CN104775081A - High-carbon non-tempered steel for breaking connecting rod and manufacturing method thereof - Google Patents
High-carbon non-tempered steel for breaking connecting rod and manufacturing method thereof Download PDFInfo
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Abstract
The invention discloses high-carbon non-tempered steel for breaking a connecting rod and a manufacturing method thereof. The high-carbon non-tempered steel comprises the following chemical elements in percentage by weight: 0.65%-0.85% of C, 0.15%-0.25% of Si, 0.50%-0.60% of Mn, 0.010%-0.045% of P, 0.060%-0.070% of S, 0.10%-0.20% of Cr, 0.55%-0.80% of Ni, 0.03%-0.04% of V, 010%-0.20% of W, 0.0120%-0.0160% of N, 0.0001%-0.0004% of Re and the balance of Fe and inevitable impurities. The manufacturing method comprises the following steps: electric furnace primary smelting; ladle refining and vacuum degassing; die casting or continuous casting; and steel bar rolling. The high-carbon non-tempered steel has relatively high strength and good breaking performance.
Description
Technical field
The present invention relates to a kind of steel, particularly relate to a kind of Micro Alloying steel.The invention still further relates to a kind of manufacture method of these Micro Alloying steel.
Background technology
Non-hardened and tempered steel is a kind of novel energy-conserving steel rolling (or forging) be integrated with combined with heat treatment, and this steel can save modifier treatment (i.e. quenching+high tempering).At present, automobile connecting bar generally adopts non-hardened and tempered steel, in the development of connecting rod non-hardened and tempered steel, adopts support cracking connecting rod non-hardened and tempered steel to be also a kind of new thinking of development.Along with the develop rapidly of automotive industry, domestic and international automobile manufacturing company constantly applies the novel technique improving the quality of products, reduce product cost, enhance productivity, to strengthen its competitive power in the international market.For this reason, in the connection rod of automobile engine manufacturing, the support of connecting rod complete processing of breaking just has fully demonstrated the development trend of production cost of enhancing productivity, reduce.The support that Fig. 1 shows connecting rod is broken the operation chart of complete processing.As shown in Figure 1, the break ultimate principle of complete processing of the support of connecting rod is: on the split surface of crank pin end pore 1, process v-depression 2 with a broaching tool, applies a power F strutted by disconnected for connecting rod support with the special support device that breaks to big end hole 1.Owing to forming stress concentration at v-depression place, thus connecting rod accurately ruptures along V-shaped groove, though its section is comparatively coarse substantially smooth.Connecting rod support is had no progeny, bonding surface no longer carries out any processing, the cross section characteristic that uneven fracture possesses can make connecting rod body and connecting rod cap reach best state of coincideing when assembling, and degree of locating is good, the modes such as tack bolt, steady brace, profile of tooth need not be adopted as conventional linkage to position, thus greatly reduce production cost.
Compare to traditional connecting rod manufacturing process, the support of the connecting rod complete processing tool that breaks has the following advantages:
1) manufacturing procedure is decreased, without the milling of bonding surface, grinding and broaching;
2) due to the special shape of bonding surface, make the location of lid more accurate, connecting rod precision in use can be ensured, and do not need tack bolt, eliminate nut assembly;
3) connecting rod blank big end hole is circular, compared to oval big end hole of the prior art, more saves metallic substance and die cost;
4) eliminate cut-out and bonding surface processing, save a large amount of cutters and grinding tool expense;
5) save operator's cost, reduce production line working cost, decrease equipment maintenance expense.
But the insufficient strength that the connecting rod shank obtained by the disconnected complete processing of support at present and big end hole are excessively located, easily occurs phenomenon of rupture, and ferrite content in the microtexture of connecting rod is too high, makes to support disconnected effect unsatisfactory.The material of support cracking connecting rod and microtexture thereof not only have impact on performance and the cutting ability of connecting rod product, also determine cleavable and the cross section quality of connecting rod, play conclusive effect to the disconnected complete processing of support.The disconnected complete processing of support requires that connecting rod forging big end hole in the disconnected process of support can not produce obvious viscous deformation, to meet the rear deviation from circular from requirement of follow-up big end hole processing, for this reason, except needs ensure connecting rod integrated performance index, also need the toughness index of limiting rod, its fracture is made to occur brittle rupture feature, to make it have good engagement.
Publication number is CN101883873A, publication date is on November 10th, 2010, name is called that the Chinese patent literature of " cracking connecting-rod steel " discloses a kind of cracking connecting-rod steel, and in this cracking connecting-rod steel, the mass percentage (wt.) of each chemical element is: C:0.25 ~ 0.5%, Si:0.01 ~ 2.0%, Mn:0.50 ~ 2.0%, P:0.015 ~ 0.080%, S:0.01 ~ 0.2%, V:0.02 ~ 0.20%, Cr:0.05 ~ 1.0%, Ti:0.01 ~ 0.10%, below N:0.01%.Because the carbon content in this cracking connecting-rod steel is low, in order to improve the disconnected property of support, need to add a certain amount of Ti, but the interpolation of Ti reduces the cutting ability of connecting rod, and the interpolation of Ti content is wayward.
Publication number is CN101892424A, publication date is on November 24th, 2010, the Chinese patent literature that name is called " in a kind of fractured connecting rod use carbon non-hardened and tempered steel " discloses a kind of non-hardened and tempered steel, the mass percentage (wt.%) of its each chemical element is: C:0.35 ~ 0.55%, Si:0.40 ~ 0.80%, Mn:0.80 ~ 1.50%, P:0.04 ~ 0.15%, S:0.03 ~ 0.10%, Cr:0.10 ~ 0.50%, V:0.05 ~ 0.25%, B:0.0005 ~ 0.006%, Ti:0.01 ~ 0.10%, Al:0.005 ~ 0.05%, N:0.005 ~ 0.020%, RE:0.005 ~ 0.04%, surplus is Fe and other inevitable impurity.Meanwhile, the content of C, P and B also must meet Fragility parameters relational expression: 0.60≤C (%)+3P (%)+50B (%)≤1.0.The carbon content of this non-hardened and tempered steel is relatively low.
Publication number is 102108472A, publication date is on June 29th, 2011, name is called that the Chinese patent literature of " high carbon microalloy round steel and production method thereof for motor car engine cracking connecting-rod " discloses a kind of steel for motor car engine cracking connecting-rod, the mass percentage (wt.%) of its each chemical element is: C:0.60 ~ 0.80%, Si:0.17 ~ 0.37%, Mn:0.30 ~ 0.90%, P:0.020 ~ 0.060%, S:0.050 ~ 0.080%, N:0.015 ~ 0.0300%, and micro alloying element V, Nb, one or more of Ti and B, surplus is Fe and inevitable impurity.Not containing Cr element in this steel.
Summary, support cracking connecting rod of the prior art also exists following defect: 1) tensile strength is low; 2) hot workability is bad; 3) cracking performance difference and quality dissatisfaction, relevant technical requirements cannot be reached.
Summary of the invention
The object of the present invention is to provide a kind of support cracking connecting rod high-carbon non-hardened and tempered steel, this non-hardened and tempered steel has higher intensity concurrently and good support is disconnected and cracking performance.In addition, support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention also has excellent fatigue property, processing characteristics, cutting ability and forgeability.
Support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is had no progeny through support, and fracture port is without obvious viscous deformation, and the support meeting connecting rod steel is broken requirement.
To achieve these goals, the present invention proposes a kind of support cracking connecting rod high-carbon non-hardened and tempered steel, its chemical element mass percentage content is:
C：0.65％-0.85％，
Si：0.15％-0.25％，
Mn：0.50％-0.60％，
P:0.010％-0.045％，
S：0.060％-0.070％，
Cr：0.10％-0.20％，
Ni：0.55％-0.80％，
V：0.03％-0.04％，
W：0.10％-0.20％，
N：0.0120％-0.0160％,，
Re：0.0001-0.0004％，
Surplus is Fe and other inevitable impurity.
The principle of design of each chemical element in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is:
C:C element is intensity for guaranteeing steel and the element being used for improving steel cracking performance.If carbon content is too low, the intensity of steel cannot be improved, if carbon content is too high, fatigue property and the machinability of steel can be reduced.For support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention, C content needs to control between 0.65-0.85wt.% scope.
Si:Si element plays the effect of reductor in steel.Because Si does not form carbide in steel, but be present in ferrite with the form of sosoloid, namely there is significant solution strengthening ferrite, to reach the effect reducing steel plasticity.In addition, Si can also promote the Grain Boundary Segregation of P, S element, makes crystal boundary suitably brittle.In order to reach this object, the lower limit set of Si content is 0.15wt.%.But, because too high Si content will worsen hot workability and the forging surface quality of steel, so need the upper limit of Si content to be set as 0.25wt.% again.
Mn:Mn element, except playing reductor, also has significant solution strengthening effect.In addition, Mn and S can form MnS and be mingled with, and plays notch effect to improve the cracking performance of steel when supportting disconnected.In order to fully improve the cracking performance of steel, Mn need be controlled at more than 0.50wt.%, but, Mn too high levels is then easy produces bainite in microtexture, thus cause the machinability of steel and the decline of cracking performance, thus, also need Mn to control be no more than 0.60wt.%.
P:P element easily forms microsegregation when solidification of molten steel, and when heat, segregation, at crystal boundary, makes the fragility of steel enlarge markedly subsequently, and it is the element of the cracking performance effectively improving steel.But, once P element is superfluous, so the hot workability of steel will reduce.Given this, the P content span of control in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is: 0.010wt.%≤P≤0.045wt.%.
S:S can form Sulfide inclusion, and this inclusion can play notched effect during cracking, to improve the cracking performance of steel.Meanwhile, inclusion is also the beneficial element improving machinability.But, once S content is superfluous, the hot workability of steel can be reduced.Based on technical scheme of the present invention, in order to give full play to the beneficial effect of S and the unfavorable factor avoiding it to bring, need S content to control as 0.06-0.070wt.%.
Cr:Cr is the forming element of middle strong carbide, and it can improve every over-all properties such as intensity, wear resistance of steel significantly.In addition, Cr can also reduce the activity of C, to prevent the decarburization in heating, rolling and heat treatment step.But the Cr of too high amount can worsen the machinability of steel, and alloy interpolation cost can be increased.Therefore, the Cr content in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention needs control to be 0.10-0.20wt.%.
Ni:Ni has the effect improving steel fatigue strength.But, once Ni too high levels will reduce the machinability after hot-work, therefore, the Ni content in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention should control between 0.55-0.80wt.% scope.
V:V is easily combined with C, N and forms VN, VC etc.The carbonitride of V has stronger precipitation strength effect, except improving soft mutually ferritic intensity further, beyond the swollen disconnected performance improving steel, also can improve the fatigue property of steel significantly.But excessive V not only can reduce the machinability of steel, also can increase the production cost of steel simultaneously.For this reason, need the mass percentage of the V in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention to control to be 0.03-0.04%.
W:W is the forming element of medium carbide.It has been generally acknowledged that W can form alloyed cementite, play the effect of crystal grain thinning.Due to W, other alloying element proportions are comparatively large relatively, particularly adopt during the pouring type of die casting process and often cause ingotism, so the content of W in the inventive solutions should be not too high.Thus, the addition of the W in non-hardened and tempered steel of the present invention is set as: 0.10wt.%-0.20wt.%, to improve forgeability (red heat and heat resistance) and the grain fineness number of steel simultaneously.
N:N is easy to combine with Al, V etc. and form AlN, VN, and it can suppress growing up of steel austenite crystal at high temperature, thus improves the fatigue property of steel., when N content is more than 0.016wt.%, especially in steel-making step, easily produce the metallurgical imperfections such as bubble, N content too high being also unfavorable for produces in batches simultaneously.Given this, the N content in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention should be designed to 0.0120-0.0160wt.%.
Re: Re is added in steel can play refining, desulfurization, in and the effect of low melting point detrimental impurity.In addition, add the processing characteristics that Re element can also improve steel, and then improve the mechanical property of steel.For this reason, the Re content in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is 0.0001wt.%-0.0004wt.%.
Further, Cu≤0.20% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
Cu:Cu can improve intensity and the toughness of material., the Cu of too high levels can produce hot-short when high temperature, thus reduces the fatigue property of material, so the Cu in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention should control as≤0.20wt.%.
Further, Mo≤0.03% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
Mo:Mo is conducive to the toughness improving material, but Mo also can reduce the cracking performance of material in the technical program.For this reason, needing the Mo content in steel to control is≤0.03wt.%.
Further, Al≤0.010% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
Al: although aluminium is reductor conventional in steel, but the too high meeting of Al forms oxide inclusion in steel in the technical program, not only can reduce the fatigue property of material, also can reduce hot workability and the cutting ability of material.Given this, the Al content in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention should control as≤0.010wt.%.
Further, Ti≤0.003% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
Ti: in general, Ti contributes to crystal grain thinning, but for the technical program, it is easily combined with N and forms hard and thick TiN, and then can reduce the fatigue strength of material.Especially when Ti content is greater than 0.003wt.%, the fatigue strength of material can significantly decline, so Ti content needs to control at below 0.003wt.%.
Further, B≤0.0003% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
B: the B of trace can improve the intensity of steel., when carbon content is higher, the effect that B improves the intensity of steel weakens gradually, and too high B absorbs the effect that more N reduces N element formation second phase particles crystal grain thinning, make the intensity of steel produce fluctuation simultaneously, improve product plasticity, be unfavorable for that support is disconnected.Based on this, the B content needs≤0.0003wt.% in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
Further, [H]≤0.00015% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
H: in the inventive solutions, once H content has exceeded 0.00015wt.% will produce white-spot defects, so need the H in non-hardened and tempered steel of the present invention to control at below 0.00015wt.%.
Further, [O]≤0.0020% in the inevitable impurity of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention.
O:O is easily combined with Al and forms the oxide-based inclusion of hard, and it can reduce fatigue strength.Especially, when the content of O is greater than 0.0020wt.%, the fatigue strength of steel also can significantly decline.Given this, need O content to be set in below 0.0020wt.%.
Certainly, above-mentioned inevitable impurity should be control more low better, but these impurity can not be eliminated to the greatest extent completely, and inevitable Control of Impurities must be lower, and manufacturing cost is higher.For this reason, the economy of technique effect and the production cost obtained in conjunction with the present invention is needed to carry out the span of control of the above-mentioned impurity of comprehensive consideration.
Technical scheme of the present invention is designed by reasonable component, adds alloying element Mn, Cr, Ni and micro-V, W, Re etc., to improve the tensile strength of steel, and by controlling a certain amount of Si element, adds micro-Re to improve processing characteristics simultaneously.Add the carbonitride that micro-V forms favourable V, the precipitation strength effect utilizing it stronger by elements such as control C, Mn, P, S, refinement crystal grain, the performance thus the support improving steel is broken.
Further, the microtexture matrix of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is perlite+ferrite.
Further, described perlite is sheet perlite, and described ferrite is interrupted ferrite network.
Add micro-V and the elements such as control C, Mn, P, S, to form the carbonitride of favourable V, the carbonitride of V can play the effect of precipitation strength, and can crystal grain thinning, improve soft mutually ferritic intensity further, the performance thus the support improving steel is broken.In addition, control effectively to ensure that the microtexture of steel is perlite+ferrite by mentioned component.
Further, in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention, above-mentioned ferritic Phase Proportion≤5.0%.Ferritic structure has good plasticity and toughness, and for the technical program, connecting rod requires when supportting disconnected viscous deformation occurs hardly, and section presents the cleavage surface of fragility, therefore requires ferritic content≤5.0%.
Further, the grain fineness number of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is 7.5-8.0 level.
Further, the microtexture of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is included in precipitate V (C, the N) particle (i.e. vanadium carbide nitride) of intrinsic silicon and grain boundaries Dispersed precipitate.
V element has higher solubleness, in the temperature range of austenitic area, be easily in solid solution condition, and in hot procedure afterwards, along with the reduction of temperature, it can be separated out with small and dispersed Second Phase Particle.V and N has very strong avidity, N joins in steel as a kind of micro alloying element of cheapness, makes the V being in solid solution state change the V separating out state into, can play crystal grain thinning, improve the effect of precipitation strength, to reach the strength level required by quenched and tempered steel of the prior art.When N content is less, precipitated phase is based on VC, and along with the increase of N content, changing VN gradually into is main precipitated phase, is mainly distributed in crystal boundary.When N content controls between 0.0120-0.0160wt.% scope, improve the Precipitation Temperature of V (C, N) in austenite and separate out motivating force, the particle of precipitation is mainly V (C, N) particle.It is more that particle separates out quantity, and particle size and spacing will be less, and distribution form also there occurs change.Be distributed in intrinsic silicon and crystal boundary to more tiny precipitate particle disperse, the relative austenite grain boundary of this tiny precipitation particles produces " pinning " effect, prevents growing up of austenite crystal.Because V (C, N) has higher solubleness in austenite, separate out in process of cooling, improving the strength level of steel by separating out precipitation strength, promoting the tensile strength level of steel especially significantly.
Further, above-mentioned microtexture also have precipitate AlN, VN and VC at least one of them.
Further, the tensile strength of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is 900-1050MPa, and unit elongation 10-20%, relative reduction in area is 20-30%, ballistic work≤16J.
Correspondingly, present invention also offers the manufacture method of above-mentioned support cracking connecting rod high-carbon non-hardened and tempered steel, this manufacture method comprises the steps:
(1) electric furnace just refines;
(2) ladle refining+vacuum outgas;
(3) die casting or continuous casting;
(4) rod iron rolling.
Just refine in step at electric furnace, furnace charge can adopt steel scrap, crop and the high duty pig iron that P and S content is low, and alloy material then can adopt ferrochrome, low-phosphorous ferromanganese, molybdenum-iron etc., and reductive agent can use ferrosilicon powder, carbon dust, aluminium powder etc.
In ladle refining+vacuum outgas step, in ladle refining furnace, carry out liquid steel refining, remove obnoxious flavour and inclusion in steel, ladle is taken a seat, thermometric, after analysis, adjust the pressure in ladle according to practical situation.
Further, in the manufacture method of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention, in above-mentioned rod iron milling step, first heat in walking beam furnace before the rolling, wherein preheating section temperature is lower than 800 DEG C, first heating zone temperature is 960-1060 DEG C, and the second heating zone temperature is 1150-1200 DEG C, and soaking zone temperature is 1150-1200 DEG C.
In above-mentioned procedure of processing, preheating section temperature is controlled lower than 800 DEG C, then controlling Heating temperature in the first heating zone is 960-1060 DEG C, the second heating zone is entered after insulation, then the Heating temperature of this section is set as 1150-1200 DEG C, enter soaking zone after insulation, soaking zone temperature controls as 1150-1200 DEG C, rolling of coming out of the stove after insulation.
Further, in the manufacture method of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention, carry out rod iron rolling after completing heating, wherein start rolling temperature is 1050-1120 DEG C, finishing temperature 850-950 DEG C.
Under above-mentioned start rolling temperature and finishing temperature, be conducive to N precipitation from γ sosoloid and out, and be combined into VN or V (C, N) with the V in steel.Due to the solubleness that the solubleness of N in α-Fe is less than in γ-Fe, and cause again two peak values of VN or V (C, N) amount of precipitation owing to being subject to exciting of phase transformation.Once finishing temperature is too low, the peak value of VN or V (C, N) is separated out, can cause VN or V (C, N) skewness, and recovery and recrystallization is insufficient and produce structural anisotropy, therefore, finishing temperature can not be too low, needs to control it as 850-950 DEG C.
Further, in the manufacture method of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention, in above-mentioned ladle refining+vacuum outgas step, controlling bull ladle temperature is 1550-1570 DEG C.
Further, in the manufacture method of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention, above-mentioned electric furnace just refines in step, and control tapping temperature is 1630-1650 DEG C.
As can be seen here, the feature of the manufacture method of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is low temperature casting, heat, high temperature rolling and high-temperature final rolling, can obtain microtexture by this technique is perlite+ferritic support cracking connecting rod high-carbon non-hardened and tempered steel, wherein, ferritic Phase Proportion may be controlled to≤5.0%.
In addition, the manufacture method of the support cracking connecting rod high-carbon non-hardened and tempered steel described in steel of the present invention adopts processing methodes such as controlling low temperature casting, heat, high temperature rolling and high-temperature final rolling, control second phase particles VN, VC, V (C, N) precipitation opportunity and precipitation quantity, thus refinement austenite crystal, make autstenitic grain size to reach 7.5-8.0 level.
For this reason, technical scheme of the present invention, by the microtexture in control steel and autstenitic grain size, makes the microstructure and chemical composition in steel more even, the performance thus the support improving support cracking connecting rod high-carbon non-hardened and tempered steel is broken.
Support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention has higher intensity and its tensile strength Rm:900-1050MPa of good unit elongation, unit elongation A:10-20%.
Support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention has good toughness and cracking performance, its ballistic work KU
2:≤16J, relative reduction in area Z:20-30%.
Support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention possesses good fatigue property, cutting ability and forgeability.
In addition, the microtexture of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is even, and it possesses excellent support and to break performance.
In addition, the alloying element in support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is simple, and economical, reduces manufacturing cost significantly.
Support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is had no progeny through support, and fracture port is without obvious viscous deformation, and the support meeting connecting rod steel is broken requirement.
The manufacture method of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention can obtain that intensity is high, excellent property is broken in good toughness, support and the high-carbon non-hardened and tempered steel that fatigue property, processing characteristics, cutting ability, forgeability and cracking performance are excellent.This high-carbon non-hardened and tempered steel is applicable to the support breaking process adopting connecting rod.
The manufacturing approach craft control temperature of support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention is reliable, and processing step cost is low.
Accompanying drawing explanation
Fig. 1 is that the support of connecting rod is broken the operation chart of complete processing.
Fig. 2 is the micro-organization chart that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 makes major part position after connecting rod.
Fig. 3 is the micro-organization chart that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 makes I-shaped muscle position after connecting rod.
Fig. 4 is the micro-organization chart that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 makes microcephaly position after connecting rod.
Fig. 5 is that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 is through supportting the SEM figure of the fracture crack expansion initiator of having no progeny.
Fig. 6 is that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 is through supportting the SEM figure of the fracture crack expansion area of having no progeny.
Fig. 7 is that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 is through supportting the SEM figure in the fracture eventual failure district of having no progeny.
Embodiment
Below in conjunction with specific embodiments support cracking connecting rod high-carbon non-hardened and tempered steel of the present invention and manufacture method thereof are made further explanation, but this explanation and explanation do not form improper restriction to technical scheme of the present invention.
The support cracking connecting rod high-carbon non-hardened and tempered steel in embodiment A 1-A8 and in comparative example B1 and B2 is manufactured according to following step:
(1) electric furnace just refines: in the electric arc furnace of 60-150 ton, carry out molten steel just refine, oxidation period duty stream slag remove P, tapping temperature is 1630-1660 DEG C, and tapping temperature is 1630-1650 DEG C;
(2) add alloy block after ladle refining+vacuum outgas: LF just deoxidation to stir 5 ~ 10 minutes, when molten steel thermometric T >=1580 DEG C, enter vacuum degassed, vacuum tightness≤66.7Pa, vacuum hold-time 15-20min, to ensure [H]≤0.00015wr.%, the proportioning controlling each chemical element is as shown in table 1, start bull ladle when all chemical elements enter after in limited range, bull ladle temperature is 1550-1570 DEG C;
(3) continuous casting: during continuous casting, in ladle, high-temperature molten steel, by protective casing, waters into tundish, control the superheating temperature 20-40 DEG C of tundish, the molten steel in tundish, through continuous cast mold, after adding induction stirring, waters with rational pulling rate and outpours 140 × 140mm
2~ 320 × 425mm
2the qualified continuously cast bloom of cross dimensions, according to different square billet sizes, controls pouring speed as 0.6-2.10m/min;
(4) rod iron rolling: first qualified billet surface is cleared up, first heat in walking beam furnace before the rolling, wherein preheating section temperature is lower than 800 DEG C, first heating zone temperature is 960-1060 DEG C, second heating zone temperature is 1150-1200 DEG C, soaking zone temperature is 1150-1200 DEG C, heating total time 150min, a square billet male and female face temperature difference≤30 DEG C steel billet is come out of the stove, steel billet dephosphorize by high pressure water descaling after coming out of the stove, carry out rod iron rolling, wherein start rolling temperature is 1050-1120 DEG C, finishing temperature 850-950 DEG C.
Concrete technology parameter in each step involved by above-mentioned manufacture method is in detail see table 2.
It should be noted that, in above-mentioned continuous casting step, tundish needs to clear up completely before using, and tundish internal surface is fire-resistant coating and must not has crack.In addition, if step (3) adopts die casting, then when die casting teeming, pouring speed is controlled to prevent the component segregation of steel ingot.
Table 1 lists the mass percentage content of each chemical element making embodiment A 1-A8 and comparative example B1-B2.
Table 1. (wt.%, surplus is Fe and other inevitable impurity)
| Sequence number | A1 | A2 | A3 | A4 | A5 | A6 | A7 | A8 | B1 | B2 |
| C | 0.65 | 0.84 | 0.67 | 0.66 | 0.71 | 0.69 | 0.67 | 0.8 | 0.38 | 0.45 |
| Si | 0.18 | 0.2 | 0.22 | 0.24 | 0.15 | 0.2 | 0.19 | 0.16 | 0.7 | 0.35 |
| Mn | 0.6 | 0.58 | 0.56 | 0.57 | 0.54 | 0.52 | 0.58 | 0.51 | 1.49 | 0.73 |
| P | 0.03 | 0.014 | 0.044 | 0.032 | 0.022 | 0.011 | 0.02 | 0.012 | 0.008 | 0.009 |
| S | 0.066 | 0.062 | 0.061 | 0.064 | 0.07 | 0.061 | 0.069 | 0.068 | 0.023 | 0.048 |
| Cr | 0.15 | 0.12 | 0.19 | 0.11 | 0.16 | 0.17 | 0.15 | 0.14 | 0.15 | 0.14 |
| Ni | 0.58 | 0.55 | 0.59 | 0.69 | 0.55 | 0.64 | 0.73 | 0.78 | 0.01 | 0.18 |
| V | 0.034 | 0.031 | 0.032 | 0.03 | 0.033 | 0.04 | 0.037 | 0.031 | 0.12 | 0.099 |
| W | 0.1 | 0.14 | 0.11 | 0.13 | 0.17 | 0.19 | 0.12 | 0.14 | 0.001 | 0.001 |
| N | 0.013 | 0.016 | 0.013 | 0.014 | 0.015 | 0.015 | 0.012 | 0.013 | 0.02 | 0.0111 |
| Re | 0.0001 | 0.0001 | 0.0002 | 0.0001 | 0.0003 | 0.0001 | 0.0004 | 0.0001 | 0 | 0 |
| Cu | 0.11 | 0.18 | 0.11 | 0.13 | 0.14 | 0.08 | 0.15 | 0.1 | 0.03 | 0.09 |
| Mo | 0.01 | 0.02 | 0.01 | 0.01 | 0.03 | 0.01 | 0.01 | 0.01 | 0.01 | 0.01 |
| Al | 0.008 | 0.006 | 0.007 | 0.008 | 0.01 | 0.006 | 0.01 | 0.009 | 0.016 | 0.01 |
| Ti | 0.0011 | 0.0018 | 0.001 | 0.0028 | 0.001 | 0.001 | 0.0022 | 0.0014 | 0.022 | 0.014 |
| B | 0.00022 | 0.00015 | 0.00018 | 0.00016 | 0.00029 | 0.0001 | 0.00013 | 0.00018 | 0.0001 | 0.0002 |
| H | 0.0001 | 0.0001 | 0.00015 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | 0.0001 | 0.0001 |
| O | 0.0018 | 0.0012 | 0.0017 | 0.0016 | 0.0018 | 0.0009 | 0.0011 | 0.001 | 0.0011 | 0.0017 |
Table 2 lists the processing parameter of the manufacture method of embodiment A 1-A8 and comparative example B1-B2.
Table 2.
Table 3 lists every mechanical property parameters and the microtexture situation of embodiment A 1-A8 and comparative example B1-B2.
Table 3.
| Sequence number | Rm/MPa | A/％ | Z/％ | KU 2/J | Ferritic phase ratio/% | Grain fineness number/level |
| A1 | 984 | 11 | 26 | 16 | 2.2 | 7.5 |
| A2 | 988 | 13 | 28 | 15 | 2.4 | 7.5 |
| A3 | 992 | 17 | 26 | 11 | 2.1 | 8.0 |
| A4 | 1030 | 12 | 27 | 16 | 2.3 | 7.5 |
| A5 | 920 | 10 | 22 | 14 | 2.1 | 8.0 |
| A6 | 1048 | 16 | 21 | 14 | 1.7 | 7.5 |
| A7 | 905 | 14 | 29 | 13 | 1.9 | 8.0 |
| A8 | 946 | 11 | 20 | 11 | 2.0 | 7.5 |
| B1 | 867 | 17 | 35 | 68 | 36 | 7.0 |
| B2 | 826 | 18 | 34 | 51 | 35 | 6.5 |
As can be seen from Table 3, compare to comparative example B1-B2, the grain fineness number of embodiment A 1-A8 is thinner, and its ferritic phase ratio is less, and all≤2.4%, its grain fineness number is not all coarser than 7.5 grades to the ferritic phase ratio of embodiment A 1-A8.Tensile strength Rm>=the 905MPa of embodiment A 1-A8, unit elongation A are within the scope of 10-17%, and relative reduction in area Z is 20-29%, ballistic work KU
2between 11-16J scope, thus, illustrate that the support cracking connecting rod high-carbon non-hardened and tempered steel in embodiment possesses higher intensity, good processing characteristics, excellent fatigue property and the support of excellence are broken performance.Review comparative example B1-B2, its tensile strength Rm is less than 900MPa, and relative reduction in area Z is all more than 30%, and ballistic work KU
2all exceeded 50J, good toughness is unfavorable for that support is disconnected.
The support cracking connecting rod high-carbon non-hardened and tempered steel that Fig. 2 shows embodiment A 1 makes the microtexture at major part position after connecting rod.The support cracking connecting rod high-carbon non-hardened and tempered steel that Fig. 3 shows embodiment A 1 makes the microtexture at I-shaped muscle position after connecting rod.The support cracking connecting rod high-carbon non-hardened and tempered steel that Fig. 4 shows embodiment A 1 makes the microtexture at microcephaly position after connecting rod.
As can be seen from Figure 2, the microtexture in the big end position of embodiment A 1 comprises lamella perlite and interrupted ferrite network matrix.Wherein, interrupted ferrite network is that proeutectoid ferrite formed in original austenite crystal prevention precipitation.In addition, this microtexture is also included in precipitate V (C, the N) particle of intrinsic silicon and grain boundaries Dispersed precipitate.
As can be seen from Figure 3, the microtexture matrix at the connecting rod I-shaped muscle position of embodiment A 1 is made up of lamella perlite and interrupted ferrite network.Wherein, ferrite network is that proeutectoid ferrite formed in original austenite crystal prevention precipitation.In addition, this microtexture is included in precipitate V (C, the N) particle of intrinsic silicon and grain boundaries Dispersed precipitate.
As Fig. 4 can find out, the microtexture matrix at the small end of connecting rod position of embodiment A 1 is made up of lamella perlite and interrupted ferrite network.Wherein, ferrite network is that proeutectoid ferrite formed in original austenite crystal prevention precipitation.In addition, this microtexture is included in precipitate V (C, the N) particle of intrinsic silicon and grain boundaries Dispersed precipitate.
Support cracking connecting rod high-carbon non-hardened and tempered steel in embodiment A 1-A8 and comparative example B1-B2 is carried out support to break.
Fig. 5 is that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 is through supportting the SEM figure of the fracture crack expansion initiator of having no progeny.Fig. 6 is that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 is through supportting the SEM figure of the fracture crack expansion area of having no progeny.Fig. 7 is that the support cracking connecting rod high-carbon non-hardened and tempered steel of embodiment A 1 is through supportting the SEM figure in the fracture eventual failure district of having no progeny.
As shown in Fig. 5, Fig. 6 and Fig. 7, no matter steel of the present invention is in fracture crack expansion initiator, or in fracture crack expansion area, also or in fracture eventual failure district, through supportting on the fracture of having no progeny all without obvious viscous deformation, microfractograph mainly exists with cleavage, is macroscopically showing as brittle rupture feature, and the support meeting connecting rod steel is like this broken requirement.
It should be noted that above enumerate be only specific embodiments of the invention, obviously the invention is not restricted to above embodiment, have many similar changes thereupon.If all distortion that those skilled in the art directly derives from content disclosed by the invention or associates, protection scope of the present invention all should be belonged to.
Claims (20)
1. support a cracking connecting rod high-carbon non-hardened and tempered steel, it is characterized in that, its chemical element mass percentage content is:
C:0.65%-0.85%, Si:0.15%-0.25%, Mn:0.50%-0.60%, P:0.010%-0.045%, S:0.060%-0.070%, Cr:0.10%-0.20%, Ni:0.55%-0.80%, V:0.03%-0.04%, W:0.10%-0.20%, N:0.0120%-0.0160%, Re:0.0001-0.0004%; Surplus is Fe and inevitable impurity.
2. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, Cu≤0.20% in described inevitable impurity.
3. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, Mo≤0.03% in described inevitable impurity.
4. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, Al≤0.010% in described inevitable impurity.
5. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, Ti≤0.003% in described inevitable impurity.
6. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, B≤0.0003% in described inevitable impurity.
7. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, [H]≤0.00015% in described inevitable impurity.
8. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, is characterized in that, [O]≤0.0020% in described inevitable impurity.
9. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, it is characterized in that, its microtexture matrix is perlite+ferrite.
10. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 9, it is characterized in that, described perlite is sheet perlite, and described ferrite is interrupted ferrite network.
11. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 9, is characterized in that, ferritic Phase Proportion≤5.0%.
12. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, it is characterized in that, its grain fineness number is 7.5-8.0 level.
13. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 9, and it is characterized in that, its microtexture is included in precipitate V (C, the N) particle of intrinsic silicon and grain boundaries Dispersed precipitate.
14. as claimed in claim 9 support cracking connecting rod high-carbon non-hardened and tempered steels, is characterized in that, its microtexture also comprise precipitate AlN, VN and VC at least one of them.
15. support cracking connecting rod high-carbon non-hardened and tempered steel as claimed in claim 1, and it is characterized in that, its tensile strength is 900-1050MPa, unit elongation 10-20%, and relative reduction in area is 20-30%, ballistic work≤16J.
16. 1 kinds as the manufacture method of high-carbon non-hardened and tempered steel of the support cracking connecting rod in claim 1-15 as described in any one, it comprises step: electric furnace just refines → ladle refining+vacuum outgas → die casting or continuous casting → rod iron rolling.
The 17. support cracking connecting rods as claimed in claim 16 manufacture method of high-carbon non-hardened and tempered steel, it is characterized in that, in described rod iron milling step, first heat in walking beam furnace before the rolling, wherein preheating section temperature is lower than 800 DEG C, first heating zone temperature is 960-1060 DEG C, and the second heating zone temperature is 1150-1200 DEG C, and soaking zone temperature is 1150-1200 DEG C.
18. support the cracking connecting rod manufacture method of high-carbon non-hardened and tempered steel as claimed in claim 17, and it is characterized in that, carry out rod iron rolling after completing heating, wherein start rolling temperature is 1050-1120 DEG C, finishing temperature 850-950 DEG C.
19. support the cracking connecting rod manufacture method of high-carbon non-hardened and tempered steel as claimed in claim 16, it is characterized in that, in described ladle refining+vacuum outgas step, controlling bull ladle temperature is 1550-1570 DEG C.
20. support the cracking connecting rod manufacture method of high-carbon non-hardened and tempered steel as claimed in claim 16, and it is characterized in that, just refine in step at described electric furnace, control tapping temperature is 1630-1650 DEG C.
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