35 results about "Continuous cooling transformation" patented technology

A bake-hardening hot-rolled steel sheet which contains 0.01-0.2 mass% carbon, 0.01-2 mass% silicon, 0.1-2 mass% manganese, up to 0.1 mass% phosphorus, up to 0.03 mass% sulfur, 0.001-0.1 mass% aluminum, up to 0.01 mass% nitrogen, and 0.005-0.05 mass% niobium, the remainder comprising iron and unavoidable impurities. The microstructure of the sheet is a polygonal ferrite having an average particle diameter of 2-8 [mu]m and / or a continuous cooling transformation texture. The proportion of a solid solution of carbon and / or a solid solution of nitrogen present at the grain boundaries in the sheet is 0.28 or lower. Also provided is a process for producing the hot-rolled steel sheet which comprises heating a steel billet comprising those ingredients to at least a temperature satisfying the equation SRT ( DEG C) = 6670 / {2.26-log(%Nb)(%C-273 (A) rough-rolling the steel billet heated, finish-rolling the sheet under such conditions that the final temperature is in the range of from the Ar3 transformation point to (Ar3 transformation point + 100 DEG C), cooling it at a cooling rate of 80 DEG C / sec or higher for cooling from cooling initiation to 500 DEG C or lower, and winding it up.

The invention discloses production method for rapidly cooling a medium plate after rolling, belonging to the technical field of production of medium plates. The method comprises the following process steps of: adjusting an ultrafast cooling (UFC) frame to 300mm+h till the cross point between extension lines of upper and lower nozzles of equipment is positioned on the central line of a steel plate; during ultrafast cooling, setting cooling rules and parameters according to the steel kind, specification as well as required final cooling temperature and cooling speed of the steel plate; starting middle spraying, side spraying and air blowing to remove residual water from the surface of steel plate to increase the cooling uniformity, starting UFC equipment, and spraying water onto the steel plate with a gap nozzle and a ganged nozzle for cooling; and controlling the cooling speed and cooling termination point according to the CCT (Continuous Cooling Transformation) curve of steel, wherein the cooling speeds of steel plates of different thicknesses are 5-80 DEG C / s, and the final cooling temperature is controlled at 450-800 DEG C. The method has the advantages: by controlling the cooling process of the steel plate after rolling, control over phase change and organization is realized, and the aim of enhancing the roughness of the steel plate is fulfilled.

The invention is suitable for the field of low temperature rolling, and provides a control method of a rod and wire production line temperature control rolling process. The method comprises the steps of determining a critical phase change temperature and a critical cooling speed of a rolled piece generation phase change tissue according to the a steel type and a corresponding continuous cooling transition curve characteristic; calculating the water cooling time according to a length value of a water tank and a rolling speed of a rolled piece, and calculating a corresponding maximum water flow rate at the critical phase change temperature and the critical cooling speed according to the water cooling time and the cooling water temperature; acquiring an initial value of the water flow rate within the maximum water flow rate range; calculating a uniform temperature of the rolled piece according to a heat transfer relation of each node of the rolled piece; judging an absolute difference value of the uniform temperature and a target temperature to exceed a first preset threshold value, adjusting the water flow rate, re-calculating the uniform temperature, and calculating the water flow rate which cannot satisfy the first preset threshold value. By adopting the control method, the automatic derivation of process parameters in the temperature control rolling process can be realized, and the low efficiency and inaccuracy for a traditional method for referring to the existing engineering or experience in the prior art can be overcome.

The invention relates to the technical field of casting defect repair, in particular to a medium carbon steel defect removal method. The medium carbon steel defect removal method comprises the following steps: preheating of the surface of a casting, performing carbon arc gouging and magnetic powder detection in the high-temperature state, and then directly conducting recovery of the high-temperature casting by repair welding. According to the medium carbon steel defect removal method, an appropriate preheat temperature is selected for high-temperature carbon arc gouging according to the CCT (Continuous Cooling Transformation) curves of the medium carbon steel material together with the Ms point temperature, the Mf point temperature and gouging operability, so that the crack probability after carbon arc gouging is effectively reduced; and as high-temperature polishing, detection and recovery by repair welding are directly carried out after high-temperature gouging, the casting is further prevented from cracking, the preheating cost in the repair welding procedure is lowered and the production period is shortened.

The invention relates to a method for measuring the continuous cooling transition curve of an aluminum alloy, belonging to the technical field of nonferrous metal material preparation. The present invention distinguishes the precipitation temperature interval of the quenching reaction in the quenching process according to the change of the heat equivalent by recording the change of the heat equivalent in different temperature intervals; the present invention measures the aluminum alloy by applying the differential scanning calorimetry (DSC) The exothermic reaction during the quenching process is combined with the microstructure analysis and mechanical property testing to obtain the continuous cooling transformation curve of the aluminum alloy. Compared with other methods, the method of the present invention is capable of obtaining precise cooling curves in a certain cooling interval and distinguishing the starting and ending temperatures of different quenching-induced precipitation phases. The continuous cooling transition curve obtained by the invention has the advantages of high precision, great guiding significance and the like.

The invention provides a high-strength hot-rolled steel plate for line pipes which is excellent in low-temperature toughness and a process for the production of the same. A steel plate which contains by mass C: 0.01 to 0.1%, Si: 0.05 to 0.5%, Mn: 1 to 2%, P: 0.03% or below, S: 0.005% or below, O: 0.003% or below, Al: 0.005 to 0.05%, N: 0.0015 to 0.006%, Nb: 0.005 to 0.08%, and Ti: 0.005 to 0.02% with the proviso that relationships: N-14 / 48xTi>0% et Nb-93 / 14x(N-14 / 48xTi)>0.005% are satisfied and with the balance consisting of Fe and unavoidable impurities, characterized in that the microstructure is a continuous cooling transformation structure, that the reflected X-ray intensity ratio between {211} plane and {111} plane which are parallel to the plate face, {211} / {111} ratio, in the texture in the thicknesswise central part of the plate is 1.1 or above, and that the density of carbonitride precipitate of Nb and / or Ti in the grains is 10<17> to 10<18 >pieces / cm<3>.

The invention provides a method for formulating a water-air alternate time-controlled quenching process. The method comprises the following steps of: step 1, predicating a structure composition of a part with required performance according to the performance detection part of an alloy steel piece and specific performance requirements; step 2, according to the super-cooled austenite isothermal cooling transformation curve or the super-cooled austenite continuous cooling transformation curve of a material, acquiring the longest cooling time or the minimum cooling speed which the structure needs to reach a certain temperature; step 3, dividing an alloy steel piece into a cooling speed control area and a slow cooling area along a section from the surface to the centre; step 4, determining the water-air alternation times of the cooling speed control area, and a water-cooling time and an air-cooling time each time; and step 5, determining the water-air alternation times of the slow cooling area, and a water-cooling time and an air-cooling time each time. With the adoption of the method provided by the invention, the alloy steel piece can obtain required performance or structure on the premise of avoiding cracking; and the method is suitable for a quenching treatment for the alloy steel pieces with various ingredients.