17 results about "Compact tension specimen" patented technology

The invention provides a corrosion fatigue crack propagation life prediction method based on an environmental damage model, and the method comprises the steps: building a corrosion fatigue damage model according to a fatigue damage model considering the effects of maximum stress and plastic strain and the influence of an environmental factor Cenv; carrying out a low-cycle fatigue test and a corrosion fatigue crack propagation test by utilizing the low-cycle fatigue sample and the compact tensile sample to respectively obtain low-cycle fatigue data and corrosion fatigue crack propagation rates under different stress ratios; the damage model is written into a subprogram in a USDFLD user subprogram interface provided by finite element software ABAQUS, corrosion fatigue crack propagation simulation is carried out, and the corrosion fatigue crack propagation rate of the standard compact tensile sample under different stress ratios is predicted. The influence of a fatigue damage model and an environmental factor Cenv is taken into consideration, finite element simulation is carried out in combination with a USDFLD subprogram of finite element software ABAQUS, and corrosion fatigue crack propagation simulation of the structure is achieved. The method is high in universality and easy to master and implement.

The invention belongs to the technical field of ferrous metallurgy, and relates to high-grade hydrogen transmission pipeline steel and a preparation method thereof.The high-grade hydrogen transmission pipeline steel is prepared from, by mass, 0.02%-0.04% of C, 0.20%-0.30% of Si, 1.20%-1.30% of Mn, smaller than or equal to 0.010% of P, smaller than or equal to 0.0010% of S, 0.015%-0.055% of Alt, smaller than or equal to 0.0020% of N, smaller than or equal to 0.0010% of O, smaller than or equal to 0.0001% of H, 0.90%-1.00% of Cr, 0.40%-0.50% of Mo, 0.020%-0.030% of Ti, 0.05%-0.07% of Nb, 0.40%-0.50% of Ni and the balance iron and inevitable impurities; various performance indexes, especially hydrogen induced crack resistance indexes, of the composite material are outstanding, CSR is equal to 0, CLR is equal to 0, CTR is equal to 0, slow tensile IRA and IEL are smaller than or equal to 20% in a solution A, KIH of a stepped compact tensile sample is larger than or equal to 100 MPa.m < 1 / 2 > in a 6.3 MPa pure hydrogen environment, and the fatigue life is larger than or equal to 500,000 times; according to the method, the technical problems in the research and development process of the steel material for the hydrogen conveying pipeline are solved, the technical scheme is relatively simple and easy to implement, the obtained product is high in performance stability and controllable in cost, and popularization and application in long-distance, large-scale and safe conveying pipeline construction of high-pressure hydrogen are facilitated.

The invention relates to the technical field of material testing, and discloses a method for testing hydrogen induced cracking of a material in a high-pressure hydrogen environment, which comprises the following steps: firstly, preparing an extended compact tensile sample based on size data of a standard wedge-shaped opening loading sample and a standard compact tensile sample; then carrying out fatigue crack prefabrication on the extended compact tensile sample through a fatigue testing machine, and carrying out shape conversion to obtain a standard wedge-shaped opening loading sample with fatigue cracks, and taking the standard wedge-shaped opening loading sample as a target wedge-shaped opening loading sample; applying a load to the tail end of the fatigue crack on the target wedge-shaped opening loading sample, and placing the target wedge-shaped opening loading sample in a high-pressure hydrogen environment to determine the length of the current hydrogen-induced crack; and finally, determining a stress intensity factor threshold value of the to-be-tested material according to the initial applied stress intensity factor, the current hydrogen-induced crack length and the standard value of the hydrogen-induced crack length. According to the method, not only can a more accurate hydrogen-induced delayed cracking stress intensity factor threshold value be obtained, but also the test cost can be effectively reduced.

The present invention discloses a preparation method of a recombined compact tension specimen, comprising the following steps: 1) preparing a specimen for a target material and spraying speckles on the surface of the specimen; 2) conducting a fracture toughness test on the specimen, and during the fracture toughness test, measuring the specimen by using a full-field strain measurement system; 3) determining a plastic strain region on the surface of the specimen according to the measurement result of the full-field strain measurement system and excising the plastic strain region, and retaining the non-plastic strain regions on both sides of the specimen to obtain a recombined block; 4) welding the recombined block with auxiliary materials to obtain the recombined compact tension specimen. The preparation method of the recombined compact tension specimen of the present invention, through reasonable recombination means and verification means, enables the performance of the recombined specimen to be similar to that of the original specimen; and the non-plastic deformation regions (recombined blocks) after the fracture toughness test can be recombined into two or more specimens, increasing the material utilization rate by three times or more.

The present invention discloses a processing method for a fracture toughness compact tension specimen. The specimen is a compact tension specimen (CTS), and the implementation steps are as follows: S1. Blanking: Prepare the blank of the specimen and mark the position of the notch surface of the specimen; S2. Rough machining: Milling the blank on the basis of leaving a margin on one side of the machining surface, and machining the side surfaces connected to the machining surface to the standard size requirements of the compact tension specimen (CTS); S3. Finish machining: Grinding the machining surface of the specimen to machine the thickness of the specimen to the standard size requirements of the compact tension specimen (CTS); then, determine the drilling position according to the standard of the compact tension specimen (CTS), and drill the specimen through a milling machine; S4. Heat treatment: Perform heat treatment on the drilled specimen to eliminate the internal stress of the specimen and facilitate subsequent processing; S5. Notch machining: Determine the cutting position of the notch according to the standard of the compact tension specimen (CTS), and machine the heat-treated specimen by wire cutting to finally obtain a standard specimen that meets the requirements.

The invention belongs to the field of metal material testing, and particularly discloses a method and a model for predicting the fatigue crack growth rate of pipeline steel in a hydrogen-doped environment, and the prediction method comprises the following steps: processing a plurality of compact tensile samples of the pipeline steel to be tested, and then performing fatigue crack growth test on the compact tensile samples in a nitrogen environment and environments with different hydrogen doping ratios to obtain the fatigue crack growth rate of the pipeline steel. The fatigue crack propagation rate and the corresponding stress intensity factor range are obtained and fitted to obtain a constant term, so that a fatigue crack propagation prediction model of the to-be-detected pipeline steel in the hydrogen-doped environment is established, and finally the fatigue crack propagation rate of the pipeline steel can be predicted according to the hydrogen doping ratio given by the fatigue crack propagation prediction model. According to the method, the fatigue crack propagation prediction model of the to-be-tested pipeline steel in the hydrogen-doped environment can be established only by carrying out the fatigue crack propagation test in the nitrogen environment and a small number of environments with different hydrogen doping ratios, so that prediction is realized, the test period of prediction is effectively shortened, and the safety of testers and equipment can be ensured.

The utility model provides a compact tensile sample fixture for testing stress corrosion strength factor, which comprises a plurality of pins, an upper chuck, a lower chuck and a corrosion container, the upper end of the upper chuck is provided with a hydraulic servo testing machine fixing part, and the lower end of the lower chuck is provided with a hydraulic servo testing machine fixing part. Compact tensile sample grooves are formed in the lower end of the upper chuck and the upper end of the lower chuck, pin through holes are formed in the side wall of the compact tensile sample groove of the upper chuck and the side wall of the compact tensile sample groove of the lower chuck, and pins can be inserted and fixed into the pin through holes. The compact tensile sample groove of the upper chuck and the compact tensile sample groove of the lower chuck are both arranged in the corrosion container cavity, a magnet is arranged on the side wall of the side, away from the pin through hole, of the compact tensile sample groove of the upper chuck, and a magnet is arranged on the side wall of the side, away from the pin through hole, of the compact tensile sample groove of the lower chuck. A lower chuck connecting hole is formed in the bottom of the corrosion container, the lower chuck connecting hole is a threaded hole, external threads are arranged on the outer side wall of the lower chuck, and the lower chuck connecting hole is in threaded connection with the outer side wall of the lower chuck. According to the utility model, a scientific and reasonable structural design is adopted, and the sample is fixed by the pin, so that the physical damage of the sample in the fixing process is reduced, and the load is uniformly and accurately applied to the compact tensile sample in the stress corrosion strength factor test.

The present invention belongs to the technical field of iron and steel metallurgy, and relates to a high-grade hydrogen transmission pipeline steel and a preparation method thereof. The chemical composition of the high-grade hydrogen transmission pipeline steel and its mass percentage content are as follows: C 0.02 - 0.04%, Si 0.20 - 0.30%, Mn 1.20 - 1.30%, P ≤ 0.010%, S ≤ 0.0010%, Alt 0.015 - 0.055%, N ≤ 0.0020%, O ≤ 0.0010%, H ≤ 0.0001%, Cr 0.90 - 1.00%, Mo 0.40 - 0.50%, Ti 0.020 - 0.030%, Nb 0.05 - 0.07%, Ni 0.40 - 0.50%, and the balance is iron and unavoidable impurities; each performance index of the present invention is outstanding, especially the hydrogen-induced cracking resistance index, meeting CSR = 0, CLR = 0, CTR = 0 under solution A, slow tensile IRA, IEL ≤ 20%, in a 6.3 MPa pure hydrogen environment, the KIH of the stepped compact tension specimen ≥ 100 MPa·m<supgt;1 / 2< / supgt;, and the fatigue life ≥ 500,000 times; the present invention solves the technical problems faced in the research and development of materials for hydrogen transmission pipeline steel, the technical solution is relatively simple and easy to implement, the performance stability of the obtained product is high and the cost is controllable, which is conducive to popularization and use in the construction of high-pressure hydrogen long-distance, large-scale and safe transmission pipelines.

A production method of TMCP hydrogen-doped hydrogen-delivering pipeline steel, characterized in that the chemical composition of the steel contains C=0.03%-0.05%, Si=0.12%-0.30%, Mn=0.95%-1.05%, P≤0.004%, S≤0.0010%, Alt=0.020%-0.045%, Nb=0.040%-0.050%, Ti=0.010%-0.020%, and the balance is Fe and inevitable impurities. The steel plate has good hydrogen environment compatibility performance in addition to the mechanical properties of conventional pipeline steel. In A solution environment, HIC: CSR≤2%, CLR≤15%, CTR≤5%; the tensile strength and the reduction of area of the smooth sample in a 6.3 MPa pure hydrogen environment are greater than 80% and 95% in the air environment; at the same time, in the 6.3 MPa pure hydrogen environment, the K1C of the step compact tension sample is ≥100 MPa·m1 / 2, and the fatigue life is ≥100,000 times.

The application relates to the technical field of material testing, and discloses a material hydrogen-induced cracking test method under a high-pressure hydrogen environment, wherein first, an extended compact tension specimen is prepared based on size data of a standard wedge-opening loading specimen and a standard compact tension specimen; then, the extended compact tension specimen is subjected to fatigue crack pre-preparation by a fatigue testing machine, and shape conversion is carried out, so that a standard wedge-opening loading specimen with a fatigue crack is obtained, which is used as a target wedge-opening loading specimen; next, a load is applied to the fatigue crack end on the target wedge-opening loading specimen, and the target wedge-opening loading specimen is placed in a high-pressure hydrogen environment, so that a current hydrogen-induced crack length is determined; finally, according to an initial applied stress intensity factor, the current hydrogen-induced crack length and a standard value of the hydrogen-induced crack length, a stress intensity factor threshold value of a material to be tested is determined. The method can not only obtain a more accurate hydrogen-induced lagging cracking stress intensity factor threshold value, but also effectively reduce the test cost.

The invention discloses a hydrogen-corrosion-resistant steel plate for a pipeline and a production method of the hydrogen-corrosion-resistant steel plate. The steel plate meets at least one of the following conditions: in a NACE TM0284 standard A solution environment, CLR is less than or equal to 10%, CTR is less than or equal to 3%, and CSR is less than or equal to 1%; in a NACE TM0177 standard stress corrosion test, the loading stress is 0.8 sigma s, and the surface of a tensile sample has no crack; in a 6.3 MPa pure hydrogen environment, the tensile strength, the ductility and the percentage reduction of area of the smooth sample are not lower than 90%, 85% and 80% in a nitrogen environment respectively; in a 6.3 MPa pure hydrogen environment, K1C of the step type compact tensile sample is greater than or equal to 110 MPa.m < 1 / 2 >. The production method comprises the steps of continuous casting, hot rolling and temperature control water cooling. And the initial cooling temperature of temperature control water cooling is Ar3-70 DEG C to Ar3-50 DEG C, and the final cooling temperature is Min (TVC, TVN)-50 DEG C to Min (TVC, TVN)-30 DEG C.

The invention discloses L415MH pipeline steel and a preparation method thereof. The steel meets any of the following items: in a NACE TM0284 standard A solution environment, CLR is less than or equal to 10%, CTR is less than or equal to 3%, and CSR is less than or equal to 1%; a stress corrosion test is carried out according to the NACE TM0177 standard, the loading stress is 0.8 sigma s, and the surface of a tensile sample has no crack; in a 6.3 MPa pure hydrogen environment, the tensile strength, the ductility and the percentage reduction of area of the smooth sample are respectively greater than or equal to 90%, 80% and 75% in a nitrogen environment; in a 6.3 MPa pure hydrogen environment, K1C of the step type compact tensile sample is greater than or equal to 100 MPa.m < 1 / 2 >. According to the preparation method, in temperature-controlled water cooling after hot rolling, the initial cooling temperature is Ar3-50 DEG C to Ar3-30 DEG C, and the final cooling temperature is Min (TVC, TVN)-300 DEG C to Min (TVC, TVN)-270 DEG C.

The invention provides a crack length measuring system, relates to the technical field of fatigue cracks, and can measure the crack length in a specific environment. The system comprises a reaction kettle used for sealing a compact tensile CT sample, the CT sample is clamped on a fatigue testing machine, and the CT sample comprises a crack area. And the gas pumping and discharging device is used for pumping and discharging the gas in the reaction kettle to a vacuum state and filling the target experimental environment gas into the reaction kettle. And the direct current potential drop system DCPD system is used for measuring the crack length of the crack area in the CT sample at multiple moments.

The present application relates to the field of crack propagation test of stress corrosion, corrosion fatigue and fracture toughness, and particularly relates to a system for in-situ monitoring of crack length of compact tension specimen in harsh corrosion environment and a use method thereof. Two short sides of a T-shaped connecting assembly are fixed at both sides of a center crack opening of a CT specimen, a long side head of the T-shaped connecting assembly is inserted into a through hole on one side of a turning block, a displacement transmission rod is clamped by a separated ohmic clamp on the other side of the turning block, an inductive core on the upper end of the displacement transmission rod is threadedly connected to a LVDT inserted into a high-temperature and high-pressure kettle cover, a spacer is threadedly and tightly sealed on the high-temperature and high-pressure kettle cover, a water cooling jacket is arranged outside the spacer, the LVDT is connected to the upper end of the spacer through a thread and a sealing washer, and the LVDT is connected to a data collector. The present application uses the flexibility method to obtain a relationship expression between the opening displacement of the crack opening of the CT specimen and the crack length, so that the crack length of the CT specimen in the harsh corrosion environment can be monitored in-situ.

The present invention relates to the field of metallic material measurement, and specifically to a method and model for predicting the fatigue crack growth rate of pipeline steel in a hydrogen-mixed environment. In this prediction method, multiple compact tension test specimens of the pipeline steel to be measured are prepared, and fatigue crack growth tests are then performed on the compact tension test specimens in a nitrogen environment and in environments with different hydrogen mixing ratios. The fatigue crack growth rates and corresponding stress intensity factor ranges are then obtained and fitted to obtain constant terms, and a fatigue crack growth prediction model for the pipeline steel to be measured in a hydrogen-mixed environment is constructed. Finally, the fatigue crack growth rate of the pipeline steel can be predicted based on the fatigue crack growth prediction model and the hydrogen mixing ratio. The present invention allows for the construction of a fatigue crack growth prediction model for the pipeline steel to be measured in a hydrogen-mixed environment by simply performing fatigue crack growth tests in a nitrogen environment and in environments with a few different hydrogen mixing ratios, thereby enabling predictions to be made, effectively shortening the prediction test period and ensuring the safety of testers and equipment.

The present application belongs to the field of metal material testing and specifically discloses a method and model for predicting the fatigue crack growth rate of pipeline steel in a hydrogen-doped environment. The prediction method comprises the following steps: processing multiple compact tensile specimens of the pipeline steel to be tested, and then conducting fatigue crack growth tests on the compact tensile specimens in a nitrogen environment and at different hydrogen-doping ratios to obtain the fatigue crack growth rate and the corresponding stress intensity factor range and fitting the constant term. ， This method establishes a fatigue crack growth prediction model for pipeline steel under a hydrogen-doped environment. Ultimately, given the hydrogen doping ratio, the fatigue crack growth rate of the pipeline steel can be predicted based on the fatigue crack growth prediction model. This application only requires conducting fatigue crack growth tests in a nitrogen environment and a few environments with different hydrogen doping ratios to establish a fatigue crack growth prediction model for pipeline steel under a hydrogen-doped environment, thereby achieving predictions. This effectively shortens the prediction test cycle and ensures the safety of test personnel and equipment.

The present application relates to hydrogen energy transportation and material mechanical property testing technical field, specifically to a kind of high-pressure hydrogen environment hydrogen transportation pipeline material constant load fracture toughness efficient determination method, by precasting the crack depth corresponding to different stress intensity factor level in two compact tension specimens respectively, and using orifice plate to mechanically connect the two, make two specimens simultaneously bear the same constant tensile load in high-pressure hydrogen environment, and after the fracture of any specimen, load can still be stably transmitted to another specimen, so that the crack propagation response data under two different crack depths in single constant load test is simultaneously obtained.The present application effectively utilizes the test time resources, and makes the test efficiency more than doubled.