance of 40Cr quenched and tempered materials, has practical research significance.
Disclosure of Invention
The invention aims to provide a production method of non-quenched and tempered steel for shafts, which is used for producing the non-quenched and tempered steel with the full-section hardness of 240-290 HBW of round steel with the tensile strength of more than or equal to 820Mpa, the yield strength of more than or equal to 540Mpa, the elongation rate of more than or equal to 22%, the area reduction rate of more than or equal to 60%, the grain size of more than or equal to 7.0 grade, the room-temperature impact energy Aku2 of more than or equal to 60J and the diameter of 20-99 mm.
The aim of the invention is achieved by the following technical scheme:
the production process of non-quenched and tempered steel for shaft includes the chemical components of C=0.37-0.44 wt%, si=0.17-0.37 wt%, mn=0.5-0.8 wt%, P not more than 0.030 wt%, S not more than 0.030 wt%, cr=0.90-1.1 wt%, al=0.005-0.025 wt%, N=0.003-0.008 wt%, H not more than 0.0002 wt%, O not more than 0.0020 wt%, and Fe and essential impurity for the rest; the key process steps comprise:
1) Smelting: the tapping C of the converter is more than or equal to 0.08 percent, an LF+RH furnace refining process is adopted, argon is blown in the whole process of LF furnace refining, slag formation and deoxidation are carried out, the white slag holding time is more than or equal to 30 minutes, and the process control Als=0.015 to 0.025 percent; vacuum treatment is carried out in an RH furnace, the vacuum maintaining time is not less than 20min below the vacuum degree of 0.5 torr, the H of the discharged molten steel is less than or equal to 2ppm, and the O is less than or equal to 10ppm;
2) Continuous casting: adopting whole-process protection casting, wherein the ladle superheat degree continuous casting furnace is less than or equal to 25 ℃, the casting furnace is less than or equal to 35 ℃, and the casting blank size is 280mm multiplied by 280mm;
3) Heating: the heating time of the casting blank is 280-480 min, the temperature of the preheating section is less than or equal to 600 ℃, the temperature of the heating section is 1140-1200 ℃, and the temperature of the soaking section is 1160-1220 ℃;
4) Rolling: the bar line two-roller horizontal interchange 850 rolling mill adopts large reduction to roll, and the reduction of the first pass and the second pass is respectively controlled according to 70mm and 65mm; the initial rolling temperature is more than or equal to 1000 ℃; the final rolling is carried out by adopting a three-roller mill, and the final rolling temperature is 700-740 ℃;
5) And (3) cooling: the rolled round steel is subjected to forced water cooling by a water tank, the temperature of an upper cooling bed is ensured to be 500-580 ℃, and a tooth-separated upper cooling bed is adopted;
6) Finishing: sawing the round steel, and performing ultrasonic flaw detection and magnetic powder surface flaw detection on the finished round steel;
7) Stress relief annealing: the whole finished round steel is subjected to stress relief annealing by adopting a trolley furnace, the annealing temperature is 300-350 ℃, the heat preservation time is 4 hours, and finally the non-quenched and tempered steel with the tensile strength of not less than 820Mpa, the yield strength of not less than 540Mpa, the elongation of not less than 22%, the area reduction of not less than 60%, the grain size of not less than 7.0 grade, the room temperature impact energy Aku2 of not less than 60J and the full section hardness of the round steel with the diameter of 20-99 mm of 240-290 HBW is obtained.
The principle of the invention:
the invention mainly guarantees the strength, hardness and toughness of the product from the following aspects.
(1) The design of chemical components: the non-quenched and tempered steel is obtained by adding trace amounts of strong carbide forming elements into medium carbon steel, cooling to room temperature after controlled rolling and controlled cooling, and utilizing precipitation strengthening of carbon (nitrogen) compounds to reach the strengthening level after quenching and tempering of the medium carbon steel, thereby omitting the quenching and tempering treatment procedure. The method is energy-saving and environment-friendly, shortens the production period, can avoid quenching deformation and cracking, improves the product quality and reduces the manufacturing cost.
Determination of C content: c is used as the most economical and basic strengthening element in steel, the strength of the steel can be obviously improved through solid solution strengthening and precipitation strengthening, but too high C can bring adverse effects to the center segregation, the toughness and the welding performance of the steel; the C content range of the invention is determined to be 0.37-0.44%, and the invention relates to steel materials which belong to the category of medium carbon steel;
determination of Si content: the Si is reinforced ferrite, so that the matrix strength of the material can be improved, and the Si contributes to the yield strength and the tensile strength of the material obviously. The Si content range of the invention is determined to be 0.17-0.37%;
determination of Mn content: mn can improve the tensile strength of steel through solid solution strengthening, improves the hardenability of the steel, and can also fix the form of sulfur in the steel and form MnS and (Fe, mn) S which have less harm to the performance of the steel as deoxidizing elements in the steelmaking process, thereby reducing or inhibiting the generation of FeS; however, mn element belongs to an easily segregated element, and the center segregation of the steel is serious due to the excessively high content; the Mn content range of the invention is determined to be 0.5-0.8%;
determination of Cr content: cr is a carbide forming element, and Cr which dissolves in austenite when heated can improve hardenability. Cr in the steel is partially dissolved into ferrite to generate solid solution strengthening, so that the strength and hardness of the ferrite are improved; cr also reduces the tendency of the steel to overheat and the surface decarburization rate; however, when the Cr content is too high, the Cr is combined with carbon in the steel, massive carbides are easily formed, and the plastic toughness of the steel is reduced by the indissoluble carbides; and the Cr content is too high, so that the hardness of the steel is too high, and the steel is not beneficial to processing and use of clients. Taking the above factors into consideration, the Cr content range of the invention is determined to be 0.90-1.1%;
determination of Al content: the aluminum nitride inclusions with fine dispersion formed by the Al element and N can refine grains, but the Al content is large, brittle inclusions such as Al2O3 and the like are easy to form in the molten steel smelting process, and the purity of the molten steel is reduced; meanwhile, al is also added as a deoxidizing element in the steel, so that the dissolved oxygen in the molten steel is reduced; the Al content range of the invention is determined to be 0.005-0.025%;
determination of S element: the S element can be combined with the Mn element to form hard and brittle MnS, so that the cutting processability of the steel is improved; promoting the formation of intra-crystalline ferrite; however, excessive S content can cause the steel to generate hot shortness, reduce the toughness of the steel and increase the center segregation of the steel; the S content range of the invention is determined to be less than or equal to 0.030%;
determination of P content: p seriously causes segregation in solidification in steel, and P dissolves in ferrite to distort and coarsen grains, and increases cold shortness. The range of the P content is determined to be less than or equal to 0.030%;
determination of N content: the V, al element in the steel is combined with N to form nitride to play the roles of improving strength and refining grains, so that a proper amount of N element is needed, and the N content range of the invention is determined to be 0.003-0.008% according to the V, al content and the stoichiometric proportion of the corresponding nitride.
(2) And the nonmetallic inclusion in the steel is reduced. Because of the existence of nonmetallic inclusion in the steel, the continuity of the metal matrix is broken, stress concentration is easy to occur, and the steel becomes an origin of metal fatigue. The majority of cracks occur between the oxide, the punctiform inclusions and the matrix, and when the stress is sufficiently large, the cracks are generated and rapidly propagate to break. The lower the plasticity of the nonmetallic inclusion, the more sharp the shape, the greater the stress concentration. In order to improve the fatigue life of the product, vacuum degassing treatment and external refining are controlled, the content of nonmetallic inclusion is reduced, and the type and distribution state of the inclusion are changed.
(3) Optimizing the rolling process and improving the grain size of the product. The surface layer of the round steel is a tempered structure, the metallographic structure of the rest part of the round steel is ferrite and pearlite, and the grain size is 7-9 grades; the fine grains can improve the toughness of the product and correspondingly improve the fatigue resistance.
The invention has the beneficial effects that: the invention adopts a medium-carbon low-alloy component design, an LF+RH composite refining technology, strictly controls the purity of molten steel, adopts a novel technology of high-temperature high-pressure rolling, controlled rolling and controlled cooling and a novel technology of online quenching tempering, and develops non-quenched and tempered steel for shafts, which reaches the 40Cr strength and plasticity index of the quenched and tempered material, the tensile strength is more than or equal to 820Mpa, the yield strength is more than or equal to 540Mpa, the elongation is more than or equal to 22%, the reduction of area is more than or equal to 60%, the grain size is more than or equal to 7.0 level, the room-temperature impact energy Aku2 is more than or equal to 60J, and the full-section hardness of round steel with the diameter of 20mm-99mm is 240-290 HBW. The production cost is lower than that of quenched and tempered steel, and the method has obvious economic benefit. The invention breaks through the conventional production process, utilizes the existing equipment and process conditions of the steel mill, fully exerts the equipment advantages, saves energy and protects the environment, produces the non-quenched and tempered steel with high toughness, uniform hardness and low cost, and can be widely applied to manufacturing key parts of motor shafts.
Drawings
FIG. 1 is a 1/4 diameter metallographic photograph of a round bar of example 1;
FIG. 2 is a 2mm metallographic image of the surface layer of the round bar of example 1;
FIG. 3 is a 1/4 diameter metallographic photograph of a round bar of example 2;
FIG. 4 is a 2mm metallographic image of the surface layer of a round bar of example 2;
FIG. 5 is a 1/4 diameter metallographic photograph of a round bar of example 3;
FIG. 6 is a 2mm metallographic image of the surface layer of the round bar of example 3.
Detailed Description
Example 1:
the production process of non-quenched and tempered steel for shaft includes the chemical components of C=0.38 wt%, si=0.25 wt%, mn=0.7 wt%, P=0.010 wt%, S=0.005 wt%, cr=1.0 wt%, al=0.010 wt%, N=0.005 wt%, H=0.0002 wt%, O=0.0010 wt%, and Fe and essential impurity for the rest. The key process steps comprise:
1) Smelting: converter tapping c=0.09%, adopting an LF+RH furnace refining process, blowing argon in the whole process of LF furnace refining, slagging and deoxidizing, keeping white slag for 35min, and controlling Als=0.020%; RH vacuum treatment, vacuum maintaining time is 22min below 0.5 torr, and the H=1.6ppm and O=10 ppm of the discharged molten steel;
2) Continuous casting: adopting whole-process protection casting, wherein the ladle superheat degree continuous casting furnace is 24 ℃, the casting furnace is started to be 30 ℃, and the size of a casting blank is 280mm multiplied by 280mm;
3) Heating: the casting blank is heated for 300min, the preheating section temperature is 580 ℃, the heating section temperature is 1160 ℃, and the soaking section temperature is 1180 ℃;
4) Rolling: the specification of the final finished round steel is 72mm; the bar line two-roller horizontal interchange 850 rolling mill adopts large reduction to roll, and the reduction of the first pass and the second pass is respectively controlled according to 70mm and 65mm; the initial rolling temperature is 1020 ℃; the final rolling is carried out by adopting a three-roller mill, and the final rolling temperature is 710 ℃;
5) And (3) cooling: the rolled round steel is cooled by water tank through water, the upper cooling bed temperature is 560 ℃, and the upper cooling bed with teeth is adopted;
6) Finishing: sawing the round steel, and performing ultrasonic flaw detection and magnetic powder surface flaw detection on the finished round steel;
7) Stress relief annealing: and carrying out stress relief annealing on the whole finished round steel by adopting a trolley furnace, wherein the annealing temperature is 320 ℃, and the heat preservation time is 4 hours.
The results of the steel property tests are shown in tables 1 to 3. The round steel metal phase diagram is shown in fig. 1 and 2.
Example 2:
the production process of non-quenched and tempered steel for shaft includes the chemical components of C=0.43 wt%, si=0.25 wt%, mn=0.75 wt%, P=0.010 wt%, S=0.005 wt%, cr=1.05 wt%, al=0.010 wt%, N=0.005 wt%, H=0.0002 wt%, O=0.0010 wt%, and Fe and essential impurity for the rest. The key process steps comprise:
1) Smelting: converter tapping c=0.09%, adopting an LF+RH furnace refining process, blowing argon in the whole process of LF furnace refining, slagging and deoxidizing, keeping white slag for 35min, and controlling Als=0.020%; RH vacuum treatment, vacuum maintaining for 25min below 0.5 torr, discharging molten steel H=1.6 ppm, O=10 ppm;
2) Continuous casting: adopting whole-process protection casting, wherein the ladle superheat degree continuous casting furnace is 24 ℃, the casting furnace is started to be 30 ℃, and the size of a casting blank is 280mm multiplied by 280mm;
3) Heating: the heating time of the casting blank is 460min, the preheating section temperature is 580 ℃, the heating section temperature is 1180 ℃, and the soaking section temperature is 1210 ℃;
4) Rolling: the specification of the final finished round steel is 65mm; the bar line two-roller horizontal interchange 850 rolling mill adopts large reduction to roll, and the reduction of the first pass and the second pass is respectively controlled according to 70mm and 65mm; the initial rolling temperature is 1050 ℃; the final rolling is carried out by adopting a three-roller mill, and the final rolling temperature is 710 ℃;
5) And (3) cooling: the rolled round steel is cooled by water tank through water, the upper cooling bed temperature is 540 ℃, and the upper cooling bed with teeth is used;
6) Finishing: sawing the round steel, and performing ultrasonic flaw detection and magnetic powder surface flaw detection on the finished round steel;
7) Stress relief annealing: and carrying out stress relief annealing on the whole finished round steel by adopting a trolley furnace, wherein the annealing temperature is 320 ℃, and the heat preservation time is 4 hours.
The results of the steel property tests are shown in tables 1 to 3. The round steel metal phase diagram is shown in fig. 3 and 4.
Example 3:
the production process of non-quenched and tempered steel for shaft includes the chemical components of C=0.41 wt%, si=0.25 wt%, mn=0.55 wt%, P=0.010 wt%, S=0.005 wt%, cr=0.92 wt%, al=0.010 wt%, N=0.006 wt%, H=0.0002 wt%, O=0.0010 wt%, and Fe and essential impurity for the rest. The key process steps comprise:
1) Smelting: converter tapping C=0.10%, adopting LF+RH refining process, blowing argon in the whole process of LF refining, slagging and deoxidizing, keeping white slag for 35min, and controlling Als=0.020%; RH vacuum treatment, vacuum maintaining for 28min below 0.5 torr, discharging molten steel H=1.6ppm, O=10 ppm;
2) Continuous casting: adopting whole-process protection casting, wherein the ladle superheat degree continuous casting furnace is 24 ℃, the casting furnace is started to be 30 ℃, and the size of a casting blank is 280 multiplied by 280mm;
3) Heating: the heating time of the casting blank is 360min, the preheating section temperature is 560 ℃, the heating section temperature is 1165 ℃, and the soaking section temperature is 1180 ℃;
4) Rolling: the specification of the final finished round steel is 43mm; the bar line two-roller horizontal interchange 850 rolling mill adopts large reduction to roll, and the reduction of the first pass and the second pass is respectively controlled according to 70mm and 65mm; the initial rolling temperature is 1025 ℃; the final rolling is carried out by adopting a three-roller mill, and the final rolling temperature is 740 ℃;
5) And (3) cooling: the rolled round steel is cooled by water tank through water, the upper cooling bed temperature is 580 ℃, and the upper cooling bed with teeth is adopted;
6) Finishing: sawing the round steel, and performing ultrasonic flaw detection and magnetic powder surface flaw detection on the finished round steel;
7) Stress relief annealing: and carrying out stress relief annealing on the whole finished round steel by adopting a trolley furnace, wherein the annealing temperature is 320 ℃, and the heat preservation time is 4 hours.
The results of the steel property tests are shown in tables 1 to 3. The round steel metal phase diagram is shown in fig. 5 and 6.
Table 1 mechanical properties of example steels
| Sequence number | Tensile strength, MPa | Yield strength, MPa | Elongation percentage,% | Shrinkage of area, percent |
| Example 1 | 955 | 724 | 22.0 | 64 |
| Example 2 | 980 | 720 | 22.4 | 66 |
| Example 3 | 961 | 712 | 23.2 | 65 |
TABLE 2 examination of impact work, hot-rolled hardness, grain size and strip texture of example steels
| Sequence number | Impact work, J | Hot rolled core hardness, HBW | Hot rolled surface hardness, HBW | Grain size, grade | Band organization, level |
| Example 1 | 75 | 249 | 286 | 8 | 1.5 |
| Example 2 | 80 | 245 | 290 | 8 | 2.0 |
| Example 3 | 86 | 258 | 283 | 8.5 | 1.5 |
TABLE 3 test of nonmetallic inclusion in example steels
| Sequence number | A | B | C | D | Ds |
| Example 1 | 1.5 | 0 | 0 | 1.0 | 0 |
| Example 2 | 1.0 | 0 | 0 | 1.0 | 0 |
| Example 3 | 1.0 | 0 | 0 | 1.0 | 0 |
As can be seen from the test results in tables 1 to 3, the non-quenched and tempered steel for the shaft, which is produced by the method, has excellent various inspection indexes, low gas content of steel and low nonmetallic inclusion content, and can well meet the use requirements of motor shaft products.
Claims (1)
1. A production method of non-quenched and tempered steel for shafts is characterized by comprising the following steps of: the steel comprises the following chemical components, by weight, C=0.37-0.44%, si=0.17-0.37%, mn=0.5-0.8%, P < 0.030%, S < 0.030%, cr=0.90-1.1%, al=0.005-0.025%, N=0.003-0.008%, H < 0.0002%, O < 0.0020%, and the balance Fe and essential impurities; the key process steps comprise:
1) Smelting: the tapping C of the converter is more than or equal to 0.08 percent, an LF+RH furnace refining process is adopted, argon is blown in the whole process of LF furnace refining, slag formation and deoxidation are carried out, the white slag holding time is more than or equal to 30 minutes, and the process control Als=0.015 to 0.025 percent; vacuum treatment is carried out in an RH furnace, the vacuum maintaining time is not less than 20min below the vacuum degree of 0.5 torr, the H of the discharged molten steel is less than or equal to 2ppm, and the O is less than or equal to 10ppm;
2) Continuous casting: adopting whole-process protection casting, wherein the ladle superheat degree continuous casting furnace is less than or equal to 25 ℃, the casting furnace is less than or equal to 35 ℃, and the casting blank size is 280mm multiplied by 280mm;
3) Heating: the heating time of the casting blank is 280-480 min, the temperature of the preheating section is less than or equal to 600 ℃, the temperature of the heating section is 1140-1200 ℃, and the temperature of the soaking section is 1160-1220 ℃;
4) Rolling: the bar line two-roller horizontal interchange 850 rolling mill adopts large reduction to roll, and the reduction of the first pass and the second pass is respectively controlled according to 70mm and 65mm; the initial rolling temperature is more than or equal to 1000 ℃; the final rolling is carried out by adopting a three-roller mill, and the final rolling temperature is 700-740 ℃;
5) And (3) cooling: the rolled round steel is subjected to forced water cooling by a water tank, the temperature of an upper cooling bed is ensured to be 500-580 ℃, and a tooth-separated upper cooling bed is adopted;
6) Finishing: sawing the round steel, and performing ultrasonic flaw detection and magnetic powder surface flaw detection on the finished round steel;
7) Stress relief annealing: the whole finished round steel is subjected to stress relief annealing by adopting a trolley furnace, the annealing temperature is 300-350 ℃, the heat preservation time is 4 hours, and finally the non-quenched and tempered steel with the tensile strength of not less than 820Mpa, the yield strength of not less than 540Mpa, the elongation of not less than 22%, the area reduction of not less than 60%, the grain size of not less than 7.0 grade, the room temperature impact energy Aku2 of not less than 60J and the full section hardness of the round steel with the diameter of 20-99 mm of 240-290 HBW is obtained.
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| CN107697855A (en) * | 2017-08-30 | 2018-02-16 | 宁波韧霸货叉有限公司 | A kind of high rigidity fork of forklift truck |
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