GOST 1778-70

• gost-1778-70.pdf (1.07 MiB)
  ГОСТ 1778-70

GOST 1778−70 (ISO 4967−79) Metallographic methods of determination of nonmetallic inclusions (with Amendments No. 1, 2)

GOST 1778−70
(ISO 4967−79)

Group B09

INTERSTATE STANDARD

STEEL

Metallographic methods of determination of nonmetallic inclusions

Steel. Metallographic methods for the determination of nonmetallic inclusions

ISS 77.080.20
AXTU 0809

Date of introduction 1972−01−01

INFORMATION DATA

1. DEVELOPED by the Central research Institute of ferrous metallurgy them. I. P. Bardin (TSNIICHM)

Director of the Institute Golikov I. N.

Supervisor Kaplan A. S.

Responsible for implementing the Grapes M. I., L. Kolesnikova, R. I., Balakina I. A., Kiselev S. A., Piterova I. A., L. G. Polovnikova

2. INTRODUCED by the Ministry of ferrous metallurgy of the USSR

Zam. the Minister Borisov A. F.

3. PREPARED FOR APPROVAL by the metallurgy Department of the Committee of standards, measures and measuring devices under Council of Ministers of the USSR

Head of Department B. V. Fedin

Engineer R. A. Vasiliev

4. Department of metallurgy all-Union scientific research Institute of standardization (VNIIS)

Head of Department A. V. Stepanov

Ml. researcher Bushina E. G.

5. APPROVED by the Committee of standards, measures and measuring instruments under the USSR Council of Ministers on 28 September 1970 (report No. 190)

Chairman of the Scientific and technical Committee Deputy Chairman of the Committee Milovanov A. P.

Members of the Commission — Ushakov V. P., V. T. Tikhonov, Fedin B. V.

6. Promulgated by Decree of the State Committee of standards of Ministerial Council of the USSR from December 29, 1970, N 1832

7. Limitation of actions taken by Protocol No. 7−95 Interstate Council for standardization, Metrology and certification (ICS 11−95)

8. EDITION (June 2011) with Amendments No. 1, 2 approved in April 1984-September 1989 (IUS 8−84, 1−90)

REPLACE GOST 1778−62


This standard applies to steels and alloys and sets metallographic methods of determination of contamination of their non-metallic inclusions.

The standard fully complies ST SEV 4077−83 and ISO 4967−79*.
________________
* Access to international and foreign documents mentioned here and below, you can get a link on the website shop.cntd.ru. — Note the manufacturer’s database.

(Changed edition, Rev. N 2).

1. CLASSIFICATION

1.1. Non-metallic inclusions determine:

Method sh (SH1-Ш14) — comparison with the reference scales used to test the deformed metal;

method To (K1-K2) — counting the number of inclusions, is used to test the deformed and the cast metal;

method P (P1-P4) — count the number and volume percent of inclusions, is used to test the deformed and the cast metal;

method L (L1-L2): straight — line counting of inclusions; used for test casting.

1.2. Application methods and their options for testing metals, and of norms of contamination of steel and alloys, non-metallic inclusions are provided for in the standards and technical documentation approved in the established manner for specific products.

Recommendations on the selection methods specified in Appendix 1.

2. SAMPLING AND FABRICATION OF MICRO-SECTIONS

2.1. The number of samples for the determination of contamination of metal non-metallic inclusions is specified in the product standards and technical documentation approved in the established order, and must be a multiple of three and at least 6 from each heat. The number of samples depends on the required accuracy.

(Changed edition, Rev. N 1).

2.2. Samples from the deformed metal taken in the following order:

a) under the control of 6 sections — 6 bars, riots, tubes, sheets, strips;

b) when more than 6 sections 1, 2, 3, 4, etc. from each of 6 or more bars, riots, tubes, sheets, strips.

Notes:

1. By agreement of the parties can be installed in place of sampling from the bars at the height of the ingot. Samples of bars can be selected from one or more ingots during casting of metal.

2. Under the control of the deformed metal with a diameter or thickness greater than 150 mm allowed sampling from two bars.

3. In the control of drilled or designed for drilling a tube blank with a diameter of 600 mm and a wall thickness of not more than 250 mm samples taken from the two workpieces.

4. When control leaves a width exceeding 1000 mm samples taken from the two sheets.

2.3. Samples of deformed bars with diameter or thickness not more than 120 mm are cut from rods supplied and the samples are bars with diameter or thickness greater than 120 mm from samples reforged or perinatalnyj on the circle or square with a diameter or thickness of 80−120 mm.

Note. By agreement of the parties is permitted to cut samples from bars with diameter or thickness greater than 120 to 270 mm, a tube blank (or drill intended for drilling) with a diameter up to 600 mm, without turning or rolling.

2.4. Samples from cast metal are selected:

a) from one or more ingots or samples from the same melt;

b) for castings from one or more test bar cast from one or more cast billet samples or discontinuous from one trial privodnogo of the bar of this melting.

Trial bars and billets of cast discontinuous samples shall be established by relevant standards, and the location of the tidal bars of the trial — by agreement of the parties.

2.5. Samples of the deformed metal for the manufacture of sections with a longitudinal direction of the fibers cut:

a) of square and round profiles with a diameter or thickness up to 40 mm inclusive, through the center of the rod from end to end (damn.1),

1 — a cutting plane; 2 — the plane of the thin section.

Damn.1

b) square and round profiles with a diameter or thickness greater than 40 to 80 mm inclusive, from the center of the rod to the edge (Fig.2),

1 — a cutting plane; 2 — the plane of the cone

Damn.2

C) of square and round profiles with a diameter or thickness over 80 to 120 mm inclusive, from the center to ¼ of the diameter or thickness (Fig.3), or from the center to the edge (Fig.2),

1 — a cutting plane; 2 — the plane of the cone

Damn.3

g) of square and round profiles with a diameter or thickness greater than 120 mm at a distance of 1/6 diameter or thickness from the center and from the edge (Fig.4) so that the center of the cone coincides with the mid-radius or one quarter of the thickness

1 — a cutting plane; 2 — the plane of the cone

Damn.4

d) of the pipe throughout the wall thickness (Fig.5),

1 — a cutting plane; 2 — the plane of the cone

Damn.5

e) of the drill or designed for drilling a tube blank with a diameter of 600 mm, a wall thickness of up to 250 mm in accordance with the devil.6, and the size of each sample in the radial direction must compose 1/5 of the wall thickness of the workpiece,

1 — samples for testing; 2 — plane sections

Damn.6

g) from sheet and strip of thickness up to 40 mm inclusive, throughout the thickness (Fig.7a) and a thickness more than 40 mm to half the thickness (Fig.7b) from the middle of the sheets and strips by width.

1 — a cutting plane; 2 — the plane of the cone

Damn.7

The length of the sample is chosen so that the area of the cone was 400±50 mm.

Notes:

1. Slub-symmetrical profiles (triangular, hexagonal, rhombic, etc.) the samples cut according to the drawings or samples from a round sheet metal, and steel shaped profiles according to the drawings approved in the prescribed manner.

2. Allowed samples of great length to be cut before the production of thin sections in several parts, considering these parts in one socket, and at small length samples to gain the required area of several samples, counting them in one section.

3. Allowed control slim profile with a diameter or thickness less than 10 mm to produce the reduced area of the cone, but not less than 200±50 mm.

4. Allowed to inspect inclusions in thin sections with an area of 500±100 mm.

2.6. Samples of the deformed metal for the manufacture of sections with transverse fiber direction cut:

a) of square and round profiles with a diameter or thickness up to 20 mm in the transverse washers with a height of 15−20 mm (Fig.8),

Damn.8

b) square and round profiles with a diameter or thickness greater than 20 to 40 mm inclusive — from edge to edge of the rod through the center (Fig.9),

Damn.9

C) of square and round profiles with a diameter or thickness greater than 40 to 120 mm, inclusive, from the center to the edge of the rod (to hell.10),

Damn.10

g) of square and round profiles with a diameter or thickness greater than 120 to 270 mm inclusive, in accordance with the devil.11,

1 — samples for testing; 2 — plane sections

Damn.11

d) out of the stacks around the circular section of the pipe, half, quarter or part of it (hell.12−15),

Damn.12

Damn.13

Damn.14

Damn.15

e) of the drilled tube stock with a wall thickness of () up to 250 mm in the radial direction (Fig.16),

1 — samples for testing; 2 — plane sections

Damn.16

g) from sheet and strip of thickness up to 40 mm inclusive, throughout the thickness (Fig.17A), more than 40 mm to half the thickness of the middle sheet and strip in width (Fig.17B),

Damn.17

Square sections should be at least 200 mm.

Note. Allowed to make up the required area of several sections.

2.7. Samples must be cut out with an allowance for removal with the plane of the cone roughness after cutting and oxidation during heat treatment.

2.8. Samples for making thin sections of cast metal cut:

a) from the sample at a distance of 2/3 the height of the sample in the form of washers with a thickness of 10−15 mm (Fig.18),

1 — shaft; 2 — a cutting plane; 3 — the plane of the cone

Damn.18

b) from the ingot, three or more horizontal planes along the height of the ingot (a), and three cross sections (at the edge, middle and center of the ingot), or the entire section from edge to the axis of the ingot (Fig.19, 20).

Damn.19

Damn.20

C) petals of the clubs — through the center from edge to edge of the petal (Fig.21),

1 — a cutting plane; 2 — the plane of the cone

Damn.21

g) of the wedge sample on a diametrical plane from edge to edge (Fig.22),

1 — a cutting plane; 2 — the plane of the cone

Damn.22

d) of blanks for discontinuous samples in accordance with the devil.23.

1 — a cutting plane; 2 — the plane of the cone

Damn.23

2.9. Samples should be cut cold by mechanical means or any other method that does not modify the structure of the metal.

2.10. On cut samples produce sections on the planes indicated by the hatching in hell.1−23.

It is possible to manufacture thin sections in two mutually perpendicular planes of the specimen cut in the form of a quarter circle or square. Each plane section is considered a separate sample.

2.11. Allowed samples before the production of thin sections to increase the hardness of heat treated.

The heat treatment must be specified in the relevant standards or technical documentation approved in the established order.

After the heat treatment on the abrasive wheel or other means removes a layer of metal, equal to the allowance.

3. TEST METHODS

3.1. Method W

3.1.1. Evaluation of non-metallic inclusions of deformed metal with a diameter or thickness not less than 6 mm produced under the microscope by comparing with the reference scales when viewing the entire area netravlenoy sections with a longitudinal direction of the fibers.

Notes:

1. The pollution of deformed metal with a diameter or thickness less than 6 mm method ø determine the interim profile or the workpiece.

2. (Deleted, Rev. N 1).

3.1.2. A five-point scale klassificeret the following types of non-metallic inclusions (see insert*):
_______________
* In the original paper (edition of M.: STANDARTINFORM, 2011) inserts missing. Electronic inserts are given from the official publication, Moscow: standards Publishing house, 1971. — Note the manufacturer’s database.

Scale can be estimated and other types of inclusions, if they are in size, shape and location correspond to the given poliatlonu.

Description of certain types of inclusions is given in Appendix 2.

The types of inclusions to be estimated is specified in the product standards or technical documentation approved in the established order.

If the inclusion shape and size could not be assessed in one of two adjacent points allowed rating 0,5; 1,5; 2,5 points etc.

The inclusion of the above points 5 5 evaluated score with the sign «more» (>5).

A rating of «zero» is placed in the absence of any kind of inclusions as well as inclusions in more than 2 times less in comparison with point 1.

3.1.3. If in the same field of view there are several types of inclusions, the assessment is made for each type of inclusions separately.

The exceptions are cases when in the same field of view meet:

a) stroke the inclusion of oxides, fragile silicates plastic and nitrides;

b) point to the inclusion of oxides and nitrides.

In either case the assessment is made collectively, and the results of the evaluation are recorded in the column of the dominant types of inclusions.

Notes:

1. By agreement of the parties allowed the assessment of stroke inclusions the maximum of the scores obtained in the evaluation of stroke oxides, fragile silicates and plastic.

2. In the evaluation of contamination of metal particles stroke nitrides and carbonitrides individual point of inclusion is not taken into account.

3.1.4. Variants of the method ø to assess the contamination of the ground and smelting of non-metallic inclusions are given in table.1.

Table 1

Notes:

1. In the methods of SH1; ø2; ø3; Ш7; Ш9; Ш10; Ш13 the diameter of the field of view of the microscope corresponds to the diameter of fotoatele (80 mm) divided by magnification.

2. When calculating the average score, score more than 5 shall be equal to 5.

3. In the methods Ш7; sh8; Ш13 and Ш14 allowed to estimate cone number of fields of view to points 1, 2, 3, 4, 5 and more than 5. Evaluation criterion of melting is the number of fields of view with points 1, 2, 3, 4, 5 and more than 5 separately for oxygen, sulfide, and nitride inclusions, assigned to the area of 10 cm.


The results of the assessment sections and melting recorded in accordance with annexes 3 and 4.

3.1.5. The data of pollution control smelting, non-metallic inclusions of the first definition may differ from the results of the second determining the magnitude of the error depending on the degree of contamination of the metal and the number of samples taken for control.

The limiting error in determining the average score of inclusions and formulas of their calculation are given in Appendix 5.

3.2. Method To

3.2.1. Counting the number of inclusions having a size greater than the set, produced under the microscope on thin sections netravlenoy.

To assess the contamination of the deformed metal used sections with a longitudinal direction of the fiber.

3.2.2. The entire area of the viewing cone at 170−180 magnification and the price of division of the ocular scale 0,007±0,0005 mm. Separately determine the amount of oxygen, sulfide, and nitride inclusions in groups:

Group 1 — inclusion of more than 1 to 2 divisions of the ocular scale, inclusive;

Group 2 — inclusion of more than 1* to 3 divisions of the ocular scale, inclusive;
________________
* The text of the document matches the original. — Note the manufacturer’s database.

Group 3 — inclusion of more than 3 to 4 divisions of the ocular scale, inclusive;

Group 4 — enable over 4 to 5 divisions of the ocular scale, inclusive;

Group 5 — the inclusion of more than 5 to 6 divisions of the ocular scale, inclusive.

The number of groups may be increased depending on the maximum size of inclusions in the metal. Using ocular scale measure the diameter or thickness of the inclusions, respectively, in the form of a circle or square, or minimum and maximum sizes of inclusions of other shapes. If the ratio of the maximum and minimum sizes of the inclusions does not exceed two, the size of the inclusion is defined as their arithmetic mean. The dimensions of elongated inclusions (with a ratio of length to thickness of more than two) determine if their thickness is not less than ¼ division of the ocular scale. The average linear size of an inclusion () is calculated according to the formula:

,

where and  — the measured values respectively the thickness and length of inclusions.

The type of inclusions to be evaluated, specify in the standards or technical documentation for the products duly approved.

3.2.3. Variants of the method for evaluation of thin sections and melting given in table.2.

Table 2

______________
* The area of the six micro-sections on the basis that the area of each cone is 4 cm.


The results of counting the number of inclusions at microsections and smelting recorded in accordance with Annex 6.

Notes:

1. Allowed to rate inclusion in a deformed metal thickness or diameter less than 6 mm square 6 cmon melting.

2. Allowed to rate inclusion in the area of 12 cmfor smelting, if one cone is determined more than 75 inclusions of the 1st group.

3.2.4. The first definition of inclusions of different groups may be different from the evaluation of the second determining the magnitude of the error which depends on the degree of contamination of the metal and the number of samples taken for control.

An example of counting the errors of determination of non-metallic inclusions is given in Annex 7.

3.3. Method P

3.3.1. The inclusion of a certain size are counted under the microscope on thin sections netravlenoy.

To evaluate the deformed metal used sections with transverse fiber direction. Allowed the use of thin sections with a longitudinal direction of the fibers.

3.3.2. The size of the inclusions in the thin sections is determined using the ocular scale by group given in table.3.

Table 3

Note. The group is built on the principle of increasing the area of the inclusions in the geometric progression with denominator 2.

3.3.3. Variants of the method P for assessment of contamination of ground and melting the non-metallic inclusions are given in table.4.

Table 4

Note. In parentheses are the limits of applicable gains.

3.3.4. In each field of view determines the size of all or some types of inclusions depending on the objectives of the study.

3.3.5. Before viewing cone line from edge to center in 5 equal zones (Fig.24). The set of fields of view in the zones on each socket produced in accordance with the requirements of table.5.

Damn.24

Table 5

In each zone of the cone field of vision you score straight lines on the cone perpendicular to the axis of the ingot or rolled.

To improve the accuracy of estimation of the contamination of thin sections the number of fields of view in the zones can be accordingly increased by 2, 3, 4, etc. times.

3.3.6. The size of inclusions, consider the diameter or side of square, respectively, in round or square shape inclusions.

In determining the amount of inclusions, oval or irregular shapes calculate the arithmetic mean of the minimum and maximum size, assuming this size for the diameter of the inclusion.

In determining the amount of inclusions, rectangular, rhombic or similar forms calculate the arithmetic mean of the minimum and maximum size, assuming this size for the side of the square. If the difference between the maximum and minimum sizes of inclusions in more than 2 times the group is determined by the area of inclusion. The total area of the inclusions of complex shape can define the summation of the squares of the individual sections.

3.3.7. Enable record groups listed in table.3.

The measurement of inclusions recorded in accordance with Annex 8.

3.3.8. To calculate the area occupied by the inclusions on a polished section, the number of inclusions of each group is multiplied by the average value of the square of inclusions of this group and obtained the works of all groups are summed.

The average size of the inclusions () in the same field of view calculated by the formula:

,

where  — the total area of inclusions;

 — the number of fields of view.

3.3.9. The content of the inclusions () volume percent calculated by the formula:

,

where  — coefficient;

 — the area of the field of view on the cone with the prescribed increase of divisions of the ocular scale in the square;

 — diameter of field of view in the divisions of the ocular scale, determined by dividing the diameter of the field of view in mm measured with object micrometer on the price of division of the ocular scale of the microscope;

, and  — constant values for a given microscope magnification.

3.3.10. The content of nonmetallic inclusions volume percent melting count as definitions arithmetic mean of all samples.

3.3.11. Calculation of volume percentage to produce with accuracy to 0.0001.

Volume percent and the number of inclusions on an area of 100 mmare counted in accordance with annexes 8 and 9.

3.3.12. The first definition of inclusions may differ from the evaluation of the second determining the magnitude of the error which depends on the degree of contamination of the metal and the number of fields of view taken at melting for the study.

Example of calculation error when determining the inclusions volume percent is given in Appendix 10.

3.4. Method L

3.4.1. Assessment of contamination of steel produced with inclusions under the microscope at netravlenoy sections.

Variants of the method L evaluation of pollution in smelting, non-metallic inclusions are given in table.6.

Table 6

Note. In parentheses are the limits of applicable gains.

3.4.2. Cone draw parallel lines in any direction so that the selected length for the counting was at least 3 cm and covered the peripheral and Central zone of the cast samples.

3.4.3. Move the cone with the micrometer screws of the stage of the microscope in one direction along the marked lines. Measure the maximum dimensions of the inclusions (see the devil.25), falling into the crosshairs of the threads of the eyepiece, and record them in accordance with groups listed in the table.7.

Damn.25

Table 7

3.4.4. Contamination of sections assessed separately by an oxygen, sulfide, and nitride inclusions or collectively in all types of inclusions.

The type of inclusions to be evaluated depends on the objectives of the study.

3.4.5. Pollution particles melting () is calculated according to the formula:

,

where the price of division of the ocular scale for a given increase in thickness.

 — the average value of the sizes of the inclusions in the divisions of the ocular scale;

the number of inclusions in the group;

 — length counting in microns.

Example of calculation of pollution are given in Appendix 11.

3.4.6. The first definition of contamination may differ from the evaluation of the second determining the magnitude of the error which depends on the degree of contamination of the metal and the total length calculation for smelting.

The ultimate error in the determination of impurity inclusions is given in Appendix 12.

ANNEX 1 (recommended). Methods of determination of contamination of non-metallic inclusions of metals of different production methods and groups of steel

ANNEX 1
Recommended

Note. Methods P1, P2, P3, P4 can be applied to the research tests the metal melted in open-hearth electric arc furnaces and converters. In this case, the number of viewable fields of view must be increased by 3 times or more.

The scale of non-metallic inclusions

ANNEX 2 (informative). Characteristics of the types of non-metallic inclusions

ANNEX 2
Reference

1. The oxides are:

the inclusion of separate small grains, often of corundum and spinel, are arranged in lines;

point include mainly simple and compound crystals of oxides in the form of individual particles or of disparate groups scattered throughout the plane of the thin section.

2. The silicates include:

destroyed by a deformation in solid lines fragile silicates or silicate glass, sometimes with inclusions of oxides;

plastically-deformed inclusions of silicates or silicate glasses, elongated in the direction of the fibers different from sulphides darker in color and transparency in a dark field of view;

non-deformable (globular) or an isolated group of rounded or irregular shaped inclusions of silicates and silicate glasses, the coarse particles of oxide inclusions, often corundum.

Inclusions are listed in the PP.1, 2 are assigned to oxygen inclusions.

3. The sulphides are plastic, opaque, a dark field of view, elongated in the direction of the fibers of the individual inclusions or groups of inclusions, as a rule, a double sulphide of iron and manganese.

4. The nitrides include:

lines and dispersed across the field of view yellow-pink crystals of nitrides and carbonitrides of titanium, mainly of the correct form;

lines and dispersed across the field of view of pale pink inclusions of nitrides and carbonitrides of niobium and irregular rounded shape;

dark crystals of nitrides of aluminium, mostly regular shape, anisotropic.

APPENDIX 3 (reference). Example of recording the results of the evaluation of contamination of the melting particles. Methods SH1-Ш6, Ш9-Ш12

APPENDIX 3
Reference

________________
* The column is filled, if by agreement of the parties allowed the assessment of stroke inclusions the maximum of the scores obtained in the evaluation of stroke oxides, fragile silicates and plastic.


The number of samples with a score above the maximum () to the percentage determined by the formula:

,

where is the number of samples with a score above the maximum;

the number of samples.

Example of calculation for silicate that does not deform when the prescribed maximum score of 3.0:

.

ANNEX 4 (reference). Examples of the record of the evaluation of the contamination of the melting particles. Methods Ш7 and sh8, Ш13 and Ш14

ANNEX 4
Reference

Continued

The number of fields of view, with oxygen inclusions score 2 or more in the area of 10 cmis equal to .

The number of fields of view with sulfide inclusions score 2 or more in the area of 10 cmis equal to .

The number of fields of view with nitride inclusions score 2 or more in the area of 10 cmis equal to .

ANNEX 5 (reference). Example of calculation of limit of error in determining the average score of non-metallic inclusions by the method of W

ANNEX 5
Reference

An average melting () is calculated according to the formula:

,

where  — the sum of the maximum scores of all samples;

 — the number of samples.

Limit error () when determining the average score is calculated by the formula:

,

where is the standard deviation calculated from the distribution of estimates at least 200 samples;

A 1.65 — constant multiplier for the probability of 0.9;

 — the number of samples.

APPENDIX 6 (reference). An example entry results in the evaluation of metal melting method K1

APPENDIX 6
Reference

APPENDIX 7 (reference). An example of counting the errors of determination of non-metallic inclusions of the 1st group method K1

ANNEX 7
Reference

The arithmetic mean of the number of inclusions () in a single sample calculated by the formula:

,

where is the total number of inclusions in the group;

 — the number of samples.

Error () when the counting of inclusions is calculated by the formula:

,

where  — the average quadratic deviation:

,

where the sum of the squared deviations from the mean value of the number of inclusions.

. .

.

ANNEX 8 (informative). An example of the recording and counting of the results of the evaluation of oxides on the microscope MIM-8, with 280-fold increase

ANNEX 8
Reference

_____________
* Counts for the fields of view of 11…125 is filled similarly.

.

.

.

ANNEX 9 (reference). An example of counting the number of oxides in thin section with an area of 100 sq mm

ANNEX 9
Reference

An example of counting the number of oxides in thin section with an area of 100 mm

Notes:

1. For calculation used the data of the application 8.

2. The area of the viewed field of view (21,625) is equal to the area of one field of view (0,173 mm) multiplied by the number of viewed fields of view (125).

3. For the number of inclusions in the melt should be the arithmetic mean of the assessments of the individual samples on an area of 100 mm.

APPENDIX 10 (reference). An example of counting errors in the determination of oxide inclusions volume percent method P

ANNEX 10
Reference

The average number of inclusions () volume percent calculated by the formula:

,

 — the total content of inclusions in vol.%;

 — the number of samples.

Error () when calculating the content of the inclusions volume percent calculated by the formula:

,

where  — the average quadratic deviation;

,

where the sum of the squared deviations from the mean value of the number of inclusions in vol.%.

.

.

.

The relative error is equal to

.

APPENDIX 11 (reference). Example of calculation of pollution melting steel 35L with the method of L

ANNEX 11
Reference

________________

* Marriage of the original. — Note the manufacturer’s database.

= 180000 microns.

= 4 µm.

An increase of 300.

.

.

.

.

APPENDIX 12 (reference). Example of calculation of limit of error in the determination of non-metallic inclusions by the method of L depending on the selected length for the counting

ANNEX 12
Reference

Limit error () of contamination is calculated by the formula:

,

where  — the average quadratic deviation of the distribution at 25 cm of length count;

A 1.65 — constant multiplier for the probability of 0.9;

 — selected length for the counting to see