GB/T 45982.3-2025Micro joining of 2nd generation high temperature superconductors - Part 3: Test methods for joints (English PDF)

Foreword

This document is in accordance with the provisions of GB/T 1.1-2020 "Guidelines for standardization work Part 1: Structure and drafting rules for standardization documents" Drafting.

This document is Part 3 of GB/T 45982 "Micro-connections of the second generation of high temperature superconductors".

MicroConnect has published the following sections.

--- Part 1: Process requirements;

--- Part 2: Qualification of welding and testing personnel;

--- Part 3: Test methods for joints.

This document is modified to adopt ISO 17279-3:2021 "Welded second-generation high-temperature superconductors microjoints Part 3: Joint test methods".

Compared with ISO 17279-3:2021, this document has many structural adjustments.

See Appendix A for the table.

The technical differences between this document and ISO 17279-3:2021 and their reasons are as follows.

a) The scope of application of this document (see Chapter 1) has been changed to apply to my country's technical conditions;

b) The normative reference document GB/T 19866 is used instead of ISO 15607:2019 (see Chapter 3);

c) Added explanations of 19 symbols (see Chapter 4) to facilitate the application of this document;

d) Deleted "Except for visual inspection, other tests should be carried out in a low temperature environment" (see 4.1 of ISO 17279-3:2021) to adapt to in response to my country's technical conditions;

e) The qualification requirements for visual inspection test personnel (see 5.2.2) have been changed to apply my country's technical requirements;

f) The reinforcement step for visual inspection of joint specimens (4.2.5 of ISO 17279-3:2021) has been deleted to adapt to my country's technical requirements;

g) Deleted the test principle of the four-lead method, the measurement content of the heat-affected zone, the strip recorder used, test steps b), and the Formula (2) and formula (3) (see 4.3.5.1 of ISO 17279-3:2021) are applicable to my country's technical conditions;

h) The temperature measuring instrument used in the four-lead method test [(see 5.3.5.1b)] and the temperature reached when the container is completely cooled [(see 5.3.5.1c)] to adapt to my country's technical conditions;

i) Deleted the data acquisition system and software used in the four-lead method for measuring self-field critical current (see ISO 17279-3:2021 4.3.5.2) to suit my country's technical conditions;

j) The four-lead method for measuring critical current density test (see 4.3.5.3 of ISO 17279-3:2021) has been deleted to adapt to my country's technology.

condition;

k) Deleted part of the expression of the transformation formula (5) of VI to normal state when measuring n-value by four-lead method, and changed the representation of n-value.

The meaning of ISO 17279-3:2021 is 4.3.5.4, so as to be applicable to my country's technical conditions;

l) The container for liquid nitrogen or refrigerant in the magnetic field attenuation test (see 5.4.5 and Figure D.2 in Appendix D) has been changed to suit my country's Technical conditions;

m) The general requirements for the applied magnetic field test (see 5.5.1) have been modified to suit my country's technical requirements;

n) The critical magnetic field test (see 4.8 of ISO 17279-3:2021) has been deleted to adapt to my country's technical requirements;

o) Scanning electron microscopy, transmission electron microscopy and X-ray diffraction tests (see ISO 17279-3:2021) have been deleted.

4.10) to suit my country's technical conditions.

The following editorial changes have been made to this document.

a) In order to comply with the requirements of my country's standard writing, the name of the standard is changed to "Second Generation High Temperature Superconductor Microconnections Part 3: Joints" Test Methods;

b) Deleted the redundant statements in the chapter (see 4.1, 4.2.3, 4.2.5, 4.3.5.2, 4.6.1, 4.7.1 and 4.9.5);

c) Deleted some notes (see 4.3.1 of ISO 17279-3:2021);

d) Deleted some explanatory descriptive content (4.3.5.1, 4.3.5.2, and 4.3.5.4 of ISO 17279-3:2021);

e) Added descriptions of the figures (see 5.7.5) and descriptions of the reference symbols in the figures (Figures 6, 7, 12, C.3, E.2 and G.2);

f) The results of the critical current density test in the report format have been deleted (see Annex B of ISO 17279-3:2021).

Record the results of scanning electron microscopy, transmission electron microscopy, and X-ray diffraction tests.

Results (see Annex I of ISO 17279-3:2021);

g) The critical magnetic field test report (see Annex G of ISO 17279-3:2021) has been deleted.

Introduction

With the widespread application of the second generation of high temperature superconductors (2GHTS) and the invention of 2GHTS resistance-free connection technology, it is necessary to this document has been developed to ensure that 2GHTS are connected in the most efficient way and that all implementation processes are properly controlled.

In order to achieve the best and uniform quality of 2GHTS joints, it is necessary to formulate national standards for micro-joining processes and joint evaluation specifications.

"Micro-connections of second-generation high-temperature superconductors" is a universal management standard for micro-connections of second-generation high-temperature superconductors, which is intended to consist of three parts.

--- Part 1: Process requirements;

--- Part 2: Qualification of welding and testing personnel;

--- Part 3: Test methods for joints.

Superconducting materials have zero resistance conduction and complete anti-magnetism below the critical temperature T, critical magnetic field strength Bc and critical current density Jc.

Once activated, current will flow forever in the diamagnetic closed loop of the superconducting material.

2GHTS consists of multiple layers with a total thickness of about 60µm~100µm, with or without copper stabilization layer coating.

The thickness of the superconducting layer prepared by (REBCO) is only 1µm~3µm, depending on the specifications of 2GHTS. Re represents rare earth materials, including

Figure 1 is a schematic diagram of the multilayer structure of a typical 2GHTS, and indicates the composition of each layer including the copper stabilization layer.

The two copper stabilization layers numbered 1 in FIG1 do not exist in the 2GHTS without stabilization layer.

Index number description.

1---20µm thick copper stabilization layer;

2---2µm thick silver protective layer;

3---1µm~3µm thick REBCO superconducting layer;

4-5 buffer layers (total thickness 160nm);

5-50µm thick Hastelloy alloy substrate.

Note. Not drawn to scale.

Figure 1 Schematic diagram of the multilayer structure of a typical 2GHTS

At present, the superconducting industry uses soft soldering (see Figure 2), brazing or other filling materials to connect joints.

High resistance at the head can create fatal defects in the superconductor.

a) Lap joint b) Bridge joint Index number description.

1---superconducting layer;

2---Soft solder.

Figure 2 Schematic diagram of 2GHTS soldering connection joint

This paper focuses on the direct self-bonding of 1 µm to 3 µm thick 2GHTS superconducting layers without the use of filler materials (see

3), and the superconducting properties were restored through oxidation annealing process, and the resistance at the joint was almost zero.

a) Lap joint b) Bridge joint Index number description.

1---Superconducting layer.

Figure 3 Schematic diagram of the direct self-connection joint between two superconducting layers of 2GHTS

GB/T 45982.1 specifies the process requirements for 2GHTS micro-connections. 2GHTS joints should have the required electrical, magnetic and mechanical properties.

To achieve this goal, it is necessary to control the design and manufacturing process.

GB/T 45982.2 specifies the qualification requirements for welding and testing personnel.

This document, as a test method standard for micro-joints of second-generation high-temperature superconductors, specifies eight joint test methods, process requirements, welding the joint evaluation method of superconductor is formed by matching the standards of joint and test personnel qualification, which also provides a theoretical basis for improving the quality of its products.

According to the report, it will further promote the application of my country's second-generation high-temperature superconductors and the demonstration application of related industries.

Second generation high temperature superconductor microconnection Part 3: Test methods for joints

1 Scope

This document specifies the test methods for second generation high temperature superconductor micro joints, including visual inspection, four-lead method test, magnetic field attenuation test, Test, external magnetic field test, tensile test, bending test, critical current density distribution test, optical microscopy test and other requirements.

This document applies to second-generation high-temperature superconductor micro-connector joints (hereinafter referred to as "joints").

2 Normative references

The contents of the following documents constitute the essential clauses of this document through normative references in this document.

For referenced documents without a date, only the version corresponding to that date applies to this document; for referenced documents without a date, the latest version (including all amendments) applies to this document.

GB/T 19866 Welding procedure specifications and general principles for their qualification (GB/T 19866-2005, ISO 15607:2003, IDT) GB/T 45982.1-2025 Second generation high temperature superconductors Microconnections Part 1: General requirements (ISO 17279-1:2018, MOD) Note. There is no technical difference between the referenced content of GB/T 45982.1-2025 and the referenced content of ISO 17279-1:2018.

3 Terms and Definitions

The terms and definitions defined in GB/T 19866 and GB/T 45982.1-2025 apply to this document.

4 Symbols and abbreviations

The following symbols apply to this document.

A1 --- cross-sectional area of the superconducting layer;

A2 --- Cross-sectional area of the lap joint;

Bc --- critical magnetic field strength;

B(t) ---magnetic field strength at time t;

B(t0)---initial magnetic field strength;

I --- the current between the two center leads;

Ic --- critical current;

Jc --- critical current density;

L --- the self-inductance of a closed loop;

n --- current power index;

R --- the average resistance between the two center leads;

Rj --- connector resistance;

rj --- resistivity of the joint;

T --- critical temperature;