液压外文翻译钢制夹紧液压缸支架 【中文2630字】【PDF+中文WORD】
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UDC 669.14.018.298:621.226STEEL FOR CRAMPS OF HYDRAULIC PRESS CRADLESI. A. Borisov1Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 24 26, May, 2001.INTRODUCTIONCreation of installations with a high unit power is ac-companied by growth of their sizes and the mass of the prin-cipal parts. This raises the requirements to the steels used forthe production of heavy-duty parts for such installations.In the present work we solved the problem of the choiceof steel for making large-size welded cradle cramps that arehighly loaded components of hydraulic presses and can de-velop, for example, a force of 650 MN.The design of a cradle includes twenty welded cramps.The length of each cramp is 30 m, the width is 1.5 4 m, andthe thickness is 0.28 0.32 m. A cramp weighs 160 tons. Itshould be noted that the maximum thickness of the sheetsused for fabricating such cramps is 0.36 m with the processallowance.Based on the data contained in native handbooks of steelgrades and special specifications 1 3 and the experienceof plants producing rolled sheets, we analyzed 10 carbon andlow-alloy steels, namely, 25, 30, 16GS, 20GS, 25GS, 09G2S,22K, 20Kh2MA, ITs-14, and 16GNMA. It turned out thatonly grades ITs-14 and 16GNMA of the list fully satisfy therequirements of the specifications. We did not know of anyexperience of their use for the production of parts with athickness of 0.36 m. Steel 30 used for plates up to 0.5 mthick was the only exception, since it met the requirements ofthe TU with respect to the level of mechanical properties.Steels ITs-14 and 16GNMA have a quite high adaptabi-lity to manufacture and are widely used in the industry forthe production of rolled sheets possessing a high strength andductility and a twice-higher impact toughness than is re-quired by the TU. The steels are satisfactorily weldable inlarge cross sections.Taking these properties into account we chose steel16GNMA used for fabricating boiler drums with high steamparameters as a prototype for our study.METHODS OF STUDYThe specified mechanical properties of cramp steelsare as follows: ?0.2? 225 MPa, ?r? 450 MPa, ? ? 18%,KCU ? 0.4 MJ?m2.The chemical composition of steel 16GNMA was cor-rected for the production of plates with respect to the mainalloying elements. In particular, the lower carbon limit waswidened by 0.1%, the content of manganese was diminishedby 0.1%, and modification with vanadium and titanium(0.05% Ti and 0.07% V) was undertaken in order to preservethe strength. These changes were directed at improving thefabricability of the steel and obtaining a steady level of itsmechanical properties. As a result, the steel has become po-pular in the production of power components of heavy hy-draulic presses under the name of ITs-1M.We also tried steel 30A as the simplest and economicallyexpedient variant (Table 1).The test steels were molten in 100-ton open-hearth fur-naces by the scrap process and cast into 68- and 82-tonmolds. The ingots were forged with and without preliminaryupsetting. The forged plates were subjected to a single an-nealing (with full recrystallization) at 860C (steel 30A) andMetal Science and Heat TreatmentVol. 43, Nos. 5 6, 20011990026-0673/01/0506-0199$25.00 2001 Plenum Publishing Corporation1TsNIITMASh Research and Production Association, Moscow,Russia.TABLE 1. Chemical Composition of the Studied SteelsSteelContent of alloying elements, %Content of admixtures, %CSiMnNiMoCrNiCuSPat most30A0.26 0.32 0.17 0.37 0.50 0.80200.020ITs-1M0.12 0.18 0.17 0.37 0.70 1.001.0 1.30.45 0.550.300.300.0200.020910C (steel ITs-1M) and to a single (steel 30A) or doubleannealing (steel ITs-1M) at 650C with subsequent coolingwith the furnace. Four forgings for pilot plates were pro-duced from each grade of steel. The ultrasonic check of theplates was performed with adjustment of the device for astandard opening 2 mm in diameter.Templates with a thickness of 200 mm were cut from theplates on the sides of the crop and the butt of the ingot aftercutting the recrement 200 400 mm wide. They were usedto study the macro- and microstructure of the metal of theforging, take sulfur imprints, and perform additional ultra-sonic check if necessary.The final heat treatment consisted of “soft” normaliza-tion and subsequent annealing. For this purpose preforms20 mmthick,200 mmwide,and380 mm high taken from the templateswere subjected to a final heat treat-ment by the following regime: 2-haustenization at 920C, cooling at arate of 150 K?h to 600C and then inair (imitation of the regime of norma-lization of plates), and annealing at650C for 10 h. The mechanical pro-perties were determined on transverseandlongitudinalspecimens.Thetransverse specimens were taken from the surface zones ofthe plates and at a depth of 1?3 and 1?2 of the thickness ofthe plate. The vertical specimens were taken from the surfaceand central (with respect to the thickness) zones of the plate.RESULTS AND DISCUSSIONThe study of the metal of the plates fabricated from steel30A showed that it fully meets the requirements of the speci-fications to the mechanical properties, the microstructure,and the sulfur content. For example, the level of the proper-ties of plates with a chemical composition including 0.32%C, 0.37% Si, 0.71% Mn, 0.25% Cr, 0.23% Ni, 0.15% Cu,0.017% S, and 0.008% P exceeded the specified values evenafter a preliminary heat treatment, namely, ?0.2= 240 MPa,?r= 460 MPa, ? = 33.6%, ? = 59%, and KCU = 1.0 MJ?m2.However, the ultrasonic control of all the pilot platesshowed that they possessed defective zones at a distance of130 150 mm from the surface, which stretched from thepadding to the butt of the plates. Therefore, three plates ofthe four ones subjected to this kind of check were rejected.Another four pilot plates were produced from steelITs-1M. The chemical composition of the pilot plates is pre-sented in Table 2; the method of casting and the mass of theingots and the forgings are presented in Table 3.The level of mechanical properties of the pilot plates af-ter the preliminary heat treatment and the points of the sulfurimprints are presented in Table 4.Analyzing the data of Tables 2 4 we can see that steelITs-1M meets the requirements of the specifications even inthe state of annealing, and its characteristics of ductility andimpact toughness are even much higher. The inconsiderabledifference in the properties of the metal of the four heats thatdiffer in the chemical compositions but correspond to thespecifications indicates that the specified composition ofsteel ITs-1M is balanced. The close levels of the metal takenfrom the crop and butt of an ingot show that the steel is appli-cable for large forgings due to its high fabricability.Control of the macrostructure showed the absence of de-fects. The points of the sulfur imprints in the crop and buttparts of the ingot satisfied the requirements of the specifica-tions (Table 4). Individual defects with the size of the stan-dard opening (? 2 mm) were detected by ultrasonic checkonly in the central part of a plate fabricated from heat 3 at a200I. A. BorisovTABLE 3. MassofIngotsandForgingsfromsteelITs-1MHeatCastingtechniqueMass, tonsingotforging1Degassed82.053.5268.036.63Not degassed68.036.6482.053.5TABLE 2. Chemical Composition of Steel ITS-1MHeatContent of alloying elements, %Content of admixtures, %CMnSiNiMoCrCuSP10.170.750.301.20.490.260.120.0160.00820.160.820.290.150.0180.01030.130.70170.00840.130.850.251.080.550.300.150.0180.008TABLE 4. Mechanical Properties and Points of Sulfur Imprintof Plates from Steel ITs-1 after Preliminary Heat TreatmentHeat?0.2,MPa?r,MPa?, %?, %KCU,MJ?m2Pointsof sulfurimprint1280300480480314306.710680.1312.212320330500480304300.730730.1716.213280300450455320308.650690.1514.214335325520510246300.460640.0809.21Notes. 1. The numerators present the properties determined forspecimens cut from the crops of the ingots; the denominators presentthe properties of specimens cut from their butts.2. The scale of points of the sulfur imprint consisted of four points(the fourth point corresponded to rejection).depth of 100 260 mm. The other three pilot plates had nodefects. This circumstance was decisive for choosing steelITs-1M for the production of commercial cramps for presscradles.In order to obtain an all-sided picture of the quality of themetal of the pilot plates we performed a laboratory study im-itating the regime of normalizing and annealing of actualplates. Templates subjected to such a treatment were used tocut transverse and longitudinal preforms for specimens formechanical tests. The preforms were cut in these directionsin order to estimate the suitability of steel ITs-1M for theproduction of thick sheets, because these directions are notonly the worst but the most indicative from the standpoint ofthe quality of the plate metal (Table 5).The performed study showed that the mechanical proper-ties of the pilot plates in the normalized and annealed statesexceeded the requirements of the specifications quite sub-stantially even in tests of the specimens cut in unfavorabledirections. It should be stressed that no deviation from the re-quirements was detected in the course of the tests, which is avery rare case for the metal of large preforms. The level ofthe mechanical properties was close over the thickness and invarious zones of the forgings, as well as in individualforgings. This means that the metal is highly isotropic andconfirms the correctness of the choice of the chemical com-position for steel ITs-1M and the production process for theplates.CONCLUSIONS1. We recommend steel ITs-1M of the following chemi-cal composition: 0.12 0.18% C, 0.17 0.37% Si, 0.7 1.0% Mn, 1.0 1.2% Ni, 0.45 0.55% Mo, ? 0.30% Cr,? 0.30% Cu, ? 0.020% S, ? 0.020% P for the production ofcradle cramps of high-capacity presses in the form of forgedand rolled plates.2. The mechanical properties of the plates after the pre-liminary heat treatment (?0.2= 280 335 MPa, ?r= 450 520 MPa, ? = 24.6 31.4%, KCU = 0.8 1.6 MJ?m2) andafterthefinalheattreatment(?0.2= 350 460 MPa,?r= 490 620 MPa,? = 22.3 32.7%,andKCU = 0.8 1.8 MJ?m2) substantially exceed the requirements of thespecifications(?0.2? 225 MPa,?r? 450 MPa,? ? 18%,KCU ? 0.4 MJ?m2).3. It has been shown that low-carbon compositions ofMn Ni Mo steels in the form of a thick forged and rolledplate are suitable for heavy-duty par
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