GOST 26388-84

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  ГОСТ 26388-84

GOST 26388−84 welded Connections. Test methods on resistance to cold cracking in fusion welding

GOST 26388−84

Group B09

STATE STANDARD OF THE USSR

WELDED CONNECTIONS

Test methods for resistance to education
cold cracking in fusion welding

Welded joints. Test methods on resistance to cold crack formation
under fusion welding

AXTU 0909

Valid from 01.01.86
to 01.01.91*
__________________________________
* Decree Of Gosstandart Of Russia
from 14.10.99 344-St standard
in Russia restored
with 01.03.2000 (IUS N 1, 2000). -
Note the manufacturer’s database.

DEVELOPED by the Ministry of higher and secondary special education of the USSR

PERFORMERS

G. A. Nikolaev, Yu.N.Sugars, E. L. Makarov, Yu. G. Novels

INTRODUCED by the Ministry of higher and secondary special education of the USSR

Member Of The Board Of D. I. Ryzhonkov

APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on standards of 20 December 1984 N 4829


The standard establishes test methods for resistance of carbon and alloy steel base metal in the heat affected zone and weld metal cold cracking in single pass welding (including the welding of root crown layered seams).

Machine method is based on bringing the metal heat affected zone or weld metal of welded samples to the formation of cold cracks under the action of tensile stresses from the external constant load.

Technological method consists in bringing the metal heat affected zone or weld metal of welded samples to cold cracking under the effect of residual welding stresses.

Native method is used with differences in the assessment of the quality of welded joints.

Test methods specified by this standard, is used for conducting research trials on the evaluation of the weldability of metals.

1. SAMPLING METHODS

1.1. For native test set five types of basic designs:

I flat to round or octagonal steel with a thickness of 1−6 mm (Fig.1 table.1) to quantify resistance of butt joints to formation of longitudinal and transverse (relative to the axis of the weld) cracks in the weld and the heat affected zone. The axis of the seam are located along or across the direction of rolling;

II — t-for steel with a thickness of 8−20 mm (Fig.2 table.2) to quantify resistance of corner joints the formation of longitudinal cracks in the heat affected zone along the plane rolled and at the root of the weld;

III — for flat rectangular steel with a thickness of 8−20 mm (Fig.Table 3.3) to quantify resistance of butt joints to the formation of longitudinal cracks in the heat affected zone across the plane rolled and the seam;

IV — a flat rectangular steel with a thickness of 8−20 mm (Fig.4 PL.4) to quantify the resilience of butt joints of the formation of transverse cracks in the heat affected zone across the plane rolled and the seam;

V — cylindrical, with a diameter of 8 mm with a spiral cut (Fig.5) to quantify resistance of butt joints made from steels with strength up to 1000 MPa the formation of longitudinal cracks in the heat affected zone across the plane rolled in the presence of sharp stress concentrators. Allowed to use samples with a diameter of 6 mm.

Damn.1. Type I

Type I

 — splice without cutting edges; b — splice groove;
in — a General view of the welded joint;  — the thickness of the sample; the diameter of the sample;
 — the size between the octahedral faces of the sample;  — the angle of cutting the sample;
 — groove depth; the diameter of the working part of the specimen

Damn.1

Table 1

Dimensions, mm

Damn.2. Type II

Type II

 — the length of the vertical walls of the specimen; the thickness of the input and output plates;
 — the wall height of the specimen; width of the base of the sample;  — the length of shelves of the sample;
the size of the gap;  — side weld bead; 1 — a wall of tested steel;
2 — shelf mild steel; 3 — input and output of smelting of low carbon steel

Damn.2

Table 2

mm

Note. It is possible to manufacture shelves and strips of steels with the same alloying system, and test the steel with a smaller content of carbon, manganese and chromium.

Damn.3. Type III

Type III

 — the sample under a butt joint; b — General view of the welded joint; 1 — sample test
steel; 2 — input and output strips of low carbon steel; the width of the specimen; is the length
sample;  — the length of the working part of the specimen in tension;  — the length of the working part of the specimen
bending;  — the width of the bottom cutting edges;  — the width of the input and output plates;
 — the length of the input and output plates; is the height of the weld;
 — distance between the supports of the punch bending (see the devil.14in)

Damn.3

Table 3

mm

Damn.4. Type IV

Type IV

 — length of cutting sample

Damn.4

Table 4

mm

Note. When submerged arc welding is used, the upper limit of the length of the cutting edges of the sample and the lower limit of the depth of groove.

Damn.5. Type V

Type V

Notes:

1. It is possible to produce plates of steel of the same alloying system, and steel for the manufacture of a cylindrical sample with a smaller content of carbon, manganese and chromium.

2. Allowed the use of plates other dimensions, if provided the same cooling rate while maintaining a given mode of welding.

Damn.5

1.2. For testing using the technological procedure establish four types of basic designs:

VI — a flat square of steel with a thickness of 1−6 mm with a disc-shaped varichem in the center with a variable diameter (Fig.6 table.5) to quantify the propensity of joints to the formation of longitudinal and transverse cracks in the heat affected zone and the weld;

VII — cross pattern, assembled from three flat rectangular elements made of steel with thickness of 8−40 mm (Fig.Table 7.6) for quality assessment of the propensity of corner joints to the formation of longitudinal cracks in the heat affected zone and the weld;

VIII — three flat rectangular test specimen with a thickness of 12−40 mm, which differ in length of the welded elements (Fig.8 table.7) to quantify the propensity of joints to the formation of longitudinal cracks in the heat affected zone and the weld;

IX — a flat square with a thickness of 12−40 mm with a longitudinal slot in the center, decorated in the form of a U-shaped cutting line (Fig.9 table.8) to qualitatively assess the tendency of welded joints to the formation of longitudinal cracks in the heat affected zone and weld. The use of the sample is limited to tests for manual and semiautomatic welding.

Damn.6. Type VI

Type VI

 — the sample without cutting edges; b — sample groove; in — General view of the welded joint;  — AC the diameter of the working part of the sample;  — dulling of cutting edges;  — the weld reinforcement on the outside;  — the weld reinforcement at the root

Damn.6

Table 5

Dimensions, mm

Damn.7. Type VII

Type VII

1, 2, 3, 4 — sequence of welds on the sample;  — the length of the weld;
 — the width of the horizontal shelves of the sample;  — the length of the weld cut out for research

Damn.7

Table 6

mm

Damn.8. Type VIII

Type VIII

 — variable distance between the plates-trailer;  — a variable length sample

Damn.8

Table 7

mm

Notes:

1. In automatic welding under flux at thickness 12, 16, 20 mm using input and output trims with a length of 55−60 mm and a length of 70−80 mm at thickness 30, 40 mm.

2. Allowed welding of the plates trailing edges of the corner seams without cutting edges. In this case, the length of the main plates are increased by 2.

Damn.9. Type IX

Type IX

Damn.9

Table 8

mm

1.3. Samples cut from the test steel by mechanical means or by thermal cutting. In the latter case, the welding edges of the samples treated by mechanical means to a depth greater than the width of the heat affected zone from the cutting. Cutting edges (weld) test specimens are equally oriented along or across the direction of rolling and noted in the test report. The axis of the sample, the type V must be located in the middle of the sheet thickness if the thickness is less than 25 mm, and in one quarter of the thickness, if it is more than 25 mm.

1.4. Samples are marked on the front surface at the locations indicated on the devil.1−9, the direction of rolling by a combination of one or more letters indicating the cipher brand, smelting, and initial condition of the steel, and digits indicating the sequential sample number in a series.

1.5. Of the workpiece, the thickness of which differs from the standard, adjusted to the nearest standard thickness by machining. While the control suture is on the surface of samples not subjected to mechanical processing.

1.6. For the manufacture of the samples used for welding sheets and blanks in the state of delivery.

1.7. Edge samples to be welding, and the surface of the samples, when welding in contact with the heat-removing elements clamping devices, for removing rust, scale and lapping smooth sand around N 16−24 grit or metal blowing sand.

2. EQUIPMENT

2.1. Testing machines for tensile, compression and transverse bending, with a special device for long-term maintenance of a given load according to GOST and GOST 15533−80 7855−74, and other machines that meet the requirements:

the smoothness of loading;

the average loading rate during the test until the specified load should not be more than 10 MPa/s;

the load must be kept constant during the entire test period of 20 h;

fluctuations in the value of the constant load during the test period must not be more than ±5% from its nominal value.

2.2. Scheme of arrangements for holding the sample and loading of test machines given in the informational Appendix 1.

Scheme of clamping the heat sink devices shown in hell.10−13 and table.9−11.

Damn.10

1 — sample; 2 — sample position type VI

Damn.10

Table 9

mm

 — the thickness of the base fixture;

 — the width of the fixture;

 — the thickness of the clamp;

 — the length of the fixture;

 — the distance between the cooling channels;

, is the distance between the holes for clamping bolts.

Damn.11

1 — sample; 2 — the position of the sample type I; 3 — position sample type III; 4 — the position of the sample type IV

Damn.11

Damn.12

1 — example of type II; 2 — holes for water flow

Damn.12

Damn.13

 — thickness of the fixture;  — the width of the groove in the fixture

Note. Trailing edges with welded corner seams without cutting edges, the grooves of the fixture have respective seams bevels.

Damn.13

Table 10

mm

Table 11

mm

3. PREPARATION FOR TESTING

3.1. Welding of the samples is carried out in a laboratory room in terms of the stationary ambient air at a temperature of (20±10) °C in accordance with table.12. For selecting the optimal heat input in welding of steel investigated possible variation in the specific welding heat input and preheating temperature. For welding of the investigated steels use standard welding materials. In case of typical welding consumables for steels has not yet been developed to apply low-carbon welding materials based on wire SV-08 (manual welding and automatic submerged arc) and SV-08G2S (carbon dioxide welding).

Table 12

Modes of welding samples

Notes:

1. Weld samples adjusted to obtain the specified size of the weld depending on welding materials and welding equipment.

2. Mode welding in argon is shown for the case of melting of the tungsten electrode of the whole sample, the joint without cutting a zero clearance insert and a wire laid in a cutting.

3. Samples of types I, IV and V weld with full penetration.

4. The samples of a type III weld with incomplete filling of the cutting edges with the penetration of the weld metal by 1.0 mm below the surface of the base metal.

5. Samples of the types VIII and IX are welded with the obligatory incomplete fusion at the root of the weld.

6. The parameters of the welding conditions given in parentheses, refer to the argon-arc welding.

3.2. Samples, except for types V, VII and IX prior to welding is fixed in the clamping devices.

The necessary heat during the welding is achieved by using water cooled copper substrates when the water flow rate of 2 DM/min Sample type II are welded in position «in the boat». Welded specimens except types VIII, released from the clamping fixtures after cooling to 150 °C. a Set of three elements are samples of the type VIII are welded simultaneously in a single pass. Samples of types V, VII and IX weld in a free state. Specimens of type V are harvested from the primary plate «flush». A sample of the type VII are welded in position «in the boat». Sutures are placed in the sequence 1−4, following the same given initial temperature. In samples of type III after welding sand around and remove tacking, fixing the input and output bars.

3.3. After welding, each specimen clamping fixture is cooled to room temperature. The surface of the heat dissipating elements are cleaned with sandpaper to eliminate scale and other impurities caused by welding.

3.4. Welding materials are prepared according to normative-technical documentation of a welded joint. In the absence of such documentation, the electrodes coated basic type fluxes and calcined at 200 °C for 2 h and electrodes with gas-protective coating is at a temperature of 80 °C for 1 h and used for welding over the next 3−4 h Humidity shielding gases shall conform to the requirements of GOST and GOST 10157−79 8050−76*. Simultaneously with the welding of the test specimen determine the content of diffusion hydrogen in the weld metal in accordance with GOST 23338−78*. Allowed the determination of hydrogen content by using chromatographic method, alcohol or glycerin samples.
______________
* On the territory of the Russian Federation there are GOST 8050−85, GOST 23338−91, respectively. — Note the manufacturer’s database.

3.5. Test subject specimens in welded connections which visual inspection is not detected defects in the form of a fistula, incomplete penetration (except for the samples of types II, VII-IX), undercuts and cracks.

4. TESTING

4.1. Machine test

4.1.1. After welding the samples in the cooling process in the temperature range of 150−100 °C load constant gain. Allowed to start loading the samples at 50 °C if the test is only the minimum destructive voltage. The temperature of the sample is measured contact chromel-alumaloy thermocouple. Samples of type I is rigidly fixed along the contour and is loaded by uniformly distributed bending load (Fig.14). The samples of a type II load by cantilever bending (Fig.14b). Samples of types III and IV loaded by transversal bending (Fig.14in and 14g) axial stretching (Fig.14d). Samples of type V is loaded by axial stretching (Fig.14e).

Damn.14

Damn.14

4.1.2. Load application to samples produced statically with loading rates of 5−10 MPa/s, under a load the samples incubated 20 h

4.1.3. Experience 30 samples of the same type a different value of loads and set the minimum load at which the samples are formed cold cracks.

4.1.4. Use the following sequence of loads in the test samples. The first three samples tested at the stress equal to 0.5of the base metal. Further testing performed by groups of three samples when reducing or increasing the voltage sequentially 0.25, 0,15, of 0.10in accordance with the presence or absence of cracks in the samples. In the event of cracks in part of the specimens tested at the same voltage, no further test conduct, reducing the voltage to 50, then to 25 MPa, while continuing tests to establish . The minimum-breaking load is determined according to test results of three samples.

4.2. Technological tests

4.2.1. Technological tests are performed when the impossibility of carrying out machine tests.

4.2.2. After welding, the samples aged at normal temperature for 20 h. Samples of the type VIII is kept in the jig. Experience 3−5 samples of the same type.

4.3. The formation of cold cracks in the samples during the tests detected by periodic visual inspection of the weld and heat affected zone with the help of a magnifying glass with magnification 3. In the formation of visually observable cracks or complete fracture of the test specimen is stopped. Produced by Dol of the sample cross section, in which you’ll crack.

The plots on the failure surface with a shiny brittle fracture, klassificeret as cold.

4.4. Cold cracks in the samples, except types V and VII, nerazrushaushsii when tested and has no visually observed cracks, is detected using nondestructive methods (GOST 4782−76), the oxidative heat treatment or by etching the surface and root of the weld and the adjacent heat affected zone of a 5% aqueous solution of nitric acid. After drying, the samples are destroyed. If necessary, the connecting seams are cut by mechanical or thermal cutting. The etched part of the fracture, detected by visual inspection using magnifier with magnification 3, take for formed when tested cold cracks. Samples, the fracture of which have defects in the form of lack of penetration (with the exception of samples of types II, VII-IX), poor fusion, hot cracking and porosity of marriage, and the result of testing void. Cold cracks in the samples of types V and VII, not destroyed during the test and has no visually observed cracks, is detected using nondestructive testing or metallographic examination of the polished sections at magnification 100. Metallographic examinations for samples of the type of V is performed on longitudinal microsections, the plane containing the axis of the sample-inserts, for samples of type VII — two or three transverse sections, cut from the control welded joints (Fig.7).

5. PROCESSING OF THE RESULTS

5.1. Stress (MPa) in specimens subjected to engine testing are calculated by the formulas:

in samples of type I

,

where the maximum longitudinal and lateral tensile stresses in the centre of the specimen on its surface, MPa;

 — the diameter of the zone of the sample to be tested, m;

 — the thickness of the base metal, m;

 — the intensity of the distributed load, MPa;

 — modulus of elasticity low carbon steel 21,8·10MPa;

in samples of type II

,

where is the maximum transverse tensile stresses in the heat affected zone of the specimen wall and the root of the seam, MPa;

 — the nominal bending moment, MPa;

 — length of specimen, m;

 — the average height of fillet weld leg on the wall of the t-sample, obtained by five measurements along a seam, m;

samples of types III and IV, the test curve

,

where  — the maximum tensile stress on the surface of a sample, MPa;

 — coefficient taking into account the uneven stress distribution over the cross section of 0.65;

 — the thickness of the base metal, m;

 — distance between the supports on the bottom, m;

 — distance between the supports on the plug, m;

 — deflection in the center of the sample on the basis of , m;

 — the residual deflection in the center of the sample on the basis of , after removal of the load, m;

 — modulus of elasticity low carbon steel 21,8·10MPa;

samples of types III and IV, the test axial tension, and type V

,

where is the average tensile stress in the heat affected zone and in the cross section of notched specimens of type V without taking into account stress concentration, MPa;

 — strengthening, MN;

 — cross section of the specimen, type V in the part having a notch, m.

5.2. For index resistance of the weld or heat affected zone cold cracking when welding up the minimum tensile stress from external loads at which they form cracks.

calculated as the arithmetic average of the three lowest destructive voltages with an accuracy of ±25 MPa.

5.3. For an indication of the tendency of the metal of welded joints to cold cracking according to the test results of samples type VI take the maximum diameter of the circular seam , which are formed of cold cracks. The increased tendency to cracks install two of the same results obtained by testing three specimens with the same diameter of the circular seam, which cracks. In the absence of cracks in samples with different diameters welded seam materials considered averse to the formation of cracks in the welding conditions of the sample.

5.4. For an indication of the tendency of the metal of welded joints to cold cracking according to the test results of samples of the type VIII are taking the maximum length of the welded elements, in which the formation of cracks. The increased tendency to cracks install two of the same results obtained by testing three composite samples. In the absence of cracks in all samples welded materials considered averse to the formation of cracks in the welding conditions of the sample.

5.5. For an indication of the tendency of the metal of welded joints to cold cracking according to the test results of samples of types VII and IX take the presence or absence of cracks. In the first case welded materials considered prone, the second is unwilling to crack formation in the welding conditions of the sample. The increased tendency to cracks install two of the same results obtained by testing three specimens.

In the formation of cold cracks in the samples of the types VIII and IX as a further comparative quantitative indicator taking the percentage ratio of the total crack length to the length of the control suture or minimum temperature heating of a sample in which no cracks.

5.6. Test results issued in the form of the test. Form of the Protocol given in recommended Appendix 2.

ANNEX 1 (reference)

ANNEX 1
Reference

Damn.1. Device for testing a sample of the type I

Device for testing a sample of the type I

1 — punch; 2 — rubber, hydroplastic or other elastic working body; 3 — specimen;
4 — supporting flange; 5 — threaded backing ring

Damn.1

Damn.2. A device for testing a sample of type II

A device for testing a sample of type II

1 — grip; 2 — sample

Damn.2

Damn.3. A device for testing a sample of type III

A device for testing a sample of type III

 — distance between the supports of the base;  — distance between the supports on the punch;
 — test load;  — the height of the frame;  — frame length;  — radius of curvature of the support;

1 — rod;

2 — the nut that secures the deflection of the specimen; 3 — frame (channel N 10); 4 — punch;
5 — sample; 6 — meter deflection

Damn.3

Table 1

mm

Damn.4. A device for testing specimen type IV

A device for testing specimen type IV

1 — grip; 2 — sample

Damn.4

APPENDIX 2 (recommended). Protocol testing of samples for the resistance to formation of cold cracks in welding

ANNEX 2
Recommended

Continued