CN108181170A - Steel material crackle forms the stretching fracture determination method of period - Google Patents
Steel material crackle forms the stretching fracture determination method of period Download PDFInfo
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Abstract
A kind of steel material crackle forms the stretching fracture determination method of period, belongs to steel material FAILURE ANALYSIS TECHNOLOGY field.It first has to prepare the tensile sample comprising crackle and carries out breaking test, two crack surfaces are detached, dimple, cleavage, Quasi cleavage are whether there is by fracture microstructure or along features such as crystalline substances judge that crackle forms the period.The advantage is that compared with existing metallographic observation method, tensile fracture analysis method does not destroy crackle and its pattern of neighbouring microscopic structure, can improve the judgement accuracy that crackle forms the period, and important evidence is provided to analyze the Crack cause of crackle and formulating the precautionary measures.
Description
Technical field
The invention belongs to steel material FAILURE ANALYSIS TECHNOLOGY field, more particularly to a kind of steel material crackle forms the period
Stretching fracture determination method.More particularly to a kind of ferritic-pearlitic shaped steel iron material crackle forms the determination method of period.
Background technology
The tissue that ferritic-pearlitic shaped steel iron material generally refers to steel is ferrite+pearlite below about 600 DEG C,
About 600~800 DEG C occur " austenite → ferrite+pearlite " transformation, are austenite at about 800~1200 DEG C.Crackle is iron
The defects of common in ferritic pearlite type steel material, crackle most probable are formed in two periods：First, in " austenite → iron element
Body+pearlite " changes in the austenite before starting, second is that the iron element after " austenite → ferrite+pearlite " transformation starts
In body and/or pearlite.Study science, rational analysis method for accurately judge crackle formed the period, this be analysis crackle
The process procedure of formation and then the key for taking the precautionary measures, while be also difficult point.
Conventional metallographic observation method is mainly used currently for the analysis method of steel material crackle, observes crackle group nearby
Decarburization and oxidation cloud point are whether there is in knitting, if any decarburization and/or oxidation cloud point, then judges that crackle is formed in steel manufacture process
Heating process or process before such as then judge that crackle is formed in steel manufacture process without decarburization also without oxidation cloud point
Heating process after, but good method there is no to define before the structural transformation that crackle is formed in after heating process also at present
After being structural transformation, so as to which targetedly the precautionary measures cannot be taken in corresponding process.
Moreover, traditional metallographic observation method is to analyze crackle by metallographic sample preparation and microexamination, there are following deficiencies：First,
Quartz sand particle, antiscuffing paste and the water of sample making course sand paper can be remained in inside crackle, destruction or the original pattern of corrosion cracking, and one
A little reaction crackles form the important microscopic features of period and are likely to be broken；2nd, conventional metallographic observation institute it is seen that crackle one
Two-dimensional appearance on a metallographic flour milling can not completely reflect the three-dimensional feature of crackle, and observed metallographic flour milling is cut through just to be split
The possibility very little of line source region, analysis result is inevitably " taking a part for the whole ".The above-mentioned deficiency of traditional metallographic observation method causes it can not
The accurate specific period concluded crackle and formed.
Invention content
The purpose of the present invention is to provide the stretching fracture determination methods that a kind of steel material crackle forms the period, solve
Traditional metallographic observation method can not accurately conclude the specific period problem that crackle is formed.Referred to herein as " tensile fracture analysis
Method ", this method first have to prepare the tensile sample comprising crackle and carry out breaking test, two crack surfaces detached, by disconnected
Mouth microstructure whether there is dimple, cleavage, Quasi cleavage or forms the period along the features such as crystalline substance judgement crackle.
A kind of steel material crackle forms the stretching fracture determination method of period, and specific steps and parameter is as follows：
1st, when find in steel there are during crackle, should carry out at the first time crackle protection processing, prevent water, dust and oil
Dirt enters inside crack damage or corrosion cracking original appearance, and clean antirust oil droplet is expired crackle to completely cut off air and water, blend compounds
Band winding package prevents antirust oil to be lost in, and following steps were completed in 24 hours；
2nd, a tensile sample for including crackle is processed in sample cracks, the size of tensile sample is according to crack size
It determines, tensile sample carries out room temperature tensile on microcomputer controlled electronic universal tester, to ensure that sample is broken along cracks, draws
Stretching speed cannot be too fast, and cupping machine crosshead displacement speed should be controlled in 0.005~0.01mm/min, until sample is along crackle
Fracture thus enables two crack surfaces mechanically decoupled without destroying crack surface primary morphology.
3rd, to prevent breaked fracture long-time ingress of air, dust and water from aoxidizing or corroding, fracture is carried out first
Protection processing, clean antirust oil droplet expire into fracture with exclusion of water, dust and greasy dirt, with absorbent cotton package fracture and in outer layer
It is sealed with adhesive tape, cutting fluid pollution, corrosion fracture, utilize wire cutting during preventing external force damage fracture and avoid wire cutting
Fracture sample with crack surface is cut one section of 10~20mm of length, is observed to clean and to be put into scanning electron microscope.
4th, the adhesive tape and the absorbent cotton of package wound on the outside of fracture sample after removal wire cutting successively, sample is careful
Be put into the beaker for filling 50~80mml acetone solns, fracture surface of sample upward, then by beaker be put into supersonic wave cleaning machine into
Row ultrasonic activation cleans, 10~30 DEG C of cleaning temperature, 5~10min of time, so repeatedly 2~3 times, and third after cleaning
Until ketone solution is clean.Sample is put into again in the beaker for filling 50~80ml alcoholic solutions, fracture surface of sample upward, then will be burnt
Cup, which is put into supersonic wave cleaning machine, carries out ultrasonic activation cleaning, 10~30 DEG C of cleaning temperature, 5~10min of time, so repeatedly
2~3 times.Finally sample is taken out, is dried up sample completely using the cold wind of hair dryer, is put into glassware and is sent to scanning electricity
Mirror carries out fracture observation.
5th, amplify under scanning electron microscope on 500~1000 times of observation fractures with primary fissure line face corresponding region, be set as the micro- of A areas
Shape characteristic is seen, according to steel material fracture professional general knowledge, when intact steel material is broken under the effect of interior external carbuncle
Fracture Morphology is broadly divided into：Tough socket type fracture, cleavage type fracture, quasi-cleavage fracture and intergranular fracture, this is this method
Judge that crackle forms the Main Basiss of period.Observation result has following three kinds：
1) such as region " A " is one or more of " dimple " type fracture, cleavage type fracture or quasi-cleavage fracture, then sentences
Determine crackle and form the period after the completion of " austenite → ferrite+pearlite " transformation.
2) such as region " A " is intergranular fracture, then measures and count the average diameter d of 30~50 " crystal grain " on fracture1, together
When measure and count the average diameter d of 30~50 ferrite and pearlite crystal grain of the material2、d3, such as d1＞ d2And d1＞ d3Then
The path for illustrating crack propagation during grain boundary fracture is not ferrite and pearlite crystal boundary, but austenite grain boundary, crackle are formed in
Austenite phase field；Such as d2And/or d3With d1Close, then crack propagation path is ferrite and pearlite crystal boundary during grain boundary fracture, is split
Line is formed in after the completion of " austenite → ferrite+pearlite " transformation；According to steel material common sense, it is impossible to d occur2＞ d1Or
d3＞ d1Situation.
3) such as microscopic appearance in region " A " then judges that crackle forms the period in " Ovshinsky without any one of features described above
Body → ferrite+pearlite " transformation start before heating or hot procedure, crackle shape after the hot-working such as rolling, forging
Looks are destroyed, and do not have above-mentioned Fracture Characteristics.
It is an advantage of the current invention that compared with existing metallographic observation method, tensile fracture analysis method does not destroy crackle and its attached
The pattern of nearly microscopic structure can improve the judgement accuracy that crackle forms the period, to analyze the Crack cause of crackle and formulating anti-
Model measure provides important evidence.
Description of the drawings
Fig. 1 is the tensile sample schematic diagram comprising crackle.
Fig. 2 is fracture micro-appearance feature, belongs to cleavage type fracture schematic diagram.
Specific embodiment
Embodiment 1
By taking crackle at one inside the Q345D bars that specification is Φ 250mm as an example, the crackle is found in macroscopic examination,
To protect crack morphology, clean antirust oil droplet is expired into crackle to completely cut off air and water, blend compounds band winding package prevents antirust
Oil stream is lost.A tensile sample for including crackle, tensile sample thickness 5mm, length 150mm, in microcomputer are processed in cracks
Room temperature tensile is carried out on control electronic universal tester, to ensure that sample is broken along cracks, cupping machine crosshead displacement speed
Degree is set as 0.01mm/min, until sample, along crack fracture, two crack surfaces are able to mechanically decoupled former without destroying crack surface
Beginning pattern.To prevent breaked fracture long-time ingress of air, dust and water from aoxidizing or corroding, the guarantor of fracture is carried out first
Clean antirust oil droplet is expired fracture with exclusion of water, dust and greasy dirt, fracture is wrapped up and in outer layer with thoroughly with absorbent cotton by shield processing
Bright rubber belt sealing, cutting fluid pollution, corrosion fracture during preventing external force damage fracture and avoid wire cutting, using wire cutting by band
The fracture sample for having crack surface cuts one section of length 15mm, is observed to clean and to be put into scanning electron microscope.
The adhesive tape and the absorbent cotton of package wound on the outside of fracture sample after removal wire cutting successively, sample is carefully put
In the beaker for entering to fill 50mml acetone solns, beaker upward, is then put into supersonic wave cleaning machine and carries out ultrasound by fracture surface of sample
Wave vibration washing, 25 DEG C of cleaning temperature, time 5min, so repeatedly 3 times, the acetone soln after cleaning is completely clean.It again will examination
Sample is put into the beaker for filling 50ml alcoholic solutions, and beaker upward, is then put into supersonic wave cleaning machine and carries out by fracture surface of sample
Ultrasonic activation cleans, 25 DEG C of cleaning temperature, time 5min, so repeatedly 3 times.Finally sample is taken out, using hair dryer
Cold wind dries up sample completely, is put into glassware and is sent to scanning electron microscope progress fracture observation.
Amplify the microscopic appearance feature with primary fissure line face corresponding region on 836 times of observation fractures under scanning electron microscope, find
It is predominantly in " cleavage type " fracture of " river shape " style, therefore, it is determined that crackle is at " austenite → ferrite+pearlite "
It is formed after the completion of structural transformation, the cooling that the generation to prevent this crackle will targetedly after the completion of structural transformation
Corresponding measure is taken in the process.
Claims (1)
1. a kind of steel material crackle forms the stretching fracture determination method of period, which is characterized in that specific steps and parameter is such as
Under：
1) when finding that the protection of progress crackle at the first time is handled there are during crackle in steel, water, dust and greasy dirt entrance are prevented
Inside crack is damaged or corrosion cracking original appearance, and clean antirust oil droplet is expired crackle to completely cut off air and water, the winding of blend compounds band
Package prevents antirust oil to be lost in, and following steps were completed in 24 hours；
2) a tensile sample for including crackle is processed in sample cracks, the size of tensile sample is true according to crack size
Fixed, tensile sample carries out room temperature tensile on microcomputer controlled electronic universal tester, to ensure that sample is broken along cracks, stretches
Testing machine crosshead displacement speed should be controlled in 0.005~0.01mm/min, until sample along crack fracture, thus makes two to split
Line face is able to mechanically decoupled without destroying crack surface primary morphology；
3) to prevent breaked fracture long-time ingress of air, dust and water from aoxidizing or corroding, the guarantor of fracture is carried out first
Clean antirust oil droplet is expired fracture with exclusion of water, dust and greasy dirt, fracture is wrapped up and in outer layer with thoroughly with absorbent cotton by shield processing
Bright rubber belt sealing, cutting fluid pollution, corrosion fracture during preventing external force damage fracture and avoid wire cutting, using wire cutting by band
The fracture sample for having crack surface cuts one section of 10~20mm of length, is observed to clean and to be put into scanning electron microscope；
4) adhesive tape and the absorbent cotton of package wound on the outside of fracture sample after removal wire cutting successively, sample is put into and is filled
In the beaker of 50~80mml acetone solns, beaker upward, is then put into supersonic wave cleaning machine and carries out ultrasonic wave by fracture surface of sample
Vibration washing, 10~30 DEG C of cleaning temperature, 5~10min of time, so repeatedly 2~3 times, the acetone soln after cleaning is done
Until net；Sample is put into again in the beaker for filling 50~80ml alcoholic solutions, beaker upward, is then put into super by fracture surface of sample
Progress ultrasonic activation cleaning in sound wave cleaning machine, 10~30 DEG C of cleaning temperature, 5~10min of time, so repeatedly 2~3 times；
Finally sample is taken out, is dried up sample completely using the cold wind of hair dryer, is put into glassware and is sent to scanning electron microscope progress
Fracture is observed；
5) amplify the microscopic appearance feature with primary fissure line face corresponding region on 500~1000 times of observation fractures under scanning electron microscope,
It is set as " a-quadrant "；Observation result has following three kinds：
1. if a-quadrant is one or more of " dimple " type fracture, cleavage type fracture or quasi-cleavage fracture, then crackle is judged
The period is formed after the completion of " austenite → ferrite+pearlite " transformation；
2. if a-quadrant is intergranular fracture, then the average diameter d of 30~50 " crystal grain " on fracture is measured and counts1, measure simultaneously
And count the average diameter d of 30~50 ferrite and pearlite crystal grain of the material2、d3, such as d1＞ d2And d1＞ d3Then illustrate edge
The path of crack propagation is not ferrite and pearlite crystal boundary during crystalline substance fracture, but austenite grain boundary, crackle are formed in austenite
Phase region；Such as d2And/or d3With d1Close, then crack propagation path is ferrite and pearlite crystal boundary during grain boundary fracture, and crackle is formed
After the completion of " austenite → ferrite+pearlite " transformation；According to steel material common sense, it is impossible to d occur2＞ d1Or d3＞ d1
Situation；
3. if the microscopic appearance of a-quadrant is without any one of features described above, then judge that crackle forms the period in " austenite → iron
Ferritic+pearlite " transformation start before heating or hot procedure, crackle after the hot-working such as rolling, forging pattern by
It destroys, does not have above-mentioned Fracture Characteristics.
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| CN113237908B (en) * | 2021-04-30 | 2022-10-11 | 北京科技大学 | Method for evaluating crack sensitivity of hypo-peritectic steel |
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