1、DEUTSCHE NORMEN Februapr 19 UDC 621.73.042-422.2-034-14 : 621.753.1 Steel Forgings Machining Allowances and Permissible Variations for Open-die Forged Bars DIN 7527 Part 6 Schmiedestcke aus Stahl; Bearbeitungszugaben und zulssige Abweichungen fr freiformgeschmiedete Stabe Dimensions in mm I. ScoDe T
2、his Standard applies to open-die forged bars which have had their final shape imparted to them by hammers or presses. It applies to round, square, hexagonal and octagonal bars, as well as to flat bars of high-grade steel including tool steel and high speed steel with a width-to-thickness ratio small
3、er than or equal to 8 : I, and also to flat bars of ordinary low carbon steel and quality steel having a width-to-thickness ratio smaller than or equal to 5 : 1. It applies to bars up to a maximum finished dimension of 1000 rnm in thickness or width and 6000 mm in length. 2. Dimensions and cross-sec
4、tional shapes 2.1. Dimensions The dimensions of open-die forged bars are thickness, width and length. In the case of round bar: the diameter counts as the thickness, whilst in the case of square, hexagonal and octagonal bars the thickness is taken as the distance between the parallel side faces. In
5、the case of flat bars the thickness is taken as the smaller distance and the width as the larger distance between the parallel side faces. - 2-=-cfoss_sectlonal- A B C D E Round bar Square bar Len they may be removed by suitable methods, provided that this does not impair the use of the bars. -=-Srf
6、ace_coobltio 5. Material and heat treatment The material is to be clearly specified by means of the material code number or the material number in accordance with the relevant material standards, and the type of heat treatment simi- larly according to DIN 17Cl4. 5. Methods of orderinq 5.1.1. Orders
7、based on finished dimensions For the thickness or thickness and width, the purchaser quotes the dimensions which the bar is required to have after final machining. From Table 1, the manufacturer determines the machining allowances, calculates the forging di- mensions (see Section 7) and, observing t
8、he permissible variations according to Table 1, sup- plies a bar which is thicker than the ordered size by the extent of the machining allowances. When bars are premachined prior to heat treatment, the premachining dimensions count as finished dimensions. 6.1.2. Orders based on forging dimensions Th
9、e purchaser quotes the forging dimensions calculated from the finished dimensions and the ma- chining allowances according to.Table l. The manufacturer, observing the permissible variations according to Table 1, supplies a bar with the dimensions stated in the order. For distinguishing from orders b
10、ased on finished dimensions, orders based on forging dimensions are to have the letter S (forging dimension) appended to the letters denoting the cross-section- al shape (A, B, C, D or E). If an order based on forging dimensions omits the letter S it will be treated in the same way as an order based
11、 on finished dimensions (see Section 6.l.Ij, and a bar will be supplied which, compared with the dimensions stated in the order, is thicker, or thicker and wider, by the extent of the machining allowances. 6.2.1. Orders based on finished dimensions The purchaser indicates the length of the bar after
12、 final machining. From Table 1, the manufacturer determines the machining allowances, calculates the forging di- mension (see Section 7) and, observing the permissible variations according to Table I, supplies a bar which is longer than the ordered dimensions by the extent of the machining allowance
13、s. If, for the purpose of joint ordering, the finished lengths of two or more bars plus allowances for the necessary number of parting cuts are combined to form a total length, this length is treated as a finished dimension. 6.2.2. Ordering in forging dimensions The purchaser states the forging dime
14、nsions calculated from the finished dimensions and the ma- chining allowances according to Table l. The manufacturer, observing the permissible variations according to Table I, supplies a bar of the length ordered. 6.2.3. Ordering in manufacturing lengths Instead of quoting a fiy for the length, the
15、 purctaser writes in the word “manufacturing lengths“ (Herstellngen or the abbreviation Hstlg. . The manufacturer, observing the permissible variations according to Table 1 on thickness or thickness and width, supplies bars to his own choice in lengths conforming to normal practice and ranging up to
16、 a maximum length of 6000 mm. 6.2.4. Ordering in a length range 6:2:_crosssec4iooal_da4a 6:2:-4!2?gth-b; 1 mm 2:-Fi_atda,r_E_65-5- Machining allowances and permissible variations on width f2 = 165 mm 21 and f 6.3mm on length 26 and ? :$ mm forging dimensions s2 = Calculation of the reference dimensi
17、on: -= 165 + 6o 112.5 mm Machining allowances and permissible variations according to the reference dimension 112.5 mm on thickness f3 = 60 nun 17 and 24.8 mm forging dimension 8. Examples o orders 8.1. Ordering thickness and length based on finished dimensions Ordering IO open-die forged round bars
18、 (A) or a finish machined thickness of 165 mm and a finish machined length of 2020 m in St 37-3: 10 bars A 165 x 2020 DIN 7527 - St 37-2 8.2. Ordering thickness based on finished dimensions and length in a particular length range Ordering 5 open-die forged square bars (B) or a finish machined thickn
19、ess of 260 mm in steel according to material No. 1.0727.02 in lengths of 4000 to 5000 mm: 5 bars B 260 x 4000 to 5000 DIN 7527 - 1.0727.02 Ordering 12 open-die forged round bars (A) according to forging dimensions (S) of 160 mm thick- ness and 320 mm length in C 45, soft annealed (G): 12 bars AS 160
20、 x 3200 DIN 7527 - C 45 G Ordering 8 open-die forged square bars (B) according to forging dimensions (S) of 180 mm thick- ness in steel according to material No. 1.0116, in manufacturing lengths: 8 bars BS 180 DIN 7527 - 1.0116 in manufacturing lengths lf = 4500 mm 165 + 21 = (186 5 6-3 ) mm 1, = 45
21、00 + 26 = (4526 2 $) mm 2 s3 = 60 + 17 = (77 t 4.8) .mm _- _- . _-_- . - - - s,7:-ol._erins-thicdoess_an_b_leoK4h_daseb-on_oorglng_b,meosioos s:_oerlne;-4aic-o-ro-eoso-leog4h_io-aooac4riog_leng4Ss Explanations This Standard is the outcome of discussions between manufacturers and users of open-die fo
22、rged bars. In response to wishes expressed by users, the scope of the Standard has been extended to include a maximum finished dimenaion of 1000 mm for the thickness of round, square, hexagonal and octagonal bars, and for the width of flat bars. Hitherto it has only been possible to order open-die f
23、orged bars on the basis of their finish machined di- mensions. This Standard provides a second method of ordering for use in cases when, for example, bars are to be ordered for stock and their finish machined dimensions are not known, or machining of the surface is not intended (e. g. bars for unfin
24、ished hexagon nuts). Whilst small machining allowances and small permissible variations involve smaller amounts of material usage, they demand in return increased cost on the forging side. In thie Standard the machining allowances and permissible variations have been chosen in such a way that the co
25、st of the finished part is near the economic optimum. Since the cost in terms of material usage depends on the quality of the steel grades con- cerned, these have been associated with different machining allowances and permissible variations. In conformity with the definition of machining allowances
26、 commonly accepted in practice as being allowances per area, the Figure showing the different cross-sectional shapes indicates the dimension letter changed from the former z/2 to z and, correspondingly in the Table, from z, as formerly, to 2 z- The previous indication of the cross-sectional shapes b
27、y letters A, B, C, D and E has been retained. The denomination of the steel groups in the Table has been brought into agreement with DIN 17007; the cor- responding ranges of material numbers have been quoted. The Table has been enlarged by including nominal dimension ranges for forging dimensions. In addition, par- ticulars regarding variations of shape and surface condition as well as a note on heat treatment have been included in the Standard. Page 4 DIN 7527 Part 6
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