40results about How to "Improved delayed fracture resistance" patented technology

There are provided a steel for warm working, to be subjected to warm working as various structures, components of cars, and the like, a warm working method thereof, and a steel material and a steel component obtainable from the warm working method.

[Solving Means] A steel is to have a particle dispersion type fiber structure formed in the matrix by warm working. The steel is characterized in that the total amount of the dispersed second-phase particles at room temperature is 7×10⁻³ or more in terms of volume fraction, and the Vickers hardness (HV) is equal to or larger than the hardness H of the following equation (2):

H=(5.2−1.2×10⁻⁴λ)×10²  (2)

when the steel is subjected to any of annealing, tempering, and aging treatments in the as-unworked state under conditions such that a parameter λ expressed by the following equation (1):

λ=T(log t+20)(T; temperature(K), t; time(hr))  (1)

is 1.4×10⁴ or more in a prescribed temperature range of 350° C. or more and Ac1 point or less. This steel is taken as the steel for warm working.

Disclosed is a high-strength bolt having a tensile strength of 1,200 N/mm² or more and superior in delayed fracture resistance and relaxation resistance, prepared by wire-drawing a bolt steel containing the following elements: C: 0.5 to 1.0% (mass %, the same shall apply hereinafter), Si: 0.55 to 3%, Mn: 0.2 to 2%, P: 0.03% or less (but not 0%), S: 0.03% or less (but not 0%), and Al: 0.3% or less (but not 0%), and containing proeutectoid ferrite, proeutectoid cementite, bainite and martensite at a total areal rate of less than 20% and pearlite in balance; cold-heading the wire into a bolt shape; and then bluing the bolt in a temperature range of 100 to 500° C.

The invention relates to low-carbon bainitic cold-work-strengthened non-quenched and tempered steel with excellent delayed fracture resistance, which belongs to the technical field of alloy steel, and is applicable to manufacturing grade 10.9 high-strength bolts with tensile strength above 1000MPa. The steel comprises the following chemical components by weight percent: 0.06-0.15% of C, not more than 0.10% of Si, 1.80-2.40% of Mn, not more than 0.010% of P, not more than 0.008% of S, 0.10-0.40% of Cr, 0.0005-0.003% of B, 0.05-0.15% of V, 0.01-0.08% of Ti, 0.005-0.03% of RE, 0.01-0.05% of Al, 0.004-0.01% of N and the balance of Fe and other inevitable impurities; simultaneously, the elements of V and Ti further meet the following relational expression of a strengthening parameter theta: V(%) plus Ti(%) is not less than 0.10 and not more than 0.20; and a metallurgical structure is a granular bainite. The low-carbon bainitic cold-work-strengthened non-quenched and tempered steel has the advantages of not only having good plasticity and cold working performance, but also having excellent delayed fracture resistance and being used for manufacturing the grade 10.9 high-strength bolts with the delayed fracture resistance.

The invention relates to a nano/superfine medium-manganese TRIP (transformation induced plasticity) steel plate and a warm-rolling preparation method thereof, belonging to the technical field of ultrahigh-strength steel. The nano/superfine medium-manganese TRIP steel plate comprises the following chemical components in percentage by weight: 0.17-0.25wt.% of C, 0.00-0.50wt.% of Si, 5.00-7.00wt.% of Mn, 1.00-1.50wt.% of Al, 0.014-0.03wt.% of N, 0.00-0.06wt.% of Nb, 0.00-0.25wt.% of Mo, and the balance of Fe and inevitable impurities. The preparation method comprises the following steps: smelting, forging, carrying out hot rolling, and carrying out warm rolling to obtain the nano/superfine medium-manganese TRIP steel plate; and carrying out heat treatment on the steel plate to obtain the nano/superfine medium-manganese TRIP heat-treated steel plate. By using the warm-rolling technique instead of the typical technique for producing manganese steel, the method provided by the invention has the advantages of simple technique, short production cycle and controllable plate shape. The prepared steel plate has a nano/superfine structure, has the advantages of high strength and favorable properties, and satisfies the target requirements of resource saving, energy consumption reduction, light weight and crash safety enhancement for automobile industry.

The invention relates to the technical field of cold heading steel, and particularly discloses an ultrahigh-strength locking riveting rivet cold heading steel wire rod and a preparing method thereof.The cold heading steel wire rod comprises chemical components including, by weight percent, 0.33-0.38% of C, smaller than or equal to 0.30% of Si, 0.80-1.10% of Mn, smaller than or equal to 0.020% ofP, smaller than or equal to 0.020% of S, 0.10-0.30% of Cr, 0.010-0.050% of Nb, 0.020-0.050% of Ti, 0.020-0.050% of Al, 0.0010-0.0035% of B and the balance Fe and inevitable impurity elements. In the preparing process, RH vacuum refining is used for removing hydrogen in steel, a hot-rolled blank is placed in a slow cooling pit, the hydrogen content is further reduced, through heating and rolling procedure control, an obtained hot-rolled wire rod has easy spheroidizing annealing and good cold machining performance, and the toughness and delayed fracture resisting performance after heat treatmentare good.

If an area that is formed concentrically inward from a surface of a wire rod and whose cross section ratio with respect to the cross sectional area of a cross section of the wire rod is between 13% and 56% is defined as area I, an area that widens concentrically about the central axis of the wire rod and whose cross section ratio with respect to the cross sectional area of the wire rod is between 3% and 11% is defined as area III, and an area between area I and area III is defined as area II, then area I is a first negative segregation portion where the degree of C segregation with respect to the average C concentration of the wire rod is between 0.75 and 0.95, area II is a positive segregation portion where the degree of C segregation is between 1.00 and 1.10, area III is a second negative segregation portion where the degree of C segregation is between 0.80 and 0.95; and the wire rod has a sandwich structure in which the first negative segregation portion, the positive segregation portion, and the second negative segregation portion are placed in order from the surface.

The invention discloses a nut production process. The process comprises the following steps that S1, through a casting process, a workblank part is made, and the workblank part comprises, by weight ratio, 0.28 to 0.32 of C, 0.32 to 0.45 of Mn, 0.05 to 0.09 of Zn, 0.15 to 0.25 of Si, 0.01 to 0.03 of La, not larger than 0.015 of P, not larger than 0.015 of S, 0.50 to 1.20 of Ni, 0.15 to 0.25 of Sn,0.15 to 0.25 of Al, 0.2 to 0.5 of Mo and the balance iron; S2, the workblank part is put into a mold cavity, cold heading extrusion molding is carried out, and the nut workblank is made; S3, the nut workblank is turned and tapped; S4, heat treatment is carried out; S5, surface treatment is carried out, cleaning oil removal is carried out, blackening treatment is carried out, static electricity manner is adopted to spray an anti-corrosion agent to the nut, and the sprayed nut is cured to obtain a nut finished product. The nut produced through the nut production process has the hardness value and strength value needed by the high-strength nut, is not prone to being corroded and long in service life.

Provided are a high-strength galvanized steel sheet having excellent delayed fracture resistance by reducing the diffusible hydrogen content in the steel and a method for producing the same.

The high-strength galvanized steel sheet includes a steel sheet having a prescribed composition and a microstructure including martensite and tempered martensite, the total area fraction of the martensite and the tempered martensite being 30% or more, and a galvanizing layer formed on the surface of the steel sheet. The diffusible hydrogen content in the high-strength galvanized steel sheet is 0.50 wt. ppm or less. The half-width of the hydrogen release peak of the high-strength galvanized steel sheet is 70° C. or less. The diffusible hydrogen content and the half-width of the hydrogen release peak are determined by a prescribed analysis method.

The invention discloses cold forging steel for a high-strength large-dimension bolt and a production method thereof. The production method comprises a heating process, a rolling process and a cooling process. Steel billet adopted by the production method consists of the following chemical components in percentage by weight: 0.17-0.23% of C, 0.70-1.00% of Mn, 0.30% of Si, less than or equal to 0.025% of P, less than or equal to 0.025% of S, 0.65-1.20% of Cr, 0.0008-0.0050% of B, 0.01-0.06% of Ti and the balance of Fe and inevitable impurity elements; and in the heating process, the steel billet is heated to 1000-1100 DEG C and the temperature-preserving time is 80-130 minutes. According to the production method, by optimizing components and the processes, a produced coil has relatively low strength and hardness, meets process properties of carrying out cold processing in a non-annealed mode, has good hardenability, meets large-dimension bolt hardenability requirements, and further has certain delayed fracture resistance; and a microstructure consists of uniform ferrites and pearlite, has tensile strength of 500-560 MPa, and area reduction greater than or equal to 60%, so that 1/3 cold upsetting is qualified, and the production cost is low. The cold forging steel has good cold processing performance and hardenability.

The invention discloses a high-strength bolt machining method. The method comprises the step of S1, a rod blank is prepared through a casting process, wherein the rod blank is controlled to comprisesthe following chemical components of, by weight, 0.28-0.32% of C, 0.32-0.45% of Mn, 0.05-0.15% of V, 0.15-0.25% of Si, 0.01-0.03% of W, less than or equal to 0.015% of P, less than or equal to 0.015%of S, 0.50-1.20% of Ni, 0.15-0.25% of Sn, 0.15-0.25% of Cu, 0.15-0.35% of Mo and the balance iron. A bolt produced by the high-strength bolt machining method reaches the hardness value and the strength value which are required by the high-strength bolt, the delay fracture and the fatigue fracture problems of the bolt under the high strength are solved, during use, connection is reliable, breakageis not prone to occurrence, the service life of the bolt is prolonged, and the use requirements of all industries in the society on the high-strength bolt are met.