BS-EN-10325-2006.pdf

BRITISH STANDARD BS EN 10325:2006 Steel Determination of yield strength increase by the effect of heat treatment Bake-Hardening-Index The European Standard EN 10325:2006 has the status of a British Standard ICS 77.040.10; 71.080.20 ? BS EN 10325:2006 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 September 2006 © BSI 2006 ISBN 0 580 48971 X National foreword This British Standard was published by BSI. It is the UK implementation of EN 10325:2006. The UK participation in its preparation was entrusted by Technical Committee ISE/NFE/4, Mechanical testing of metals, to Subcommittee ISE/NFE/4/1, Uniaxial testing of metals. A list of organizations represented on ISE/NFE/4/1 can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. Compliance with a British Standard cannot confer immunity from legal obligations. Amendments issued since publication Amd. No. DateComments EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN 10325 August 2006 ICS 77.040.10; 71.080.20 English Version Steel - Determination of yield strength increase by the effect of heat treatment Bake-Hardening-Index Aciers - Détermination de l'augmentation de la limite apparente d'élasticité due à un traitement thermique (index de durcissement à la cuisson Bake-hardening) Stahl - Bestimmung der Streckgrenzenerhöhung durch Wärmebehandlung (Bake-Hardening-Index) This European Standard was approved by CEN on 7 July 2006. CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG Management Centre: rue de Stassart, 36 B-1050 Brussels © 2006 CENAll rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 10325:2006: E EN 10325:2006 (E) 2 Contents Foreword3 1 Scope 4 2 Normative references4 3 Terms and definitions .4 4 Symbols and designations.6 5 Principle6 6 Test equipment 6 7 Test pieces .6 8 Testing procedure6 8.1 Testing conditions.6 8.2 Heat treatment conditions 6 8.3 Determination of Bake-Hardening-Index (BH2) .7 9 Test report7 EN 10325:2006 (E) 3 Foreword This document (EN 10325:2006) has been prepared by Technical Committee ECISS/TC 1 “Steel - Mechanical testing”, the secretariat of which is held by AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by February 2007, and conflicting national standards shall be withdrawn at the latest by February 2007. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 10325:2006 (E) 4 1 Scope This document specifies the method for the determination of yield strength increase by the effect of heat treatment (Bake-Hardening-Index) for steel. NOTE This test is applied in particular, to steels showing a mechanism of bake hardening, which are specially intended for automotive industry. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 10002-1:2001, Metallic materials Tensile testing Part 1: Method of test at ambient temperature 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 10002-1:2001 and the following apply. NOTE However it should be noted that in the context of this document, the term “yield strength“ also covers 0,2 % proof strength in addition to its definition in EN 10002-1. 3.1 Bake-Hardening-Index (BH2) increase of yield strength between a reference condition after a 2 % plastic pre-strain and the condition obtained after a heat treatment simulating the usual industrial paint processes (see Figure 1) NOTE The heat treatment of simulation is specified in 8.2. EN 10325:2006 (E) 5 Key 1 Stress 2 Strain 3 Application of a 2 % plastic pre-strain 4 Tensile test after heat treatment on the same test piece Figure 1 Illustration of the determination of BH2 EN 10325:2006 (E) 6 4 Symbols and designations The symbols used in this document and the corresponding designations are given in Table 1. Table 1 Symbols and designations Symbol Unit Designation Rp2,r MPa a Stress corresponding to a 2 % plastic prestrain measured on the test piece ReL,t MPa Lower yield strength measured on the test piece initially prestrained at 2 % and then heat treated Rp0,2,t MPa 0,2 % proof strength measured on the test piece initially prestrained at 2 % and then heat treated BH2 MPa Bake-Hardening-Index a 1 MPa = 1 N/mm². 5 Principle The test determines an index giving the increase of yield strength of a test piece submitted to a 2 % plastic pre- strain, then to a specified heat treatment. 6 Test equipment The test equipment shall be in accordance with EN 10002-1. 7 Test pieces The test pieces shall be according to EN 10002-1. 8 Testing procedure 8.1 Testing conditions The tensile test shall be performed according to Annex A of EN 10002-1:2001. The testing rate given in EN 10002-1 for the beginning of the tensile test, shall only be increased after the determination of ReL or Rp0,2. During the pre-straining of the test pieces, the testing rate shall be kept constant up to a plastic pre-strain of (2 ± 0,05) %. All tensile tests used to characterize a steel shall be performed with the same actual testing rate. 8.2 Heat treatment conditions A test piece temperature of 170 °C shall be achieved within 7 min. The heat treatment time of (20 ± 0,5) min commences when a test piece temperature of 168 °C is achieved. The heat treatment equipment used shall be capable of keeping the prescribed test piece temperature (i.e. 170 °C) at ± 2 °C. The temperature measuring device shall have a resolution of no more than 1 °C with a maximum measuring uncertainty of ± 2 °C. After the holding time, the test piece shall be air cooled to room temperature, i.e. (23 ± 5) °C. EN 10325:2006 (E) 7 8.3 Determination of Bake-Hardening-Index (BH2) The BH2-Index is the difference between the proof strength, Rp2,r, of the 2 % plastically strained test piece (modulus of elasticity of steel considered to be 200 000 MPa) and the lower yield strength, ReL,t, or the proof strength, Rp0,2,t, of the same test piece after an additional heat treatment at 170 °C with a holding time of 20 minutes. Determining ReL,t or Rp0,2,t after heat treatment, the cross-sectional area of the test piece after a plastic pre-strain shall be used. rp2,p0,2tteL,2 orRRRBH=)( (1) 9 Test report 9.1 If testing of BH2 is carried out in combination with the conventional test according to EN 10002-1, the Bake- Hardening-Index shall be added to the test report. 9.2 If testing of BH2 is carried out separately, the test report shall contain at least the following information: a) reference to this European Standard; b) identification of the test piece; c) location and direction of sampling; d) test result. BS EN 10325:2006 BSI 389 Chiswick High Road London W4 4AL BSI British Standards Institution BSI is the independent national body responsible for preparing British Standards. It presents the UK view on standards in Europe and at the international level. It is incorporated by Royal Charter. Revisions British Standards are updated by amendment or revision. 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