CN105274444B - Cold work tool steel - Google Patents

Cold work tool steel Download PDF

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Publication number
CN105274444B
CN105274444B CN201510252702.3A CN201510252702A CN105274444B CN 105274444 B CN105274444 B CN 105274444B CN 201510252702 A CN201510252702 A CN 201510252702A CN 105274444 B CN105274444 B CN 105274444B
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steel
work tool
content
cold work
mold
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CN105274444A (en
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伊吹基宏
清水崇行
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Daido Steel Co Ltd
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Daido Steel Co Ltd
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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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/84—Controlled slow cooling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C21D1/25—Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • 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
    • C21D2211/001—Austenite
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/02—Hardening by precipitation

Abstract

The present invention relates to cold work tool steel, and it includes in terms of quality %: C:0.70% to 0.90%；Si:0.60% to 0.80%；Mn:0.30% to 0.50%；P:0.30% or less；S:0.030% or less；Cu:0.01% to 0.25%；Ni:0.01% to 0.25%；Cr:6.0% to 7.0%；Mo+1/2W:2.50% to 3.00%；V:0.70% to 0.85%；N:0.020% or less；O:0.0100% or less；With Al:0.100% hereinafter, surplus is Fe and inevitable impurity, wherein meeting 1.66 (Mo+1/2W)+V < 5.7%.

Description

Cold work tool steel
Technical field
The present invention relates to cold work tool steel, and particularly, are related to shaping the preferred cold work tool of high tensile steel plate Use steel.
Background technique
In general, the cold work tool steel indicated by SKD11, is quenched at a temperature of being greater than or equal to 1,000 DEG C Handle (quenching treatment), then greater than or equal to 450 DEG C at a temperature of carry out tempering (tempering Treatment after), it is generally used for the degree of about HRC60 to HRC63.As the main application of the cold work tool steel, show Example is cold pressing mold and mould for cold forging.For example, patent document 1 discloses the size by improving carbide and is distributed come real The cold work tool steel of existing high rigidity and high tenacity.
On the other hand, in recent years, in automobile industry, the countermeasure of global warming issue has been required, and as most effective Solution, many companies are all absorbed in the lightweight of car body.It is known when improve car body lightweight when, can reduce from vehicle The amount of carbon dioxide of discharge.For this reason, though by when be used for than it is conventional it is thinner in the case where when remain to provide It is used as car body or structure member with the material for the conventional steel sheet same intensity for being typically used as car body materials.This material is known as High tensile steel plate.
High tensile steel plate is also known as " high tensile steel disc (High Tensile Strength Steel Sheets) ", And indicate the steel plate with high tensile.Conventional steel plate has the tensile strength more than or equal to 270MPa, however has The steel plate of the tensile strength of 340MPa to 790MPa is normally defined high tensile steel plate.It is greater than or equal to 1 in addition, having, The steel plate of the tensile strength of 000MPa is particularly referred to as Ultra-Drawing steel plate.
Patent document 1:JP-A-H02-277745
Summary of the invention
From the light-weighted requirement of car body, cold work tool has gradually been applied to superelevation with steel (cold working mold) and has drawn Stretch the processing of steel plate.For this reason, when by using cold working die forming Ultra-Drawing steel plate, cold working has been increased The load of mold.If cold working mold can not resist load, therefore cold working die deformation deteriorates car body or structural portion The dimensional accuracy of part.In order to obtain sufficient load resistance (load resistance), it is necessary to ensure that the hardness of mold is cold worked And impact value.It, effectively will be larger amount of in quenching treatment in order to obtain high rigidity while in view of resource-effective Carbon dissolution forms solid solution (solid solution) in material steel and then carries out post-curing by tempering.
As the method for increasing meltage of the carbon in solid solution, example is to increase the method for hardening heat.However, when increasing When adding hardening heat, it is understood that there may be roughening steel in crystal grain the problem of.The crystal grain of roughening causes the impact value of punching block to reduce.Cause This, it is necessary to it include the carbide such as VC of grain coarsening to be prevented under hardening heat, but work as and the carbon for preventing grain coarsening is excessively increased When the amount of compound, impact value is also reduced.In addition, expecting the hardness for being attributed to post-curing when adding the element of such as Mo and V It improves.
On the other hand, when focusing on the manufacturing process of cold working mold, cold working mold is generally cut simultaneously at room temperature Finishing is final shape.The Cutting Process is the shear-deformable fracture for being attributed to mold materials (cold work tool steel) (rupture) and the repetition of the chip (ruptured swarf) of fracture and the abrasion of tool, and temporarily and instantaneously increase mould Has the temperature in the cutting face of material.If mold is difficult to deform under the high-temperature, that is, if the hardness under high-temperature increases Add, machinability reduces.That is, increasing the load (increasing tool abrasion loss) of the tool of cutting dies, therefore increase cutting element The manufacturing time of cost and mold, and reduce the productivity of mold.
In view of above situation completes the present invention, the present invention is by providing in the necessary hardness for ensuring mold and necessary impact The productive cold work tool that mold can be improved while value is solved the above problems with steel.
As further investigation as a result, present inventors found that can solve the above problems.The specific method solved the problems, such as is such as Under.
The first aspect of the present invention is cold work tool steel, and it includes in terms of quality %:
C:0.70% to 0.90%；
Si:0.60% to 0.80%；
Mn:0.30% to 0.50%；
P:0.30% or less；
S:0.030% or less；
Cu:0.01% to 0.25%；
Ni:0.01% to 0.25%；
Cr:6.0% to 7.0%；
Mo+1/2W:2.50% to 3.00%；
V:0.70% to 0.85%；
N:0.020% or less；
O:0.0100% or less；With
Al:0.100% hereinafter,
Surplus be Fe and inevitable impurity,
Wherein meet 1.66 (Mo+1/2W)+V < 5.7%.
The second aspect of the present invention is the cold work tool steel according to first aspect, is further included in terms of quality % At least one below:
Nb:0.001% to 0.30%,
Ta:0.001% to 0.30%,
Ti:0.20% hereinafter, and
Zr:0.001% to 0.30%.
The third aspect of the present invention is the cold work tool steel according to first aspect or second aspect, after quenching The retained austenite scale of construction is less than or equal to 25 volume %.
The fourth aspect of the present invention is the cold work tool according to either one or two of first aspect, second aspect and the third aspect With steel, greater than or equal to 450 DEG C at a temperature of tempering after maximum hardness be more than or equal to 64HRC.
The present invention ensures hardness and impact necessary to mold within a predetermined range by adjusting C, Si, Cr, Mo, W and V Value.In addition, in order to improve the productivity of mold, optimizing the balance between Mo, W and V, and limit 1.66 (Mo+1/ in the present invention 2W) the relational expression of+V < 5.7%.In general, cutting dies at room temperature, and during cutting by cutting heat temporarily and instantaneously Increase the temperature of mold.In this case, when focusing on the hardness of mold, hardness highest and with temperature liter at room temperature It is high and reduce.Further investigation as the present inventors as a result, discovery temporarily and is instantaneously increasing mold by cutting In the case where temperature, particularly, if add each element of Mo, W and the V more a greater amount of than predetermined additive amount, machinability is damaged Thus deterioration stock-removing efficiency.That is, the element additive amount that they sum up Mo, W and V is to reduce one of productive factor of mold.
Incidentally, cold work tool disclosed in above-mentioned patent document 1 passes through the size and distribution of improvement carbide with steel It realizes high rigidity and high tenacity, but does not have characteristic of the invention, therefore the present invention has entirely different technological concept.
As described above, cold work tool steel according to the present invention, it can ensure the necessary hardness of mold and impact value The productivity of mold is improved simultaneously.
Detailed description of the invention
Fig. 1 is the figure for showing the relationship between tool abrasion loss (machinability) and the additive amount of Mo, W and V.
Fig. 2 is the figure for showing relationship of the steel of the present invention compared between the impact value of steel and the numerical value of hardness.
Specific embodiment
It will be described in cold work tool steel (hereinafter referred to as implementation of one of embodiment according to the present invention The cold work tool steel of scheme).The cold work tool of the embodiment can be applied to form high tensile steel plate mould with steel Tool, cold forging formed punch and punch die, mould for cold forging, squeeze forging (swaging) mold, rolling screw-threads (thread at bending die Rolling mold, formed punch component, slitter knife (slitter knife), punching press lead frame mold, meter, drawing) are used Deep-draw head (deep drawing punch), crooked formed punch, shear-blade, stainless steel bending die, drawing die (drawing Die), for example hot head of plastic processing tool, gear formed punch, cam part, pressurization punching press mold, progressive punching press mold, Sediment transport device sealing plate, screw member, concrete sprayer swivel plate, IC sealing mold and the high ruler of needs The accurate pressurizing mold of very little precision.In addition, the cold work tool of the embodiment with steel can also be used to carry out as CVD processing, The various cold metal dices (dice) used after PVD processing and the surface treatment of TD processing etc..Wherein, particularly preferred for tool There is the Ultra-Drawing steel plate of the tensile strength more than or equal to 1,000MPa.
The cold work tool of the embodiment contains following element with ladle.The type of addition element explained below, its addition Range and the reason of limit its range.
C:0.70% to 0.90%
C is to ensure that the essential elements of intensity and abrasion performance, and by with carbide former such as Cr, Mo, W, V and Nb Bonding is to form carbide.In addition, C for by quenching when be dissolved to parent phase (matrix phase) with formed solid solution from And martensitic structure is formed to ensure that hardness is necessary.In order in cold work tool with obtaining this effect in steel, C content Lower limit set is 0.70%.In contrast, when C content is excessive, carbide former be bonded with C with formed thick carbide because And impact value can be reduced.In addition, hot-workability when being hot-forged after the casting to ingot can be reduced.For those reasons, C contains The upper limit of amount is set as 0.90%.From above-mentioned viewpoint, the more preferable range of C content is 0.75% to 0.85%.
Si:0.60% to 0.80%
Si is dissolved to parent phase to form solid solution, and Si can accelerate the precipitation of other carbide, and can help to post-curing. In order to obtain these effects, the lower limit set of Si content is 0.60%.In contrast, as excessively addition Si, quenching can be reduced Property.For this reason, the upper limit of Si content is set as 0.80%.
Mn:0.30% to 0.50%
Addition Mn is to improve hardenability and stable austenite.Particularly, when hardenability reduces, the variation of hardness is microcosmic Level increases.In addition, Mn forms MnS, and can prevent the distortion by being attributed to heat treatment when inevitably including S (distortion) impact value caused by (anisotropic growth encourage) reduces.For those reasons, the lower limit set of Mn content is 0.30%.In contrast, when Mn content is excessive, hot-workability when being hot-forged after the casting to ingot can be reduced.For The upper limit of this reason, Mn content is set as 0.50%.
P:0.30% or less
P is inevitably included in steel.P is easy to be segregated in crystal grain boundary and toughness can be caused to reduce.For this The upper limit of reason, P content is set as 0.3%.
S:0.030% or less
S is inevitably included in steel.In general, energetically adding S to improve machinability.In the present invention, pass through To prevent the reduction of the impact value as caused by the distortion (anisotropic growth encourage) for being attributed to heat treatment, therefore addition S can form MnS S content is limited to less than or is equal to 0.03%.
Cu:0.01 to 0.25%
Cu is the element of stable austenite.However, can increase the retained austenite scale of construction when Cu content is excessive therefore can occur The ongoing change of size.In addition, hot-workability when being hot-forged after the casting to ingot can be reduced as excessively addition Cu. For those reasons, Cu content is set as 0.01% to 0.25%.
Ni:0.01% to 0.25%
Ni is the element of stable austenite.However, can increase the retained austenite scale of construction when Ni content is excessive therefore can occur The ongoing change of size.For this reason, Ni content is set as 0.01% to 0.25%.
Cr:6.0% to 7.0%
Cr is the element for improving corrosion resistance.In order to obtain this effect, the lower limit set of Cr content is 6.0%.Work as Cr When content is excessive, C can be reduced and be dissolved to austenitic structure to form the amount of solid solution, therefore sufficient hardness can not be obtained.Out It is set as 7.0% in the upper limit of this reason, Cr content.
Mo+1/2W:2.50% to 3.00%
Mo and W-shaped at fine carbides, and to facilitate the important element of post-curing.In order to obtain effect identical with Mo Fruit, it is necessary to add the W of double amount, therefore in the present invention, limit Mo content and 1/2 W content total amount.It is secondary in order to obtain The effect of hardening, the lower limit set of the content of Mo+1/2W are 2.50%.In contrast, when the content of Mo and W is excessive, can increase The remaining quantity of carbide when adding quenching, therefore the upper limit of the content of Mo+1/2W is set as 3.00%.
V:0.70% to 0.85%
V can be bonded to form carbide with C.Carbide can help to inhibit the roughening of crystal grain diameter.It is this in order to obtain Effect, the lower limit set of V content are 0.70%.When V content is excessive, the carbonitride of V can be easy to crystallization to reduce impact value. For this reason, the upper limit of V content is set as 0.85%.
N:0.020% or less
N is clearance type element (interstitial type element) and can help to the hardness of martensitic structure Increase.Relative to the carbon for being all clearance type element, N has stronger γ stability.However, when N content is excessive, during solidification Nitrogen in Steel material can be concentrated so that being more than the limitation that nitrogen sprays, therefore be easy to that hole (void) occurs in ingot.For this The upper limit of a reason, N content is set as 0.020%.
O:0.0100% or less
O be inevitably include element in molten steel.However, O can be bonded with Si and Al when O content is excessive Become the thick oxide of content to form it, therefore toughness can be reduced.From the viewpoint for preventing the phenomenon, the upper limit of O content is set It is set to 0.0100%.
Al:0.100% or less
Al is the element for being added to deoxidier.However, Al can be bonded to form thick oxide with O when Al content is excessive And its starting point that can become crackle (crack).For this reason, the upper limit of Al content is set as 0.100%.
1.66 (Mo+1/2W)+V: less than 5.7%
In order to increase post-curing, it is necessary to add Mo+1/2W and V.In contrast, when its total content is excessive, even if logical Cutting resistance or cutting heat when cutting are crossed to increase the temperature of mold, the hardness of mold may not be reduced, therefore can deteriorate Machinability.For this reason, its total content is limited to meet 1.66+V < 5.7 (Mo+1/2W).
Other than above-mentioned essential elements, the cold work tool steel of the embodiment is optionally including selected from following members Plain is one or more.That is, the cold work tool of the embodiment can be only by usually being formed with the member that quality % is counted with steel below: 0.70≤C≤0.90；0.60≤Si≤0.80；0.30≤Mn≤0.50；P≤0.30；S≤0.030；0.01≤Cu≤0.25； 0.01≤Ni≤0.25；6.0≤Cr≤7.0；2.50≤Mo+1/2W≤3.00；0.70≤V≤0.85；N≤0.020；O≤ 0.0100；With Al≤0.100, surplus is Fe and inevitable impurity, wherein meet 1.66 (Mo+1/2W)+V < 5.7%, but It is optionally including selected from the one or more of its content element as described below.
Nb:0.001% to 0.30%, Ta:0.00l% to 0.30%, Ti:0.20% is hereinafter, extremely with Zr:0.001% 0.30%
Nb, Ta, Ti and Zr are to be bonded with C and N to form the element of carbonitride, and can help to inhibit the thick of crystal grain Change.In contrast, as excessively addition Nb, Ta, Ti and Zr, machinability when finishing (finishing) can be reduced, therefore can Reduce the productivity of mold.For those reasons, the content of each element is set within the above range.
In addition, in the cold work tool steel of the embodiment, the retained austenite scale of construction after preferably quenching be less than or Equal to 25 volume %.This is because can increase after being attributed to tempering when the retained austenite scale of construction after quenching increases wait divide The die size of the retained austenite scale of construction of solution changes, it is thus possible to need the time to carry out precision cutting to mold.Furthermore it is preferred that Hardening heat is 1,000 DEG C to 1,100 DEG C.
In addition, in the cold work tool steel of the embodiment, it is preferred that more than or equal to 450 DEG C at a temperature of Maximum hardness is greater than or equal to 64HRC after tempering.Particularly, when the cold work tool of embodiment steel is used as height When stretching steel plate cold working mold, it is necessary to ensure hardness and impact value by applying post-curing.
Embodiment
Hereinafter, reference implementation example is described in detail the present invention.
Steel respectively with chemical composition (quality %) as shown in Table 1 and Table 2 is melted in vacuum induced furnace, and is cast into Each ingot with 50kg weight.These ingots after casting are hot-forged and form 60mm2Each bar (rod material). After hot forging, these bars are subjected to spheroidizing (spheroidizing annealing), wherein the material is from 880 DEG C with 7 DEG C/when cooling velocity slowly cool down.Evaluate hardness measurement test, the Charpy impact test (Charpy of each gained Steel material Impact Test), machinability test and the measurement of the retained austenite scale of construction test.
<hardness measurement test>
The cube test piece that side length is 10mm is cut out from the bar after above-mentioned heat treatment, and as shown in table 3 It is handled under heat treatment condition (hardening heat and tempering temperature).By the measuring surface and ground plane of cube test piece (grounding surface) is ground to #400.Then, cube test piece is measured by using Rockwell C Scale Hardness.The hardness shows be greater than or equal to maximum hardness when carrying out tempering at a temperature of 450 DEG C.
<Charpy impact test>
It prepares 10R- notch card and finishes test film, wherein the 2mm notch with 10R depth is formed in from above-mentioned 60mm2Stick In the square bar of the 10mm × 10mm cut out on material × 55mm.10R- notch card finishes test film in temperature as shown in table 3 Under carry out quenching treatment and tempering, then measure its impact value at room temperature.The average value of three test films obtains as punching Hit value.
<machinability test (end mill(ing) cutter (End Mill) processing experiment)>
Machinability test is carried out to the following tests piece cut out from Steel material after annealing.Experimental condition is as follows.
Test film: 55mm × 55mm × 200mm
Cutting element: the square end mill(ing) cutter (φ 10mm) of superhard M20
Cut distance: 10m
Cutting speed: 100m/min
Each revolution of travelling speed: 0.2mm/rev
Cut width (horizontal direction): 0.5mm
Cut height (vertical direction): 0.5mm
Cutting oil: nothing
In evaluation, after machining 10m, end mill(ing) cutter is separated with bracket, and measure the angle part of square end mill(ing) cutter Maximum abrasion loss.The maximum of the angle part of square end mill(ing) cutter is measured by using the actual measurement of the CCD camera of 3 times of magnifying powers Abrasion loss.Herein, " the maximum abrasion loss of the angle part of square end mill(ing) cutter " shows the elder generation from the angle part of square end mill(ing) cutter Hold the maximum value for being able to confirm that the distance at position of removing (peeling) and abrasion.
<measurement of the retained austenite scale of construction is tested>
It will be from 60mm2Bar on the square bar of 10mm × 10mm × 2mm that cuts out in quenching temperature as shown in table 3 Degree is lower to be maintained 30 minutes, then cooling with the average cooling rate of 50 DEG C/min.Next, by square bar (test film) Measuring surface is ground to the #800 defined such as JIS-R6001, and is measured by X-ray diffraction device.Iron element is obtained by x-ray measurement The peak intensity of (200) of the peak intensity of (200) and (211) of body and austenite, (220) and (311), then by peak intensity than counting It calculates the retained austenite scale of construction (volume %).
In Tables 1 and 2, steel of the present invention is shown and compares the chemical composition of steel.In table 3, steel of the present invention is shown and compares steel Heat treatment condition and test result.In addition, in Fig. 1, steel of the present invention is shown and compare the tool abrasion loss (machinability) of steel with Relationship between the additive amount of Mo, W and V.In Fig. 2, steel of the present invention is shown compared between the impact value of steel and the numerical value of hardness Relationship.
Table 3
Contrast table 1, table 2, table 3, Fig. 1 and Fig. 2, it is possible to find following facts.Firstly, in relatively steel 1 to 6,1.66 (Mo+ 1/2W)+V is greater than or equal to 5.7.For this reason, tool abrasion loss increases, and the productivity of mold reduces.Specifically, join According to Fig. 1, wherein steel 1 to 6 is compared in point expression of 1.66 (Mo+1/2W) more than or equal to 5.7.In contrast, wherein 1.66 (Mo+ 1/2W) point less than 5.7 indicates steel 1 to 9 of the present invention and compares steel 7 to 12.As shown in table 1, as 1.66 (Mo in alloy composite + 1/2W) be greater than or equal to 5.7 when, tool abrasion loss increase, machinability reduce, and mold productivity reduce.
Referring to table 1, table 2, table 3 and Fig. 2, because one or both of S and V are more than the upper limit of limitation range of the invention, institute To compare steel 8 to 12 with low impact value.
Referring to table 1, table 2, table 3 and Fig. 2, because the content of Si, Mo and V are lower than the lower limit and Cr of limitation range of the invention Content is more than the upper limit of limitation range of the invention, so comparing steel 13 cannot achieve sufficient hardness.In addition, because C content More than the upper limit of limitation range of the invention, so comparing steel 13 with low impact value.
Referring to table 1, table 2 and table 3, because the content of Mo and V is super lower than the lower limit and Cr content of limitation range of the invention The upper limit of limitation range of the invention is crossed, so comparing steel 14 cannot achieve sufficient hardness.In addition, because C content is more than this The upper limit of the limitation range of invention, so comparing steel 14 with low impact value.Incidentally, the comparison steel 16 in table 3 is to form Steel 14 is identical compared in table 2 and tempering temperature and hardening heat are different from being tried under conditions of the comparison steel 14 in table 3 The example tested.
Referring to table 1, table 2 and table 3, because the content of C, Mo and V are lower than the lower limit and Cr content of limitation range of the invention More than the upper limit of limitation range of the invention, so comparing steel 15 cannot achieve sufficient hardness.
In contrast, hardness measurement test, Charpy impact test, machinability test and the retained austenite scale of construction measurement In any test result of test, relative to these comparison steel, steel of the present invention realizes excellent result.From the above, according to The cold work tool steel of the present embodiment can improve mold while the necessary hardness for ensuring mold and necessary impact value Productivity.
Although describing the present invention in detail with reference to its specific embodiment, it will be apparent, however, that can make wherein each Kind changes and changes and be not only restricted to these embodiments and embodiment.
Japanese patent application 2014-125901 that the application was submitted based on June 19th, 2014, on October 28th, 2014 mention The Japanese patent application 2014-243681 that the Japanese patent application 2014-218985 of friendship and on December 2nd, 2014 submit, in Appearance is incorporated by reference into herein.

Claims (4)

1. a kind of cold work tool steel comprising, in terms of quality %:
C:0.70% to 0.90%；
Si:0.60% to 0.80%；
Mn:0.30% to 0.50%；
P:0.30% or less；
S:0.027% or less；
Cu:0.01% to 0.25%；
Ni:0.01% to 0.25%；
Cr:6.0% to 7.0%；
Mo+1/2W:2.50% to 3.00%；
V:0.70% to 0.85%；
N:0.020% or less；
O:0.0100% or less；With
Al:0.100% hereinafter,
Surplus be Fe and inevitable impurity,
Wherein meet 1.66 (Mo+1/2W)+V < 5.7%,
Its retained austenite scale of construction after quenching is less than or equal to 25 volume %.
2. cold work tool steel according to claim 1, further comprises, below at least one in terms of quality % Kind:
Nb:0.001% to 0.30%,
Ta:0.001% to 0.30%,
Ti:0.20% hereinafter, and
Zr:0.001% to 0.30%.
3. cold work tool steel according to claim 2, the retained austenite scale of construction after quenching be less than or equal to 25 volume %.
4. cold work tool steel according to any one of claims 1 to 3, at a temperature of being greater than or equal to 450 DEG C Tempering after maximum hardness be more than or equal to 64HRC.
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Applications Claiming Priority (6)

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JP2014-125901 2014-06-19
JP2014-218985 2014-10-28
JP2014218985 2014-10-28
JP2014243681A JP6439227B2 (en) 2014-06-19 2014-12-02 Cold work tool steel
JP2014-243681 2014-12-02

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