CN113564484A - Steel for engine connecting rod and production method thereof - Google Patents
Steel for engine connecting rod and production method thereof Download PDFInfo
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- CN113564484A CN113564484A CN202110952023.2A CN202110952023A CN113564484A CN 113564484 A CN113564484 A CN 113564484A CN 202110952023 A CN202110952023 A CN 202110952023A CN 113564484 A CN113564484 A CN 113564484A
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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 24
- 238000007670 refining Methods 0.000 claims abstract description 45
- 238000000034 method Methods 0.000 claims abstract description 36
- 238000009749 continuous casting Methods 0.000 claims abstract description 22
- 238000010583 slow cooling Methods 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 14
- 239000012535 impurity Substances 0.000 claims abstract description 10
- 238000003723 Smelting Methods 0.000 claims abstract description 9
- 238000005096 rolling process Methods 0.000 claims abstract description 5
- 239000002893 slag Substances 0.000 claims description 35
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 19
- 238000001816 cooling Methods 0.000 claims description 14
- 239000000463 material Substances 0.000 claims description 12
- 238000009489 vacuum treatment Methods 0.000 claims description 11
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000010079 rubber tapping Methods 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 8
- 229910052782 aluminium Inorganic materials 0.000 claims description 8
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 6
- 238000005266 casting Methods 0.000 claims description 6
- 239000000498 cooling water Substances 0.000 claims description 6
- 229910052593 corundum Inorganic materials 0.000 claims description 5
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 5
- MBMLMWLHJBBADN-UHFFFAOYSA-N Ferrous sulfide Chemical compound [Fe]=S MBMLMWLHJBBADN-UHFFFAOYSA-N 0.000 claims description 4
- 238000010008 shearing Methods 0.000 claims description 4
- 238000002791 soaking Methods 0.000 claims description 4
- 229910000519 Ferrosilicon Inorganic materials 0.000 claims description 3
- 239000003795 chemical substances by application Substances 0.000 claims description 3
- 150000004767 nitrides Chemical class 0.000 claims description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 3
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 abstract description 11
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 10
- 230000000052 comparative effect Effects 0.000 description 9
- CADICXFYUNYKGD-UHFFFAOYSA-N sulfanylidenemanganese Chemical compound [Mn]=S CADICXFYUNYKGD-UHFFFAOYSA-N 0.000 description 9
- 238000005516 engineering process Methods 0.000 description 8
- 238000012545 processing Methods 0.000 description 8
- 238000004458 analytical method Methods 0.000 description 7
- 239000011593 sulfur Substances 0.000 description 7
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 6
- 239000002131 composite material Substances 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 229910045601 alloy Inorganic materials 0.000 description 4
- 239000000956 alloy Substances 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000007664 blowing Methods 0.000 description 4
- 238000005520 cutting process Methods 0.000 description 4
- 238000011161 development Methods 0.000 description 4
- 238000000921 elemental analysis Methods 0.000 description 4
- 230000000877 morphologic effect Effects 0.000 description 4
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 4
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 230000035882 stress Effects 0.000 description 4
- 229910000859 α-Fe Inorganic materials 0.000 description 4
- 229910001563 bainite Inorganic materials 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 3
- 239000011572 manganese Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000002159 abnormal effect Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 230000000737 periodic effect Effects 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 229910014458 Ca-Si Inorganic materials 0.000 description 1
- 229910000915 Free machining steel Inorganic materials 0.000 description 1
- 229910000677 High-carbon steel Inorganic materials 0.000 description 1
- 229910000742 Microalloyed steel Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 150000004763 sulfides Chemical class 0.000 description 1
- 230000008646 thermal stress Effects 0.000 description 1
- 238000005406 washing Methods 0.000 description 1
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/114—Treating the molten metal by using agitating or vibrating means
- B22D11/115—Treating the molten metal by using agitating or vibrating means by using magnetic fields
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/18—Controlling or regulating processes or operations for pouring
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/16—Controlling or regulating processes or operations
- B22D11/22—Controlling or regulating processes or operations for cooling cast stock or mould
- B22D11/225—Controlling or regulating processes or operations for cooling cast stock or mould for secondary cooling
-
- 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
-
- 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
- C21C7/0006—Adding metallic additives
-
- 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
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
-
- 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
-
- 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
-
- 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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
-
- 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
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- 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
-
- 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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
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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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/009—Pearlite
Abstract
The invention discloses a steel for an engine connecting rod and a production method thereof, wherein the steel comprises the following chemical components in percentage by mass: 0.69-0.73% of C, 0.15-0.25% of Si, 0.55-0.60% of Mn, less than or equal to 0.045% of P, 0.060-0.070% of S, 0.10-0.15% of Cr, 0.04-0.08% of Ni, 0.030-0.040% of V, less than or equal to 0.010% of Al, 0.0120-0.0160% of N, less than or equal to 0.0020% of O, and the balance of Fe and inevitable impurities; the production process route is as follows: converter smelting → LF refining furnace refining → RH vacuum furnace refining → continuous casting → rolling → slow cooling; the method can accurately control the contents of S and N in the steel, and the produced steel has proper structure and inclusion morphology and good comprehensive performance.
Description
Technical Field
The invention relates to the technical field of steel material manufacturing, in particular to steel for an engine connecting rod and a production method thereof.
Background
With the rapid development of the automobile industry, the design and manufacturing process of engine parts and components with high quality, high efficiency, low cost and low energy consumption becomes the only way to improve the product competitiveness. The production mode of the traditional and backward processing technology is difficult to adapt to the change of the market, and the change of the processing technology becomes a necessary development trend and development direction. Many new processes break the conventional process, and the new processes are carried out according to the characteristics of novel conception and remarkable benefit, thereby meeting the requirements of modern enterprises. The connecting rod cracking technology is an advanced new connecting rod processing technology appearing in the 20 th century, and compared with the traditional processing technology, the technology has the outstanding advantages of greatly improving the product quality, improving the production rate, reducing the production cost and the like, and is paid attention to in the industry.
The connecting rod is used as an important part of an engine and bears high periodic impact force, inertia force and bending force during working. The quality of the connecting rod manufacture directly affects the performance and reliability of the engine, which requires that the connecting rod have high strength, toughness and fatigue resistance, as well as high machining accuracy. The expansion-fracture characteristic determines that narrow component control is strictly needed, various mechanical properties are reasonably matched, and the grain size is controlled by adopting a micro-alloying mode, so that the production difficulty is high.
When many domestic manufacturers produce steel for high-carbon, sulfur-containing, nitrogen-containing and microalloy engine connecting rods, the LF refining furnace adopts high-alkalinity slag, the high-alkalinity slag system has great influence on the S content in the steel, particularly the S yield is greatly influenced, and the narrow-range control of the S is not easy to stabilize. And N in the steel is at a lower level after RH vacuum treatment, a large amount of nitrogen-containing alloy or cored wires need to be added in the later period, the alloy is melted by opening the bottom blowing stirring, the temperature drop is large, and secondary oxidation of the molten steel is easily caused.
The Chinese patent application number of 200910062748.3 discloses a production process method of low-carbon high-sulfur free-cutting steel, wherein a refining furnace is used for producing low-alkalinity slag, and the refining slag comprises the following components in percentage by weight: CaO 40-50%, SiO2 15-30%，Al2O320-35% of MgO, 5-15% of MgO; after chemical components except S in the steel enter the required range in the later stage of refining, feeding an S line into the refining furnace, and keeping the strength of argon blowing at the bottom of the ladle, wherein the recovery rate of S is 75-85%; the chemical components of each element in the steel meet the required requirements, Ca wires or Ca-Si wires are fed into the refining furnace after the temperature reaches 1580-. In the patent, the refining slag adopts low alkalinity, the S component is easy to control, the yield of S is high, but the refining slag is not subjected to vacuum treatment, the purity of molten steel is low, and the inclusion control is not facilitated.
The Chinese invention patent application number is 200910063354.X, which discloses a production method of nitrogen and sulfur containing non-quenched and tempered steel, and discloses that refining slag in a refining furnace adopts medium-alkalinity refining slag with alkalinity of 1.5-3.0, and the percentage content of the refining slag is as follows:CaO 40-50%，SiO2 15-20%，Al2O320-25%, MgO 5-10%, and other inevitable oxide impurities. The process route provided by the patent is simple, nitrogen is easily added into steel, and alloy is saved; the S component is easy to control, and the yield of S is high. But the vacuum treatment is not carried out, the purity of the molten steel is low, the inclusion control is not facilitated, and the N is controlled by bottom blowing nitrogen in the refining process, so that the yield of the N is unstable and the risk is high.
A ' narrow component control technology of sulfur in C70S6BY non-quenched and tempered steel ' is disclosed in the modern metallurgy ', a method for carrying out slag washing desulfurization on a C70S6BY non-quenched and tempered steel converter by using high carbon and top slag technology is explained in the paper, and narrow component control of sulfur in C70S6BY steel is accurately realized by adjusting a slag system and subsequent technological measures for controlling soft blowing time through LF. However, the paper adopts premelted refining slag produced after the converter, the early alkalinity of the refining furnace is higher, the slag fluidity is reduced, the slag amount is large, and a large amount of nitrogen and sulfur containing core-spun yarns are fed after RH vacuum treatment, so the operation is complicated, the treatment period is long, and the mass production is not facilitated.
In view of the above-mentioned shortcomings of the prior high-carbon, sulfur-containing, nitrogen-containing and microalloy steel for the engine connecting rod, the development of a steel for the engine connecting rod and a production method thereof are technical problems to be solved urgently in the technical field.
Disclosure of Invention
The invention aims to solve the problem of large S, N content fluctuation in steel, and provides the steel for the engine connecting rod and the preparation method thereof; the whole RH furnace treatment process adopts nitrogen gas drive, so that the whole RH vacuum treatment process can be ensured, and the content of N in steel can not be reduced, thereby accurately controlling the content of N in steel; the produced steel has proper structure and inclusion form and good comprehensive performance.
The invention is realized by the following technical scheme:
the invention relates to steel for an engine connecting rod, which comprises the following chemical components in percentage by mass: 0.69-0.73% of C, 0.15-0.25% of Si, 0.55-0.60% of Mn, less than or equal to 0.045% of P, 0.060-0.070% of S, 0.10-0.15% of Cr, 0.04-0.08% of Ni, 0.030-0.040% of V, less than or equal to 0.010% of Al, 0.0120-0.0160% of N, less than or equal to 0.0020% of O, and the balance of Fe and inevitable impurities; the production process route is as follows: converter smelting → LF refining furnace refining → RH vacuum furnace refining → continuous casting → rolling → slow cooling.
Preferably, the chemical components and the mass percentage thereof of the invention are as follows: 0.70% of C, 0.18% of Si, 0.57% of Mn, 0.022% of P, 0.064% of S, 0.13% of Cr, 0.060% of Ni, 0.035% of V, 0.004% of Al, 0.0155% of N, 0.0016% of O, and the balance of Fe and inevitable impurities.
The performance parameters of the steel for the engine connecting rod are as follows: rm 900 minus one 1050MPa, ReL is more than or equal to 550MPa, A is more than or equal to 10 percent, Z is more than or equal to 20 percent, and Brinell hardness HB 280 minus one 310.
The invention discloses a production method of steel for an engine connecting rod, which comprises the following steps:
(1) smelting in a converter
Firstly, controlling 0.20-0.40% of C, less than or equal to 0.025% of P and 1600 ℃ of tapping temperature T =1560 and slag stopping by adopting a sliding plate at the smelting end point;
adding aluminum ingots into the molten steel in the tapping process, wherein the adding amount of the aluminum ingots in each ton of the molten steel is 2.5-3.0Kg, and other elements are added according to the requirements of chemical components;
(2) LF refining
Firstly, making low-alkalinity slag in a refining furnace, controlling the alkalinity to be 1.2-2.0, wherein the refining slag comprises 35-45% of CaO and SiO by weight2 25-30%，Al2O310-15%, MgO 5-13%, and other inevitable oxide impurities;
keeping the white slag for more than or equal to 15min, adding ferrous sulfide to adjust the S content to 0.062-0.068% according to the S content in the molten steel, and hoisting the S into an RH vacuum furnace;
(3) refining in RH vacuum furnace
The whole RH vacuum treatment process adopts nitrogen gas drive, and the flow rate is 80-100 Nm3The retention time of the ultimate vacuum degree (less than 67 Pa) is more than or equal to 10 min;
adding 1.2 Kg/t ferrosilicon nitride, returning to a four-stage pump, circulating for 5-10 min, controlling the N content to be 0.0120-0.0160%, adding a covering agent, and carrying out bale lifting until continuous casting;
(4) continuous casting
The superheat degree of the tundish molten steel is less than or equal to 25 ℃, a continuous casting process of an electromagnetic stirring and weak cooling system is adopted, the electromagnetic stirring current is 400A, and the frequency is 3.5 Hz; the cooling water quantity of the crystallizer is 150-160 m3The specific water amount of the secondary cooling water is 0.8-1.0L/Kg, the billet drawing speed of the 200-square continuous casting billet is 1.2-1.4 m/min, the straightening temperature of the continuous casting billet is 950-plus-material 1000 ℃, and the casting billet enters a pit for slow cooling for 48 hours after being cut, so that a high-temperature embrittlement region is avoided, and the stress is eliminated;
(5) rolled steel
The temperature of the preheating zone is less than or equal to 850 ℃, the temperature of the heating zone is 1140-1190 ℃, the temperature of the soaking zone is 1130-1180 ℃, and the total heating time is more than or equal to 130 min; the opening angle of the cooling bed heat-insulating cover is 30 degrees, the stepping speed of the cooling bed is accelerated, and the shearing temperature of steel is guaranteed to be more than or equal to 400 ℃; steel materials are timely put into a pit for slow cooling, the temperature of round steel with the diameter of 50 mm and above entering the pit is guaranteed to be more than or equal to 400 ℃, the temperature of round steel with the diameter of 50 mm below entering the pit is guaranteed to be more than or equal to 350 ℃, a slow cooling cover is covered at the first time, and the slow cooling time is more than or equal to 36 hours, so that the steel materials can be dug.
The reasons for the production process of the present invention are as follows:
according to the invention, a large amount of aluminum ingots are added for deoxidation during converter tapping, because Al is the most economic and effective deoxidation element in the steelmaking process, the deoxidation effect is good, the time consumption is short, and the molten steel rephosphorization caused by slag falling in the tapping process can be effectively avoided by adopting the sliding plate to block slag.
The low-alkalinity slag is produced in the LF refining furnace because the S content of the steel for the engine connecting rod is required to be 0.060-0.070%, the S content range is narrow, and the control difficulty is high. And a low-alkalinity slag system is adopted, so that the S content in the whole refining process can be kept relatively stable, and if the S content is lower than a target, ferrous sulfide is added to increase the S content.
The invention adopts nitrogen gas to drive in the whole RH vacuum treatment process because the content of N in the steel for the engine connecting rod is required to be 0.0120-0.0160 percent. The control difficulty of the N element is very high, the nitrogen is adopted for driving, the pump is withdrawn and then circulated for a certain time, the whole RH vacuum treatment process can be ensured, the N content in the steel can not be reduced, and the guarantee is provided for the accurate control of the N content of the finished product.
The invention adopts the continuous casting process of low superheat degree pouring, electromagnetic stirring and weak cooling system, and the casting blank is slowly cooled for more than 36h in a pit, because the C content of the steel is 0.69-0.73%, the high-carbon steel is easy to generate carbon segregation, the S, N content is high, and the casting blank is easy to generate cracks and even seriously cracked in the conventional air cooling process.
The invention controls the heating temperature of the casting blank to be 1130-.
The steel is slowly cooled in the pit after being rolled, because a bainite structure is formed if the cooling speed after rolling is high, the process window of downstream user processing is greatly reduced, the hardness exceeds the standard, and the risk of cracks and even breakage is generated due to superposition of thermal stress and structural stress.
According to the invention, aluminum ingots are added for pre-deoxidation in the converter tapping process, and low-alkalinity slag (1.2-2.0) is produced in the LF refining furnace in the whole process; the whole RH vacuum treatment process adopts nitrogen gas drive, and the flow rate is 80-100 Nm3And h, keeping the ultimate vacuum degree (less than 67 Pa) for more than or equal to 10 min, adding the nitrogen-containing alloy, returning to a four-stage pump, circulating for 5-10 min, and accurately controlling the S content and the N content in the steel. The superheat degree of the continuous casting molten steel is less than or equal to 25 ℃, a continuous casting process of an electromagnetic stirring and weak cooling system is adopted, the casting blank enters a pit for slow cooling for 48 hours after being cut, a high-temperature embrittlement region is avoided, and stress is eliminated. The temperature of a preheating zone of steel rolling is less than or equal to 850 ℃, the temperature of a heating zone is 1140-1190 ℃, the temperature of a soaking zone is 1130-1180 ℃, and the total heating time is more than or equal to 130 min; the opening angle of the cooling bed heat-insulating cover is 30 degrees, the stepping speed of the cooling bed is accelerated, and the shearing temperature of steel is ensured to be more than or equal to 400 ℃. Steel materials are timely put into a pit for slow cooling, the temperature of round steel with the diameter of 50 mm and above entering the pit is guaranteed to be more than or equal to 400 ℃, the temperature of round steel with the diameter of 50 mm below entering the pit is guaranteed to be more than or equal to 350 ℃, a slow cooling cover is covered at the first time, and the slow cooling time is more than or equal to 36 hours, so that the steel materials can be dug. The steel of the invention is ensured to have proper structure and inclusion shape and good comprehensive performance.
Drawings
FIG. 1 is an elemental analysis of a manganese sulfide inclusion in a steel product produced in example 1 of the present invention;
FIG. 2 is a morphological analysis of a manganese sulfide inclusion in a steel product produced in accordance with example 1 of the present invention;
FIG. 3 is an elemental analysis of composite inclusions in a steel product produced in example 1 of the present invention;
FIG. 4 is a morphological analysis of composite inclusions in a steel product produced in example 1 of the present invention;
FIG. 5 is metallographic structure analysis of round steel of 55mm in diameter produced in example 1 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to examples to facilitate the clear understanding of the present invention, but the present invention is not limited thereto.
Example 1
The steel for the engine connecting rod comprises the following chemical components in percentage by mass: 0.70% of C, 0.18% of Si, 0.57% of Mn, 0.022% of P, 0.064% of S, 0.13% of Cr, 0.060% of Ni, 0.035% of V, 0.004% of Al, 0.0155% of N, 0.0016% of O, and the balance of Fe and inevitable impurities.
The production method of the steel for the engine connecting rod comprises the following steps:
(1) smelting in a converter
Firstly, controlling 0.25 percent of C, 0.018 percent of P and 1580 percent of tapping temperature T at the end point of smelting, and pushing off slag by adopting a sliding plate;
adding 2.8 Kg of aluminum ingot into molten steel during tapping, and adding other elements according to the chemical component requirements, wherein the adding amount of the aluminum ingot in each ton of molten steel is 2.8 Kg;
(2) LF refining
Making low-alkalinity slag in a refining furnace, controlling the alkalinity to be 1.5, wherein the refining slag comprises 42 percent of CaO and SiO in percentage by weight2 28 %，Al2O312%, MgO 9%, and the balance being unavoidable oxide impurities;
secondly, keeping the white slag for 15min, adding ferrous sulfide to adjust the S content to 0.064% according to the S content in the molten steel, and hoisting the S into an RH vacuum furnace;
(3) refining in RH vacuum furnace
The whole RH vacuum treatment process adopts nitrogen gas drive, and the flow rate is 90 Nm3H, ultimate vacuum (Small)At 67 Pa) for 12 min;
adding 1.2 Kg/t of ferrosilicon nitride, returning to a four-stage pump, circulating for 5min, controlling the N content to be 0.0155%, adding a covering agent, and hoisting to continuously cast;
(4) continuous casting
The superheat degree of the tundish molten steel is 20 ℃, a continuous casting process of an electromagnetic stirring and weak cooling system is adopted, the electromagnetic stirring current is 400A, and the frequency is 3.5 Hz; the cooling water quantity of the crystallizer is 155 m3The specific water amount of the secondary cooling water is 0.85L/Kg, the billet drawing speed of a 200-square continuous casting billet is 1.2 m/min, the straightening temperature of the continuous casting billet is 980 ℃, the continuous casting billet enters a pit for slow cooling for 48 hours after being cut, a high-temperature embrittlement area is avoided, and the stress is eliminated;
(5) rolled steel
The preheating zone temperature is 750 ℃, the heating zone temperature is 1160 ℃, the soaking zone temperature is 1150 ℃ and the total heating time is 135 min; the opening angle of the cooling bed heat preservation cover is 30 degrees, the shearing temperature of rolled round steel with the diameter of 55mm is 480 ℃, the pit entering temperature is 420 ℃, the slow cooling cover is covered at the first time, and the pit can be dug in 40 hours after slow cooling.
Example 1 as the best embodiment of the present invention, low basicity slag is manufactured by an LF refining furnace, and the S content in steel is precisely controlled. The RH vacuum furnace adopts methods of nitrogen driving, pump withdrawal circulation and the like, accurately controls the content of N in steel, and greatly reduces inclusions in the steel. The continuous casting adopts low superheat degree pouring, and segregation is reduced. The heating temperature of the rolled steel is controlled within a narrow range, and the rolled steel enters a pit for slow cooling after being rolled, so that the uniform structure is ensured, the generation of abnormal structures and cracks is avoided, and the cutting performance and the fatigue performance of the material are improved.
The steel produced in this example has the following performance parameters: rm 1002 MPa, 1004 MPa, ReL 590 MPa, 592 MPa, A12.0%, Z24%, 23.5%, Brinell hardness HB 289, 292, the hot rolled structure morphology obtained is pearlite and ferrite, the inclusions are manganese sulfide and composite inclusions.
The manganese sulfide in the steel produced in this example was subjected to elemental analysis and morphological analysis, see fig. 1 and 2. As can be seen from FIG. 1, the main component of the inclusions in the steel material is manganese sulfide; as can be seen from FIG. 2, the manganese sulfide is distributed in the steel in an interrupted strip shape, the length of the inclusion is 10-75 μm, and a small amount of manganese sulfide is in a spindle shape, which is beneficial to improving the cutting processing performance of the steel. The composite inclusions in the steel of this example were further subjected to elemental analysis and morphological analysis, see fig. 3 and 4. As can be seen from fig. 3 and 4, the composite inclusion is formed by oxide inclusions as nucleation sites and being encapsulated by sulfides. It has a wrapping effect on oxide inclusions, and is beneficial to improving the fatigue performance of the material. In addition, the round steel with the specification of phi 55mm produced in the embodiment is subjected to metallographic structure analysis, and referring to fig. 5, as can be seen from fig. 5, the hot rolled structure of the steel produced in the embodiment is pearlite + a small amount of ferrite, which is more favorable for the expansion fracture processing of the connecting rod.
Example 2
Referring to example 1 of the present invention, the present invention also performed four other examples, while one comparative example was performed according to the conventional process, chemical composition lists in examples 1 to 5 and comparative example 1 are shown in table 1 below, process parameter lists in examples 1 to 5 and comparative example 1 are shown in table 2 below, and performance test results of the steel materials prepared using the chemical compositions in table 1 and the process parameters in table 2, respectively, are shown in table 3 below.
TABLE 1 chemical composition of examples of the invention and comparative examples
TABLE 2 Key Process parameters for the examples of the invention and comparative examples
TABLE 3 List of the results of the performance, texture and inclusion detection analysis of each example of the present invention and comparative example
Description of the drawings: in Table 3, the mechanical properties and the normalized properties of hardness are shown at 1050 ℃ for 0.5 hour. Rm: 900-1050MPa, ReL: 550MPa or more, A10% or more, Z20% or more, Brinell hardness HB: 280 to 310.
As can be seen from tables 1 and 2, the control ranges of the components of examples 1 to 5 of the present invention are narrow, and especially the S and N contents are extremely stable, compared to the conventional mode, i.e., comparative examples 1 to 3. In the LF refining of the embodiments 1 to 5 of the invention, low-alkalinity slag is adopted, the S content in steel is stably controlled, and the RH vacuum furnace refining adopts the refining with the flow rate of 90 Nm3Nitrogen gas driving around/h ensures that the fluctuation range of N in the steel is within 20 ppm. In contrast to comparative examples 1-3, the refining furnace used high-basicity slag, the S content in steel fluctuated greatly (0.058-0.072%), while the RH vacuum furnace refining did not use nitrogen gas to drive, the N content in steel could not be stably controlled, and the fluctuation range was large (0.0115-0.0172%).
As can be seen from Table 3, the hot rolled structures of examples 1 to 5 of the present invention are pearlite + ferrite, and have no abnormal structure, and the inclusions are mainly manganese sulfide + composite inclusions. Compared with the traditional mode, the steel structure and inclusion form are beneficial to the expansion-fracture processing of the connecting rod, and have better cutting performance and fatigue performance. The hot rolling structure of the comparative examples 1 to 3 is pearlite + bainite + ferrite, the inclusions are mainly manganese sulfide + alumina + spherical oxide, and the bainite exists in the structure, so that the cutting performance of the steel is reduced, the inclusions are scattered and have no marks, and the fatigue life of the steel is seriously influenced.
The connecting rod is used as an important part of an engine and bears high periodic impact force, inertia force and bending force during working. The quality of the connecting rod manufacture directly affects the performance and reliability of the engine, which requires that the connecting rod have high strength, toughness and fatigue resistance, as well as high machining accuracy. The steel for the engine connecting rod produced by the method has the advantages of strong process reliability, stable steel quality, suitability for mass production and obvious advantages.
The embodiments of the present invention are merely preferred examples, and are not intended to limit the scope of the claims.
Claims (4)
1. The steel for the engine connecting rod is characterized by comprising the following chemical components in percentage by mass: 0.69-0.73% of C, 0.15-0.25% of Si, 0.55-0.60% of Mn, less than or equal to 0.045% of P, 0.060-0.070% of S, 0.10-0.15% of Cr, 0.04-0.08% of Ni, 0.030-0.040% of V, less than or equal to 0.010% of Al, 0.0120-0.0160% of N, less than or equal to 0.0020% of O, and the balance of Fe and inevitable impurities; the production process route is as follows: converter smelting → LF refining furnace refining → RH vacuum furnace refining → continuous casting → rolling → slow cooling.
2. The steel for the engine connecting rod as claimed in claim 1, wherein the steel comprises the following chemical components in percentage by mass: 0.70% of C, 0.18% of Si, 0.57% of Mn, 0.022% of P, 0.064% of S, 0.13% of Cr, 0.060% of Ni, 0.035% of V, 0.004% of Al, 0.0155% of N, 0.0016% of O, and the balance of Fe and inevitable impurities.
3. The steel for an engine connecting rod according to claim 1 or 2, wherein the performance parameters of the steel are: rm 900 minus one 1050MPa, ReL is more than or equal to 550MPa, A is more than or equal to 10 percent, Z is more than or equal to 20 percent, and Brinell hardness HB 280 minus one 310.
4. The production method of a steel for an engine connecting rod as set forth in claim 1 or 2, characterized by comprising the steps of:
(1) smelting in a converter
Firstly, controlling 0.20-0.40% of C, less than or equal to 0.025% of P and 1600 ℃ of tapping temperature T =1560 and slag stopping by adopting a sliding plate at the smelting end point;
adding aluminum ingots into the molten steel in the tapping process, wherein the adding amount of the aluminum ingots in each ton of the molten steel is 2.5-3.0Kg, and other elements are added according to the requirements of chemical components;
(2) LF refining
Firstly, making low-alkalinity slag in a refining furnace, controlling the alkalinity to be 1.2-2.0, wherein the refining slag comprises 35-45% of CaO and SiO by weight2 25-30%，Al2O310-15%, MgO 5-13%, and other inevitable oxide impurities;
keeping the white slag for more than or equal to 15min, adding ferrous sulfide to adjust the S content to 0.062-0.068% according to the S content in the molten steel, and hoisting the S into an RH vacuum furnace;
(3) refining in RH vacuum furnace
The whole RH vacuum treatment process adopts nitrogen gas drive, and the flow rate is 80-100 Nm3The retention time of the ultimate vacuum degree (less than 67 Pa) is more than or equal to 10 min;
adding 1.2 Kg/t ferrosilicon nitride, returning to a four-stage pump, circulating for 5-10 min, controlling the N content to be 0.0120-0.0160%, adding a covering agent, and carrying out bale lifting until continuous casting;
(4) continuous casting
The superheat degree of the tundish molten steel is less than or equal to 25 ℃, a continuous casting process of an electromagnetic stirring and weak cooling system is adopted, the electromagnetic stirring current is 400A, and the frequency is 3.5 Hz; the cooling water quantity of the crystallizer is 150-160 m3The specific water amount of the secondary cooling water is 0.8-1.0L/Kg, the billet drawing speed of the 200-square continuous casting billet is 1.2-1.4 m/min, the straightening temperature of the continuous casting billet is 950-plus-material 1000 ℃, and the casting billet enters a pit for slow cooling for 48 hours after being cut, so that a high-temperature embrittlement region is avoided, and the stress is eliminated;
(5) rolled steel
The temperature of the preheating zone is less than or equal to 850 ℃, the temperature of the heating zone is 1140-1190 ℃, the temperature of the soaking zone is 1130-1180 ℃, and the total heating time is more than or equal to 130 min; the opening angle of the cooling bed heat-insulating cover is 30 degrees, the stepping speed of the cooling bed is accelerated, and the shearing temperature of steel is guaranteed to be more than or equal to 400 ℃; steel materials are timely put into a pit for slow cooling, the temperature of round steel with the diameter of 50 mm and above entering the pit is guaranteed to be more than or equal to 400 ℃, the temperature of round steel with the diameter of 50 mm below entering the pit is guaranteed to be more than or equal to 350 ℃, a slow cooling cover is covered at the first time, and the pit can be formed when the slow cooling time is more than or equal to 36 hours.
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