CN111607690B - Processing method for improving percent of pass of tensile property of steel plate - Google Patents
Processing method for improving percent of pass of tensile property of steel plate Download PDFInfo
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- CN111607690B CN111607690B CN202010638763.4A CN202010638763A CN111607690B CN 111607690 B CN111607690 B CN 111607690B CN 202010638763 A CN202010638763 A CN 202010638763A CN 111607690 B CN111607690 B CN 111607690B
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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
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Abstract
The application provides a processing method for improving the yield of tensile property of a steel plate, belonging to the technical field of steel. The processing method comprises the following steps: the first stage is as follows: and (3) placing the steel plate on a cooling bed to be cooled to 300-550 ℃. And a second stage: and naturally aging the steel plate for 24 hours or more in a manner of stacking and slow cooling down on a lower line, cutting the steel plate to obtain a plurality of sub-steel plates when the surface temperature of the steel plate is less than or equal to 150 ℃, sampling and processing an initial test sample. And a third stage: and (3) naturally aging the initial test sample and the plurality of sub-steel plates corresponding to the initial test sample for 24-72 h, and detecting the tensile property of the naturally aged initial test sample. Compared with the method for directly detecting the tensile property of the initial test sample in the second stage, the method can improve the yield of the tensile property of the steel plate by the treatment in the third stage.
Description
Technical Field
The application relates to the technical field of steel, in particular to a processing method for improving the yield of tensile property of a steel plate.
Background
The medium plate is one of the most important products in the steel industry and plays a very important role in national economic development. At present, the delivery date of medium and thick plate products is strictly required by customers, particularly the production period of thick steel plates is relatively long, whether the initial inspection performance and the final inspection performance are qualified or not is very important, once the initial inspection performance is unqualified, the probability of qualified rechecking is small, if the rechecking performance is still unqualified, the rolling period is long, the delivery date of the products is seriously influenced, and the market competition is not facilitated.
Since the ultra-fast cold assembly of the medium plate is on line, the produced thick steel plate (the steel plate with the thickness of 40-90 mm) is subjected to normal processes of sampling, processing, inspection and the like, the initial tensile property is often unqualified, and the phenomenon that the yield strength or tensile strength is higher and the elongation is lower is mainly shown.
Disclosure of Invention
The application provides a processing method for improving the yield of the tensile property of a steel plate, and the processing method can improve the yield of the tensile property of the steel plate.
The application provides a processing method for improving the yield of the tensile property of a steel plate, which comprises the following steps: the first stage is as follows: and (3) placing the steel plate on a cooling bed to be cooled to 300-550 ℃. And a second stage: and naturally aging the steel plate for 24 hours or more in a way of stacking and slow cooling in a lower line, cutting the steel plate to obtain a plurality of sub-steel plates when the surface temperature of the steel plate is less than or equal to 150 ℃, sampling and processing the initial test sample. And a third stage: and (3) carrying out natural aging on the initial detection sample and a plurality of sub-steel plates corresponding to the initial detection sample for 24-72 h, and detecting the tensile property of the initial detection sample after natural aging.
In a possible embodiment, if the tensile property test of the initial test sample after natural aging fails, the processing method further comprises the following steps: a fourth stage: and (3) carrying out artificial aging on a plurality of sub steel plates corresponding to the initial test sample, preserving the heat for 5.5-6.5 h at the temperature of 175-185 ℃, naturally cooling in the air, taking the reinspection sample, and detecting the tensile property of the reinspection sample.
In one possible embodiment, the steel sheet is a first steel sheet produced by a non-thermomechanical rolling process, the first steel sheet having a thickness h 1 And is not less than 40h 1 Less than or equal to 65mm, and the treatment method comprises the following steps: the first stage is as follows: the first steel plate is cooled on a cooling bed until the surface temperature is 350-450 ℃. And a second stage: naturally aging the first steel plate in a way of slow cooling by a offline stack, wherein the surface temperature of the first steel plate is 350-450 ℃ at the beginning of the stack, and the natural aging time T 1 The surface temperature of the first steel plate is less than or equal to 150 ℃, the first steel plate is cut to obtain a plurality of first sub-steel plates, and a first circular initial test sample is sampled and processed. And a third stage: carrying out natural aging time T on the first circular initial detection sample and a plurality of first sub-steel plates corresponding to the first circular initial detection sample 2 And the tensile property of the first circular initial test sample after natural aging is detected for 48-72 h.
In a possible embodiment, the steel sheet is subjected to a natural ageing time T in the form of an inline stacking slow cooling 1 The following relationship is satisfied: 18+10 x (h) 1 /65) 2 +t 1 /150≤T 1 ≤18+27×(h 1 /65) 2 +t 1 150; wherein h is 1 Represents the thickness of the first steel plate in mm; t is t 1 Surface temperature, expressed in units of degrees c, at the start of the first steel plate stack; t is 1 The natural aging time is expressed in the unit of h.
In a possible embodiment, in the third stage, the first round preliminary test sample and the plurality of pieces of first sub-steel plates corresponding to the first round preliminary test sample are subjected to natural aging time T 2 The following relationship is satisfied: t is 2 =3 × (elongation-1/2 × SQRT (h) 1 10)); wherein h is 1 Represents the thickness of the first steel plate in mm; t is 2 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the required elongation of the first steel sheet standard.
In one possible embodiment, the steel sheet is a second steel sheet produced by a non-thermomechanical rolling process, the second steel sheet having a thickness h 2 And 65 < h 2 Less than or equal to 90mm, and the treatment method comprises the following steps: the first stage is as follows: the second steel plate is cooled on a cooling bed until the surface temperature is 450-550 ℃. And a second stage: naturally aging the second steel plate in a way of slow cooling by a down-line stacking, wherein the surface temperature of the second steel plate is 450-550 ℃ when the stacking starts, and the natural aging time T 3 The surface temperature of the second steel plate is less than or equal to 150 ℃, the second steel plate is cut to obtain a plurality of second sub-steel plates, and a second round initial test sample is sampled and processed. And a third stage: carrying out natural aging time T on the second circular initial detection sample and a plurality of second sub-steel plates corresponding to the second circular initial detection sample 4 And the tensile property of the second round initial test sample after natural aging is detected for 36-48 h.
In a possible embodiment, the steel sheet is subjected to a natural aging time T in the form of a slow cooling of the steel sheet in a down-line stack 3 The following relationship is satisfied: 40+10 × (h) 2 /90) 2 +t 2 /150≤T 3 ≤40+28×(h 2 /90) 2 +t 2 150; wherein h is 2 Represents the thickness of the second steel plate in mm; t is t 2 Surface temperature, expressed in units of degrees c, at the start of the second steel plate stack; t is 3 The natural aging time is expressed in h.
In a possible embodiment, in the third stage, the second round initial test sample and the plurality of second sub-steel plates corresponding to the second round initial test sample are subjected to natural aging time T 4 The following relationship is satisfied: t is a unit of 4 =2.2 × (elongation-1/2 × SQRT (h) 2 10)); wherein h is 2 Represents the thickness of the second steel plate in mm; t is a unit of 4 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the elongation required by the second steel sheet standard.
In one possible embodiment, the steel sheet is a third steel sheet produced by a thermomechanical rolling process, the third steel sheet having a thickness h 3 And is not less than 40h 3 Less than or equal to 90mm, and the treatment method comprises the following steps: the first stage is as follows: the third steel plate is cooled on a cooling bed until the surface temperature is 300-400 ℃. And a second stage: naturally aging the third steel plate in a mode of slow cooling by stacking in a lower line, and starting stackingThe surface temperature of the third steel plate is 300-400 ℃, and the natural aging time T is 5 And when the surface temperature of the third steel plate is less than or equal to 150 ℃, slitting the third steel plate to obtain a plurality of third sub-steel plates, sampling and processing the rectangular initial test sample. And a third stage: carrying out natural aging time T on the rectangular initial detection sample and a plurality of third sub-steel plates corresponding to the rectangular initial detection sample 6 And (3) detecting the tensile property of the rectangular initial test sample after natural aging for 24-36 h.
In a possible embodiment, the steel sheet is subjected to a natural aging time T in the form of a slow cooling of the steel sheet in a down-line stack 5 The following relationship is satisfied: 22+5 × (h) 3 /90) 2 +t 3 /150≤T 5 ≤22+23×(h 3 /90) 2 +t 3 150; wherein h is 3 Represents the thickness of the third steel plate in mm; t is t 3 Surface temperature, expressed in units of c, at the start of the third steel plate stack; t is 5 The natural aging time is expressed in h.
In a possible embodiment, in the third stage, the rectangular initial test sample and the plurality of third sub-steel plates corresponding to the rectangular initial test sample are subjected to natural aging time T 6 The following relationship is satisfied: t is a unit of 6 =1.6 × (elongation-1/2 × SQRT (h) 3 10)); wherein h is 3 Represents the thickness of the third steel plate in mm; t is 6 The unit of the natural aging time is h; the elongation represents the absolute value of the minimum value of the elongation required by the third steel sheet standard.
The processing method for improving the yield of the tensile property of the steel plate provided by the embodiment of the application has the beneficial effects that:
the steel plate is placed on a cooling bed to be cooled, and then natural aging is carried out in a mode of stacking and slow cooling in a lower line, so that the thermal stress in the steel plate is released slowly and fully. And after natural aging, when the surface temperature of the steel plate is less than or equal to 150 ℃, slitting the steel plate, sampling in the slitting process, and processing an initial test sample.
The inventor finds that if the sample is directly subjected to primary inspection, the yield of the tensile property of the steel plate is low, the number of the steel plates which are unqualified in the primary inspection is large, the probability of retesting or judging the steel plate is increased, and the delivery date of the steel plate is prolonged. Therefore, in the application, the steel plate is naturally aged for 24 hours or more in a linear stacking slow cooling mode at the second stage, the thermal stress in the steel plate can be fully and slowly released, the initial inspection sample and the sub-steel plate after slitting are naturally aged for 24-72 hours at the third stage, and the tissue stress in the steel plate can be effectively reduced, so that the yield of the tensile property of the initial inspection sample after natural aging is improved, the yield of the initial inspection of the steel plate is correspondingly improved, the probability of retesting or judging the steel plate is reduced, the time from production to warehousing of the steel plate is reduced, the delivery period of the steel plate is shortened, and the capacity of quickly responding to the market is improved.
Further, if the tensile property of the initial test sample after the third-stage natural aging is unqualified, all the sub-steel plates corresponding to the initial test sample can be artificially aged, the temperature of the artificial aging is lower, the time is shorter, but the structure stress of the steel plates can be effectively eliminated, so that the yield of the tensile property of the steel plates is further improved.
Furthermore, the calculation formulas of the slow cooling natural aging time of the offline stack in the second stage and the natural aging time in the third stage are provided, the time of the natural aging in the second stage and the third stage can be accurately set, the overaging is avoided, the resource waste is caused, and the qualification rate of the steel plate can be improved in a short time.
Detailed Description
Because the hot rolled steel plate generally has certain 'timeliness', namely, the strength index of the steel plate is reduced, the plasticity index is increased and the performance of the steel plate tends to be stable after a period of time passes after the steel plate is rolled. Therefore, the steel sheet is subjected to aging treatment to increase the plasticity index of the steel sheet, thereby improving the yield of the steel sheet in terms of tensile properties.
The aging treatment refers to a heat treatment process that an alloy workpiece (such as low-carbon steel and the like) is subjected to solution treatment, cold plastic deformation or casting and forging, and then is placed at a higher temperature or room temperature, and the performance, the shape and the size of the alloy workpiece change along with time. If the aging treatment process is adopted, in which the workpiece is heated to a certain lower temperature and is kept warm for a period of time in a shorter time, the process is called artificial aging treatment. The aging phenomenon that occurs when a workpiece is left at room temperature or stored in a natural condition for a long time is called natural aging treatment. The aging treatment in the invention refers to the aging treatment of the steel plate after the steel plate is produced, the steel plate is subjected to the aging treatment through a cooling bed, the steel plate is sampled and processed, and then the processed sample and the steel plate are subjected to the aging treatment.
It should be noted that: and the steel plate tensile property initial inspection qualified rate = the number of inspection batches/total number of inspection batches of all the initial inspection property qualified. Steel sheet tensile property pass rate = number of pass/total number of pass all properties.
In order to improve the qualified rate of the tensile property of the steel plate, the application provides a processing method for improving the qualified rate of the tensile property of the steel plate, which comprises the following steps:
the first stage is as follows: and (3) placing the steel plate on a cooling bed to be cooled to 300-550 ℃. After the steel plate is produced, the temperature of the steel plate is higher, the steel plate is cooled by a cooling bed on the rear part of a hot straightening machine, the steel plate can be timely subjected to off-line stacking and slow cooling, and the smooth production logistics is ensured.
And a second stage: and naturally aging the steel plate for 24 hours or more in a way of stacking and slow cooling in a lower line, cutting the steel plate to obtain a plurality of sub-steel plates when the surface temperature of the steel plate is less than or equal to 150 ℃, sampling and processing the initial test sample. The stack slow cooling can let the thermal stress of steel sheet obtain slowly and fully release, after steel sheet surface temperature drops to the uniform temperature, just can carry out the work of artifical marking off, crop and side cut to the steel sheet to the sample and the processing work of preliminary examination sample, so, after the stack slow cooling was accomplished, the surface temperature of steel sheet must not be higher than 150 ℃.
And a third stage: and (3) naturally aging the initial test sample and the plurality of sub-steel plates corresponding to the initial test sample for 24-72 h, and detecting the tensile property of the naturally aged initial test sample. The inventor researches and discovers that the primary inspection yield of the steel plate is very low without the natural aging of the third stage, and the reason of the primary inspection tensile property is as follows: the temperature difference gradient between the core part and the surface layer is large when the steel plate is rolled and cooled, the tissue difference is large, the tissue stress is large, and the slit sample is naturally aged in the third stage, so that the tissue stress of the steel plate can be reduced, and the initial detection qualification rate of the tensile property of the steel plate is improved.
After the third stage treatment, the initial inspection qualification rate of the tensile property of the steel plate is generally about 97.5%, and the sub-steel plates which are unqualified and correspond to the initial inspection samples are subjected to the artificial aging treatment of the fourth stage, so that the tensile property of the steel plate can be qualified, and the tensile property qualification rate of the steel plate is improved.
Optionally, the fourth stage: and (3) carrying out artificial aging on a plurality of sub steel plates corresponding to the initial test sample, preserving the heat for 5.5-6.5 h at the temperature of 175-185 ℃, then naturally cooling in the air, sampling and processing the reinspection sample, and detecting the tensile property of the reinspection sample. The structure stress in the steel plate can be further eliminated, the tensile property of the reinspection can be qualified, and the yield of the tensile property of the steel plate is improved.
As an example: the artificial aging temperature is 175 ℃, 178 ℃, 180 ℃, 182 ℃ or 185 ℃; the artificial aging time is 5.5h, 5.8h, 6h, 6.2h or 6.5h.
The temperature of artificial aging is lower, the time of aging is shorter, and the structure stress of the steel plate can be effectively eliminated, so that the qualification rate of the tensile property of the steel plate is further improved.
The artificial aging further eliminates the structural stress in the steel plate, so that the tensile property qualification rate of the steel plate can be improved to 99.9 percent. In general, the number of the retest specimens is twice as many as the number of the initial specimens, and the retest specimens are completely acceptable, which indicates that the tensile properties of the steel sheet represented by the retest specimens are acceptable.
The inventor finds that the natural aging time of steel plates with different production processes and different specifications is different due to different finishing rolling temperatures, the temperature of the steel plates passing through a cooling bed, the starting temperature of the slow cooling of the steel plate off-line stacking and the like. According to the difference of the production process of the steel plate and the thickness of the steel plate, the final cooling temperature of the steel plate is different, and the surface temperature of the steel plate on a cooling bed is also different; and because the thickness of the steel plate is different, the temperature drop speed is also different, the thicker the steel plate is, the slower the temperature drop is, and the longer the aging time of the required stacking slow cooling is.
Several different types of steel sheet processing methods will be described in detail below. Before describing the treatment method in detail, it should be noted that: in the steel sheet produced by the non-TMCP process (non-thermomechanical rolling process), when the thickness of the steel sheet is more than or equal to 40mm, a batch rectangular tensile test cannot be carried out, and the test piece needs to be processed into a round test piece according to the standard so as to carry out the tensile test, so that the tensile test piece can be processed into a round test piece with the diameter of 10mm according to the relevant regulation of GB/T2975 standard. For the steel plate produced by the TMCP process (thermo-mechanical rolling process), the GB/T2975 standard clearly stipulates that for the steel plate, a full-thickness or half-thickness rectangular sample is required to be adopted as a tensile sample, and the steel plate produced by the TMCP process with the thickness of 40-90 m is processed into a sample with the thickness of 20-45 mm of the half-thickness rectangular sample for detection. Therefore, according to the provisions of the GB/T2975 standard, the application respectively sets up a non-TMCP process steel plate and a sample, and an aging treatment process of the TMCP process steel plate and the sample, and aims to improve the initial inspection qualified rate and the final inspection qualified rate of the tensile property of the steel plate.
It should be noted that since the TMCP process with a thickness of 80 to 90mm produces a very small amount of steel sheet, the tensile test specimens are processed into the specimens with a half-thickness rectangular specimen thickness of 40 to 45mm, and the tensile test is allowed to be performed in a very small amount.
Further, for the steel plate produced by the non-TMCP process, the aging treatment process is set into two different parts according to the difference of the thickness; for the steel sheets produced by the TMCP process, no distinction is made regarding the thickness, but the time-course setting thereof is different from that of the non-TMCP sheets. The main reason is that the inventor researches and discovers that the samples for detecting tensile property of the steel plate produced by 40-90 mm non-TMCP process are circular samples, the anisotropy of the circular samples is small, the tissue difference and stress concentration of the circular samples are obvious, and the circular samples are particularly influenced by the thickness, so that the samples with obvious tissue difference and stress concentration need to be distinguished by different thicknesses for different aging treatments; the samples for detecting the tensile property of the steel plate produced by the 40-90 mm TMCP process are rectangular samples, the tissue difference is small, the tissue stress is correspondingly small, the self stress is small, and the influence of the thickness is small, so the samples can be considered together in the whole range.
If the steel plate is the first steel plate produced by the non-TMCP process, the thickness of the first steel plate is h 1 And is not less than 40h 1 Less than or equal to 65mm, and the treatment method comprises the following steps:
the first stage is as follows: the first steel plate is cooled on a cooling bed until the surface temperature is 350-450 ℃. Optionally, the first steel plate is cooled on a cooling bed to a surface temperature of 350 ℃, 400 ℃ or 450 ℃.
And a second stage: naturally aging the first steel plate in a way of slow cooling by a offline stack, wherein the surface temperature of the first steel plate is 350-450 ℃ at the beginning of the stack, and the natural aging time T 1 The surface temperature of the first steel plate is less than or equal to 150 ℃, the first steel plate is cut to obtain a plurality of first sub-steel plates, and a first circular initial test sample is sampled and processed.
In the second stage, the steel sheet can be slit when the surface temperature of the steel sheet is cooled to 150 ℃ or lower after the surface temperature of the steel sheet at the start of stacking is close to the finish cooling temperature of cooling on the cooling bed and the natural aging time is 24 hours or longer.
In order to further determine the time of natural aging of the steel plates stacked and slowly cooled off the production line, the time of natural aging is prevented from being overlong while thermal stress is eliminated, and meanwhile, the smooth production logistics of the subsequent steel plates are ensured. Optionally, the natural aging time T is carried out in a way of off-line stacking slow cooling 1 The following relationship is satisfied: 18+10 × (h) 1 /65) 2 +t 1 /150≤T 1 ≤18+27×(h 1 /65) 2 +t 1 150; wherein h is 1 Represents the thickness of the first steel plate in mm; t is t 1 The surface temperature, expressed in units of degrees c, at the start of the first steel plate stack; t is a unit of 1 The natural aging time is expressed in h.
And a third stage: carrying out natural aging time T on the first circular initial detection sample and a plurality of first sub-steel plates corresponding to the first circular initial detection sample 2 And the tensile property of the first round initial test sample after natural aging is detected for 48-72 h. In some possible embodiments, the natural aging time in the third stage is 48h, 52h, 56h, 60h,64h, 68h or 72h.
In order to accurately determine the natural aging time of the third stage, the over-aging is avoided, and the sample treatment time is prolonged. Optionally, the first circular initial test sample and the multiple first sub-steel plates corresponding to the first circular initial test sample are subjected to natural aging time T 2 The following relationship is satisfied: t is a unit of 2 =3 × (elongation-1/2 × SQRT (h) 1 10)); wherein h is 1 Represents the thickness of the first steel plate in mm; t is a unit of 2 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the elongation required by the first steel sheet standard, and SQRT represents the square of the opening.
And if the tensile property of the first circular initial test sample after natural aging is unqualified, the fourth stage: and (3) carrying out artificial aging on a plurality of first sub steel plates corresponding to the first circular initial test samples, carrying out heat preservation for 5.5-6.5 h at the temperature of 175-185 ℃, then naturally cooling in the air, sampling and processing the circular reinspection samples, and detecting the tensile property of the circular reinspection samples.
If the steel plate is a second steel plate produced by a non-TMCP process, the thickness of the second steel plate is h 2 And 65 < h 2 Less than or equal to 90mm, and the treatment method comprises the following steps:
the first stage is as follows: the second steel plate is cooled on a cooling bed until the surface temperature is 450-550 ℃. Optionally, the second steel plate is cooled on a cooling bed to a surface temperature of 450 ℃, 500 ℃ or 550 ℃.
And a second stage: naturally aging the second steel plate in a way of slow cooling by a down-line stacking, wherein the surface temperature of the second steel plate is 450-550 ℃ when the stacking starts, and the natural aging time T 3 The surface temperature of the second steel plate is less than or equal to 150 ℃, the second steel plate is cut to obtain a plurality of second sub-steel plates, and a second round initial test sample is sampled and processed.
In the second stage, the steel sheet can be slit by cooling the surface temperature of the steel sheet to 150 ℃ or lower after the surface temperature of the steel sheet at the start of stacking is close to the finish cooling temperature of cooling on the cooling bed and the natural aging time is 48 hours or more.
In order to further determine the time of natural aging of the steel plates stacked and slowly cooled off the production line, the time of natural aging is prevented from being overlong while thermal stress is eliminated, and meanwhile, the smooth production logistics of the subsequent steel plates are ensured. Optionally, the natural aging time T is carried out in a way of off-line stacking slow cooling 3 The following relationship is satisfied: 40+10 × (h) 2 /90) 2 +t 2 /150≤T 3 ≤40+28×(h 2 /90) 2 +t 2 150; wherein h is 2 Represents the thickness of the second steel plate in mm; t is t 2 Surface temperature, expressed in units of ° c, at the start of the second steel plate stack; t is 3 The natural aging time is expressed in h.
And a third stage: carrying out natural aging time T on the second circular initial inspection sample and a plurality of second sub-steel plates corresponding to the second circular initial inspection sample 4 And the tensile property of the second round initial test sample after natural aging is detected for 36-48 h. In some possible embodiments, the natural aging time in the third stage is 36h, 40h, 44h, or 48h.
In order to accurately determine the natural aging time of the third stage, the over-aging is avoided, and the sample treatment time is prolonged. Optionally, the second round initial test sample and a plurality of second sub-steel plates corresponding to the second round initial test sample are subjected to natural aging time T 4 The following relationship is satisfied: t is 4 =2.2 × (elongation-1/2 × SQRT (h) 2 10)); wherein h is 2 Represents the thickness of the second steel plate in mm; t is 4 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the elongation required for the second steel sheet standard.
And if the tensile property of the second round initial test sample after natural aging is unqualified, the fourth stage: and (3) carrying out artificial aging on a plurality of second sub steel plates corresponding to the second circular initial test samples, carrying out heat preservation for 5.5-6.5 h at the temperature of 175-185 ℃, then naturally cooling in the air, sampling and processing the circular reinspection samples, and detecting the tensile property of the circular reinspection samples.
If the steel plate is a third steel plate produced by a TMCP process, the thickness of the third steel plateIs h 3 And is not less than 40h 3 Less than or equal to 90mm, and the treatment method comprises the following steps:
the first stage is as follows: and cooling the third steel plate on a cooling bed until the surface temperature is 300-400 ℃. Optionally, the third steel plate is cooled on a cooling bed to a surface temperature of 300 ℃, 350 ℃ or 400 ℃.
And a second stage: naturally aging the third steel plate in a manner of slow cooling by a following-line stacking, wherein the surface temperature of the third steel plate is 300-400 ℃ when the stacking starts, and the natural aging time T is 5 And when the surface temperature of the third steel plate is less than or equal to 150 ℃, slitting the third steel plate to obtain a plurality of third sub-steel plates, sampling and processing the rectangular initial test sample.
In the second stage, the steel sheet can be slit when the surface temperature of the steel sheet is cooled to 150 ℃ or less after the surface temperature of the steel sheet at the start of stacking is close to the final cooling temperature of cooling on the cooling bed and the natural aging time is 24 hours or more.
In order to further determine the time of natural aging of the lower-line stacked slow-cooling steel plate, the thermal stress is eliminated, meanwhile, the time of natural aging is prevented from being overlong, and meanwhile, the subsequent steel plate production logistics are ensured to be smooth. Optionally, the natural aging time T is carried out in a way of off-line stacking slow cooling 5 The following relationship is satisfied: 22+5 × (h) 3 /90) 2 +t 3 /150≤T 5 ≤22+23×(h 3 /90) 2 +t 3 150; wherein h is 3 Represents the thickness of the third steel plate in mm; t is t 3 Surface temperature, expressed in units of c, at the start of the third steel plate stack; t is a unit of 5 The natural aging time is expressed in the unit of h.
And a third stage: carrying out natural aging time T on the rectangular initial inspection sample and a plurality of third sub-steel plates corresponding to the rectangular initial inspection sample 6 And (3) detecting the tensile property of the rectangular initial test sample after natural aging for 24-36 h. In some possible embodiments, the natural aging time in the third stage is 24h, 28h, 32h, or 36h.
In order to accurately determine the natural aging time of the third stage, avoid over-aging and prolong the sample treatment timeAnd (3) removing the solvent. Optionally, the rectangular initial inspection samples and a plurality of third sub-steel plates corresponding to the rectangular initial inspection samples are subjected to natural aging time T 6 The following relationship is satisfied: t is 6 =1.6 × (elongation-1/2 × SQRT (h) 3 10)); wherein h is 3 Represents the thickness of the third steel plate in mm; t is 6 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the elongation required by the third steel sheet standard.
And if the tensile property of the rectangular initial test sample after natural aging is unqualified, the fourth stage: and (3) carrying out artificial aging on a plurality of third sub-steel plates corresponding to the rectangular initial test samples, carrying out heat preservation for 5.5-6.5 h at the temperature of 175-185 ℃, then naturally cooling in the air, sampling and processing the rectangular reinspection samples, and detecting the tensile property of the rectangular reinspection samples.
It should be noted that, for all steel plates, only one initial inspection sample needs to be processed, and for the retest sample, two retests need to be processed.
The steel plate and the test sample thereof can effectively eliminate the thermal stress and the structural stress in the production process of the steel plate through the multistage aging treatment method, so that the performance of the steel plate tends to be stable, and the quality and the tensile property qualification rate of the steel plate are finally improved, thereby ensuring the safe and reliable use of the thick steel plate.
For the first stage, all 40-90 mm steel plates must pass through the cooling bed after the steel plates are produced, according to components and process design and by combining with the condition of production line equipment, the steel plates with different production processes and different specifications have different final cooling temperatures and different cooling speeds on the cooling bed, so the surface temperatures of the upper cooling bed and the lower cooling bed of the steel plates are also different.
The final cooling temperature of the steel plate produced by the non-TMCP process is higher after the production is finished and is generally between 600 and 700 ℃, and the final cooling temperature of the steel plate produced by the TMCP process is lower after the production is finished and is generally between 500 and 600 ℃.
In the second stage, after the steel plate passes through the cooling bed, the steel plate is adsorbed from the cooling bed by the high-temperature magnet and is stacked and slowly cooled. According to the different thickness of the steel plate and the stackingThe initial surface temperature is different, the temperature drop speed is different, the thicker the steel plate is, the higher the stacking initial surface temperature is, the lower the temperature drop speed is, and the longer the required stacking slow cooling aging time is correspondingly. Generally, the thickness h of the steel plate produced by the non-TMCP process is less than or equal to 40 ≤ 1 When the thickness is less than or equal to 65mm, cooling the mixture on a cooling bed to the surface temperature of 350-450 ℃, and naturally aging the mixture on the cooling bed in a stacking and slow cooling manner; when the thickness of the steel plate is more than 65 h 2 When the thickness is less than or equal to 90mm, cooling the mixture on a cooling bed to the surface temperature of 450-550 ℃, and naturally aging the mixture on the cooling bed in a stacking slow cooling mode; when the thickness h of the steel plate produced by the TMCP process is more than or equal to 40 ≤ 3 When the thickness is less than or equal to 90mm, the final cooling temperature is relatively low after the production is finished, and the product is cooled on a cooling bed to the surface temperature of 300-400 ℃, and then the natural aging can be carried out on the cooling bed in a stacking slow cooling mode.
The steel plate is naturally aged in a stacking slow cooling mode, so that the thermal stress of the steel plate is slowly and fully released, and the higher the temperature is, the longer the stacking slow cooling time of a lower cooling bed is, the more fully the thermal stress of the steel plate is released. In addition, the thicker the steel plate thickness, the higher the initial stacking temperature, and the slower the heat dissipation, the longer the stacking time required. Considering that the logistics of the steel plates on site is smooth and the operation is convenient, the slow cooling time of the steel plate stacks is set to be more than or equal to 24h and more than or equal to 48h, and the slow cooling natural aging time of the steel plate stacks with different specifications is set respectively.
The higher the initial surface temperature of the steel plate stack is, the longer the required stack slow cooling time is, the thicker the steel plate is, the lower the temperature drop speed is, and the correspondingly longer the required stack slow cooling aging time is, so in the formula of the natural aging time of the stack, the temperature and the thickness are set on the denominator, and for different thicknesses, the parameters are h/65, h/90 and h/90 respectively, which mainly reflect the proportion of the steel plate with the thickness to the steel plate with the maximum thickness in the use range of the formula (the thicker the thickness is, the larger the calculated proportion is, and the correspondingly larger the slow cooling time is); since the surface temperature of the steel plate in the second stage is all cooled to be below 150 ℃, the parameters are all t/150 and represent the ratio of the surface temperature to the unstacking temperature (the higher the temperature is, the larger the calculated ratio is, the larger the slow cooling time is).
The inventor researches and discovers that whether the TMCP process or the non-TMCP process is adopted, in the formula of the natural aging time of the stack slow cooling, the surface temperature of the steel plate at the start of the stack is limited within a narrow range (the difference between the maximum temperature and the minimum temperature is within 100 ℃), the thickness of the steel plate is also limited within a narrow range (the difference between the maximum thickness and the minimum thickness of the non-TMCP process is within 25 mm; and the difference between the maximum thickness and the minimum thickness of the TMCP process is within 50 mm), and the thickness and the surface temperature of the steel plate at the start of the stack are reflected in the formula, so that the natural aging time can be more accurate.
The higher the surface temperature of the steel plate at the beginning of stacking, the higher the thermal stress, in order to fully release the thermal stress, the longer the slow cooling time of the stacking is needed, the influence of the thickness, the temperature difference exists between the core part and the surface temperature, the temperature drop is slow, the influence of the thickness is caused by the target of temperature reduction, the influence of the thickness on the slow cooling time of the stacking is more indirect and relatively complex than the influence of the temperature, and therefore, the coefficient is given in the front of the thickness term. (h/65) 2 、(h/90) 2 The square of the thickness proportion can reduce the influence of the thickness on the slow cooling time of the stack, so that the time is more accurate, and the over-aging and the insufficient aging are avoided.
In the fitting process of the formula in the second stage, a large amount of data including the thickness h of the steel plate, the stacking starting surface temperature T of the steel plate and the optimal aging time T are input. The optimal aging time is determined by determining the quantity of end points in a batch experiment, and the optimal aging time is determined according to the effect of improving the yield of the tensile property of the steel plate in different processes, different thicknesses and different temperatures. Thus, the coefficient of the foremost coefficient of the formula and the coefficient of the thickness term are determined, and the aging time formula of the second stage of different processes and thicknesses is obtained.
The third stage is a natural aging stage after the preparation of the sample. For steel plates produced by a non-TMCP process, the natural aging time of steel plate samples produced by different production processes and different specifications is different, and the natural aging time of the samples is in fact greatly related to the sample preparation method, because the final cooling temperature of the steel plates produced by the non-TMCP process is higher, generally 600-700 ℃, the temperature gradient of the steel plates from the surface layer to the core part is large, the tissue uniformity is poor, and the tissue stress is larger.
The steel plate produced by the non-TMCP process has the advantages that the tensile property detection sample is a circular sample, the diameter of the parallel section of the circular sample is (10 +/-0.07) mm, the center line of the sample coincides with the thickness of the steel plate at 1/4, a straight line exists from top to bottom in the thickness direction of the steel plate, the structure and the grain size in the upper direction and the lower direction of the straight line are not uniformly distributed at a certain point of the straight line, the structure and the grain size in the left direction and the right direction of the straight line are uniformly distributed, namely, the structure and the grain size in the thickness direction of the steel plate are not uniformly distributed, and the structure and the grain size in the width direction of the steel plate are uniformly distributed.
In this case, when the thickness h of the steel sheet is 40. Ltoreq 1 When the thickness is less than or equal to 65mm, the cross section of the circular sample accounts for 15.38-25% of the total thickness in the thickness direction, and when the thickness h of the steel plate is more than 65% 2 When the diameter is less than or equal to 90mm, the proportion of the cross section of the circular sample diameter to the total thickness in the thickness direction is 11.11-15.38%. That is, when the thickness h of the steel sheet is 40. Ltoreq 1 When the thickness is less than or equal to 65mm, the difference of the tissues on the section of the circular sample is more than 65 and the thickness h of the steel plate 2 Larger when less than or equal to 90mm, and larger tissue stress.
In this case, for the steel sheet produced by the non-TMCP process, the thickness h of the steel sheet is not less than 40 ≤ 1 When the thickness is less than or equal to 65mm, the longer time of natural aging of the sample is more appropriate to be 48-72 h. When the thickness of the steel plate is more than 65 h 2 When the thickness is less than or equal to 90mm, the natural aging time of the sample is shorter and is more appropriate to be 36-48 h.
Although the anisotropy of the round sample is small, due to obvious tissue difference and stress concentration, in order to fully release the tissue stress, the invention adopts a mode that the sample is naturally placed and aged for a period of time after being prepared to eliminate unstable factors of the tensile test caused by the tissue stress and the surface layer work hardening.
It should be noted that, due to the limitation of the capability of the equipment, the operations of cutting the head, cutting the tail, cutting the edge, sampling and the like of the steel plate with the thickness of more than or equal to 40mm are all completed under the manual flame cutting, and are limited by site factors, for example, the operations of cutting the head, cutting the tail, cutting the edge, sampling and the like are obviously unrealistic after the steel plate after the stacking and slow cooling is performed for a period of time, so that the production logistics of the steel plate with the thick specification at the later stage can be seriously influenced. If the operations such as head cutting, tail cutting, edge cutting, sampling and the like are performed on the steel plate, the steel plate can be transferred to a warehouse for stacking, and meanwhile, the sample is sent to be processed. On the other hand, since the structural stress of the steel sheet is always present, the surface layer work hardening is mainly generated during the sample preparation. Therefore, in the first to fourth stages, in order to improve the initial inspection performance yield of the tensile test specimen, sampling and sample preparation operations are performed, and then the test specimen and the steel plate are naturally aged for a certain time to keep the state consistency of the test specimen and the steel plate.
Furthermore, in the third stage, the steel plate sample is prepared in a natural aging stage, and the natural aging time of the steel plate samples prepared by different production processes is different. The steel plate produced by the TMCP process has lower final cooling temperature, which is generally between 500 and 600 ℃. The steel plate has small temperature gradient from the surface layer to the core part, good tissue uniformity and small tissue stress. In the steel plate produced by the TMCP process, the processing mode of the tensile sample is a rectangular sample, the width of the sample is (25 +/-0.5) mm, the thickness of the sample is half thickness including the upper surface of the steel plate, the cross section area of the rectangular sample is large, the stress is relatively dispersed, and the tissue difference is relatively small, so the tissue stress is relatively small, and the natural aging time of the sample is relatively proper to be 24-36 h.
When the thickness of the steel plate produced by the non-TMCP process is less than or equal to 40h 1 When the thickness is less than or equal to 65mm, the surface of the round sample is subjected to cutting action in the sample preparation process, and the surface layer is processed and hardened on the whole surface; in addition, the structure stress of a round sample made of the steel plate in the thickness range is large, the natural aging time of the sample is long, the coefficient in the front of the formula is also large, and the coefficient in the front of the formula at the stage is taken as 3.
When the thickness of the steel plate produced by the non-TMCP process is more than 65 h 2 When the thickness is less than or equal to 90mm, the surface of the round sample is subjected to cutting action in the sample preparation process, and the surface layer is processed and hardened on the whole surface; in addition, the structural stress of the round specimens made of steel plates in this thickness rangeThe natural aging time of the sample is relatively short, the coefficient in the front of the formula is also small, and the coefficient in the front of the formula at the stage is 2.2.
When the thickness h of the steel plate produced by the TMCP process is more than or equal to 40 ≤ 3 When the thickness is less than or equal to 90mm, the surface of the rectangular sample is not subjected to cutting action in the sample preparation process, and only two adjacent side surfaces are subjected to turn-milling processing; in addition, the structural stress of a rectangular sample made of the steel plate in the thickness range is minimum, the natural aging time of the sample is relatively minimum, the coefficient in the front of the formula is also minimum, and the coefficient in the front of the formula in the stage is 1.6.
The larger the required elongation is, the longer the aging time is, and for the steel plate produced by the non-TMCP process, the smaller the thickness of the steel plate is, the larger the proportion of the diameter of the circular test sample in the total length in the thickness direction is, the longer the time is required, 10 represents the diameter of the test sample, h is smaller, h is divided by 10 to be smaller, the front is provided with a minus sign, and the more the time is required. However, the inventor researches and discovers that although the thickness has a certain influence on the time efficiency, the influence of the thickness is within a range, so that the influence of the thickness can be reduced by multiplying the formula by 1/2 after the formula is set.
For the steel plate produced by the TMCP process, the thickness of the test sample is half thickness containing the upper surface of the steel plate, the cross section area of the rectangular test sample is large, the stress is relatively dispersed, and the tissue difference is small, so that the larger the thickness is, the shorter the required time is, and the negative sign is arranged in front of the thickness.
In the embodiment of the application, in a preferred scheme, the natural aging time of the steel plate in the second stage in a lower-line stacking slow cooling mode is a range value, and the natural standing aging time of the initial test sample and the slit steel plate in the third stage is a point value. In the second stage, the steel plates which are stacked and slowly cooled off the line have different natural aging time due to different processes, thicknesses and temperatures, and in addition, the process of unstacking the steel plates comprises the processes of head cutting, tail cutting, edge cutting, sampling and the like, and needs a period of time and cannot be completed simultaneously, so the natural aging time of the steel plates in the second stage in the mode of stacking and slowly cooling off the line is a range value. In the third stage, the tensile test of the sample is continuously operated and can be completed in a short time, so the aging time of the initial test sample and the slit steel plate in the third stage after natural placement can be set to be a point value.
The above invention and the mechanism analysis are only briefly analyzed macroscopically, and are briefly analyzed microscopically hereinafter.
The yield of tensile properties can be increased after the samples and the steel sheets corresponding to the samples are naturally aged for the following reasons: in a natural state of the sample, supersaturated solute carbon in alpha-Fe is gradually precipitated from supersaturated solid solution in alpha-Fe under the action of concentration gradient along with the prolonging of time, and finally transformed into ferrite with carbon solubility of 0.008% at room temperature, and on the other hand, along with the disappearance of supersaturated solid solution in alpha-Fe and the formation of ferrite, the internal stress of carbon steel is eliminated, so that the brittleness of the carbon steel is reduced, and the plasticity and the toughness are improved. During the stretching process of the sample, the stress-strain curve has an obvious yield platform, and the most direct embodiment is that the elongation rate is obviously improved, and the yield strength and the tensile strength are reduced and tend to be stable. In addition, the degree of segregation in the band-shaped structure can be reduced even after the sample is aged.
In the fourth stage, the artificial aging stage is performed. The stage is a supplement to the previous stage, and if the initial test of the tensile property of the sample is unqualified, a plurality of sub-steel plates corresponding to the unqualified sample need to be subjected to artificial aging, so that the structural stress of the steel plate is further eliminated. In the actual operation process, the temperature of the artificial aging of the steel plate is not too high, one round of artificial aging time is considered for 8 hours, in addition, for the convenience of operation, the steel plate is subjected to heating treatment in the same furnace, the temperature of the artificial aging is the same and is 175-185 ℃, the heating time is 5.5-6.5 hours, for all the artificially aged steel plates, after the artificial aging is finished, the steel plates are placed in the air to be naturally cooled to the room temperature, sampling is carried out according to the standard GB/T2975, rechecking samples are processed, and the tensile test is carried out on the rechecking samples.
In the fourth stage, after the steel plate is artificially aged, the structural stress of the steel plate is basically and completely eliminated, and the yield of the tensile property of the steel plate is higher and can reach 99.9 percent.
The present application is further illustrated by the following examples.
Examples
Table 1 shows the specific steps of the treatment method for improving the yield of the tensile property of the steel plate:
TABLE 1 treatment method for improving the percent of pass of steel plate tensile properties
It should be noted that: in table 1, it is not necessary that each type of steel sheet is processed through the above four stages. For the data in the comparative example, only the first and second stages of treatment were performed, and after completion of the treatment, the tensile properties of the test specimens were directly examined.
For the data in the embodiment, after the first stage, the second stage and the third stage of processing, 1 initial test sample is detected, and after the detection is qualified, the fourth stage of processing is not needed; and if the detection is not qualified, performing treatment in a fourth stage, and taking 2 recheck samples after the treatment to detect the tensile property.
The data of the comparative examples and examples obtained after examination are shown in Table 2.
TABLE 2 tensile Properties of the Steel sheets
As can be seen from Table 2, the Q235B steel plate produced by the non-TMCP process has the elongation of both sample 1 and sample 2 after the first and second stages of treatment; the tensile strength and the elongation of the sample 3 are both not qualified; the tensile properties of samples 4 to 8 were all acceptable. After the first to third treatments, all of the tensile properties of samples 1 to 8 were acceptable.
After the steel plate with the mark S275J0 produced by the non-TMCP process is processed in the first stage and the second stage, the elongation rates of the sample 10, the sample 11 and the sample 12 are all not qualified; all of the tensile properties of sample 9 and samples 13 to 16 were acceptable. After the first to third stages of treatment, the tensile properties of samples 9 to 16 were all acceptable.
The sample 17, a steel plate of the type S355J0 produced by the non-TMCP process, after the first and second stages of treatment, has unqualified elongation; the tensile strength of both sample 18 and sample 20 was not acceptable; all of the tensile properties of sample 19 and samples 21 to 23 were acceptable. After the first to third treatments, all of the tensile properties of samples 17 to 23 were acceptable.
After the Q355B steel plate produced by the non-TMCP process is subjected to the first stage and the second stage, the elongation of the samples 24, 25 and 26 is not qualified; sample 28 failed in tensile strength; all of the tensile properties of sample 27 and samples 29 to 31 were acceptable. After the first to third stages of treatment, the tensile properties of samples 24, 25, 27 to 31 were all acceptable; sample 26 failed to elongate. After the first to fourth stages of treatment, the tensile properties of both samples of sample 26 were acceptable.
After the Q390B steel plate produced by the non-TMCP process is processed in the first stage and the second stage, the elongation of the samples 33 and 34 is not qualified; the tensile strength of sample 36 was not acceptable; the tensile properties of samples 32, 35, 37 were all acceptable. After the first to third stages of treatment, the tensile properties of samples 32 to 37 were all acceptable.
After the Q345GJB steel plate produced by the non-TMCP process is processed in the first stage and the second stage, the elongation of the sample 39 is not qualified; samples 40 and 43 all failed in yield strength, tensile strength and elongation; sample 41 failed in yield strength; the tensile properties of samples 38, 42 and 44 were all acceptable. After the first to third stages of treatment, the tensile properties of samples 38, 41 to 44 were all acceptable; the yield strength and tensile strength of sample 39 were both not acceptable; the yield strength of sample 40 failed. After the first to fourth stages of treatment, the tensile properties of both samples 39 and 40 were acceptable.
After the Q345qC steel plate produced by the non-TMCP process is processed in the first stage and the second stage, the elongation of the sample 46 is not qualified; all of the tensile properties of samples 45 and 47 to 50 were acceptable. After the first to third stages of treatment, the tensile properties of samples 45 to 50 were all acceptable.
After the Q420MC steel plate produced by the TMCP process is processed in the first stage and the second stage, the tensile strength and the elongation of the samples 51 and 52 are not qualified; sample 53 failed in tensile strength; the elongation of samples 55 and 56 was not acceptable; the tensile properties of sample 54 were all acceptable. After the first to third stages of treatment, all of the tensile properties of samples 51 to 56 were acceptable.
After the Q460MC steel plate produced by the TMCP process is processed in the first stage and the second stage, the elongation of the sample 58 is not qualified; all of the tensile properties of samples 57 and 59 to 62 were acceptable. After the first to third stages of treatment, all of the tensile properties of samples 57 to 62 were acceptable.
After the Q420qD steel plate produced by the TMCP process is processed in the first stage and the second stage, the elongation of the sample 64 is not qualified; all of samples 63 and 65 to 68 were acceptable in tensile properties. After the first to third treatments, all of the tensile properties of samples 63 to 68 were acceptable.
After the first stage and the second stage of treatment, the elongation of the sample 70 and 74 of the S460M steel plate produced by the TMCP process is not qualified; all of the tensile properties of samples 69 and 71 to 73 were acceptable. After the first to third stages of treatment, the tensile properties of samples 69, 71 to 74 were all acceptable; the elongation of sample 70 failed. After the first to fourth stages of treatment, the tensile properties of both samples of the sample 70 were acceptable.
After the first to third stages of treatment, the yield of the tensile property of the steel plate is improved; and for the steel plate with unqualified tensile property, after the fourth stage treatment is continuously carried out, the yield of the tensile property of the steel plate is further improved.
From the above, it can be seen that the steel sheet performance is represented by the phenomena of higher yield strength or/and tensile strength and lower elongation without the aging treatment provided by the present application. Particularly, compared with steel plates with the same strength grade, such as Q355B and Q345qC, the high-construction plate, such as Q345GJB, has relatively high standard required elongation, and has upper limit requirements on yield strength and tensile strength.
The embodiments described above are some, but not all embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments in the present application without making any creative effort belong to the protection scope of the present application.
Claims (2)
1. A processing method for improving the qualified rate of the tensile property of a steel plate is characterized in that,
if the steel plate is a first steel plate produced by a non-thermomechanical rolling process, the thickness of the first steel plate is h 1 And is not less than 40h 1 ≦ 65mm, the treatment method comprising:
the first stage is as follows: cooling the first steel plate on a cooling bed until the surface temperature is 350-450 ℃;
and a second stage: for the first steel platePerforming natural aging in a manner of slow cooling by a following-line stacking, wherein the surface temperature of the first steel plate is 350-450 ℃ at the beginning of stacking, and the natural aging time T 1 When the surface temperature of the first steel plate is less than or equal to 150 ℃, slitting the first steel plate to obtain a plurality of first sub-steel plates, sampling and processing a first circular initial test sample; t is a unit of 1 The following relationship is satisfied: 18+10 × (h) 1 /65) 2 +t 1 /150≤T 1 ≤18+27×(h 1 /65) 2 +t 1 150; wherein h is 1 Represents the thickness of the first steel plate in mm; t is t 1 The surface temperature, expressed in units of degrees c, at the start of the first steel plate stack; t is 1 The unit of the natural aging time is h;
and a third stage: subjecting the first circular initial detection sample and the plurality of first sub-steel plates corresponding to the first circular initial detection sample to natural aging time T 2 The tensile property of the first round initial test sample after natural aging is detected for 48-72 hours; t is 2 The following relationship is satisfied: t is 2 =3 × (elongation-1/2 × SQRT (h) 1 10)); wherein h is 1 Represents the thickness of the first steel plate in mm; t is 2 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the required elongation of the first steel plate standard;
if the steel plate is a second steel plate produced by a non-thermomechanical rolling process, the thickness of the second steel plate is h 2 And 65 < h 2 ≦ 90mm, the treatment method comprising:
the first stage is as follows: cooling the second steel plate on a cooling bed until the surface temperature is 450-550 ℃;
and a second stage: naturally aging the second steel plate in a way of slow cooling of a lower-line stack, wherein the surface temperature of the second steel plate is 450-550 ℃ at the beginning of the stack, and the natural aging time T is 3 When the surface temperature of the second steel plate is less than or equal to 150 ℃, slitting the second steel plate to obtain a plurality of second sub-steel plates, sampling and processing a second circular initial test sample; t is 3 The following relationship is satisfied: 40+10 × (h) 2 /90) 2 +t 2 /150≤T 3 ≤40+28×(h 2 /90) 2 +t 2 150; wherein h is 2 Represents the thickness of the second steel plate in mm; t is t 2 Surface temperature, expressed in units of ° c, at the start of the second steel plate stack; t is 3 The unit of the natural aging time is h;
and a third stage: subjecting the second circular initial test sample and a plurality of second sub-steel plates corresponding to the second circular initial test sample to natural aging time T 4 The tensile property of the second round initial test sample after natural aging is detected for 36-48 h; t is 4 =2.2 × (elongation-1/2 × SQRT (h) 2 10)); wherein h is 2 Represents the thickness of the second steel plate in mm; t is a unit of 4 The natural aging time is expressed in the unit of h; the elongation represents the absolute value of the minimum value of the required elongation of the second steel plate standard;
if the steel plate is a third steel plate produced by a thermomechanical rolling process, the thickness of the third steel plate is h 3 And is not less than 40h 3 ≦ 90mm, the treatment method comprising:
the first stage is as follows: cooling the third steel plate on a cooling bed until the surface temperature is 300-400 ℃;
and a second stage: naturally aging the third steel plate in a manner of slow cooling by a lower-line stacking, wherein the surface temperature of the third steel plate is 300-400 ℃ when the stacking is started, and the natural aging time T is 5 When the surface temperature of the third steel plate is less than or equal to 150 ℃, slitting the third steel plate to obtain a plurality of third sub-steel plates, sampling and processing a rectangular initial test sample; t is a unit of 5 The following relationship is satisfied: 22+5 × (h) 3 /90) 2 +t 3 /150≤T 5 ≤22+23×(h 3 /90) 2 +t 3 150; wherein h is 3 Represents the thickness of the third steel plate in mm; t is t 3 Surface temperature, expressed in units of c, at the start of the third steel plate stack; t is a unit of 5 The unit of the natural aging time is h;
and a third stage: subjecting the rectangular initial test sample and a plurality of third sub-steel plates corresponding to the rectangular initial test sample to natural aging time T 6 Detecting natural aging for 24-36 hThe tensile property of the rectangular initial test sample is measured; t is 6 The following relationship is satisfied: t is a unit of 6 =1.6 × (elongation-1/2 × SQRT (h) 3 10)); wherein h is 3 Represents the thickness of the third steel plate in mm; t is 6 The unit of the natural aging time is h; the elongation represents the absolute value of the minimum value of the required elongation of the third steel sheet standard.
2. The processing method according to claim 1, wherein if the tensile property test of the initial test specimen after natural aging fails, the processing method further comprises:
a fourth stage: and (3) carrying out artificial aging on a plurality of sub steel plates corresponding to the initial test sample, preserving the heat for 5.5-6.5 h at the temperature of 175-185 ℃, then naturally cooling in the air, sampling and processing a reinspection sample, and detecting the tensile property of the reinspection sample.
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