ISO 898-2:2022 ファスナー — 炭素鋼および合金鋼で作られたファスナーの機械的特性 — Part 2: 特定の特性クラスを持つナット | ページ 2

Foreword

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The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, 1. In particular, the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, 2 (see www.iso.org/directives ).

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This document was prepared by Technical Committee ISO/TC 2, Fasteners, Subcommittee SC 12, Fasteners with metric internal thread, in collaboration with the European Committee for Standardization (CEN) Technical Committee CEN/TC 185, Fasteners, in accordance with the Agreement on technical cooperation between ISO and CEN (Vienna Agreement).

This fourth edition cancels and replaces the third edition (ISO 898-2:2012) which has been technically revised.

The main changes are as follows:

• property class 9 has been deleted completely, and nuts with fine pitch thread and property class 5 have been deleted (see Introduction);
• nuts with fine pitch thread in style 2 and property class 12 have been added for diameters 18 mm to 39 mm (see Tables 4, 6 and 10);
• styles have been more precisely specified for standard hexagon nuts according to their minimum height, and styles have been specified for other nuts according to their minimum design thread height (see 5.1);
• additional statements for thin nuts and jam nuts have been added (see Clause 6);
• additional statements for hot dip galvanized nuts have been added by referencing ISO 10684;
• relation to material, heat treatment and steel microstructure (see Clause 7):
  • the minimum carbon content has been added (see Tables 3 and 4),
  • the minimum manganese content has been specified to 0,25 % for all Non-Quenched and Tempered nuts (NQT) and has been raised to 0,45 % for all Quenched and Tempered nuts (QT) (see Tables 3 and 4),
  • the table footnote for free cutting steel has been reworked (see Tables 3 and 4),
  • the minimum tempering temperature has been added for QT nuts (see Tables 3 and 4), and a reference retempering test has been added (see 10.4),
  • for nuts that may optionally be quenched and tempered at the manufacturer’s discretion, detailed specifications have been added (see 7.2),
  • specifications for steel microstructure have been added for NQT and QT nuts (see 7.4.1, 7.4.2 and 10.3);

• relation to proof load:

  • the proof load values for nuts with coarse pitch thread and property classes 6 and 8 have been raised for sizes M27 to M39 (see Introduction, Table 5, and Annex C),
  • the maximum hole diameter for the grip has been corrected for diameters 5 mm and 6 mm (see Table 11), and reference to additional proof load specifications has been added for prevailing torque nuts (see 10.1);

• relation to hardness:

  • the reference Vickers hardness values have been recalculated, and conversion into Brinell and Rockwell hardness has been adjusted (see Introduction and 8.3),
  • hardness determined on the bearing surface (see 10.2.4 a) and hardness determined in the transverse section at mid-height of the nut (see 10.2.4 b) have been added for routine inspection,
  • the test method for hardness determined in the thread has been improved and the test force has been specified according to the pitch dimension (see 10.2.5),
  • for QT nuts, the test methods for hardness in the core (see 10.2.6) and uniformity of hardness (see 10.2.7) have been added,
  • requirements for hardness have been clarified (see 10.2.8 and 10.2.9);

• inspection documents have been referenced in accordance with ISO 16228 for fasteners (see 9.4);

• marking and labelling have been revised, and all nuts conforming to this document are to be marked whatever their shape (see Clause 11);

• Annex B, Design principles for nuts, has been improved;

• Annex C, Nominal stress under proof load, has been added.