A0802_A0802M-95(2006)钢铸件外观检验的表面验收标准

Designation: A 802/A 802M – 95 (Reapproved 2006) Standard Practice for Steel Castings, Surface Acceptance Standards, Visual Examination1 This standard is issued under the fixed designation A 802/A 802M; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon (e) indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. 1. Scope 1.1 This practice covers the acceptance criteria for the surface inspection of steel castings by visual examination. Four levels of acceptance standards are provided. 1.2 Acceptance levels utilize Steel Castings Research and Trade Association (SCRATA)2 graded reference comparators for the visual determination of surface texture, surface rough- ness, and surface discontinuities described as follows: Acceptance levels A—Surface Texture B—Nonmetallic Inclusions C—Gas Porosity D—Solidification Discontinuities E—Sand Expansion Discontinuities F—Metal Inserts G—Thermally Cut Surfaces H—Mechanically Prepared Surfaces J—Welded Surfaces 1.3 Descriptions of terms related to casting discontinuities are in Section 2. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety and health practices and determine the applica- bility of regulatory limitations prior to use. 2. Terminology 2.1 Definitions of Terms Specific to This Standard: 2.1.1 expansion discontinuities: 2.1.1.1 veins, n—raised, narrow, linear ridges that form upon cracking of the sand mold or core due to expansion of sand and the resulting mold or core stresses during filling of the mold with liquid steel. 2.1.1.2 rat tails, n—long, narrow, linear depressions or small steps occurring on a casting surface. Rat tails form as a result of sand expansion and minor buckling of the mold surface during filling of the mold with liquid metal. 2.1.1.3 scab, n—a raised, rough area on a casting that usually consists of a crust of metal covering a layer of sand. Sometimes, a scab consists of a raised, rough area of essen- tially solid metal on the surface of a casting. 2.1.2 external chills: 2.1.2.1 external chills, n—usually metal blocks, or graphite and carbon blocks, that are incorporated into the mold to locally increase the rate of heat removal during solidification. Brackets have the same purpose but represent an integral part of the casting. Brackets are produced by providing suitable cavities in the mold or core. External chills may produce flat spots and edges (raised areas or depressions) on the casting surface. Brackets merely change the casting appearance due to their presence. Brackets may be removed or allowed to remain on the casting. 2.1.2.2 parting line and core print fins, n—thin projections of excess metal at the parting plane between mold halves or core and mold. Causes are improper closing of the mold, insufficient weighting or clamping of the mold for pouring, or uneven pattern surfaces at the matching locations. Core print fins are usually caused by improper dimensions of core prints of the pattern or core box, by rough placement of cores in a soft mold, or by inadequately secured cores. 2.1.3 fusion discontinuities: 2.1.3.1 wrinkles, n—elongated, smooth depressions of the casting surface, frequently appearing in closely spaced groups. Wrinkles result from irregularities of the liquid metal flow in the mold cavity, frequently associated with low temperature, and are distinguished from the more severe phenomenon of laps, folds, or cold shuts where the casting surface is actually folded over. 1 This practice is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel, and Related Alloys and is the direct responsibility of Subcommittee A01.18 on Castings. Current edition approved March 1, 2006. Published April 2006. Originally approved in 1982. Last previous edition approved in 2001 as A 802/A 802M – 95 (2001). 2 Available from The Castings Development Centre, 7 East Bank Road, Sheffield, UK S2 3PT. 1 Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States. 2.1.3.2 laps, folds, and cold shuts, n—interchangeable terms to describe the appearance of the casting surface that is actually folded over. They develop due to low temperature, unfavorable flow conditions caused by oxide films, or combi- nations thereof. 2.1.3.3 misrun, n—an incompletely formed casting, due to only partial filling of the mold cavity when the liquid metal solidifies prematurely. The resulting casting appearance is characterized by rounded edges, for a mild degree of misrun. Irregular, malformed edges of more severe misruns, and not fully formed castings, are characteristic. Frequently, misruns are associated with such discontinuities as wrinkles or laps and folds, or both. 2.1.4 gas porosity, n—a concave discontinuity in castings due to the evolution of gas, either from the solidifying metal or the surrounding mold. 2.1.5 inserts: 2.1.5.1 chaplets, n—metallic (steel) devices used to main- tain the spacing between the core and the mold. Low liquid metal temperature and unfavorable flow conditions in the mold may produce insufficient fusion and cause irregular contact areas on the casting surface. 2.1.5.2 internal chills, n—metallic (steel) devices used to locally increase the rate of heat removal during solidification. Incomplete fusion due to low liquid steel temperatures and prevailing flow conditions may produce irregularities of the surface similar to those that may be associated with chaplets. 2.1.6 linear discontinuities, n—elongated discontinuities are considered linear if their length equals or exceeds three times the width. 2.1.6.1 cracks, n—cold and hot, less jagged, sometimes straight ruptures that occur after solidification of the casting, due to excessive strain. Sometimes cracks are referred to as cold, hot, or heat treat-cracks to indicate the condition of the castings, or the operation during which the cracks occur. 2.1.6.2 hot tears, n—jagged ruptures in castings that occur during the final stages of solidification, while there is still some liquid in the interdendritic spaces, or shortly after solidification is complete. 2.1.7 metal removal marks, n—flame cutting and air carbon- arc cutting produce parallel grooves in the cut-off area. Finer marks are produced with the abrasive cut-off wheel and grinding. 2.1.8 nonmetallic inclusions, n—casting surface inclusions such as ceroxides, slag, and sand are partially or completely removed during the cleaning process of pressure blasting. Surface discontinuities left by these inclusions are referred to by the inclusion type that caused their formation: 2.1.8.1 Ceroxides cause depressions on the surface of the casting by displacement of molten metal. Ceroxides consist of a mixture of low-melting oxides and partially fused sand. The crater-like appearance of the casting surface depression is typical. 2.1.8.2 Depressions on the casting surface caused by slag are similar to those caused by ceroxides. They differ by a more rounded appearance of the depression and do not exhibit the crater-like appearance of ceroxides. 2.1.8.3 Depressions caused by sand are similar to those of ceroxides and slag. Their appearance may, at times, more closely reflect the granular nature of the sand. 2.1.9 shrinkage under risers and gates, and revealed by machining, n—a shrinkage void is a discontinuity in castings due to the lack of available liquid feed metal during solidifi- cation contraction. Riser removal and machining may reveal shrinkage that extends from the interior of the casting to the near surface area. 2.1.10 surface texture, n—cast surfaces have a multi- directional lay, without the uniform sequence of ridges and valleys of machined surfaces. 2.1.11 welding: 2.1.11.1 weld undercuts, n—narrow elongated depressions that border the weld contour and result from improper welding conditions or inadequate control of welding operations. 2.1.11.2 weld spatter, n—weld metal droplets that solidified against and adhere to the component being welded. 3. Ordering Information 3.1 The inquiry and order should specify the following information: 3.1.1 Acceptance Level—More than one acceptance level may be specified for different surfaces of the same casting (see Section 4), 3.1.2 If any types of discontinuities are unacceptable, 3.1.3 Extent of casting surfaces to be examined, and 3.1.4 Number of castings to be examined. 4. Acceptance Standards 4.1 Levels of acceptance for visual inspection are listed in Table 1. 4.2 Surface discontinuities not covered in Practice A 802/ A 802M shall be a matter of agreement between the purchaser and the manufacturer. TABLE 1 Visual Inspection Acceptance Criteria Surface Feature Level I Level II Level III Level IV Surface texture A1 A2 A3 A4 Nonmetallic inclusions B1 B2 B4 B5 Gas porosity C2 C1 C3 C4 Fusion discontinuities . . .A D1 D2 D5 Expansion discontinuities . . .A . . .A E3 E5 Inserts . . .A . . .A F1 F3 Metal removal marks: Thermal G1 G2 G3 G5 Mechanical H1 H3 H4 H5 Welds J1 J2 J3 J5 A No reference comparator plate is available for this surface feature and level. A 802/A 802M – 95 (2006) 2 5. Keywords 5.1 steel castings; surface acceptance standards; visual ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the risk of infringement of such rights, are entirely their own responsibility. 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A 802/A 802M – 95 (2006) 3 Scope Terminology Ordering Information Acceptance Standards TABLE 1 Keywords