GOST 21548-76

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  ГОСТ 21548-76

GOST 21548−76 Pike. Method for detection and determination of a layer thickness of a chemical compound (with Amendments No. 1, 2)

GOST 21548−76*

Group B09

INTERSTATE STANDARD

SOLDERING

Method for detection and determination of a layer thickness
chemical compounds

Brazing and soldering.
Method for detecting and determination of chemicals interlayer thickness

Date of introduction 1977−01−01

The decision of the State standards Committee of the Council of Ministers of the USSR from 05.02.76 N 346 date of introduction is established 01.01.77

The expiration time limit is removed by the Resolution of Gosstandart of the USSR from 15.08.91 N 1356

* REPRINT (January 2001) with Amendments No. 1, 2, approved in August 1981, April 1988 (IUS 10−81, 7−86)

DEVELOPED by all-Union scientific-research Institute for normalization in mechanical engineering (VNIINMASH)**

Acting Director, PhD. tech. Sciences N. Gerasimov

Supervisor, doctor of engineering. Sciences, Professor S. V. Lashko

Performers: candidate. tech. Sciences N. Sirchenko, V. M. Pichugin

The draft all-Union scientific-research Institute for normalization in mechanical engineering (VNIINMASH)**

Acting Director N. N. Gerasimov

APPROVED AND promulgated by the Decree of the State Committee of standards of Ministerial Council of the USSR of February 5, 1976 N 346**
________________
** Information cited from the official publication, Moscow: Publishing house of standards, 1976. — Note the manufacturer’s database.

This standard specifies the metallographic method for the detection and determination of a layer thickness of a chemical compound on the border of the brazed material, a brazed joint or a tin-plated layer.

Control of presence and a layer thickness of a chemical compound produced when selecting the solder and the material of the product select and change the mode of technological process of soldering and tinning and parameters of the solder joint, and also determining the activation period and speed of growth strata (see Annex 1).

(Changed edition, Rev. N 2).

1. SAMPLING

1.1. Sections for the detection and determination of a layer thickness of a chemical compound on the border of the brazed material, a brazed joint or a tin-plated layer made of tin-plated or soldered lap joint samples.

1.2. The number of samples for testing shall not be less than five for each mode and combination of materials and solder.

1.3. The shape and dimensions of specimens, brazed lap joint, shall be as specified in the hell.1.

Damn.1. The shape and dimensions of specimens, brazed lap joint

1 — base plate; 2 — upper plate; 3 — strip

Damn.1

The thickness of the lower and upper plates of the specimen — [(1,0…2,0)±0,1] mm.

When the thickness of the brazed material is more than 2.0 mm may be processed wafers to the desired thickness from the side, not be soldered.

Note. In the case of determination of a layer thickness of a chemical compound in the solder seam connecting the sintered hard alloy with the metal, the thickness of the plate 2 of hard metal — [(1,0…6,0)±0,1] mm.

1.4. To reproduce the conditions of tinning or soldering by immersion using the samples form and the dimensions of which should correspond to those on features.2.

Damn.2. Samples of the strip, pipe, wire

The sample from the strip

A sample from the pipe

The sample from the wire

[(0,5…2,0)±0,1] mm; [(0,5…2,0)±0,1] mm; [(0,5…2,0)±0,1] mm; [(2,0…10,0)±0,1] mm

Damn.2

For precious and rare metals allowed the use of smaller sample thickness while maintaining uniformity of the gap during soldering.

1.5. Samples should be cut in any way, not causing changes in their structure.

1.6. The samples marked by the batch number or the conditional index on a non-working part to the sample of wire attached tag for marking.

2. PREPARING FOR THE TEST

2.1. Preparing for the test specimen lap joint

2.1.1. The method of preparing the sample surface, the shape and placement of solder and the size of the gap is adjusted in accordance with technological process of manufacture of a brazed product.

In the absence of regulated surface preparation the choice of preparation method and surface roughness — the results of tests 20485−75 GOST, GOST 23904−79 and of this standard.

Note. When laying the solder gap should be placed at a lower side of the upper plate.

2.1.2. The gap () between the plates (Fig.1) you must install gaskets () — wire or strips.

It is allowed to set the gap by making a groove on one of the plates as specified in claim 1.5. The shape and size of groove shall be as specified in the hell.3.

Damn.3. The shape and dimensions of groove

Maximum deviation in size of±0.01 mm

Damn.3

2.1.3. The plate is fixed at a predetermined position by a clamp or other means.

2.1.4. The gasket material and the retaining device when soldering should not melt independently or in contact with the sample material or solder.

2.1.5. The volume of solder for the soldering of the samples overlap should be 150% of the volume of the gap.

2.1.6. Ration samples that are installed in a horizontal position, should be carried out in a gas atmosphere, vacuum or flux modes used in the respective processes.

2.1.7. For temperature measurement you should use thermocouples and instruments according to the GOST 7164−78.

2.1.8. The working end of the thermocouple should be fastened in the center of the outer surface of one of the plates (Fig.1) zachekanka, by spot welding or other method which provides reliable thermal contact with the sample.

The direct impact of the heat source for a thermocouple is not allowed.

2.2. Preparing to test samples from strip, tubing and wire

2.2.1. Surface preparation of the strip, tube and wire shall be as specified in clause 2.1.1.

2.2.2. The prepared strip, tube or wire must be immersed into the crucible with molten solder to a depth of not less than 20 mm. Lower end of the sample should not touch the bottom of the crucible. The volume of the solder must be not less than 6 cm.

Notes:

1. The crucible material must not significantly interact with the solder.

2. Each sample shall be immersed in a new batch of solder.

2.2.3. The tinning process should be carried out in a gas atmosphere, vacuum or submerged in the modes to be applied in the relevant technological processes.

2.2.4. Temperature measurement according to claim 2.1.7.

3. TESTING

3.1. For the manufacture of thin sections samples should be cut with a method specified in claim 1.5. The cutting plane is indicated on the devil.1 and 2.

3.2. A method of manufacturing thin sections not regulated.

3.3. The plane of the cone should be perpendicular to the solder or tin-plated surfaces of the sample. A blockage of edges is not allowed.

In the case of small thickness layers of chemical compounds, it is recommended to carry out measurements on oblique sections.

3.4. Identification of the structure of a brazed joint should be chemical, electrochemical, or other method, without causing changes in its structure and depending on the chemical composition of soldered material and solder. Reagents for chemical etching of thin sections are given in Annex 1 GOST 21549−76.

3.5. In the manufacture of thin sections and identification of their structure must not be damaged solder joints — spalling, burn-out or etching of its components.

3.6. The measurement of the thickness of the layer is performed under a metallographic microscope at a magnification of 300−500. May increase to 1000.

3.7. The thickness of the layer in the capillary area of the weld (zone II) and in the fillets (I and III zones) should be identified separately.

3.8. The measurement should be carried out in five evenly spaced along the length of the layer points of capillary is not less than three points the fillet of the solder joint.

Notes:

1. When a seam of multiple layers of chemical compounds to measure the thickness of each layer separately and the total thickness.

2. In the case of brazing dissimilar materials, the interlayer thickness should be measured at both boundaries of the seam.

3. On tin plate, pipe or wire for measuring the thickness of the interlayer is produced on the perimeter of the cross section at five points.

3.9. When the dendritic nature of growth layer measurement are subject to two variables: the thickness of the continuous layer and the height of the dendrites as shown in hell.4.

Damn.4. Measurement of the thickness of the continuous layer and the height of the dendrites

Damn.4

4. PROCESSING OF THE RESULTS

4.1. The thickness of the layer of chemical compounds should be measured in microns with an error of less than 1 micron.

4.2. The thickness of the layer is determined as the arithmetic mean of values determined for each sample.

4.3. The thickness of the layer should take the arithmetic mean of five measurements in the capillary area of the seam, three measurements in the weld throat. With variable-thickness layer at the weld seam should take its maximum value. When the dendritic structure of the layer should take the arithmetic mean of five measurements of the thickness of the continuous layer and the maximum value of the height measurements of the dendrites.

4.4. If the degree of dispersion of the test results of more than 20%, the failure of the thermocouple or detection Naropa more than 5% of the area of overlap tests must be repeated, the number of samples must match the number of invalid test results.

4.5. The test results of each sample should be made in the Protocol, the form of which is given in Appendix 2.

ANNEX 1 (reference). THE DEFINITION OF THE PERIOD OF ACTIVATION AND THE RATE OF GROWTH OF THE LAYER OF A CHEMICAL COMPOUND BY THE METHOD OF SUCCESSIVE APPROXIMATIONS

ANNEX 1
Reference

1. The definition of the period of activation

The soldering process the samples are in isothermal conditions, since the exposure time of the sample . If the exposure time at a given temperature stratum reveals the following pattern of solder exposure , etc. to where the layer is not detected. Then examine the samples after aging is equal , until it is determined the maximum time of contact with the brazed material with a liquid solder, wherein the layer is still not detected metallographically at a given magnification. The time taken for the activation period .

Conducting similar tests at different temperatures to determine the dependence of the activation temperature soldering

.

2. Determination of the rate of growth of the layer of a chemical compound

The process of soldering lead in isothermal conditions with exposures in excess of the activation period at a predetermined temperature. According to the data (at least five exposures) build the relationship «the thickness of the layer — time» .

Study of the growth layers depending on the temperature at a given shutter speed allows you to build the relationship «the thickness of the interlayer  — temperature », . Simultaneously with the samples intended for the determination of the rate of growth of the layer during soldering, in the same modes braze lap joint samples for determination of resistance to shear solder joints as the emergence and growth of the layer.

To change the resistance of the slice set allowable layer thickness for a given combination of brazed material is solder.

Example.

The definition of the period of activation and the rate of growth of the layer.

Type of sample — plate. Brazed material — copper M1. Solder: tin; tin +5% cadmium.

Preparation of the samples surface: sanding N 00, degreasing with alcohol, pickled in 5% strength solution of ammonium persulfate, rinsed in water, dried at 100 °C, fluxing.

Mode of soldering: preheating in an electric furnace to a temperature of 120 °C, immersion in a bath of solder, soldering temperature 250, 280, 300 °C, air cooling.

Metallographic analysis

The test results are shown in hell.1 and 2.

Damn.1. The dependence of the activation period of the formation layer from soldering temperature

The dependence of the activation period of the formation layer from soldering temperature

1 — solder the tin — cadmium; 2 — solder tin

Damn.1

Damn.2. The rate of growth of a chemical compound layer at different temperatures of soldering (solder tin)

The rate of growth of a chemical compound layer at different temperatures of the soldering
(solder tin)

1 — soldering temperature 250 °C; 2 — soldering temperature 280 °C; 3 — temperature of soldering 300 °C

Damn.2

ANNEX 2 (mandatory). PROTOCOL metallographic analysis of the brazed and tin-plated samples

ANNEX 2
Mandatory

1. Type of sample —

3. Brand or chemical composition of the solder

4. The temperature of the beginning and end of melting solder

5. Surface preparation of the sample:

a) method of removal of contaminants and oxides —

b) the roughness parameter of the working surface of the sample

6. Method of soldering:

a) the removal of the oxide film

b) to obtain a solder —

C) heat source —

(Changed edition, Rev. N 1).

7. Brand or chemical composition of the flux, gaseous environment, vacuum

8. The thermal cycle of the soldering:

9. Metallographic analysis:

a) measurement results of sample N ______

b) microstructure of the investigated areas:

I zone

II area

III area