CN101316943B

CN101316943B - Steel for hot tooling, and part produced from said steel, method for the production thereof, and uses of the same

Info

Publication number: CN101316943B
Application number: CN2006800446707A
Authority: CN
Inventors: 尼古拉斯·比诺; 安德烈·格雷利耶; 皮埃尔-埃马纽埃尔·里奇
Original assignee: Aubert and Duval SA
Current assignee: Aubert and Duval SA
Priority date: 2005-11-29
Filing date: 2006-11-28
Publication date: 2012-07-04
Anticipated expiration: 2026-11-28
Also published as: CN102851608A; IL191569A0; CN101316943A; EP1954846A1; TW200734471A; FR2893954A1; KR20080073762A; AR057195A1; FR2893954B1; HK1122072A1; US20080302501A1; BRPI0620491A2; JP2009517546A; WO2007063210A1

Abstract

The invention relates to steel for hot tooling, the composition of said steel being made up of the following weight percentages: 0.30 % = C = 0.39 %, 4.00 % = Cr = 6.00 %, traces = Si = 0.50 %, traces = Mn = 0.80 %, traces = W = 1.45 %, traces = Co = 2.75 %, 0,80 % = Ni = 2.80 %, 1.50 % = Mo = 2.60 % with 1.50 % = Mo + 0.65W = 3.20 %, 0.55 % = V = 0.80 %, with 0.65 = K = 0.65, where K = K2 - K1 and K2 = 0.75 x (Ni 0.60), K1 = 1.43 x (V 0.40) + 0.63 x [(Mo + 0.65W) 1.20], traces = Al = 0.080 %, traces = S = 0.0040 %, traces = P = 0.0200 %, traces = Ti = 0.05 %, traces = Zr = 0.05 %, traces = Nb = 0.08 %, traces = N = 0.040 %, 10 P + As + 5 Sb + 4 Sn = 0.21 %, traces = O = 30ppm, the remainder being iron and inevitable impurities. The invention also relates to a part produced from said steel, to the method for the production thereof, and to the use of the same.

Description

The parts and method of manufacture and the purposes that are used for the steel of hot forming tool, process by said steel

Invention field

The technical field that the present invention relates to is the steel that is used for hot forming tool, and said steel can be used for casting and molded, forges, and draws or pushes.

Summary of the invention

Of the present invention one preferred but Application Areas that be not limited thereto is to produce to be used at casting under pressure based on the alloy in lightweight of aluminium or magnesium or the large size mould of copper alloy (cuprous alloys).

In application process, the instrument that thermoforming is used will stand pulsating stress, and this can cause their damage.

The generation source of these stress is:

-by the mechanical mechanical stress that causes like (pressing machine) direct acting reactive force;

-thermal stresses: owing to alternately contact hot material to be transformed and sprayed the cooling of lubricating oil or refractory paint, temperature is changed suddenly, thereby produce swell gradients, this is the reason that produces local mechanical stress.

In some cases, destruction is because unexpected fracture causes, and when the toughness of material was not enough, this fracture can cause the moment of instrument to damage.Usually this is caused by crackle, and this crackle produces in an initial hundreds of working cycle of using, and development gradually until after tens thousand of or hundreds thousand of circulations, makes instrument generation catastrophic explosion then.This process is commonly referred to " thermal fatigue ".

Destruction that thermal fatigue resistance caused has enough toughness when requiring the valley of temperature in the thermal cycling process.This character generally be with the impact bending of standard test specimen can and measure, sample to be tested is between envrionment temperature and 150 ℃.Also require in use, in working cycle, have enough hardness and softening resistance during the temperature vertex.

The production of large size mould or instrument (as having the thickness greater than 200mm) requires their steel of preparation to have higher performance.In quenching process; Because speed of cooling is through being confined to the hot-fluid nature demulcent on surface; And the producer is concerned about is that parts are indeformable or do not damage, and therefore said steel can not produce and account for most marquench structures, and this structure can obtain best use properties.For each compsn, QCC figure (Cooling Quenching continuously) can describe the character of the phase that forms according to speed of cooling, still well-knownly is, this figure can't calculate flexible loss amount in quenching/Annealed Strip that the reduction owing to quenching velocity causes.

Known steel with this purposes can be:

-AISI H11 steel, it approximately contains C=0.40%, Si=0.90%, Mn=0.40%, Cr=5%, Mo=1.30%, V=0.5%;

-AISI H13 steel, identical with the former, difference is to comprise V=0.95%;

-W-1.2367 steel, it approximately contains C=0.40%, Si=0.30%, Mn=0.40%, Cr=5%, Mo=2.9%, V=0.65%;

-the steel that can compare with AISI H11, but contain Si=0.3% and Ni=0.2% (referring to EP-B1-0 663 018); The composition of its nominal is C=0.3-0.4%, Si≤0.8%, Mn≤0.8%, Cr=4.5-5.8%, Mo=0.75-1.75%; V≤1.3%, W≤1.5%, Ni≤0.5%, P≤0.008%; Sb≤0.002%, Sn≤0.003%, As≤0.005%, and 10P+5Sb+4Sn+As≤0.10%.

In order to improve the performance of these known steel, carried out a lot of researchs, these researchs are paid close attention to is to obtain better balance between the stability (particularly hardness) of performance when hardness, toughness and use.Therefore, with respect to the H11 steel, through improving the content of Mo and V in the steel, can improve the patience when being heated, yet this has but caused the flexible reduction like above-mentioned H13 steel and W-1.2367 steel.On the other hand,, toughness can be improved, also quenchability can be improved if reduce the content of Si or add Ni.But Ni can reduce hardness and the ys when being heated.

The purpose of this invention is to provide a kind of steel that is used for the new grade of hot forming tool, it has obtained excellent balance between each item performance that preceding text are mentioned.

For this reason, the present invention relates to a kind of steel that is used for hot forming tool, have composition as expressed in weight percent:

-0.30％≤C≤0.39％

-4.00％≤Cr≤6.00％

-trace≤Si≤0.50%

-trace≤Mn≤0.80%

-trace≤W≤1.45%

-trace≤Co≤2.75%

-0.80％≤Ni≤2.80％

-1.50%≤Mo≤2.60% and 1.50%≤Mo+0.65W≤3.20%

-0.55％≤V≤0.80％

-and-0.65≤K≤0.65

K=K2-K1 in the formula

K2＝0.75×(Ni-0.60)

K1＝1.43×(V-0.40)+0.63×[(Mo+0.65W)-1.20]

-trace≤Al≤0.080%

-trace≤S≤0.0040%

-trace≤P≤0.0200%

-trace≤Ti≤0.05%

-trace≤Zr≤0.05%

-trace≤Nb≤0.08%

-trace≤N≤0.040%

-10P+As+5Sb+4Sn≤0.21％

-trace O≤30ppm

All the other are iron and unavoidable impurities.

Preferably, 0.33%≤C≤0.38%.

Preferably, trace≤Si≤040%.

Preferably, trace≤Mn≤0.60%.

Preferably, 4.6%≤Cr≤6.0%.

Preferably, 1.60%≤Mo≤2.00% and 1.60%≤Mo+0.65W≤2.20%.

Preferably, trace≤Al≤0.030%.

Preferably, trace≤S≤0.0010%.

Preferably, trace≤P≤0.0080%.

Preferably, trace≤Ti≤0.01%.

Preferably, trace≤Zr≤0.02%.

Preferably, trace≤Nb≤0.01%.

Preferably, trace≤N≤0.01%.

Preferably, 10P+As+5Sb+4Sn≤0.10%.

Preferably, trace≤O≤15ppm.

Preferably ,-0.35≤K≤0.35.

Preferably:

-0.335％≤C≤0.375％

-1.50％≤Ni≤2.10％

-1.60%≤Mo+0.65W≤2.20% and 1.60%≤Mo≤2.00%

-0.62％≤V≤0.75％。

Preferably:

-0.335％≤C≤0.375％

-2.00％≤Ni≤2.40％

-1.80%≤Mo+0.65W≤2.90% and 1.80%≤Mo≤3.40%and W≤0.90%

-0.66％≤V≤0.76％。

Preferably:

-0.335％≤C≤0.375％

-0.90％≤Ni≤1.50％

-1.50%≤Mo+0.6W≤1.90% and W≤0.40%

-0.55％≤V≤0.63％。

Preferably:

0.335%≤C≤0.375%, 4.60%≤Cr≤6.00%, trace≤Si≤0.40%, trace≤Mn≤0.60%; Trace≤W≤1.45%, trace≤Co≤2.75%, 1.50%≤Ni≤2.10%, 1.60%≤Mo+0.65W≤2.20% and 1.60%≤Mo≤2.00%; 0.62%≤V≤0.75%, and-0.35≤K≤0.35, trace≤Al≤0.030%, trace≤S≤0.0010%; Trace≤P≤0.0080%, trace≤Ti≤0.011%, trace≤Zr≤0.02%; Trace≤Nb≤0.01%, trace≤N≤0.01%, trace≤O≤15ppm.

The invention still further relates to the preparation method of the parts that are equipped with by steel, it is characterized in that: said steel is equipped with by aforementioned steel, and under 1000～1050 ℃, carries out austenitic transformation, quenches then.

Preferably, austenite transformation temperature is 1015～1040 ℃.

Preferably, after the quenching, said parts under 550～650 ℃, are carried out double tempering at least, the hardness that makes said parts is 42～52HRC.

The invention still further relates to the parts that the steel that made by aforesaid method is equipped with, it is characterized in that: said parts are thermoforming parts with instrument.

Said parts have the thickness more than or equal to 200mm.

Said parts are the moulds that are used at casting under pressure alloy in lightweight or copper alloy.

Said parts are forging toolses.

Said parts are forging dies.

Said instrument is boring or the rolling tool that is used for steel pipe.

Said parts are the instruments that are used for glass ware forming.

Said parts are the instruments that are used for plastic shaping.

Said parts prepare with following steel: 0.335%≤C≤0.375%; 2.00%≤Ni≤2.40%; 1.80%≤Mo+0.65W≤2.90% and 1.80%≤Mo≤3.40% and W≤0.90%, 0.66%≤V≤0.76%, and said parts are extrusion dies of used in aluminium alloy casting.

The invention still further relates to the purposes of the parts of the instrument that is used for thermoforming; It is characterized in that: said parts are prepared by following steel: 0335%≤C≤0375%; 2.00%≤Ni≤2.40%; 1.80%≤Mo+0.65W≤2.90% and 1.80%≤Mo≤3.40% and W≤0.90%, 0.66%≤V≤0.76%, and its surperficial working temperature keeps below 680 ℃.

The invention still further relates to the purposes of the parts of the instrument that is used for thermoforming; It is characterized in that: said parts are prepared by following steel: 0.335%≤C≤0.375%; 0.90%≤Ni≤1.50%; 1.50%≤Mo+0.6W≤1.90% and W≤0.40%, 0.55%≤V≤0.63%, and its surface temperature keeps below 770 ℃ when using.

Will be understood that with the known steel that preceding text are mentioned and compare that especially the steel among the EP-B1-0 663 018 is compared, the present invention has particularly made the mutual simultaneously coupling of softening Ni with the elements Mo and the V of stabilization and their attenuations that neutralizes.All these make quenchability be improved, thereby on big parts, reproduce these performances, and these performances can only obtain on widget before this.

Pass through its surperficial transient heat flow when hot forming tool uses because the contriver at first is devoted to effectively to measure, thereby make the one-tenth of optimizing steel of the present invention be divided into possibility.Then, the contriver derives through calculating the transient heat stress that causes owing to thermal shocking (said thermal shocking meeting causes the generation of crackle).Mechanical behavior when this can understand material work better.Because the experiment measuring that on the sample that reappears industrial quenching velocity, carries out, and thermodynamics simulation, the contriver has been able to set up the composition of steel, heat treatment parameter before using and the contact between the microtexture.Particularly, the contriver confirms, the influence that the interdependent property between component and the quenching temperature has particularly important to the balance that obtains various mechanical properties, and these mechanical properties have the effect of particularly important to the steel that is used for hot forming tool.

Through the description of reading hereinafter and with reference to accompanying drawing, can understand the present invention better:

What-Fig. 1 showed is, along with the variation of permissive temperature, reference group compound (Fig. 1 a)～Fig. 1 e)) and compsn of the present invention (Fig. 1 f)) the mark of undissolved carbide change.

-Fig. 2 is with reference to steel (Fig. 2 is a)) and steel of the present invention (Fig. 2 b)) the QCC curve.

-Fig. 3 is the comparison of the energy-to-break after different reference sample and sample of the present invention quench, and this quenching is carried out under laboratory condition He under the industrial condition.

Test is on the sample with the listed component of table 1, to carry out, the description that concrete testing method vide infra.In this table, COEFFICIENT K 2, K1 and K are corresponding to following amount, and wherein content is represented with wt%:

K2＝0.75×(Ni-0.60)

K1＝1.43×(V-0.40)+0.63×[(Mo+0.65W)-1.20]

K＝K2-K1

The present invention is based on the effect of elemental carbon, chromium, molybdenum, vanadium and nickel and Study of Interaction basically, and before quenching austenite transformation temperature to the research of the influence of the mechanical property of the steel studied.

The influence of austenite transformation temperature:

Austenite transformation temperature has determined the distribution of alloying element between undissolved carbide and matrix.Along with the rising of temperature, the amount of undissolved carbide raises always.

In final product, undissolved carbide must keep a suitable content, so that the control grain-size.For guaranteeing toughness and fatigue resistence, thin grain-size is necessary.

The alloying element that is dissolved in the matrix is being controlled quenchability, anti-annealing property and generally speaking all mechanical properties.

Table 2 is that the quenching temperature of one of compsn (with reference to melt 10) of research is to microtexture and Effect on Performance.

The experiment foundry goods of table 2-reference example 10: austenite transformation temperature to microtexture (Elements C with The distribution of V) and the influence of mechanical property

When the carbide dissolving of vanadium increased gradually, in this case, anti-remollescent improved and loss in toughness when the rising of austenite transformation temperature can cause being heated.

This shows, obtain satisfying the most optimum materials of intended use, must consider component and austenitic transformation condition simultaneously.The software for calculation that adopts the metallurgist generally to use

Describe balancing each other, carry out the thermodynamics simulation through this description, thereby, provide about undissolved each carbide (VC, M for each element ₂₃C ₆And M if possible ₆C, Fe ₃C, M ₂C ...) the information of amount.Fig. 1 draws by this simulation.Shown in Figure 1 is, along with the variation of austenite transformation temperature, five reference group compounds (Fig. 1 a)～Fig. 1 e)) and a compsn of the present invention (Fig. 1 f)) the fractional of undissolved carbide change.

Set up between elements Mo and the V competitive relation that fixes carbon through their preferred carbide forms well.The adding of nickel only produces secondary role (secondary effect) to this mechanism.

Observation to the experiment microtexture under the crude as-quenched condition has confirmed the mimic anticipation trend.Through following principle, austenite transformation temperature is optimized:

-under suitable temperature, carbide M ₆C and M ₂₃C ₆, not very effective to the control of grain-size, must be dissolved, so that metallic element M and C discharge, be the offer the best potentiality of quenchability of matrix.

-according to thermodynamics simulation, the minimum value of the x of the carbide of undissolved vanadium is that 0.20% magnitude is necessary, can guarantee the homogeneous of crystal grain and tiny like this; Austenite transformation temperature must keep below corresponding threshold value.

-for this reference, must consider specified temp 10～15 ℃ deviation up and down, the temperature distribution that this is common during corresponding to industrialized mass production.

The austenite transformation temperature of different compositions, in table 3, summarize:

table 3: the desirable austenite transformation temperature of different experiments melt.

The definition of the compsn of optimizing and the observed value of key property:

As stated, a basic purpose of the present invention has comprised the balance of carrying out to following aspect:

-on the one hand, and molybdenum, vanadium and the optional tungsten that exists, the softening and softening resistance during to operation is favourable, but attenuation (weakening effect) is arranged.

-on the other hand, nickel helps improving toughness, but impair the hardness when being heated.

What need know is; Steel of the present invention is when being heated; Enough hardness must be arranged to avoid depression (recessing) and antifatigue, in first order of solution, the hardness when they are heated has identical relation with hardness under 20 ℃; Under 20 ℃ of identical down stiffness conditions, quenching and tempering heat treatment state are compared.Previously selected hardness is 47,45 and 42HRC.

According to original creation method of the present invention; To (being chosen to be 22 ℃ of PMs with laboratory sample that quenches at a high speed and the sample that on experimental installation, reappears the quenching velocity of typical industrial part; TR is 900/400 ℃), carried out systematically and measurement side by side.

This measurement comprises:

-variation along with 2 hours tempering temperature of 2 temper is described, the variation of hardness, thus the tempering of confirming to carry out is to obtain the hardness of expectation;

-through measuring the hardness loss amounts that cause after keeping 80 hours down owing at 560 ℃, obtaining softening resistance, the initial hardness value is 47HRC;

-under+20～200 ℃ of differing tempss, the impact bullet bending energy when destroying through the V-notch impact specimen is measured toughness.

Austenite is transition point (Re-austenisation point Ac1) again:

In operation, necessarily can not surpass this point, because the structure of parts material can change, this will cause the noticeable change of mechanical property.

Shown in the table 4 is the most representative result who obtains from different samples, and this influence that confirms Mo and V element is not obvious; On the other hand, along with the rising of nickel content, the Ac1 point reduces.Therefore, when operation, in the application scenario of surface temperature very high (as in some forging toolses), must avoid the high compsn of nickel content; But they also have multiple purposes, like the mold of alloy in lightweight, and their surface temperature milder.

Table 4-austenite changes the relation of Ac1 point and component again

Foundry goods	Nickel (%)	Molybdenum (%)	Vanadium (%)	The Ac1 point (℃)
					1	0.06	1.21	0.47	825
7	0.08	2.29	0.57	820
					8	0.15	1.62	0.64	805
12	1.42	1.21	0.46	770
					13	2.93	1.23	0.47	680

20	0.59	2.14	0.77	800
					22 (the present invention)	1.63	1.82	0.71	755
23 (the present invention)	1.05	1.78	0.70	785
					26 (the present invention)	2.19	2.28	0.70	710

Softening when temper resistance and anti-operation

Be that alloying element anti-hardness when being in high temperature reduces the influence of property shown in the table 5.

The hardness value that obtains after the double tempering is 47 and 42HRC, and tempering temperature is 550 ℃ for the first time, and tempering for the second time is to carry out under the characteristic temperature that in table, occurs.

The initial value that the hardness loss is measured is 47HRC.

Shown in the table 5A is to be higher than two samples 12 of said reference sample and the result that sample 13 obtains from reference sample 1 and nickel content.Table shown in the 5B is that content from sample 1, Mo and possible V is higher than the result that sample 3, sample 5, sample 6 and the sample 8 of sample 1 obtain.Table shown in the 5C is the result who obtains from sample 8 and sample 22 and sample 6 and sample 26, and the content of their Ni, Mo and V is higher than sample 1.

Table 5-is when keeping a segment length after the time, and alloying element is to the influence of the tempering temperature and the property of softening

Table 5-A shows the detrimental effect that adds nickel simply and caused---for given hardness, highly significant ground reduces tempering temperature, and maintenance one segment length increases the hardness loss amount after the time under heating status.The reduction of tempering temperature has destructiveness, because for fear of overbating, steel must provide its possible maximum operating temperature, is at least 600～630 ℃.

Because the surface temperature of parts is usually near 520-560 ℃ when the injection (injection) of aluminium, when forging even higher, in order to confirm whether given compsn can satisfy given application requiring, and this index is a considerable important factor.

Table 5-B shows, adds simply on molybdenum and vanadium temper resistance and the softening resistance when improve operating to have favorable influence.On the other hand, the decline of quenching velocity has adverse influence to these parameters between laboratory condition and industrial condition, and this is because the quenchability deficiency of material causes.

Among the table 5-C about compsn to comparison shows that of (pairs) (8,22) and (6,26), under laboratory condition, the anti-hardness loss property of nickeliferous foundry goods will be lower than the low foundry goods of corresponding nickel content, still under industrial quenching conditions, their performance is very approaching.

Sum up: under industrial heat-treat condition, combination and add nickel, molybdenum and vanadium is evenly given material keeping temper resistance and the softening resistance of a segment length after the time, and the performance of these performances when not adding nickel is suitable.

These favourable results can explain through significantly improving of the quenchability shown in Fig. 2; Fig. 2 with the QCC of reference group compound 1 cool off continuously figure (Fig. 2 a) with the comparing of compsn 22 of the present invention (Fig. 2 b); Reference group compound 1 carried out austenitic transformation 30 minutes under 990 ℃, compsn 22 carried out austenitizing 30 minutes under 1030 ℃.

Compsn of the present invention has perlite phase region and bainite phase region, with respect to the reference group compound, can obviously offset the influence of low speed of cooling.Therefore; For pending instrument; According to the size of parts and in parts residing position, common industry quench (its mode illustrates with black matrix in Fig. 2 a and Fig. 2 b) make that reaching 400 ℃ at 1000～5000 seconds becomes possibility, compsn of the present invention can produce exclusive martensitic transformation.On the contrary, the reference group compound is essential to form a large amount of bainites, and this does not help the performance that obtains expecting so.

Toughness:

The disadvantageous effect that laboratory condition produces with the decline of industrial condition speed of cooling down down, at the V-notch impact specimen owing to receive and show more obviously on the energy-to-break of impacting the generation bending.

Shown in the table 6 be through screening result's canonical trend; Add Ni, Mo and V simultaneously foundry goods 21 of the present invention has been produced favorable influence; Because it is it handles elasticity number (resilience value) that the back obtains under industrial condition the highest, minimum by the reduction that the reduction of quenching velocity causes.

Table 6-is impacted owing to its periphery by the V-notch impact specimen that several typical foundry goods record The time energy-to-break that produces, wherein:

R: rapid quenching (oil quenching of sample)

L: quench at a slow speed (the industrial quenching velocity of reappearing in the laboratory).

Fig. 3 compares the value of all foundry goods; These values are to obtain behind quenching and the rapid quenching under the industrial speed forming identical metal; Wherein sample has been carried out anneal, obtaining 42,45 and the hardness of 47HRC, and sample destroys under 20 ℃ and 100 ℃.Each point has been represented the hardness value and the fail temperature of sample.The result shows, for compsn of the present invention because the hardness loss amount that the decline of quenching velocity causes wants much little.

The be pressed test result of the tool block that the condition of stating handles of the result's of lab investigation trend confirms:

Size 570 * 450 * 228mm of tool block

Be in the same position in the stove

At air pressure is under 5 crust, with identical gas flow rate, in identical industrial furnace, quenches

The temperature independent control of double tempering, with obtain 46+/-hardness of 0.5HRC

Choosing the V-notch impact specimen on the xsect: in big face, choose in the heart near the top layer of tool block and core position.

The MV of impact bending ability is seen table 7, and it has confirmed that steel 22 of the present invention has excellent performance, and particularly on the core position of tool block, larger sized parts can be represented in this position.

The test result of the impact bending ability of the tool block that table 7-handles under industrial condition

Foundry goods	Ni ％	Mo ％	V ％	The energy-to-break KV of perimeter sample (joule)	The energy-to-break KV (joule) of core position sample
						2	0.11	1.27	0.49	32	16
5	0.17	2.74	0.48	18	14
						7	0.08	2.29	0.57	23	20
9	0.25	1.59	0.66	24	19
						22 (the present invention)	1.63	1.82	0.71	28	26

All these Mechanical test results all show, reduce quenching velocity and have adverse influence, especially:

When hardness was identical, impact bending can reduce

560 ℃ of times that keep a segment length, the loss amount of hardness can increase

Yet for all compsns, the amplitude of these variations and inequality, verified according to hereinafter described rule simultaneously and add alloying element evenly, can significantly reduce this species diversity.

The effect of alloying element:

Performance and thermodynamics mimic performance through testing foundry goods compare Journal of Sex Research, can estimate the effect of various alloying elements and the interaction between them.Through following the rule that preceding text propose, confirmed following trend about quenching conditions:

CarbonFavourable to quenchability, can improve the ideal austenite transformation temperature, confirm the highest hardness that after 550 ℃ of following anneal, obtains.But, harmful to toughness.With high-load molybdenum or vanadium coupling, can cause the formation of eutectic carbides, this eutectic carbides is harmful to microtexture and toughness.Its content should be at least 0.30%, to obtain enough hardness, is at most 0.39% fatigue to avoid repairing.Best scope is 0.33～0.38%.

ChromiumFavourable to quenchability.In temper hardening, play an important role, and for the desired advantageous applications occasion of the present invention---(42～52HRC) large-size components, this specific character is favourable promptly to need high firmness.But the carbide of its generation can develop more stable status rapidly, and verified to reduce property for anti-hardness under the high temperature be not very effective.Therefore, be necessary to form element such as the Mo and the V of carbide, Cr is replenished with other.It is 4.0% less that the content of chromium element must be maintained to, and to obtain quenchability, is at most 6.0%, if surpass 6.0%, the effect of chromium can suppress the effect of V and Mo.Preferably, the content of chromium is 4.6%～6%.

MolybdenumCan improve quenchability.Itself and chromium coexistence are can improve the quantity of chromium base carbide in the chromium base carbide.When content was high, it formed specific M ₂C and M ₆C.Aspect macro property, it can improve hardness and temper resistance, reduces toughness.Its content is 1.50～2.60%.Also need consider the tungsten that possibly exist, this will explain hereinafter.Preferably, the content of Mo be 1.60～2.00% and Mo+0.65W be 1.60～2.20%.

VanadiumForm specific VC type carbide, on by experiment face that foundry goods covered, this carbide accounts for the sedimentary overwhelming majority, does not dissolve under these throw out austenite transformation temperatures, has guaranteed that therefore crystal grain can't grow up.In the drawing process of after quenching, implementing; Can precipitate the micron and the nano level carbonization thing that make new advances; And they through with the interaction of martensite lattice defect, receive during softening and operation at secondary in the softening resistance of doing the time spent of temperature and pulsating stress and play active effect.On the other hand, the excessive carbide that in drawing process, produces can cause the remarkable decline of performance.In the scope of the compsn that this paper studied, and follow sum up about the selection principle of austenite transformation temperature the time, the content of V is necessary for 0.55%～0.75%.

NickelHardness under the treated state has adverse influence; It can reduce the temperature of temper and the hardness and the softening resistance that obtain to expect.And in the TR that is adopted, the amount above 3% can significantly reduce austenite transition point again, and this definitely should be avoided.On the other hand, it is 1～3% o'clock that nickel can improve quenchability, particularly content, can also significantly improve toughness.The present invention is decided to be 0.80～2.80% with the content of Ni.The spinoff that a large amount of adding brought of nickel can compensate with Cr, Mo, V and the W of the said content of preamble.

TungstenOptional interpolation element, Mo+0.65W be 1.50～3.20% and the content of Mo be that W content is at most 1.45% under 1.50～2.60% the condition, when the content of Mo was 1.60～2.00%, the content of W was preferably 1.60～2.20%.In fact, tungsten can compensate the effect of molybdenum, and 1% tungsten is equivalent to 0.65% molybdenum.The adding of tungsten, limited to the spinoff that toughness and quenchability cause, when being heated, the softening resistance that particularly is higher than under the probe temperature of 560 ℃ (as 600 ℃) has active effect.

CobaltBe limited to 2.75% on adding.For softening resistance, when particularly residing temperature is 600 ℃ of orders of magnitude, be favourable; But it is unfavorable to quenchability.The price of considering this interpolation element is high, and not special recommendation is adopted.

And, between various performances, reach the ideal balance for when using, also require to add simultaneously evenly molybdenum, vanadium, nickel and possible tungsten, and satisfy following relation:

K is-0.65～+ 0.65, is preferably-0.35～+ 0.35, preferably as far as possible near zero, wherein:

K＝K2-K1

K2＝0.75×(％Ni-0.60)

K1＝1.43×(％V-0.40)+0.63×[％Mo+(0.65×％W)-1.20]

Can see that table 1 has been listed K1, K2, the K value of all foundry goods.

When satisfying following condition simultaneously, the result who obtains is best:

0.335％≤C≤0.375％；

1.50％≤Ni≤2.10％；

1.60%≤Mo+0.65W≤2.00% and Mo>=1.60%;

0.62％≤V≤0.75％。

For certain applications occasion more, also recommend to satisfy following condition:

0.335％≤C≤0.375％

2.00％≤Ni≤2.40％

1.80%≤Mo+0.65W≤2,90% and 1.80≤Mo≤2.40% and W≤0.90%

0.66％≤V≤0.76％

The application scenario: in order to produce the large-size components of for example casting the extrusion die that the Al alloy uses, and need obtain excellent quenchability the time, consider to reduce phase transition point Al through Ni, the working temperature on surface keeps below 680 ℃.

0.335％≤C≤0.375％

0.90％≤Ni≤1.50％

1.50%≤Mo+0.65W≤1.90% and W≤0.40%

0.55％≤V≤0.63％

Application scenario: when surface temperature is lower than 770 ℃ application for the performance requriements that satisfies middle-sized parts and when being suitable for work.

In addition, also need mention other elements, they must or can be to confirm that content limit exists.

SiliconSince harmful to toughness, under the prerequisite that industrial cost can allow, keep low levels, the limit that can not surpass is 0.50%, preferred limit is 0.40%.

ManganeseFavourable to quenchability, but harmful to toughness, content can not exceed 0.80%, preferably can not surpass 0.60%.

Elementary sulfur, phosphorus, arsenic, tin, antimony, titanium, zirconium, niobium, nitrogenUnfavorable to toughness, when operation, can produce attenuation, must be limited to the minimum content that industry and economical means can reach.The maximum content that allows is:

S:0.0040% is preferably 0.0010%

P:0.0200% is preferably 0.0080%

Ti:0.05% is preferably 0.01%

Zr:0.05% is preferably 0.02%

Nb:0.08% is preferably 0.01%

N:0.0400% is preferably 0.0100%

And the content of P, As, Sb and Sn must satisfy:

10P+As+5Sb+4Sn≤0.21%, preferred≤0.10%.

AluminiumContent be necessary for trace～0.080%, be preferably trace～0.030%.Its effect is the oxygen of removing in the steel, therefore can limit the amount of the oxide inclusion in the steel, and this oxide compound can cause the fatigue resistence of steel to descend especially.Content based on this reason oxygen must can not surpass 30ppm, preferred 15ppm.High-load Al has reduced the O content that is dissolved in the liquid steel, but this also makes liquid steel when casting, reoxidize more sensitivity of effect to atmospheric, thereby has improved the risk that forms harmful oxide inclusion.

By general method, steel of the present invention can be divided into two grades.

" standard " grade, for each element in the compsn, when its content is not when definitely being within the optimum range of preceding text definition, acquisition be exactly " standard " grade.Compared with prior art, its raising part is quenchability.This can produce has all large size products of homogeneous of high firmness and whole prod various piece.

" high-quality " grade, when the content of each element all is within the optimum range of preceding text definition, acquisition be exactly " high-quality " grade.In this case, except having improved quenchability, can also obtain H.T., and H.T. and the high firmness good thermal fatigue resistance and anti-fracture suddenly that bring simultaneously.

In order to obtain this result; A kind of like this method is necessary to seek help; This method comprises; After in electric furnace and ladle, carrying out first refining, adopt var technology (vacuum arc refusion) (VAR) or electrode conductivuty slag remelting processing (electroconductive slag refusion) (ESR) carry out the remelting of consumable electrode, this especially can guarantee desired very low O content.Likewise, as to the common processing of doing of the steel of these types, be necessary cast steel is rolled and the annealed thermodynamic process, this thermodynamic process can make the structure of steel tight, in conjunction with, fine and closely woven and homogeneous; Also be cured process simultaneously, it can produce very little and not be separate dendrite.

In general parts in that the steel of producing according to method mentioned above of the present invention can prepare, comprise the parts of thermoforming with instrument, especially:

-parts are the mold and pattern for casting tools under the extruding of alloy in lightweight or copper alloy;

-forging die;

-be used for the boring or the rolling tool of steel pipe.

The shaping jig of-glass and plastic material.

It is 200mm or higher parts that the present invention is preferred for producing thickness.

Claims

1. produce the method for steel part, it is characterized in that: said parts are with the steel that is used for hot forming tool with following component as expressed in weight percent, under 1000～1050 ℃, carry out austenitic transformation, quench then, thereby prepare:

-0.30％≤C≤0.39％

-4.00％≤Cr≤6.00％

-trace≤Si≤0.50%

-trace≤Mn≤0.80%

-trace≤W≤1.45%

-trace≤Co≤2.75%

-0.80％≤Ni≤2.80％

-1.50%≤Mo≤2.60% and 1.50%≤Mo+0.65W≤3.20%

-0.55％≤V≤0.80％

--0.65≤K≤0.65

K=K2-K1 in the formula

K2＝0.75×(Ni-0.60)

K1＝1.43×(V-0.40)+0.63×[(Mo+0.65W)-1.20]

-trace≤Al≤0.080%

-trace≤S≤0.0040%

-trace≤P≤0.0200%

-trace≤Ti≤0.05%

-trace≤Zr≤0.05%

-trace≤Nb≤0.08%

-trace≤N≤0.040%

-10P+As+5Sb+4Sn≤0.21％

-trace≤O≤30ppm

Surplus is iron and unavoidable impurities.

2. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 0.33%≤C≤0.38%.

3. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Si≤0.40%.

4. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Mn≤0.60%.

5. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 4.6%≤Cr≤6.0%.

6. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 1.60%≤Mo≤2.00%, and 1.60%≤Mo+0.65W≤2.20%.

7. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Al≤0.030%.

8. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤S≤0.0010%.

9. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤P≤0.0080%.

10. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Ti≤0.01%.

11. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Zr≤0.02%.

12. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Nb≤0.01%.

13. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤N≤0.01%.

14. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 10P+As+5Sb+4Sn≤0.10%.

15. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤O≤15ppm.

16. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent :-0.35≤K≤0.35.

17. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

-0.335％≤C≤0.375％

-1.50％≤Ni≤2.10％

-1.60%≤Mo+0.65W≤2.20% and 1.60%≤Mo≤2.00%

-0.62％≤V≤0.75％。

18. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

-0.335％≤C≤0.375％

-2.00％≤Ni≤2.40％

-1.80%≤Mo+0.65W≤2.90% and 1.80%≤Mo≤2.40% and W≤0.90%

-0.66％≤V≤0.76％。

19. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

-0.335％≤C≤0.375％

-0.90％≤Ni≤1.50％

-1.50%≤Mo+0.65W≤1.90% and W≤0.40%

-0.55％≤V≤0.63％。

20. method according to claim 1 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

0.335%≤C≤0.375%, 4.60%≤Cr≤6.00%, trace≤Si≤0.40%, trace≤Mn≤0.60%; Trace≤W≤1.45%, trace≤Co≤2.75%, 1.50%≤Ni≤2.10%, 1.60%≤Mo+0.65W≤2.20% and 1.60%≤Mo≤2.00%; 0.62%≤V≤0.75% ,-0.35≤K≤0.35, trace≤Al≤0.030%, trace≤S≤0.0010%; Trace≤P≤0.0080%, trace≤Ti≤0.011%, trace≤Zr≤0.02%; Trace≤Nb≤0.01%, trace≤N≤0.01%, trace≤O≤15ppm.

21. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Si≤0.40%.

22. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Mn≤0.60%.

23. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 4.6%≤Cr≤6.0%.

24. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 1.60%≤Mo≤2.00%, and 1.60%≤Mo+0.65W≤2.20%.

25. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Al≤0.030%.

26. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤S≤0.0010%.

27. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤P≤0.0080%.

28. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Ti≤0.01%.

29. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Zr≤0.02%.

30. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤Nb≤0.01%.

31. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤N≤0.01%.

32. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: 10P+As+5Sb+4Sn≤0.10%.

33. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent: trace≤O≤15ppm.

34. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent :-0.35≤K≤0.35.

35. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

-0.335％≤C≤0.375％

-1.50％≤Ni≤2.10％

-1.60%≤Mo+0.65W≤2.20% and 1.60%≤Mo≤2.00%

-0.62％≤V≤0.75％。

36. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

-0.335％≤C≤0.375％

-2.00％≤Ni≤2.40％

-1.80%≤Mo+0.65W≤2.90% and 1.80%≤Mo≤2.40% and W≤0.90%

-0.66％≤V≤0.76％。

37. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

-0.335％≤C≤0.375％

-0.90％≤Ni≤1.50％

-1.50%≤Mo+0.65W≤1.90% and W≤0.40%

-0.55％≤V≤0.63％。

38. method according to claim 2 is characterized in that: the said steel that is used for hot forming tool has following component as expressed in weight percent:

39. according to each described method of claim 1-38, it is characterized in that: the temperature of carrying out austenitic transformation is 1015～1040 ℃.

40. according to each described method of claim 1-38, it is characterized in that: after the quenching, said parts under 550～650 ℃, are carried out double tempering at least, the hardness that makes said parts is 42～52HRC.

41. by the steel part that the described method of aforementioned each claim is produced, it is characterized in that: said parts are thermoforming parts with instrument.

42. according to the described parts of claim 41, it is characterized in that: the thickness of said parts is more than or equal to 200mm.

43. according to the described parts of claim 41, it is characterized in that: said parts are the moulds that are used at casting under pressure alloy in lightweight or copper alloy.

44. according to the described parts of claim 41, it is characterized in that: said parts are forging toolses.

45. according to the described parts of claim 41, it is characterized in that: said parts are forging dies.

46. according to the described parts of claim 41, it is characterized in that: said parts are boring or the rolling tools that are used for steel pipe.

47. according to the described parts of claim 41, it is characterized in that: said parts are the instruments that are used for glass ware forming.

48. according to the described parts of claim 41, it is characterized in that: said parts are the instruments that are used for the plastic material moulding.

49. according to the described parts of claim 41, it is characterized in that: said parts are by claim 18 or 36 described method preparations, and said parts are the extrusion dies that are used for y alloy y.

50. the purposes of the said parts of claim 41 is characterized in that: said parts are by claim 18 or 36 described method preparations, and its surperficial working temperature keeps below 680 ℃.

51. the purposes of the said parts of claim 41 is characterized in that: said parts are by claim 19 or 37 described method preparations, and the surface temperature during its work keeps below 770 ℃.