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GB/T 20671.6-2020 English PDF (GBT20671.6-2020)

GB/T 20671.6-2020 English PDF (GBT20671.6-2020)

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GB/T 20671.6-2020: Classification system and test methods for nonmetallic gasket materials -- Part 6: Standard test method for adhesion of gasket materials to metal surfaces

This Part of GB/T 20671 specifies the principle, instruments and apparatuses, sample, test procedure, precision and test report for the test of adhesion of nonmetallic gasket materials to metal surfaces. This Part applies to the determination of adhesion of nonmetallic gaskets, such as polytetrafluoroethylene gaskets, fiber gaskets, graphite gaskets, to metal surfaces.
GB/T 20671.6-2020
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 23.100.60
Q 69
Replacing GB/T 20671.6-2006
Classification system and test methods for
nonmetallic gasket materials - Part 6: Standard test
method for adhesion of gasket materials to metal
surfaces
ISSUED ON: JUNE 02, 2020
IMPLEMENTED ON: APRIL 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the PEOPLE Republic of
China.
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Principle ... 5
4 Instruments and apparatuses ... 6
5 Sample ... 7
6 Test procedure ... 8
7 Precision ... 10
8 Test report ... 10
Foreword
GB/T 20671, Classification system and test methods for nonmetallic gasket materials, is divided into 11 parts:
-- Part 1: Standard classification system for nonmetallic gasket materials; -- Part 2: Standard test method for compressibility and recovery of gasket materials;
-- Part 3: Standard test method for fluid resistance of gasket materials; -- Part 4: Standard test method for sealability of gasket materials;
-- Part 5: Standard test method for creep relaxation of gasket materials; -- Part 6: Standard test method for adhesion of gasket materials to metal surfaces;
-- Part 7: Standard test methods for tension testing of nonmetallic gasket materials;
-- Part 8: Standard test method for flexibility of non-metallic gasket materials; -- Part 9: Standard test method for binder durability of cork composition gasket materials;
-- Part 10: Standard practice for evaluating thermal conductivity of gasket materials;
-- Part 11: Standard practice for determining resistance of synthetic
polymeric materials to fungi.
This Part is Part 6 of GB/T 20671.
This Part was drafted in accordance with the rules given in GB/T 1.1-2009. This Part replaces GB/T 20671.6-2006, Classification system and test methods for nonmetallic gasket materials - Part 6: Standard test method for adhesion of gasket materials to metal surfaces. Compared with GB/T 20671.6-2006, the main technical changes, except editorial changes, are as follows:
-- Modify the scope (see Chapter 1; Chapter 1 of version 2006);
-- Add the scope of application of this Part (see Chapter 1);
-- In the scope, delete ?€?Use the value that is expressed in International System of Units (SI) as the standard?€? and ?€?This Part does not involve
Classification system and test methods for
nonmetallic gasket materials - Part 6: Standard test
method for adhesion of gasket materials to metal
surfaces
1 Scope
This Part of GB/T 20671 specifies the principle, instruments and apparatuses, sample, test procedure, precision and test report for the test of adhesion of nonmetallic gasket materials to metal surfaces.
This Part applies to the determination of adhesion of nonmetallic gaskets, such as polytetrafluoroethylene gaskets, fiber gaskets, graphite gaskets, to metal surfaces.
2 Normative references
The following documents are indispensable for the application of this document. For dated references, only the dated version applies to this document. For undated references, the latest edition (including all amendments) applies to this document.
GB/T 20671.1, Classification system and test methods for nonmetallic gasket materials - Part 1: Standard classification system for nonmetallic gasket materials
GB/T 20671.5-2020, Classification system and test methods for nonmetallic gasket materials - Part 5: Standard test method for creep relaxation of gasket materials
3 Principle
Place the gasket material sample between two parallel metal flat circular plates as a flat circular plate-sample assembly. After the assembly bears the load under the specified conditions, separate the sample from the flat circular plate; measure the required tensile force to evaluate the adhesion of gasket to metal surface. The maximum test temperature that is recommended by this method is 205 ??C.
Note 1: The tensile force that is required to separate the plates may exceed 8896 N.
Note 2: This set of equipment can also be used to determine the creep
relaxation according to Method B of GB/T 20671.5-2020.
4 Instruments and apparatuses
4.1 Hot air circulating oven: The temperature can be adjusted to 100 ??C ?? 2 ??C or other temperatures that are approved by both the supplier and the buyer. 4.2 Test device: It consists of two flat circular plates with holes (the two holes on the side of each flat circular plate are separated by 180??), a calibrated bolt, a washer, a nut, a set of dial indicator components (the device is compatible with the device of Method B in GB/T 20671.5-2020), a steel positioning pin and a steel bracket or a similar positioning pin clamping device. The steel bracket is connected to the chuck of the tensile testing machine, so that the tensile force that is provided by the testing machine is perpendicular to the surface of the flat circular plate (as shown in Figure 1). The surface of the flat circular plate shall be kept smooth, which is obtained by using 8/0 dry emery paper to polish (refer to 5.2), or other surface treatments which are determined by negotiation between the supplier and the buyer. The flat circular plate is a flat circular specific metal plate, whose diameter is 76 mm and minimum thickness is 25.4 mm. There shall be a cut-through hole, whose diameter is 10.3 mm, in the center of each flat circular plate. All sides of the flat circular plate shall be slightly chamfered; the two sides shall be machined to ensure parallelism. The
roughness of the contact surface between each plate and the sample is Ra ??? 1.6 ??m.
4.3 Tensile testing machine: the loading rate is 1.3 mm/min; it is equipped with a device to record or display the maximum tensile force.
4.4 Stretch connectors, namely upper and lower brackets.
4.5 8/0 dry emery paper.
4.6 Molybdenum disulfide: powder or spray.
4.7 Socket wrench: 14.3 mm (9/16 in).
be used to measure the fine grinding condition of the surface before the test. Then, use the laboratory reagent acetone to scrub the flat circular plate clean to remove any foreign impurities. After the flat circular plate is cleaned, before the test, handle it only from the edge; do not touch the cleaned surface by hand. See 6.1 for the time limit after cleaning.
5.3 Adjust the cut samples according to the adjustment procedures of various materials that are specified in GB/T 20671.1. When it is agreed by both the supplier and the buyer, the adjustment conditions can be changed according to the special application requirements.
5.4 Before assembling the test device, place the components of the test device - the metal flat circular plate, the calibrated bolts, the washers, and the nuts - at 21 ??C ~ 27 ??C for at least 4 h.
6 Test procedure
6.1 Within 30 minutes after the flat circular plate is cleaned, carefully clamp the adjusted annular gasket sample between the two flat circular plates. Carefully adjust the positioning pin hole on one flat circular plate to a 90?? from the positioning pin hole on the other flat circular plate.
6.2 Use molybdenum disulfide powder or spray (oil is not recommended) to lightly lubricate the threads of washers and bolts. Carefully pass the bolt through the two plates, the sample and the washer; screw on the nut; use fingers to tighten it lightly. During the operation, avoid the lubricator from contaminating the sample and the flat circular plate surfaces.
6.3 Set the socket wrench on the nut. Then, install the dial indicator assembly on the top of the calibrated bolt; tighten it by hand; adjust the dial indicator pointer to zero reading.
6.4 Use a wrench to tighten the nut, until the dial indicator reading reaches the specified value; record the actual reading (D0) of the dial indicator. Continuously apply the pressure, to reach the specified load within 3 s. Apply a pressure of 26.7 kN; the extension of the bolt is usually 0.122 2 mm ~ 0.127 0 mm. For Class 2 or Class 3 gasket materials, the pressure can be appropriately reduced according to the opinions that are agreed by the supplier and the buyer. 6.5 Remove the dial indicator and the socket wrench.
6.6 Put the flat circular plate/sample assembly into a hot air circulating oven at 100 ??C ?? 2 ??C for 22 h, unless otherwise specified.

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