CN111766152B  Method for obtaining stress parameters of steel plate for pipe making and steel plate selecting method  Google Patents
Method for obtaining stress parameters of steel plate for pipe making and steel plate selecting method Download PDFInfo
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 CN111766152B CN111766152B CN202010817943.9A CN202010817943A CN111766152B CN 111766152 B CN111766152 B CN 111766152B CN 202010817943 A CN202010817943 A CN 202010817943A CN 111766152 B CN111766152 B CN 111766152B
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Abstract
The invention belongs to the technical field of steel pipe preparation, relates to a method for obtaining stress parameters of a steel plate for pipe making and a steel plate selecting method, and aims to solve the problem that a steel pipe manufactured by a steel plate selected based on a stress standard value does not meet the requirements; the method for obtaining the stress parameters of the steel plate for manufacturing the pipe comprises the steps of obtaining the average strain of the steel pipe to be manufactured; selecting N steel plate samples to obtain M groups of strain values and N steel plate stress values corresponding to the same strain value of each group; selecting N steel plate samples to prepare N steel pipe samples, and obtaining yield strength values of the steel pipe samples when the strain value is delta epsilon; performing straight line fitting on the steel plate stress value and the yield strength value, and obtaining a steel plate strain value corresponding to the maximum fitting goodness as a characterization parameter of the steel plate stress value; based on actual measurement of R in steel pipe _{tΔx} Fitting R with steel pipe _{tΔx} Obtaining stress value R corresponding to the corrected characterization parameter _{tx} The steel pipe manufactured by the steel plate with the stress parameter selected in the invention meets the process requirements.
Description
Technical Field
The invention belongs to the technical field of steel pipe preparation, and particularly relates to a method for obtaining stress parameters of a steel plate for pipe making and a steel plate selecting method.
Background
The pipeline is used as a highefficiency and economic conveying mode and is a main mode for longdistance conveying of petroleum and natural gas. At present, oil and gas pipelines such as Western gas east transportation pipelines, western gas east transportation two/three/four lines, china Russian crude oil pipelines, china Asian pipelines, china Burma pipelines and the like are built in China for more than 12 ten thousand kilometers, but still the requirement of rapid increase of oil and gas requirements of China can not be met, and the construction of the oil and gas pipelines is still in a stage of rapid development. The raw material of the longitudinal submerged arc welded pipe of the oil and gas pipeline is a hot rolled wide and thick plate, and the main pipe making process comprises the steps of prebending, forming, welding, mechanical expanding, hydrostatic pressure and the like. In the process of pipe making, the shaping and expanding procedures lead the material to generate certain shaping deformation, so that the tensile property, especially the yield strength, of the material is greatly changed. Therefore, the tensile properties of the steel plate need to be determined according to the tensile property index of the steel pipe and the tensile property change condition in the pipe making process, rather than the standard value.
Because the change of the tensile property (mainly the yield strength and the yield ratio) of the material in the pipe making process is influenced by the characteristics of the material, the steel grade, the diameter of the steel pipe, the wall thickness, the forming and expanding parameters and other factors, difficulty often exists in determining the tensile property index of the steel plate, and an index range is generally set according to experience. And such problems often occur during the production inspection of steel and steel pipes: firstly, the tensile property of the steel plate meets the required range, but the tensile property of the steel pipe after pipe making is unqualified; secondly, the tensile property of the steel plate does not meet the required range, but the tensile property of the steel pipe after the pipe is manufactured is qualified. Because the tensile property index is required to be inaccurate, the control of steel factories and pipe factories is difficult. Judging and process adjustment are carried out on the manufactured steel plates according to the tensile property requirements of the steel plates put forward by ordering, and judging waste of the steel plates which do not meet the steel plate requirements but possibly meet the requirements after pipe making can occur, or the steel plates which meet the steel plate requirements but are unqualified after pipe making are sent out according to qualified products; because the sampling inspection is carried out according to batches in the pipe making process, the situation also causes the risk of sending out unqualified products, and the risk and the challenge are brought to the safety of the pipeline.
Therefore, the method for accurately determining the tensile property requirement of the steel plate and predicting the tensile property of the steel plate after pipe making according to the tensile property requirement of the steel plate has very important significance for improving the manufacturing level and the product quality and the qualification rate.
Disclosure of Invention
In order to solve the problems in the prior art, namely the problem that a steel pipe manufactured by a steel plate selected based on a stress standard value in the prior art does not meet the yield strength requirement, the invention provides a method for acquiring stress parameters of the steel plate for manufacturing a pipe and a steel plate selecting method.
The first aspect of the invention provides a method for obtaining stress parameters of a steel plate for pipe making, comprising the following steps: step S100, based on the diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining the average stress of the steel pipe to be preparedChanging epsilon _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube;
step S200, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, and respectively obtaining stressstrain curves of the N corresponding steel plate samples through a tensile test; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plate stress values corresponding to different strain values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared;
Step S300, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, respectively preparing N steel pipe samples according to parameters of the steel pipe to be prepared, obtaining a stress strain curve and delta epsilon of the steel pipe samples through a tensile test, and obtaining yield strength values of the N steel pipe samples corresponding to the delta epsilon of the strain value;
step S400, obtaining a steel plate stress value corresponding to the fitting goodness with the largest value as a characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same stress value and the yield strength values of the N steel pipe samples corresponding to the same stress value when the stress value is delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein R is 100 times of the strain value of the steel plate to be selected _{tx} For the stress value corresponding to the total deformation epsilon on the tensile stress strain curve, delta _{x} ＝100Δε；
S500, obtaining a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} ；
1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range of
2) When DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range of
3) When N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of
In some preferred embodiments, Δε is 0.5%.
In some preferred embodiments, the steel plate sample in step S200 is a transverse sampling sample.
In some preferred embodiments, the selection position of the steel pipe sample in step S300 coincides with the selection position of the steel plate sample.
In some preferred embodiments, the "stress at each corresponding" in step S200 should beRespectively with epsilon in the variate curve _{1} The method for obtaining M steel plate stress values corresponding to different strain values by selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard comprises the following steps: based on the set interval a, at ε _{1} The +Deltaepsilon is taken as the center and is taken at the left and the right sides The strain values are used for obtaining M corresponding steel plate stress values; wherein a > 0; m is an odd number; />
In some preferred embodiments, the method for obtaining the goodness of fit of the steel plate and the steel pipe in step S400 is as follows:
wherein ,x_{i} Is the stress value variable of the steel plate, y _{i} Is the variable of the yield strength value of the steel pipe, < >>Stress average value corresponding to the same strain value of N steel plates,/>The average value of the yield strengths of the N steel pipes is given.
In some preferred embodiments, the method further comprises a step S410 of based on ε _{1} Setting the characteristic strain delta epsilon corresponding to the yield strength of the steel pipe and compensating the deformation epsilon _{2} Obtaining theoretical strain value epsilon=epsilon of steel plate _{1} +ε _{2} +Δε; wherein epsilon when delta epsilon=0.5% _{2} The value range is as follows: 0 < epsilon _{2} Less than or equal to 1.0 percent; the value range of epsilon is as follows: epsilon is more than 0.5 percent and less than or equal to 5 percent; epsilon when delta epsilon=0.2% _{2} The value range is as follows: 0 < epsilon _{2} Less than or equal to 1.0 percent, and the value range of epsilon is as follows: epsilon is more than 0.2 percent and less than or equal to 5 percent;
judging whether the theoretical strain value epsilon of the steel plate and the strain value of the steel plate corresponding to the maximum fitting goodness are consistent or not based on the obtained theoretical strain value epsilon of the steel plate;
if the strain values are consistent, taking the strain values of the steel plates as standard parameters; if not, step S420 is performed.
In some preferred embodiments, step S420, based on the theoretical strain value epsilon of the steel plate, combines the tensile stress strain curve of the steel pipe to be manufactured to obtain the range of the theoretical stress value epsilon of the steel plate; acquiring a steel plate test stress value range based on the steel plate strain value corresponding to the maximum fitting goodness;
Judging whether the range of the theoretical stress value of the steel plate falls into the range of the experimental stress value of the steel plate; if m is greater than or equal to delta _{1} And n is less than or equal to delta _{2} Delta is then _{1} ≤R _{tx} ≤δ _{2} As stress parameters of steel plates for pipe making;
wherein m is the lower limit value of the theoretical stress value of the steel plate, and n is the upper limit value of the theoretical stress value of the steel plate; delta _{1} For the lower limit value, delta, of the test stress value range of the steel plate _{2} The upper limit value of the stress value range is tested for the steel plate.
In some preferred embodiments, when Δε=0.5%, ε can be in the range of: epsilon is more than 0.5 percent and less than or equal to 5 percent; when Δε=0.2%, the value range of ε is: epsilon is more than 0.2 percent and less than or equal to 5 percent.
A method of selecting a steel sheet, the method comprising the steps of: step S100, based on the diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining the average strain epsilon of the steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube;
step S200, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, and respectively obtaining stressstrain curves of the N corresponding steel plate samples through a tensile test; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plates corresponding to different strain valuesStress values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared;
step S300, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, respectively preparing N steel pipe samples according to parameters of the steel pipe to be prepared, obtaining a stress strain curve and delta epsilon of the steel pipe samples through a tensile test, and obtaining yield strength values of the N steel pipe samples corresponding to the delta epsilon of the strain value;
step S400, obtaining a steel plate stress value corresponding to the fitting goodness with the largest value as a characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same stress value and the yield strength values of the N steel pipe samples corresponding to the same stress value when the stress value is delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the strain value of the steel plate, R _{tx} Namely, the stress value corresponding to the total deformation epsilon on the tensile stress strain curve is expressed as deltax=100 deltaepsilon;
s500, obtaining a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range of 2) When DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range of 3) When N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
Step S600, based on the corrected stress value R corresponding to the characterization parameter _{tε} And selecting the corresponding steel plate of the steel pipe to be prepared, and preparing the steel pipe to be prepared.
The beneficial effects of the invention are as follows:
1) By the method for acquiring the stress parameters of the steel plate for manufacturing the pipe, the safety margin adjustment and correction are carried out on the stress value range corresponding to the steel plate strain value obtained by fitting a straight line formula, and the stress value R corresponding to the corrected characterization parameter is adopted _{tx} The range (namely that the total strain on the tensile stress strain curve is a stress value corresponding to epsilon, wherein x is 100 times of epsilon) is used as a stress selection standard of the steel plate of the steel pipe to be prepared, and the selection precision of the steel plate of the steel pipe to be prepared is improved.
2) The invention breaks the traditional rule R about yield strength according to the domestic and foreign general standards _{t0.5} (stress corresponding to 0.5% of total strain is taken as steel plate yield strength) or R _{p0.2} (0.2% in residual deformation)The corresponding stress is used as the yield strength), and the method of determining the yield strength of the steel plate for manufacturing the pipe adopts epsilon of more than 0.5 percent (when the stress corresponding to 0.5 percent of total strain is used as the yield strength of the steel plate) or epsilon of more than 0.2 percent (when the stress corresponding to 0.2 percent of residual deformation is used as the yield strength) as a selection standard for the first time, and provides a new judgment standard, thereby having great significance for manufacturing and selecting the steel plate in the field.
3) The steel plate stress value obtained by the step in the method for obtaining the steel plate stress parameter for pipe production in the invention is used as the characterization parameter, namely R _{tx} (i.e., the total strain on the tensile stress strain curve is a stress value corresponding to ε, where x is 100 times ε) instead of R _{t0.5} The steel plate with the tensile property of the steel pipe is selected, so that the defects of large stress change and inconsistent change rule around 0.5% of total strain on a stress strain curve can be effectively overcome, and the tested stress result is more stable; wherein R is _{tx} Refers to the stress value corresponding to the total strain epsilon on the tensile curve.
4) The steel plate stress value as the characterization parameter obtained through the steps of the steel plate stress parameter obtaining method for pipe production provided by the invention is namely R _{tx} Substitute R _{t0.5} Taking the material stress strain curve deviation caused by deformation in the steel plate pipe making process into consideration, so that the obtained steel plate stress value R _{tx} Yield strength value R of steel pipe _{t0.5} More closely.
5) The steel plate stress value R which is obtained by the steps of the steel plate stress parameter obtaining method for pipe production and is taken as the characterization parameter _{tx} Yield strength value R of steel pipe _{t0.5} The method is closer to, has stronger regularity, can more accurately determine the tensile property requirement of the steel plate, and improves the tensile property qualification rate of the steel plate and the steel pipe.
6) The steel plate stress value serving as the characterization parameter is obtained through the steps of the steel plate stress parameter obtaining method for manufacturing the pipe, and the steel plate stress value R obtained after correction and optimization is obtained _{tx} The strength of the steel pipe after pipe making can be predicted more accurately.
7) The steel plate stress parameter for pipe making is obtained by the inventionThe steel plate stress value obtained by the steps of the method is closer to the set yield strength value of the steel pipe and has stronger regularity, and the steel pipe fitting R corresponding to the maximum fitting goodness is further obtained by a fitting formula _{t0.5} Actually measured R of steel pipe obtained by actually measuring _{t0.5} By DeltaR _{t0.5} =actual measurement of steel tube R _{t0.5} Fitting R to Steel pipe _{t0.5} According to the obtained N R corresponding to the measured values of the yield strength of the N steel pipes and the fitting calculated values of the yield strength of the steel pipes _{t0.5} The method has the advantages that the optimization and correction of the stress range of the steel plate obtained by the test are carried out, the corrected stress value range of the steel plate is used as a selection standard of the steel pipe to be prepared, great guiding significance is provided for adjusting the manufacturing process of the steel plate, the steel plate qualification rate is improved, the steel plate performance interval can be further optimized, and the performance consistency of the steel plate and the steel pipe is improved.
8) The invention corrects the stress range corresponding to the characterization parameter, and takes the corrected stress value range of the steel plate as the selection standard of the steel plate corresponding to the steel pipe, thereby having the advantages of high precision and high reliability. In addition, the optimization method for deducing the range of the stress value corresponding to the steel plate directly according to the internal control standard of the steel pipe to be prepared has the advantages of being quick in judgment, simple and efficient, and provides great guiding significance for selecting the steel plate based on setting the tensile property parameters of the steel pipe.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of nonlimiting embodiments, made with reference to the following drawings, in which:
FIG. 1 is a first fitted line graph of steel sheet stress values and steel tube yield strength values for a first specific example of a method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 2 is a second fitted line graph of steel sheet stress values and steel tube yield strength values for a first specific example of a method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 3 is a third fitted line graph of steel sheet stress values and steel tube yield strength values for a first specific example of the method of obtaining steel sheet stress parameters for pipe making according to the present invention;
FIG. 4 is a fourth fitted line graph of steel sheet stress values and steel tube yield strength values for a first specific example of the method of obtaining steel sheet stress parameters for pipe making according to the present invention;
FIG. 5 is a fifth fitted line graph of steel sheet stress values and steel tube yield strength values for a first specific example of a method of obtaining steel sheet stress parameters for pipe making according to the present invention;
FIG. 6 is a first fitted line graph of steel sheet stress values and steel tube yield strength values for a second specific example of a method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 7 is a second fitted line graph of steel sheet stress values and steel tube yield strength values for a second specific example of the method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 8 is a third fitted line graph of steel sheet stress values and steel tube yield strength values for a second specific example of the method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 9 is a fourth fitted line graph of steel sheet stress values and steel tube yield strength values for a second specific example of the method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 10 is a fifth fitted line graph of steel sheet stress values and steel tube yield strength values for a second specific example of the method of obtaining steel sheet stress parameters for pipe making in the present invention;
FIG. 11 is a schematic view of a first form of a typical stressstrain curve of a steel sheet or a steel pipe in the method for obtaining a steel sheet stress parameter for pipe production according to the present invention;
FIG. 12 is a schematic view of a second form of typical stressstrain curves of steel sheets and steel pipes in the method for obtaining stress parameters of steel sheets for pipe production according to the present invention;
FIG. 13 is a schematic view of a third form of typical stressstrain curves of steel sheets and steel pipes in the method for obtaining stress parameters of steel sheets for pipe production according to the present invention;
FIG. 14 is a schematic view showing the selection of different parameters of yield strength of steel plates and steel pipes in the invention.
Detailed Description
The preferred embodiments of the present invention will be described below with reference to the accompanying drawings, and it will be understood by those skilled in the art that these embodiments are merely for explaining the technical principles of the present invention, and are not intended to limit the scope of the present invention.
The invention provides a method for obtaining stress parameters of a steel plate for manufacturing a pipe, which comprises the following steps: step S100, based on the diameter D (outer diameter) of the steel pipe to be manufactured, the width W of the steel plate before forming, and the distance t from the center position of the tensile specimen to the outer surface of the steel pipe _{0} Obtaining average strain epsilon of steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} And t is the wall thickness of the steel tube.
Step S200, selecting N steel plate samples of which the steel pipes to be prepared correspond to the preset specifications, and respectively obtaining stressstrain curves of the N corresponding steel plate samples through a tensile test; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plate stress values corresponding to M different strain values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to M different strain values, taking the steel plate stress values corresponding to the same strain value as a group to obtain M groups of different strainstress corresponding values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared.
Step S300, selecting N steel plate samples of which the steel pipes to be prepared correspond to the preset specifications, respectively preparing N steel pipes according to the required parameters of the steel pipes to be prepared, taking tensile samples, obtaining stress strain curves and delta epsilon of the steel pipe samples through tests, and obtaining yield strength values of the N steel pipe samples corresponding to the delta epsilon of the strain values; in the process of manufacturing steel pipes from steel plates, the base metal steel plates are selected according to the determined tensile performance requirements of the steel pipes, in the invention, the yield strength values corresponding to the base metal steel plates of the same model are consistent after the base metal steel plates of the same batch and the same model are manufactured in theory, but in practice, even though the yield strength values corresponding to the base metal plates of the same batch and the same model are different on the tensile stress strain curves, in the step, N steel pipe yield strength values when the strain values take delta epsilon are obtained based on N steel pipe samples and the corresponding tensile stress strain curves, and the yield strength values of the steel pipe samples are equal to the yield strength of the steel pipes.
Step S400, obtaining M fitting straight lines of the relation between the steel pipe stress values corresponding to M different steel plate strain values and the steel pipe yield strength values through straight line fitting based on N steel plate stress values corresponding to the same strain value and the yield strength values of N steel pipe samples corresponding to the strain value delta epsilon, and calculating the fitting goodness of each fitting straight line, wherein the steel plate strain value corresponding to the fitting goodness with the largest value is the characterization parameter of the steel plate stress value; wherein each fitting straight line corresponds to a steel plate strain value; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔε} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the strain value of the steel plate, R _{tx} For the stress value corresponding to the total deformation epsilon on the tensile stress strain curve, deltax is 100 times the strain value corresponding to the yield strength of the steel pipe to be produced, i.e. deltax=100 deltaepsilon.
S500, obtaining a steel plate fitting stress value R through a steel plate fitting straight line formula and a steel pipe sample actual measurement value _{tx} Measured R of steel pipe sample _{tΔx} Wherein x=Δx; based on DeltaR _{tΔx} ＝R _{tΔx} R _{tx} Obtaining N delta R corresponding to N steel platesteel pipe samples _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} Maximum value of (2)As the upper limit value f of the safety margin, the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of2) When DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of +.>3) When N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
Preferably, Δε is 0.5%, and since the stress corresponding to a total deformation of 0.5% on the tensile stress strain curve is generally used as the yield strength, the present invention mainly uses this as the criterion for selecting the yield strength of the steel pipe to be produced.
Preferably, the steel plate sample in step S200 is a transverse sampling sample. For a sample piece with lower central strength than a part close to the surface, determining a half part of the center as a sampling position; for a sample piece with no obvious difference in performance in the length direction or the longitudinal direction, sampling can be performed at two ends; of course, longitudinal sampling may be employed according to practical needs, and the invention is not limited thereto.
Preferably, the selection position of the steel pipe sample in the step S300 is consistent with the selection position of the steel plate sample, and the selection positions are all the same end part in the steel plate, so as to reduce other accumulated errors of the steel plate in the test and the steel pipe after pipe making; specifically, the steel plate sample selection and the steel pipe sample selection in the invention can be sequentially selected at the set end parts of the N base metal steel plates so as to ensure that the selection positions of the steel plate sample selection and the steel pipe sample selection are at the same end.
Further, the methodIn step S200, "epsilon is used for each corresponding stressstrain curve _{1} The method for obtaining M steel plate stress values corresponding to different strain values by selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard comprises the following steps: the sections corresponding to the M steel plate strain values comprise epsilon _{1} +Δε; further, Δε may be included to further improve the difference between the test result and the stress value corresponding to Δε.
Preferably, the method for obtaining the stress values of the M steel plates comprises the following steps: based on the set interval a, at ε _{1} The +delta epsilon is taken as the center, and the left side and the right side of the center are respectively taken at equal intervalsThe strain values are used for obtaining M corresponding steel plate stress values; wherein a > 0; m is an odd number; ,so as to ensure that the selected scattered points can fully reflect the stress value which corresponds to the steel plate and has the closest yield strength corresponding to the steel tube strain value delta epsilon. It should be noted that the invention provides a uniform value method, and the invention also includes a value method with unequal intervals, namely asymmetric value, which can be implemented in epsilon _{1} One point is taken to the left of + delta epsilon, two points are taken to the right of it, at which point,the minimum value selected on the left side of the steel tube is a strain value corresponding to the yield strength of the steel tube, and the maximum value selected on the right side of the steel tube is not more than 5%;
further, the method for obtaining the goodness of fit between the steel plate and the steel pipe in the step S400 comprises the following steps: : wherein ,x_{i} Is the stress value variable of the steel plate, y _{i} Is the variable of the yield strength value of the steel pipe, < >>Stress average value corresponding to the same strain value of N steel plates,/>The average value of the yield strengths of N steel pipes is obtained; in the invention, the fitting goodness is used as a judgment standard, so that more accurate comparison data can be obtained.
Further, the method for obtaining the stress parameter of the steel plate for manufacturing the pipe further comprises the step S410 of based on epsilon _{1} Setting the characteristic strain delta epsilon corresponding to the yield strength of the steel pipe and compensating the deformation epsilon _{2} Obtaining theoretical strain value epsilon=epsilon of steel plate _{1} +ε _{2} +Δε; wherein, when the delta epsilon is 0.5%, epsilon _{2} The value range is as follows: 0 < epsilon _{2} Less than or equal to 1.0 percent, and the value range of epsilon: epsilon is more than 0.5 percent and less than or equal to 5 percent; when Δε is 0.2%, ε _{2} The value range is as follows: 0 < epsilon _{2} Less than or equal to 1.0%, the specific value of which can be determined according to the range of the specified yield strength of the steel pipe to be produced, for example, epsilon when the specified yield strength of the steel pipe to be produced is less than or equal to 485MPa _{2} 0.5% of epsilon can be taken when the specified yield strength of the steel pipe to be prepared is more than 485MPa _{2} 1.0% of the total weight of the composition can be taken; value range of epsilon: epsilon is more than 0.2 percent and less than or equal to 5 percent. In the present invention, since the strain value corresponding to the yield strength of the steel pipe is 0.5% and the strain value of the steel plate corresponding to the strain value of the steel pipe is more than 0.5% as proved by a large number of experiments, the minimum value of epsilon set in the present invention is more than 0.5%, that is, the value range of epsilon is more than delta epsilon.
Further, in the tensile stressstrain curve of the steel sheet, the curve change becomes gentle with an increase in strain value, and the corresponding change in stress value is not large, so that the value range of ε may be set to 0.5% < ε.ltoreq.5%. Further, taking Δε as 0.5% as an example, when the yield strength of the steel pipe is tested after the pipe is strained, the stressstrain curve of the material is not completely continuous with the stressstrain curve of the pipe manufacturing process, that is, it is not simple to directly superimpose 0.5% after the stopping point of the strain caused by the pipe manufacturing process of the material; strain epsilon and epsilon corresponding to steel pipe yield strength value on steel plate stress strain curve _{1} There is some deviation of +0.5% "mainly due to the materialAdditional stress caused by internal dislocation motion, particle movement, etc. after strain. To use a unified expression, ε is introduced _{2} To represent the strain change of the additional stress induced strain ε _{2} The deformation is not actually generated by the material, and the deviation of the deformed steel pipe strain value is further supplemented; in the present embodiment, the strain value of the steel sheet obtained by the test is mainly used, so epsilon is given here for the theoretical strain calculation formula _{2} The value range of (2) is 0 < epsilon _{2} ≤1.0％。
Further, judging whether the obtained theoretical strain value epsilon of the steel plate and the strain value of the steel plate corresponding to the maximum fitting goodness are consistent or not based on the obtained theoretical strain value epsilon of the steel plate; if the strain values are consistent, taking the strain values of the steel plates as standard parameters; if not, step S420 is performed.
Further, step S420, based on the theoretical strain value epsilon of the steel plate, combines the tensile stress strain curve of the steel pipe to be prepared to obtain the range of the theoretical stress value of the steel plate; acquiring a steel plate test stress value range based on a steel plate strain value corresponding to the maximum fitting goodness; judging whether the range of the theoretical stress value of the steel plate falls into the range of the stress value of the steel plate test; if m is greater than or equal to delta _{1} And n is less than or equal to delta _{2} Delta is then _{1} ≤R _{tx} ≤δ _{2} As stress parameters of steel plates for pipe making; wherein m is the lower limit value of the theoretical stress value of the steel plate, and n is the upper limit value of the theoretical stress value of the steel plate; delta _{1} For the lower limit value delta of the steel plate test stress value deduced according to the fitting formula _{2} And the upper limit value of the test stress value of the steel plate is deduced according to a fitting formula.
Taking 0.5% corresponding to the yield strength of the steel pipe as an example, in the art, the corresponding stress when the total deformation is 0.5% is defaulted as the yield strength, so as to determine the judging standard of the base steel plate for production, but because the change of the tensile property (mainly the yield strength and the yield ratio) of the material in the process of pipe making is influenced by factors such as the self characteristics of the material, the steel grade, the diameter of the steel pipe, the wall thickness, the forming expansion parameters and the like, difficulties often exist in determining the tensile property index of the steel plate, an index range is generally set according to experience, and the steel plate and the steel pipe are often in the production test process Such problems occur: firstly, the tensile property of the steel plate meets the required range, but the tensile property of the steel pipe after pipe making is unqualified; secondly, the tensile property of the steel plate does not meet the required range, but the tensile property of the steel pipe after the pipe is manufactured is qualified, and because the tensile property index requirement is not accurate enough, the control of a steel mill and a pipe mill is difficult, the steel mill judges and adjusts the process of the manufactured steel plate according to the steel plate tensile property requirement proposed by ordering, and the steel plate which does not meet the steel plate requirement but possibly meets the requirement after the pipe is manufactured is judged to be wasted, or the steel plate which meets the steel plate requirement but is unqualified after the pipe is manufactured is sent out according to a qualified product. As the sampling inspection is carried out according to batches in the pipe making process, the situation also causes the risk of disqualification product emission, and the invention proves that the strain value of the steel plate obtained by the invention replaces the traditional 0.5 percent by using R _{tx} Instead of R _{t0.5} As a selection standard of the steel plate, the existing problems can be effectively solved, and the qualification rate of the steel pipe is greatly improved.
A steel plate selecting method comprises the following steps: step S100, based on the diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining average strain epsilon of steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube; />
Step S200, selecting N steel plate samples of which the steel pipes to be prepared correspond to the preset specifications, and respectively obtaining stressstrain curves of the N corresponding steel plate samples through a tensile test; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plate stress values corresponding to different strain values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon corresponds to the yield strength selection standard of the steel pipe to be preparedParameters of (2);
step S300, selecting N steel plate samples of which the steel pipes to be prepared correspond to the preset specifications, respectively preparing N steel pipes according to parameters of the steel pipes to be prepared, taking tensile samples, obtaining stress strain curves and delta epsilon of the steel pipe samples through a tensile test, and obtaining yield strength values of the N steel pipe samples corresponding to the delta epsilon of the strain values;
Step S400, obtaining a steel plate stress value corresponding to the fitting goodness with the largest value as a characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same strain value and yield strength values of N steel pipe samples corresponding to the strain value delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the strain value of the steel plate, R _{tx} For the stress value corresponding to the total deformation epsilon on the tensile stress strain curve, Δx=100 Δepsilon;
s500, obtaining a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of 2) When DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of +.> 3) When N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
Step S600, based on the stress value R corresponding to the corrected characterization parameter _{tx} And selecting a steel plate corresponding to the steel pipe to be prepared, and preparing the steel pipe to be prepared.
It should be noted that, for convenience and brevity of description, specific working processes and related descriptions of the abovedescribed steel plate selecting method may refer to corresponding processes in the foregoing method embodiments for obtaining stress parameters of the steel plate for pipe making, so that details are not repeated herein.
In the present invention, when Δε is 0.5%, that is, when the total strain on the tensile stress strain curve is 0.5%, the stress R corresponds to _{t0.5} Yield strength as a steel pipe or steel pipe specimen; when delta epsilon is 0.2%, namely on a tensile stress strain curve, the corresponding stress R is when the residual deformation is 0.2% _{p0.2} As yield strength; r is R _{t0.5} Mainly used for steel plates and steel pipes with steel grade not higher than X80 steel grade, R _{p0.2} The method is mainly used for steel plates and steel pipes of steel grade X90; the method provided by the invention is suitable for the situation that the delta epsilon is 0.5% and the situation that the delta epsilon is 0.2%, and for the purpose of describing the invention more clearly, the detailed description is focused on the case that the delta epsilon is 0.5%, and the specific embodiment is not repeated when the delta epsilon is 0.2%.
The invention is further described below in connection with specific embodiments with reference to the accompanying drawings.
It should be noted that, in the process of manufacturing steel from steel plate to steel pipe, the change rule of the tensile property of the material mainly depends on the factors such as the material itself and the pipe making process, as the final product, the performance requirement of the steel pipe must be definite, which is the basis of the pipeline design, and the root of ensuring the pipeline safety, since the property of the steel plate changes in the pipe making process and the condition of the change varies according to the material and the process, after the tensile property requirement of the steel pipe is determined, the tensile property index of the steel plate is determined by the steel pipe manufacturer and the steel plate manufacturer according to the change rule of the tensile property in the pipe making process, namely, the tensile property requirement of the steel plate is reversely pushed according to the steel pipe performance requirement, namely, the steel pipe performance requirement is R _{t0.5} An example is described.
Referring to fig. 1, 2, 3, 4 and 5, a first fitted line graph, a second fitted line graph, a third fitted line graph, a fourth fitted line graph and a fifth fitted line graph of a steel plate stress value and a steel pipe yield strength value, respectively, according to a first specific example of a method for obtaining a steel plate stress parameter for pipe production in the present invention are illustrated; taking an X70 longitudinal submerged arc welded pipe with the dimension of D914 multiplied by 16mm as an example, the width of the steel plate before molding is 2792mm; the outer diameter D of the steel pipe after pipe making is 914mm; the tensile sample is a full wall thickness sample and the center of the sample is the center of the wall thickness, then t _{0} =8mm; calculating the average tensile strain of the material in the pipe making process according to a formulaRounding epsilon _{1} 1.0%; testing to obtain tensile stress strain curve of steel plate, selecting five values (M is 5), setting interval a to be 0.5%, and then using epsilon _{1} +0.5% as center, and selecting corresponding stress values R of the steel plate with strain values of 0.5%, 1.0%, 1.5%, 2.0% and 2.5% _{t0.5} 、R _{t1.0} 、R _{t1.5} 、R _{t2.0} 、R _{t2.5} The method comprises the steps of carrying out a first treatment on the surface of the After five steel pipes are manufactured, tensile test samples are taken at corresponding positions to test the tensile properties of the steel pipes, and N corresponding steel pipes R are recorded _{t0.5} The method comprises the steps of carrying out a first treatment on the surface of the Analysis of Steel plate stress value R _{t0.5} 、R _{t1.0} 、R _{t1.5} 、R _{t2.0} 、R _{t2.5} And the steel pipe R _{t0.5} And (3) performing straight line fitting to obtain the following results: the fitted line of the first fitted line graph is: steel pipe R _{t0.5} =448+0.20×steel plate R _{t0.5} Goodness of fit R ^{2} =0.136; the fitted straight line of the second fitted straight line graph is: steel pipe R _{t0.5} =244+0.58×steel plate R _{t1.0} Goodness of fit R ^{2} =0.397; the fitted line of the third fitted line graph is: steel pipe R _{t0.5} =71+0.89×steel plate R _{t1.5} Goodness of fit R ^{2} =0.651; the fourth fitted straight line of the fitted straight line graph is: steel pipe R _{t0.5} =129+0.77×steel plate R _{t2.0} Goodness of fit R ^{2} =0.623; the fitted line of the fifth fitted line graph is: steel pipe R _{t0.5} =175+0.68×steel plate R _{t2.5} Goodness of fit R ^{2} ＝0.554。
The result shows that the steel plate R _{t1.5} Yield strength R with steel pipe _{t0.5} The method has the best fitting goodness, namely, the corresponding strain value of 1.5% is used as a characterization parameter to select the corresponding steel plate; steel pipe R _{t0.5} The range of (2) is 485MPa or less and R is steel pipe _{t0.5} Less than or equal to 635MPa according to a fitting formulaObtaining the steel plate R _{t1.5} The range of (2) is 465MPa or less and R is a steel plate _{t1.5} ≤634MPa。
TABLE 1
Further, referring to Table 1, table 1 shows the fitting stress value R of the steel pipe _{t0.5} With the measured yield strength value R of the steel pipe _{t0.5} Is a table of correspondence parameters; in this embodiment, N is 45, and as can be seen from this embodiment, 45 ΔR _{t0.5} Includes both positive and negative numbers, so N ΔR are selected _{t0.5} The absolute value of the minimum value (15 MPa) in (2) is taken as the lower limit value e of the safety margin, the maximum value (10 MPa) is taken as the upper limit value f of the safety margin, and the adjustment is based on the adjustmentAfter that, the stress value range of the steel plate is selected as the corresponding steel pipeAnd steel pipe R _{t0.5} =244+0.58×steel plate R _{t1.0} Obtaining the stress value R of the steel plate corresponding to the characterization parameters after further correction and optimization _{t1.5} The range of (2) is: r is not less than 480MPa _{t1.5} And the stress parameter of the steel plate of the X70 longitudinal submerged arc welded pipe with the size of D914 multiplied by 16mm is less than or equal to 624 MPa.
Referring to fig. 6 to 10, a first fitted line graph, a second fitted line graph, a third fitted line graph, a fourth fitted line graph and a fifth fitted line graph of a steel plate stress value and a steel pipe stress value of a second specific embodiment of the method for obtaining a steel plate stress parameter for pipe production in the present invention are illustrated, and an X80 longitudinal submerged arc welded pipe with a dimension of D1219×27mm is taken as an example, and a steel plate width W before forming is 3705mm; the outer diameter D of the steel pipe after pipe making is 1219mm; the tensile sample is a full wall thickness sample and the center of the sample is the center of the wall thickness, then t _{0} =13.5 mm; calculating the average tensile strain of the material in the pipe making process according to a formulaRounding epsilon _{1} 1.0%.
Testing to obtain tensile stress strain curve of steel plate, selecting five values, setting interval a to 0.5%, and then using epsilon _{1} +0.5% as center, and selecting corresponding stress values R of the steel plate with strain values of 0.5%, 1.0%, 1.55, 2.0% and 2.5% _{t0.5} 、R _{t1.0} 、R _{t1.5} 、R _{t2.0} 、R _{t2.5} The method comprises the steps of carrying out a first treatment on the surface of the After five steel plates are manufactured into five steel pipes, tensile test samples are taken at corresponding positions to test the tensile properties of the steel pipes, and corresponding steel pipes R are recorded _{t0.5} The method comprises the steps of carrying out a first treatment on the surface of the Analysis of Steel plate stress value R _{t0.5} 、R _{t1.0} 、R _{t1.5} 、R _{t2.0} 、R _{t2.5} And the steel pipe R _{t0.5} And (3) performing straight line fitting to obtain the following results:
the fitted line of the first fitted line graph is: steel pipe R _{t0.5} =6760.1×steel plateR _{t0.5} Goodness of fit R ^{2} ＝0.024；
The fitted straight line of the second fitted straight line graph is: steel pipe R _{t0.5} =127+0.854×steel plate R _{t1.0} Goodness of fit R ^{2} ＝0.370；
The fitted line of the third fitted line graph is: steel pipe R _{t0.5} = 42+1.114×steel plate R _{t1.5} Goodness of fit R ^{2} ＝0.882；
The fourth fitted straight line of the fitted straight line graph is: steel pipe R _{t0.5} = 2.2+1.022 x steel plate R _{t2.0} Goodness of fit R ^{2} ＝0.947；
The fitted line of the fifth fitted line graph is: steel pipe R _{t0.5} =78+0.875×steel plate R _{t2.5} Goodness of fit R ^{2} ＝0.925。
The result shows that the steel plate R _{t2.0} And the steel pipe R _{t0.5} With best goodness of fit, i.e. the steel plate stress value R with the greatest goodness of fit should be used _{t2.0} As a characterization parameter, selecting a steel plate corresponding to the steel pipe to be prepared; steel pipe R _{t0.5} The range of (2) is 555MPa or less and R is steel pipe _{t0.5} 690MPa or less according to the formula of the fitting straight lineObtaining the optimal steel plate stress value R corresponding to the maximum fitting goodness _{t2.0} The range of (2) is 545 MPaR steel plate _{t2.0} ≤677MPa。
TABLE 2
Steel plate Rt2.0  Actually measured Rt0.5 of steel pipe  Steel tube Rt0.5 calculated according to fitting formula  (actual)Valuecalculated value) 
610  625  626  1 
621  629  639  10 
616  630  632  2 
621  631  637  6 
592  600  607  7 
598  610  613  3 
Further, referring to Table 2, table 2 shows the fitting stress value R of the steel plate _{t0.5} With the measured yield strength value R of the steel pipe _{t0.5} Is a table of correspondence parameters; in this embodiment, N is 5, and ΔR is as follows from this embodiment _{t0.5} All are smaller than zero, the minimum difference value is10 MPa, and only theA safety margin lower limit value, without considering a safety margin upper limit value; the lower limit value e of the safety margin is 10, and the stress value range of the steel plate is selected as the corresponding steel pipe after adjustment and correctionYang Gangguan R _{t0.5} = 2.2+1.022 x steel plate R _{t2.0} Obtaining a further optimized steel plate R _{t2.0} In the range of 555MPa to R _{t2.0} And the stress parameter of the steel plate of the X80 longitudinal submerged arc welded pipe with the size of D1219 multiplied by 27mm is less than or equal to 677 MPa.
According to the method for obtaining the stress parameters of the steel plate for manufacturing the pipe, various error accumulation in actual machining is considered, the step of safety margin adjustment and correction is carried out on the stress value range corresponding to the strain value of the steel plate obtained through fitting a linear formula, the accuracy of the stress value range of the steel plate, which is obtained through a test and is judged as a yield strength standard, is improved, and therefore the steel plate can be obtained as a selection standard of the steel plate, and the steel plate meets the process requirements more accurately. Disclosed in the present invention is: fitting R based on obtained steel pipe _{t0.5} Actually measured R of steel pipe obtained by actually measuring _{t0.5} Based on DeltaR _{t0.5} =actual measurement of steel tube R _{t0.5} Fitting R to Steel pipe _{t0.5} To obtain N delta R _{t0.5} The method comprises the steps of carrying out a first treatment on the surface of the Specifically, first, N ΔR obtained by judgment _{t0.5} Whether both are greater than zero or both are less than zero, or include both positive and negative numbers; second, based on the N ΔR obtained _{t0.5} And then correspondingly determining the upper limit value and the lower limit value of the safety margin, and further correcting the corresponding range of the steel plate stress value when the obtained fitting goodness is maximum according to the formula of the safety margin corresponding to different conditions. In addition, the invention also comprises a second optimization method: the range of stress values corresponding to the steel plate is directly deduced according to the internal control standard of the steel pipe to be prepared, and the specific method is as follows: first, R based on the standard corresponding to the steel pipe to be prepared _{t0.5} The upper limit value and the lower limit value of the steel pipe are directly increased or decreased according to the safety margin, and a range corresponding to the yield strength of the steel pipe is obtained after the safety margin is considered; second, the first one is a first one,and then, according to the fitting straight line with the maximum fitting goodness, which is obtained by straight line fitting, carrying out the determination of the corresponding range of the steel plate stress value directly by taking the steel pipe yield strength value after the safety margin is considered.
The result obtained by the first optimization method is obtained based on the comparison of a large amount of data, and the selection of the base material prepared by the steel pipe with higher corresponding precision level has great guiding significance; the result obtained by the second optimization method is the adjustment of the yield strength range of the steel pipe based on the gauge in the field, the calculation amount is very small, and the corresponding stress value range of the steel plate can be rapidly obtained based on the fitting straight line.
It should be noted that the first optimization method and the second optimization method are two parallel optimization methods, and can be respectively and independently used as a range of the stress value of the steel plate corresponding to the strain value with the largest fitting goodness obtained after the test, so as to obtain a further optimized selection standard of the tensile property requirement of the steel plate determined according to the performance requirement of the steel pipe. In addition, according to the specific steps of the method for obtaining the stress parameters of the steel plate for manufacturing the steel pipe, the method can be directly used as a selection standard for the base metal steel plate of the steel pipe to be manufactured, and the numerical value obtained by the second optimization method further proposed by the invention does not influence the main protection method of the invention and the protection range of the method.
Further, for the X70 longitudinal submerged arc welded pipe with the dimension of D914X 16mm, the calculation can be carried out according to a second optimization method, and the specific method is as follows: steel pipe R _{t0.5} The range of (2) is 485MPa or less and R is steel pipe _{t0.5} Less than or equal to 635MPa, wherein the lower limit value e of the yield strength of the steel pipe is selected to be 15MPa safety margin according to the standard of a line gauge, the upper limit value f is selected to be 10MPa safety margin according to the standard of a second optimization method Fitting a straight line to obtain R with the pressure of 482MPa being less than or equal to R _{t1.5} ≤622MPa。
Further, for X80 straight with a dimension of D1219X 27mmThe seam submerged arc welded pipe may also be calculated according to a second optimization method. Steel pipe R _{t0.5} The range of (2) is 555MPa or less and R is steel pipe _{t0.5} A safety margin of 10MPa is selected according to the lower limit value e of the yield strength of the steel pipe and the upper limit value f is selected according to the standard of the second optimization method, wherein the safety margin of the lower limit value e of the yield strength of the steel pipe is less than or equal to 690MPa and the safety margin of the upper limit value f is selected to be 10MPaFitting a straight line to obtain an optimized steel plate R _{t2.0} In the range of 555MPa to R _{t2.0} ≤668MPa。
It should be noted that, the second optimization method and the first optimization method are two parallel optimization methods, and can be respectively and independently used as a range of the stress value of the steel plate corresponding to the strain value with the largest fitting goodness obtained after the test, and the two methods are independent and feasible due to different selected safety margin methods.
Further, referring to fig. 11, a schematic view of a first form of a typical stressstrain curve of a steel sheet or a steel pipe in the method for obtaining a steel sheet stress parameter for pipe making according to the present invention is shown, the steel sheet stressstrain curve being characterized by discontinuous strain hardening, the stressstrain curve having a "peak", and the R of the steel sheet _{t0.5} Falls into the lower yield point, and after passing the lower yield point, the stress value changes less in a certain strain range, namely R _{t0.5} and R_{t0.5} Substantially identical; after pipe making, the stressstrain curve of the steel pipe has no sharp top, the side line is continuous strain reinforced type, and the steel pipe R _{t0.5} And steel plate R _{t0.5} R is R _{t1.5} All have better uniformity. The strength change trend shown by the stressstrain curve of the steel plate is consistent with the test result of the steel pipe, namely the yield strength change after pipe making is smaller, and the stress value of the steel plate obtained by the test is used as a characterization parameter.
Further, referring to fig. 12, a schematic diagram of a second form of a typical stressstrain curve of a steel sheet or a steel pipe in the method for obtaining a steel sheet stress parameter for pipe making according to the present invention is shown, wherein the steel sheet stressstrain curve is characterized by continuous strain hardening, and the stress value increases as the strain increases; stress of steel pipe after pipe makingThe strain curve is still continuous strain strengthening type, and the steel pipe R _{t0.5} And steel plate R _{t0.5} The difference is larger than that of the steel plate R _{t1.5} More closely, the strength change trend shown by the stressstrain curve of the steel plate is consistent with the test result of the steel pipe, namely the yield strength after pipe making is increased, and the stress value of the steel plate obtained by the test is used as a characterization parameter.
Further, referring to fig. 13, a schematic view of a third form of a typical stressstrain curve of a steel sheet or a steel pipe in the method for obtaining a steel sheet stress parameter for pipe making according to the present invention is shown, the steel sheet stressstrain curve being characterized by discontinuous strain hardening, and having "tip" and R of the steel sheet _{t0.5} Falling on a half slope which descends after passing through a 'sharp top', and then as the strain increases, the stress is reduced further firstly and then remains unchanged in a longer strain range; the stressstrain curve of the steel pipe after pipe making is still continuous strain reinforced; steel pipe R _{t0.5} And steel plate R _{t0.5} The difference is larger than that of the steel plate R _{t1.5} And the strength change trend expressed by the stressstrain curve of the steel plate is consistent with the test result of the steel pipe, namely the yield strength after pipe making is reduced, and the stress value of the steel plate obtained by the test is used as a characterization parameter.
Further, referring to FIG. 14, FIG. 14 is a schematic view showing the selection of different parameters corresponding to the standard yield strength of the steel plate and the steel pipe according to the present invention, R _{t0.5} Namely, on a tensile stress strain curve, the stress corresponding to the total deformation of 0.5% is taken as yield strength; r is R _{p0.2} Namely, on a tensile stress strain curve, the stress corresponding to the residual deformation of 0.2% is taken as yield strength; r is R _{t0.5} Mainly used for steel plates and steel pipes with steel grade not higher than X80 steel grade, R _{p0.2} Mainly used for steel grade X90 and steel plates and pipes, and in the examples listed in the invention, the strain value is 0.5 percent as an example, and the invention corresponds to R _{p0.2} The same applies when the strain value of (a) is 0.2%, and will not be described in detail here.
The invention also comprises a system for obtaining the stress parameters of the steel plate for manufacturing the pipe, which comprises a first module, a second module, a third module, a fourth module and a fifth module; wherein the first module is configured withBased on the diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining average strain epsilon of steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube;
the second module is configured to select N steel plate samples of which the steel pipes to be prepared correspond to the set specifications, and obtain stressstrain curves of the N corresponding steel plate samples through tensile tests respectively; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plate stress values corresponding to different strain values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared;
The third module is configured to select N steel plate samples of which the steel pipes are to be prepared and have corresponding set specifications, prepare N steel pipe samples according to parameters of the steel pipes to be prepared respectively, obtain stress strain curves and delta epsilon of the steel pipe samples through a tensile test, and obtain yield strength values of the N steel pipe samples corresponding to the strain value delta epsilon;
the fourth module is configured to obtain the steel plate stress value corresponding to the fitting goodness with the largest value as the characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same strain value and the yield strength values of the N steel pipe samples corresponding to the strain value delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the corresponding steel plate strain value, R _{tx} For the stress value corresponding to the total deformation epsilon on the tensile stress strain curve, Δx=100 Δepsilon;
the fifth module is configured to obtain a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of 2) When DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of3) When N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
Preferably, Δε in this system is 0.5%.
Preferably, the steel plate samples in the second module are transverse sampling samples.
Preferably, the selection position of the steel pipe sample in the third module is identical to the selection position of the steel plate sample.
Preferably, the "in each corresponding stressstrain curve" in the second module is respectively expressed in ε _{1} The +delta epsilon is a standard, M steel plate strain values are selected based on preset intervals, so that M steel plate stress values corresponding to different strain values are obtained, and the specific configuration is as follows: based on the set interval a, at ε _{1} The +Deltaepsilon is taken as the center and is taken at the left and the right sidesThe strain values are used for obtaining M corresponding steel plate stress values; wherein a > 0; m is an odd number; / >
Preferably, the method for obtaining the fitting goodness of the steel plate and the steel pipe in the fourth module comprises the following steps:
wherein ,x_{i} Is the stress value variable of the steel plate, y _{i} Is the variable of the yield strength value of the steel pipe, < >>Stress average value corresponding to the same strain value of N steel plates,/>The average value of the yield strengths of the N steel pipes is given.
The system further includes a fourth submodule configured to be epsilonbased _{1} Setting the characteristic strain delta epsilon corresponding to the yield strength of the steel pipe and compensating the deformation epsilon _{2} Obtaining theoretical strain value epsilon=epsilon of steel plate _{1} +ε _{2} +Δε; wherein epsilon when delta epsilon=0.5% _{2} The value range is as follows: 0 < epsilon _{2} Less than or equal to 1.0 percent; the value range of epsilon is as follows: epsilon is more than 0.5 percent and less than or equal to 5 percent; epsilon when delta epsilon=0.2% _{2} The value range is as follows: 0 < epsilon _{2} Less than or equal to 1.0 percent, and the value range of epsilon is as follows: epsilon is more than 0.2 percent and less than or equal to 5 percent; judging whether the obtained theoretical strain value epsilon of the steel plate and the strain value of the steel plate corresponding to the maximum fitting goodness are consistent or not based on the obtained theoretical strain value epsilon of the steel plate; if the strain values are consistent, taking the strain values of the steel plates as standard parameters; if not, the fourth execution module is started.
The fourth execution module is configured to acquire the range of the theoretical stress value of the steel plate based on the theoretical stress value epsilon of the steel plate and combined with the tensile stress strain curve of the steel pipe to be prepared; acquiring a steel plate test stress value range based on a steel plate strain value corresponding to the maximum fitting goodness; judging whether the range of the theoretical stress value of the steel plate falls into the range of the stress value of the steel plate test; if m is greater than or equal to delta _{1} And n is less than or equal to delta _{2} Delta is then _{1} ≤R _{tx} ≤δ _{2} As stress parameters of steel plates for pipe making; wherein m is the lower limit value of the theoretical stress value of the steel plate, and n is the upper limit value of the theoretical stress value of the steel plate; delta _{1} For the lower limit value, delta, of the test stress value range of the steel plate _{2} The upper limit value of the stress value range is tested for the steel plate.
Preferably, when Δε=0.5%, ε is in the range of: epsilon is more than 0.5 percent and less than or equal to 5 percent; when Δε=0.2%, the value range of ε is: epsilon is more than 0.2 percent and less than or equal to 5 percent.
A steel plate selecting system comprises a first module, a second module, a third module, a fourth module, a fifth module and a sixth module; wherein the first module is configured to be based on the pipe diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining average strain epsilon of steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube;
the second module is configured to select N steel plate samples of which the steel pipes to be prepared correspond to the set specifications, and obtain stressstrain curves of the N corresponding steel plate samples through tensile tests respectively; respectively with epsilon in each corresponding stressstrain curve _{1} +ΔEpsilon is a standard, M steel plate strain values are selected based on preset intervals, so that M steel plate stress values corresponding to different strain values are obtained; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared;
The third module is configured to select N steel plate samples of which the steel pipes are to be prepared and have corresponding set specifications, prepare N steel pipe samples according to parameters of the steel pipes to be prepared respectively, obtain stress strain curves and delta epsilon of the steel pipe samples through a tensile test, and obtain yield strength values of the N steel pipe samples corresponding to the strain value delta epsilon;
the fourth module is configured to obtain the steel plate stress value corresponding to the fitting goodness with the largest value as the characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same strain value and the yield strength values of the N steel pipe samples corresponding to the strain value delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the strain value of the steel plate, R _{tx} For the stress value corresponding to the total deformation epsilon on the tensile stress strain curve, Δx=100 Δepsilon;
the fifth module is configured to obtain a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of 2) When DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the corrected characterization parameter _{tx} Is in the range of3) When N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
The sixth module is configured to be based on the stress value R corresponding to the corrected characterization parameter _{tx} And selecting a steel plate corresponding to the steel pipe to be prepared, and preparing the steel pipe to be prepared.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention, and in particular, the technical features set forth in the various embodiments may be combined in any manner so long as there is no structural conflict; the present invention is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.
In the description of the present invention, terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like, which indicate a direction or a positional relationship, are based on the direction or the positional relationship shown in the drawings, are merely for convenience of description, and do not indicate or imply that the apparatus or elements must have a specific orientation, be constructed and operated in a specific orientation, and thus are not to be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Furthermore, it should be noted that, in the description of the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention can be understood by those skilled in the art according to the specific circumstances.
The terms "comprises," "comprising," or any other variation thereof, are intended to cover a nonexclusive inclusion, such that a process, article, or apparatus/means that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, article, or apparatus/means.
Thus far, the technical solution of the present invention has been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of protection of the present invention is not limited to these specific embodiments. Equivalent modifications and substitutions for related technical features may be made by those skilled in the art without departing from the principles of the present invention, and such modifications and substitutions will fall within the scope of the present invention.
Claims (7)
1. A method for obtaining stress parameters of a steel plate for pipe making, the method comprising the steps of:
step S100, based on the diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining the average strain epsilon of the steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube;
step S200, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, and respectively obtaining stressstrain curves of the N corresponding steel plate samples through a tensile test; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plate stress values corresponding to different strain values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared;
step S300, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, respectively preparing N steel pipe samples according to parameters of the steel pipe to be prepared, obtaining a stress strain curve and delta epsilon of the steel pipe samples through a tensile test, and obtaining yield strength values of the N steel pipe samples corresponding to the delta epsilon of the strain value;
step S400, obtaining a steel plate stress value corresponding to the fitting goodness with the largest value as a characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same stress value and the yield strength values of the N steel pipe samples corresponding to the same stress value when the stress value is delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the strain value of the steel plate, R _{tx} Is the total on the tensile stress strain curve of the steel plateCorresponding stress value when deformation is epsilon, wherein Deltax=100 Deltaepsilon;
s500, obtaining a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range ofWhen DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range ofWhen N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
2. The method of obtaining a stress parameter of a steel sheet for pipe production according to claim 1, wherein Δε is 0.5%.
3. The method of obtaining stress parameters of steel sheet for pipe production according to claim 1, wherein said steel sheet sample in step S200 is a transverse sampling sample.
4. The method of obtaining a steel plate stress parameter for pipe production according to claim 2, wherein the selection position of the steel pipe sample in step S300 coincides with the selection position of the steel plate sample.
5. The method for obtaining stress parameters of steel sheet for pipe production according to claim 1, wherein "epsilon is used for each corresponding stressstrain curve" in step S200 _{1} The method for obtaining M steel plate stress values corresponding to different strain values by selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard comprises the following steps: based on the set interval a, at ε _{1} The +Deltaepsilon is taken as the center and is taken at the left and the right sidesThe strain values are used for obtaining M corresponding steel plate stress values;
6. the method for obtaining stress parameters of steel sheet for pipe production according to claim 1, wherein the method for obtaining goodness of fit between steel sheet and steel pipe in step S400 is as follows:
7. A method for selecting a steel sheet, comprising the steps of:
step S100, based on the diameter D of the steel pipe to be prepared, the width W of the steel plate before forming and the distance t between the center position of the tensile sample and the outer surface of the steel pipe _{0} Obtaining the average strain epsilon of the steel pipe to be prepared _{1}； wherein , wherein ,0＜t_{0} T is less than t, and t is the wall thickness of the steel tube;
step S200, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, and respectively obtaining stressstrain curves of the N corresponding steel plate samples through a tensile test; respectively with epsilon in each corresponding stressstrain curve _{1} Selecting M steel plate strain values based on a preset interval by taking +delta epsilon as a standard to obtain M steel plate stress values corresponding to different strain values; based on stressstrain curves of N corresponding steel plate samples and M steel plate stress values corresponding to different strain values, taking the steel plate stress values corresponding to the same strain value as a group, and obtaining M groups of different strain values and N steel plate stress values corresponding to the same strain value of each group; wherein N is more than or equal to 5, M is more than or equal to 3, and delta epsilon is a parameter corresponding to a yield strength selection standard of the steel pipe to be prepared;
step S300, selecting N steel plate samples of the steel pipe to be prepared with corresponding set specifications, respectively preparing N steel pipe samples according to parameters of the steel pipe to be prepared, obtaining a stress strain curve and delta epsilon of the steel pipe samples through a tensile test, and obtaining yield strength values of the N steel pipe samples corresponding to the delta epsilon of the strain value;
Step S400, obtaining a steel plate stress value corresponding to the fitting goodness with the largest value as a characterization parameter of the steel plate stress value through straight line fitting based on the obtained N steel plate stress values corresponding to the same stress value and the yield strength values of the N steel pipe samples corresponding to the same stress value when the stress value is delta epsilon; based on fitting straight line R _{tΔx} ＝a+b×R _{tx} Setting the range corresponding to the yield strength of the standard steel pipe as c is less than or equal to R _{tΔx} D is less than or equal to d, and the stress value range of the steel plate corresponding to the characterization parameter is obtainedWherein x is 100 times of the strain value of the steel plate, R _{tx} The stress value corresponding to the total deformation epsilon on the tensile stress strain curve of the steel plate is deltax=100 deltaepsilon;
s500, obtaining a fitting stress value R of the steel pipe through a fitting linear formula and an actual measurement value of the steel pipe sample _{tΔx} Measured R of steel pipe sample _{tΔx} Based on DeltaR _{tΔx} =actual measurement R _{tΔx} fitting R _{tΔx} Obtaining N DeltaR _{tΔx} The method comprises the steps of carrying out a first treatment on the surface of the 1) When DeltaR _{tΔx} All are greater than zero, N DeltaR are selected _{tΔx} The maximum value in (a) is used as the upper limit value f of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range ofWhen DeltaR _{tΔx} All are less than zero, N DeltaR are selected _{tΔx} The absolute value of the minimum value in the test is taken as the lower limit value e of the safety margin, and the stress value R corresponding to the characterization parameter after correction _{tx} Is in the range ofWhen N deltaR _{tΔx} When the number includes both positive and negative numbers, N DeltaR are selected _{tΔx} The absolute value of the minimum value of the characteristic parameters is used as a safety margin lower limit value e, and when the absolute value of the minimum value of the characteristic parameters is used as a safety margin upper limit value f, the corrected stress value R corresponding to the characteristic parameters is used as a stress value R _{tx} Is in the range of +.>
Step S600, based on the corrected stress value R corresponding to the characterization parameter _{tx} And selecting the corresponding steel plate of the steel pipe to be prepared, and preparing the steel pipe to be prepared.
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