1 Scope
This document specifies a combination of bolts, screws, studs and nuts manufactured from carbon steel or alloy steel, in accordance with GB/T 3098.1 and GB/T 3098.2 performance level of bolts, screws, studs and nuts with flat washers, in the ambient temperature of 10 ℃ ~ 35 ℃ when the test mechanical and physical properties.
Note 1: These types of flat washers can also be used together with other fasteners, such as self-tapping screws.
When tested at ambient temperatures of 10 °C to 35 °C, flat washers that meet the requirements of this document may not maintain the specified mechanical and physical properties at high and/or low temperatures.
Note 2: The applicable operating temperature for flat washers meeting the requirements of this document is 50 °C to +150 °C. When the operating temperature exceeds 50 °C to +150 °C, they may not maintain the specified mechanical and physical properties. When the use of temperature exceeds a 50 ℃ ~ +150 ℃, or even up to +300 ℃, the user is recommended to the relevant aspects of expert advice.
This document applies to flat washers and assemblies made of carbon steel or alloy steel with a thickness of 0.2 mm to 12 mm in accordance with the following provisions:
Flat washers (with or without pattern, ribs or chamfers);
Square flat washers;
Flat washers with square holes;
Shaped flat washers.
The following performance requirements are not specified in this document:
Corrosion resistance
Weldability.
2 Normative references
The content of the following documents through the normative references in the text and constitute the essential provisions of this document. Among them, note the date of the reference document, only the date of the corresponding version applies to this document; do not note the date of the reference document, its latest version (including all the revision sheets) applies to this document.
GB/T 97.4 Flat washers for screw and washer assemblies (GB/T 97.4-2002, eqv ISO 10673:1998)
GB/T 97.5 Flat washers, for self-tapping screws and washer assemblies (GB/T 97.5-2002, eqv ISO 10669:1999 )
3 Terminology and definitions
There are no terms and definitions to be defined in this document.
4 Designations
The following designations are applicable to this document.
5 Marking system
The performance class of a flat washer consists of two parts, a number and a symbol:
The number indicates the minimum Vickers hardness value (see Table 3);
The letter HV indicates the Vickers hardness.
Example: In accordance with the provisions of table 3, the minimum Vickers hardness of 200 steel flat washers performance level marked as 200 HV.
If you can comply with the provisions of table peal and table 3, the marking system specified in this document can also be used for specifications beyond the standard thickness range (e.g. t>12 mm).
Although this document provides a number of performance levels, but does not mean that all performance levels are applicable to all flat washers and / or all bolts, nuts, washers combination. The performance class combinations of flat washers with bolts, screws, studs and nuts are shown in Table 1.
For threaded self-forming screws and screws with soft materials (such as plastic, wood, etc.) connection screws, should be determined according to their intended use and the combination of flat washer performance levels.
6 Material
Table peal provides different performance levels of flat washers with carbon steel and alloy steel chemical composition limits. The chemical composition should be in accordance with the provisions of the relevant national standards.
Note: Alloy steels include spring steels and alloy spring steels that can be used for flat washers.
For flat washers to be hot dipped galvanised, the material requirements of GB/T 5267.3 should be met.
If the assembly is hardened and tempered as a whole, it can be supplied as an unheated flat washer. In this case, the chemical composition of the flat washers shall be agreed between supply and demand in accordance with GB/T 9074.1.
When self-tapping screw assemblies are surface hardened in accordance with GB/T 97.5, the carbon content of the flat washers should not exceed 0.12%. Each manufacturing batch of flat washers should be manufactured from the same furnace number of raw materials.
7 mechanical and physical properties
Specify the performance level of flat washers, at ambient temperature, whether in the manufacturing process test or final inspection, should be in line with the mechanical and physical properties specified in Table 3.
Chapter 8 for the inspection of flat washers in accordance with the provisions of Table 3 provides the applicable test methods and arbitration test methods. For 380 HV performance level of flat washers, when there are special requirements, should be in accordance with Appendix A for ductility testing.
8 Test methods
8.1 Hardness test
8.1.1 General
The purpose of the hardness test is to:
Determine the hardness of the flat washer in accordance with the minimum and maximum requirements specified in Table 3; - for quenched and tempered flat washers, in line with the material requirements specified in Table 2.
This test applies to all performance classes of flat washers.
Flat washers should be tested in the received state, except for assembled flat washers for assemblies that need to be hardened and tempered. Table 4 should be carried out in accordance with the appropriate surface or flat washer cross-section hardness test.
8.2 Decarburisation test
8.2.1 General rules
The purpose of the decarburisation test is to detect surface decarburisation and depth of decarburisation of knurled or ribbed flat washers of performance class 300 HV and all flat washers of performance class 380 HV.
The decarburised area is shown in Figure 4.
8.2.2 Metallographic method
8.2.2.1 Specimen preparation
Flat washers should be tested in the received condition, after removal of the coating and plating.
The specimen should be taken from the radial section through the centre line of the hole. The specimen shall be embedded in plastic or mounted in a fixture base or clamp. After mounting, the surface should be ground and polished until it is ready for metallographic examination to preserve the original properties of the surface base metal (good metallography).
Note: Immersion in a 3% nitric acid-ethanol etching solution (a mixture of concentrated nitric acid and ethanol) will show changes in the metallographic organisation due to decarburisation.
8.2.2.2 Test procedure
Specimens should be examined under a microscope, unless otherwise agreed, at a magnification of 100 times.
If the microscope has a frosted glass screen, the degree of decarburisation can be measured directly with the aid of a scale. If measured with an eyepiece, a microscope with a crosshair or scale should be used.
8.3 Carbon increase test
8.3.1 General rules
The purpose of the carbon increase test is to determine whether the surface of the flat washer is carbonized during the heat treatment process. Carbon gain should be determined in the hardness test through the radial section of the centre line of the hole.
This test applies to knurled or ribbed flat washers with a performance class of 300 HV and all flat washers with a performance class of 380 HV, with a minimum thickness of 0.4 mm.
8.3.2 Test procedure
Specimens should be prepared in accordance with 8.2.2.1, but do not need to be corroded.
Measure the Vickers hardness at point 1 and point peal as shown in Figure 5. The test force shall be 2.942 N (Vickers hardness test HVO.3).
9 Marking
9.1 General rule
According to the requirements of this document manufactured flat washers, only the full compliance with the technical requirements of this document, can be marked in accordance with the marking system in chapter 5.
9.2 Flat washer markings
Flat washer marking can be determined by the manufacturer, or by the supply and demand agreement; supply and demand agreement, flat washer marking should include the manufacturer's identification mark and performance level.
Dealers selling flat washers with their own identification mark should be considered as the manufacturer's identification mark.
Flat washers shall not be marked with raised lettering. Concave markings are generally not recommended because they can alter the torque-clamping force relationship of the bolt-nut joint or can create stress concentrations that can lead to initial cracking. Long-lasting marks can be obtained by other processing methods, such as laser marking.
When marking performance levels, the performance level code or the clock face method marking symbol should be marked in accordance with Table 5.
9.3 Packaging markings
In the scope of this document, all performance levels of flat washers in the packaging, there should be a mark (for example: through the label). Marking should include the manufacturer and/or seller's identification mark and the performance level specified in Chapter 5, as well as the manufacturing lot number defined in GB/T 3099.4.
Appendix A (normative) Performance class 380 HV Ductility test for flat washers
1 Scope
2 Normative references
3 Terminology and definitions
4 Designations
5 Marking system
6 Material
7 mechanical and physical properties
8 Test methods
9 Marking
Appendix A (normative) Performance class 380 HV Ductility test for flat washers
