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This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard replaces GB/T 12362-2003 “Steel Die Forgings-Tolerance and machining allowances”. Compared with GB/T 12362-2003, except for editorial changes, the main changes are as follows:
- Replace the “Machine Machining Margin and Its Usage Principle” in the scope with “Machine Machining Remaining Level and Technical Content”, and change the “Structured Steel Forgings” to “Structural Steel Die Forgings” and replace “250kg” with “500kg”. (See Chapter 1, Chapter 1 of the 2003 Edition.)
- Remove "forgings that required additional manufacturing processes to be achieved" and "flat forged parts used only at ordinary level" (see 2.1 in 2003)
In the special case a) of 3.1.2, “In selecting tolerances, the mass of the forging is considered only the mass of the cylindrical part of diameter d and thickness t; if this special rule selects a tolerance less than that of 3.1.2 Tolerances selected by the rules are selected according to the general rules of 3.1.2” is added (see 3.1.2).
In the special case b) of 3.1.2, the “Where selecting the dimensional tolerances of the relevant features, the quality of the forgings only considers the mass of the cylinder with a diameter of d1 and a thickness of t1; if the tolerances chosen for this special rule are less than .2 Tolerances for general rules are based on the tolerances selected in 3.1.2 General rules (see 3.1.2) is added;
Remove “Where using coal-fired or secondary-fired heating, consider increasing the tolerance or margin appropriately, the value of which shall be determined through negotiation between the supply and demand sides” (see 3.1.6 of the 2003 edition).
Change "error tolerance" to "error" (see 3.2.4, 2003 version 3.2.4)
Change "deep tolerance" to "depth" (see 3.2.14, 2003 version 3.2.14)
The quality ranges in Table 1, Table 2, Table 3, Table 4, and Table 16 are revised and the query lines are added (see Table 1, Table 2, Table 3, Table 4, Table 16, Table 1, Table 2 of 2003 Edition), Table 3, Table 4, Table 16)
The aperture range in Table 15 is modified and the query line was added (see Table 15, Table 15 of the 2003 Edition).
This standard was proposed and is under the jurisdiction of the National Forging Standardization Technical Committee (SAC/TC74).
The previous versions of the standards replaced by this standard are:
- GB/T 12362-1990, GB/T 12362-2003.
Steel Die Forgings-Tolerance and Machining Allowance
1 Scope
This standard specifies the steel die forgings (hereinafter referred to as "forgings") tolerances and machining allowance levels and technical content.
This standard applies to die forging hammers, hot die forging presses, screw presses, flat forging machines and other forging equipment production of structural steel die forgings.
Other steel forgings can also be used as reference. This standard applies to forgings with a mass less than or equal to 500kg and a length (maximum size) less than or equal to 2500mm.
2 Level of Tolerances and Machining Allowances
2.1 The tolerance is divided into two levels: ordinary level and precision level.
Ordinary tolerances apply to forgings that meet the technical requirements of general die forging processes.
Precision tolerances apply to forgings with higher technical requirements and can be used for the full size of a forging and for local dimensions.
2.2 The Machining Allowance is Only One Level.
3 Technical Content
3.1 The main factors to determine forging tolerance and machining allowance
3.1.1 Forging Mass mf
Forging quality are estimated according to the following procedure:
The basic dimensions of the part drawing → Estimate the machining allowance → Draw the forging drawing → Estimate the forging quality, and determine the tolerance and machining allowance according to this quality check table.
3.1.2 Forging Shape Complex Factor S
The forging complex shape factor is the ratio of the forging mass mf to the corresponding forging external shell mass mN, see Equation (1):
S=mf/mN (1)
The forging profile containment mass mN is the calculated mass of the cylinder or cuboid containing the largest profile of the forging as the entity, and is calculated according to formula (2) or formula (3):
a) Round forgings (Figure 1)
mN=1/4·π·d2·h·ρ (2)
Where:
ρ——Steel density(7.85g/cm3)
Figure 1 Round Forgings
b) Non-circular forgings (Figure 2)
mN=l·b·h·ρ (3)
Figure 2 Non-circular Forgings
According to the size of S value, forging complex shape factor is divided into 4 levels:
S1 level (simple): 0.63
Foreword i
1 Scope
2 Level of Tolerances and Machining Allowances
3 Technical Content
Annex A (Informative) Forging Tolerance Application Example
