CN109811114A - A kind of fine grain intensive quenching cooling means of steel - Google Patents

A kind of fine grain intensive quenching cooling means of steel Download PDF

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Publication number
CN109811114A
CN109811114A CN201811275456.3A CN201811275456A CN109811114A CN 109811114 A CN109811114 A CN 109811114A CN 201811275456 A CN201811275456 A CN 201811275456A CN 109811114 A CN109811114 A CN 109811114A
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steel
temperature
cooling
isothermal
waste heat
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王长文
王中忞
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Individual
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Priority to CN201811275456.3A priority Critical patent/CN109811114A/en
Priority to CN202110215559.6A priority patent/CN113355493A/en
Priority to CN202011375574.9A priority patent/CN112575157A/en
Priority to CN202110379946.3A priority patent/CN113215364A/en
Publication of CN109811114A publication Critical patent/CN109811114A/en
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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
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite

Abstract

A kind of fine grain intensive quenching cooling means of steel.With " invertibity of martensite transfor mation " rule, the obdurability of steel is improved with heat treatment method refinement crystal grain.Steel provides condition in austenitization, for martensite reverted austenite；After the steel austenitizing for having martensite reverted austenite condition, when water cooling is not cold around C- curve range of instability to martensitic regions after pre-cooling, martensite nucleus is gradually grown up with temperature decline；Water outlet is risen again using waste heat, and when temperature rises, martensite is again synchronous in turn to be reduced with temperature rising, i.e. refinement crystal grain.It include: the austenitizing of steel, as martensite reverted austenite provides condition；The control of the pre-cooling of steel, steel is cold, the isothermal hardening of steel, the grade quench of steel, single medium water hardening of steel, the interrupted quenching of steel.The energy saving and resource of present invention energy protects environment, and refinement crystal grain improves the obdurability of steel, and the raising of tensile strength solves fine grain Strengthening and Toughening problem at big section steel part 1/2T greater than the raising of yield strength.

Description

A kind of fine grain intensive quenching cooling means of steel
Technical field
The present invention relates to a kind of Heat-Treatment of Steel method more particularly to a kind of fine grain intensive quenching cooling means of steel.
Background technique
The refined crystalline strengthening of prior art steel, the energy and big, seriously polluted, at high cost, the big section steel part 1/2T of resource consumption Place's quality and technical index is difficult to up to standard；Prior art characteristic is:
The refined crystalline strengthening of steel is added in steel: reducing the alloying element of critical point, such as Mn, Cr, Mo；Improve forming core Rate, the microalloy element of Austenite Grain Growth, such as Ti, Nb, V when preventing Warm status；The raising of yield strength is caused to be greater than The raising of tensile strength, yield tensile ratio value increase；
The consistency of the refined crystalline strengthening effect of steel is the running by microalloy element (Ti, Nb, V etc.) ingredient；
It is pre-chilled in heating furnace, hypereutectoid steel, which is transferred to, is heated to Ar1It is cooled to Ar in advance in (10 DEG C~30 DEG C) temperature furnace1-(10 DEG C~30 DEG C) temperature, sub-eutectoid steel is cooled to intercritical hardening temperature in advance in former heating furnace；It is transferred in single medium again cooling；
It is pre-chilled in the oil, is transferred to oil cold several seconds, play pre-cooling, then be transferred in water cooling；
The harden ability for improving steel is the alloying element that sufficient amount is added in steel and stablizes overcooling austenite, changes C- curved shape It shape and elapses C- curve to the right, reduces critical quenching rate to realize and improve quenching cooling velocity, to improve the through hardening of steel Property；
The alloying element that sufficient amount stablizes overcooling austenite is added in big section steel part in steel, changes C- curve shape and makes C- curve elapses to the right, reduces critical quenching rate to realize and improve quenching cooling velocity, to improve the harden ability of steel, steel exists Ms (martensite start) point Ms isothermal temperature on the upper side or on the lower side can be directly cooled in the melting salt bath or hot oil slot of temperature control Or hierarchical temperature, have the isothermal of energy supplement to keep the temperature；
The isothermal hardening and grade quench of steel go out melting salt bath or hot oil slot is air-cooled to room temperature；
Single medium water hardening of steel is cooled to~80 DEG C in water, and water outlet is air-cooled to room temperature；
The interrupted quenching of steel is cooled to room temperature in the relatively weak medium of cooling capacity；
The above problem can be solved using technical solution of the present invention.
Summary of the invention
In order to solve the above-mentioned technical problem, the present invention is achieved by the following technical solutions；
The purpose of the present invention is to provide a kind of fine grain intensive quenching cooling means of steel, overcome it is in the prior art not Foot, this method refines crystal grain with " invertibity of martensite transfor mation " rule, with heat-treating methods, to improve the tough of steel Property；
The invention is realized in this way it is characterized in that method are as follows:
1. cooling for the first time bent around C- in mass fraction 5%~10%NaCl aqueous solution after pre-cooling after steel austenitizing Line range of instability --- nose portion temperature to martensitic regions and it is not cold, be discharged to rise again using waste heat to bainite transformation for the first time and open Beginning temperature Bs+ (50 DEG C~100 DEG C), but perlitic transformation temperature must be lower than, it is transferred to mass fraction 5%~10%NaCl water immediately Martensitic regions are cooled to again in solution and not cold, be discharged risen again the temperature for stopping rising using waste heat again, according to difference Steel grade and different process for quenching, be steel quenching under cooling together start temperature --- Ms (martensite start) point Ms is on the upper side Or temperature on the lower side；
The described method includes:
(1) austenitizing of steel；
(2) pre-cooling of steel；
(3) control of steel is cold；
(4) isothermal hardening of steel；
(5) grade quench of steel；
(6) single medium water hardening of steel；
(7) interrupted quenching of steel.
2. the austenitizing of steel are as follows:
(1) quenching temperature of steel, soaking time and heating rate are to reduce austenite to change start temperature As, are mentioned High Ms (martensite start) point Ms reduces the temperature difference of As and Ms, provides condition for martensite reverted austenite, mentioned with refining crystal grain The obdurability of Gao Gang；
(2) quenching preheating number, temperature, soaking time and the heating rate of steel are to reduce austenite to change start temperature As improves Ms (martensite start) point Ms, reduces As and Ms temperature difference, condition is provided for martensite reverted austenite, to refine crystalline substance Grain improves the obdurability of steel.
3. the pre-cooling of steel are as follows:
(1) it after steel austenitizing, comes out of the stove and is pre-chilled in air；
(2) precooling temperature of the steel of different steel grades is；
(1) eutectoid steel and hypereutectoid steel are Ar1(10 DEG C~30 DEG C)；
(2) sub-eutectoid steel is Ac1+ (50 DEG C~80 DEG C), but must < Ac3；
(3) pre-cooling of steel is precooling temperature, is transferred to cooling in mass fraction 5%~10%NaCl aqueous solution immediately, prevents Pre-cooling is insufficient or exaggerates.
4. the control of steel is cold are as follows:
(1) after steel austenitizing, surface layer certain depth is cold in mass fraction 5%~10%NaCl aqueous solution after pre-cooling But C- curve range of instability --- the not cold degree of nose portion temperature to Ms (martensite start) point Ms or less is bypassed, and is reached To each critical point desired temperature；
(2) cooling for the first time in mass fraction 5%~10%NaCl aqueous solution after pre-cooling to bypass C- after steel austenitizing Curve range of instability --- the nose portion temperature degree not cold to martensitic regions, i.e. cooling time for the first time are as follows: be discharged for the first time It is risen again using waste heat to bainite start temperature Bs+ (50 DEG C~100 DEG C), but perlitic transformation temperature must be lower than；
(3) steel is discharged for the first time is risen again using waste heat to bainite start temperature Bs+ (50 DEG C~100 DEG C), but must be low In perlitic transformation temperature, it is transferred in mass fraction 5%~10%NaCl aqueous solution and cools down again immediately；
(4) steel is cooled to martensitic regions and not cold journey again in mass fraction 5%~10%NaCl aqueous solution Degree, i.e. cooling time again are as follows: be discharged risen again the temperature for stopping rising using waste heat again, according to different steel grades and different quenchings Method, be steel quenching under cooling start temperature together --- Ms (martensite start) point Ms is on the upper side or temperature on the lower side.
5. the isothermal hardening of steel are as follows:
(1) steel be discharged again using waste heat rise again stop rise temperature be steel enter in slow cooling box using waste heat progress Noenergy supplements the isothermal start temperature that isothermal is kept；
(3) the isothermal start temperature of steel is Ms+ (20 DEG C~50 DEG C)；
(3) steel is isothermal start temperature, is transferred in slow cooling box and is protected using the isothermal that waste heat carries out noenergy supplement immediately It holds；
(4) steel is kept in slow cooling box using the isothermal that waste heat carries out noenergy supplement with isothermal start temperature, will be continuous Cooling process merges to be kept in process in isothermal；
(5) performance requirement of slow cooling box；
(6) isothermal time of steel；
(1) steel is isothermal start temperature, is transferred in slow cooling box and is kept using the isothermal that waste heat carries out noenergy supplement immediately, Start to calculate isothermal time；
(2) isothermal time of steel be bainite transformation start and end of a period line the time required to 50%~70%；
(7) go out slow cooling box after steel isothermal is kept, be transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously cold But to room temperature；
(8) the interrupted water cooling of steel is transferred to down one of heat treatment procedure to room temperature immediately.
6. the grade quench of steel are as follows:
(1) steel be discharged again using waste heat rise again stop rise temperature be steel enter stand air in using waste heat into Row noenergy supplements the classification start temperature that isothermal is kept；
(2) the classification start temperature of the steel of different steel grades are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) steel is classification start temperature, is transferred to stand in air immediately and be protected using the isothermal that waste heat carries out noenergy supplement It holds；
(4) steel is kept with being classified start temperature in standing air using the isothermal that waste heat carries out noenergy supplement, will even Continuous cooling process merges to be kept in process in isothermal；
(5) grading time of steel；
(1) steel is classification start temperature, is transferred to stand in air immediately and be protected using the isothermal that waste heat carries out noenergy supplement It holds, starts to calculate grading time；
(2) grading time of steel is (90~120) s；
(6) go out to stand air after steel isothermal is kept, be transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously It is cooled to room temperature；
(7) the interrupted water cooling of steel is transferred to down one of heat treatment procedure to room temperature immediately.
7. single medium water hardening of steel are as follows:
(1) it is single medium quenching of steel in mass fraction 5% that steel is discharged the temperature risen again using waste heat and stop rising again Continue cooling start temperature in~10%NaCl aqueous solution；
(2) steel of different steel grades continues the start temperature of water cooling are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) steel is the start temperature for continuing water cooling, is transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously It is cooled to room temperature, carries out single medium water hardening processing of steel；
(4) the interrupted water cooling of steel is transferred to down one of heat treatment procedure to room temperature immediately.
8. the interrupted quenching of steel are as follows:
(1) it is the interrupted quenching of steel in cooling capacity phase that steel is discharged the temperature risen again using waste heat and stop rising again To start temperature cooling in weak medium；
(2) steel of different steel grades start temperature cooling in the relatively weak medium of cooling capacity are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) steel is cooling start temperature in the relatively weak medium of cooling capacity, is transferred to relatively weak Jie of cooling capacity immediately It is cooled down in matter and not cold；
(4) steel go out the relatively weak medium of cooling capacity using waste heat rise again stop rise temperature be mass fraction 5%~ Start temperature cooling for the third time in 10%NaCl aqueous solution；
(5) steel is the start temperature of third time water cooling, is transferred to immediately cold in mass fraction 5%~10%NaCl aqueous solution But to room temperature；
(6) molten steel is cooled to room temperature, is transferred to down one of heat treatment procedure immediately.
9. mass fraction 5%~10%NaCl aqueous temperature is controlled at 18 DEG C~38 DEG C.
Compared with prior art, the beneficial effects of the present invention are: improving the obdurability of steel with heat treatment method refinement crystal grain, The raising of tensile strength is greater than the raising of yield strength, and energy saving and resource protects environment, reduces cost, reduce the carbon of steel Equivalent improves the welding performance of steel, and process merges, shortens the construction period, solve fine grain Strengthening and Toughening problem at big section steel part 1/2T.
Detailed description of the invention
The fine grain intensive quenching cooling means flow chart of Fig. 1 steel of the present invention, abscissa indicate the time, and ordinate indicates Temperature, DEG C.
Cooling process schematic diagram after the fine grain intensive quenching cooling means pre-cooling of Fig. 2 steel of the present invention, when abscissa indicates Between, lg τ；Ordinate indicates temperature, DEG C；Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is pearl The range of instability nose portion temperature of body of light transition temperature --- C- curve, c are steel core portion temperature, and s is steel surface temperature.
The isothermal hardening schematic diagram of Fig. 3 prior art steel, abscissa indicate time, lg τ；Ordinate indicates temperature, DEG C； Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is perlitic transformation temperature.
The cooling of the fine grain Strengthening and Toughening isothermal hardening of Fig. 4 steel of the present invention and isothermal schematic diagram, abscissa indicate time, lg τ；Ordinate indicates temperature, DEG C；Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is pearlite Transition temperature.
The grade quench schematic diagram of Fig. 5 prior art steel, abscissa indicate time, lg τ；Ordinate indicates temperature, DEG C； Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is perlitic transformation temperature, and c is steel core portion temperature Degree.
The cooling of the fine grain Strengthening and Toughening grade quench of Fig. 6 steel of the present invention and classification schematic diagram, abscissa indicate time, lg τ；Ordinate indicates temperature, DEG C；Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is pearlite Transition temperature, c are steel core portion temperature.
The cooling schematic diagram of the fine grain Strengthening and Toughening list medium water hardening of Fig. 7 steel of the present invention, abscissa indicate time, lg τ；Ordinate indicates temperature, DEG C；Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is pearlite Transition temperature, c are steel core portion temperature.
The cooling schematic diagram of the fine grain Strengthening and Toughening interrupted quenching of Fig. 8 steel of the present invention, abscissa indicate time, lg τ；It is vertical Coordinate representation temperature, DEG C；Ms is Ms (martensite start) point, and Bs is bainite start temperature, and Tp is perlitic transformation Temperature, c are steel core portion temperature.
Specific embodiment
Present invention is further described in detail with specific embodiment with reference to the accompanying drawing.
The present invention is described in detail now with reference to the embodiment for the several recommendations being illustrated in attached drawing；It is retouched below In stating, in order to enable the invention to thoroughly be understood, several concrete details are proposed；It will be clear that not having for those skilled in the art Have in these details certain some or all, the present invention also can be implemented；In some examples, in order to avoid unnecessarily The present invention is become blurred, well-known processing step is not explained in detail.It is heat-treated degree-of-difficulty factor:
After steel heating is transformed into austenite, it is cooled to critical point A in water1Temperature do not change immediately, at this time Existing austenite is known as overcooling austenite；When overcooling austenite is cooled to lower than Ar1A certain temperature when, will decompose, And it is transformed into its hetero-organization.
Heat treatment degree-of-difficulty factor is that (steel part internal and external temperature uniformity, austenite homogenization, phase transformation are complete for steel austenitizing At austenite grain must not grow up, and expense is low) after, it is cooled in water at center portion 1/2T lower than Ar1A certain temperature when, Decompose and be transformed into the complexity of martensite or lower bainite.
Heat treatment degree-of-difficulty factor is calculated as follows:
N in formula --- heat treatment degree-of-difficulty factor (mm)；
Cooling volume (the mm of V --- steel3)；
Film-cooled heat (the mm of S --- steel2)；
Refined crystalline strengthening is uniquely to improve yield strength simultaneously, improves the schedule of reinforcement of toughness, therefore, referred to as fine grain is strong Toughening；
As shown in Figure 1, the invention is realized in this way, method are as follows:
With " invertibity of martensite transfor mation " rule, crystal grain is refined with heat treatment method, to improve the obdurability of steel.
1. after steel austenitizing EF, be pre-chilled after FY cooled down for the first time in mass fraction 5%~10%NaCl aqueous solution YG around Cross C- curve range of instability --- nose portion temperature to martensitic regions and it is not cold, be discharged risen again using waste heat to the temperature of H for the first time Degree is bainite start temperature Bs+ (50 DEG C~100 DEG C), but must be lower than perlitic transformation temperature, is transferred to quality point immediately In number 5%~10%NaCl aqueous solution again cool down HJ to martensitic regions and it is not cold, be discharged to rise again using waste heat to K again and stop The temperature only risen, start temperature --- the geneva cooled down together under the quenching that different process for quenching are steel according to different steel grades Body changes that start temperature Ms is on the upper side or temperature on the lower side；See Fig. 2；
The refined crystalline strengthening of prior art steel is added in steel: reducing the alloying element of critical point, such as Mn, Cr, Mo；It mentions High nucleation rate, the microalloy element of Austenite Grain Growth, such as Ti, Nb, V when preventing Warm status；Cause mentioning for yield strength The tall and big raising in tensile strength, yield tensile ratio value increase, and both consume alloy resource, improve the cost and carbon equivalent of steel, reduce steel Welding performance, and it is unfavorable to the safety and cold-forming property of steel；Raising just because of yield strength is greater than tensile strength Raising, yield tensile ratio value increases, unfavorable to the safety and cold-forming property of steel, therefore, to the raising of steel part yield strength and Yield tensile ratio value limits, and the raising of yield strength must not exceed the 110% of standard value, and yield tensile ratio value must not exceed 0.9；
The present invention improves the tough of steel with " invertibity of martensite transfor mation " rule, with heat treatment method refinement crystal grain Property；Steel reduces austenite and changes start temperature As, improve Ms (martensite start) point Ms, reduce in austenitization As and Ms temperature difference, provide condition for martensite reverted austenite；After the steel austenitizing for having martensite reverted austenite condition, after pre-cooling Water cooling is not cold around C- curve range of instability to Ms (martensite start) point Ms or less, and martensite nucleus declines with temperature And it gradually grows up；Water outlet is risen again using waste heat, and temperature rises, and martensite synchronizes the rising with temperature again in turn and reduces, i.e., The obdurability that crystal grain improves steel is refined, the raising of tensile strength is made to be greater than the raising of yield strength, yield tensile ratio value reduces, both saved Alloy resource reduces the cost and carbon equivalent of steel, improves the welding performance of steel, and is conducive to safety and the cold-forming property of steel, Solve fine grain Strengthening and Toughening problem at big section steel part 1/2T；
Low-carbon and low-alloy ASTM A694F65 steel, carbon equivalent ce≤0.43,160 millimeters of effective thickness, supplier, demander, Under third party BV tripartite witnesses jointly, after carrying out Q+T heat treatment by the present invention and the isothermal tempering cooling means of steel, taken through ontology Properties and tissue are up to standard at sample detection 1/2T, and performance and histologic results are as follows at steel part 1/2T:
(1) performance: σ s is 480Mpa, is the 107% of standard value (>=450Mpa)；σbFor 605Mpa, be standard value (>= 530Mpa) 113%；δ is 30.5%, is the 152% of standard value (>=20%)；- 46 DEG C of notched bar impact strengths: tangential AkFor 255J It (252/253/259), is the 637% of standard value (average >=40J, single >=30J)；Axial AkFor 270J (274/272/264), It is the 675% of standard value (average >=40J, single >=30J)；
1) the yield tensile ratio standard value of prior art refined crystalline strengthening is 0.85 (450Mpa/530Mpa), and fine grain of the present invention is tough The yield tensile ratio value of change is 0.79 (480Mpa/605Mpa), and yield strength is the 107% of prior art standard value, tensile strength It is the 113% of prior art standard value, the raising of tensile strength is greater than the raising of yield strength, and yield tensile ratio value reduces；
2) consistency of prior art refined crystalline strengthening effect is by microalloy element (Ti, Nb, V etc.) into sub-operation, brilliant It is inappropriate that grain, which further refines and improves production cost from economic aspect, is strictly to limit from the raising of aspect of performance yield tensile ratio value 's；Present invention heat treatment method fine grain Strengthening and Toughening, does not increase production cost, and yield tensile ratio value reduces, and toughness is tangentially and axial direction Ak Value is six times of standard value or more, and organizes deviation and be no more than 10J, is conducive to crystal grain and further refines；
(2) tissue: quenching temperature is 20 DEG C~40 DEG C higher than former heating temperature, and metallographic structure grain size is more brilliant than former instead 1~2 grade of fine size；This is deformed by martensite reverse, when steel has the martensite reverted austenite item for reducing As and Ms temperature difference Part, after steel austenitizing, after pre-cooling twice water cooling around C- curve range of instability to martensitic regions not cold, martensite nucleus Decline with temperature and gradually grow up, risen again after water outlet using waste heat, temperature rises, and martensite nucleus is again synchronous with temperature in turn Rising and reduce, i.e., refinement crystal grain improve steel obdurability.
2. the austenitizing of steel；
(1) quenching temperature of steel, soaking time and heating rate are austenite phase transformation completion, and austenite grain is not It must grow up, burn thoroughly, uniformly, expense is low, reduces the thermal stress of heating, and steel part section temperature distribution uniformity is made for quenching water cooling Prepare, reduces austenite and change start temperature As, improve Ms (martensite start) point Ms, reduce the temperature difference of As and Ms, be Martensite reverted austenite provides condition, to refine the obdurability that crystal grain improves steel；
(1) the quenching temperature EF of steel；
1) the steel quenching temperature EF of harden ability difference is determined by following principle:
1. Heat-Treatment of Steel degree-of-difficulty factor N >=30mm, quenching temperature EF are higher by 30 than the grade of steel quenching temperature DEG C~50 DEG C；
2. Heat-Treatment of Steel degree-of-difficulty factor N < 30mm, quenching temperature EF are higher by 20 than the grade of steel quenching temperature DEG C~40 DEG C；
2) the good steel quenching temperature EF of harden ability be it is 10 DEG C higher than the grade of steel quenching temperature~30 DEG C；
(2) the Holding Time at Austenitizing Temperature E of steel1F1；
The Holding Time at Austenitizing Temperature E of steel1F1, it is calculated as follows:
τAlways=Kz+Az × D × K
τ in formulaAlways--- the total time of steel Quench heating heat preservation, unit: min；
Kz --- steel Holding Time at Austenitizing Temperature radix, unit: min；
Az --- steel Holding Time at Austenitizing Temperature coefficient, unit: min/mm；
D --- workpiece effective thickness, unit: mm；
K --- workpiece shove charge correction factor；
(3) the Quench heating heating rate DE of steel is 150 DEG C~200 DEG C/h；
(2) quenching ladder preheating number, temperature, soaking time and the heating rate of steel are to burn thoroughly, uniformly, and expense is low, subtracts The thermal stress of small preheating, steel part section temperature distribution uniformity are prepared for quenching water cooling, are reduced austenite and are changed start temperature As improves Ms (martensite start) point Ms, reduces the temperature difference of As and Ms, provides condition for martensite reverted austenite, with refinement The obdurability of crystal grain raising steel；
(1) the quenching preheating of steel preheats AB and CD for ladder twice；
(2) quenching of steel ladder preheating temperature AB and CD twice are as follows:
1) when heating temperature EF is 800 DEG C, then the first ladder preheating temperature AB and the second ladder preheating temperature CD distinguishes For 400 DEG C and 600 DEG C；
2) when heating temperature EF is 950 DEG C, then the first ladder preheating temperature AB and the second ladder preheating temperature CD distinguishes For 500 DEG C and 700 DEG C；
3) when heating temperature EF is between 800 DEG C~950 DEG C, the first ladder preheating temperature AB and the second ladder preheating temperature Degree CD is calculated as follows respectively:
1. AB=aAB(X-800)+bAB
In formula: AB --- the practical preheating temperature of the first ladder, DEG C；
X --- practical heating temperature EF, DEG C, value range: 800≤X≤950；
aAB--- the ratio of the first ladder preheating temperature range AB and heating temperature range EF；
bAB——400℃；
2. CD=aCD(X-800)+bCD
In formula: CD --- the practical preheating temperature of the second ladder, DEG C；
X --- practical heating temperature EF, DEG C, value range: 800≤X≤950；
aCD--- the ratio of the second ladder preheating temperature range CD and heating temperature range EF；
bCD——600℃；
1. and 2. citing: when practical heating temperature X is 890 DEG C, substitutes into, obtain respectively:
(3) quenching of steel ladder preheating insulation time A twice1B1And C1D1；
Ladder preheating insulation time A twice1B1And C1D1, it is calculated as follows:
τ=Ay × D × K
τ in formula --- ladder preheating insulation time twice, unit: min；
Ay --- ladder preheating insulation time coefficient twice, unit: min/mm；
D --- workpiece effective thickness, unit: mm；
K --- workpiece shove charge correction factor；
Quenching (preheating) the soaking time radix Kz and soaking time coefficient Az, Ay of various steel are shown in Table 1；Workpiece shove charge amendment COEFFICIENT K is shown in Table 2；
Table 1: various steel quenching (preheating) soaking time radix Kz and soaking time coefficient Az, Ay value
2 Quench heating shove charge correction factor k of table
The effective thickness (D) of workpiece heating calculates as follows:
1. cylindrical body is using diameter as effective thickness；
2. square section is using side length as effective thickness；
3. rectangular section workpiece is using short side as effective thickness；
4. plate part, effective thickness is 1.5 times of maximum gauge；
5. thin-wall sleeve parts are using wall thickness as effective thickness；
Aperture is less than 50 millimeters, and aperture is less than outer diameterClass, then effective thickness is twice of wall thickness；
WhenIts effective thickness is calculated as follows:
D in formula --- workpiece effective thickness (mm)；
D0--- the unilateral actual (real) thickness of workpiece (mm)；
ΦIt is interior--- circular diameter (mm) in workpiece；
ΦOutside--- excircle of workpiece diameter (mm)；
Citing: workpiece OD440 × ID160 × L430mm
D0=(440-160) ÷ 2=140mm
6. cone workpiece is from small endThe diameter at place is as effective thickness；
It, can be based on the section thickness of working portion for cutter 7. complex-shaped part is calculated with maximum gauge It calculates.
(4) ladder pre-heating temperature elevation speed OA and BC is 100 DEG C~150 DEG C/h twice.
3. the pre-cooling of steel；
(1) it after steel austenitizing EF, comes out of the stove and FY is pre-chilled in air；This is because:
The thermal stress of steel is caused by the energy difference of steel cooling surface and cooling medium, and energy difference is big, and thermal stress is big, instead It, thermal stress is small, and in same cooling medium, the high thermal stress of steel cooling surface temperature is greater than the low heat of steel cooling surface temperature Stress；After steel austenitizing, temperature falls to precooling temperature after pre-cooling, and it is water-soluble to be transferred to 5%~10%NaCl of mass fraction immediately It is cooling in liquid, steel cooling surface energy is reduced, the energy difference of steel cooling surface and water cooling medium is reduced, is i.e. the heat of reduction steel is answered Power is conducive to reduce amount of distortion and tearing tendency；
(2) steel of different steel grades is cooled to the precooling temperature Tn of Y in advance are as follows:
(1) eutectoid steel and hypereutectoid steel are Ar1(10 DEG C~30 DEG C)；
This is because: the austenite of eutectoid steel and hypereutectoid steel is subcooled to slightly less than Ar1Following temperature, it is still more stable, There is cementite precipitation, hypereutectoid steel is in A1It more than temperature is pre-chilled and does not consume incubation period, martensite can be quenched to and analysed Strengthen out；
(2) sub-eutectoid steel precooling temperature Tn is Ac1+ (50 DEG C~80 DEG C), but must < Ac3；
This is because:
1) austenite of sub-eutectoid steel is subcooled to slightly less than Ar1Following temperature, it is still more stable, and in A1It is more than temperature pre- It is cold not consume incubation period, there is a small amount of ferrite to be precipitated, though it can be quenched to martensite, but the strong of reduction steel is precipitated in a small amount of ferrite Degree；
2) sub-eutectoid steel is in Ac1~Ac3Heating quenching is known as intercritical hardening, phase on intercritical hardening temperature departure between temperature Height Ac3Remoter, ferrite precipitation is more, and the strength reduction of steel is bigger, to reduce ferrite amount of precipitation, that is, reduces the intensity of steel Reduction amount, sub-eutectoid steel precooling temperature are close to upper transformation temperature Ac3Intercritical hardening temperature；
3) sub-eutectoid steel is close to upper transformation temperature Ac3The intercritical hardening of temperature, energy fining austenite grains improve the tough of steel Property, it concentrates on the objectionable impurities such as phosphorus in a small amount of free dispersion ferrite crystal grain, improves notch toughness, reduce cold short transformation temperature Degree reduces temper brittleness；
(3) the pre-cooling degree of steel is controlled；The pre-cooling of steel is insufficient, and reduction thermal stress is limited, and pre-cooling is exaggerated, and steel cannot quench It is more at martensite or ferrite amount of precipitation, the quality and technical index of quenching is not achieved, the pre-cooling degree to steel is needed to control, So that pre-cooling degree had not only been maximized reduction thermal stress, but will not steel cannot be quenched to martensite or ferrite amount of precipitation is more, and reach The desired temperature of pre-cooling, it is up to standard to obtain consistent intended tissue and performance；
(1) the precooling temperature Tn of eutectoid steel and hypereutectoid steel is Ar1(10 DEG C~30 DEG C)；
Citing: T10 steel Ar1Temperature is 700 DEG C,
Then Tn=Ar1(10~30)=700-10~700-30=690~670
T10 steel precooling temperature value range is 670 DEG C≤Tn≤690 DEG C；
(2) the precooling temperature Tn of sub-eutectoid steel is Ac1+ (50 DEG C~80 DEG C), but must < Ac3；
Citing: 20Cr steel Ac1Temperature is 766 DEG C, Ac3Temperature is 838 DEG C；
Then Tn=Ac1+ (50~80)=766+50~766+80=816~846
Ac3=838 DEG C, 20Cr steel precooling temperature value range is 838 DEG C of 816 DEG C≤Tn <；
(4) pre-cooling of steel is precooling temperature Tn, is transferred to cooling in mass fraction 5%~10%NaCl aqueous solution immediately, prevents Only pre-cooling is insufficient or exaggerates；
(5) compared with prior art, the beneficial effect of forecooling method of the present invention is:
(1) after the prior art is steel austenitizing:
1) it is pre-chilled in heating furnace, eutectoid steel and hypereutectoid steel are transferred to and are heated to Ar1It is pre- in (10 DEG C~30 DEG C) temperature furnace It is cooled to Ar1- (10 DEG C~30 DEG C) temperature, sub-eutectoid steel is cooled to intercritical hardening temperature in advance in former heating furnace；It is transferred to single medium again Middle cooling consumes the energy and resource, improves heat treatment cost, pollutes environment；
2) it is pre-chilled in the oil, is transferred to oil cold several seconds, play pre-cooling, then be transferred in water cooling, raising heat treatment cost, Pollute environment；
(2) after the present invention is steel austenitizing, eutectoid steel and hypereutectoid steel are cooled to Ar in advance in air1(10 DEG C~30 DEG C) temperature, sub-eutectoid steel is cooled to Ac in advance in air1+ (50 DEG C~80 DEG C), but must < Ac3, and close to upper transformation temperature Ac3Temperature Degree；Being transferred to cooling, energy saving and resource in mass fraction 5%~10%NaCl aqueous solution immediately reduces cost, protection ring Border reaches the desired temperature of pre-cooling, up to standard to obtain consistent intended tissue and performance.
4. the control of steel is cold；
(1) the cooling process after steel pre-cooling is designed, controls steel in mass fraction 5%~10%NaCl aqueous solution In cooling degree, it is cooling around C- curve range of instability --- nose portion temperature to martensite to control steel surface layer certain depth Change start temperature Ms or less and not cold degree, i.e. control martensite transfor mation amount, and reach each critical point desired temperature, obtains It obtains consistent intended tissue and performance is up to standard；See Fig. 2；
(2) it after steel austenitizing EF, is pre-chilled after FY and cools down YG for the first time in mass fraction 5%~10%NaCl aqueous solution Around C- curve range of instability --- the nose portion temperature degree not cold to martensitic regions, i.e., water cooling time Y for the first time1G1Are as follows: Water outlet for the first time is Bs+ (50 DEG C~100 DEG C) using waste heat tempering temperature H, but must be lower than perlitic transformation temperature；
(1) the time Y of water cooling for the first time of steel1G1It is calculated by right formula: T=a × N
The water cooling time (min) of T in formula --- steel；
N --- Heat-Treatment of Steel degree-of-difficulty factor (mm)；
The cooling ratio (min/mm) of a --- steel；
1) Heat-Treatment of Steel degree-of-difficulty factor N >=30mm, carbon steel a value take 0.05~0.09min/mm, and steel alloy a value takes 0.02~0.06min/mm；
2) Heat-Treatment of Steel degree-of-difficulty factor N < 30mm, carbon steel a value take 0.08~0.20min/mm, and steel alloy a value takes 0.02~0.15min/mm；
Coefficient a is with the content of NaCl in the temperature of water, water, the cycling condition of water, the chemical analysis of steel, the temperature of steel and pre- Cold degree and steel, which enter water mode etc., to be influenced and changes；
Influence of the various factors to the practical water cooling time, seeming a value is a Protean variable, and cooling time can not It determines；Actually this is not so, although the quenching environment of each manufacturer is different, cooling ratio a value is different, each factory There are the production environment and stable technical process of oneself in family, needs to control each main influence factor, makes it stable, at this moment A value almost without what variation, be a constant；Rule can also be found out even if changing, as water temperature influence with The variation in season and change, with steel in water cool down frequency variation and change, change size with the thermal capacity size of water and Variation etc.；As long as first calculating Heat-Treatment of Steel degree-of-difficulty factor N, accumulation steel quenching when objective environment condition all data and The water cooling time of optimum efficiency；These data are substituted into model formation: T=a × N, i.e. a=T/N；It can calculate and be suitble to this The cooling ratio a value that factory uses；
(2) H of tempering temperature for the first time of steel is Bs+ (50 DEG C~100 DEG C), but must be lower than perlitic transformation temperature, i.e. C- is bent Line nose portion temperature --- Tp；
1) illustrate: 65Mn steel Bs is 400 DEG C, and Tp is 480 DEG C, and tempering temperature H is；
H=Bs+ (50~100)=400+50~400+100=450~500
Tp is 480 DEG C, 65Mn steel tempering temperature value range are as follows: 480 DEG C of 450 DEG C≤H <；
2) H of tempering temperature for the first time of steel is determined by following principle:
1. Heat-Treatment of Steel degree-of-difficulty factor N >=30mm, tempering temperature H capping；
2. Heat-Treatment of Steel degree-of-difficulty factor N < 30mm, tempering temperature H are removed the limit；
This is because Heat-Treatment of Steel degree-of-difficulty factor is big, section is also big, conversely, the section of steel is small；It is heat-treated degree-of-difficulty factor N >=30mm, tempering temperature H capping increase the energy difference of steel cooling surface and water cooling medium, improve specific heat processing difficulty system The cooling velocity of number N < 30mm bigger water cooling again is equivalent to reduction heat treatment degree-of-difficulty factor N；
(3) H of tempering temperature for the first time of steel is Bs+ (50 DEG C~100 DEG C), but must be lower than perlitic transformation temperature, is turned immediately Enter and cool down HJ in mass fraction 5%~10%NaCl aqueous solution again, prevents pearlite and Upper Bainite Transformation；This be by In:
(1) perlitic transformation occurs for overcooling austenite, and the quality and technical index of steel cannot be up to standard；
(2) Upper Bainite Transformation occurs for overcooling austenite, and upper bainite is due to being distributed with coarse brittleness carbonization between lath Object is the adverse tissue in steel, endangers the toughness of steel, it is necessary to avoid；
(4) steel cools down the HJ journey not cold to martensitic regions again in mass fraction 5%~10%NaCl aqueous solution Degree, i.e., water cooling time H again2J2Are as follows: it is discharged again cold together under the quenching that the temperature K for being risen again using waste heat and stopping rising is steel But start temperature；
(1) the time H of water cooling again of steel2J2It is determined by following principle:
1) Heat-Treatment of Steel degree-of-difficulty factor N >=30mm, again water cooling time H2J2For water cooling time Y for the first time1G150%~ 80%；
2) Heat-Treatment of Steel degree-of-difficulty factor N < 30mm, again water cooling time H2J2For water cooling time Y for the first time1G140%~ 70%；
(2) the temperature K for stopping rising that rises again again of steel, according to different steel grades and different process for quenching under the quenching of steel Cooling start temperature together --- Ms (martensite start) point Ms is on the upper side or temperature on the lower side；
(5) compared with prior art, the present invention is removed with " invertibity of martensite transfor mation " rule, uses heat treatment method Crystal grain is refined to improve outside the obdurability beneficial effect of steel, further includes:
(1) harden ability of steel is improved；
1) it is the alloying element that sufficient amount is added in steel and stablizes overcooling austenite that the prior art, which improves the harden ability of steel, is changed Become C- curve shape and elapse C- curve to the right, reduces critical quenching rate to realize and improve quenching cooling velocity, to mention The harden ability of Gao Gang consumes alloy resource, improves the cost and carbon equivalent of steel, reduce the welding performance of steel；
2) heat treatment method of the invention, after steel austenitizing, in mass fraction 5%~10%NaCl aqueous solution after pre-cooling In it is cooling for the first time not cold around C- curve range of instability to martensitic regions, be discharged risen again using waste heat to bainite turn for the first time Become start temperature Bs+ (50 DEG C~100 DEG C), but perlitic transformation temperature must be lower than, is transferred to mass fraction 5%~10% immediately Martensitic regions are cooled to again in NaCl aqueous solution and not cold, being discharged the temperature risen again using waste heat and stop rising again is steel Quenching under cooling start temperature together --- Ms (martensite start) point Ms is on the upper side or temperature on the lower side, improves the cooling table of steel Face energy increases the energy difference of steel cooling surface and cooling medium, the cooling velocity of water cooling and third time again is improved, to mention The harden ability of Gao Gang；Replace low alloying with microalloying in steel, with low alloying replace in alloying, alloying replaces in Part high-alloying saves alloy resource, reduces the cost and carbon equivalent of steel, improve the welding performance of steel；This is because:
1. the cooling velocity of steel is caused by the energy difference of steel cooling surface and cooling medium, the big cooling velocity of energy difference Greatly, conversely, cooling velocity is small, so the high cooling velocity of steel cooling surface temperature is cooling greater than steel in same cooling medium The low cooling velocity of surface temperature；
2. being the variation that high-energy is shifted to low-energy state inside substance, cooling is the high-energy of steel to low to steel in water The process of the water transfer of energy；
After steel austenitizing, cooling in water after pre-cooling cooling velocity constantly decays to a certain extent, tends towards stability, locates In a kind of sub- equilibrium state；It is the high-energy of steel cooling surface because the energy difference of steel cooling surface and water cooling medium becomes smaller The high-energy for relying solely on center portion passes over, and the cooling velocity of steel is restricted just because of this mechanism, to restrict quenching for steel Permeability；Like water-power plant, barrage is built, the potential energy of water is improved, that is, increases the energy of water, then open a sluice gate to generate electricity, the gesture of water Kinetic energy can be changed into, flow velocity is accelerated；
(2) the effective thickness scope of application of steel；
1) alloy that sufficient amount stablizes overcooling austenite is added in the isothermal hardening of prior art steel, big section steel part in steel Element changes C- curve shape and elapses C- curve to the right, reduces critical quenching rate to realize the harden ability for improving steel, steel It can be directly cooled to a little higher than Ms (martensite start) point Ms progress isothermal heat preservation in the melting salt bath or hot oil slot of temperature control, Since melting salt bath or hot oil temperature are higher, cooling capacity is weak, has certain limitations to steel part effective thickness, can only be applicable in Thickness is imitated compared with small steel piece, otherwise, at 1/2T from High-temperature cooling into Lower Bainite Transformation temperature course, is sent out because cooling velocity is low Raw pearlite and Upper Bainite Transformation, are not achieved quality and technical index；See Fig. 3；
2) isothermal hardening of steel of the present invention, after steel austenitizing, twice in mass fraction 5%~10%NaCl water after pre-cooling Cooling not cold around C- curve range of instability to martensitic regions in solution, water outlet is risen again using waste heat to a little higher than martensite Change start temperature Ms and carry out isothermal holding, water cooling speed again is improved, to improve the harden ability of steel；The effective thickness of steel is suitable It is wide with range, it avoids that overcooling austenite occurs into Lower Bainite Transformation temperature course from High-temperature cooling at big section steel part 1/2T To pearlite and Upper Bainite Transformation, keep quality and technical index up to standard；See Fig. 4；
3) alloy that sufficient amount stablizes overcooling austenite is added in the grade quench of prior art steel, big section steel part in steel Element changes C- curve shape and elapses C- curve to the right, reduces critical quenching rate to realize the harden ability for improving steel, steel Ms (martensite start) point Ms is on the upper side or carry out isothermal on the lower side can directly be cooled in the melting salt bath or hot oil slot of temperature control Heat preservation, since melting salt bath or hot oil temperature are higher, cooling capacity is weak, has certain limitations to steel part effective thickness, can only Effective thickness is applicable in compared with small steel piece, otherwise, is changed because of the low generation overcooling austenite of cooling velocity to non-martensite at 1/2T, quality Technical indicator cannot be up to standard；See Fig. 5；
4) grade quench of steel of the present invention, after steel austenitizing, twice in mass fraction 5%~10%NaCl water after pre-cooling Cooling not cold around C- curve range of instability to martensitic regions in solution, water outlet, which is risen again using waste heat to martensite transfor mation, opens Beginning temperature Ms is on the upper side or progress isothermal holding on the lower side, water cooling speed again is improved, to improve the harden ability of steel；Effective thickness of steel It is wide to spend the scope of application, avoids that supercooling Ovshinsky occurs at big section steel part 1/2T from during High-temperature cooling to martensite transformation temperature Body changes to non-martensite, keeps quality and technical index up to standard；See Fig. 6；
5) alloy that sufficient amount stablizes overcooling austenite is added in the water hardening of prior art steel, big section steel part in steel Element changes C- curve shape and elapses C- curve to the right, and reduction critical quenching rate improves the harden ability of steel to realize, by The harden ability of steel limits, and steel is cold in water, and amount of distortion is big, or even cracking；It is not cold, quality and technical index is quenched not at 1/2T Can be up to standard, cause " dilemma of dual hypothesis "；
6) single medium water hardening of steel of the present invention, after steel austenitizing, twice in mass fraction 5%~10% after pre-cooling Cooling not cold around C- curve range of instability to martensitic regions in NaCl aqueous solution, water outlet is risen again using waste heat to continuation water Cold start temperature, both eliminates structural stress and thermal stress, reduces amount of distortion and tearing tendency, but improve again with third time water Speed of cooling, to improve the harden ability of steel；The effective thickness scope of application of steel is wide, avoids cold from high temperature at big section steel part 1/2T But change to generation overcooling austenite during martensite transformation temperature to non-martensite, reach the quality and technical index of quenching Mark；See Fig. 7；
7) conjunction that sufficient amount stablizes overcooling austenite is added in the interrupted quenching of prior art steel, big section steel part in steel Gold element changes C- curve shape and elapses C- curve to the right, and reduction critical quenching rate improves the harden ability of steel to realize, Steel is not cold with respect to cooling in strong medium in cooling capacity, be transferred in the relatively weak medium of cooling capacity it is cooling, reduce amount of distortion with Tearing tendency occurs overcooling austenite since cooling capacity is relatively weak, at big section steel part 1/2T and changes to non-martensite, up to not To the quality and technical index of quenching；
8) interrupted quenching of steel of the present invention, after steel austenitizing, twice in 5%~10%NaCl of mass fraction after pre-cooling Cooling not cold around C- curve range of instability to martensitic regions in aqueous solution, water outlet is risen again using waste heat in cooling capacity Cooling start temperature in relatively weak medium not only reduces amount of distortion and tearing tendency, but also improves water cooling again and in cooling capacity Cooling velocity in relatively weak medium, to improve the harden ability of steel；The effective thickness scope of application of steel is wide, avoids big section steel Overcooling austenite occurs at part 1/2T from during High-temperature cooling to martensite transformation temperature to change to non-martensite, makes quenching Quality and technical index is up to standard；See Fig. 8；
(3) the surface layer overcooling austenite of steel is partially converted to martensite in martensitic regions in advance, and catalysis isothermal keeps bayesian The speed of body transformation；
1) it after the prior art is steel austenitizing, is directly cooled in the melting salt bath or hot oil slot of energy temperature control a little higher than Ms (martensite start) point Ms temperature carries out isothermal heat preservation, and overcooling austenite cannot be transformed into martensite, that is, geneva is not present Body tissue cannot be catalyzed bainite transformation and quickly carry out, not can be shortened bainite transformation incubation period, cannot make to change period contracting It is short, isothermal soaking time be bainite transformation start and end of a period line the time required to 100%, see that Fig. 3, process cycle are long；
2) it after the present invention is steel austenitizing, is cooled down for the first time in mass fraction 5%~10%NaCl aqueous solution after pre-cooling Around C- curve range of instability --- nose portion temperature to martensitic regions and it is not cold, be discharged risen again using waste heat to bayesian for the first time Body change start temperature Bs+ (50 DEG C~100 DEG C), but must be lower than perlitic transformation temperature, be transferred to immediately mass fraction 5%~ Martensitic regions are cooled to again in 10%NaCl aqueous solution and not cold, be discharged risen again the temperature for stopping rising using waste heat again Enter in slow cooling box for steel and carries out the isothermal start temperature that noenergy supplements isothermal holding, steel surface layer overcooling austenite using waste heat It is partially converted to martensite in martensitic regions in advance twice, catalysis isothermal keeps bainite transformation quickly to carry out；
1. shorten bainite transformation incubation period, shorten transformation the period, isothermal time shorten to bainite transformation start and eventually 50%~70% the time required to line, see Fig. 4, shortens process cycle；
2. shorten bainite transformation incubation period since the isothermal of martensite catalysis steel keeps bainite transformation quickly to carry out, To make bainite transformation cycle time, enters in slow cooling box for steel and kept using the isothermal that waste heat carries out noenergy supplement, section The about energy and resource, reduction heat treatment cost, protection environment, cool down in the isothermal time of shortening and open not less than martensite transfor mation Beginning temperature Ms temperature is shown in Fig. 4, prevents overcooling austenite that martensite transfor mation occurs and bainite transformation occurs, and obtains lower bainite Tissue, provides technical support；This is because:
(i) overcooling austenite occurs bainite transformation and changes small, reduction structural stress than the specific volume of martensite transfor mation, thus Reduce amount of distortion and tearing tendency；
(ii) lower bainite not only improves intensity, but also more significant than the toughness of martensite and plasticity raising；
(4) the surface layer overcooling austenite of steel carries out self tempering in the martensite of martensitic regions portions turn in advance twice；
1) reduce amount of distortion and the tearing tendency of steel；
1. making the martensite transfor mation of preparatory portions turn at tempered martensite, structural stress is eliminated；
2. eliminating cooling initial stage causes drawing stress on surface, the thermal stress of center portion compression；
3. being equal to the quick self tempering of high temperature, temper brittleness is avoided；This is because high temperature and fast temper does not generate Temper brittleness Property；
4. reducing the temperature difference when continuing cooling in table, i.e. reduction thermal stress；
5. cooling velocity is improved due to rising again again:
(i) reduce the temperature difference in table, i.e. reduction thermal stress；
(ii) shorten the time difference of table organization transformation, i.e. reduction structural stress；
2) for steel, water cooling increases Cooling Austenite Transformation amount again, reduces remained austenite content, improves quenching degree completely and mentions For condition；This is because Cooling Austenite Transformation is that volume expansion occurs for martensite, the overcooling austenite not yet changed is by week The additonal pressure for enclosing martensite, loses the condition of growing up and remains；According to newton " active force and reaction force " theorem, twice Rising again makes overcooling austenite carry out self tempering in the martensite of martensitic regions portions turn in advance, is tempering horse by martensite transfor mation Volume contraction occurs for family name's body, reduces the overcooling austenite that not yet changes by the additonal pressure of tempered martensite around, to provide The condition of growing up is changed.
5. the isothermal hardening (as shown in Figure 4) of steel is；
(1) steel be discharged again using waste heat rise again to K stop rise temperature be steel enter in slow cooling box using waste heat into Row noenergy supplements the isothermal start temperature that isothermal keeps KL；
(2) the isothermal start temperature K of steel is Ms+ (20 DEG C~50 DEG C)；This is because:
(1) steel be discharged again using waste heat rise again to K stop rise temperature be steel enter in slow cooling box using waste heat into Row noenergy supplements the beginning that isothermal keeps KL, offsets steel and is protected in slow cooling box using the isothermal that waste heat carries out noenergy supplement It holds, there is the cooling of a small amount of heat loss and slowly successively decreasing for isothermal temperature；
(2) steel is kept and in melting salt bath or hot oil slot in slow cooling box using the isothermal that waste heat carries out noenergy supplement It carries out keeping the temperature temperature difference with the presence of the isothermal of energy supplement, steel carries out noenergy supplement isothermal using waste heat in slow cooling box and keeps Isothermal start temperature determination, by melting salt bath or hot oil slot isothermal keep the temperature isothermal temperature add the temperature difference；Make The isothermal temperature that steel carries out noenergy supplement isothermal holding using waste heat in slow cooling box cools down in isothermal time and is not less than horse Family name's body changes start temperature Ms, sees Fig. 4, prevents overcooling austenite that martensite transfor mation occurs and bainite transformation occurs, under acquisition Bainite structure；
(3) temperature of the isothermal start temperature K of steel is Ms+ (20 DEG C~50 DEG C)；
K=Ms+ (20 DEG C~50 DEG C)
1) illustrate: 65Mn steel Ms is 254 DEG C,
Then K=Ms+ (20~50)=254+20~254+50=274~304
65Mn steel isothermal start temperature value range are as follows: 274 DEG C≤K≤304 DEG C；
2) the isothermal start temperature K of steel is determined by following principle:
1. Heat-Treatment of Steel degree-of-difficulty factor N >=30mm, isothermal start temperature K is removed the limit；
2. Heat-Treatment of Steel degree-of-difficulty factor N < 30mm, isothermal start temperature K capping；
This is because Heat-Treatment of Steel degree-of-difficulty factor is big, thermal capacity is big, conversely, thermal capacity is small；
(3) steel is isothermal start temperature K, is transferred in slow cooling box and is protected using the isothermal that waste heat carries out noenergy supplement immediately KL is held, heat is prevented to scatter and disappear outside slow cooling box, saves the isothermal holding that waste heat carries out noenergy supplement；
(1) energy saving and resource；
1) prior art steel is directly cooled to a little higher than martensite transfor mation in the melting salt bath or hot oil slot of energy temperature control and opens The isothermal temperature of beginning temperature Ms temperature have the isothermal of energy supplement to keep the temperature, and consumes the energy and resource, increase are heat-treated to This, pollutes environment；
2) steel of the present invention is not cooling cold around C- curve range of instability to martensitic regions in water twice, is discharged again The temperature for stopping rising of being risen again using waste heat is isothermal start temperature, is transferred in slow cooling box immediately and carries out noenergy benefit using waste heat The isothermal filled is kept, and energy saving and resource reduces heat treatment cost, protection environment；
(2) cooling and isothermal medium used in；
1) cooling used in the melting salt bath or hot oil slot of prior art energy temperature control and isothermal medium is melting salt bath or hot oil, Melting salt bath or hot oil are at high cost, and when use needs to be heated to the isothermal temperature of a little higher than Ms (martensite start) point Ms, by In temperature height, therefore cooling capacity is weak, and pollution is big, is easy kindling and splashing is hurted sb.'s feelings, dangerous, there are aging phenomena, use one After fixing time, it is necessary to more renew；
2) cooling and isothermal medium used in the present invention is water and air, and water and air is at low cost, easy to use, the cooling of water Ability is strong, cleanliness without any pollution, protect environment, safety it is not on fire, without aging phenomenon, clean cooling water be with it is more long more It is good, it is strided forward to " with water generation oil " clean heat treatment of real meaning, opens up the new way " with water generation oil "；
(3) process merges；
1) prior art steel can carry out the heat preservation of energy supplement isothermal in the melting salt bath or hot oil slot of temperature control, there is only Single isothermal transformation [it is a Ms line horizontal line on the upper side, (see Fig. 3) that isothermal, which keeps the temperature line segment ,], improves austenite thermostabilization journey Degree；
2) steel of the present invention is kept in slow cooling box using the isothermal that waste heat carries out noenergy supplement, there is a small amount of heat loss Cooling and the slow of isothermal temperature successively decrease, and cooling velocity is slow, overcooling austenite continuous coo1ing is not terminated, by continuous coo1ing work Sequence, which merges, keeps in process [it is a Ms line oblique line on the upper side, (see Fig. 4) that isothermal, which keeps line segment ,] in isothermal；Isothermal holding was both wrapped Isothermal transformation is included, and including continuous cooling transformation；
1. isothermal transformation makes overcooling austenite that bainite transformation occur, lower bainite tissue is obtained；
2. continuous cooling transformation:
(i) austenite thermostabilization degree is reduced, cold treatment and tempering difficulty are reduced；
(ii) increase Cooling Austenite Transformation amount, reduce remained austenite content, improve quenching completely degree, make steel intensity and Hardness improves, and the fracture appearance transition tem of steel reduces, and dimensional stability increases；
This is because overcooling austenite stops cooling and keeps certain time, retained austenite is retained the temperature is more Come, and the retention time is long, the overcooling austenite not changed becomes more stable；Overcooling austenite is to martensite when being further continued for cooling Transformation is not immediately begun to, but through that could restore to change after a period of time, transformation will carry out at lower temperatures, and change The transformation amount of continuous coo1ing is also not achieved in amount；
(4) performance requirement of slow cooling box；
(1) good heat insulating of slow cooling box reduces heat loss, saves the isothermal holding that waste heat carries out noenergy supplement；
(2) steel enters is automatically closed slow cooling tank inlet immediately after slow cooling box, scattered and disappeared with reducing heat from inlet, more than preservation The isothermal that heat carries out noenergy supplement is kept, and after pouring out hot water like vacuum flask, plug for vacuum bottle is covered bottleneck immediately, to reduce Heat scatters and disappears from bottle mouth position；
(5) the isothermal time K of steel1L1；
(1) steel is isothermal start temperature K, is transferred in slow cooling box and is kept using the isothermal that waste heat carries out noenergy supplement immediately KL starts to calculate isothermal time K1L1；
(2) the isothermal time K of steel1L1For bainite transformation start and end of a period line the time required to 50%~70%；This be by It is cooling in water twice after pre-cooling to bypass C- curve range of instability --- nose portion temperature to martensitic regions after steel austenitizing And it is not cold, surface layer overcooling austenite is partially converted to martensite in martensitic regions in advance, and catalysis isothermal keeps bainite transformation It quickly carries out, shortens bainite transformation incubation period, make bainite transformation cycle time；
(6) after steel isothermal keeps KL, the cooling LM of slow cooling box L out；
(1) after the heat preservation of prior art steel isothermal, melting salt bath or hot oil slot are air-cooled to room temperature out, improve austenite thermostabilization Change degree improves cold treatment and tempering difficulty；
(2) after steel isothermal of the present invention keeps KL, slow cooling box L, is transferred to mass fraction 5%~10%NaCl aqueous solution immediately out In be discontinuously cooled to room temperature；
1) after steel isothermal keeps KL, slow cooling box L, is transferred to third in mass fraction 5%~10%NaCl aqueous solution immediately out Secondary cooling LM and it is not cold；
2) water outlet of steel third time is risen again using waste heat stops the temperature rising to N as in 5%~10%NaCl of mass fraction 4th cooling start temperature in aqueous solution；
3) the start temperature N of the 4th water cooling of steel of different steel grades are as follows:
1. middle and high carbon medium alloy steel is 110 DEG C~140 DEG C；
2. high-carbon steel and middle and high carbon low alloy steel are 90 DEG C~120 DEG C；
3. medium and low carbon steel and low-carbon low-alloy steel are 70 DEG C~100 DEG C；
4) steel is the start temperature N of the 4th water cooling, is transferred to the 4th in mass fraction 5%~10%NaCl aqueous solution immediately Secondary cooling NP is to room temperature；
(3) after steel isothermal keeps KL, the interrupted water cooling of slow cooling box L to room temperature out, with refine crystal grain improve steel obdurability and Austenite thermostabilization degree is reduced, cold treatment and tempering difficulty are reduced；This is because:
1) with " invertibity of martensite transfor mation " rule, crystal grain is refined with heat treatment method, to improve the tough of steel Property；
2) the austenite thermostabilization degree of steel and residence time at a certain temperature are long, austenite thermostabilization degree Greatly, to shorten the residence time at a certain temperature, interrupted water cooling to room temperature is dropped immediately with reducing austenite thermostabilization degree Low cold treatment and tempering difficulty；
(7) the interrupted water cooling of steel is transferred to down one of heat treatment procedure to room temperature immediately；This is because the Ovshinsky body heat of steel is steady Surely changing degree, the residence time is long at a certain temperature, and austenite thermostabilization degree is big, to shorten stop at a certain temperature Time reduces cold treatment and tempering difficulty to reduce austenite thermostabilization degree；
6. the grade quench (as shown in Figure 6) of steel is；
(1) steel is discharged again rises again that stop the temperature rising to K be that steel enters and stands in air using waste heat using waste heat Carry out the classification start temperature that noenergy supplement isothermal is kept；
(2) the classification start temperature K of the steel of different steel grades are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
K=Ms+ (40 DEG C~60 DEG C),
Citing: 5CrNiMo steel Ms is 230 DEG C,
Then K=Ms+ (40~60)=230+40~230+60=270~290
5CrNiMo steel is classified start temperature value range are as follows: 270 DEG C≤K≤290 DEG C；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
K=Ms+ (20 DEG C~40 DEG C),
Citing: GCr15 steel Ms is 240 DEG C,
Then K=Ms+ (20~40)=240+20~230+40=260~280
GCr15 steel is classified start temperature value range are as follows: 260 DEG C≤K≤280 DEG C
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
K=Ms- (80 DEG C~120 DEG C),
Citing: 45 steel Ms are 350 DEG C,
Then K=Ms- (80~120)=350-80~350-120=270~230
45 steel are classified start temperature value range are as follows: 230 DEG C≤K≤270 DEG C
(4) the classification start temperature K of steel is determined by following principle:
1) Heat-Treatment of Steel degree-of-difficulty factor N >=30mm, classification start temperature K are removed the limit；
2) Heat-Treatment of Steel degree-of-difficulty factor N < 30mm is classified start temperature K capping；
This is because Heat-Treatment of Steel degree-of-difficulty factor is big, thermal capacity is big, conversely, thermal capacity is small；
(5) K is the classification start temperature of steel, this is because:
1) steel be discharged again using waste heat rise again to K stop rise temperature be steel enter stand air in using heat treatment Waste heat carries out the beginning that noenergy supplement isothermal keeps KL, offsets steel and carries out noenergy supplement using waste heat in standing air Isothermal is kept, and has the cooling of heat loss and isothermal to keep successively decreasing for temperature；
2) steel is kept and using the isothermal that waste heat carries out noenergy supplement in melting salt bath or hot oil slot in standing air Middle to carry out keeping the temperature temperature difference with the presence of the isothermal of energy supplement, steel carries out noenergy using waste heat in standing air and supplements isothermal The determination of the classification start temperature of holding adds the temperature by the hierarchical temperature that isothermal is kept the temperature in melting salt bath or hot oil slot Difference；The hierarchical temperature for making steel carry out noenergy supplement isothermal holding using waste heat in standing air cools down in grading time Not less than the hierarchical temperature that technique requires, maximizes the thermal stress in cooling procedure and reduce, to significantly reduce amount of distortion And tearing tendency, and the final performance of steel is not influenced；
(3) steel is classification start temperature K, is transferred to the isothermal for standing and carrying out noenergy supplement in air using waste heat immediately KL is kept, heat is reduced and scatters and disappears in air, saves the isothermal holding that waste heat carries out noenergy supplement；
(1) energy saving and resource；
1) prior art steel can directly be cooled to Ms (martensite start) point in the melting salt bath or hot oil slot of temperature control Hierarchical temperature Ms on the upper side or on the lower side have the isothermal of energy supplement to keep the temperature, and consumes the energy and resource, increase are heat-treated to This, pollutes environment；
2) steel of the present invention is not cooling cold around C- curve range of instability to martensitic regions in water twice, utilizes waste heat The temperature for stopping rising of rising again is Ms (martensite start) point Ms classification start temperature on the upper side or on the lower side, is transferred to standing immediately It is kept in air using the isothermal that waste heat carries out noenergy supplement, energy saving and resource reduces heat treatment cost, protection ring Border；
(2) cooling and isothermal medium used in；
1) cooling used in the melting salt bath or hot oil slot of prior art energy temperature control and isothermal medium is melting salt bath or hot oil, Melting salt bath or hot oil are at high cost, and when use needs to be heated to Ms (martensite start) point Ms classification temperature on the upper side or on the lower side Degree, due to temperature height, cooling capacity is weak, and pollution is big, is easy kindling and splashing is hurted sb.'s feelings, dangerous, there are aging phenomena, make With after a certain period of time, it is necessary to more renew；
2) cooling and isothermal medium used in the present invention is water and air, and water and air is at low cost, easy to use, the cooling of water Ability is strong, cleanliness without any pollution, protect environment, safety it is not on fire, without aging phenomenon, clean cooling water be with it is more long more It is good, it is strided forward to " with water generation oil " clean heat treatment of real meaning, opens up the new way " with water generation oil "；
(3) process merges；
1) prior art steel can carry out the heat preservation of energy supplement isothermal in the melting salt bath or hot oil slot of temperature control, there is only Single isothermal heat preservation [it is a Ms line horizontal line on the upper side or on the lower side, (see Fig. 5) that isothermal, which keeps the temperature line segment ,], it is steady to increase Ovshinsky body heat Surely change degree；
2) steel of the present invention is kept in standing air using the isothermal that heat treatment waste heat carries out noenergy supplement, has heat to dissipate The cooling of mistake and isothermal keep successively decreasing for temperature, and cooling velocity is slow, overcooling austenite continuous coo1ing are not terminated, by continuous coo1ing Process, which merges, keeps in process [it is a Ms line oblique line on the upper side or on the lower side, (see Fig. 6) that isothermal, which keeps line segment ,] in isothermal；Isothermal It keeps not only including isothermal holding, but also including continuous coo1ing；
1. isothermal holding plays samming, reduce the thermal stress in cooling procedure, to reduce amount of distortion and cracking Tendency；
2. continuous coo1ing:
(i) austenite thermostabilization degree is reduced, cold treatment and tempering difficulty are reduced；
(ii) increase Cooling Austenite Transformation amount, reduce remained austenite content, improve quenching completely degree, make steel intensity and Hardness improves, and the fracture appearance transition tem of steel reduces, i.e., the toughness of steel increases, and the dimensional stability of steel increases；
It is being remained in the temperature, do not change this is because overcooling austenite stops cooling and keeps certain time Overcooling austenite becomes more stable；Overcooling austenite is not immediately begun to martensite transfor mation when being further continued for cooling, but is passed through It could restore to change after a period of time, transformation will carry out at lower temperatures, and turning for continuous coo1ing is also not achieved in transformation amount Variable；
(4) the grading time K of steel1L1；
(1) steel is classification start temperature, is transferred in standing air immediately and heat treatment waste heat is utilized to carry out noenergy supplement Isothermal keeps KL, starts to calculate grading time K1L1；
(2) the grading time K of steel1L1For (90~120) s；This is because:
1) grading time of steel is short, and the effect of samming is limited, reduces the thermal stress in cooling procedure limited, to reduce Amount of distortion and tearing tendency are limited；
2) grading time of steel grows the final performance that non-martensite transformation occurs during isothermal is kept and influences steel；
(5) after steel isothermal keeps KL, the cooling LM of air L is stood out；
(1) go out melting salt bath after the heat preservation of prior art steel isothermal or hot oil slot is air-cooled to room temperature, cause austenite thermostabilization Change degree improves, and cold treatment and tempering difficulty increase；
(2) after steel isothermal of the present invention keeps KL, air L is stood out, it is water-soluble to be transferred to 5%~10%NaCl of mass fraction immediately It is discontinuously cooled to room temperature in liquid；
1) after steel isothermal keeps KL, air L is stood out, is transferred in mass fraction 5%~10%NaCl aqueous solution the immediately Three times cool down LM and it is not cold；
2) water outlet of steel third time is risen again using waste heat stops the temperature rising to N as in 5%~10%NaCl of mass fraction The start temperature of 4th cooling NP in aqueous solution；
3) the start temperature N of the 4th water cooling of steel of different steel grades are as follows:
1. middle and high carbon medium alloy steel is 110 DEG C~140 DEG C；
2. high-carbon steel and middle and high carbon low alloy steel are 90 DEG C~120 DEG C；
3. medium and low carbon steel and low-carbon low-alloy steel are 70 DEG C~100 DEG C；
4) steel is the start temperature N of the 4th water cooling, is transferred to the 4th in mass fraction 5%~10%NaCl aqueous solution immediately Secondary cooling NP is to room temperature；
(3) after steel isothermal keeps KL, the interrupted water cooling of air L is stood out to room temperature, to refine the obdurability that crystal grain improves steel With reduction austenite thermostabilization degree, cold treatment and tempering difficulty are reduced；This is because:
1) with " invertibity of martensite transfor mation " rule, crystal grain is refined with heat treatment method, to improve the tough of steel Property；
2) the austenite thermostabilization degree of steel and residence time at a certain temperature are long, austenite thermostabilization degree Greatly, to shorten the residence time at a certain temperature, interrupted water cooling to room temperature is dropped immediately with reducing austenite thermostabilization degree Low cold treatment and tempering difficulty；
(7) the interrupted water cooling of steel is transferred to down one of heat treatment procedure to room temperature immediately；This is because the Ovshinsky body heat of steel is steady Surely changing degree, the residence time is long at a certain temperature, and austenite thermostabilization degree is big, to shorten stop at a certain temperature Time reduces cold treatment and tempering difficulty to reduce austenite thermostabilization degree.
7. single medium water hardening (as shown in Figure 7) of steel are as follows:
(1) steel be discharged again using waste heat rise again to K stop rise temperature be steel single medium quenching in mass fraction Continue cooling start temperature in 5%~10%NaCl aqueous solution；
(2) steel of different steel grades continues the start temperature K of water cooling are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
K=Ms+ (40 DEG C~60 DEG C),
Citing: 5CrNiMo steel Ms is 230 DEG C,
Then K=Ms+ (40~60)=230+40~230+60=270~290
5CrNiMo steel continues water cooling start temperature value range are as follows: 270 DEG C≤K≤290 DEG C；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
K=Ms+ (20 DEG C~40 DEG C)
Citing: GCr15 steel Ms is 240 DEG C,
Then K=Ms+ (20~40)=240+20~230+40=260~280
GCr15 steel continues water cooling start temperature value range are as follows: 260 DEG C≤K≤280 DEG C
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
K=Ms- (80 DEG C~120 DEG C)
Citing: 45 steel Ms are 350 DEG C,
Then K=Ms- (80~120)=350-80~350-120=270~230
45 steel continue water cooling start temperature value range are as follows: 230 DEG C≤K≤270 DEG C
(3) steel is the start temperature K for continuing water cooling, is transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously It is cooled to room temperature；
(1) steel is the start temperature K for continuing water cooling, is transferred to third in mass fraction 5%~10%NaCl aqueous solution immediately Secondary cooling KL and it is not cold；
(2) water outlet of steel third time is risen again using waste heat stops the temperature rising to M as in 5%~10%NaCl of mass fraction 4th cooling start temperature in aqueous solution；
(3) the start temperature M of the 4th water cooling of steel of different steel grades are as follows:
1) middle and high carbon medium alloy steel is 110 DEG C~140 DEG C；
2) high-carbon steel and middle and high carbon low alloy steel are 90 DEG C~120 DEG C；
3) medium and low carbon steel and low-carbon low-alloy steel are 70 DEG C~100 DEG C；
(4) steel is the start temperature M of the 4th water cooling, is transferred in mass fraction 5%~10%NaCl aqueous solution the immediately Four cooling MN are to room temperature；
(5) steel is the start temperature K for continuing water cooling, is transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously The beneficial effect being cooled to room temperature；
1) water hardening of prior art steel is to be cooled to~80 DEG C in water, and water outlet is air-cooled to room temperature, causes austenite Thermostabilization degree improves, and cold treatment and tempering difficulty increase；
2) single medium water hardening of steel of the present invention is interrupted water cooling to room temperature, with refine crystal grain improve steel obdurability and Austenite thermostabilization degree is reduced, cold treatment and tempering difficulty are reduced；This is because:
1. crystal grain is refined with heat treatment method, to improve the tough of steel with " invertibity of martensite transfor mation " rule Property；
2. the austenite thermostabilization degree of steel and residence time at a certain temperature are long, austenite thermostabilization degree Greatly, to shorten the residence time at a certain temperature, interrupted water cooling to room temperature is dropped immediately with reducing austenite thermostabilization degree Low cold treatment and tempering difficulty；
(4) the interrupted water cooling of steel is transferred to down one of heat treatment procedure to room temperature immediately；This is because the Ovshinsky body heat of steel is steady Surely changing degree, the residence time is long at a certain temperature, and austenite thermostabilization degree is big, to shorten stop at a certain temperature Time reduces cold treatment and tempering difficulty to reduce austenite thermostabilization degree.
8. the interrupted quenching (as shown in Figure 8) of steel are as follows:
(1) steel be discharged again using waste heat rise again to K stop rise temperature be steel interrupted quenching in cooling capacity Cooling start temperature in relatively weak medium:
(2) steel of different steel grades start temperature K cooling in the relatively weak medium of cooling capacity are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) steel is cooling start temperature K in the relatively weak medium of cooling capacity, and the steel of different steel grades is transferred to cold immediately But in the relatively weak different medium of ability cooling KL and it is not cold；
(1) middle and high carbon medium alloy steel is transferred to air-cooled immediately；
(2) high-carbon steel and middle and high carbon low alloy steel are transferred to air-cooled immediately；
(3) it is cold to be transferred to mist immediately for medium and low carbon steel and low-carbon low-alloy steel；
(4) it is in mass fraction that steel, which goes out the relatively weak medium of cooling capacity to rise again using waste heat to the temperature that M stops rising, Start temperature cooling for the third time in 5%~10%NaCl aqueous solution；
(5) the start temperature M of the steel third time water cooling of different steel grades are as follows:
(1) middle and high carbon medium alloy steel is 70 DEG C~100 DEG C；
(2) high-carbon steel and middle and high carbon low alloy steel are 90 DEG C~120 DEG C；
(3) medium and low carbon steel and low-carbon low-alloy steel are 110 DEG C~140 DEG C；
(6) steel is the start temperature M of third time water cooling, is transferred in mass fraction 5%~10%NaCl aqueous solution the immediately MN is cooled down three times to room temperature；
(1) interrupted quenching of prior art steel is cooled to room temperature in the relatively weak medium of cooling capacity, causes Ovshinsky Body heat stable degree improves, and cold treatment and tempering difficulty increase；
(2) interrupted quenching of steel of the present invention is that water cooling is not cold, and cooling is not cold in the relatively weak medium of cooling capacity Thoroughly, the relatively weak medium of cooling capacity is risen again using waste heat to the start temperature of third time water cooling out, is transferred to mass fraction 5% immediately It is cooled to room temperature for the third time in~10%NaCl aqueous solution, sees Fig. 8, to refine the obdurability and reduction austenite that crystal grain improves steel Thermostabilization degree reduces cold treatment and tempering difficulty；This is because:
1) with " invertibity of martensite transfor mation " rule, crystal grain is refined with heat treatment method, to improve the tough of steel Property；
2) the austenite thermostabilization degree of steel and residence time at a certain temperature are long, austenite thermostabilization degree Greatly, to shorten the residence time at a certain temperature, interrupted water cooling to room temperature is dropped immediately with reducing austenite thermostabilization degree Low cold treatment and tempering difficulty；
(7) molten steel is cooled to room temperature, is transferred to down one of heat treatment procedure immediately；This is because the austenite thermostabilization of steel The residence time is long at a certain temperature for degree, and austenite thermostabilization degree is big, to shorten the residence time at a certain temperature, To reduce austenite thermostabilization degree, cold treatment and tempering difficulty are reduced.
9. mass fraction 5%~10%NaCl aqueous temperature is controlled at 15 DEG C~38 DEG C.

Claims (9)

1. a kind of fine grain intensive quenching cooling means of steel, it is characterized in that after steel austenitizing, in mass fraction 5% after pre-cooling It is cooling for the first time in~10%NaCl aqueous solution to bypass C- curve range of instability --- nose portion temperature to martensitic regions and it is not cold, It is discharged and is risen again using waste heat to bainite start temperature Bs+ (50 DEG C~100 DEG C) for the first time, but perlitic transformation temperature must be lower than Degree is transferred in mass fraction 5%~10%NaCl aqueous solution immediately and is cooled to martensitic regions again and not cold, again water conservancy out It is risen again with waste heat start temperature --- Ms (martensite start) point cooling together under the quenching that the temperature for stopping rising is steel Ms is on the upper side or temperature on the lower side；
The described method includes:
(1) austenitizing of steel；
(2) pre-cooling of steel；
(3) control of steel is cold；
(4) isothermal hardening of steel；
(5) grade quench of steel；
(6) single medium water hardening of steel；
(7) interrupted quenching of steel.
2. the austenitizing of steel as described in claim 1, it is characterized in that the austenitizing of the steel are as follows:
(1) it determines that quenching temperature, soaking time and the heating rate of steel change start temperature As to reduce austenite, mentions High Ms (martensite start) point Ms reduces the temperature difference of As and Ms, provides condition for martensite reverted austenite；
(2) determine that quenching ladder preheating number, temperature, soaking time and the heating rate of steel start to reduce austenite transformation Temperature As improves Ms (martensite start) point Ms, reduces the temperature difference of As and Ms, provides condition for martensite reverted austenite.
3. the pre-cooling of steel as described in claim 1, it is characterized in that the pre-cooling of the steel are as follows:
(1) it after determining steel austenitizing, comes out of the stove and is pre-chilled in air；
(2) precooling temperature of steel is determined are as follows:
(1) eutectoid steel and hypereutectoid steel are Ar1(10 DEG C~30 DEG C)；
(2) sub-eutectoid steel is Ac1+ (50 DEG C~80 DEG C), but must < Ac3；
(3) pre-cooling for determining steel is precooling temperature, is transferred in mass fraction 5%~10%NaCl aqueous solution immediately cooling.
4. the control of steel as described in claim 1 is cold, it is characterized in that the control of the steel is cold are as follows:
(1) after determining steel austenitizing, surface layer certain depth is cold in mass fraction 5%~10%NaCl aqueous solution after pre-cooling But C- curve range of instability --- the not cold degree of nose portion temperature to Ms (martensite start) point Ms or less is bypassed, and is reached To each critical point desired temperature；
(2) cooling for the first time in mass fraction 5%~10%NaCl aqueous solution after pre-cooling to bypass C- after determining steel austenitizing Curve range of instability --- the nose portion temperature degree not cold to martensitic regions, i.e. cooling time for the first time are as follows: be discharged for the first time It is risen again using waste heat to bainite start temperature Bs+ (50 DEG C~100 DEG C), but perlitic transformation temperature must be lower than；
(3) it determines that steel is discharged for the first time to rise again using waste heat to bainite start temperature Bs+ (50 DEG C~100 DEG C), but must be low In perlitic transformation temperature, it is transferred in mass fraction 5%~10%NaCl aqueous solution and cools down again immediately；
(4) determine that steel is cooled to martensitic regions and not cold journey again in mass fraction 5%~10%NaCl aqueous solution Degree, i.e. cooling time again are as follows: be discharged again cooling together under the quenching that the temperature risen again using waste heat and stop rising is steel Start temperature --- Ms (martensite start) point Ms is on the upper side or temperature on the lower side.
5. the isothermal hardening of steel as described in claim 1, it is characterized in that the isothermal hardening of the steel are as follows:
(1) determine steel be discharged again using waste heat rise again stop rise temperature be steel enter in slow cooling box using waste heat progress Noenergy supplements the isothermal start temperature that isothermal is kept；
(2) the isothermal start temperature for determining steel is Ms+ (20 DEG C~50 DEG C)；
(3) it determines that steel is isothermal start temperature, is transferred in slow cooling box and is protected using the isothermal that waste heat carries out noenergy supplement immediately It holds；
(4) determine that steel is kept in slow cooling box using the isothermal that waste heat carries out noenergy supplement with isothermal start temperature, it will be continuous Cooling process merges to be kept in process in isothermal；
(5) performance requirement of slow cooling box is determined；
(1) good heat insulating of slow cooling box is determined；
(2) it determines and slow cooling tank inlet is automatically closed immediately after steel enters slow cooling box；
(6) isothermal time of steel is determined；
(1) it determines that steel is isothermal start temperature, is transferred in slow cooling box and is kept using the isothermal that waste heat carries out noenergy supplement immediately, Start to calculate isothermal time；
(2) determine steel isothermal time be bainite transformation start and end of a period line the time required to 50%~70%；
(7) it determines and goes out slow cooling box after steel isothermal is kept, be transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously cold But to room temperature；
(8) determine that the interrupted water cooling of steel to room temperature, is transferred to down one of heat treatment procedure immediately.
6. the grade quench of steel as described in claim 1, it is characterized in that the grade quench of the steel are as follows:
(1) determine steel be discharged again using waste heat rise again stop rise temperature be steel enter stand air in using waste heat into Row noenergy supplements the classification start temperature that isothermal is kept；
(2) the classification start temperature of steel is determined are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) steel is determined as classification start temperature, is transferred to stand in air immediately and be protected using the isothermal that waste heat carries out noenergy supplement It holds；
(4) steel is determined to be classified start temperature in standing air and keep using the isothermal that waste heat carries out noenergy supplement, will be connected Continuous cooling process merges to be kept in process in isothermal；
(5) grading time of steel is determined；
(1) steel is determined as classification start temperature, is transferred to stand in air immediately and be protected using the isothermal that waste heat carries out noenergy supplement It holds, starts to calculate grading time；
(2) grading time for determining steel is (90~120) s；
(6) it determines and goes out to stand air after steel isothermal is kept, be transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously It is cooled to room temperature；
(7) determine that the interrupted water cooling of steel to room temperature, is transferred to down one of heat treatment procedure immediately.
7. single medium water hardening of steel as described in claim 1, it is characterized in that single medium water hardening of the steel are as follows:
(1) determining that steel is discharged the temperature risen again using waste heat and stop rising again is single medium quenching of steel in mass fraction 5% Continue cooling start temperature in~10%NaCl aqueous solution；
(2) determine that steel continues the start temperature of water cooling are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) it determines that steel is the start temperature for continuing water cooling, is transferred in mass fraction 5%~10%NaCl aqueous solution immediately discontinuously It is cooled to room temperature；
(4) determine that the interrupted water cooling of steel to room temperature, is transferred to down one of heat treatment procedure immediately.
8. the interrupted quenching of steel as described in claim 1, it is characterized in that the interrupted quenching of the steel are as follows:
(1) determining that steel is discharged the temperature risen again using waste heat and stop rising again is the interrupted quenching of steel in cooling capacity phase To start temperature cooling in weak medium:
(2) steel start temperature cooling in the relatively weak medium of cooling capacity is determined are as follows:
(1) middle and high carbon medium alloy steel is Ms+ (40 DEG C~60 DEG C)；
(2) high-carbon steel and middle and high carbon low alloy steel are Ms+ (20 DEG C~40 DEG C)；
(3) medium and low carbon steel and low-carbon low-alloy steel are Ms- (80 DEG C~120 DEG C)；
(3) it determines that steel is cooling start temperature in the relatively weak medium of cooling capacity, is transferred to relatively weak Jie of cooling capacity immediately It is cooled down in matter and not cold；
(4) determine steel go out the relatively weak medium of cooling capacity using waste heat rise again stop rise temperature be mass fraction 5%~ Start temperature cooling for the third time in 10%NaCl aqueous solution；
(5) it determines that steel is the start temperature of third time water cooling, is transferred to immediately cold in mass fraction 5%~10%NaCl aqueous solution But to room temperature；
(6) it determines that molten steel is cooled to room temperature, is transferred to down one of heat treatment procedure immediately.
9. the fine grain intensive quenching cooling means of steel as described in claim 1, it is characterized in that: mass fraction 5%~10% NaCl aqueous temperature is controlled at 18 DEG C~38 DEG C.
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CN111500832A (en) * 2020-05-06 2020-08-07 浙江天基重工机械有限公司 Preparation process of alloy steel forge piece
CN113969333A (en) * 2021-10-22 2022-01-25 中车戚墅堰机车车辆工艺研究所有限公司 Method for inhibiting structure grain size in quenching heat treatment process of steel workpiece
CN113969333B (en) * 2021-10-22 2022-12-23 中车戚墅堰机车车辆工艺研究所有限公司 Method for inhibiting structure grain size in quenching heat treatment process of steel workpiece
CN114107615A (en) * 2021-11-05 2022-03-01 云南昆钢耐磨材料科技股份有限公司 Heat treatment method for regulating and controlling steel structure through spraying
CN114107615B (en) * 2021-11-05 2023-08-22 云南昆钢耐磨材料科技股份有限公司 Heat treatment method for regulating and controlling steel tissues through spraying

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