VW50093_EN_2012-07

Group Standard VW 50093

Issue 2012-07

Class. No.:

A6600Descriptors:cast, casting, light metal cast, pore, porosity

Porosity of Castings

Requirements

Preface

This Standard supersedes Volkswagen Standard VW 50097 "Porosity of metal castings

(VDG P201)" (VDG = Association of German Foundry Experts – German abbreviation)

Previous issues

VW 50097: 2002-12, 2007-07

Changes

The following changes have been made compared with VW 50097: 2007-07:

–Application as per VDG specification P202

Contents Page

Scope .........................................................................................................................2Definitions ..................................................................................................................2Designation ................................................................................................................2Explanation of the designation system .......................................................................2Deviations from and supplements to VDG specification P202 ...................................5Grading of porosity specifications in drawings ...........................................................6Requirements .............................................................................................................6Delivery of components ..............................................................................................6Definition of porosity ...................................................................................................6Testing of porosity (7)

Recourse claims .........................................................................................................7Applicable documents (71)

2

3

3.1

3.2

3.3

4

4.1

4.2

5

6

7Verify that you have the latest issue of the Standard before relying on it.

This electronically generated Standard is authentic and valid without signature.

The English translation is believed to be accurate. In case of discrepancies, the German version is alone authoritative and controlling.

Numerical notation acc. to ISO/IEC Directives, Part 2.Page 1 of 7

All rights reserved. No part of this document may be provided to third parties or reproduced without the prior consent of the Standards Department of a Volkswagen Group member.? Volkswagen Aktiengesellschaft

VWNORM-2012-05i

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VW 50093: 2012-07

Scope

This Standard defines the requirements for the porosity of castings regardless of the casting proc‐ess used.

Definitions Definitions as per VW 50099.Surface to which a porosity specification and the evaluation relates (cor‐responding to VDG P202)Generating a flat, rectangular surface by unfolding the inner surface of a

hollow cylinder.

Designation The underlying designation system and the definition of the reference surfaces correspond to the BDG guideline (VDG specification) VDG P202. Details on the designation system can be obtained from the specification.Deviations from and supplements to the provisions set forth in the specification are listed in this Standard in section 3.2.

The permissible porosity of a casting is entered in the respective finished part drawing.

Explanation of the designation system The designation system of the porosities is composed of the following parameters as per the VDG specification VDG P202:

–[R z ] – Roughness of the reference surface:

[R z ] is specified in μm. If the roughness information is missing, [R z ] = 0 applies automatically.This corresponds to a metallographically polished microsection.–[%] – Pore content:

The pore content is defined as the maximum permissible pore volume in percent for the

agreed reference surfaces.

–[?] – Pore diameter/pore length:

The maximum permissible pore diameter is specified in mm.

–[A] – Distance between adjacent pores:

The minimum distance to be adhered to between two adjacent pores is described with this pa‐rameter. The distance specification [A] is an integer factor with which the diameter of the smaller of two adjacent pores is multiplied and the minimum distance is calculated.

–[U] – Disregarded pores:

The value [U] indicates up to which diameter pores are disregarded in the reference surface evaluation.

–[Z] – Number of pores :

This parameter indicates the maximum permissible number of individual pores per reference surface as an integer value. Pore accumulations are treated as individual pores here.

–

[H], [H R ], or [H K ] – Pore accumulations:1 2 Reference surface:

Unfold rule:3 3.1

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VW 50093: 2012-07

A pore accumulation is present where the distance between two adjacent pores is less than

the diameter of the smaller pore.

–[H] – (without subscript) refers to pore accumulations in the entire reference surface

–[H R] – refers to pore accumulations in the reference surface edge area (outer third of wall)–[H K] – refers to pore accumulations in the reference surface core area (inner third of wall) The value for [H], [H R] and [H K] can have the following binary values:

–0 = pore accumulations impermissible

– 1 = pore accumulations permissible

If a maximum pore diameter is specified in addition to the pore accumulation, the pore accu‐mulations are treated as individual pores. That is, pore accumulations with diameters that ex‐ceed the maximum permissible individual pore diameter are not permissible.

–[N], [N R], or [N K] – Localized porosities:

A localized porosity is present whenever the diameter of a pore accumulation exceeds the

maximum permissible diameter for individual pores.

–[N] – (without subscript) refers to localized porosities in the entire reference surface

–[N R] – refers to localized porosities in the reference surface edge area (outer third of wall)–[N K] – refers to localized porosities in the reference surface core area (inner third of wall) [N], [N R], or [N K] can have the following binary values:

–0 = localized porosity impermissible

– 1 = localized porosity permissible

If [N], [N R], or [N K] is listed in the pore key, but a value is not indicated, the value 1 is automati‐cally applicable. That is, localized porosity is permissible in the pertinent area.

NOTE 1 The permissibility of localized porosities automatically implies pore accumulation per‐missibility as well. If localized porosities are impermissible, this does not necessarily preclude the permissibility of pore accumulations.

Representation: (Standard) – [Parameter 1][Value]/[Parameter 2][Value]/ ... [Parameter n][Value] Information in parentheses must be indicated; information in square brackets may be indicated, in which case the parameters can be arranged in any order.

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VW 50093: 2012-07

For examples, see figure 1:

Figure 1

NOTE 2 Due to missing roughness information, the development of a metallographic microsection is also stipulated by this pore key.

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VW 50093: 2012-07 Deviations from and supplements to VDG specification P202

3.2

The following deviations from VDG specification VDG P202 provisions will be mandatory when this Standard becomes final:

–[R z] – Roughness:

The casting skin and processed surfaces are exempted from surface quality (roughness) spe‐cifications in porosity keys. Even if porosity keys contain roughness specifications for these surfaces (e.g., in the case of collective porosity specifications in terms of the VDG specifica‐tion), the surface quality specified in the drawing applies automatically.

–[%] – Pore content:

If the specification for a pore content is <5%, then in addition to the provisions set forth in the VDG specification for the reference surface and in addition to the specified pore content of the reference surfaces, the pore content of any sub-section of a reference surface must not be greater than 4%. Here it must be noted that the sub-sections have fixed dimensions of

(4 x 3) mm2.

NOTE 3 This supplement maps the provisions of the predecessor Volkswagen Standard

VW 50097 for pore classes D1 to D4.

If a pore content of <5% is specified for iron and steel castings, this 4% rule can be overruled by adding an explicit supplement to the drawing note.

NOTE 4 The 4% rule cannot be overruled for any other materials.

–[?] – Pore diameter/pore length:

This Standard provides exclusively for the use of the comparison diameter (pore length, max.

pore dimension, max. Feret). Therefore, the corresponding subscript – the specification

VDG P202 includes the suffix L for this purpose – can be omitted.

–[U] – Disregarded pores:

Deviating from specification P202, the parameter [U] is provided exclusively for processed sur‐faces. If not indicated, [U] automatically comes from the quality of the test surface and of the optical aid specified for the test.

NOTE 5 Specifications of [U] must be used only for processed surfaces that provide a sealing function, with some exceptions.

–[Z] – Number of pores:

This Standard stipulates the use of this parameter for processed surfaces only.

–For porosity specifications for holes and threads, the reference surface is always the entire, contiguous lateral surface of the area, for which a uniform porosity specification has been de‐fined. Exempt from this provision are sealing surfaces in holes. The unfold rule applies to

these areas. The reference surface rule as per PV 6093 "Porosity Determination as per

VW 50093" must be applied to the surface that is formed in this way. That is, the smaller of the two edge lengths of the rectangle that is formed by unfolding defines the edge length of the square reference surface.

–Deviating from the specification, this Standard is applicable regardless of the metal type and casting process. Following agreement with the appropriate development laboratory, this

Standard can also be applied to injection-molded castings made of polymer materials. A corre‐sponding drawing note is required for this.

–An exclusive porosity specification for processed surfaces in the drawing also always contains

a standard porosity specification corresponding to section 4.2.

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VW 50093: 2012-07

Grading of porosity specifications in drawings

The following grading rules apply to the definition of drawing notes:

[%]Integer steps from 1% to 4%; integer steps of five as of 5%. A specification

of 0% is not valid. The specification of values of <5% is only permissible in

agreement with the development laboratory, with the exception of steel and

cast iron materials.

[?]This parameter must be indicated in steps of 0,5 mm. The specification of

diameters of <0,5 mm is not permissible.

[U]Specifications of values below the optical resolution capacity of the test

method stipulated are impermissible. However, if lesser limits are specified,

the limiting resolution of the test method is automatically binding, depend‐

ing on the quality of the examined reference surface. [U] is graded in steps

of 0,1 mm.

Requirements

Delivery of components The supplier must automatically enclose test reports for components presented for testing, first sample inspection, or build sample approval. These reports must clearly identify all component properties required according to this Standard.

NOTE 6 Castings that are presented for build sample approval (BMG) must be regarded as boun‐dary samples for future deliveries from the respective supplier. That is, by presenting a casting for the build-sample test, the supplier undertakes to only supply parts of the same or higher quality in the future. This applies to casting porosity in particular.

Definition of porosity

If this Standard is cited in a drawing, in other standards, or in performance specifications, or if po‐rosity specifications referencing VW 50093 are cited in a drawing, in other standards, or in perform‐ance specifications, then the following general standard specifications apply to the entire casting:–

Castings made of steel and iron cast materials VW 50093–%1–

Castings made of zinc base alloys VW 50093–%10–All other castings VW 50093–%5Porosity specifications always refer to a square reference surface (see PV 6093).

Deviating requirements must be specified more precisely and must adher to all the specifications of this Standard. An exclusive limitation of porosity specifications to specific test levels or a general exclusion from the standard specifications described here must be done explicitly and in writing in the drawing. Unless otherwise specified, mechanical damage on machined surfaces must be trea‐ted like pores.

The specifications for maximum permissible individual pores inside the casting must be dimen‐sioned such that they can also be evaluated in a nondestructive manner – preferably by X-ray test‐ing – without problems. The limiting resolution of the X-ray test is 6% of the wall thicknesses irradi‐ated in total. To that effect, when specifying the permissible individual pore size, the degree to which the casting can be irradiated must be taken into account depending on its geometry.

3.3 4

4.1

4.2

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VW 50093: 2012-07

If the build samples are provided by a sole supplier or a first supplier, then the supplier must aim to make the max. porosity specified in the drawing the limit porosity. If the supplier is unable to fulfill this porosity requirement, it must provide suitable documentation and verfication of this. The docu‐mentation must clearly identify all affected areas. The same applies to the first delivery of castings that are not subject to build sample approval.

If the test is positive, the porosity of the tested castings must be entered in the finished part draw‐ing, provided the porosity exceeds the drawing specifications and represents the general state of the art. The existing drawing note retains its validity in all other cases.

NOTE 7 It is recommended to mark strength- or process-critical areas on castings, in addition to a general porosity specification, as preferred test areas in the drawing. A periodic examination of po‐rosity should always include these areas. The exclusive application of the porosity specification to these testing areas is only permissible if clearly specified in the wording.

Testing of porosity The porosity of the castings must be tested in compliance with the drawing notes as per PV 6093.If the supplier uses a test method other than that prescribed to test porosity, the supplier must es‐tablish a correlation between this method and the prescribed method for the respective casting.NOTE 8 When performed correctly, the X-ray CT scan is recognized as an adequately correlating test method. However, a supplier may use any test method for periodic production monitoring. Only those test results produced using the prescribed method or a correlating method will be valid in ar‐bitration cases.

Recourse claims Should the supplier violate parts of this Standard, in particular section 4.1 and section 4.2, the sup‐plier may be billed for the resultant additional testing costs.

NOTE 9 The same applies to all other material properties of castings specified in drawings.Applicable documents

The following documents cited in this Standard are necessary to its application.

Some of the cited documents are translations from the German original. The translations of Ger‐man terms in such documents may differ from those used in this Standard, resulting in terminologi‐cal inconsistency.

Standards whose titles are given in German may be available only in German. Editions in other languages may be available from the institution issuing the standard.

PV 6093Porosity Determination as per VW 50093VW 50099Foundry and Casting Technology; Definitions VDG P202Volume Deficits of Castings Made from Aluminum, Magnesium, and Zinc

Casting Alloys 5 6 7