CN101029373A - Preharden steel with excellent cutting performance and toughness and manufacturing method therefor - Google Patents
Preharden steel with excellent cutting performance and toughness and manufacturing method therefor Download PDFInfo
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- CN101029373A CN101029373A CNA2007100842071A CN200710084207A CN101029373A CN 101029373 A CN101029373 A CN 101029373A CN A2007100842071 A CNA2007100842071 A CN A2007100842071A CN 200710084207 A CN200710084207 A CN 200710084207A CN 101029373 A CN101029373 A CN 101029373A
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—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
- 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
- C21D2211/002—Bainite
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Abstract
The present invnetion provides a prehardened steel excellent in cutting performance, toughness and hardness, and used for metal molds for plastics forming, and a processing for pruducing same. Said prehardened steel is a tool steel, contains, based on weight %, the following components: C: 0.05-0.17%; Si: less than 0.6%; Mn: 0.5-2.0%; Ni: 2.5-3.5%; Cr: less than 2.0%; one or two of W and Mo(1/2W+Mo): less than 0.7%; Al: 0.5-1.5%; Cu: 0.7-2.5%; and has a mixing tissue of an upper bainite and a lower bainite, preferably a mixing tissue with 20-80% by area of the lower bainite; with a hardness of 34-45 HRC. It is allowable to replace the Fe part with less than 0.3% of S. The manufacturing method comprising the steps of heating the tool steel having the components mentioned above to austenitic area, executing upper/lower mixing bainite generating heating treatment for cooling the mixing area of the upper bainite and the lower bainite, after that, executing a tempering treatment for generating a hardness of 34-45 HRC.
Description
Technical field
The present invention relates to have extremely excellent machinability, also have concurrently toughness and hardness new pre-hardening type, be mainly used in plastics forming metal die with steel and manufacture method thereof.
Background technology
The perhardened steel that uses mainly as the metal mold for plastic shaping tool from the fabrication cycle that shortens metal die etc. with improve the viewpoint in work-ing life, when requiring machinability, also requires the toughness of excellent intensity, wearability, appropriateness.But these desired characteristics are opposite character, also can not obtain all fully to satisfy the steel of above-mentioned each characteristic.
For above-mentioned requirements, for example, propose to have to low that C-Mn-Ni-Mo (W)-Cu-Al is an alloy, have machinability and toughness (with reference to patent documentation 1) by making grain size number concurrently in the scope of granularity numbering 4～6.The tissue of this steel mainly by making the C step-down be adjusted to uniform top bainite structure, is guaranteed machinability by this top bainite structure.On the other hand, the present patent application people has proposed mainly by making Mn amount suitableization be adjusted to uniform bottom bainite structure, and formation has machinability and flexible concurrently and hangs down that C-Mn-Ni-Mo (W)-Gao Cu-Al is alloy (with reference to a patent documentation 2).
Patent documentation 1 spy opens flat 05-070887 communique
Patent documentation 2 spies open flat 07-278737 communique
Above-mentioned motion has proposed respectively improving a kind of method that plastics forming is made contributions with the performance of perhardened steel.Though but but the top bainite structure excellent in machinability toughness of patent documentation 1 is also insufficient.On the other hand, though the bottom bainite structure tenacity excellent machinability of patent documentation 2 has some poor, also insufficient.So,, shorten the metal die fabrication cycle and improve aspect the requiring of work-ing life the leeway of improving characteristic in addition fully satisfying with in the steel at existing metal die.
Summary of the invention
The objective of the invention is to according to above-mentioned requirements, provide a kind of and can reach the fabrication cycle that shortens metal die simultaneously and improve work-ing life, particularly be suitable for most the perhardened steel and the manufacture method thereof of metal mold for plastic shaping tool.
The present inventor is that alloy or low C-Mn-Ni-(Mo, W)-Gao Cu-Al are that the composition of alloy and tissue and machinability and flexible are when concerning scrutinizing low C-Mn-Ni-(Mo, W)-Cu-Al, discovery is not to be to improve top bainite structure or the bottom bainite structure that machinability is considered to necessary tissue, but be adjusted into the mixed structure of top bainite and bottom bainite, can further improve machinability thus, obtain having concurrently excellent machinability and flexible perhardened steel.
Promptly, the present invention is the perhardened steel of a kind of machinability and tenacity excellent, it is characterized in that, it is a kind of tool steel, in quality %, contain: C:0.05～0.17%, Si:0.6% are following, Mn:0.5～2.0%, Ni:2.5～3.5%, Cr:2.0% are following, W and Mo one or both (1/2W+Mo): below 0.7%, Al:0.5～1.5%, Cu:0.7～2.5%, tissue is the mixed structure of top bainite and bottom bainite.
The perhardened steel of this machinability and tenacity excellent, it is characterized in that, be preferably in quality %, has following composition, contain: C:0.05～0.17%, Si:0.6% are following, Mn:0.5～2.0%, Ni:2.5～3.5%, Cr:0.3～0.8%, W and Mo one or both (1/2W+Mo): below 0.7%, Al:0.5～1.5%, Cu:1.2～1.8%, surplus is made of Fe and unavoidable impurities, and tissue is the mixed structure of top bainite and bottom bainite.
In addition, other inventions of the present invention are perhardened steels of a kind of machinability and tenacity excellent, are essentially consist with any of above-mentioned steel, with the part of the following replacement of fe of S:0.3%, and make the mixed structure of tissue formation top bainite and bottom bainite.
The perhardened steel of machinability of the present invention and tenacity excellent is characterized in that, preferred in above-mentioned steel of the present invention, the mixed structure of its top bainite and bottom bainite is 20～80% in area % bottom bainite.Perhaps, the perhardened steel of machinability of the present invention and tenacity excellent is characterized in that, and then hardness is 34～45HRC.
And, manufacture method of the present invention is the manufacture method of the perhardened steel of machinability and tenacity excellent, it is characterized in that, be after following tool steel is heated to austenite region, carry out generating thermal treatment to the mixing region of top bainite and bottom bainite refrigerative upper/lower mixed with bainite, this tool steel contains in quality %: C:0.05～0.17%, below the Si:0.6%, Mn:0.5～2.0%, Ni:2.5～3.5%, below the Cr:2.0%, one or both of W and Mo (1/2W+Mo): below 0.7%, Al:0.5～1.5%, Cu:0.7～2.5%.Also can use the part of the following replacement of fe of S:0.3%.Having carried out preferably carrying out tempering after the upper/lower mixed with bainite generates thermal treatment, form the hardness of 34～45HRC.
(invention effect)
Steel of the present invention has the machinability and the toughness of the not available high-caliber excellence of existing perhardened steel concurrently.Therefore, do not make other characteristic that very big deterioration be arranged, and reach the prolongationization of the life tools that plastics forming for example uses very effectively.In addition, steel of the present invention is because the toughness height, so even also be difficult to crack, be particularly suitable for carrying out more high-precision metal die processing under the effect of the thermal stresses that the processing along with metal die etc. produces.
Description of drawings
Fig. 1 is the photo of an example of expression microstructure of metals of the present invention (* 400 times).
Fig. 2 is the photo of an example of expression microstructure of metals of the present invention (* 400 times).
Fig. 3 is the photo of an example of the microstructure of metals (* 400 times) of expression comparative example.
Fig. 4 is the photo of an example of the microstructure of metals (* 400 times) of expression comparative example.
Embodiment
A feature that forms trunk of the present invention is in the perhardened steel of low C-Mn-Ni-(Mo, W)-Cu-Al system or low C-Mn-Ni-(Mo, W)-Gao Cu-Al system, makes tissue form the mixed structure of top bainite and bottom bainite.
As above-mentioned, with existing low C-Mn-Ni-(Mo, W)-Cu-Al is that alloy or low C-Mn-Ni-(Mo, W)-Gao Cu-Al are that alloy is when using as perhardened steel, in order to ensure its machinability, be that target is modulated with the single phase structure of top bainite structure or bottom bainite structure.But the top bainite structure is the tissue of excellent in machinability but also is the low tissue of toughness on the contrary that in addition, the bottom bainite structure is the tissue of tenacity excellent on the contrary, but also is the tissue that machinability has some differences.
Therefore, the present inventor finds, change to the mixed structure of top bainite and bottom bainite by single phase structure with existing top bainite structure or bottom bainite structure, the step of going forward side by side is put in order its best combined balance system, and can access the machinability more excellent than top bainite structure, and obtain the toughness identical, realize simultaneously shortening the fabrication cycle of metal die and improving work-ing life with the bottom bainite structure.
In addition, the mixed structure of top given to this invention bainite and bottom bainite depends on that not only steel forms, and the very big influence of the speed of cooling when being subjected to quenching.But steel of the present invention is particularly fully adjusted by the amount optimizing that makes Cu, Cr two elements, so be used to form the heat treatment step of the mixed structure of the top bainite of target and bottom bainite, its management is not difficult.For example, be heated to austenite region after, even heat-treat the air cooling that should tail off, also can access top bainite and bottom bainite mixed structure.In addition, even the speed of cooling after the hot-work is the above direct quenching of air cooling, also can access top bainite and bottom bainite mixed structure.
Also have, the phase transformation resultant that produces when the bainite in the structure of steel is the cooling austenite usually a kind of generates the intermediate temperature range that temperature and martensite generates temperature at perlite and produces.And what produce near the pearlitic transformation temperature during microscopic examination is shown as featheriness (bulk), and what produce near martensite generates temperature is shown as needle-like, and the former is called as the top bainite, and the latter is called as the bottom bainite.Top given to this invention bainite and bottom bainite mixed structure, if expression then is a tissue (top bainite 30 area %, bottom bainite 70 area %) for example shown in Figure 1 particularly, or tissue shown in Figure 2 (top bainite 40 area %, bottom bainite 60 area %).And, for relatively, also shown the top bainite structure (Fig. 3) and the bottom bainite structure (Fig. 4) of existing steel.
The top bainite of steel so of the present invention and bottom bainite mixed structure, preferred feature is that in area % (below, only be designated as %) bottom bainite be 20～80%.In the bainite structure of the top of excellent in machinability, mix 20～80% bottom bainite as different tissues, suitably embrittlement when cutting thus, can access than the more excellent machinability of uniform top bainite structure.But it is insufficient that the bottom bainite is lower than 20% o'clock toughness, and surpassing 80% o'clock machinability has some poor, therefore is made as 20～80%.Also have, if the top bainite be main body then toughness have that some are poor, so more preferably the bottom bainite is more than 60%.On the other hand, more preferably the bottom bainite on be limited to 70%.
In addition, the preferred composition of steel of the present invention is characterised in that, measures suitableization by making Cu, Cr, and moderately makes the bainite structure miniaturization, tissue is adjusted into the mixed structure of preferred top bainite and bottom bainite.Promptly, in the perhardened steel that has the low C-Mn-Ni-of hardness and machinability (Mo, W)-Cu-Al system or low C-Mn-Ni-(Mo, W)-Gao Cu-Al system concurrently, even the management when the quenching heat treatment operation is relatively easy to the speed of cooling scope, also can make it have both extremely excellent machinability and toughness.
Below, the regulation reason of composition of the steel of the present invention regulation is described.
C is that the quenching structure that will hang down the perhardened steel of C-Mn-Ni-Mo (W)-Cu-Al system or low C-Mn-Ni-(Mo, W)-Gao Cu-Al system remains bainite structure, and be used to give the basic interpolation element of matrix, this matrix is brought the precipitation-hardening of separating out based on the Cu-Fe sosoloid in the tempering, Ni-Al intermetallic compound and Mo, W carbide.If cross and make base material martensitic stucture reduction machinability at most, in addition, form the over-drastic carbide machinability is reduced.Therefore, in the present invention, be defined as 0.05～0.17 quality % (below, only be designated as %).Be preferably more than 0.08%.Most preferably be more than 0.10% and/or below 0.14%.
Si is the corrosion proof element that improves the atmosphere when using as steel work.Cause ferritic generation at most if cross, machinability is descended, therefore be made as below 0.6%.If reduce then anisotropy reduction of Si, banded segregation reduces in addition, is preferably below 0.4% in order to obtain excellent mirror finish.Preferred lower limit is 0.1%.
Mn is for the high mixed structure of toughness of the present invention, is preferably one of most important element containing the perhardened steel of mixed structure that 20～80% bottom bainite structure is a base material.Mn is the flexible element that improves base material basically, needs more than 0.5%.In addition, Mn improves bainitic hardening, is easy to obtain the element as 20～80% bottom bainite structure of the feature of preferred tissue of the present invention.Therefore, be preferably more than 1.0%, more preferably add more than 1.25%.In addition, Mn has the ferritic generation of inhibition, gives the effect of Q-tempering (timeliness) hardness of appropriateness.But toughness became too high when Mn was too much, can not guarantee excellent machinability, therefore was limited to below 2.0%.Be preferably below 1.6%.
The interpolation of Ni is in order to improve bainitic hardening, to suppress ferritic generation in addition, in addition, when tempering (timeliness), the Ni-Al intermetallic compound is separated out, obtain desired hardness, and, ductility is suitably descended, obtain the raising of machinability.The bainitic transformation temperature is reduced, make bainite structure miniaturization exceedingly, in addition, also influence martensitic phase and change, make the viscosity rising of base material in addition and machinability is reduced, therefore be made as below 3.5%, then can not obtain above-mentioned additive effect if cross to hang down, therefore be made as more than 2.5%.Be preferably more than 2.6%, most preferably be more than 2.8% and/or below 3.2%.
Cr is for one of most important element of mixture ratio that obtains mixed structure of the present invention and then its preferred top bainite and bottom bainite, even the management that has when the quenching heat treatment operation is relatively easy to the speed of cooling scope, also make the suitably effect of miniaturization of bainite structure.In addition, also have the raising solidity to corrosion, the hardness when improving nitrogenize is when further suppressing attrition process or the effect of getting rusty during the goods keeping.But, make bainite structure miniaturization exceedingly in the time of too much, also influence martensitic phase and change, machinability is reduced, so need be made as below 2.0%.Be preferably below 1.0%, more preferably more than 0.3% and/or below 0.8%.It is particularly effective as the metal die steel that the plastics forming that requires machinability is used.
W, Mo are during the tempering (timeliness) at steel of the present invention is handled, particularly the high tempering (timeliness) above 500 ℃ is handled, has the fine carbide of separating out, cause separating out (timeliness) sclerosis, improve the element of the corrosion proof effect of the atmosphere when using in addition with respect to goods.Situation of the present invention need not heavy addition, too much can cause the reduction of machinability, therefore one or both of W and Mo is made as below 0.7% in (1/2W+Mo).Under the situation of the effect that goes for above-mentioned interpolation especially, preferably be made as more than 0.1% in (1/2W+Mo).Most preferably be more than 0.2% and/or below 0.4%.Also have, slow though W and Mo handle equally in above-mentioned effect because W and Mo compare velocity of diffusion, so during heavy addition W, during hot-work or during quenching not the residual possibility of solid solution carbide uprise.Thus, from this point, the present invention preferably only adopts Mo.
Al be in tempering (timeliness) is handled, bring the Ni-Al intermetallic compound fine separate out generation separate out (timeliness) sclerosis, make one of important element that the machinability of excellence of the present invention forms.In addition, Al is the interpolation element that is used to obtain wishing hardness, if carry out the effect that nitrogenize then has the nitrogenize hardness rising that makes this moment.The growing amount of alumina series inclusion increases when too much, and the minute surface finishability is reduced, and pitting corrosion resistance is descended, and causes the excessive reduction of ductility in addition, therefore, is made as below 1.5%, is made as more than 0.5% because machinability is descended so cross when hanging down.Particularly be preferably more than 0.8% in order further to improve the machinability when forming 20～80% bottom bainite structure.Most preferably be more than 0.95% and/or below 1.2%.
Cu and above-mentioned Cr are one of the most important element that is used to obtain the mixture ratio of mixed structure of the present invention, particularly preferred top bainite and bottom bainite equally, even the management that has when the quenching heat treatment operation is relatively easy to the speed of cooling scope, also make the suitably effect of miniaturization of bainite.In addition, be to be used for separating out (timeliness) sclerosis what tempering (timeliness) handled that bring Fe-Cu sosoloid fine separate out generation, the basic machinability of giving steel of the present invention is used to obtain wishing the element of hardness in addition, also bring excellent solidity to corrosion in addition.But, can make the hot workability reduction in the time of too much, make bainite miniaturization exceedingly in addition, also influence martensitic phase and change, machinability is descended, therefore be made as below 2.5%, cross when hanging down and can not obtain above-mentioned additive effect, therefore be made as more than 0.7%.Be preferably more than 1.2% and/or below 1.8%.
In addition, particularly in order to improve machinability, can add the S below 0.3% among the present invention.Be preferably more than 0.002%.The interpolation of S is extremely effective to improving machinability, but its interpolation can bring the mirror finish deterioration, so preferably its utilization is reduced to below 0.005% under the situation of specularity requiring.
In addition, from as at least a element of selecting V, the Nb of 4A, 5A family element, Ta, Ti, Zr, the Hf, make the crystal grain miniaturization, improving on the flexible point is the element with same function.Heavy addition can be brought up to solution hardness and timeliness hardness more than necessity, reduces machinability and toughness, so when managing as impurity, even add, also preferably be controlled at below 0.5% respectively.Also have, V has the effect of raising temper softening opposing, and when still forming the V carbide of hard on the contrary, it particularly can bring detrimentally affect to mirror finish, so preferably carry out independent and special the management in 4A, 5A family element.If pay attention to the minute surface processibility, then preferably V be controlled at below 0.1%.More preferably be lower than 0.03%, more preferably be lower than 0.02%.
From at least a element that Be and B select, be the element that has same function with element as the hardenability of the situation of improving massive article.Even these element heavy addition effects are also few, can make the processibility deterioration on the contrary, therefore, when manage as impurity, even add, be preferably also that Be:0.5% is following to be reached below the B:0.01%.In addition, at least a element of selecting from Pb, Bi, Se, Te and has identical effect as the element that improves machinability.But the heavy addition of these elements can make the toughness deterioration, therefore remain when managing as impurity, even add, also preferably count below 0.5% with total amount.
Steel of the present invention is supplied with the pre-hard state of the hardness of for example 34～45HRC, is processed into article shape with this state, if metal die then after copying, is implemented attrition process, further implements height minute surface precision work or wrinkle processing etc. and uses.When being lower than 34HRC, in use (as the shaping of metal die time) problem of the damage of wearing and tearing etc. can take place, in addition, when surpassing 45HRC, machinability is had detrimentally affect, so preferred hardness is 34～45HRC.
And the desired toughness of perhardened steel of the present invention is in order to prevent crackle and the necessary characteristic of bending.Therefore, be based on the impact value that the 2mmU type nick-break test sheet of the metallic substance pendulum impact test method of JIS-Z-2242 (2005) produces as toughness value, more particularly, estimate, be preferably 24J/cm with the condition of embodiment described later
2More than, 25J/cm more preferably
2More than.The toughness of excellence of the present invention consists of on the basic basis at the composition with steel, and the control bainite structure is realized therefrom, but is preferably the balance of considering with above-mentioned hardness value, and can realize mutually with the machinability of excellence.
The supply mode of perhardened steel, normally following this circulation path, from the former material producer modified former material in centre of regulation hardness that is that dispatches from the factory, processing producer should cut into necessary size and 6 faces are cut precision work by middle former material, also follow according to needs and carry out grinding precision work, give metal die producer as the final user with it.And, particularly nearest, have in order to improve the working (machining) efficiency of final user's side, intermediary processing producer will be adjusted into the tendency that the perhardened steel of high-precision finishing size is supplied with as " steel plate (plate) " in advance according to final user's requirement.For the perhardened steel of supplying with the shape of steel plate, require particularly in positive face milling cutters processibility, be in the cutting of positive face milling cutters, can with the wearing and tearing of cutting blades less feature such as cutting efficiently process, and require cutting surface can access level and smooth surface roughness.Therefore, control bainite structure and the perhardened steel of the present invention that obtains are because particularly positive face milling cutters excellent in workability so be applicable to this steel plate, can be brought into play maximum action effect.
Embodiment 1
After the test portion 1 that the surplus of the chemical ingredients shown in the table 1 is made of Fe and unavoidable impurities carries out hot rolling, be heated to 880 ℃ austenite region, carry out bainite and generate thermal treatment (bainitic hardening) with half cold 5 minutes, half cold 15 minutes, half cold 30 minutes, half cold 70 minutes cooling conditions respectively, carry out tempering 500～550 ℃ temperature ranges, hardness is modulated at 38～40HRC.For tissue, be modulated into the mixed structure, 40% top bainite of the bottom bainite of bottom bainite structure, 20% top bainite and 80% and mixed structure, the top bainite structure of 60% bottom bainite respectively according to above-mentioned cooling conditions.Also have, half cold (time) is meant the required time of temperature that is cooled to (quenching temperature+room temperature)/2 from quenching temperature.
Table 1
| Test portion No. | Chemical ingredients (mass%) | |||||||||
| C | Si | Mn | S | Ni | Cr | W | Mo | Cu | Al | |
| 1 | 0.12 | 0.30 | 1.36 | 0.004 | 3.06 | 0.20 | ＜0.01 | 0.27 | 1.00 | 1.00 |
* the element beyond above-mentioned is lower than 0.01%
Face cutter (face mill) processing of Φ 80mm has been implemented in the evaluation of machinability.That is, at the cutting blades that uses sintering metal (cermet) system, cutting speed is 116m/min, and feeding is the 0.09mm/ sword, cuts in the processing conditions into 1mm, and the tools for measurement abrasion loss is as estimating up to the cutting distance of the wearing and tearing of carrying out 0.2mm.
Flexible is estimated, and based on the metallic substance pendulum impact test method of JIS-Z-2242 (2005), uses 2mmU type nick-break test sheet to implement the pendulum test, measures the pendulum impact value under the room temperature.Test film is that the position of the rolling direction (L direction) of test portion is taked 3 in its length, and the mean value of the end value of each test film is estimated as impact value.The above table 2 that the results are shown in.
Table 2
| Speed of cooling | Tissue (top B: bottom B) | Length of cut (m) | Impact value (J/cm 2) | Remarks |
| Partly cold 5 minutes | 0∶100 | 0.8 | 30 | Comparative steel |
| Partly cold 15 minutes | 20∶80 | 1.7 | 26 | Steel of the present invention |
| Partly cold 30 minutes | 40∶60 | 3.0 | 22 | Steel of the present invention |
| Partly cold 70 minutes | 100∶0 | 1.1 | 15 | Comparative steel |
* Zu Zhi symbol B represents bainite.
As shown in table 2, the steel of the present invention that is modulated into the mixed structure of top bainite and bottom bainite is compared with the comparative steel of the single phase structure that is modulated into top bainite structure or bottom bainite structure, and machinability significantly improves.In addition, in the mixed structure of top bainite 40% and 60% bottom bainite, machinability further significantly improves.In addition, for toughness, comparing with 100% bottom bainite structure has deficiency slightly, but compares obvious excellence with 100% top bainite structure.
Embodiment 2
After the test portion 2～6 that the surplus of the chemical ingredients shown in the table 3 is made of Fe and unavoidable impurities carries out hot rolling, after being heated to 880 ℃ austenite region, carry out air cooling, carry out tempering 500～590 ℃ temperature ranges, use such supplying to try material, carry out machinability and flexible evaluation.Wherein, the air cooling of test portion 2～5 is equivalent to partly cold 30 minutes, and the air cooling of test portion 6 is equivalent to half cold 10 minutes cooling conditions.
Table 3
| Test portion No. | Chemical ingredients (mass%) | |||||||||
| C | Si | Mn | S | Ni | Cr | W | Mo | Cu | Al | |
| 2 | 0.12 | 0.30 | 1.36 | 0.004 | 3.06 | 0.20 | ＜0.01 | 0.27 | 1.00 | 1.00 |
| 3 | 0.12 | 0.30 | 1.44 | 0.003 | 3.09 | 0.20 | ＜0.01 | 0.30 | 1.52 | 1.04 |
| 4 | 0.12 | 0.30 | 1.40 | 0.003 | 2.99 | 0.50 | ＜0.01 | 0.30 | 1.53 | 1.05 |
| 5 | 0.12 | 0.30 | 1.36 | 0.003 | 2.95 | 0.99 | ＜0.01 | 0.30 | 1.50 | 1.08 |
| 6 | 0.14 | 0.29 | 1.38 | 0.004 | 2.96 | 1.89 | ＜0.01 | 0.30 | 2.25 | 1.08 |
* the element beyond above-mentioned is lower than 0.01%
The evaluation of machinability has been implemented to hole and has been processed, the positive face milling cutters processing of Φ 125mm.The evaluation of boring processing is the drill bit with the Φ 2mm of high speed steel, and at cutting speed 15m/min, speed of feed 120mm/min under the processing conditions of working depth 20mm, has measured 50 the tool wear amounts behind the hole of processing.The evaluation of positive face milling cutters processing is to use the cutting blades of sintering metal system, in cutting speed is 150m/min, and speed of feed is the 0.13mm/ sword, and incision is 2 (degree of depth) * 100 (width) mm, the cutting blade number is under one piece the processing conditions, to have measured the tool wear amount when cutting 49.7 minutes.The flexible evaluation is carried out similarly to Example 1.More than the results are shown in table 4.
Table 4
| Test portion No. | Half cool time (min) | Tissue (top B: bottom B: M) | Abrasion loss (mm) | Impact value (J/cm 2) | Hardness (HRC) | Remarks | |
| Drill bit | Milling cutter | ||||||
| 2 | 30 | 40∶60∶0 | 0.11 | 0.35 | 22 | 39.5 | Steel of the present invention |
| 3 | 40∶60∶0 | 0.09 | 0.31 | 49 | 39.9 | Steel of the present invention | |
| 4 | 30∶70∶0 | 0.08 | 0.31 | 53 | 39.1 | Steel of the present invention | |
| 5 | 20∶80∶0 | 0.09 | 0.48 | 66 | 37.9 | Steel of the present invention | |
| 6 | 10 | 0∶80∶20 | 0.14 | 0.60 | 60 | 38.3 | Comparative steel |
* Zu Zhi symbol B represents bainite, and M represents martensite.
As known from Table 4, in any composition of test portion 2～5, by the mixed structure's (the bottom bainite is 20%～80%) that is modulated into top of the present invention bainite and bottom bainite, (test portion 2 is because Cu is 1% and few slightly and can have both excellent machinability and toughness, so toughness step-down, but compare with embodiment 1,100% top bainite structure, obviously excellent).In addition, formed some martensitic stuctures in test portion 6 tissues, though tenacity excellent, machinability has some poor.
Embodiment 3
After the test portion 7～9 that the surplus of the chemical ingredients shown in the table 5 is made of Fe and unavoidable impurities carries out hot rolling, be heated to 880 ℃ austenite region, cool off to be equivalent to half cold 40 minutes air cooling, carry out tempering, hardness is modulated into 36～38HRC 530～590 ℃ temperature ranges.According to above-mentioned cooling conditions, tissue is modulated into the mixed structure of the bottom bainite of 30% top bainite and 70%.
Table 5
| Test portion No. | Chemical ingredients (mass%) | |||||||||
| C | Si | Mn | S | Ni | Cr | W | Mo | Cu | Al | |
| 7 | 0.12 | 0.30 | 1.42 | - | 3.01 | 0.12 | ＜0.01 | 0.31 | 2.26 | 1.04 |
| 8 | 0.12 | 0.30 | 1.41 | 0.003 | 2.99 | 0.14 | ＜0.01 | 0.29 | 2.23 | 1.08 |
| 9 | 0.12 | 0.31 | 1.39 | 0.006 | 3.01 | 0.16 | ＜0.01 | 0.30 | 2.23 | 1.06 |
* one is to be lower than 0.001%
* the element beyond above-mentioned is lower than 0.01%
The positive face milling cutters processing of Φ 160mm has been implemented in the evaluation of machinability.That is, using the cutting blades of sintering metal system, is 115m/min in cutting speed, and speed of feed is the 0.12mm/ sword, and incision is 2 (thickness) * 90 (width) mm, and the cutting blade number is under one piece the processing conditions, to have measured the tool wear amount when cutting 60 minutes.More than the results are shown in table 6.
Table 6
| Test portion No. | S measures (mass%) | Tissue | Abrasion loss (mm) | Remarks |
| 7 | ＜0.001 | Top bainite 30% bottom bainite 70% | 0.2 | Steel of the present invention |
| 8 | 0.003 | 0.1 | Steel of the present invention | |
| 9 | 0.006 | 0.1 | Steel of the present invention |
As known from Table 6, do not add the test portion 7 of S and the test portion 8,9 of trace interpolation and compare, even the S trace is also effective to improving machinability.S because the formation of the MnS in the tissue etc. has detrimentally affect to specularity, so when paying attention to specularity, preferred trace adds.
(industrial utilizability)
The perhardened steel of the present invention of machinability and tenacity excellent is suitable for the metal die steel that uses in the plastics forming for example most, and in addition, also going for injection machine screw rod etc. needs hardness also to pay attention to machine components of machinability etc.
Claims (10)
1. the perhardened steel of machinability and tenacity excellent is characterized in that,
It is a kind of tool steel, in quality %, contain: C:0.05～0.17%, Si:0.6% are following, Mn:0.5～2.0%, Ni:2.5～3.5%, Cr:2.0% are following, W and Mo one or both (1/2W+Mo): below 0.7%, Al:0.5～1.5%, Cu:0.7～2.5%, tissue is the mixed structure of top bainite and bottom bainite.
2. the perhardened steel of machinability and tenacity excellent is characterized in that,
In quality %, has following composition, contain: C:0.05～0.17%, Si:0.6% are following, Mn:0.5～2.0%, Ni:2.5～3.5%, Cr:0.3～0.8%, W and Mo one or both (1/2W+Mo): below 0.7%, Al:0.5～1.5%, Cu:1.2～1.8%, surplus is made of Fe and unavoidable impurities, and tissue is the mixed structure of top bainite and bottom bainite.
3. the perhardened steel of machinability according to claim 1 and 2 and tenacity excellent is characterized in that,
In quality %, with the part of the following replacement of fe of S:0.3%.
4. the perhardened steel of machinability according to claim 1 and 2 and tenacity excellent is characterized in that,
The mixed structure of top bainite and bottom bainite is 20～80% in area % bottom bainite.
5. the perhardened steel of machinability according to claim 3 and tenacity excellent is characterized in that,
The mixed structure of top bainite and bottom bainite is 20～80% in area % bottom bainite.
6. the perhardened steel of machinability according to claim 1 and 2 and tenacity excellent is characterized in that,
Hardness is 34～45HRC.
7. the perhardened steel of machinability according to claim 3 and tenacity excellent is characterized in that,
Hardness is 34～45HRC.
8. the manufacture method of the perhardened steel of machinability and tenacity excellent is characterized in that,
After following tool steel is heated to austenite region, carry out generating thermal treatment to the mixing region of top bainite and bottom bainite refrigerative upper/lower mixed with bainite, this tool steel contains in quality %: C:0.05～0.17%, Si:0.6% are following, Mn:0.5～2.0%, Ni:2.5～3.5%, Cr:2.0% are following, W and Mo one or both (1/2W+Mo): below 0.7%, Al:0.5～1.5%, Cu:0.7～2.5%.
9. the manufacture method of the perhardened steel of machinability according to claim 8 and tenacity excellent is characterized in that,
In quality %, with the part of the following replacement of fe of S:0.3%.
10. according to Claim 8 or the manufacture method of the perhardened steel of 9 described machinabilities and tenacity excellent, it is characterized in that,
After having carried out upper/lower mixed with bainite generation thermal treatment, be tempered to the hardness of 34～45HRC.
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Also Published As
| Publication number | Publication date |
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| KR20070090750A (en) | 2007-09-06 |
| CN100575525C (en) | 2009-12-30 |
| KR100908624B1 (en) | 2009-07-21 |
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