65results about How to "Short residence time at high temperature" patented technology

The invention discloses a method for preparing a bimetal composite plate by stirring friction braze welding. The method comprises that: a plate with small hardness is used as a covering layer metal plate; a plate with high hardness is used as a base layer metal plate; the covering layer metal plate and the base layer metal plate are horizontally fixed on a working platform surface in a lap joint mode; solders which can generate eutectic reaction with one of the upper / base layer metal plates are preset between the upper / base layer metal plates; a non-needle type cylinder friction device is arranged over the covering layer metal plate; the non-needle type cylindrical friction device is made to rotate and be pressed to be closely contacted with the surface layer of the covering layer metal plate, but not penetrate the covering layer metal plate, and the non-needle type cylindrical friction device rotates in the original position or moves forward along the surface of the covering layer metal plate while rotating; by utilizing frictional heat to melt the solders, the upper / base layer metal plates are both quickly melted in the solders, thereby achieving excellent interface combination; and the excessive solders are squeezed out, and a thin and dense soldering seam is formed, so that the bimetal composite plate is prepared. Compared with the braze welding in a furnace, the method has the advantages of high efficiency, energy conservation, pressure lead-in, unnecessary soldering flux and gas protection and short holding time at a high temperature.

The method of electron beam brazing repair high temperature alloy blades. The invention involves a brazing repair high temperature alloy blade method in order to solve the problems of complex repair art, long repair cycle, the need of integral heating when brazing repair, long retention period at high temperature when brazing work in original method of repair high temperature alloy blade. The method is realized by the following steps: (1) grinding off blade injury and polishing the injury part into trough, mixing the solder or alloy powder and acetone or general soldering bonding agent sold in market into cream status and putting it in groove; (2) setting process parameters and brazing; (3) when the solder or alloy powder are not melted completely, cooling it until room temperature and taking out high temperature alloy blade, the high temperature alloy blade is repaired. The electron beam brazing repair high temperature alloy blade method in the invention has simple repair process and short repair cycle, a cycle requires only 5 minutes to 10 minutes, it only heats the injury position, the retention time of blades when repaired is reduced to 0.1 ~ 10% of original method.

The invention discloses a heat treatment method for improving mechanical property of a normalized steel plate, which belongs to the medium and thick steel plate manufacturing technical field. A rolled microalloying steel plate containing niobium is placed into a quenching furnace for conventional normalizing treatment, and is taken out of the furnace after 3 to 40 minutes of heat insulation, the quenching furnace is adopted to perform weak water-cooling treatment to the steel plate, the ratio of water supply and drain at a water outlet of a quenching machine is controlled to between 1 and 1.8, the roll speed is maintained to between 10 and 40m / min, and the measured surface temperature of the steel plate after the weak water-cooling treatment is between 600 and 800 DEG C. The method greatly improves the comprehensive performance of the steel plate compared with the conventional normalizing treatment: the yield strength is improved by between 50 and 80MPa, the tensile strength is improved by between 20 and 30MPa, the low-temperature toughness and the strain aging performance of the steel plate are both improved, the uniformity of the performance in the thickness direction of the steel plate is improved, and the plate shape and the surface quality of the steel plate are good.

The invention provides a method for making an easy-to-pickle steel plate and belongs to the technical field of metallurgy. The method comprises the following steps of: smelting molten steel, and making a plate blank by continuous casting; descaling by using high pressure water, performing rough rolling on the descaled plate blank, performing finish rolling, cooling to the temperature of 500 to 550 DEG C, cooling at the speed of 5 to 10 DEG C per minute to obtain the steel which is easy to pickle and in a hot rolling state and of which the content of FeO is over 25 percent; performing finish rolling, cooling to the temperature of 650 to 700 DEG C at the speed of 1 to 5 DEG C per minute to obtain the steel which is easy to pickle and in a cold rolling state and has a uniform structure and of which the content of iron oxide scale FeO is less than 10 percent. By adopting the method, the thickness of the iron oxide scale is reduced by 20 to 30 percent compared with the conventional process, the pickling speed of the strip steel is increased from 150 to 160 m per minute to 180 to 200 m per minute compared with the conventional process, not only the pickling quality of the steel plate is guaranteed, but also the pickling efficiency is effectively improved.

The invention relates to a method for preparing hydroxypivalaldehyde through a micro-channel reactor. The problems that in the prior art, reaction time is long, product selectivity is poor, and the raw material conversion rate is low are mainly solved. By means of the method for preparing hydroxypivalaldehyde through the micro-channel reactor, isobutyraldehyde, formaldehyde raw materials and a catalyst are mixed completely through a pre-mixer of the micro-channel reactor and then enter a constant-temperature reactor of the micro-channel reactor to react, and the product containing hydroxypivalaldehyde is obtained; the mass ratio of formaldehyde to isobutyraldehyde in the raw materials is (1-1.4) : 1; the using quantity of the catalyst is 0.5-5% of the total mass of a reaction solution; reaction temperature in the micro-channelconstant-temperature reactor is 100-140 DEG C, the pressure of a reaction meter is 0.5-1.5 MPa, and the reaction staying time of the reaction solution in the micro-channel reactor is 30-300 s; the technical scheme that after reaction, the conversation rate of the raw material isobutyraldehyde in the reaction solution after reaction is larger than 95%, the selectivity of the product hydroxypivalaldehyde is larger than 95% well solves the problems, and the method can be used for preparing hydroxypivalaldehyde.

The present invention discloses an ordered carbon nano-tube reinforced aluminum matrix composite material and a preparation method thereof. The composite material comprises aluminum or an alloy thereof adopted as a matrix material and carbon nano-tubes orderedly dispersed in the matrix material. The method comprises: carrying out cross-lamination on plural ordered carbon nano-tube thin film layers and plural aluminum layers or aluminum alloy layers, and carrying out hot rolling to form the ordered carbon nano-tube reinforced aluminum matrix composite material, wherein the ordered carbon nano-tube thin film layer is formed by the plural orderly-dispersed carbon nano-tubes. According to the present invention, the ordered carbon nano-tube thin film such as the superaligned nano-tube thin film and the like is adopted to carry out lamination and hot rolling with the aluminum foil to prepare the composite material so as to achieve orientation distribution of the carbon nano-tubes in the aluminum matrix, completely provide excellent mechanical property and functional characteristics of the carbon nano-tubes, achieve mechanical enhancement and function modification on the aluminum matrix composite material, combine with the hot rolling molding, and provide important practical application prospects.

The invention aims at solving defects such as low light oil yield, high foam layer, and high coke yield of prior arts, and discloses a delayed coking method. The method is characterized in that: a mixed raw material is heated in a heating furnace; the heated hot material flow enters a primary hydrocyclone, such that a gas phase (1) and a mixed liquid phase (1) are obtained; the gas phase (1) is quenched and is delivered into a fractionation column; high-temperature steam is injected into the mixed liquid phase (1), and the mixture is delivered into a secondary hydrocyclone; the secondary hydrocyclone separates the mixed liquid phase (1) into a gas phase (2) and a mixed liquid phase (2). The gas phase (2) is delivered into a fractionation column; high-temperature steam is injected into the mixed liquid phase (2), and the mixture is delivered into a coke column; coke is discharged from the bottom of the coke column, and reaction oil gas is delivered into the fractionation column.

The invention discloses a diazotization continuous tubular reactor which comprises liquid storage tanks, a tubular reactor, a diazotization salt separation storage tank and a circular cooling system, wherein all liquid storage tanks are connected with the tubular reactor through a mixer which can be used for sufficiently mixing all reaction materials and feeding the mixture into the tubular reactor; a flow controller is arranged between each liquid storage tank and the mixer; the mixer and the tubular reactor are in sealed connection; the circular cooling system comprises a quencher, a mediumstorage tank, a quencher nozzle and a recycling mechanism, wherein the quencher is used for connecting the outlet of the tubular reactor with the liquid inlet tube of the diazotization salt separation storage tank; the medium storage tank is used for storing a cooling medium; the quencher nozzle is used for quickly spraying the cooling medium into the quencher; the recycling mechanism is connected with the diazotization salt separation storage tank and used for recycling the cooling medium and cooling the recycled cooling medium; the recycling mechanism and the medium storage tank are connected; the cooling medium is low-temperature high-pressure CO2; and the top of the diazotization salt separation storage tank is provided with an exhaust port. The diazotization continuous tubular reactor disclosed by the invention has the advantages of high reaction yield, low energy consumption and strong generality.

A technology for welding high-C steel rail and high-Mn steel switch fork of railway includes such steps as build-up welding of Cr-Ni-Mo alloy transition layer on the steel rail, build-up welding of Mn-Cr-Ni alloy transition layer on the switch fork and solid dissolving, matching their U-shaped bevel joint surfaces, and manual arc welding. Its advantages are high welding quality and stability and low cost.

The invention provides an inner water circulation copper block forced cooling device for steel structure box-type column electroslag welding. The device comprises two water collection tanks, a water pump, a water valve, a water pressure gauge, a water pipe, a copper block and a U-shaped pipeline. The copper block is tightly attached to the outer surface of an electroslag welding member joint; two drainage channels are formed inside the copper block along the thickness direction; and a water inlet channel is formed close to the electroslag welding member side, and a water outlet channel is formed on the other side. The water inlet channel and the water outlet channel are communicated at one end of the copper block by virtue of the U-shaped pipeline; the water inlet channel at the other end of the copper block is connected with the water collection tank I; the water outlet channel is connected with the water collection tank II; inner water circulation of the copper block is realized under the action of the water pump, and forced cooling in the electroslag welding is realized. According to the device, a too wide heat affected zone, extremely long time Deltat 8 / 5 and high-temperature retention time generated by the electroslag welding joint can be avoided, so that the mechanical property, particularly breaking tenacity, of the electroslag welding joint is improved, the device can be used for improving the microstructure and mechanical property of the building steel structure box-type column electroslag welding joint, and the shock resistance of the structure is improved.

The invention belongs to the technical field of macromolecules, and particularly discloses hydrophilic polyester and a preparation method thereof. The hydrophilic polyester is prepared by polymerizingethylene glycol terephthalate oligomer and polyether glycol under the synergistic action of titanium alcohol salt, polyhydroxy compound, phosphorus compound, sterically hindered phenol compound and acetate. The hydrophilic polyester has the characteristics that the catalyzing function of titanium alcohol salt to side reaction is inhibited by the multiple stabilizer system; the easiness in yellowing is avoided, and the reduction of intrinsic viscosity in the forming process is little; the green and environment-friendly effects are realized, any heavy metal pollution is avoided, the color phaseis excellent, and the spinnability and heat stability are good.

The invention relates to an automatic welding and cooling device and welding method, and belongs to a welding device and a welding method. The technical problems that when pipes are welded, heat radiation performance is poor, and thin and small pipes cannot be welded are mainly solved. According to the technical scheme, the device and method are characterized in that a telescopic air cylinder (5) is arranged in an air cylinder sleeve (6), a cooling chamber (2) is arranged at one end of the telescopic air cylinder (5), a cooling pipe (1) is arranged at the other end of the cooling chamber (2), a water outlet (3) is connected into one side of the cooling chamber (2), and a water inlet (4) is connected into the other side of the cooling chamber (2). The device and method are mainly used for welding and cooling the small pipes or the thin-wall pipes.

The invention belongs to the technical field of textile fibers, and particularly relates to a hydrophilic polyester fiber and a preparation method thereof, wherein the hydrophilic polyester fiber is obtained by carrying out melt spinning on a hydrophilic polyester, and the hydrophilic polyester is obtained by polymerizing a ethylene glycol terephthalate oligomer and polyether diol under the actionof a titanium metal alkoxide, a polyhydroxy compound and a phosphorus compound / hindered phenol compound / acetate complex. According to the present invention, the hydrophilic polyester fiber has characteristics of yellowing resistance, reduced viscosity reduction during molding processing, good moisture absorption performance, good normal pressure dyeing performance, no heavy metal pollution, softhand feeling and excellent hue.

The invention discloses a multi-point synchronous hot-torsion forming device and forming method for a hollow blade. The multi-point synchronous hot-torsion forming device comprises a blade tenon clamping device, a multi-point pushing rod punch device and a heating device. According to the multi-point synchronous hot-torsion forming device and forming method for the hollow blade, precise control over torsional deformation of a blade body can be achieved through multi-point synchronous loading heat torsion, and meanwhile the mold manufacturing cost can be greatly reduced by applying a flexible tool composed of height-adjustable basic bodies which are arranged in a dot-matrix mode.

The invention discloses a laser welding method for a steel / aluminum dissimilar material. According to the laser welding method, an Al2O3 oxidation layer on the surface of an aluminum alloy does not need to be removed, and a Ni / B powder mixture is prearranged on the surface of the aluminum alloy, wherein the mass percentage of B powder ranges from 5% to 15%; laser welding is conducted in the atmosphere of inert gas mixed with a CO2 / O2 gas mixture or air, so that the metallurgical reaction in a molten pool is improved through Ni in the Ni / B powder mixture, occurrence of the Fe-Al metallurgical reaction is effectively hindered, and a Fe-Al intermetallic compound at an interface of a welding joint is inhibited from being separated; the B powder is molten and enters the welding molten pool, sothat toughness of an Al-Ni intermetallic compound generated after the Ni is added is improved; either or both of O2 or CO2 are adopted to be mixed with the inert gas, or welding is conducted directlyin a pure air environment, so that the oxygen partial pressure of the welding molten pool is increased, and an element Al and an element O entering the molten pool are combined to form Al2O3 which does not affect the toughness of the welding joint; the thickness of the Fe-Al intermetallic compound at the interface is reduced, and strengthening and toughening of the steel / aluminum dissimilar welding joint are achieved; and the high-quality laser welding joint is obtained.

The invention discloses a method for manufacturing a ventilated steel tube made of hull steel, which comprises the following steps: cutting into strips, i.e. vertically cutting a steel plate; milling edges, i.e. milling the two side edges of the steel plate at a time; prebending, i.e. removing straight flanges of the end of the plate; bending, i.e. primarily bending the steel plate into a cylinder shape; molding, i.e. molding the cylinder-shaped steel plate into the steel tube; closing a joint and prewelding, i.e. carrying out joint close on the connecting end of the steel tube; internal welding, i.e. welding the inner part of the connecting end of the steel tube; external welding, i.e. welding the external part of the connecting end of the steel tube; machining a tube end, i.e. machining a flat end of the tube end of the steel tube; straightening, wherein straightness accuracy being up to standard can be reached only through straightening; finishing, i.e. forcibly finishing through an O-shaped mould; trimming an end, i.e. enabling the end of the steel tube to be smooth; final detecting, i.e. detecting the steel tube; and warehousing, i.e. warehousing after the steel tube is detected to be qualified. A measure for preventing the occurrence of longitudinal cracks of a welding seam is controlling circular degree of prebending and prefinishing before internal welding.

The invention provides a heat treatment process capable of lowering ductile-brittle transition temperature and intergranular fracture ratio of turbine blades. When the heat treatment process is used, the problem that the process effect is susceptible to influences of chemical components of the raw material of the blades when the conventional sub-temperature annealing process is used to treat the turbine blades and the problem of high ductile-brittle transition temperature and intergranular fracture ratio of the turbine blades due to overlong high-temperature retention during heat treatment ofthe blades in the sub-temperature annealing process are solved. In the invention, the blades are uniformly placed in a common quenching material basket according to a technical scheme and then the quenching material basket is placed in a heat treatment quenching furnace. The heat treatment process is characterized in that: the blades are quenched twice in a quenching furnace; the temperature of primary quenching is 980 to 1070 DEG C; the temperature is kept constant for 1 to 3 hours; the cooling speed is 20 to 50 DEG C per minute; the temperature of secondary quenching is 900 to 1,000 DEG C; the temperature is kept constant for 15 to 120 minutes; the cooling speed is 30 to 50 DEG C minutes; and the temperature of the primary quenching is 20 to 100 DEG C higher than the temperature of the secondary quenching.

The invention provides a welding method for low-carbon high-strength steel. The welding method for the low-carbon high-strength steel comprises the following steps of: 1) forming a welding groove on the low-carbon high-strength steel with a laser blanking method, and forming a welding line between the welding grooves of two pieces of low-carbon high-strength steel to be welded; and 2) welding the welding line by consumable electrode mixed gas metal arc welding, filling a welding wire in the welding process, and ensuring that the welding environment temperature is higher than 5DEG C. Specifically, the step 2) comprises the following steps of: 21) carrying out backing weld to the welding line by non-pulse consumable electrode mixed gas metal arc welding, forming a backing weld layer on the bottom of the welding line, and filling the welding wire in the welding process; and 22) carrying out cosmetic welding to the welding line by pulse consumable electrode mixed gas metal arc welding, forming a plurality of cosmetic layers above the backing weld layer, ensuring that two adjacent cosmetic layers are provided with overlay regions, and filling welding wire in the welding process. According to the welding method for the low-carbon high-strength steel, the stress concentration is lowered, and the welding quality of the low-carbon high-strength steel is improved.

The invention discloses a rotary kiln for calcining titanium dioxide by a sulfuric acid method. The rotary kiln comprises a barrel body, a combustion chamber and a kiln tail cover, wherein the middle barrel body is supported by three groups of supporting wheels; the two ends of the barrel body are sealed with sealing fins; the sealing fins are arranged in a fish-scale shape; the gradient of the barrel body is 6-8%; an inverted horn mouth is arranged in a position of the barrel body with a distance of 3.5-5.5 m from a discharge hole; the inverted horn mouth comprises a shrinkage hole (2), a tube section (3) and an expansion hole (4); and raising plates (1) are arranged in front of the shrinkage hole and uniformly distributed in the axial direction of the barrel body. The rotary kiln has the advantages of high production capacity, low energy consumption and stable quality of calcined titanium dioxide.

The invention discloses a method for manufacturing a high-temperature and high-pressure steel pipe, which comprises the following steps: strip opening; edge milling; pre-bending, which eliminates the straight edge of the plate end; bending; forming; The end of the steel pipe is welded; the internal welding is used to weld the inside of the connecting end of the steel pipe; the external welding is used to weld the outside of the connecting end of the steel pipe; the pipe end processing is to process the flat end of the steel pipe end; straightening requires The straightness allowed by the standard can only be achieved after straightening; finishing, forced precise shaping with an O-shaped mold; flaw detection; heat treatment of the whole steel pipe after passing the flaw detection; re-straightening and finishing; trimming, so that the end of the steel pipe is smooth; finally Testing, testing the steel pipes; warehousing, the steel pipes are put into storage after passing the test. The main technical measures of the present invention to prevent quenching in the heat-affected zone are to use small welding energy, reduce the high-temperature residence time, and perform heat treatment after welding, thereby greatly reducing and eliminating the possibility of welding cracks.

The invention relates to an on-line process for improving performance of a welding heat affected zone. According to the technical scheme, the process comprises the following steps of: blowing compressed gas at a welding joint which is 20 to 50mm away from a welding arc along with the forward movement of the welding arc in the welding process of steel for 2 to 10 seconds; immediately covering the welding joint by using heat preservation cotton along with the departure of the compressed gas and slowly cooling to room temperature; and continuously performing welding, blowing and slow cooling processes respectively until the entire welding joint is cooled to the room temperature, wherein the compressed gas is air, the pressure of the compressed gas is between 0.5 and 1.0MPa, and the flow rate of the compressed gas is between 5 and 10L / min; and the welding joint is one of welding joints which are formed by a manual arc welding method, a submerged arc welding method, a gas shielded welding method and a tungsten electrode argon arc welding method. The on-line process has the characteristics of simple process, convenience of operation, no need of arranging special equipment and low cost; and by the process, cracks of the welding heat affected zone can be reduced or eliminated, and the performance of the welding heat affected zone can be obviously improved.

The invention discloses a tailored blank laser welding method for titanium micro-alloying carbon manganese steel. Laser is utilized to weld welding positions of titanium micro-alloying carbon manganese steel plates in air or in shielding gas which is a mixture of inert gas and oxygen gas. Weld zones obtained through the tailored blank laser welding method contain titanium elements obtained by melting base metal, titanium elements are oxidized and bonded with oxygen element provided by oxygen in shielding gas or air, formed titanium-containing oxides in proper size can just become nucleation points of acicular ferrite, full penetration welds of a mixed structure of acicular ferrite and martensite are obtained finally, and the welds have higher toughness than welds of a pure martensite structure obtained from pure inert gas. Compared with a method using pure inert gas rather than inert gas and oxygen mixed shielding gas or air, the method has the advantages that usage of inert gas is lowered, welding cost is reduced, and laser welding in air is unrestricted by welding surroundings.

The invention discloses a cooling device and method for butting welding of coiled tubing. The cooling device systematically comprises cooling blocks, a water pump, a flow regulation device, a temperature measuring and controlling device, a connecting pipeline, a backwater supplying device and the like. During work, the copper cooling blocks which are matched with a to-be-welded coiled tubing are selected and mounted according to the outer diameter of the to-be-welded coiled tubing; and the connecting pipeline and a circuit are used for reducing heat effect of welding heat on a welded seam area when coiled tubing is welded, and the cooling speed of a connector and a welding heat effect area is increased, so that the width of the welding heat effect area is reduced, high-temperature dwell time is reduced, the grain growth tendency is slowed down, and the welding joint performance is improved.

The invention discloses a diazotization continuous tubular reactor which comprises liquid storage tanks, a tubular reactor, a diazotization salt separation storage tank and a circular cooling system, wherein all liquid storage tanks are connected with the tubular reactor through a mixer which can be used for sufficiently mixing all reaction materials and feeding the mixture into the tubular reactor; a flow controller is arranged between each liquid storage tank and the mixer; the mixer and the tubular reactor are in sealed connection; the circular cooling system comprises a quencher, a mediumstorage tank, a quencher nozzle and a recycling mechanism, wherein the quencher is used for connecting the outlet of the tubular reactor with the liquid inlet tube of the diazotization salt separation storage tank; the medium storage tank is used for storing a cooling medium; the quencher nozzle is used for quickly spraying the cooling medium into the quencher; the recycling mechanism is connected with the diazotization salt separation storage tank and used for recycling the cooling medium and cooling the recycled cooling medium; the recycling mechanism and the medium storage tank are connected; the cooling medium is low-temperature high-pressure CO2; and the top of the diazotization salt separation storage tank is provided with an exhaust port. The diazotization continuous tubular reactor disclosed by the invention has the advantages of high reaction yield, low energy consumption and strong generality.

The invention provides a circular seam lock bottom connector and a manufacturing and welding method thereof. The method mainly comprises the steps of connector design, part preparing, welding preparing, assembling and spot welding, and formal welding. The connector design mainly focuses on the problem that due to the non-penetration state of laser welding of the lock bottom connector, air holes are formed easily, a groove is designed in a lock bottom part, the groove achieves the penetration state of laser welding on the structure, and the problem of the air holes can be solved. In order to relieve the situation that due to the groove, when gas in a closed cavity is heated and swelled in the welding process, small holes of laser welding and a molten bath are disturbed, and the welding stability is influenced, a ditch is designed in the lock bottom part, the ditch can communicate with the closed cavity and the outside, when heated swelling and cooling shrinkage occur in the laser welding process, the gas in the cavity breathes freely and circulates with the outside, the gas pressure in the cavity is stable, and thus disturbance on the molten bath for the laser welding and the smallholes is avoided.

The invention relates to an online process for improving the impact toughness of a welding heat affected zone. The online process adopts the technical scheme that the compressed gas is directly blown at the position of a welding joint which is 20-1200 mm away from a welding electric arc in the welding process of a steel product; the blowing time is 2-120 s; and the distance between the position of the blown welding joint and the welding electric arc is kept unchanged and synchronously moves forwards along with the welding electric arc. The compressed gas is air, the pressure of the compressedgas is 0.5-3.0 MPa; the flow rate of the compressed gas is 5-30 L / min; the steel product is one of low carbon steel, medium carbon steel, low alloy steel, medium alloy steel and high alloy steel; andthe welding joint is one of welding points formed by welding methods of electric arc welding, submerged-arc welding, gas shielded welding and argon tungsten-arc welding. The online process has the characteristics that the online process is simple, is convenient to operate, has low cost and requires no additionally-arranged special equipment. With the adoption of the process, the impact toughness of the welding heat affected zone can be improved by 60-525 percent.

The invention discloses a resistance spot welding method for a coated steel plate, and is applied to welding of a resistance spot welding device on a welding plate group. The method comprises the following steps that first-section welding is conducted on the welding plate group by adopting a first current to form a welding nugget with an initial diameter on the welding plate group, the first current being smaller than a maximum welding current; and after first interval time, a second current is adopted for conducting second-section welding with a duration being preset time on the welding plate group, so that a diameter of the welding nugget is increased to a target diameter, the target diameter being smaller than a maximum nugget diameter, the preset time being welding time required when welding is conducted by using the maximum welding current so as to enable the formed nugget to reach the target diameter, and the second current being smaller than the maximum welding current. According to the method, a welding process has a lower welding temperature and shorter high-temperature retention time, and the technical problems that in the prior art, the service life of an electrode is short, and LME cracks exist on the surface of a welding spot of the coated steel plate are solved.

The invention discloses a manufacturing method of a steel longitudinal submerged arc welding steel pipe for a high-temperature and high-pressure boiler. The method comprises the following steps of: splitting: vertically cutting a steel plate; edge milling: performing primary milling processing on two side edges of the steel plate; pre-bending to eliminate straight edges at plate ends; bending: initially bending the steel plate into a cylindrical steel plate; forming: forming the cylindrical steel plate into a steel pipe; joint close and pre-welding: performing joint close at the connecting end of the steel pipe; inner welding: welding the inside of the connecting end of the steel pipe; outer welding: welding the outside of the connecting end of the steel pipe; pipe end machining: machining a pipe end flat head of the steel pipe; straightening to reach standard-allowed straightness; finishing: forcedly finishing with an O-shaped mold; end trimming: smoothing the tip of the steel pipe; final detection: detecting the steel pipe; and warehousing: warehousing qualified steel pipes. In the invention, a measure for preventing a longitudinal crack of a welding line comprises controlling the pre-bending roundness and performing pre-finishing in advance before inner welding.

The invention discloses a heat treatment method for improving mechanical property of a normalized steel plate, which belongs to the medium and thick steel plate manufacturing technical field. A rolled microalloying steel plate containing niobium is placed into a quenching furnace for conventional normalizing treatment, and is taken out of the furnace after 3 to 40 minutes of heat insulation, the quenching furnace is adopted to perform weak water-cooling treatment to the steel plate, the ratio of water supply and drain at a water outlet of a quenching machine is controlled to between 1 and 1.8, the roll speed is maintained to between 10 and 40m / min, and the measured surface temperature of the steel plate after the weak water-cooling treatment is between 600 and 800 DEG C. The method greatly improves the comprehensive performance of the steel plate compared with the conventional normalizing treatment: the yield strength is improved by between 50 and 80MPa, the tensile strength is improved by between 20 and 30MPa, the low-temperature toughness and the strain aging performance of the steel plate are both improved, the uniformity of the performance in the thickness direction of the steel plate is improved, and the plate shape and the surface quality of the steel plate are good.

The invention discloses a preparation method of polyester, and the polyester. The preparation method comprises the following steps: (1) carrying out an esterification reaction on aromatic dibasic acid, aliphatic dihydric alcohol, a titanium catalyst and a carbon free radical scavenger to obtain an oligomer; (2) carrying out condensation polymerization on the oligomer to obtain a melt; and (3) curing the melt to obtain the polyester. The carbon free radical scavenger can efficiently capture carbon free radicals formed by the low-melting-point polyester in a high-temperature heated environment,so the thermal stability of the low-melting-point polyester is remarkably improved.