CN105886717A - Normalizing method for forging waste heat of steel - Google Patents

Normalizing method for forging waste heat of steel Download PDF

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CN105886717A
CN105886717A CN201610282007.6A CN201610282007A CN105886717A CN 105886717 A CN105886717 A CN 105886717A CN 201610282007 A CN201610282007 A CN 201610282007A CN 105886717 A CN105886717 A CN 105886717A
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steel
temperature
forging
cooling
normalizing
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CN105886717B (en
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王中忞
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C21D1/28—Normalising
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/84—Controlled slow cooling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The invention discloses a normalizing method for forging waste heat of steel. The normalizing method is characterized in that online controlled forging and cooling isothermal normalizing treatment for forging waste heat is implemented. The normalizing method comprises the following steps of controlled forging of the steel: controlling the forging temperature and the forging deformation degree of the steel, and refining grains by deforming and recrystallizing austenite; controlled cooling of the steel: controlling cooling rates, cooling uniformity and cooling efficiency of the steel at of all critical temperatures according to the principles of metallography and heat treatment; cooling the steel to a critical temperature and keeping the isothermality; finishing transformation of super-cooled austenite within the temperature range, thus obtaining fine grain structures; and after isothermal keeping, performing controlled cooling, namely controlling the cooling rate, the cooling uniformity, the cooling efficiency and a cooling final temperature after isothermal keeping, thus obtaining the normalizing method with structure and mechanical properties up to standards. According to the normalizing method disclosed by the invention, energy sources and resources can be saved, the normalizing treatment quality is improved, the normalizing treatment cost is reduced, the labor intensity of workers is reduced, labor productivity is improved, and the construction period is shortened.

Description

A kind of residual forging heat normalizing method of steel
Technical field
The present invention relates to a kind of Heat-Treatment of Steel method, particularly relate to the residual forging heat control forging control of a kind of steel cold etc. Temperature normalizing method.
Background technology
The isothermal normalizing of conventional steel processes consume energy big, quality instability, the mixed crystal that occurs now and then, cost height, work People's labour intensity is heavy, long in time limit；By energy-saving and emission-reduction, the requirement of green low-carbon, the repeatedly utilization to used heat, The particularly repeatedly utilization to residual forging heat；Due to residual forging heat normalized treatment, quality and technical index is difficult to reach Mark, and this problem can use technical scheme to solve.
Summary of the invention
In order to solve above-mentioned technical problem, the present invention is achieved by the following technical solutions:
It is an object of the invention to provide a kind of forging press and be followed by the normalized treatment production line of waste heat steel, be implemented in Line residual forging heat control forging is controlled cold isothermal normalizing and is processed, and instant invention overcomes deficiency of the prior art, the method Utilizing the residual forging heat of steel, heat need not reheat acquisition, eliminates reheating operation, saves the energy And resource, raising normalized treatment quality:
(1), after solving the residual forging heat normalizing of steel, quality and technical index is difficult to a difficult problem up to standard；
(2) the cold distortional stress of control of the present invention forging control promotes Ms point to rise, and improves the quenching degree of steel, with this Invent the conditioning treatment as quenching, have the advantage that
(1) use the process for quenching of reduction cooling velocity, be useful to preventing hardening flaw and minimizing amount of distortion 's；
(2) quenching temperature uses lower limit temperature, organizes after refinement quenching, prevents hardening flaw and subtract Few amount of distortion is useful, and saves the energy, extends the service life being heat-treated facility；
(3) austempering need not improve quenching temperature, organizes after refinement quenching, prevents Hardening flaw and minimizing amount of distortion are useful, and save the energy, extend the service life being heat-treated facility.
Traditional isothermal normalizing of steel is that steel heats austenitizing, and after samming, steel quickly cools down and passes through normalizing temperature To the critical-temperature of steel, carrying out having the isothermal of energy supplement to keep in entering heating furnace, overcooling austenite is at this Temperature range changes complete, obtains thinner grain structure, then air cooling, it is thus achieved that preferably machinability Can be with the normalizing method of mechanical property；
The present invention is the normalized treatment production line that forging press is followed by waste heat steel, implements online residual forging heat control forging control Cold isothermal normalizing processes, and the residual forging heat of steel i.e. utilizes the residual forging heat of steel, the control forging of steel, i.e. controls steel Forging temperature and forging deformation degree, cause crystal grain thinning by austenite deformation and recrystallization, the control of steel is cold, According to metallography and Principles of Heating Processing, control the cooldown rate of each critical-temperature of steel, cooling uniformity and cold But efficiency, steel is cooled to normalizing temperature, quickly the cooling critical-temperature by normalizing temperature to steel, enters slow Ice chest carries out the isothermal holding that noenergy is supplemented, and overcooling austenite changes complete in this temperature range, obtains thin Grain structure, isothermal controls cooldown rate, cooling uniformity and cooling effectiveness and cooling and terminates temperature after keeping Degree, it is thus achieved that the normalizing method that microstructure and mechanical property is up to standard.
As a example by the present invention is achieved in that with medium carbon structure steel (containing middle carbon and low-alloy non-hardened and tempered steel, lower same), It is characterized in that method is:
1. the residual forging heat of steel, it is the residual forging heat utilizing steel, and heat need not reheat acquisition, saves Reheat operation.
2. the control forging of steel is forging temperature and the forging deformation degree controlling steel；
(1) forging temperature of control steel:
(1) Forge Heating temperature TA of steel is determined by usual Forge Heating temperature and the initial forging temperature of steel；
Deformation temperature due to steel is higher than the recrystallization temperature of deformed austenite, and Forge Heating temperature should slow down Austria The process that family name's body is grown up because of dynamic and Static Recrystallization crystal grain, AUSTENITE GRAIN COARSENING during to reduce heating, because of This, on the premise of ensureing forging and molding, Forge Heating temperature TA of steel presses the usual Forge Heating temperature of steel Determine with initial forging temperature；
Forge Heating temperature TA of steel is calculated as follows:
TA=(TSD+20)℃
T in formulaSDThe usual initial forging temperature of steel；
(2) SB is that the forging of steel is forged in austenite recrystallization temperature scope, and steel is in thermal deformation process, logical Cross deformation and cause Austenite Grain Refinement with recrystallization；
(3) the initial forging temperature S of steel presses the usual initial forging temperature of steel and determines；
Deformation temperature due to steel is higher than the recrystallization temperature of deformed austenite, and initial forging temperature should slow down austenite Because of dynamically and the process grown up of Static Recrystallization crystal grain, make initial forging temperature reduction AUSTENITE GRAIN COARSENING, therefore, On the premise of ensureing forging and molding, initial forging temperature S presses the usual initial forging temperature of steel and determines；
(4) final forging temperature of steel is determined as higher than the austenitizing temperature of steel；
Final forging temperature T of B point temperature steelZDRepresent with following formula:
TZD≥(TA+40)℃
T in formulaAThe austenitizing temperature of steel；
B point temperature is TZD≥(TA+ 40) DEG C, this is owing to B point is final forging temperature, is also to deform after forging Austenite carries out the starting point of recrystallization, and B point temperature is more than minimum deformed austenite recrystallization temperature T95, At least there is the recrystallization of 95% in this temperature, make the abundant recrystallization of austenite, be conducive to being refined, all Even, etc. the austenite crystal of axle；
(2) the forging deformation degree of control steel:
The forging deformation degree of steel be obtained uniformly by austenite deformation and recrystallization, refinement, etc. the Ovshinsky of axle Body crystal grain, it is to avoid critical degree of deformation and big degree of deformation, prevents grain coarsening.
Every time employing 25～40% of the forging deformation degree of steel:
When steel forging deformation degree every time be 25%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps normalizing After, forging metallographic structure reaches first group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
When steel forging deformation degree every time be 40%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps normalizing After, forging metallographic structure reaches first group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
When steel forging deformation degree every time be 30%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps normalizing After, forging metallographic structure reaches first group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
Obtained uniformly by austenite deformation and recrystallization, refinement, etc. the austenite crystal of axle, it is to avoid critical Degree of deformation and the large deformation degree more than 70%, prevent grain coarsening；This be due to:
(1) degree of deformation is less than 20%, there is the small Recovery and recrystallization stage, rapidly enters crystal grain and grows up rank Section；
(2) degree of deformation is little, and during Forge Heating, austenite crystal is roughened, and the degree of deformation less than 20% causes office Portion deforms, and recrystal grain thickness is uneven；
(3) during more than 70% degree of deformation, interior friction makes forging temperature increase, and promotes recrystallization brilliant Grain length is big；
(4) during more than 90% degree of deformation, it is too high that interior friction makes forging temperature increase, and causes secondary Recrystallization, causes crystal grain abnormal thick.
3. the cold cooldown rate of each critical-temperature, cooling uniformity and the cooling effectiveness for controlling steel of the control of steel；
(1) steel is cooled to the normalizing temperature of steel from final forging temperature；
(1) steel is from B point temperature TZD≥(TA+ 40) the normalizing temperature of C point temperature steel DEG C it is cooled to Degree, Y point is for movement, and BY is Slow cooling, YC is comparatively fast to cool down, this be due to:
1) make the abundant recrystallization of deformed austenite of steel, refined, uniformly, etc. the austenite crystal of axle, Grain size distribution is the narrowest more is conducive to suppressing grain coarsening, in order to avoid there is mixed crystal；
2) cooling velocity of steel is caused by the energy difference on steel surface with cooling medium, the cooling velocity that energy difference is big Greatly, otherwise, cooling velocity is little, so, in same cooling medium, the cooling velocity that the temperature of steel is high is big In the cooling velocity that temperature is low, through the cooling of BC, wherein BY is Slow cooling, and YC is very fast cooling, Forging is the normalizing temperature of steel to C point temperature；
(2) C point temperature is steelThis is due to the usual normalizing temperature than sub-eutectoid steel DegreeHigh (20～50) DEG C, eliminate the high temperature normalizing temperature of forging Widmannstatten structure than sub-eutectoid steelLow 50 DEG C, high temperature normalizing can eliminate forging Widmannstatten structure, reduces banded structure and makes Calendering longitudinal direction and the horizontal mechanical performance difference become, normalizing temperature usesAnd subsequently Very fast cooling and Ar1The quick cooling of temperature, causes stress big, and hardness is high, for obtaining suitable machining Performance, eliminates forging Widmannstatten structure simultaneously；
(3) BC B cool time1C1It is not more than 60 seconds, i.e. Y1Point moves with Y point and moves, and BY delays Slow cool down time B1Y1Cool time very fast with YC Y1C1And no more than 60 seconds, steel forging after stop time Between long meeting cause growing up of austenite crystal, this be due to steel forge after the first stage for reply, second stage For recrystallization, the phase III is that crystal grain is grown up；
Phase III crystal grain time y following formula of growing up is expressed:
Y=x-(τ1+τ2)
The time of staying after X forging in formula,
τ1Turnaround time first stage,
τ2The second stage recrystallization time；
1) as X-(τ1+τ2During)=0, the recrystallization stage just terminates, and obtain is distortionless etc. Axle recrystallization initial grain；
2) as X-(τ1+τ2) ＜ 0 time, recrystallization is insufficient, it is impossible to refined, uniformly, etc. axle Crystal grain；
3) as X-(τ1+τ2) ＞ 0 time, work as τ1+τ2For definite value, when variable X value is big, then y Value is also big, so phase III crystal grain is grown up, the time is long, causes grain coarsening；
(2) normalizing temperature by steel is quickly cooled down；
(1) CD is very fast cooling, from steelComparatively fast it is cooled to Ar1Temperature, this is Due to slow in normalizing temperature cooling velocity after forging, cause grain coarsening；
D point temperature is the Ar of steel1+ (30～40) DEG C；
(2) DE is Slow cooling, and this is that its cooling velocity is more than Slow cooling speed owing to CD is very fast cooling Degree, causes forging temperature field deviation, and heart portion temperature is higher than surface temperature, according to be high-energy inside the matters to The Changing Pattern of low-energy state transfer, by heat transfer, forging temperature field is in sub-poised state, now Slow cooling plays the effect of uniform temperature and cooling:
1) uniformity, cooldown rate and cooling effectiveness that next step EF quickly cools down are improved；
2) stoping next step EF quickly to cool down causes forging surface that bainite transformation occurs, suitable to obtain Machinability；
E point temperature is the Ar of steel1+ (20～30) DEG C；
(3) EF is quickly cooling, this be due to:
1) universal law of tissue effect after steel normalizing is by cooling velocity: cooling velocity is big, austenite decomposition Temperature is low, and perlitic transformation product is tiny, for making the residual forging heat control cold normalizing metallographic structure of steel reach First group of judge picture of GB/T13320-2007 1～4 grades of qualified requirements；
2) it is the Ar quickly through steel1Temperature, prevents from occurring thick tissue on pro-eutectoid ferrite crystal boundary；
F point temperature is the Ar of steel1(0～10) DEG C；
(4) FG is Slow cooling, and this is that its cooling velocity is more than comparatively fast cooling down speed owing to EF is quickly cooling Degree, causes the deviation that forging temperature field is big, and heart portion temperature is higher than surface temperature, according to being high energy inside the matters Measuring the Changing Pattern to low-energy state transfer, by heat transfer, forging temperature field is in sub-poised state, The now effect of Slow cooling:
1) effect of uniform temperature is played；
I () improves uniformity, cooldown rate and the cooling effectiveness that next step GH comparatively fast cools down；
(ii) stoping next step GH comparatively fast to cool down causes forging surface that bainite transformation occurs, suitable to obtain Machinability；
2) cooling after uniform temperature and the common effect of Slow cooling, quickly through the Ar of steel1Temperature；
G point temperature is the Ar of steel1(10～20) DEG C；
(5) GH is very fast cooling, and H point temperature is the Ar of steel1(20～30) DEG C, this point for quickly through The Ar of steel1Temperature terminates；
(6) HJ is Slow cooling, and this is owing to Slow cooling plays the effect of uniform temperature and cooling, with accurately Temperature enters the isothermal holding that noenergy is supplemented；
J point be forging enter slow cooling box carry out noenergy supplement isothermal keep beginning, for from entering slow cooling box J point Temperature keeps at least 20 minutes to nose " upper C-curve " temperature isothermal, makes Cooling Austenite Transformation become pearlite, Nose " lower C-curve " temperature will not be entered in 20 minutes by isothermal temperature, stop and bainite transformation occurs, obtain Suitable machinability:
1) J point temperature is C-curve nose portion temperature T of steelP+ (40～90) DEG C, and meet the Ar of steel1- (30～80) DEG C, offset cooling and isothermal holding in slow cooling box that steel part has a small amount of heat to scatter and disappear in slow cooling box Temperature slowly successively decrease；
2) slow cooling box good heat insulating；
3) forging is automatically switched off slow cooling box entrance after entering slow cooling box immediately, lost from porch to reduce heat, Preserve waste heat and carry out isothermal holding, after pouring out hot water just as vacuum flask, immediately plug for vacuum bottle is covered bottleneck, Lost from bottle mouth position to reduce heat.
4. the isothermal normalizing of steel be steel critical-temperature isothermal keep carry out normalized treatment；
Steel quickly cools down the critical-temperature C-curve nose temperature by normalizing temperature to steel, at the C-of steel Curve nose temperature isothermal keeps carrying out normalized treatment；
(1) JK be isothermal keep, this be due to:
(1) overcooling austenite of steel changes complete in this temperature range, it is thus achieved that thin pearlitic structrure；
(2) universal law of performance impact after steel normalizing is by cooling velocity: cooling velocity is big, and stress is big, Hardness is high, and after cold isothermal normalizing is controlled in the residual forging heat control forging of steel, metallographic structure reaches GB/T13320-2007 the One group of judge picture 1～4 grades of qualified requirements, for eliminating the Ar at steel1Temperature quickly cool down the stress that causes big, Hardness is high, thus obtains suitable machinability；
(3) Ar of steel1Temperature is provided without quickly cooling down, and uses very fast cooling, the most not at the C-curve of steel Nose temperature isothermal keeps, and after normalized treatment, metallographic structure is thick, comments for GB/T13320-2007 first group 7 grades of level figure；
(4) it is balanced tissue, forges through the residual forging heat control of steel and control cold isothermal normalizing and process the balance group that obtains Knitting, the coarse grain non-equilibrium microstructure of elimination steel, when usual hardening heat heats, regains coarse grain Tissue heredity；Through the coarse grain balance group that the residual forging heat control forging control cold isothermal normalizing process of steel obtains Knit, when usual hardening heat heats, Structure Inheritance does not occur, and obtains small grains tissue, it is ensured that Whole thermal treatment quality；
(5) the forging control cooling after forged of the steel C-curve nose temperature etc. that diffusion coefficient is big to hydrogen solubility is little Temperature keeps, and carries out Dehydroepiandrosterone derivative；
(6) increase Waste Heat Reuse number of times, improve the utilization rate of waste heat of residual forging heat normalized treatment；
(2) K point temperature is (400～550) DEG C；
(3) J1K1For isothermal holding time；
(1) entering slow cooling box from first forging to last part forging, interval time is (90～100) Minute, this is owing to forging is at the Ar of steel1Temperature below long-term heat preservation, can be on pro-eutectoid ferrite crystal boundary Thick tissue occurs；
(2) isothermal holding time starts to calculate isothermal holding time when entering slow cooling box with last part forging, Isothermal holding time J1K1It it is 60 minutes.
5. the isothermal of steel is controlled after keeping and is controlled cooldown rate, cooling uniformity and cold after the cold isothermal for steel keeps But efficiency and cooling termination temperature；
Control steel goes out cooldown rate, cooling uniformity and the cooling effectiveness after slow cooling box and cooling termination temperature.
KL is slowly cooled to room temperature for going out slow cooling box.
Cold isothermal normalizing method is controlled in the residual forging heat control forging of steel, as a example by medium carbon structure steel, describes and realizes this Bright technical scheme and principle, the function obtained, the present invention is also suitable for other steel grades, and other steel grades are for obtaining Function after this steel grade is processed by the invention, its feature, technical scheme, principle, the function that obtains identical it Place, no longer describes, and difference is described as follows:
(1) it is the cutting ability improving mild steel (containing low-carbon low-alloy steel), by steel Normalizing temperature Ac3+ (40～80) DEG C are comparatively fast cooled to the Ar of steel3+ (10～30) DEG C, isothermal in slow cooling box Keep the Ar to steel1-(10～30) DEG C, go out slow cooling box and are comparatively fast cooled to room temperature, arrive improving the hardness of steel The scope of suitable machining, chip frangibility, prevent from being wrapped on workpiece or cutter, improve machining Productivity ratio.
(2) it is the formation effectively suppressing hypereutectoid steel cementite network, does tissue for spheroidizing and prepare, make Spheroidizing is easily given and being carried out, with stable spheroidal annealing quality, it is thus achieved that carbide tiny, equally distributed and ball Change tissue, normalizing temperature Acm+ (30～50) DEG C of steel be quickly cooled to:
(1) C curve nose portion temperature Tp+ (10～30) DEG C of steel, in slow cooling box, isothermal keeps to steel C curve nose portion temperature Tp-(10～30) DEG C, go out slow cooling box and be slowly cooled to room temperature, prevent Crackle, reduces amount of distortion；
(2) temperature Tp ± (10～30) DEG C, C curve nose portion of steel, medium at slow cooling box Temperature keeps 0 second, proceeds to spheroidizing immediately and processes；This is owing to quickly cooling suppresses the formation of cementite network, Proceed to spheroidizing immediately process, the hypereutectoid steel of quickly cooling heated, terminates continuous coo1ing, Isothermal is needed to keep with nodularization during spheroidizing；
(3) all proceed to the most immediately spheroidizing process must be in slow cooling box, by the C curve nose temperature of steel Tp+ (10～30) DEG C of isothermal keeps to Tp-(10～30) DEG C, goes out slow cooling box and is slowly cooled to room temperature；This It is owing to proceeding to spheroidizing the most immediately, the hypereutectoid steel of quickly cooling is not heated, i.e. do not terminate even Continuous cooling, for preventing crackle, reduces amount of distortion, must be in slow cooling box, by the C curve nose portion of steel Temperature Tp+ (10～30) DEG C isothermal keeps to Tp-(10～30) DEG C, goes out slow cooling box and is slowly cooled to room temperature.
(3) after structural steel surface hardening, normalizing conditioning treatment and quenched conditioning treatment, both Strength character, fatigue life is without significant difference；For Simplified flowsheet, with normalizing conditioning treatment replace expensive, The quenched conditioning treatment of high energy consumption, by normalizing temperature Ac of steel3+ (40～80) DEG C are comparatively fast cooled to steel Ar1+ (20～40) DEG C, are quickly cooled to C curve nose temperature Tp+ (30～50) DEG C of steel, In slow cooling box, isothermal keeps C curve nose temperature Tp-(30～50) DEG C to steel, goes out slow cooling box relatively rapid cooling But to room temperature.
(4) for make mild steel (containing low-carbon low-alloy steel) large forgings obtain the ferrite sum that quantity is few Measure many, organize thin pearlite, intensity, plasticity and low-temperature flexibility to be all improved, by the normalizing temperature of steel Ac3+ (30～50) DEG C are cooled to C curve nose temperature Tp+ (10～30) DEG C of steel rapidly, in slow cooling In case, isothermal keeps C curve nose temperature Tp-(10～30) DEG C to steel, goes out slow cooling box and cools down rapidly To (180～240) DEG C, then in static air, it is cooled to room temperature；Avoid large forgings surface because of rapidly Cooling produces the temper brittleness of quenched martensite.
6. cold isothermal normalizing method is controlled in the residual forging heat control forging of steel, it is characterized in that, each critical-temperature of steel is forging Part surface temperature.
Compared with prior art, the invention has the beneficial effects as follows: save the energy and resource, improve normalized treatment matter Amount, reduces normalized treatment cost, alleviates labor strength, raise labour productivity, in advance the duration.
Accompanying drawing explanation
Cold isothermal normalizing method flow chart, abscissa table are controlled in Fig. 1 medium carbon structure steel of the present invention residual forging heat control forging Show that time, ordinate represent temperature；
Fig. 2 present invention stops generation bainite transformation cooling technique process design schematic diagram, when abscissa represents Between, ordinate represents temperature, and C is forging heart portion temperature, and S is forging surface temperature, TcstFor beginning to cool down Temperature, BsFor bainite start temperature；
Fig. 3 medium carbon structure steel tradition isothermal normalizing schematic diagram, abscissa represents that time, ordinate represent temperature；
Fig. 4 medium carbon structure steel of the present invention residual forging heat control forging controls cold isothermal normalizing schematic diagram, when abscissa represents Between, ordinate represents temperature；
First group of judge picture of Fig. 5 GB/T13320-2007 is 8 grades, pearlite+ferrite, Wei Shi soma, Multiplication factor 100 × fractograph；
It is 8 grades that Fig. 6 medium carbon structure steel tradition isothermal normalizing processes forging metallographic structure, pearlite+ferrite, Mixing crystal grain, Wei Shi soma, multiplication factor 100 × fractograph；
First group of judge picture of Fig. 7 GB/T13320-2007 is 7 grades, pearlite+ferrite net, mix-crystal Grain, has a Wei Shi soma, multiplication factor 100 × fractograph；
Fig. 8 medium carbon structure steel residual forging heat normalizing, forging deformation degree every time be 25%, Ar1Temperature is air-cooled, The non-isothermal of C-curve nose keeps, and forging metallographic structure is 7 grades, pearlite+ferrite net, mixes crystal grain, Have a Wei Shi soma, multiplication factor 100 × fractograph；
First group of judge picture of Fig. 9 GB/T13320-2007 is 6 grades, and pearlite+ferrite has Wei Shi body group Knit, multiplication factor 100 × fractograph；
Figure 10 medium carbon structure steel residual forging heat normalizing, forging deformation degree every time be 25%, Ar1Temperature is air-cooled, C-curve nose isothermal keeps, and forging metallographic structure is 6 grades, and pearlite+ferrite has Wei Shi soma, Multiplication factor 100 × fractograph；
First group of judge picture of Figure 11 GB/T13320-2007 is 5 grades, pearlite+ferrite, and crystal grain is uneven Even, multiplication factor 100 × fractograph；
Figure 12 medium carbon structure steel residual forging heat normalizing, forging deformation degree every time be 30%, Ar1Temperature is air-cooled, C-curve nose isothermal keeps, and forging metallographic structure is 5 grades, and pearlite+ferrite, crystal grain is uneven, puts Big multiple 100 × fractograph；
First group of judge picture of Figure 13 GB/T13320-2007 is 4 grades, pearlite+ferrite, and crystal grain is uneven Even, multiplication factor 100 × fractograph；
Figure 14 medium carbon structure steel of the present invention residual forging heat control forging control cold isothermal normalizing, forging deformation degree every time be 25%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps, and forging metallographic structure is 4 grades, pearlite+iron Ferritic, crystal grain is uneven, multiplication factor 100 × fractograph；
First group of judge picture of Figure 15 GB/T13320-2007 is 3 grades, pearlite+ferrite, crystal grain fragmentation, Multiplication factor 100 × fractograph；
Figure 16 medium carbon structure steel of the present invention residual forging heat control forging control cold isothermal normalizing, forging deformation degree every time be 30%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps, and forging metallographic structure is 3 grades, pearlite+iron Ferritic, crystal grain fragmentation, multiplication factor 100 × fractograph；
Figure 17 TP+40℃、Ar1The J point temperature of-80 DEG C and TP+90℃、Ar1The J point temperature of-30 DEG C Number axis figure, dash area is J point temperature range (620～660) DEG C；
Figure 18 TP+ (40～90) DEG C and Ar1Median T of-(30～80) DEG CP+ (40+25) DEG C with Ar1-(30+25) DEG C, J point temperature number axis figure, dash area is J point temperature range (635～645) DEG C.
Detailed description of the invention
With detailed description of the invention, the present invention is described in further detail below in conjunction with the accompanying drawings.
Degree of deformation:
From the viewpoint of metallography, more than recrystallization temperature, do not cause processing hardening plastic history Do thermal deformation processing.Whether this produces processing after deformation processing with metal and is hardened to foundation；Gold in fact Belong in thermal deformation process, also can produce hardening, but owing to the temperature of thermal deformation is far above recrystallization temperature, become Hardening caused by shape is quickly eliminated by simultaneous recrystallization process.
Degree of deformation following formula calculates:
ϵ = H 0 - H 1 H 0 × 100 %
ε degree of deformation (%) in formula；
H0Height (mm) before thermal deformation；
H1Height (mm) after thermal deformation.
The isothermal normalizing process power consumption of conventional steel is big, quality is unstable, the mixed crystal that occurs now and then (see accompanying drawing 5,6), Cost is high, labor strength is heavy, long in time limit；
Traditional isothermal normalizing of steel is that steel heats austenitizing, is quickly cooled to C-curve nose (pregnant after samming Educate the phase the shortest) temperature, carry out having the isothermal of energy supplement to keep in entering heating furnace, overcooling austenite is at this Temperature range changes complete, obtains thinner grain structure, then air cooling, it is thus achieved that preferably machinability Can be with the normalizing method of mechanical property, accompanying drawing 3 is shown in by medium carbon structure steel tradition isothermal normalizing schematic diagram；
The present invention is the normalized treatment production line that forging press is followed by waste heat steel, implements online residual forging heat control forging control Cold isothermal normalizing processes；The residual forging heat of steel, i.e. utilizes the residual forging heat of steel, the control forging of steel, i.e. controls steel Forging temperature and forging deformation degree, cause crystal grain thinning by austenite deformation and recrystallization, the control of steel is cold, According to metallography and Principles of Heating Processing, control the cooldown rate of each critical-temperature of steel, cooling uniformity and cold But efficiency, medium carbon structure steel is cooled to normalizing temperature, quickly the cooling C-curve nose by normalizing temperature to steel Portion's (incubation period is the shortest) temperature, enters slow cooling box and carries out the isothermal holding that noenergy is supplemented, overcooling austenite Change complete in this temperature range, obtain thin grain structure, then control slow cooling box cooldown rate, Cooling uniformity and cooling effectiveness and cooling termination temperature, it is thus achieved that the normalizing method that microstructure and mechanical property is up to standard, Accompanying drawing 4 is shown in by the medium carbon structure steel residual forging heat control of the present invention forging cold isothermal normalizing schematic diagram of control.
Each critical-temperature of described steel is forging surface temperature.
As it is shown in figure 1, the present invention is achieved in that with medium carbon structure steel (containing middle carbon and low-alloy Micro Alloying Steel, lower same) as a example by, method is:
The residual forging heat of steel, it is the residual forging heat utilizing steel, and heat need not reheat acquisition, saves Reheat operation, save the energy and resource.
Control forging temperature and the forging deformation degree of steel；
(1) Forge Heating temperature TA of steel is determined by usual Forge Heating temperature and the initial forging temperature of steel；
Deformation temperature due to steel is higher than the recrystallization temperature of deformed austenite, and Forge Heating temperature should slow down Austria The process that family name's body is grown up because of dynamic and Static Recrystallization crystal grain, AUSTENITE GRAIN COARSENING during to reduce heating, because of This, on the premise of ensureing forging and molding, Forge Heating temperature TA of steel presses the usual Forge Heating temperature of steel Determine with initial forging temperature；
Forge Heating temperature TA of steel is calculated as follows:
TA=(TSD+20)℃
T in formulaSDThe usual initial forging temperature of steel；
The usual Forge Heating temperature of example 55 steel is (1200～1250) DEG C, the usual initial forging temperature T of steelSDValue For (1180～1220) DEG C, then:
TA=(TSD+ 20)+20 DEG C, DEG C=(1180～1220) DEG C=(1200～1240) DEG C；
(2) SB is that the forging of steel is forged in austenite recrystallization temperature scope, and steel is in thermal deformation process, logical Cross deformation and cause Austenite Grain Refinement with recrystallization；
(3) the initial forging temperature S of steel presses the usual initial forging temperature of steel and determines；
Deformation temperature due to steel is higher than the recrystallization temperature of deformed austenite, and initial forging temperature should slow down austenite Because of dynamically and the process grown up of Static Recrystallization crystal grain, make initial forging temperature reduction AUSTENITE GRAIN COARSENING, therefore, On the premise of ensureing forging and molding, initial forging temperature S presses the usual initial forging temperature of steel and determines；
(4) final forging temperature of steel is determined as higher than the austenitizing temperature of steel；
Final forging temperature T of B point temperature steelZDRepresent with following formula:
TZD≥(TA+40)℃
T in formulaAThe austenitizing temperature of steel；
The austenitizing temperature of example 55 steel is 870 DEG C, then: TZD≥(TA+40)℃
TZD≥(870+40)℃
TZD≥910℃
B point temperature is TZD>=910 DEG C, this is owing to B point is final forging temperature, is also deformed austenite after forging Carrying out the starting point of recrystallization, B point temperature is more than minimum deformed austenite recrystallization temperature T95, temperature at this At least there is the recrystallization of 95% in degree, makes the abundant recrystallization of austenite, be conducive to refine, uniform, etc. The austenite crystal of axle；
(5) the forging deformation degree of control steel:
The forging deformation degree of steel be obtained uniformly by austenite deformation and recrystallization, refinement, etc. the Ovshinsky of axle Body crystal grain, it is to avoid critical degree of deformation and big degree of deformation, prevents grain coarsening.
Every time employing 25～40% of the forging deformation degree of steel:
When steel forging deformation degree every time be 25%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps normalizing After, forging metallographic structure reaches first group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
When steel forging deformation degree every time be 40%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps normalizing After, forging metallographic structure reaches first group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
When steel forging deformation degree every time be 30%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps normalizing After, forging metallographic structure reaches first group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
Obtained uniformly by austenite deformation and recrystallization, refinement, etc. the austenite crystal of axle, it is to avoid critical Degree of deformation and the large deformation degree more than 70%, prevent grain coarsening；This be due to:
(1) degree of deformation is less than 20%, there is the small Recovery and recrystallization stage, rapidly enters crystal grain and grows up rank Section；
(2) degree of deformation is little, and during Forge Heating, austenite crystal is roughened, and the degree of deformation less than 20% causes office Portion deforms, and recrystal grain thickness is uneven；
(3) during more than 70% degree of deformation, interior friction makes forging temperature increase, and promotes recrystallization brilliant Grain length is big；
(4) during more than 90% degree of deformation, it is too high that interior friction makes forging temperature increase, and causes secondary Recrystallization, causes crystal grain abnormal thick；
Control the cooldown rate of each critical-temperature, cooling uniformity and the cooling effectiveness of steel；
(6) steel is cooled to the normalizing temperature of steel from final forging temperature；
Steel is from B point temperature TZD>=910 DEG C of normalizing temperatures being cooled to C point temperature steel, Y point is Movement, BY is Slow cooling air cooling, YC for comparatively fast cooling down air cooling, this be due to:
(1) make the abundant recrystallization of deformed austenite of steel, refined, uniformly, etc. the austenite crystal of axle, Grain size distribution is the narrowest more is conducive to suppressing grain coarsening, in order to avoid there is mixed crystal；
(2) cooling velocity of steel is caused by the energy difference on steel surface with cooling medium, the cooling velocity that energy difference is big Greatly, otherwise, cooling velocity is little, so, in same cooling medium, the cooling velocity that the temperature of steel is high is big In the cooling velocity that temperature is low, through the cooling of BC, wherein BY is Slow cooling air cooling, and YC is Very fast cooling is air-cooled, the normalizing temperature that temperature is steel of forging to C point；
C point temperature is steelThis is due to the usual normalizing temperature than sub-eutectoid steelHigh (20～50) DEG C, eliminate the high temperature normalizing temperature of forging Widmannstatten structure than sub-eutectoid steelLow 50 DEG C, high temperature normalizing can eliminate forging Widmannstatten structure, reduces banded structure and makes Calendering longitudinal direction and the horizontal mechanical performance difference become, normalizing temperature usesAnd subsequently Very fast cooling and Ar1The quick cooling of temperature, causes stress big, and hardness is high, for obtaining suitable machining Performance, eliminates forging Widmannstatten structure simultaneously；
BC B cool time1C1It is not more than 60 seconds, i.e. Y1Point moves with Y point and moves, BY air cooling time B1Y1Time Y air-cooled with YC1C1And no more than 60 seconds, steel forging after time of staying length can cause Ovshinsky Growing up of body crystal grain, this is that second stage is recrystallization owing to after steel forging, the first stage is reply, the 3rd Stage is that crystal grain is grown up；
Phase III crystal grain time y following formula of growing up is expressed:
Y=x-(τ1+τ2)
The time of staying after X forging in formula,
τ1Turnaround time first stage,
τ2The second stage recrystallization time；
As X-(τ1+τ2During)=0, the recrystallization stage just terminates, obtain be distortionless wait axle again Crystallization initial grain；
As X-(τ1+τ2) ＜ 0 time, recrystallization is insufficient, it is impossible to refined, uniformly, etc. axle Crystal grain；
As X-(τ1+τ2) ＞ 0 time, work as τ1+τ2For definite value, when variable X value is big, then y value is also Greatly, so phase III crystal grain is grown up, the time is long, causes grain coarsening；
(7) CD is that very fast cooling is air-cooled, from steelAir-cooled to Ar1Temperature, this It is due to slow in normalizing temperature cooling velocity after forging, causes grain coarsening；
D point temperature is the Ar of steel1+ (30～40) DEG C；
(8) DE is Slow cooling air cooling, and this is owing to CD is air-cooled, and air-cooled speed is more than air cooling speed Degree, causes forging temperature field deviation, and heart portion temperature is higher than surface temperature, according to be high-energy inside the matters to The Changing Pattern of low-energy state transfer, by heat transfer, forging temperature field is in sub-poised state, now Air cooling plays the effect of uniform temperature and cooling:
(1) uniformity, cooldown rate and cooling effectiveness that next step EF quickly cools down are improved；(2) under stoping
One step EF quickly cools down and causes forging surface that bainite transformation occurs, with Obtain suitable machinability；
E point temperature is the Ar of steel1+ (20～30) DEG C；
(9) EF is that quickly cooling mist is cold, this be due to:
(1) universal law of tissue effect after steel normalizing is by cooling velocity: cooling velocity is big, and austenite divides Solution temperature is low, and perlitic transformation product is tiny, for making the residual forging heat control cold normalizing metallographic structure of steel reach First group of judge picture of GB/T13320-2007 1～4 grades of qualified requirements；
(2) it is the Ar quickly through steel1Temperature, prevents from occurring thick tissue on pro-eutectoid ferrite crystal boundary；
Medium carbon structure steel residual forging heat normalizing, forging deformation degree every time be 25%, Ar1Temperature is air-cooled, and C-is bent Line nose isothermal keeps, and forging metallographic structure is 6 grades, sees accompanying drawing 9,10；
Medium carbon structure steel residual forging heat normalizing, forging deformation degree every time be 30%, Ar1Temperature is air-cooled, and C-is bent Line nose isothermal keeps, and forging metallographic structure is 5 grades, sees accompanying drawing 11,12；
EF uses air-cooled, and air-cooled speed is less than mist speed of cooling, air-cooled not as good as the cold Ar quickly through steel of mist1Temperature, After isothermal normalizing: forging deformation degree every time be 25%, forging metallographic structure is 6 grades, forging deformation degree per pass Secondary is 30%, and forging metallographic structure is 5 grades, first group of judge picture of the most not up to GB/T13220-2007 1～4 The requirement that level is qualified；
Medium carbon structure steel residual forging heat control of the present invention forging control cold isothermal normalizing, forging deformation degree every time be 25%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps, and forging metallographic structure is 4 grades, sees accompanying drawing 13,14；
Medium carbon structure steel residual forging heat control of the present invention forging control cold isothermal normalizing, forging deformation degree every time be 30%, Ar1Temperature mist is cold, and C-curve nose isothermal keeps, and forging metallographic structure is 3 grades, sees accompanying drawing 15,16；
EF uses mist cold, accelerates the Ar by steel1Temperature, after isothermal normalizing: forging deformation degree every time be 25%, Forging metallographic structure is 4 grades, forging deformation degree every time be 30%, forging metallographic structure is 3 grades, all reaches First group of judge picture of GB/T13220-2007 1～4 grades of qualified requirements；
Owing to EF uses mist cold, after isothermal normalizing, metallographic structure is up to standard, and hardness exceeds standard, and increases machining Difficulty, for obtaining suitable machinability, from mist cold → air-cooled → isothermal keeps, stop and bayesian occur Body changes cooling process and is designed, and sees accompanying drawing 2；
Control surface (S) temperature more than bainite start temperature, i.e. BSMore than line (20～30) DEG C, Stop and bainite transformation occurs；
F point temperature is the Ar of steel1(0～10) DEG C；
(10) FG is Slow cooling air cooling, and this is owing to EF is that mist is cold, and mist speed of cooling is more than air-cooled speed Degree, causes the deviation that forging temperature field is big, and heart portion temperature is higher than surface temperature, according to being high energy inside the matters Measuring the Changing Pattern to low-energy state transfer, by heat transfer, forging temperature field is in sub-poised state, The now effect of air cooling:
(1) effect of uniform temperature is played；
1) uniformity, cooldown rate and cooling effectiveness that next step GH comparatively fast cools down are improved；
2) stoping next step GH comparatively fast to cool down causes forging surface that bainite transformation occurs, suitable to obtain Machinability；
(2) cooling after samming and the common effect of air cooling, quickly through the Ar of steel1Temperature；
G point temperature is the Ar of steel1(10～20) DEG C；
(11) GH is that very fast cooling is air-cooled, and H point temperature is the Ar of steel1-(20～30) DEG C, this Point is the Ar quickly through steel1Temperature terminates；
(12) HJ is Slow cooling air cooling, and this is owing to air cooling plays the effect of uniform temperature and cooling, The isothermal holding that noenergy is supplemented is entered with temperature accurately；
J point be forging enter slow cooling box carry out noenergy supplement isothermal keep beginning, for from entering slow cooling box J point Temperature keeps at least 20 minutes to nose " upper C-curve " temperature isothermal, makes Cooling Austenite Transformation become pearlite, Nose " lower C-curve " temperature will not be entered in 20 minutes by isothermal temperature, stop and bainite transformation occurs, obtain Suitable machinability:
(1) J point temperature is C-curve nose portion temperature T of steelP+ (40～90) DEG C, and meet the Ar of steel1 -(30～80) DEG C, offset forging have in slow cooling box a small amount of heat scatter and disappear cooling and in slow cooling box isothermal protect The temperature held slowly is successively decreased；
The T of example 55 steelpIt is 580 DEG C, Ar1It is 690 DEG C, substitutes into:
1)Tp+ 40 DEG C=580 DEG C+40 DEG C=620 DEG C；
Ar1-80 DEG C=690 DEG C-80 DEG C=610 DEG C
J point temperature is 620 DEG C, sees accompanying drawing 17；
2)Tp+ 90 DEG C=580 DEG C+90 DEG C=670 DEG C,
Ar1-30 DEG C=690 DEG C-30 DEG C=660 DEG C
J point temperature is 660 DEG C, sees accompanying drawing 17；
Comprehensive 1) and 2), J point temperature is (620～660) DEG C, sees accompanying drawing 17 dash area；
3)Tp+ (40+25) DEG C=580 DEG C+(40+25) DEG C=645 DEG C,
Ar1-(30+25) DEG C=690 DEG C-(30+25) DEG C=635 DEG C,
J point temperature is (635～645) DEG C, sees accompanying drawing 18 dash area；
(2) slow cooling box good heat insulating；
(3) forging is automatically switched off slow cooling box entrance, immediately to reduce heat after entering slow cooling box Scatter and disappear from porch, preserve waste heat and carry out isothermal holding, after pouring out hot water just as vacuum flask, immediately will insulation Bottle stopper covers bottleneck, lost from bottle mouth position to reduce heat.
The isothermal normalizing of steel be steel critical-temperature isothermal keep carry out normalized treatment；
Steel quickly cools down the critical-temperature C-curve nose temperature by normalizing temperature to steel, at the C-of steel Curve nose temperature isothermal keeps carrying out normalized treatment；
(13) JK be isothermal keep, this be due to:
(1) overcooling austenite of steel changes complete in this temperature range, obtains thin pearlitic structrure；
(2) universal law of performance impact after steel normalizing is by cooling velocity: cooling velocity is big, and stress is big, Hardness is high, and after cold isothermal normalizing is controlled in the residual forging heat control forging of steel, metallographic structure reaches GB/T13320-2007 the One group of judge picture 1～4 grades of qualified requirements, for eliminating the Ar at steel1The cold stress caused of temperature mist is big, hard Degree height, thus obtain suitable machinability；
(3) Ar of steel1It is cold that temperature is provided without quickly cooling down mist, and uses very fast cooling air-cooled, The most the C-curve nose temperature isothermal at steel does not keeps, and after normalized treatment, metallographic structure is thick, for 7 grades of first group of judge picture of GB/T13320-2007；See accompanying drawing 7,8；
(4) being balanced tissue, the statenchyma obtained processed by the invention, the coarse grain eliminating steel is non- Statenchyma, when usual hardening heat heats, regains the tissue heredity of coarse grain；Through the present invention Process the coarse grain statenchyma of the steel obtained, when usual hardening heat heats, Structure Inheritance do not occur, And obtain small grains tissue, it is ensured that finished heat treatment quality；
(5) the forging control cooling after forged of the steel C-curve nose temperature etc. that diffusion coefficient is big to hydrogen solubility is little Temperature keeps, and carries out Dehydroepiandrosterone derivative；
(6) increase Waste Heat Reuse number of times, improve the utilization rate of waste heat of residual forging heat normalized treatment；
K point temperature is (400～550) DEG C；
(14) J1K1For isothermal holding time
(1) entering slow cooling box from first forging to last part forging, interval time is (90～100) point Clock, this is owing to forging is at the Ar of steel1Temperature below long-term heat preservation, can go out on pro-eutectoid ferrite crystal boundary Existing thick tissue；
(2) isothermal holding time starts to calculate isothermal holding time when entering slow cooling box with last part forging, Isothermal holding time J1K1It it is 60 minutes；
Control steel goes out cooldown rate, cooling uniformity and the cooling effectiveness after slow cooling box and cooling termination temperature；
(15) KL is for going out slow cooling box Slow cooling air cooling to room temperature.
Cold isothermal normalizing method is controlled in the residual forging heat control forging of steel, as a example by medium carbon structure steel, describes and realizes this Bright technical scheme and principle, the function obtained, the present invention is also suitable for other steel grades, and other steel grades are for obtaining Function after this steel grade is processed by the invention, its feature, technical scheme, principle, the function that obtains identical it Place, no longer describes, and difference is described as follows:
(16) are the cutting ability improving mild steel (containing low-carbon low-alloy steel), by the normalizing temperature of steel Ac3The air-cooled Ar to steel of+(40～80) DEG C very fast cooling3+ (10～30) DEG C, isothermal in slow cooling box Keep the Ar to steel1-(10～30) DEG C, go out slow cooling box and comparatively fast cool down air-cooled to room temperature, to improve steel Hardness to the scope of suitable machining, chip frangibility, prevent from being wrapped on workpiece or cutter, improve Machining productivity ratio.
(17) are the formation effectively suppressing hypereutectoid steel cementite network, do tissue for spheroidizing and prepare, make Spheroidizing is easily given and being carried out, and stablizes spheroidal annealing quality, it is thus achieved that carbide tiny, equally distributed and nodularization Tissue, is cooled to by the quick cooling mist of normalizing temperature Acm+ (30～50) DEG C of steel:
(1) C curve nose portion temperature Tp+ (10～30) DEG C of steel, medium at slow cooling box Temperature keeps C curve nose portion temperature Tp-(10～30) DEG C to steel, goes out slow cooling box Slow cooling empty It is cooled to room temperature, prevents crackle, reduce amount of distortion；
(2) temperature Tp ± (10～30) DEG C, C curve nose portion of steel, in slow cooling box, isothermal keeps 0 Second, proceed to spheroidizing immediately and process；This is due to the formation of mist cold suppression cementite network, proceeds to ball immediately Annealing processes, and the hypereutectoid steel cold to mist heats, and terminates continuous coo1ing, in spheroidizing process In need isothermal keep with nodularization；
(3) all proceed to the most immediately spheroidizing process must be in slow cooling box, by the C curve nose portion temperature of steel Degree Tp+ (10～30) DEG C isothermal keeps to Tp-(10～30) DEG C, goes out slow cooling box Slow cooling air cooling To room temperature；This is owing to proceeding to spheroidizing the most immediately, not heating the hypereutectoid steel that mist is cold, the most not Terminate continuous coo1ing, for preventing crackle, reduce amount of distortion, must be in slow cooling box, by the C curve of steel Nose portion temperature Tp+ (10～30) DEG C isothermal keeps to Tp-(10～30) DEG C, goes out slow cooling box air cooling to room temperature.
After (18) structural steel surface hardening, normalizing conditioning treatment and quenched conditioning treatment, both Strength character, fatigue life are without significant difference；For Simplified flowsheet, with normalizing conditioning treatment replace expensive, The quenched conditioning treatment of high energy consumption, by normalizing temperature Ac of steel3The very fast cooling wind in+(40～80) DEG C It is cooled to the Ar of steel1+ (20～40) DEG C, quickly cooling mist is cooled to C curve nose portion temperature Tp+ of steel (30～50) DEG C, in slow cooling box, isothermal keeps C curve nose portion temperature Tp-(20～40) DEG C to steel, Go out slow cooling box and comparatively fast cool down air-cooled to room temperature.
(19) are for make mild steel (containing low-carbon low-alloy steel) large forgings obtain the ferrite sum that quantity is few Measure many, organize thin pearlite, intensity, plasticity and low-temperature flexibility to be all improved, by the normalizing temperature of steel Ac3+ (30～50) DEG C cool down mass fraction rapidly and are cooled to steel for (5～10) %NaCI aqueous solution C curve nose portion temperature Tp+ (10～30) DEG C, in slow cooling box, isothermal keeps the C to steel bent Line nose portion temperature Tp-(10～30) DEG C, go out slow cooling box cooling down mass fraction rapidly is (5～10) %NaCI The aqueous solution is cooled to (180～240) DEG C, is then cooled to room temperature in static air, it is to avoid large forgings Superficial layer produces the temper brittleness of quenched martensite because cooling down rapidly.

Claims (6)

1. a residual forging heat normalizing method for steel, is characterized in that: Described method is that the residual forging heat utilizing steel is carried out:
(1) the control forging of steel, i.e. controls forging temperature and the forging deformation degree of steel；
(2) control of steel is cold, i.e. controls the cooldown rate of each critical-temperature, cooling uniformity and the cooling effectiveness of steel；
(3) isothermal normalizing of steel, i.e. the critical-temperature isothermal at steel keep carrying out normalized treatment；
(4) isothermal of steel is controlled cold after keeping, and controls cooldown rate, cooling uniformity and cooling effectiveness and cooling termination temperature after i.e. the isothermal of steel keeps.
The residual forging heat normalizing method of a kind of steel the most as claimed in claim 1, is characterized in that: forging temperature and the forging deformation degree of described control steel be:
(1) forging temperature of control steel:
(1) the Forge Heating temperature of steel is determined by usual Forge Heating temperature and the initial forging temperature of steel；
(2) the austenite recrystallization temperature scope at steel that is forged to of steel is forged；
(3) initial forging temperature of steel is determined by the usual initial forging temperature of steel；
(4) final forging temperature of steel is determined as higher than the austenitizing temperature of steel；
(2) the forging deformation degree of control steel:
The forging deformation degree of steel be obtained uniformly by austenite deformation and recrystallization, refinement, etc. the austenite crystal of axle, it is to avoid critical degree of deformation and big degree of deformation, prevent grain coarsening.
The residual forging heat normalizing method of a kind of steel the most as claimed in claim 1, is characterized in that: the cooldown rate of each critical-temperature, cooling uniformity and the cooling effectiveness of described control steel be:
(1) steel is cooled to the normalizing temperature of steel from final forging temperature；
(2) steel quickly cools down the normalizing temperature by steel.
The residual forging heat normalizing method of a kind of steel the most as claimed in claim 1, is characterized in that: the described critical-temperature isothermal holding at steel carries out normalized treatment and is:
(1) steel quickly cools down the critical-temperature by the normalizing temperature of steel to steel；
(2) the critical-temperature isothermal at steel keeps carrying out normalized treatment.
The residual forging heat normalizing method of a kind of steel the most as claimed in claim 1, is characterized in that: the isothermal of described steel controls cooldown rate, cooling uniformity and cooling effectiveness after keeping and cooling termination temperature is: control cooldown rate, cooling uniformity and cooling effectiveness after steel isothermal keeps and cooling termination temperature.
The residual forging heat normalizing method of a kind of steel the most as claimed in claim 1, is characterized in that: each critical-temperature of described steel is forging surface temperature.
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