Background technology
Along with the develop rapidly of China's economic level and the very big raising of industrialization degree, the application of various forging die moulds is also more and more general and important, how to utilize resource still less, produce the more better product of multimass, by a direction that is industrial development, so when forging die die design, must consider its performance and cost two aspects.In the prior art, usually adopt various die steel to manufacture forging die mould.Some die steel has the over-all propertieies such as good strong hardness and toughness, can meet forging die operating mode demand, but prevailing price is higher, and preparation technology's flow process is more, and the cycle is longer.And other die steel is not that hardness and intensity are too high, toughness plasticity is poor, adds the basil in man-hour position and easily bursts apart and peel off, and makes acute angle rust or damaged; Be exactly that hardness and intensity are lower, for keeping enough toughness plasticities, mould contact surface is because wearing and tearing comparatively fast compared with soft.Below either way will change the size and dimension of mould, thereby have a strong impact on dimensional precision and the surfaceness after processing.Even if mould again repairs a die and changes, also want cycle time expand, increase production cost, and being again installed and locating the processing quality that also will affect product of mould.
In sum, in existing forging die mould, the performance of mould and cost often can not be met simultaneously preferably.Have the die steel price of better hardness, intensity and toughness plasticity performance conventionally very expensive again, mold production process process is many.Therefore, find and a kind ofly can meet preferably the performance requriements of forging die mould aspect hardness, intensity and toughness plasticity two simultaneously, can reduce again the forging die preparation method of production cost and operation simultaneously, just become the art problem demanding prompt solution.
In order to solve the technical problem; contriver had once designed a kind of method technique of the preparing forging mould by double-layer metal resurfacing welding based on cast steel substrate and had applied for patent; the patent No. is ZL 200910104604X; in the method technique; adopt cast steel as forging die matrix, form waviness matrix surface, and by carry out double-layer metal resurfacing welding on base layer; tempering destressing again, the last machining moulding of mould.Like this, the forging die obtaining can meet forging die mould at the performance requriements of the aspects such as hardness, intensity and toughness preferably, can reduce again the forging die preparation method of production cost simultaneously; Realized the manufacture of low cost, less energy-consumption, short period of time, high utilization rate, high-level efficiency, high-performance and high benefit and used mould, die industry having been there is to the meaning that cannot estimate.
Contriver states in the process of method on the implementation, finds forging die that the double-deck bead-welding technology of this employing makes in the course of the work, and through use repeatedly, under pressing mold repeated stock, de-splitting easily appears in the overlay cladding of forging die.Therefore how guaranteeing, on the basis of forging die intensity, further to improve forging die matrix and overlay cladding bonding strength, become the new direction of this area research.
Summary of the invention
For above-mentioned the deficiencies in the prior art, the technical problem to be solved in the present invention is: how a kind of cast steel substrate of preparing forging die technique for double-deck built-up welding and preparation method thereof is provided, improve the matrix of forging die and the bonding strength between overlay cladding, and then improve Service Life of Forging Die.
After the forging die that existing double-deck bead-welding technology makes goes wrong in the course of the work, contriver analyzes and researches.Compare with cast iron, the castability of steel is poor.Because the fusing point of steel is higher, crystallization range is wider, therefore the flowing property of molten steel is poor; Shrink larger, therefore shrink and shrinkage porosite trend larger, foundry goods easily forms the defects such as hot tearing and cold cracking.In the chemical composition of conventional cast carbon steel, these five kinds, carbon, silicon, manganese, phosphorus, sulphur are fundamental elements, and wherein carbon can improve the content of pearlite in alloy in carbon steel, and the intensity of carbon steel is improved; Silicon and manganese also play admittedly molten strengthening to steel to a certain extent; Phosphorus can form the Fe of fragility
3p-compound, causes the plasticity and toughness of steel sharply to decline, and the brittle transition temperature of steel is raise, and forms " cold short "; Sulfur capacity easily forms FeS low melting point (its fusing point only has 985 ℃) at crystal boundary, and when the condition of high temperature is stressed, material can form crackle along crystal boundary, forms " hot-short ".
Although cast steel surface has Decarburized layer, in the place of nearly epidermis, do not have shrinkage cavity, metal is dense, thus according to cast steel surface layer metal design and direct on upper layer welding be all more satisfactory.And the welding property of cast steel is also closely related with its carbon equivalent, according to carbon equivalent calculation formula (following formula 1), major effect welding property element is C, Mn, Cr, Mo etc.Conventionally cast steel carbon content, below 0.3%, if impurity is few, does not have segregation phenomena, and this explanation weldability is good.If carbon content is more than 0.3%, or it is more to contain sulphur phosphorus impurities, just easily at weld, there is the defects such as sclerosis, crack.
Carbon equivalent=C+1/6Mn+1/24Si+1/15Ni+1/5Cr+1/4Mo (1)
Therefore forging die matrix carbon and alloying element content are high, and its intensity is high, but must cause weldability energy variation; And good welding property needs lower carbon equivalent, this also will inevitably affect forging die mechanical property.
Therefore in existing cast material, being difficult to meet casting matrix can have sufficiently high intensity simultaneously, to bear forging press operating pressure, do not break at work, be out of shape little, plasticity and toughness can be excellent; Can there is good welding property again, it is combined firmly with surface strengthening layer, during work, not come off.Have the die steel price of better hardness, intensity and toughness plasticity performance conventionally very expensive again, mold production process process is many.Need to again research and develop and a kind ofly can meet preferably the performance requriements of forging die mould aspect hardness, intensity and toughness plasticity two simultaneously, there is again the forging die cast material of excellent welding performance simultaneously
In order to solve the technical problem, in the present invention, adopted following technical scheme:
A kind of preparation method who prepares the cast steel substrate of forging die technique for double-deck built-up welding, its feature is, adopted the material being formed by following per-cent element: carbon element content 0.2%-0.35%, silicon content 0.1%-0.5%, manganese element content 1.0%-1.8%, phosphorus element content≤0.01%, element sulphur content≤0.01%, chromium constituent content 0.3%-0.8%, nickel element content 0.1%-0.8%, molybdenum element content 0.1%-0.5%, copper content≤0.5%, surplus is iron; After normalizing, the technique of tempering obtains, and wherein normalizing temperature is 980-1020 ℃; Tempering temperature is 550-600 ℃.Soaking time size belongs to common practise, and concrete size can determine according to die size.The cast steel substrate that adopts present method to obtain, after tested, its mechanical performance index can reach: σ
s(yield strength)>=380MPa, σ
b(tensile strength)>=590MPa, δ (unit elongation)>=14%, ψ (shrinking percentage)>=30%, AKv (40 ℃)>=27J.
In technique scheme, redesigned the degree of material element, wherein: the mass percent of forging die cast steel substrate carbon containing is 0.2%-0.35%.This is all poor because of the hot tearing drag of the lower steel of carbon content and high carbon steel, easily form hot tearing, and the hot tearing drag of the steel that the mass percent of carbon containing is 0.2%-0.3% is all relatively good, is difficult for forming hot tearing; Soft steel plasticity is better simultaneously, is not easy to produce cold cracking; High carbon steel plasticity is poor, easily produces cold cracking.
The siliceous mass percent of forging die cast steel substrate is 0.1%-0.5%.This is because silicon does not form carbide in steel, only forms sosoloid.In ferrite, form solution strengthening effect, thereby make the intensity of steel and hardness increase, but plasticity declines to some extent.In steel, silicon content surpasses after 3%, and the decline of plasticity and toughness is particularly remarkable.
Forging die cast steel substrate is 1.0%-1.8% containing the mass percent of manganese.Because manganese can be offset the deleterious effect of sulphur to a certain extent, contribute to prevent that hot tearing from forming, and make steel keep high plasticity, reduce steel tough-brittle transition temperature, simultaneously available its replaces the effect of part of nickel, to save valuable nickel and to reduce costs.But it also can increase the superheated susceptivity of steel, slightly overheated in the situation that, just there is alligatoring in crystal grain, increases temper brittleness simultaneously.
The phosphorous mass percent of forging die cast steel substrate is≤0.01%.Phosphide in steel weakens the intensity of steel, increases the cold cracking trend of steel.
The mass percent of forging die cast steel substrate sulfur-bearing is≤0.01%.Because sulfide is at the end just set in the crystal grain circumferential location of steel at steel process of setting, significantly reduce the hot strength of steel, impel hot tearing to form.When sulphur content is high, steel organize medium sulphide content quantity many, the intensity of steel and plasticity are reduced simultaneously, increase cold cracking trend.
Forging die cast steel substrate is 0.3%-0.8% containing the mass percent of chromium.The through hardening performance of steel is improved, play solution strengthening effect, improve intensity and the hardness of steel under as-heat-treated condition.When mass percent is less than 2%, improve the plasticity of steel.But also increased the temper brittleness of steel simultaneously.
The nickeliferous mass percent of forging die cast steel substrate is 0.1%-0.8%.Improve the hardening capacity of steel, and the eutectoid point of steel is moved to left, under identical carbon content, can obtain more perlite, be conducive to the strengthening of steel; And in strengthening, make ferritic plasticity and toughness increase; Not only improve normal temperature plasticity and the toughness of steel, also can make tough brittle transition temperature decline; Nickel is not oxidizable, under oxidizing atmosphere.Along with the oxidized consumption of other elements, nickel is in the enrichment gradually of the surface of steel, and the higher rich nickel dam of formation chemical stability, the resistance of oxidation of raising steel.
Forging die cast steel substrate is 0.1%-0.5% containing the mass percent of molybdenum.Solid solution, in steel, can significantly improve the recrystallization temperature of steel, thereby can significantly improve the hot strength of steel, and significantly improves the hardening capacity of steel, is used in conjunction with Cr, Mn element etc., can reduce or suppress the temper brittleness of steel,
The mass percent of forging die cast steel substrate cupric is≤0.5%.Play solution strengthening effect; Improve the toughness of steel, reduce the tough brittle transition temperature of steel.Copper can reduce the fusing point of steel simultaneously, thereby improves the mobility of molten steel, is conducive to castings production.
Adopt normalizing to add the heat treatment mode of tempering, can further strengthen matrix hardness, improve mechanical performance index.
The cast steel substrate of preparing forging die technique for double-deck built-up welding obtained by the method for the present invention, its intensity meets hydropress forging die mould, plasticity and toughness are good, carbon equivalent is at 0.6-0.8, weldability can be better, welding strengthening layer and cast steel substrate are connected firmly, and strength of joint surpasses 1000MPa, during work, does not come off.Therefore meet preferably the performance requriements of forging die mould aspect hardness, intensity and toughness plasticity two simultaneously, there is again excellent welding performance simultaneously, improved matrix and overlay cladding bonding strength, extended the forging die life-span, reduced production costs, save simultaneously forging process, shorten the forging die manufacture cycle.
Embodiment
Below in conjunction with specific experiment, the present invention is done to further checking and explanation.
In order to verify effect of the present invention, applicant has carried out orthogonal experiment, during experiment, in body material formula of the present invention, choose tetra-kinds of concrete ratios of element of C, Mn, Cr, Ni that material property is played a major role, adopt orthogonal test to verify, its technique is that the technique of tempering makes cast steel substrate after normalizing, and wherein normalizing temperature is 980-1020 ℃; Tempering temperature is 550-600 ℃, detects the performance perameters such as intensity of the cast steel substrate obtaining, and then prepares forging die technique built-up welding one deck transition layer in the double-deck built-up welding described in cast steel substrate surface employing background technology, detects the strength of joint after built-up welding transition layer.Take passages part orthogonal experiment data as following table.
Table 1 yield strength
Table 2 tensile strength
By above-mentioned analysis of variance table, found out, factor Ni is not remarkable to the effect of sample yield strength, can think that Ni is the secondary cause that affects this cast steel intensity, and from the angle of saving, might as well adopt Ni content is 0.1% later.Factor collocation is preferably C1Mn1Cr1, and C is 0.35%, and Mn is 1.8%, and Cr is 0.8%.Consider in the influence factor of carbon equivalent, the height of carbon content is main, reduces carbon content and will greatly reduce carbon equivalent, thereby increase cast steel weldability energy, improve the strength of joint of matrix and strengthening layer, make that it does not come off in process of production, distortion etc.
Therefore the optimum content of final definite principal element per-cent is that C is that 0.2%, Mn is that 1.8%, Cr is that 0.8%, Ni is 0.1%, and its carbon equivalent is 0.7 left and right, and weldability can be better.On this basis, all the other element ratios are chosen according to intermediate value or maximum value, its concrete ratio is as follows: carbon element content 0.2%, silicon content 0.3%, manganese element content 1.8%, phosphorus element content 0.01%, element sulphur content 0.01%, chromium constituent content 0.8%, nickel element content 0.1%, molybdenum element content 0.3%, copper content 0.5%, surplus is iron; After normalizing, the technique of tempering obtains cast steel substrate, and wherein normalizing temperature is 1000 ℃; Tempering temperature is 580 ℃.Test the performance of this cast steel substrate, its mechanical performance index reaches σ
s(yield strength)=527MPa, σ
b(tensile strength)=775MPa, δ (unit elongation)=21%, ψ (shrinking percentage)=51%, the requirement of AKv=39J.And then after built-up welding transition layer, test and detect and microanalysis on this cast steel substrate, its weld layer constituent content transition is the most steady, fluctuation is minimum, matrix is combined with weld layer firmly, and test weld layer strength of joint is 1200MPa, therefore can meet the demands completely.
The sample of above-mentioned optimum proportion composition is manufactured to forging die for actual casting, through actual production, put into practice, this forging die has been produced 7166 of qualified forging at present on 4000T hot die forging press, cast steel substrate occurs without situations such as deformation fractures, welding strengthening layer is connected firmly, without coming off, meet service requirements.