The wear-resisting hot stamping die alloy steel material of heat resistance
Technical field
The present invention relates to the wear-resisting hot stamping die of a kind of heat resistance with alloy steel material and preparation method thereof, belong to hot stamping die material manufacturing process technology field.
Background technology
Energy-saving and environmental protection, safety are the general trends of current automotive engineering development, and reduction oil consumption, save energy, minimizing motor vehicle emission are one of current urgent problems that solves, and wherein the automobile lightweight is the important channel that addresses this problem.At present, Iron And Steel Company has released a series of quenching boron steel series with superstrength, as 22MnB5, the 30MnB5 of well-known Arcelor company release, and is the Usibor1500 of auto parts with production specially.The characteristics of these quenching boron steels are after roll forming, and material structure is uniform ferrite+perlite, and yield strength is 280-400Mpa, and tensile strength is greater than 450Mpa; And after Overheating Treatment, it is organized as uniform martensite, and yield strength can reach 1200Mpa, and tensile strength can reach 1600Mpa.Adopt the auto parts of this kind steel plate production can make the part loss of weight of equality strength, rigidity more than 50%.But since during the intensity of ultrahigh-strength steel the 2-3 of general steel plate intensity doubly, required plastic force is very big, tends to during shaping therefore cause that mould damages, the equipment vibrations, and easily produce break, wrinkling, problem such as size and dimension is bad.Therefore, original cold punching forming process can not satisfy the needs of technology and production development again, needs a kind of new heating shaping technology mode.Hot press-formed technology mainly is to utilize metal under the condition of high temperature, and its plasticity and ductility increase sharply, and yield strength is the characteristics of decline rapidly, makes the technology of component shaping by mould.Adopt hot worked method, generally be that plate is heated to more than the recrystallization temperature certain suitable temperature (for ferrous materials, be heated to austenitic state) time carry out drawing, stress of fluidity when making sheet forming reduces, improves the plasticity of plate, the resilience of reduction drip molding, and reduces the tonnage of required equipment.Compare with the plate cold stamping, plate hot press-formed has that resistance to deformation is little, plasticity good, the forming limit advantages of higher.For boron steel, not only has hot formed advantage described above by thermoforming, and be equipped with suitable follow-up heat treatment mode, can also make plate bring into play its best performance, for automobile provides high-quality component, thereby not only reduced the weight of automobile component, also improved its shock resistance and fatigue property, improved the security of automobile.Still there is not special suitable hot press-formed moulding stock at present both at home and abroad.What Germany enterprise adopted is CR7V and 1.2379, and that Japanese enterprises adopts is SKD61.From the present condition of production, these materials are all chosen from existing moulding stock, and relative merits are respectively arranged, but are not the materials of best suitable hot press-formed usefulness.
Summary of the invention
The purpose of this invention is to provide the wear-resisting hot stamping die of a kind of heat resistance alloy steel material and preparation method thereof.
The wear-resisting hot stamping die alloy steel material of a kind of heat resistance of the present invention is characterized in that having following chemical constitution and mass percent thereof:
C 0.4-0.5%, Si 0.3-0.5%,
Mn 0.65-0.85%, Cr 2.5-2.7%,
Mo 2.1-2.4%, V 0.8-1.0%,
P <0.025%, S <0.005%,
The Fe surplus
The wear-resisting hot stamping die of the heat resistance of the present invention preparation method of alloy steel material is characterized in that having following process and step:
A. induction melting: batching is placed medium-frequency induction furnace, under 1500~1700 ℃ of temperature, carry out melting, pour into a mould steel ingot then;
B. esr: steel ingot is put in the esr device, carries out secondary refining, with obtain composition evenly, the steel ingot of dense structure;
C. annealing: at 850~860 ℃ of following insulation 7h, air cooling ℃ is carried out in slow cooling to 300 then;
D. high-temperature homogenization: above-mentioned steel ingot is heated to 1220~1250 ℃, and is incubated 8~10 hours, make the composition of steel homogenizing, prevent component segregation, improve the solidified structure of material, cool off with being placed in the air;
E. forge: with above-mentioned treated steel ingot reheat to 1200~1230 ℃, carry out rough forge subsequently, final forging temperature is 980 ℃, obtains the steel forgings blank;
F. annealing: above-mentioned steel forgings blank is put into process furnace, is heated to 830 ℃, the insulation 8h, after stove is chilled to 300 ℃ then again air cooling to room temperature; Finally obtain the wear-resisting hot stamping die alloy steel material of heat resistance.
The present invention designs the theoretical foundation of steel grade material composition:
(1) matrix hardness of the content of C decision hardened steel.For tool steel, the carbon part in the steel enters in the matrix of steel and causes solution strengthening.A part of in addition carbon will be combined into alloy carbide with the carbide forming element in the alloying element.To the hot stamping die steel, this alloy carbide is except that small amount of residual, also require it in drawing process on the quenched martensite matrix disperse separate out and produce the secondary hardening phenomenon, thereby decide the performance of hot stamping die steel by the tissue of equally distributed residual alloy carbide and tempered martensite.Therefore, the C content in the hot stamping die material is advisable 0.45 ~ 0.48%.
(2) Si is one ferrite is replaced the very effective element of solution strengthening, but reduces the toughness and the plasticity of steel simultaneously to a certain extent.Si is the effective element that improves resistance to tempering, and still, the Si add-on is too much, and carbide accumulative overaging speed is increased, to such an extent as to be difficult to control.Si content is controlled at 0.3 ~ 0.5%.
(3) Mn has the solution strengthening effect, thereby improves ferrite and austenitic intensity and hardness.Manganese is weak carbide forming element, and it is solvable goes in the cementite to form alloyed cementite, and its formation can reduce the free energy of system.Can increase the hardening capacity of steel in the molten figure austenite of manganese strongly, the strong simultaneously Ms point that reduces steel.But the manganese too high levels can make fragility increase, and takes all factors into consideration it is controlled at 0.65 ~ 0.85%.
(4) Cr is that the most generally contain and alloying element cheapness in the alloy tool steel.Chromium all has favorable influence to wearability, hot strength, hot hardness, toughness and the hardening capacity of steel, and it dissolves in the corrosion resisting property that matrix can significantly improve steel simultaneously.Present H13 modified version hot-work die steel generally has Cr5.0% and Cr2.6% type.Be chosen to be Cr2.5 ~ 2.7% in the hot stamping die material.
(5) Mo dissolves in the effect that also has solution strengthening among the Fe, and Mo is dissolved in the hardening capacity that can improve steel in the austenite.Mo adds as the main alloy element that makes steel have secondary hardening, and Mo can improve the decarburization oxidation sensitive of steel, so Mo content is controlled at 2.1 ~ 2.4% proper.
(6) V is displacement solution strengthening ferrite and the element that forms the austenite circle.The main effect of V in tool steel is the crystal grain and the tissue of refinement steel, increases the temper resistance of steel and strengthens the secondary hardening effect.In general, but V adds 0.05% crystal grain thinning, increases with add-on, and thinning effect is strengthened.Even because 700 ℃ of temperature convergences, the carbide stability of V is still high, still can keep tiny,, also be the important alloy element of the steel of at high temperature being on active service so V is the element that effectively stops AUSTENITE GRAIN COARSENING.Therefore, be controlled at 0.8 ~ 1.0%.
(7) S and P are harmful element, and its content all should be controlled at bottom line, in order to avoid produce the performance that worsens the hot stamping die material, produce adverse consequences, should make P<0.025%, S<0.005%.
Description of drawings
Fig. 1 is the thermostability comparison diagram of steel of the present invention and other steel grades.
Embodiment
After now specific embodiments of the invention being described in.
Embodiment
A kind of new hot stamping die material of present embodiment, its chemical ingredients comprises by weight percentage:
C 0.47%, Si 0.37%,
Mn 0.65%, Cr 2.6%,
Mo 2.2%, V 0.94%,
P <0.013%, S <0.005%,
The Fe surplus.
Preparation process is as follows:
A. induction melting: batching is placed medium-frequency induction furnace, under 1500~1700 ℃ of temperature, carry out melting, pour into a mould steel ingot then;
B. esr: steel ingot is put in the esr device, carries out secondary refining, can reduce the content of inclusion, and obtain composition evenly, dense structure, the measured steel ingot of matter.Alloy is removed inclusion by wash heat and the come-up in the molten bath during remelting, obtains further refining, and the enduring quality and the plasticity of alloy all are improved, and eliminates or has alleviated various macroscopic views and microscopic defect;
C. annealing: at 850~860 ℃ of following insulation 7h, air cooling ℃ is carried out in slow cooling to 300 then.
D. high-temperature homogenization: above-mentioned steel ingot is heated to 1220~1250 ℃, and is incubated 8~10 hours, make the composition of steel homogenizing, prevent component segregation, improve the solidified structure of material, place air to cool off then;
E. forge: above-mentioned steel ingot is heated to 1200~1230 ℃, carries out rough forge subsequently, final forging temperature is 980 ℃, obtains the steel forgings blank;
F. annealing: the steel forgings blank is put into process furnace, is heated to 830 ℃, the insulation 8h, after stove is chilled to about 300 ℃ then again air cooling to room temperature.Finally obtain the wear-resisting hot stamping die of heat resistance with adding up to steel.
Performance test
Above-mentioned hot stamping die steel sample is done performance test, and the result is as follows:
(1) annealed state hardness 205HB is 50HRC through hardness after 1020 ℃ of+600 ℃ of temper of quenching;
(2) through after 1020 ℃ of+600 ℃ of temper of quenching, the ballistic work of 7*10*55mm impact specimen is 172J;
(3) through after 1020 ℃ of+600 ℃ of temper of quenching, tensile strength is 1900MPa;
(4) through after 1020 ℃ of+600 ℃ of temper of quenching, the linear expansivity in the time of 200 ℃ is 12.3*10
-6/ K, thermal conductivity are 31.6 W/ (m*K).
Hot stamping die steel of the present invention and QRO90 steel and CR7V steel are done heat stability test under 600 ℃ of conditions; QRO90 steel and CR7V composition of steel are as shown in table 1 below.The thermostability contrast of steel of the present invention, QRO90, CR7V steel as shown in Figure 1.
The composition of table 1 QRO90 and CR7V
Composition (wt%) |
C |
Si |
Mn |
Cr |
Mo |
V |
P |
S |
QRO90 |
0.389 |
0.25 |
0.53 |
2.62 |
2.21 |
0.934 |
0.013 |
0.005 |
CR7V |
0.448 |
0.483 |
0.357 |
6.45 |
1.29 |
0.77 |
0.016 |
0.0004 |
Be used for correlated steel grade thermal treatment process:
QRO90:1200 ℃ of+600 ℃ of tempering 2 hours (2 times) of quenching.
CR7V:1020 ℃ of+550 ℃ of tempering 2 hours (2 times) of quenching.
Experimental result
Can find out that by accompanying drawing 1 trial curve under 600 ℃ of conditions, the hardness of steel of the present invention is apparently higher than QRO90 and CR7V.Steel of the present invention (code name of steel of the present invention is SDCM1) is applied to hot stamping die, can significantly improves the work-ing life of mould.