Analysis of crackle of forging of manhole of oilcan of large wall pressure reachs his to solder

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Summary: Take-over in the manhole of oilcan of large wall pressure when the assorted solder seam welding of forging and cylindrical shell receives repair, unusual arose to solder crackle, and take-over to manhole ceaselessly the phenomenon with patulous forging undertook an analysis, use electron microscope observation, undertake chemical composition analysis and mechanical function experiment, discover manhole take-overs forging tenacity difference, grain is bulky, use normalizing to add craft of temper heat treatment manhole of new heat treatment take-overs forging, can make forging function satisfies standard requirement afresh, by welder art the requirement applies solder manhole to take-over the assorted welding line of forging and cylindrical shell, flaw detection is eligible. Keyword: Pressure vessel; Canister forging; Crackle; Normalizing; Solder guides character pressure oilcan to belong to 2 kinds of pressure vessel, according to coming water quantity differs, its command point of view of lamina of the water turbogenerator in hydroelectric station, design actuating pressure 6.

3MPa, hydraulic proof pressure 8.

75MPa, design work temperature 50 ℃ , working medium is oil, welding line coefficient is 1, cubage 19.

78m3, cylindrical shell and seal a head to use data of 16MnR normalizing condition, armor plate chases flaw detection of ultrasonic of Zhang Jin travel, quality presses the Ⅲ class regulation of standard JB4730-94, a, B kind butt joint welding line undertakes flaw detection of 100% γ ray, press qualification of class of JB4730-94 standard Ⅱ , meet with every solder again after qualification of length 20% undertake ultrasonic detects, press qualification of class of JB4730-94 standard Ⅰ , manhole, flange, take-over to all use the forging of 16Mn Ⅲ class that accords with JB4726-2000 standard (normalizing) , d kind flaw detection of 100% magnetic particle should undertake after contact solder, press qualification of class of JB4730-94 standard Ⅰ , this equipment solders entirely end and nondestructive detects heat treatment of stress of disappear of whole of travel of the reentry after qualification. When hydraulic experiment, take-over in manhole the place of assorted welding line of forging and cylindrical shell produced crackle, when subsequently crackle repair, in discovering carbolic arc enrages dig process, crackle is met by solder inclined to expand ceaselessly in forging, plane of air of forging carbon arc blows off make an appointment with 600mm after deepness of long, 20mm, still produce crackle ceaselessly, some place did not discover flaw at that time, but produce crackle again subsequently, be forced to stop solder to meet repair. To analyse the account that this kind of phenomenon produces, the manhole that from repair generation crackle already discarded as useless take-overs on forging, sampling undertakes chemical composition analysis, mechanical function examines, observation of macroscopical and microcosmic metallographic, find out the account that produces a problem thereby, enact processing measure. 1 test data and method 1.

Material of section of canister of 1 test data is 16MnR, board thick 50mm; Manhole take-overs for 16Mn forging (the Ⅲ class of JB4726-2000 standard) , its dimension is φ 572/ φ 450 × 425 Mm, of forging of the chemical part that nominal and chemical composition and supplier provide data of 16MnR canister section, 16Mn nominal the chemical part that reachs a supplier to offer and composition of actual measurement chemistry see a table 1. The chemical composition that expresses 1 tube of sections and forging (Wt% ) 1.

Preparation of 2 test specimen and method take-over from the manhole that discard as useless press on forging tangential respectively intercept drawing sample, concussion sample, metallographic sample, the Xia Bichong that becomes a standard by GB/T229 metric system with machine treatment method attacks sample, the impact that has room temperature, 0 ℃ respectively experiments, have observation directly to pounding fracture surface; Drawing sample presses the R4 date in GB/T6397 (D0 = 10mm, l0 = 50mm) preparation, tensile test undertakes by GB/T228 standard; Metallographic sample preparation is grind on metallographic sand paper to 1800# , use 3 oxidation next 2 chromic aqueous solution are in P-2 polisher upcast is smooth, abluent hind corrode of dip of the acid that use heat, make its show the microstructure of sample. The observation of concussion fracture surface and metallographic sample scans in Quanta 400 electric lens (SEM) in undertake. Use deliquescent law to undertake chemical composition is analysed. 2 tests result and analysis 2.

Aperture of 1 newspaper disabled person take-overs forging 2.

1.

The mechanical function rank of forging of 1 mechanical function is expressed 2, criterion for evaluation is pressed " pressure vessel uses carbon steel and low-alloy steel forging " JB4726-2000[1] , by the watch 2 visible, the data that mechanical function and supplier provide the forging of actual measurement differs bigger, its intensity exceeds standard upper limit, concussion result is far the lowermost value that asks under the standard, present sex of excel in, small new moon, low tenacity. Watch 2 discard as useless the mechanical function of forging 2.

1.

After 2 metallographic organization and crackle analyse arc of carbon of this forging classics to enrage dig, the groove that enrages dig in carbolic arc is in origin to have macroscopical and visible flaw, crackle grows about 12 ㎜, meet by solder inclined to expand in forging, see graph 1a. The deep gray area near groove leaves in metallographic microscope, show below scanning report lens for white bright area, see graph 1b, the organization of deep gray area near groove is martensite + leftover austenite, hardness HV0.

1 500, 454, 438; With HV0 of hardness of area of adjacent of deep gray photograph.

1 331, 311, 323, its organization is ordinal for (graph 1C) ferrite of irregular lump of ferrite → of + of body of family name of all alone of → of body of family name of troostite → all alone + pearlite, . The organization that is far from crackle place is irregular lump ferrite + pearlite, see graph 1d. Observe sample polish face, decarbonization phenomenon is not had near crackle, without serious field trash. Via determining, manhole take-overs forging brilliant granuality is 4 ~ 5 class, bulkier, graph 1d also can prove this. (A) macroscopical metallographic; (B) crackle is initiative place feature; (C) be far from crackle area organization; (D) area of groove place deep gray organizes a scheme 1 manhole take-overs acetone of classics of fracture surface of forging crackle and concussion of microstructure manhole forging is supersonic after cleaning, visible section shows the cleavage trait that the graph shows 2 times. Cleavage unit is bigger, local 2 crackle are apparent, the unusual metallurgy flaw such as big field trash, loose, stoma did not discover on section. Graph appearance of form of fracture surface of concussion of 2 manhole forging take-overs as a result of manhole forging forgings bigger, wall is large, must the temperature with 1250 higher ℃ of 850 ℃ ~ forgings, here grain of temperature area 16Mn is brought up extremely easily bring about overheat [2] , take-over in manhole the assorted welding line of forging and cylindrical shell is tall cabined when soldering, when crackle of repair welding line, as a result of the existence of cementite layer and leftover austenite, composition slants analyse relatively serious, below the combined action of thermal stress and greater cabined stress, caused martensite photograph to change [3] , produced exterior crackle, as a result of outside the normalizing after bought forging forgings did not achieve a requirement, the overheat organization that makes high temperature forgings did not restore, forging grain is bulky, grain is bulky it is carbolic arc in air plane process, crackle is met by solder inclined to the main reason that expands ceaselessly in forging, manhole take-overs forging falls in the combined action of thermal stress and greater cabined stress, crackle is met very easily also by solder inclined to expand ceaselessly in forging, make forging crackle ceaseless thereby patulous and hard repair. 2.

2 times aperture of choose and employ persons take-overs mechanical function and metallographic organization use forging the manhole that discard as useless take-overs forging does imitate test, the method that uses new heat treatment makes forging is answered with. Take-over the manhole that discard as useless forging regards as the heat treatment that let oven tries board, take-over to unqualified manhole forging classics 620 ℃ of ~ of 930 ℃ normalizing, 600 ℃ answer 900 ℃ ~ after fervent processing [4] , try in the heat treatment that let oven board on by tangential respectively intercept drawing sample, concussion sample, metallographic sample, its are mechanical function rank is expressed 3, with the watch 2 in data phase is compared, 16Mn manhole take-overs the mechanical function of forging gets ameliorative apparently, satisfy standard requirement completely; Fire of classics of mother capable person adds the metallographic organization of temper to be ferrite + pearlite, brilliant granuality is 9.

5 ~ 10.

5 class, if the graph is shown 3 times, grain gets refining apparently. The overheat organization that makes through new heat treatment high temperature forgings apparently gets resumptive, improved metallographic organization, refined grain, obtain what contented standard asks to learn function index, satisfied use requirement, manhole take-overs forging classics normalizing adds temper can answer afresh after new heat treatment with. The watch pursues 3 times with the mechanical function of forging 3 manhole take-over 1003 manhole of × of the organization after forging normalizing take-over forging and canister section solder to take-over manhole forging classics normalizing adds temper after new heat treatment, solder with cylindrical shell again, because manhole take-overs of forging and cylindrical shell solder those who use two end to all be extended is embedded T Quan Rong solders fully contact, structural tigidity is bigger, solder cabined stress is greater [5] , must the warm-up before solder 150 ℃ of 100 ℃ ~ , the temperature between the layer not under 150 ℃ , after wall solders, have intermediate disappear hydrogen treatment, in order to make up for inadequacy of the temperature between the layer, after the wall solders outside, have final disappear hydrogen treatment again, the manhole that as above solders take-overs the assorted welding line of forging and cylindrical shell, level of grade of Ⅱ of JB4730-94 ultrasonic flaw detection is pressed after 24 hours, qualification. Graph 4 manhole take-over forging and canister section solder 4 conclusion 1) after because canister manhole take-overs,forging forgings press requirement normalizing not strictly, make manhole take-overs forging overheat organization did not restore, grain is bulky, bring about manhole to take-over the assorted welding line of forging and cylindrical shell is in thick board tall crackle of the generation when next cabined soldering. 2) use forging normalizing to add temper craft new heat treatment, can improve its metallographic completely to organize, refine grain, achieve the mechanical function target that the standard asks, also satisfied use requirement. 3) the manhole after new heat treatment take-overs the assorted welding line of forging and cylindrical shell, the welder of hydrogen treatment of the disappear after solder of the warm-up before using solder art measure, in thick board tall cabined solder below flawless generation, welding line flaw detection is one-time eligible. CNC Milling CNC Machining