CN104946999A - Low alloy steel for forging steel products and crankshaft - Google Patents
Low alloy steel for forging steel products and crankshaft Download PDFInfo
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- CN104946999A CN104946999A CN201510048376.4A CN201510048376A CN104946999A CN 104946999 A CN104946999 A CN 104946999A CN 201510048376 A CN201510048376 A CN 201510048376A CN 104946999 A CN104946999 A CN 104946999A
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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
- 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
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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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
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
- F16C3/00—Shafts; Axles; Cranks; Eccentrics
- F16C3/04—Crankshafts, eccentric-shafts; Cranks, eccentrics
- F16C3/06—Crankshafts
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- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- General Engineering & Computer Science (AREA)
- Ocean & Marine Engineering (AREA)
- Shafts, Cranks, Connecting Bars, And Related Bearings (AREA)
- Heat Treatment Of Steel (AREA)
- Forging (AREA)
- Heat Treatment Of Articles (AREA)
Abstract
The invention provides low alloy steel for forging steel products, the low alloy steel is excellent in cutability, and the yield strength and the toughness of the low alloy steel can meet requirements of large-scale forging steel products. The low alloy steel for forging steel products comprises, by mass, 0.30 % to 0.40 % of C, 0 % to 0.45 % of Si, 0.50 % to 1.90 % of Mn, 0.70 % to 2.00 % of Ni, 1.00 % to 2.30 % of Cr, 0 % to 0.35 % of Mo, 0 % to 0.20 % of V, and the reminder comprising Fe and inevitable impurities, more than 17 % of bainite structure, martensitic structure or composite structure of bainite structure and martensitic structure, and the balance being pearlitic structure, ferritic structure or composite structure of pearlitic structure and ferritic structure, wherein the components meet that (1.5*Mn+2*Ni)/Cr < than 2.35 (1).
Description
Technical field
The present invention relates to forged steel goods low alloy steel and crank axle.
Background technology
The steel that the large-scale crank axle of the transmission component of the diesel engine used as boats and ships and generator is used, in order to the output rating realizing diesel engine improves and miniaturization, require high strength.
To this, develop the forging steel (such as with reference to Japanese Patent No. 4150054 publication) having a kind of crank throw of combined crank axle to use.
, combined crank axle is crank throw by being obtained by shaping forged steel goods steel and crank journal shrunk fit and combine and manufacture.Therefore, in the running of diesel engine, skid in order to avoid this shrunk fit portion, the forged steel goods steel used for crank throw requires high-yield strength (YS).Along with the output rating of diesel engine improves, recently require the high-yield strength that more than 450MPa is such.
But, in the forged steel goods steel employing carbon steel, the yield strength of more than 350MPa, below 380MPa degree can only be obtained.In addition, when use has the forged steel goods steel of the low alloy steel of existing composition, if large-scale, then there is hardening crack, therefore can not be manufactured on the diameter of axle and be greater than the forged steel goods steel that the large-scale combined crank axle of 650mm can use.So, manufacture the yield strength with more than 450MPa, and manufacture the forged steel goods steel difficulty that can be used in large-scale combined crank axle.
In addition, the crank throw that combined crank axle uses and crank journal, after being configured as their shape, can be rebuild by machining, and therefore, the forged steel goods steel used for combined crank axle also requires excellent machinability.
Prior art document
Patent documentation
Patent documentation 1: Japanese Patent No. 4150054 publication
Summary of the invention
The present invention is based on above-mentioned such situation and formed, its object is to, providing a kind of and there is yield strength required by large-sized forging steel work and toughness, and the forged steel goods low alloy steel of excellent in machinability.
In order to solve the invention that above-mentioned problem is formed, a kind of forged steel goods low alloy steel, it has following composition: containing C (carbon): more than 0.30 quality % and at below 0.40 quality %, Si (silicon): be greater than 0 quality % and at below 0.45 quality %, Mn (manganese): more than 0.50 quality % and at below 1.90 quality %, Ni (nickel): more than 0.70 quality % and at below 2.00 quality %, Cr (chromium): more than 1.00 quality % and at below 2.30 quality %, Mo (molybdenum): be greater than 0 quality % and at below 0.35 quality %, V (vanadium): be greater than 0 quality % and in the such basal component of below 0.20 quality %, surplus is Fe (iron) and inevitable impurity, containing bainite structure, martensitic stucture or their complex tissue more than 17%, surplus is pearlitic structure, ferritic structure or their complex tissue, and meet following formula (1).
(1.5×Mn+2×Ni)/Cr＜2.35…(1)
This forged steel goods low alloy steel, by making the content of each composition of steel in above-mentioned scope and meeting above formula (1), containing bainite structure, martensitic stucture or their complex tissue more than 17%, excellent toughness can be obtained thus, and the high-yield strength required by large-sized forging steel work of large-scale crank axle etc. can be guaranteed.In addition, this forged steel goods low alloy steel, by making the composition of steel meet above formula (1), the Cr concentration in the cementite of metal structure becomes large, drag reduction when cutting thus, therefore excellent in machinability.
In addition, in order to solve another invention that above-mentioned problem is formed, be the crank axle manufactured by this forged steel goods low alloy steel.This crank axle owing to being made up of this forged steel goods low alloy steel, so there is high-yield strength and toughness as above-mentioned, and excellent in machinability.
As described above, forged steel goods low alloy steel of the present invention, has the yield strength required by large-sized forging steel work and toughness, and excellent in machinability, be therefore also applicable to the combined large-scale crank axle etc. of boats and ships.
Accompanying drawing explanation
Fig. 1 is the graph representing the bainite structure of embodiment, martensitic stucture or the tissue point rate of their complex tissue and the relation of yield strength
The graph of the relation of torque resistance when Fig. 2 is Mn, Ni and Cr content and the Drilling operation representing embodiment
Embodiment
Below, the embodiment for forged steel goods low alloy steel of the present invention is described.
< metal structure >
In the metal structure of this forged steel goods low alloy steel, the ratio (tissue point rate) of bainite structure, martensitic stucture or their complex tissue is more than 17%, and surplus is pearlitic structure, ferritic structure or their complex tissue.So in metal structure, make the tissue point rate of bainite structure, martensitic stucture or their complex tissue more than above-mentioned lower limit, this forged steel goods low alloy steel has as the required high-yield strength (more than 450MPa) of the combined large-scale crank axle etc. of boats and ships.Also have, tissue as bainite structure, martensitic stucture or their complex tissue divides the measuring method of rate, such as can carry out in the following way, the test film of microstructure observation is cut from forged steel goods low alloy steel, stretch direction along forging and mirror ultrafinish is carried out for the surface of this test film, with nital corrosion, observe with opticmicroscope.
< forms >
About this forged steel goods low alloy steel, there is following composition, containing more than C:0.30 quality % and at below 0.40 quality %, Si: be greater than 0 quality % and at below 0.45 quality %, more than Mn:0.50 quality % at below 1.90 quality %, more than Ni:0.70 quality % at below 2.00 quality %, more than Cr:1.00 quality % at below 2.30 quality %, Mo: be greater than 0 quality % and at below 0.35 quality %, V: be greater than 0 quality % and in the basal component of below 0.20 quality %, surplus is Fe and inevitable impurity, and meet following formula (1).
(1.5×Mn+2×Ni)/Cr＜2.35…(1)
As the lower limit of the C containing ratio of this forged steel goods low alloy steel, be 0.30 quality %, be preferably 0.32 quality %.On the other hand, as the upper limit of the C containing ratio of this forged steel goods low alloy steel, be 0.40 quality %, be preferably 0.39 quality %.If the C containing ratio of this forged steel goods low alloy steel is lower than above-mentioned lower limit, then can not get sufficient hardenability, carry out modified of the process likely can not guaranteeing by carrying out tempering after normalizing and the tissue point rate of the metal structure of sufficient yield strength can be obtained.Otherwise if the C containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then toughness extremely reduces, and the pearlitic generation because improving the stability of cementite during normalizing is promoted, so yield strength likely reduces.By making the C containing ratio of this forged steel goods low alloy steel in above-mentioned scope, hardenability and the yield strength of this forged steel goods low alloy steel can be guaranteed rightly.
As the lower limit of the Si containing ratio of this forged steel goods low alloy steel, for being greater than 0 quality %.On the other hand, as the upper limit of the Si containing ratio of this forged steel goods low alloy steel, be 0.45 quality %, be preferably 0.32 quality %.If the Si containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then toughness is likely impaired.By making the Si containing ratio of this forged steel goods low alloy steel in above-mentioned scope, the hardenability of this forged steel goods low alloy steel can be made to improve, guarantee sufficient toughness.
As the lower limit of the Mn containing ratio of this forged steel goods low alloy steel, be 0.50 quality %, be preferably 0.80 quality %.On the other hand, as the upper limit of the Mn containing ratio of this forged steel goods low alloy steel, be 1.90 quality %, be preferably 1.50 quality %.If the Mn containing ratio of this forged steel goods low alloy steel is lower than above-mentioned lower limit, then can not get sufficient hardenability, can not guarantee by by carrying out modified under this process of tempering after normalizing and the tissue point rate of the metal structure of sufficient yield strength can being obtained, and likely can not get sufficient toughness.Otherwise if the Mn containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then the Cr concentration in cementite reduces, and machinability is likely impaired.By making the Mn containing ratio of this forged steel goods low alloy steel in above-mentioned scope, yield strength and the toughness of this forged steel goods low alloy steel can be guaranteed rightly.
As the lower limit of the Ni containing ratio of this forged steel goods low alloy steel, be 0.70 quality %, be preferably 0.74 quality %.On the other hand, as the upper limit of the Ni containing ratio of this forged steel goods low alloy steel, be 2.00 quality %, be preferably 1.50 quality %.If the Ni containing ratio of this forged steel goods low alloy steel is lower than above-mentioned lower limit, then can not get sufficient hardenability, likely can not guarantee by by carrying out modified under this process of tempering after normalizing and the tissue point rate of the metal structure of sufficient yield strength can being obtained.In addition, if the Ni containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then make the Cr concentration in cementite reduce, machinability is likely impaired.By making the Ni containing ratio of this forged steel goods low alloy steel in above-mentioned scope, hardenability and the intensity of this forged steel goods low alloy steel can be guaranteed rightly.
As the lower limit of the Cr containing ratio of this forged steel goods low alloy steel, be 1.00 quality %, be preferably 1.40 quality %.On the other hand, as the upper limit of the Cr containing ratio of this forged steel goods low alloy steel, be 2.30 quality %, be preferably 2.10 quality %.If the Cr containing ratio of this forged steel goods low alloy steel is lower than above-mentioned lower limit, then can not get sufficient hardenability, can not guarantee, by by carrying out modified under this process of tempering after normalizing and the tissue point rate of the metal structure of sufficient yield strength can being obtained, likely to can not get sufficient intensity.Otherwise if the Cr containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then the ratio of the cementite of metal structure increases, and toughness is likely impaired.By making the Cr containing ratio of this forged steel goods low alloy steel in above-mentioned scope, the hardenability of this forged steel goods low alloy steel, intensity and toughness can be guaranteed rightly.
As the lower limit of the Mo containing ratio of this forged steel goods low alloy steel, be greater than 0 quality %.On the other hand, as the upper limit of the Mo containing ratio of this forged steel goods low alloy steel, be 0.35 quality %, be preferably 0.32 quality %.If the Mo containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then fine carbide generates, and toughness is likely impaired.This forged steel goods low alloy steel contains the Mo of above-mentioned scope, and hardenability improves, and can guaranteeing the tissue point rate by can obtain the metal structure of sufficient yield strength by carrying out modified under this process of tempering after normalizing, can obtain sufficient intensity.
As the lower limit of the V containing ratio of this forged steel goods low alloy steel, be greater than 0 quality %.On the other hand, as the upper limit of the V containing ratio of this forged steel goods low alloy steel, be 0.20 quality %, be preferably 0.10 quality %.If the V containing ratio of this forged steel goods low alloy steel is higher than the above-mentioned upper limit, then fine carbide generates, and toughness is likely impaired.This forged steel goods low alloy steel contains the V of above-mentioned scope, and hardenability improves, and can guaranteeing the tissue point rate by can obtain the metal structure of sufficient yield strength by carrying out modified under this process of tempering after normalizing, obtaining sufficient intensity.
About this forged steel goods low alloy steel, except above-mentioned basal component, containing Fe and inevitable impurity in surplus.In addition, as inevitable impurity, the Cu (copper), the Sn (tin) that such as bring into because of the situation of raw material, goods and materials, producing apparatus etc. can be allowed, As (arsenic), being mixed into of the element of Pb (copper), Ti (titanium) etc.In addition, the composition also on one's own initiative containing other is also effective, and according to the kind of contained composition, the characteristic of forged steel material is further improved.
The relational expression > that < respectively forms
In this forged steel goods low alloy steel, the content of each element meets following formula (1).
(1.5×Mn+2×Ni)/Cr＜2.35…(1)
When the content of each element meets the scope of above formula (1), the more crisp cementite of Cr concentration more than 24% generates.Think that this more crisp cementite generates, can cause drag reduction during cutting, machinability improves.Further, if the Cr concentration in cementite is at least more than 22%, then can obtain the sufficient machinability required by machining of the component of large-scale crank axle.
< mechanical properties >
As the lower limit of the yield strength (YS) of this forged steel goods low alloy steel, be preferably 450MPa, be more preferably 500MPa.If the yield strength of this forged steel goods low alloy steel is more than above-mentioned lower limit, then can manufacture the requirement meeting combined large-scale crank axle, and the diameter of axle is the crank axle of more than 650mm.About the evaluation of yield strength, can by such as carrying out according to the tension test of JIS-Z2241 (2011).
As the lower limit of the absorption energy vE (the absorption energy under room temperature) of this forged steel goods low alloy steel, be preferably 20J, be more preferably 30J.If the absorption of this forged steel goods low alloy steel more than above-mentioned lower limit, then can meet the combined toughness required by large-scale crank axle.Absorb the evaluation of energy, can by such as carry out according to the pendulum impact test of JIS-Z2242 (2005).
The manufacture method > of < forged steel goods low alloy steel and crank axle
About this forged steel goods low alloy steel, such as, by possessing the manufacture method manufacture of melting operation, casting process, heating process, forging process and heat treatment step.In addition, by machining operation, this forged steel goods low alloy steel is processed, thus manufactures this crank axle.
(melting operation)
In melting operation, first, use high frequency melting furnace, electric furnace, converter etc., melting is adjusted to the composition steel of afore mentioned rules.Thereafter, vacuum-treat is implemented to this molten steel, the gaseous constituent of removing O (oxygen), H (hydrogen) etc. and impurity element.
(casting process)
In casting process, use and carried out the steel of composition adjustment through above-mentioned melting operation, casting ingot casting (steel ingot).When large-sized forging steel work steel, the main ingot casting that adopts casts (イ Application go Star ト cast is made), when more small-sized forged steel goods, also can adopt Continuous casting process.
(heating process)
In heating process, heat steel ingot in required time with the temperature specified.If be in low temperature, then the resistance to deformation of material increases, and therefore in order to process in the scope that the deformability of material is good, Heating temperature is such as more than 1150 DEG C.In addition, in order to make the surface of steel ingot and inner homogeneous temperature, need the heat-up time of regulation, heat-up time is such as more than 3 hours.It is generally acknowledged heat-up time and square being directly proportional of the diameter of machined object, heavy section, heated hold time is longer.
(forging process)
In forging process, forge the steel ingot of the temperature being heated to more than 1150 DEG C with heating process.In order to make the casting flaw pressing of shrinkage cavity shrinkage porosity and Micro shrinkage etc., be preferably more than 3S as forging ratio.
(heat treatment step)
At heat treatment step, after carrying out anneal and normalizing treatment, then carry out temper.
First, the anneal of the steel ingot forged is carried out.In anneal, heats forged steel ingot, keeps the specified time (such as more than 5 hours) with the temperature specified (such as more than 250 DEG C, less than 350 DEG C).Afterwards, be heated to more than austenitizing temperature (such as more than 850 DEG C less than 920 DEG C), after keeping the specified time (such as more than 3 hours), Xu Lengzhi specified temperature (such as more than 50 DEG C, less than 200 DEG C).In addition, after above-mentioned cooling, with heat-up rate 30 DEG C/more than hr, 70 DEG C/below hr, be slowly heated to specify temperature (such as more than 500 DEG C, less than 800 DEG C), maintenance certain hour (such as more than 5 hours).
In normalizing treatment, after anneal, cut steel from the forging steel ingot being cooled to room temperature, first, carry out the austenitizing of these steel.Austenitizing is with heat-up rate 30 DEG C/more than hr and 70 DEG C/below hr slowly heats more than Ac3 transformation temperature (830 DEG C), keeps certain hour (such as more than 1 hour).Further, when large-scale steel, because produce the temperature difference during heating inside and outside material, so in order to slowly be heated to austenitizing temperature, making the surface of steel and inner homogeneous temperature, needing to keep certain hour.This hold-time depends on steel diameter, and heavy section more needs to extend.
Secondly, in normalizing treatment, make the temperature of steel reach homogeneous through austenitizing after, cooling steel.As the lower limit of speed of cooling at this moment, be preferably 0.5 DEG C/min, be more preferably 1 DEG C/min.In addition, as the upper limit of above-mentioned speed of cooling, be preferably 8 DEG C/min, be more preferably 5 DEG C/min.If above-mentioned speed of cooling is lower than above-mentioned lower limit, then bainite structure, martensitic stucture or their complex tissue reduce, and likely can not get sufficient yield strength.On the other hand, if above-mentioned speed of cooling is higher than the above-mentioned upper limit, then likely there is crackle due to thermal stresses during cooling and transformation stress.
After above-mentioned cooling, by carrying out temper, this forged steel goods low alloy steel can be obtained.The tempering of steel, with heat-up rate 30 DEG C/more than hr and 70 DEG C/below hr be slowly heated to specify temperature, keep certain hour (such as more than 5 hours).Tempering in order to adjust the balance of intensity, ductility and toughness, and is such as carried out with more than 550 DEG C in order to the internal stress (residual stress) removed because phase transformation produces.But if be in high temperature, then the coarsening of carbide, makes due to the recovery etc. of dislocation structure steel soften, can not guarantee sufficient intensity, therefore be such as less than 650 DEG C.
(machining operation)
After this forged steel goods low alloy steel after heat treatment step is forged into crank throw and crank journal, implements the trimming mechanical workout comprising cutting or grinding, thus the part of this crank axle can be obtained.Then, shrunk fit implements crank throw and the crank journal of trimming mechanical workout, thus can obtain this crank axle.
[embodiment]
Below, illustrate in greater detail the present invention by embodiment, but the present invention does not limit by these embodiments.
(evaluation of steel grade and hardening and tempering method)
First, about steel grade and hardening and tempering method, the suitability just towards large-scale crank axle is evaluated.
(embodiment 1)
In embodiment 1, will there is the steel of the composition shown in table 1, more than 900 DEG C, carry out forge hot between the temperature of less than 1230 DEG C after, be configured as the shape of the crank throw of diameter of axle 950mm by gas cutting.Then, after the crank throw of this shaping is heated to 870 DEG C, cooled by air cooling, carried out normalizing.Again the crank throw of cooling is heated to 620 DEG C, implements tempering.
(comparative example 1 ~ 3)
In comparative example 1 ~ 3, be by have the steel of the composition shown in table 1 more than 900 DEG C, carry out forge hot between the temperature of less than 1230 DEG C after, be configured as the shape of the crank throw of the diameter of axle 620mm, 720mm and 1062mm by gas cutting.Then, after these crank throws be shaped are heated to 870 DEG C, are cooled by air cooling, carry out normalizing.Again the crank throw of cooling is heated to 620 DEG C, implements tempering.
(comparative example 4)
In comparative example 4, being the steel by having the composition shown in table 1, after carrying out forge hot between the temperature of more than 900 DEG C, less than 1230 DEG C, being configured as the shape of the crank throw of diameter of axle 720mm by gas cutting.Then, after the crank throw of this shaping is heated to 870 DEG C, is adjusted to the polymer liquid cooling of the polyalkylene glycol system of 25 quality % by the concentration of the aqueous solution, quenches.Again the crank throw of cooling is heated to 620 DEG C, implements tempering.
[hardening crack evaluation]
Observed by visual inspection and carried out modified crank throw, confirm there is flawless.
[yield strength evaluation]
From the shrunk fit portion neighborhood acquisition test sheet carrying out modified crank throw, implement tension test according to JIS-Z2241 (2011).The shape of test film, according to the 14A test film of JIS-Z2241 (2011), is φ 6 × G.L.30mm, measures yield strength.In this test, more than yield strength 450MPa's is qualified.
In this test, crank throw is unconfirmed to crackle, and yield strength be more than 450MPa be comprehensive evaluation " A ".In addition, yield strength is comprehensive evaluation " B " lower than 450MPa, and what confirm crackle is comprehensive evaluation " C ".The display of these measuring results in Table 1.
[table 1]
[measuring result]
The crank throw of embodiment 1, unconfirmed to hardening crack, and the yield strength of more than 450MPa can be obtained.It can thus be appreciated that the modified steel containing basal component of the present invention and under having carried out implementing this process of tempering after normalizing, can be suitable on large-scale crank axle.
On the other hand, employ the crank throw of the steel of comparative example 1 ~ 3, although unconfirmed to hardening crack, yield strength is low, is far from being and can be applicable to combined large-scale crank axle.
In addition, use the crank throw of the steel of comparative example 4, although the diameter of axle is larger, because quenching, so top layer and inside easily the temperature difference occur, due to the above-mentioned temperature difference produced, thermal stresses or transformation stress occurs during quenching, therefore think and there occurs crackle.
(composition of steel and metal structure evaluation)
Then, the composition of steel and metal structure are evaluated.
(embodiment 2 ~ 5, comparative example 5 ~ 15)
Embodiment 2 ~ 5, comparative example 5 ~ 15, melting has the steel of the composition shown in table 2, manufactures the forged steel goods steel of test.First, use the steel of the composition shown in high-frequency melting furnace table 1, cast the steel ingot of the 40kg of the 230mm of wide 170mm × thick 120mm × high.Then, that excises the steel ingot obtained emitted notch portion, with 1230 DEG C of heating more than 5 hours less than 10 hours.Then, utilize flat-die forging press, the steel ingot of heating is compressed to 1/2 with aspect ratio, make steel ingot medullary ray half-twist and forge, after being stretched to wide 90mm × thick 90mm × long 450mm, letting cool this former material in an atmosphere.Thereafter, the former material being cooled to more than 250 DEG C less than 300 DEG C is kept after more than 10 hours in process furnace, heats with 50 DEG C/hr, keep 5 hours with 870 DEG C.Afterwards, after this former material stove is chilled to more than 100 DEG C less than 150 DEG C, then heat with 50 DEG C/hr, after keeping 15 hours with 650 DEG C, let cool in an atmosphere, implement anneal.
Then, cutting the square stock of wide 20mm × thick 20mm × long 200mm from letting cool to the above-mentioned former material of room temperature, implementing austenitizing process with little type simulated stove.Austenitizing process is that the former material cut (above-mentioned square stock) is warming up to 870 DEG C with 50 DEG C/hr, keeps after 1 hour, makes the average cooling rate of the temperature range of 870 DEG C to 500 DEG C be that 1.0 DEG C/min cools.Thereafter, after above-mentioned former material is cooled to room temperature, as temper, after keeping 10 hours with 620 DEG C, let cool in an atmosphere.Further, this average cooling rate of 1.0 DEG C/min from the temperature range of 870 DEG C to 500 DEG C after above-mentioned austenitizing process is the speed of cooling of the cooling after the normalizing in simulation large-sized forging steel work.
(comparative example 16 ~ 19)
Comparative example 16 ~ 19, uses composition and embodiment 2 ~ 5 be the steel of same composition, and except the average cooling rate of the cooling after making normalizing is except 0.3 DEG C/min, other are all same with the manufacture method of above-described embodiment 2, and manufacture is tested and used former material thus.
(comparative example 20,21)
Comparative example 20,21, is used the steel with the composition shown in table 2, is tested use former material by the manufacture method manufacture same with above-described embodiment 2.Further, the steel used in comparative example 20,21, its composition does not meet above formula (1).
(embodiment 6 ~ 9)
Embodiment 6 ~ 9, uses composition and embodiment 2 ~ 5 be the steel of same composition, and except the average cooling rate of the cooling after making normalizing is except 5.0 DEG C/min, other are all same with the manufacture method of above-described embodiment 2, and manufacture is tested and used former material thus.
(comparative example 22,23)
Comparative example 22,23, uses composition and comparative example 20,21 be the steel of same composition, and except the average cooling rate of the cooling after making normalizing is except 5.0 DEG C/min, other are all same with the manufacture method of above-described embodiment 2, and manufacture is tested and used former material thus.
[measurement of mechanical properties]
Acquisition test sheet from the former material of above-mentioned test manufactured, implements tension test according to JIS-Z2241 (2011).The shape of test film, according to the 14A test film of JIS-Z2241 (2011), is φ 6 × G.L.30mm, measures yield strength (YS).In this test, more than yield strength 450MPa's is qualified.
In addition, measured absorption energy (vE) (absorption energy under room temperature) of the former material of above-mentioned test by pendulum impact test, carry out the evaluation of toughness.Pendulum impact test is implemented according to JIS-Z2242 (2005), and test film shape at this moment adopts the 2mmV otch of JIS-Z2242 (2005).In this test, absorbing can be qualified for the judgement of more than 20J.
[observation of metal structure]
Cut the test film of metal structure observation from the former material of test, with 3% nital, this test film is corroded, observation by light microscope.Specifically, carry out observing and photographing with the multiplying power of 100 times with opticmicroscope, for the photo of shooting, stamp the grid that 11 row × 11 arrange, count the net point met with bainite structure or martensitic stucture.Then, by the quantity of this net point divided by total-grid number 121, the tissue as the bainite structure in each visual field, martensitic stucture or their complex tissue divides rate (ratio of metal structure).The former material of each test carries out same measurement in 3 visuals field, divides rate using its mean value as the tissue of the bainite structure of each former material, martensitic stucture or their complex tissue.In table 2, this tissue point rate was described as " BM divides rate ".
[concentration analysis of the alloying element in cementite]
The concentration analysis of the alloying element in cementite, by carrying out quantitative analysis to carry out with the EDX of subsidiary scanning electron microscope (SEM).EDX detects the characteristic X-ray occurred by electronbeam irradiation, by carrying out the method for ultimate analysis and compositional analysis with energy light splitting.Further, for the comparative example 5 ~ 8,10,12 ~ 19 of oblique line additional in " in cementite Cr concentration " hurdle in table 2, the concentration analysis of the alloying element in cementite is not implemented.
[machinability evaluation]
As the evaluation of machinability, the experiment with measuring of torque resistance value when Drilling operation carried out for test former material.To on the former material of test of leniently 20mm × thick 20mm × 200mm, using the square stock of length 12mm cut-out as test film, the cut surface for this test film carries out Drilling operation.Use the superhard brill (" 860.1-0500-019A1-PM4234 " of サ ンドビツ Network Co., Ltd.) of φ 5mm, for a test film, bore the hole of opening 2 degree of depth 10mm with 1.Drilling operation is with revolution 4,000rpm, give speed 0.25mm/rev, lubricating oil (carrying out 50 times of dilutions for soluble oil (the ユ シ ロ mono-ケ Application " EC50 " of ユ シ ロ chemical industry Co., Ltd.)) is supplied to Drilling operation portion with the flow of 10L/min and carries out.In machinability is evaluated, measure from boring the mean value contacted with test film to boring the torque resistance of hole during this ending degree of depth 10mm, below 180Ncm is qualified.Further, for the comparative example 5 ~ 8,10,12 ~ 19 at " torque resistance " additional oblique line in hurdle in table 2, the evaluation of machinability is not implemented.
In this test, yield strength, absorb can and machinability be all judged to be that qualified is comprehensive evaluation " A ".In addition, yield strength (YS) is comprehensive evaluation " B " lower than 450MPa, and absorbing (vE) be comprehensive evaluation " C " lower than 20J, and what torque resistance during Drilling operation was greater than 180Ncm is comprehensive evaluation " D ".The display of these measuring results in table 2.
[table 2]
[measuring result]
All yield strength is high for embodiment 2 ~ 9, and toughness and machinability are also excellent, are comprehensive evaluation A.These forged steel goods low alloy steel, can be suitable for as large-scale crank axle.
In contrast, in comparative example 5 ~ 15, yield strength, toughness and machinability at least any one does not meet qualified scope.These test former material, are to use the steel with the composition of the scope not meeting basal component of the present invention to make.Among basal component of the present invention, C, Mn, Ni, Cr are the elements contributing to intensity raising, have (comparative example 5,8,10,12) of the composition of the content lower limit lower than these elements specified in the present invention, and yield strength reduces.In addition, among basal component of the present invention, if C, Si, Cr, Mo, V are the elements that surplus just can damage toughness, have (comparative example 6,7,13,14,15) of the composition of the upper content limit higher than these elements specified in the present invention, toughness reduces.In addition, among basal component of the present invention, if Mn and Ni is superfluous, then the Cr concentration in cementite tissue just reduces, and therefore has (comparative example 9,11) of the composition of the upper content limit higher than these elements specified in the present invention, and machinability reduces.
In comparative example 16 ~ 19, because reduce the average cooling rate of the cooling after normalizing, so the bainite structure tested in former material and martensitic stucture tail off, all unconfirmed to bainite structure and martensitic stucture in the former material of any test.In comparative example 16 ~ 19 because bainite structure and martensitic stucture few, so think that yield strength reduces.
In comparative example 20 and 21, employ the steel that had composition meets the scope of basal component of the present invention, but the content of Mn, Ni and Cr does not meet above formula (1).Therefore, the Cr concentration step-down in cementite, thinks that machinability reduces.
In embodiment 6 ~ 9, because increase the average cooling rate of the cooling after normalizing, so the ratio of the bainite structure tested in former material or martensitic stucture becomes many, testing the whole of the metal structure of former material becomes bainite structure and martensitic stucture.Therefore, the Cr concentration in cementite can not be made to reduce, can say that machinability does not reduce.In addition, in embodiment 6 ~ 9, yield strength ratio embodiment 2 ~ 5 improves, and can saying the average cooling rate in the cooling by controlling after normalizing, yield strength can be made to improve.
In comparative example 22 and 23, because compare comparative example 20 and 21, increase the average cooling rate of the cooling after normalizing, so the ratio of the bainite structure tested in former material or martensitic stucture, more than comparative example 20 and 21.But, because the content of Mn, Ni and Cr does not meet above formula (1), so the Cr concentration in cementite does not improve, can think that machinability does not improve relative to comparative example 20 and 21.
About the measuring result of above-described embodiment 2 ~ 9, comparative example 5 ~ 23, the tissue point rate (BM divides rate) of bainite structure, martensitic stucture or their complex tissue and the relation of yield strength (YS) show in FIG.The diagram of the black circle of Fig. 1 represents the measuring result of embodiment, and dimetric diagram represents the measuring result of comparative example.As shown in Figure 1, the tissue of bainite structure, martensitic stucture or their complex tissue divides rate higher, yield strength has the tendency more improved, if the tissue point rate of bainite structure, martensitic stucture or their complex tissue is more than 17%, then can obtain the high-yield strength of more than 450MPa.
In addition, about the measuring result of above-described embodiment 2 ~ 9, comparative example 9,11,20 ~ 23, the value on the left side of above formula (1) and the relation of torque resistance show in fig. 2.The diagram of the black circle of Fig. 2 represents the measuring result of embodiment, and dimetric diagram represents the measuring result of comparative example.As shown in Figure 2, the value on the left side of above formula (1) is larger, and torque resistance has larger tendency, if the value on the left side of above formula (1) is lower than 2.35, then torque resistance is below 180Ncm, can obtain excellent machinability.
[utilizability in industry]
As described above, this forged steel goods low alloy steel, has the high-yield strength required by large-sized forging steel work and toughness, and excellent in machinability, be therefore applicable to the combined large-scale crank axle etc. of boats and ships.
Claims (2)
1. a forged steel goods low alloy steel, wherein, has following composition: contain
More than C:0.30 quality % and below 0.40 quality %,
Si: be greater than 0 quality % and below 0.45 quality %,
More than Mn:0.50 quality % and below 1.90 quality %,
More than Ni:0.70 quality % and below 2.00 quality %,
More than Cr:1.00 quality % and below 2.30 quality %,
Mo: be greater than 0 quality % and below 0.35 quality %,
V: be greater than 0 quality % and in the basal component of below 0.20 quality %, surplus is Fe and inevitable impurity,
Bainite structure containing more than 17%, martensitic stucture or their complex tissue, surplus is pearlitic structure, ferritic structure or their complex tissue, meets following formula (1),
(1.5×Mn+2×Ni)/Cr＜2.35…(1)。
2. a crank axle, it is manufactured by forged steel goods low alloy steel according to claim 1.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2014070215A JP2015190040A (en) | 2014-03-28 | 2014-03-28 | Low alloy steel for steel forging and crank shaft |
| JP2014-070215 | 2014-03-28 |
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| Publication Number | Publication Date |
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| CN104946999A true CN104946999A (en) | 2015-09-30 |
| CN104946999B CN104946999B (en) | 2018-01-30 |
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| CN201510048376.4A Expired - Fee Related CN104946999B (en) | 2014-03-28 | 2015-01-30 | Forge steel part low-alloy steel and crank axle |
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| Country | Link |
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| JP (1) | JP2015190040A (en) |
| KR (1) | KR101647920B1 (en) |
| CN (1) | CN104946999B (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108149154A (en) * | 2017-12-01 | 2018-06-12 | 宝鼎科技股份有限公司 | High-voltage motor highly stressed rotor forging shaft and heat treatment processing method |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| JP7127999B2 (en) | 2017-03-27 | 2022-08-30 | 株式会社神戸製鋼所 | Steel for forgings, forged steel crank throws and forged journals for assembled crankshafts |
| CN107937829B (en) * | 2017-12-01 | 2020-10-02 | 宝鼎科技股份有限公司 | High-strength rotor shaft forging for high-voltage motor and heat treatment method |
| CN112342437A (en) * | 2020-11-20 | 2021-02-09 | 宁波北理汽车科技股份有限公司 | Crankshaft connecting rod preparation process |
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| JP2004225128A (en) * | 2003-01-24 | 2004-08-12 | Kobe Steel Ltd | Steel for forging, and forging obtained by using the same |
| CN101443463A (en) * | 2006-06-21 | 2009-05-27 | 株式会社神户制钢所 | Steel for forging, process for producing the same, and forged article |
| CN101910438A (en) * | 2007-12-26 | 2010-12-08 | Posco公司 | Hot rolled steel sheet having superior hot press forming property and high tensile strength, formed article using the steel sheet and method for manufacturing the steel sheet and the formed article |
| WO2013117953A1 (en) * | 2012-02-10 | 2013-08-15 | Ascometal | Process for making a steel part, and steel part so obtained |
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| JPH04150054A (en) | 1990-10-12 | 1992-05-22 | Nec Corp | Processing method for polyimide film |
| JP3663170B2 (en) * | 2000-11-22 | 2005-06-22 | 株式会社神戸製鋼所 | High-strength forging steel and large crankshaft for ships using the same |
| JP4332070B2 (en) * | 2004-06-01 | 2009-09-16 | 株式会社神戸製鋼所 | High strength steel and crankshaft for large steel products |
| JP5859384B2 (en) * | 2012-06-06 | 2016-02-10 | 株式会社神戸製鋼所 | Large high strength forged steel |
-
2014
- 2014-03-28 JP JP2014070215A patent/JP2015190040A/en active Pending
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2015
- 2015-01-30 CN CN201510048376.4A patent/CN104946999B/en not_active Expired - Fee Related
- 2015-03-26 KR KR1020150042163A patent/KR101647920B1/en active IP Right Grant
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1163942A (en) * | 1996-02-08 | 1997-11-05 | 阿斯克迈塔尔公司 | Steel for manufacture of forging and process for manufacturing forging |
| JP2004225128A (en) * | 2003-01-24 | 2004-08-12 | Kobe Steel Ltd | Steel for forging, and forging obtained by using the same |
| CN101443463A (en) * | 2006-06-21 | 2009-05-27 | 株式会社神户制钢所 | Steel for forging, process for producing the same, and forged article |
| CN101910438A (en) * | 2007-12-26 | 2010-12-08 | Posco公司 | Hot rolled steel sheet having superior hot press forming property and high tensile strength, formed article using the steel sheet and method for manufacturing the steel sheet and the formed article |
| WO2013117953A1 (en) * | 2012-02-10 | 2013-08-15 | Ascometal | Process for making a steel part, and steel part so obtained |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108149154A (en) * | 2017-12-01 | 2018-06-12 | 宝鼎科技股份有限公司 | High-voltage motor highly stressed rotor forging shaft and heat treatment processing method |
| CN108149154B (en) * | 2017-12-01 | 2019-12-10 | 宝鼎科技股份有限公司 | High-strength rotor shaft forging for high-voltage motor and heat treatment processing method |
Also Published As
| Publication number | Publication date |
|---|---|
| KR20150112865A (en) | 2015-10-07 |
| JP2015190040A (en) | 2015-11-02 |
| CN104946999B (en) | 2018-01-30 |
| KR101647920B1 (en) | 2016-08-11 |
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