GOST R 54790-2011

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  ГОСТ Р 54790-2011

GOST R 54790−2011/ISO/TR 17641−3:2005 destructive Tests of welded joints of metallic materials. Test on resistance to hot cracking in welded joints. The arc welding processes. Part 3. Tests with the application of an external load

GOST R 54790−2011/ISO/TR 17641−3:2005

Group B09

NATIONAL STANDARD OF THE RUSSIAN FEDERATION

DESTRUCTIVE TESTING OF WELDED JOINTS OF METALLIC MATERIALS

Test on resistance to hot cracking in welded joints. The arc welding processes

Part 3

Tests with the application of an external load

Destructive tests on welds in metallic materials. Hot cracking tests for weldments. Arc welding processes. Part 3. Externally loaded tests

OKS 25.160.40

Date of introduction 2013−01−01

Preface

The objectives and principles of standardization in the Russian Federation established by the Federal law of 27 December 2002 N 184-FZ «On technical regulation», and rules for the application of national standards of the Russian Federation — GOST R 1.0−2004 «Standardization in the Russian Federation. The main provisions"

Data on standard

1 PREPARED by the Federal state institution «Scientific-educational center «welding and control» at MGTU im. N. Uh. Bauman» (FGU «NORSK computer. N. Uh. Bauman»), the National Agency for control of welding (NAKS) on the basis of their own authentic translation into the Russian language of the standard referred to in paragraph 4

2 SUBMITTED by the Technical Committee for standardization TC 364 «welding and allied processes"

3 APPROVED AND put INTO EFFECT by the Federal Agency for technical regulation and Metrology of December 13, 2011 N 1031-St

4 this standard is identical to international ISO/TR 17641−3:2005* «Destructive testing of welds of metallic materials. Test on resistance to hot cracking in welded joints. The arc welding processes. Part 3. Tests with the application of an external load» (ISO/TR 17641−3:2005 Destructive tests on welds in metallic materials — Hot cracking tests for weldments — Arc welding processes — Part 3: Externally loaded tests»).
________________
* 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.

In applying this standard it is recommended to use instead of the referenced international standards corresponding national standards, the details of which are given in Appendix YES

5 INTRODUCED FOR THE FIRST TIME


Information about the changes to this standard is published in the annually issued reference index «National standards», and the text changes and amendments — in monthly indexes published information «National standards». In case of revision (replacement) or cancellation of this standard a notification will be published in a monthly information index «National standards». Relevant information, notification and lyrics are also posted in the information system of General use — on the official website of the Federal Agency for technical regulation and Metrology on the Internet

Introduction

ISO/TR 17641−3:2005 prepared by the European Committee for standardization (CEN), Technical Committee of the ST/TC 121 «welding», the Secretariat of which is assigned to the German standards Institute (DIN), in collaboration with technical Committee ISO/TC 44 «welding and allied processes», Subcommittee SC 5 «Testing and inspection of welds» in accordance with the Agreement on technical cooperation between ISO and SEN (Vienna agreement).

Series ISO 17641 consists of the following parts, under the General name of «Destructive testing of welds of metallic materials. Test on resistance to hot cracking in welded joints. The arc welding processes»:

part 1. General provisions;

part 2. Tests with the natural stiffness;

part 3. Tests with the application of external loads (a technical report).

1 Scope

This standard defines methods and procedures for testing of welded joints with the application of external load to evaluate the resistance to hot cracking.

Established the following test:

— tensile hot;

— with the application of the loads acting along and across the weld;

— on the planar stretching.

These tests can provide information on the resistance to hot cracking of the basic material, weld metal and welded joints. The evaluation is based on measuring «the temperature range fragility» (BTR), which cracks occur.

This standard is used primarily for welding units and welding material of austenitic corrosion-resistant steels, Nickel, alloys of Nickel and alloys ncelemesi. However, the fundamental provisions could be extended to other materials such as aluminium alloys and high-strength steel, the agreement between the parties to the contract.

2 Normative references

For this standard you need to use the edition of the standard EN ISO 17641−1:2004 destructive Tests of welded joints of metallic materials. Tests on hot cracking of welded assemblies. The arc welding processes. Part 1. General provisions (ISO 17641−1:2004).

3 Terms and definitions

For use of this standard the terms and definitions given in EN ISO 17641−1:2004.

4 Indicators, symbols and units

For the present standard used indicators, symbols and units given in table 1.


Table 1 — Parameters, symbols and units

5 Fundamental provisions

Test on resistance to hot cracking with the application of an external load can be used to obtain quantitative information about the occurrence of crystallization, and phase separation caused by the fall of the plasticity of cracks in accordance with table 2. These tests are applicable for evaluating resistance to hot cracking of the basic materials, welded joints and weld metal. However, the precise mechanisms of various forms of formation of hot cracks is not understood to the end.

Described test with the application of external loads use different criteria to evaluate the resistance to hot cracking. None of them exactly reproduces the conditions of temperature, cooling rate and stresses induced by limitation of deformations and the application of an external load, the wide range observed in manufacturing, where hot cracks may be considered as a potential problem. These tests can only be used for ranking core, welding materials and welding conditions. To establish their potential suitability results should be compared with the data of experience. For this reason, it is impossible to conclude about the greatest suitability of individual test specific requirement. On the basis of experience or prior experiments, the user must decide which testing is most preferable for a specific application.

Describes tests for resistance to hot cracking and its compliance with the types of cracking and possible applications are presented in table 2.


Table 2 — Tests for resistance to hot cracking, types of cracking and the application of

All tests for resistance to hot cracking associated with the application to the sample the external load using a suitable test equipment.

This load can create strain and strain rate in the temperature range of brittleness (BTR) and hence to reproduce certain aspects of the welding process. The results of the tests are quantitative and typically reproduced when using the same procedures and the same equipment.

Unfortunately, the equipment and the test procedures are not standardized and absolute reproducibility of results when tested in different laboratories is not achieved. When applied within the same lab, the same procedures and equipment repeatability is generally good.

When you experience the basic materials, the sample heat up or penetration metal welding in inert gas consumable electrode when tested with a load acting along the weld seam, when tested on a planar tensile or electric heating resistance during the tensile test in hot condition. In both cases there is a zone of thermal influence which is subjected to tension and the subsequent assessment of the resistance to hot cracking.

When experiencing the weld metal, the welding should be performed with the use of appropriate arc welding process and when testing with a load acting along the weld seam, when tested on plane tensile deformed metal during solidification of the weld. Any cracking is a base assessment. For tensile tests in the hot condition the sample are made of multi-pass welded joint and evaluate the mechanical properties using the appropriate procedure (see 6.1.1).

Multi-pass welds can also be assessed when testing with a load acting along the weld and in-plane stretching, which should be applied to samples from the multiple overlaying. Reheating the weld metal should be carried out using the process of welding in inert gas consumable electrode, similar to that used when testing base material.

Although in a test sample may be present in more than one form of hot cracking, the formation of its type, such as crystallization, can reduce the stress in the sample to such an extent that other forms will not appear. Thus, the absence in a test sample of a particular form of cracking is not in practice means the absence of risk for this type.

The test load acting in the direction across the weld, mainly designed to assess the induced cracking of the weld metal in the deformation, transverse relative to its length. The formation in this and other forms of hot cracking, which should be noted in the test report.

6 description of the tests

6.1 tensile Test in hot condition

6.1.1 General provisions

Tensile test at hot condition determines the resistance of a material to hot cracking when using the sample of cylindrical shape, which is subjected to a thermal cycle similar to the observed during welding. The sample can be destroyed in any time during the thermal cycle. To study the formation of hot cracks, if you want to play the heat caused by fusion welding, the sample is heated to the melting temperature. Use a number of cylindrical samples for tensile tests, which can be brought to failure at a given point (procedure A).

To reproduce the thermal cycle of HAZ cracking and phase separation, the sample is heated to a temperature close to the zero strength temperature (NST), below the melting point. This procedure is the same for segregated cracking in heat-affected zones of the core material and the individual cylinders of multi-pass welded joints (procedure). Such tests are used primarily to study the formation of hot cracks in weld metal is characterized by good reproducibility.

6.1.2 sample Size

Procedure A — for playback of crystallization, cracking, and heated to the melting point of the applied sample with a length of 130 mm and a diameter of 10 mm.

Procedure for playback of exudation cracking in the heat affected zone and determining the temperature of the NST uses a sample of length 110 and a diameter of 6 mm.

The specimen dimensions and the location of welded joint is shown in figure 1.

Figure 1 — specimen Dimensions for tensile tests in the hot condition

Dimensions in mm

1 — weld metal; 130 for crystallization cracking, 110 — for segregated cracking

For segregated cracking.

For crystallization cracking.

Figure 1 — specimen Dimensions for tensile tests in the hot condition

6.1.3 Protective atmosphere

Samples for test are heated in the chamber, which after vacuum filled with argon to prevent excessive oxidation of the metal at high temperature. The oxygen content in the start of the test shall not exceed 0.1%.

6.1.4 test Procedure

6.1.4.1 General provisions

The sample temperature is measured with a thermocouple Pt-PtRh diameter 0,2/0,25 mm, fixed in the middle of its length by percussion welding.

6.1.4.2 Procedure And Study of crystallization cracking

A specimen of 10 mm diameter fixed in a water-cooled copper clamps and then heated to the melting point using controlled heating resistance. The Central part of the sample and protect from destruction while close to the melting point with the surrounding quartz tube. During solidification and further cooling the clamps of the fixture remain fixed so that the limiting deformations from shrinkage has caused cracking.

When subsequent tests, after performing the heating cycle can be applied controlled compression to set the deformation to avoid cracking.

6.1.4.3 procedure In the Study of phase separation cracking

To determine the peak temperature of zero strength (NST), a sample with a diameter of 6 mm are heated to a temperature of 50 °C — 100 °C below a solidus temperature at a rate of about 50 °C/s (for some alloys up to 250 °C/s). At this stage, the heating rate reduces to about 2 °C/s until the sample is destroyed under the action of sustained load approximately equal to 100 N. Plasticity in the hot state can be determined using tests during heating and cooling.

For testing after cooling the sample should be heated to the NST and then cooled to a temperature of carrying out tensile tests.

For testing by heating the sample need only be heated to test temperature and then subjected to stretching by the strain rate of 50 mm/s. Speed of heating and cooling must meet the reproducible thermal cycle of the weld metal.

While heating is necessary to ensure the free elongation of the sample, however, if available information about the real situation, it is possible to reproduce the deformation when welding with the use of program controlled equipment. During cooling to ensure the free compression of the specimen or alternative controlled compression to achieve the recovery temperature plasticity (DRT).

This compensates for compression of the sample in the axial direction and can be used for quantitative strain measurements, necessary to prevent cracking. Usually to construct a reliable curve of plasticity in the hot condition requires at least 12 samples.

6.1.5 test Results

After the test, local contraction () in the fracture zone is calculated as a fraction of the initial cross section of sample for test. The limit of the tensile strength () can be obtained by dividing the peak force to the original cross-sectional area of the sample. This characteristic local narrowing of the cross section should be submitted for testing during heating and cooling as a function of test temperature. Typical graphs are shown in figure 2.

Figure 2 — Graphs based on the results of the test

1 — heating; 2 — cooling

Figure 2 — Graphs based on the results of the test

Material sensitive to hot cracking, while it is in the temperature interval of brittleness (BTR), which is determined by the difference between the zero strength temperature (NST) and the ductility recovery (DRT). For comparison of materials, the DRT is defined as the temperature at which local contraction upon cooling reaches 5%.

Sensitivity to segregated cracking of the material can be characterized by the ratio of ductility recovery (RDR), the speed of recovery (DRR) and the range of temperature of zero plasticity (NDR) — see table 1.

The most reliable criterion is the coefficient of ductility recovery (RDR), which can be used to predict hot cracking in the heat affected zone of the base metal.

6.2 principles of the test with a load acting along the weld seam (Varestraint test), and the load acting across the weld (Transvarestraint test)

6.2.1 General principles

The test load is acting along the weld and the load acting across the weld, can be used to measure the resistance to hot cracking of the base metal, filler materials and weld assemblies using the simultaneous execution of the weld and application testing efforts.

When the test load acting along the weld, the force is applied in the longitudinal relative to the weld direction. You can play three types of hot cracking, namely, crystallization, and phase separation caused by a drop in ductility (see table 2).

When the test load acting across the weld, the stress applied in the transverse relative to the seam direction. This test is designed primarily to assess the sensitivity to cracking during solidification. Loading material may be base metal or metal previously made weld seam obtained by pereplavleni arc welding with non-consumable electrode or weld metal performed when tested.

Figure 3 illustrates General principles of testing when loading the sample and synchronizing of welding procedures and loading requires special equipment. Because it has significant differences, the reproducibility of results when tested in different laboratories can be quite low. However, tests conducted in one laboratory, can be used to rank the materials and compare them with the materials, where resistance to cracking under practical conditions are known.

The obvious advantage of the test is speed of testing and evaluation, combined with low scatter and good reproducibility of results (when applying the same test machine). The test is able to identify the impact of small changes in the chemical composition of the material and/or welding conditions. For a given set of conditions (typically 1 to 3) useful information can be obtained with a small number of trials.

6.2.2 sample Size

The specimen dimensions are not fixed and depend on the material used, accuracy and testing efforts, developing testing machine.

When the test load acting along the weld seam, the most simple form of the sample is a flat plate of length (a) from 80 to 300 mm, a width (a) from 40 to 100 mm and a thickness of () dependent on the test material and of the efforts developed by the test machine.

When the test load acting across the weld, a typical specimen dimensions are: length 100 mm, width 40 mm and thickness 10 mm.

Note — the sample Sizes for tests of both longitudinal and transverse relative to the axis of the weld load is applied to thin sheet materials and pipes can be changed.

Figure 3 — Scheme of the test load acting along the weld and the load acting across the weld

Dimensions in mm

1 — burner position during bending of the sample; 2 — completion of welding; 3 — sample; 4 — adjustable hydraulic system the speed of bending of the sample

Figure 3 — Scheme of the test load acting along the weld (top) and load current across the weld (below)

6.2.3 test Procedure

The tests in the standard form involves performing welding in inert gas consumable electrode welding of a seam on the basic material or pre-melted metal.

Welding parameters can be selected depending on private applications, but standard conditions are:

To 12.5 V, 85 A, 18 cm/min. (low heat attachment);

Is 13.5 V, 205 And 11 cm/min (large attachment heat).

Welding parameters must be recorded.

At a fixed point cushion, deposited by welding in inert gas consumable electrode, typically in the center of the sample when bending around a mandrel of a predetermined shape (see figure 3) is its deformation. Loading is usually carried out by hydraulic actuator with a controllable speed of the plunger, which should reach 1.8 mm/s, and automatically synchronized with the welding.

6.2.4 test Results

At the end of each test should be visually at 25 x magnification to check for cracks. The total length of visible cracks () must be determined and displayed on the graph as a function of strain from bending. The curve defining the crack length in dependence of the deformation on the sample surface enables to evaluate the resistance to formation of hot cracks (see figure 4).

Figure 4 is a Typical representation of test results the load acting along the weld and the load acting across the weld

1 — the total length of cracks; 2 — radius of the mandrel/plunger; 3 — sample for testing load acting along the weld seam; 4 — the length measured by stereomicroscope with 25 times magnification: , 5 — speed welding; area 1 — high resistance to hot cracking; area 2 — increased risk of formation of hot cracks; area 3 — high risk of formation of hot cracks

Figure 4 is a Typical representation of test results the load acting along the weld and the load acting across the weld

Although the results shown as examples in figure 4 refer to the test load acting along the weld seam, such diagrams can be obtained when the test load acting across the weld, a curve that establishes the dependence of the total length of the cracks caused by bending deformation on the surface. Presentation of results figure 4 is an illustration of how they can be evaluated from the point of view of prediction of the behavior during welding. Three areas that indicate «good weldability», «limited weldability» and «bad weldability», represent only an illustration and does not give an absolute evaluation of weldability or a resistance to hot cracking.

Because it is extremely difficult to establish a link between the deformations given in the testing and occurs in a welded connection with the actual production, it is highly recommended that the test is used to compare new materials or welds with those whose characteristics are known from practice.

6.3 Test planar tension (Flat tensile test)

6.3.1 General provisions

Test of planar stretching (e.g., resistance to cracking, programmable deformation) is able quantitatively to determine the sensitivity to hot cracking of the base metal, weld metal and welding procedures.

Test for resistance to hot cracking is performed using a single sample for testing in-plane stretching, which is loaded in the testing machine for horizontal extension with a programmed linear increase in its velocity. The procedure of the PVR-test (programmed deformation) different from the test load acting along the weld and the load acting across the weld, is actually the fact that programmable deformation of a linear increase in the speed of stretching occurs during the welding roller in the same direction. The test can be carried out with the use of filler materials or without it.

The basic materials can be assessed using standardized parameters of welding in inert gas consumable electrode welding materials with application of welding conditions recommended by the manufacturer or available in the actual production.

To minimize the risk of formation of hot cracks welding procedure can be optimized by varying its conditions (e.g. welding parameters, like welding material, shielding gas mixtures, combinations of flux and wires, etc.).

All three types of hot cracking (solidification, liquation and fall of plasticity) can be played in one trial, reflecting the sensitivity of the material to him.

When available for comparison, reference data is required only one test to establish the resistance of the basic material or the weld metal hot cracks.

The test is reproduced with a small spread and are well able to distinguish three types of hot cracking.

6.3.2 Size of sample

The exact dimensions of the sample on the planar stretching is determined by the capacity of the testing machine and are typically (4010300) mm (widththicknesslength), as shown in figure 5. The sample surface must be machined and polished in the longitudinal direction before reaching the surface roughness parameter RA of 6.3 µm. Should be avoided perpendicular to the direction of welding notches on the surface, which may cause false cracks. Sample testing in-plane tensile weld in a special clamping device to ensure that equipment programmed deformation.

Figure 5 — Dimensions control sample for test of resistance to cracking, programmable deformation (PVR-test)

Dimensions in mm

1 — the surface polished in longitudinal direction

Figure 5 — Dimensions control sample for test of resistance to cracking, programmable deformation (PVR-test)

6.3.3 test Procedure

Test procedure in the standard form shown in figure 6. Welding (with constant speed) is performed in combination with a linearly increasing speed of the stretch , starting with zero and reaching 70 mm/min at the end of the test procedure. Although the test in the standard form is performed when the coincidence of the directions of welding and tensile loads, it is also possible to evaluate the welds perpendicular to the direction of its action.

Figure 6 — test Procedure for resistance to hot cracking programmable deformation (PVR-test)

1 — linearly increasing speed stretching; 2 — time; 3 — the first hot crack; 4 — welding speed

Figure 6 — test Procedure for resistance to hot cracking programmable deformation (PVR-test)

After the test welding roller on a control sample to check on the microscope with 25 x magnification to establish the critical loading rate corresponding to the first appearance of hot cracks for each of the various types of hot cracking (if the test is more of the same type).

6.3.4 test Results

The critical loading rate corresponds to appearance of the first cracks that is observed visually at 25 x magnification. This speed is used as a criterion for the PVR-test to determine the resistance to hot cracking. It can be set for each type of hot cracks.

7 test reports

Any evaluation of resistance to hot cracks must include in each test report as a minimum, the following information:

a) reference to this standard;

b) description of test (s);

c) the characteristics of the base and filler materials (if applicable);

d) identifying a test sample/samples;

e) dimensions of control and sample/samples;

f) welding conditions;

g) any special conditions of testing;

h) results (specific to the tests).

App YES (reference). Information about the compliance of the referenced international standards reference the national standards of the Russian Federation

App YES
(reference)

Table YES.1