1 Scope
This part of GB/T 3098 specifies the mechanical properties of tapping screws made of austenitic, martensitic and ferritic steel grades of corrosion-resistant stainless steels, when tested over an ambient temperature range of 10℃ to 35℃. Properties vary at higher or lower temperatures.
This part applies to tapping screws with threads from ST2,2 up to and including ST8, in accordance with GB/T 5280.
This part does not apply to screws with special properties, such as weldability.
Note: The designation system of this part of GB/T 3098 can be used for sizes outside the limits given in this clause (e.g. d > ST8), provided that all applicable mechanical and physical requirements of the hardness classes are met.
This part of GB/T 3098 does not define corrosion or oxidation resistance in particular environments. However, some information on materials for particular environments is given in Annex C. Regarding definitions of corrosion and corrosion resistance, see GB/T 10123.
The aim of this part of GB/T 3098 is the classification of corrosion-resistant stainless steel tapping screws into hardness classes.
Corrosion and oxidation performances and mechanical properties for use at elevated or sub-zero temperatures can be agreed on between the user and the manufacturer in each particular case. Annex D shows how the risk of intergranular corrosion at elevated temperatures depends on the carbon content.
All austenitic stainless steel fasteners are normally non-magnetic in the annealed condition; after cold working, some magnetic properties can be evident (see Annex E).
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.
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GB/T 90.3 Fasteners — Quality Assurance System (GB/T 90.3-2010, ISO 16426:2002, IDT)
GB/T 3098.6 Mechanical Properties of Fasteners — Stainless Steel Bolts, Screws and Studs (GB/T 3098.6-2014, ISO 3506-1:2009, MOD)
GB/T 4334 Corrosion of Metals and Alloys — Test Methods for Intergranular Corrosion of Stainless Steels (GB/T 4334-2008, ISO 3651-1:1998 & ISO 3651-2:1998, MOD)
GB/T 4340.1 Metallic Materials - Vickers Hardness Test — Part 1: Test Method (GB/T 4340.1-2009, ISO 6507-1:2005, MOD)
GB/T 5267.4 Passivation of Corrosion-resistant Stainless-steel Fasteners (GB/T 5267.4-2009, ISO 16048:2003, IDT)
GB/T 5280 Tapping Screws Thread (GB/T 5280-2002, idt ISO 1478:1999)
3 Designation, Marking and Finish
3.1 Designation
The designation system for stainless steel grades and hardness classes for tapping screws is given in Figure 1. The designation of the material consists of two blocks, which are separated by a hyphen. The first block designates the steel grade and the second block, the hardness class.
The designation of the steel grade (first block) consists of one of the letters and and digits:
Foreword II
1 Scope
2 Normative References
3 Designation, Marking and Finish
4 Chemical Composition
5 Mechanical Properties
6 Test Methods
Annex A (Normative) Description of the Groups and Grades of Stainless Steels
Annex B (Informative) Stainless Steel for Cold Heading and Extruding
Annex C (Informative) Austenitic Stainless Steels with Particular Resistance to Chloride Induced Stress Corrosion
Annex D (Informative) Time-Temperature Diagram of Intergranular Corrosion in Austenitic Stainless Steels, Grade A2 (18/8 Steels)
Annex E (Informative) Magnetic Properties for Austenitic Stainless Steels
Bibliography
