84 results about "Delayed fracture" patented technology

The invention relates to a delayed fracture resistant non-quenched and tempered 14.9-grade high-strength cold heading steel wire rod and a preparation method thereof. The wire rod comprises the following chemical components: 0.33%-0.55% of C, less than or equal to 0.10% of Si, 1.5%-2.3% of Mn, 0.4%-0.6% of Cr, 0-0.04% of Nb, 0-0.1% of V, 0-0.1% of Ti, 0.004%-0.008% of B, more than or equal to 0.020% of Als, less than or equal to 0.040% of Alt, less than or equal to 0.015% of P, less than or equal to 0.010% of S, less than or equal to 1ppm of H and the balance of Fe and impurity elements. Fine control is adopted in the steelmaking process, the H content is strictly controlled to be lower than 1 ppm, a hydrogen trap is manufactured by adding microalloy elements such as Nb, V and Ti, and the delayed fracture resistance is improved; the air cooling speed of the rolled hot-rolled wire rod is precisely controlled, so that the structure of the hot-rolled wire rod is lath bainite, and high strength is realized by utilizing a medium-carbon bainite structure; the finished wire rod has high strength, high plasticity, excellent low-temperature impact toughness and good delayed fracture resistance.

A method for manufacturing high-strength, hydrogen-embrittlement-resistant bolts based on microsphere shot peening, and the bolts themselves, are disclosed. The manufacturing method includes: S1, cold heading and thread rolling of alloy structural steel billets to obtain bolt forming parts; S2, surface cleaning of the bolt forming parts, followed by overall surface peening with microspheres driven by high-pressure air; after overall peening, targeted strengthening peening treatment is performed on stress concentration areas such as thread roots, undercut grooves, and flange transition corners to obtain reinforced bolt parts; S3, the reinforced bolt parts are cleaned, dried, and phosphated to obtain finished bolt parts. This design, through a "overall + targeted" composite microsphere shot peening strategy, introduces a uniform residual compressive stress field and a micron-level fine-grained plastic deformation layer on the bolt surface, forming a thicker strengthening layer in stress concentration areas, significantly improving the fatigue strength and delayed fracture resistance of high-strength bolts, while ensuring uniform surface roughness and stable assembly friction coefficient.

The present invention provides a steel sheet having a tensile strength of 1310 MPa or more and excellent press formability in a steel having a martensite structure as a main body and excellent delayed fracture resistance. The steel sheet is characterized by having a composition consisting of, in mass%, C: 0.12% to 0.40%, Si: 1.5% or less, Mn: 1.7% or less, P: 0.05% or less, S: 0.010% or less, sol. Al: 1.00% or less, N: 0.010% or less, Ti: 0.002% to 0.080%, and B: 0.0002% to 0.0050%, with the remainder being Fe and inevitable impurities, and a metal structure in which the area ratio of a martensite to the entire structure is 95% or more, the length L S of sub-block boundaries in the martensite is 0.5 to 2.0 μm, and the ratio L B / L S of the length L B of the sub-block boundaries to the length L of the block boundaries satisfies a prescribed formula (1), and the tensile strength is 1310 MPa or more.

The invention provides a hydrogen-induced delayed fracture resistant ultrahigh-strength steel plate and a preparation method thereof, and belongs to the technical field of metal materials. The hydrogen induced delayed fracture resistant type ultrahigh strength steel plate comprises the following components in percentage by mass: 0.18 to 0.25 percent of C, 2.0 to 2.8 percent of Mn, 0.3 to 1.0 percent of Si, 3.0 to 6.0 percent of Al, 0.001 to 0.015 percent of Ce, 0.05 to 0.25 percent of Mo, 0.02 to 0.10 percent of Ti, less than or equal to 0.01 percent of P, less than or equal to 0.005 percent of S, less than or equal to 0.004 percent of N and the balance of Fe and inevitable impurities. The steel plate with ultrahigh strength, high elongation and excellent hydrogen-induced delayed fracture resistance can be stably produced through rare earth microalloying and precise structure regulation and control in cooperation with a proper process.

The invention discloses a high-strength bolt, a steel material and a preparation method of the high-strength bolt, and relates to the technical field of alloy smelting, and the high-strength bolt is characterized by comprising the following components in percentage by mass: 0.18%-0.22% of C, 0.08%-0.12% of Nb, 0.02%-0.05% of Al, 0.004%-0.02% of Ti, 0.05%-0.08% of V, 0.0001%-0.002% of S, 0.00%-0.05% of Cu, 0.70%-0.90% of Mn, 0.20%-0.30% of Si, 0.90%-1.10% of Cr, 0.30%-0.50% of Ni, 0.15%-0.30% of Mo and the balance of Fe. The high-strength steel material has the advantages that the components of the high-strength steel material are optimized, an alloy structure composed of fine and uniform martensite, nanoscale precipitated phases and low internal stress is obtained, and the effects of improving the strength and the delayed fracture resistance are achieved.

The present invention provides a resistance spot welding method that can alleviate residual stress during resistance spot welding and can suppress occurrence of delayed fracture. In the resistance spot welding method, a pair of plate-shaped members having a hat-shaped cross section with a top plate portion and a pair of vertical wall portions extending from both ends of the top plate portion are overlapped, and resistance spot welding is performed on the pair of plate-shaped members. In the resistance spot welding method, there are included a step of detecting a contact load required for mutual contact of a portion where a gap between the pair of vertical wall portions becomes the largest due to a part tolerance of the plate-shaped members after the top plate portions of the pair of plate-shaped members are overlapped and resistance spot welding is performed on the top plate portions; and a step of setting a pressing force of a pair of electrodes that sandwich the pair of vertical wall portions during resistance spot welding on the overlapped pair of vertical wall portions in such a manner that the pressing force of the electrodes is greater than half of the contact load and smaller than the contact load, and performing resistance spot welding on the pair of vertical wall portions with the pressing force of the electrodes.

The application relates to the technical field of denture welding processing, in particular to a flexible support fastening component for denture root part in denture welding processing, which comprises a support table, an arc-shaped groove for loading a denture root part component is arranged on the inner side of the support table, a support assembly is arranged below the support table, and a flexible support fastener for fixing the denture root part component is arranged above the support table. The flexible support fastener comprises a support seat, a sliding seat is slidably arranged in the support seat, a positioning shaft with a conical top is detachably arranged on the top side of the sliding seat, and a return spring is fixed to one side of the sliding seat. The flexible support fastening component for the denture root part in the denture welding processing can pull the end part of the e-bar, effectively eliminates welding residual stress, prevents post-welding deformation and delayed fracture, the pulling force can effectively eliminate the internal stress of the e-bar welding position caused by high welding temperature, deformation and cracking of the e-bar caused by stress concentration are avoided, and the structural stability of the e-bar after welding is improved.

The present application relates to the technical field of metallurgical materials, and particularly relates to a rare earth micro-alloyed cold heading steel wire rod for 14.9-grade ultra-high strength fasteners and a preparation method thereof. Through reasonable alloy component design, synergistic micro-alloying of rare earth elements and precise control of process parameters, the plasticity and delayed fracture resistance of the fastener are significantly improved while meeting the ultra-high strength requirement of the 14.9-grade fastener, and the stability of rare earth addition and the industrial applicability of the process are realized. After the fastener prepared by the present application is subjected to a quenching and tempering heat treatment, the tensile strength is greater than or equal to 1400 MPa, the yield strength is greater than or equal to 1260 MPa, the elongation after fracture is greater than or equal to 9%, the reduction of area is greater than or equal to 48%, the core hardness is HRC 44-49, and the mechanical performance requirement of the 14.9-grade fastener is fully met.

Provided is a high-strength steel sheet having excellent member strength, stretch flangeability, bendability, and delayed fracture resistance under atmospheric corrosion and in a coated state. The steel sheet has a prescribed component composition, microstructure and the like, the average value [tau q] of the plastic deformation initiation stress [tau q] measured by nanoindentation at a position 1 / 4 of the sheet thickness of the steel sheet is 2.50-4.10 GPa, the standard deviation [sigma q] of the tau q is 0.30 GPa or less, and the average value [tau q] of the plastic deformation initiation stress [tau q] is 0.30 GPa or less. When [tau s] is the average value of the plastic deformation start stress [tau] s measured by the nanoindentation method at a position 10 [mu] m from the surface of the steel sheet, the ratio of measurement points less than 0.85 * [tau s] is 25.0% or less.

Provided are a steel sheet and a member, having high strength and high delayed fracture resistance, and methods for manufacturing the steel sheet and the member. The steel sheet has a specific chemical composition and a microstructure in which the area fraction of martensite is 95% to 100%, with the balance being one or more of bainite, ferrite, and retained austenite. In the steel sheet, prior-austenite grains have an average grain size of 18 μm or less, 90 mass % or more of the total content of Nb and Ti contained is present as a carbonitride having an equivalent circular diameter of 100 nm or more, and a Nb carbonitride and a Ti carbonitride, having an equivalent circular diameter of 1.0 μm or more, are present at a rate of 800 pieces / mm2 or less in total. The steel sheet has a tensile strength of 1310 MPa or more.

The present invention provides steel plates and components having a tensile strength (TS) of 980 MPa or more, and excellent formability, impact resistance, chemical conversion treatability, and delayed fracture resistance, as well as methods for manufacturing the same. It has a specific chemical composition, and the steel sheet surface coverage rate of Si-based oxides is 1% or less, At the 1 / 4 position of the plate thickness, the area fraction of ferrite is 3% or more and 30% or less, The area fraction of tempered martensite is 60% or more and 94% or less, The volume fraction of retained austenite is 3% or more and 15% or less, The steel sheet has a structure in which the area fraction of the remaining structure is 10% or less, and the ferrite has low-Mn ferrite in which the Mn concentration is less than 0.85 times the Mn content of the steel sheet, and high-Mn ferrite in which the Mn concentration is 0.85 times or more the Mn content of the steel sheet, and the proportion of the high-Mn ferrite in the ferrite is 20% or more and 90% or less in area fraction.

Provided is a high-strength hot-rolled steel sheet having excellent delayed fracture resistance and excellent flatness in addition to high stretch flangeability while maintaining a high strength with a tensile strength of 1310 MPa or above.　The high-strength hot-rolled steel sheet has: a predetermined component composition; a steel structure in which the area ratio of tempered martensite is 80% to 100%, the area ratio of bainite is 0% to 20%, the total area ratio of the remaining structure is 0% to 10.0%, and the number density of metastable carbides having a major-axis length of 10 nm or more is 5 × 1010 / mm3; a steepness of 2.0% or less; a tensile strength of 1310 MPa or more; and high stretch flangeability and excellent delayed fracture resistance.

The application provides an anti-hydrogen embrittlement stainless steel and a preparation method and application thereof, and relates to the technical field of special stainless steel.The anti-hydrogen embrittlement stainless steel provided by the application contains the following elements in percentage by mass: 0.05-0.08% of C, 7-9% of Mn, 13-16% of Cr, 8-10% of Ni, 0.8-1% of Cu, 2-3% of Co, 0.2-0.4% of N, 1-2% of RE, 0.01-0.05% of impurities and the balance of Fe; the RE contains at least one of La, Ce and Y. The multiple metal elements and non-metal elements are used to cooperate and jointly act, the Mn and N can stabilize the austenite structure, can improve the structural strength and toughness of the anti-hydrogen embrittlement stainless steel, and can make the stainless steel have the anti-hydrogen embrittlement capability, and the anti-delayed fracture performance is improved.

This invention provides a steel plate with a tensile strength of 1310 MPa or higher, which achieves excellent compressibility in a steel primarily composed of martensite with excellent resistance to delayed fracture. The steel plate is characterized by having the following composition and microstructure, wherein the composition, by mass%, contains C: 0.12%–0.40%, Si: less than 1.5%, Mn: greater than 1.7% and less than 3.5%, P: less than 0.05%, S: less than 0.010%, sol.Al: less than 1.00%, N: less than 0.010%, Ti: 0.002%–0.080%, and B: 0.0002%–0.0050%, with the remainder being Fe and unavoidable impurities. The martensite in the microstructure has an area fraction of 85% or more relative to the overall microstructure, and the length L of the subplate boundaries in this martensite is... S Length L of the lath boundary B The ratio of L S / L B It satisfies the specified formula (1) and has a tensile strength of 1310 MPa or more.

A thin, high-strength steel sheet with a tensile strength of 1180 MPa or more is provided, exhibiting excellent malleability, excellent delayed fracture resistance from a base steel sheet, and excellent delayed fracture resistance from a projection weld, along with a method for its manufacture. The thin, high-strength steel sheet has a chemical composition containing C, Si, Mn, P, S, Al, and N, with the remainder consisting of Fe and unavoidable impurities, and a complex structure containing ferrite, quenched martensite, and bainite, wherein a volume fraction of the total quenched martensite and bainite contains five or more carbides with a particle size of 0.1 µm or more.0 µm or less in a grain with respect to the total quenched martensite and bainite is 85% or more, whereas the mass % of C and the mass % of Mn in a region of 20 µm or less in the thickness direction from a surface of the steel sheet is 20% or less with respect to the mass % of C and the mass % of Mn in a region of 100 µm or more and 200 µm or less from the surface of the steel sheet.

Provided is a technology for evaluating the influence of a strain amount in a post-trimmed portion before trim forming, on a delayed fracture characteristic of a sheared end surface. A delayed fracture characteristic evaluation method for evaluating a delayed fracture characteristic of a sheared end surface of a metal sheet (3) made of a high-tensile steel sheet includes: producing a test piece (1) having the sheared end surface from the metal sheet (3) having at least a portion to which a plastic strain is applied by performing shearing on the metal sheet at a position including the portion to which the plastic strain is applied; leaving the test piece (1) under a hydrogen charging environment with a load stress being applied to the sheared end surface of the test piece (1); and evaluating the delayed fracture characteristic of the sheared end surface.

The invention relates to the technical field of bolt production, and particularly discloses a high-strength bolt machining process and device. Comprising the following steps: S1, material selection: selecting an alloy steel blank containing C, Si, Mn, Cr, Mo, V and the balance of Fe; s2, cold heading forming is conducted, specifically, the alloy steel blank is placed in a multi-station cold heading machine, and a bolt blank is formed through continuous cold heading and forging; s3, heat treatment is conducted, specifically, the bolt blank is subjected to quenching treatment and then subjected to tempering treatment, and a bolt base body is obtained; and S4, surface treatment is conducted, specifically, phosphating treatment is conducted on the surface of the bolt base body in sequence to form a phosphating layer, the composite coating is coated, and the high-strength bolt is obtained. The high-strength bolt machining process can be used for manufacturing connecting components requiring high reliability under complex working conditions such as heavy load, vibration and impact, and the high-strength bolt machining process has the advantages that the toughness, fatigue resistance and delayed fracture resistance are improved while high strength is kept.

The application discloses a hot-rolled wire rod 30Si2Mn for prestressed steel rods and a preparation method thereof. The hot-rolled wire rod comprises the following components in percentage by weight: C: 0.28%-0.33%, Si: 1.55%-1.70%, Mn: 0.65%-0.80%, P: <=0.020%, S: <=0.020%, Ni: <=0.20%, Cr: <=0.20%, Cu: <=0.20%, H <=0.0003%, and the balance of Fe and inevitable impurity elements. By designing the optimal component system, optimizing the controlled rolling and controlled cooling process, improving the mechanical properties of the wire rod, prolonging the wire rod online slow cooling time by taking process measures, releasing hydrogen and internal stress, controlling the hydrogen content below 3ppm, and achieving the section shrinkage rate above 50% after natural aging, hydrogen-induced delayed fracture of the prestressed steel rod is effectively avoided, and the safety of the construction engineering is improved.

The invention discloses 15.8 grade ultrahigh strength delayed fracture resistant steel for fasteners and a manufacturing method of the 15.8 grade ultrahigh strength delayed fracture resistant steel. The 15.8 grade ultrahigh strength delayed fracture resistant steel comprises, by mass, 0.40%-0.50% of C, 0.15%-0.35% of Si, 0.50%-1.00% of Mn, smaller than or equal to 0.015% of P, smaller than or equal to 0.010% of S, 0.90%-1.20% of Cr, 0.10%-0.20% of Ni, 0.70%-0.90% of Mo, 0.20%-0.40% of V, 0.02%-0.08% of Nb, 0.010%-0.020% of Ti, 0.020%-0.040% of Al, 0.0040%-0.0080% of N and the balance Fe and inevitable impurity elements. The manufacturing process comprises the steps of converter smelting, LF refining, RH vacuum degassing, continuous casting, heating and cogging, flaw detection and coping, high-speed wire rolling, follow-up treatment and the like, a lower bainite structure is obtained after a wire rod is subjected to annealing, wire drawing, cold heading and isothermal quenching heat treatment, and the mechanical properties of the lower bainite structure are as follows: the tensile strength is 1500-1670 MPa, the yield strength is larger than or equal to 1200 MPa, the ductility is larger than or equal to 9%, and the percentage reduction of area is larger than or equal to 48%; and the material has excellent delayed fracture resistance, and is suitable for high-end fields such as aerospace, rail transit and the like.

This invention provides a high-strength bolt steel material resistant to delayed fracture and a bolt manufacturing method, belonging to the field of alloy steel technology. The effective components and contents of the steel material are as follows: C: 0.36-0.43%; Si: 0.15-0.35%; Mn: 0.40-1.00%; P: P≤0.012%; S: S≤0.008%; Cr: 0.40-1.00%; Mo: 0.15-0.35%; W: 0.15-0.35%; V: 0.05-0.15%; Nb: 0.02-0.07%; Cu: 0.20-0.50%, with the balance being Fe. The V, Mo, and W elements satisfy the relationship with the strengthening parameter θ: θ=V(%)+0.5Mo(%)+0.75W(%), 0.35≤θ≤0.42. This invention improves the strength of steel materials. By controlling the reasonable strengthening parameter θ and performing appropriate deformation direct quenching followed by high-temperature tempering, it promotes the large-scale dispersion precipitation of nano-sized MC and M2C carbides. While achieving a strength level of 1400MPa, it also improves the resistance to delayed fracture, enabling the production of 14.9 grade high-strength bolts. It eliminates the need for re-austenitizing heating and quenching after bolt forming, resulting in simplified processes, energy saving, and reduced consumption, which aligns with the green and low-carbon development trend.

A plated steel sheet for hot press forming with improved hydrogen delayed fracture properties is disclosed. The disclosed plated steel sheet includes a base steel sheet, and a plating layer formed on a surface of the base steel sheet and including, by weight, Si: 5.0 to 15.0%, Zn: 10.0 to 30.0%, Fe: 4.0 to 12.0%, and the remainder including Al and unavoidable impurities.

The invention relates to the technical field of bolts, and provides a high-strength anti-theft bolt and a preparation method thereof.The bolt is composed of C, Si, Mn, Cr, W, Mo, V, Re, Nb, Al, N, Ca, B, P, S and the balance Fe and other inevitable impurities. According to the technical scheme, the ultrahigh strength, excellent toughness and delayed fracture resistance of the bolt are achieved, the corrosion resistance of the bolt is improved, and the service life of the bolt is prolonged.

The invention discloses a test method for obtaining the relationship between the hydrogen concentration and the delayed cracking fracture time of high-strength steel, which comprises the following steps of: 1, preparing a sample, namely shearing a high-strength steel sample to be detected into a uniform size; 2, surface treatment: removing impurities on the surface of the sample; 3, preparing a hydrogen charging solution; step 4, electrochemical hydrogen charging: putting the sample subjected to surface treatment into a hydrogen charging solution, and performing hydrogen charging treatment on the sample for different times by adopting an electrochemical hydrogen charging method; 5, heating the hydrogen-filled sample to release hydrogen by using a thermal desorption method; 6, cryopreserving the sample; 7, after unfreezing is completed, the saturated hydrogen concentration of the hydrogen-filled sample is detected according to the hydrogen filling time, meanwhile, the relation between the hydrogen concentration and the time is recorded, and a hydrogen concentration change curve is established; 8, sample selection: selecting a plurality of samples with different hydrogen concentrations; step 9, sample stress loading test; step 10, preparing an acid solution; step 11, carrying out stress loading test on the hydrogen-filled sample; 12, recording delayed fracture time; step 13, making a fitting curve of the hydrogen concentration and the fracture time of the sample; according to the test method, the relevance between the hydrogen concentration of the sample and the fracture time can be obtained, and guidance is provided for improvement of the hydrogen resistance and safe use of the high-strength steel.

1. A coated steel sheet having a variable thickness in the rolling direction, with one portion rolled at a rolling ratio of 1 to 60% and at least another portion rolled at a different rolling ratio, wherein the coating comprises optional elements selected from zinc, silicon, magnesium, maximum 3.0 wt% iron, Ni, Zr, Hf, Sr, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr or Bi, each of which has a content by weight of less than 0.3 wt%, optionally maximum 100 ppm calcium, and maximum 0.02 wt% unavoidable impurities, the balance being aluminum, and wherein the coating has a thickness of 50 to 500 g / m2 on both sides combined before flexible rolling. 2 Coated steel sheets with variable thicknesses having coating weights of

Provided are: a high-strength hot-dip galvanized steel sheet which has a beautiful surface appearance without plating and which has excellent delayed fracture resistance; and a method for producing the high-strength hot-dip galvanized steel sheet. A hot-dip galvanized steel sheet provided with a base steel sheet and a zinc plating layer formed on the surface of the base steel sheet and having a plating layer adhesion amount per surface of 20-120 g / m2, the base steel sheet has a component composition containing, in mass%, 0.06 to 0.30% C, 0.01 to less than 3.00% Si, 1.5 to 3.5% Mn, 0.1% or less (excluding 0%) P, 0.003% or less (excluding 0%) S, 0.1% or less (excluding 0%) sol.Al, 0.007% or less (excluding 0%) N, and 0.003% or less (excluding 0%) O, with the remainder comprising Fe and unavoidable impurities. The total amount of hydrogen released at 200 DEG C to 350 DEG C (inclusive) when measured by temperature rise analysis is 0.20 ppm by mass or less.

To provide a construction method for more easily preventing the falling of a high-strength bolt due to delayed fracture than before.SOLUTION: The present invention relates to a method for preventing a drop of a high-strength bolt using a coating material for preventing the drop of the high-strength bolt attached to a predetermined attachment target, the method including a main material treatment of applying an anti-drop coating material having a tensile strength of 10 to 70N / mm2, an elongation at break of 100 to 500%, and a waterproofness of 3800 to 4500 g / m2 to a surface of the attachment target.SELECTED DRAWING: Figure 1

Provided is a high-strength steel sheet that is excellent in all of strain dispersibility, ductility, bendability, and delayed fracture resistance under atmospheric corrosion conditions in the coated state. The steel sheet has a predetermined chemical composition and microstructure, where an average value [τq] of plastic deformation initiation stress τq measured by a nanoindentation method at the ¼ thickness position of the steel sheet is 1.70 GPa or more and 3.30 GPa or less, standard deviation σq of the τq is 0.42 GPa or less, and when an average value of plastic deformation initiation stress τs measured by a nanoindentation method at the 10 μm position from the steel sheet surface is defined as [τs], the proportion of measurement points having values less than 0.85×[τs] is 30.0% or less.

Provided are: a hot-dip galvanized steel sheet which has high strength, a beautiful surface appearance without plating, and excellent delayed fracture resistance; and a method for producing the hot-dip galvanized steel sheet. A hot-dip galvanized steel sheet provided with: a base steel sheet having a component composition containing C, Si, Mn, P, S, sol.Al, N, and O in specific contents, or further containing specific optional elements in specific contents, with the remainder being Fe and unavoidable impurities, and a zinc-based plating layer formed on the surface of the base steel sheet, the zinc-based plating layer being formed on the surface of the base steel sheet, and the zinc-based plating layer being formed on the surface of the base steel sheet; the number of inclusions under specific conditions is 10 / mm2 or less, the hydrogen concentration HL of the base steel sheet is 0.30 ppm by mass or less and the hydrogen concentration HH is 0.20 ppm by mass or less, and the tensile strength is 780 MPa or more.

Provided is a high-strength steel sheet that is excellent in all of member strength, stretch flangeability, bendability, and delayed fracture resistance under atmospheric corrosion conditions in the coated state. The steel sheet has a predetermined chemical composition and microstructure, where an average value [τq] of plastic deformation initiation stress τq measured by a nanoindentation method at the ¼ thickness position of the steel sheet is 2.50 GPa or more and 4.10 GPa or less, standard deviation σq of the τq is 0.30 GPa or less, and when an average value of plastic deformation initiation stress τs measured by a nanoindentation method at the 10 μm position from the steel sheet surface is defined as [τs], the proportion of measurement points having values less than 0.85×[τs] is 25.0% or less.

Provided are: a method whereby delayed fracture at a sheared end surface can be evaluated with higher accuracy; and a method for producing a press-molded article using the method. A delayed fracture evaluation method for evaluating delayed fracture characteristics of a sheared end surface of a metal plate, in which a test is performed for the presence or absence of a delayed fracture when molding strain and loading stress are applied to the sheared end surface of the metal plate, and on the basis of the test, a delayed fracture is evaluated for two or more evaluation positions along the plate direction of the sheared end surface. Evaluation information for the presence or absence of a delayed fracture at the evaluation position under the molding strain and the loading stress is solved, and an evaluation criterion for the evaluation of the delayed fracture using the evaluation position, the molding strain, and the loading stress as variables is solved on the basis of the obtained evaluation information.