gb code-hardness

8/12/2019 GB code-Hardness

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ICS 25.160.10

J33

Record No.: 31130-2011

Electric Power Industry Standard of the People's Republic of China

DL/T 819-2010

Replace DL/T 819-2002

The code of the welding heat treatment for power plant

Issued on January 9, 2011 Implemented on May 1, 2011

Issued by National Energy Administ ration


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Table of Content

Preface............................................................................................................................................. 11. Scope.......................................................................................................................................... 32. Normative Reference................................................................................................................. 33. Terms and Definitions............................................................................................................... 34. General requirements................................................................................................................ 55. Heating device and heating method....................................................................................... 66. Welding heat treatment technology......................................................................................... 87 Temperature measuring........................................................................................................... 128. Post-weld heating treatment technology measures............................................................ 159. Quality inspection..................................................................................................................... 1710. Technical documents............................................................................................................. 19Appendix A ..................................................................................................................................... 20(Normative Appendix) .................................................................................................................... 20Technical conditions for flexible ceramic resistive heater .............................................................. 20Appendix B ..................................................................................................................................... 22(Informative Appendix) ................................................................................................................... 22Operation card for welding heat treatment, operating record for welding heat treatment, operation

statistical table for welding heat treatment ...................................................................................... 22Appendix C ..................................................................................................................................... 25(Informative Appendix) ................................................................................................................... 25Preheating temperature for common steel ....................................................................................... 25Appendix D ..................................................................................................................................... 27(Informative Appendix) ................................................................................................................... 27Post-welding heat treatment temperature and time for common steel ............................................ 27Appendix E ..................................................................................................................................... 29(Normative Appendix) .................................................................................................................... 29Quality evaluation form for post-welding heat treatment ............................................................... 29


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Preface

According to experience since the implementation of DL/T 819-2002, with reference to the

application of new material technology achievements for supercritical, ultra-supercritical

thermal power unit in recent years, as well as the scientific and new technology

achievements for welding heat treatment, with reference to the United States ASME, AWS

and other standards, compared with the DL/T 819-2002 Thermal Power Plant Welding Heat

Treatment Technical Code, this standard is modified as follows:

--- The scope of this standard is expanded to all steel parts of thermal power plant for

which the welding heat treatment is necessary;

--- Structurally, in order to describe the temperature measurement in a more detailed way,

Chapter 7 of the original standard on temperature measurement is enriched to be a

separate chapter; in order to emphasize the process control, evaluation process and

requirements on quality of heat treatment after welding, Chapter 8 of the originalstandard is adjusted to be a separate chapter.

--- The terms of GB/T 3375 are adopted, with the term range of soak band and width of

heating added.

--- The requirements for thermal insulation material are added.

--- The content on Safety requirements is simplified.

--- The heating method is more detailed, and the content of the heating equipment of the

original standard is adjusted with the requirements on heating furnace added, and the

limitation on the thickness of the medium frequency induction heating is changed from

the original 30mm to 100mm.

--- The original Section 6.1 is changed as Determination of documents on site welding

heat treatment, with the relationship between assessment of welding process and site

process instruction documents clarified.

--- Requirements on weld preheating, heat treatment of dissimilar steels are detailed.

--- The requirements on heat treatment constant temperature and holding time after

welding are adjusted, with new steels added.

--- The thermocouple installation requirements are adjusted, with the use requirements of

the compensating conductor added.

--- Temperature measurement requirements for other methods are adjusted.

--- The heating range of heat treatment after welding has been adjusted.--- The quality evaluation of heat treatment after welding has been added.

This standard is put forward by the China Electricity Council.

This standard is filled by the Technical Committee for Welding Standardization of power

station in the electric power industry.

This standard is mainly drafted by China Electric Power Research Institute.

This standard is also drafted by Henan No. 1 Thermal Power Construction Company,

Shanghai Electric Power Construction Co., Ltd, Shanghai Electric Power Construction


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Second Engineering Company, Anhui Electric Power Construction First Engineering

Company.

This standard is mainly written by Guo Jun, Chang Jianwei, Qiao Yaxia, Qiu Minglin, Feng

Caigen, Lin Zhihua and Yu Shihong.

From the date of implementation, this standard replaces DL/T 819-2002.

During the implementation of this standard, the suggestions or advice can be sent to the

Management Center for Standardization of China Electricity Council (Baiguang Road 2#1,

Beijing, 100761).


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The code of the welding heat treatment for power plant

1. Scope

This code provides the welding heat treatment requirements on the fabrication, erection

and inspection of steel bearing-pipe and component for terminal power plant .

This code is applicable to the preheating, post-heating and post-weld heating treatment

on the welding piece.

2. Normative Reference

The following documents are indispensable for the application of this document. Where

the reference documents are marked with a date, only the version with a date is applicable

to this document; otherwise, the latest version (including all the modification lists) shall be

applied.

GB/T1234 High Resistance Heating AlloyGB/T2614 Nickel-chrome and Nickel-silicon Thermocouple Wire

GB/T 3375 Welding Terminology

GB/T 4654 General Technical Conditions of Non-metallic Base Infrared Radiation Heater

GB/T 4989 Compensation Lead Used for Thermocouple

GB/T9452 Measuring Method for Effective Heating Area of Heat Treatment Furnace

GB/T 16839.1 Part 1 of Thermocouple: Indexing Table

GB/T 16839.2 Part 2 of Thermocouple: Tolerance

GB/T 17394 Metal Leeb Hardness Test Method

DL/T 752 Welding Technical Procedures of Dissimilar Steel for Thermal Power Plant

DL/T 868 Qualification Procedures for Welding Process

DL/T 869 Welding Technical Procedures for Thermal Power Plant

DL/T 884 Technical Guideline of Metallographic Examination and Assessment for

Thermal Power Plant

JB/T 9238 Technical Conditions of Industrial Thermocouple Technology

3. Terms and Definitions

The terms and definitions of GB/T 3375 are applicable to this standard.

3.1 Welding heat treatment

The welding heat treatment refers to a process to improve the welding processperformance, the metallographic organization of welding joint and mechanical property

through the full or local heating, thermal insulation and cooling before, during or after

welding, including pre-heating, post-heating and post-weld heating treatment.

3.2Range of soak band

During the heating process at constant temperature, the temperature difference of welding

joint in the direction of through thickness is less than or equal to the specified scope of the

heated metal.

3.3 Width of heating

It refers to the minimum width of imposed heating source during the heating process, in

order to reach the required range of soak band for the welding piece, such as the width of


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heating device during the electrical heating and the heating range during the flame

heating.


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4. General requirements

4.1 Personnel

4.1.1 The welding heat treatment personnel should be taken the special training and with the

certificates. If the personnel without the certificates, they can only do the auxiliary

work of the welding heat treatment.

The welding heat treatment staff includes the technicians and operators (also called

workers).

4.1.2 Responsibilities of heat treatment technicians

a) Take charge of the preparation of construction scheme, operation instruction, process

card and other technical documents for welding heat treatment, and the technical

disclosure.

b) Direct and supervise the work of heat treatment workers, and elevate the heat treatment

procedures and results after welding.

c) Collect, summarize and settle the welding heat treatment data.

4.1.3 Responsibilities of heat treatment workers

a) Strictly obey the construction scheme, operation instruction and process card for welding

heat treatment during the construction.

b) Record the heat treatment procedures.

c) Insist on self-inspection after heat treatment.

4.2 Welding device

4.2.1 The device should satisfy the technology requirement to be safe and reliable.

4.2.2 During the welding heat treatment, the measuring device such as measurement &

control device and thermocouple should be calibrated and used before expiration date.

The measuring device should be calibrated again after being maintained.

4.2.3 The temperature-control accuracy of the device should be within 5.According

to the temperature (which is indicated on the automatic recorder), adjust the temperature

which is on the computer temperature-control system whose display unit shall be better

to be equipped with cold end automatic temperature compensator. Adopt the printed

welding heat treatment record curve, and the error should be smaller than 0.5% which has

been confirmed with calculation.

4.3Thermalinsulationmaterial

4.3.1The thermalinsulationmaterialsused for welding heat treatment shall comply with

the following requirements:

a) The thermal resistance value of thermal insulation materials shall be no less than

0.35m2/W.

b)For the thermalinsulationmaterialsused for flexible ceramic resistance heating or far


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infrared radiation heating, the melting temperature shall be over 1150 .

c) The thermal insulation materials used for induction heating shall have no shielding

effect to the electromagnetic field.

d)The thermalinsulationmaterials used for flame heating shall be dry.

4.3.2 It is better to use aluminum silicate refractory fiber products, glass fiber cloth and

high silica cloth.

4.4 Safety requirements

4.4.1 In addition to the relevant requirements on safety operation, the following

requirements shall also be obeyed during the welding heat treatment work:

a) The protective articles should be worn to forbidden the scald.

b) At least two persons should be on duty.

c) When taking the electric heating, the conductor of heating device shall be prevented from

contacting with the welding piece.

4.4.2 When using the infrared thermometer, the laser shall be prevented form directly or

indirectly hurting your eyes.

5. Heating device and heating method

5.1.1 Furnace

a) It shall be equipped with temperature measurement and control devices for the automatic

recording of temperature.

b) For the effective heating area of furnace, the accuracy of thermal insulation shall reach

10, and the measuring method shall comply with GB/T 9452.

c) The calibration period of measurement and instrument of the effective heating area

shall be six months.

d) The furnace can be heated in electrical heating or flame heating method.

5.1.2 Flexible ceramic resistance heating device and far infrared radiation heating device


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a) The technical conditions of flexible ceramic resistance heating device shall comply with

Appendix A.

b) The technical conditions of far infrared radiation heating device shall comply with GB/T

4654.

c) If several heating devices are controlled by one furnace, the resistance difference

of each heating device shall be within the scope of 5%.

d) It shall be equipped with temperature measurement and control devices for the automatic

recording of temperature and the automatic control of the whole process.

5.1.3 Electromagnetic induction heating device

a) Its output power and frequency can make automatic response and meet the technical

requirements.

b) It shall be equipped with temperature measurement and control devices for the automatic

recording of temperature and the automatic control of the whole process.

c) The circle space of induction coil shall be determined according to the thickness of welding

piece and the proposed heating width.

5.1.4 Flame heating device

a) When use the oxygen-acetylene or other combustible liquid and gas, the corresponding

device may be used for flame heating.

b) The liquid and gas must be stored in cylinder (container) or pipe, with appropriate

measures taken to prevent the backfire.

c) The appropriate flame burning device shall be selected according to the size of welding

piece and the proposed heating area.

d) It shall be equipped with temperature measurement devices to monitor the temperature of

welding piece.

5.2 Application scope of heating method

5.2.1 The furnace is applicable to the preheating, post-heating and post-weld heating

treatment of the welding piece. For the different size or heating method of the welding

piece, the following requirements shall be reached:

a) When the welding piece is too large that it shall be divided into several parts for post-weld

heating treatment, the overlapped heating length shall be no more than 300mm.

b) When the flame heating is adopted, it shall be ensured that the flame will not directly wash

the welding piece to be heated.

5.2.2 The flexible ceramic resistance heating, far infrared radiation heating and

electromagnetic induction heating are all applicable to the preheating, post-heating and

post-weld heating treatment of the welding piece. For the welding piece with obvious

sharp corner or at the thickness more than 100mm, the intermediate frequency

electromagnetic induction heating shall not be used.

5.2.3 The flame heating method can be used for the preheating and post-heating of the

welding piece when the other methods are not applicable. If the flame heating method

is used for post-weld heating treatment of the welding piece, the following requirements

shall be reached:


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a) The detail operation program shall be prepared to ensure that the heating is relatively

uniform, with effective temperature control measures taken.

b) The flame heating method is not applicable to the post-weld heating treatment of the

high-alloy steel welding piece.

5.3 Control of flame heating

5.3.1 When several nozzles are used, they should be symmetrically arranged and uniformly

heated.

5.3.2 The flame center should be more than 10mm away from the working area. The

moving speed of the nozzle should be stable and not long stay at one place. In the

process of flame heating, the burning of flame shall be carefully controlled to

prevent metal oxidization orrecarburization.

5.3.3 The flame heating should make the welding seam as center; heating width should be

50mm more than the welding seam on the two ends.

5.3.4 The constant time of the flame heating should be calculated as one minute for each

one millimeter of the welding piece.

5.3.5 After the heating, the dry heat-insulating material should be used immediately for the

purchase of thermal insulation.

6. Welding heat treatment technology

6.1 Determination of documents on weld ing heat treatment

6.1.1 The key parameters of the welding heat treatment (such as heating manner, heating

time, heating speed and isothermal temperature) shall be evaluated in accordance

with the welding procedure qualification stated in DL/T868.

6.1.2 The actual specifications of welding piece and construction conditions should be

combined with the site condition to prepare the operation instruction or process card of

welding heat treatment (in the form as shown in Appendix B), and confirm the key

parameters of the welding heat treatment which can be implemented during the

welding heat treatment of the first welding piece.

6.1.3 The operation instruction or process card of welding heat treatment confirmed by the

first welding piece will be carried out in the follow-up work.

6.2 Preheating

6.2.1 Preheating temperaturea) The preheating temperature of welding piece shall comply with the requirements of

operation instruction or process card, and that of the common steels shall refer to

appendix C.

b) When welding the dissimilar steels, the preheating temperature should be adjusted

according to the requirements stated in DL/T 752.


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6.2.2 Preheating manner and heating area

a) If the pipe external diameter is larger than 219mm meanwhile the pipe thickness is

larger than or equal to 20mm, take the flexible ceramic resistance heating, far infrared

radiation heating and electromagnetic induction heatingmethod for preheating.

b) When the thermocouple outside the groove of monitoring welding piece reaches the

preheating temperature, it shall be held for a certain time to make the temperature of the

groove parts to be welded meet the requirements.

c) When the heater is respectively arranged on both sides of the weld joint or covers the

whole area, the preheating width should be calculated from the welding edge: if the flexible

ceramic resistance heating or far infrared radiation heating method is used, the heating

width at each side should be no small than four times of the welding piece thickness; if the

electromagnetic induction heating or flame heating method is used, it should be no

small than three times of the welding piece thickness and no small than 100mm.

d) When the weld area is like dotted form, the heating area is a nearly round area with thewelding center as the center of a circle and with nine times of the maximum depth size

of weld seam as the radius.

6.2.3 Pre-heating warming up

a) The pre-heating warming up shall be carried out before welding again in case of the

occurrence of interrupt.

b) The process of pre-heating warming up corresponds to that of pre-heating.

6.3 Post-heating

6.3.1 For the welding piece which has the cold crack tendency, if the post-heatingtreatment cannot be taken immediately after the welding work, the post-heating

should be taken. The post-heating process is: 300~400 for the heating temperature,

2h~4h for the holding time.

6.3.2 For the welding on Martensitic steel, if the post heating is necessary, it should be

taken after the welding piece is at 80~120 for the heating temperature and 1h~2h

for the holding time.

6.3.3 The post-heating width should be no small than the preheating width.

6.4 Post-weld heating treatment

6.4.1 The post-weld heating treatment shall be carried out according to the provisions of

DL/T 869 and DL/T 752 or other regulations or technical documents. For the

Martensitic steel containing 9%~12% Cr, the post-weld heating treatment shall be

carried out immediately before its transformation; otherwise, the post-heating is

applicable according to the requirements of Section 6.3.

6.4.2 The principles to select the constant temperature of post-weld heating treatment:

a) It shall not exceed the lower transformation temperature (Ac1) of the welding material

melting metal or the raw materials at both sides (whichever is lower), generally 30

lower than this Ac1.

b) For the welding joint of tempering structure, it shall be lower than the backfire oftempering treatment.


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c) The loading tools used for cooling weld joint shall not be removed until the post-weld

heating treatment is finished.

d) For the welding piece with the thickness more than 100mm, special measures shall be

taken to ensure enough range of soak band during the post-weld heating treatment.

7 Temperature measuring

7.1 Selection of Temperature measuring method

7.1.1 According to the heating methods, select the suitable method to measure the

temperature.Contact process is always adopted for flexible ceramic resistance heating,

far infrared radiation heating and electromagnetic induction heating, while non- contact

process is always adopted for flame heating.

7.1.2 Contact process temperature-measuring generally adopts the thermocouple,

temperature-measuring pen, contact surface thermometer etc. Non-contact process

temperature-measuring generally adopts the infrared thermometric indicator.

7.2 Requirements on thermocouple temperature-measuring

7.2.1 Selection ofthermocouple

a) The thermocouple can be adopted according to the heat treatment temperature,

indicator type and accuracy of thermometer. The diameter and length of the thermocouple

should consider the size of welding piece, heating width and fixing manner.

b) The K graded waterproof armoring thermocouple or K gradedthermocouplewire should

be adopted, with the quality reaching the requirements of GB/T168391, GB/T168392,

GB/T2614 and JB/T9238.


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P9

7.2.2 Erection of thermocouple

a) The erected location of the thermocouple should ensure that the

temperature-measuring is accurate, reliable and representative.

b) During the preheating, the thermocouple should be arranged within the heating area,and the monitoring thermocouple shall approach to the groove to be welded as

much as possible. If necessary, other temperature measuring methods shall be

used to check the temperature at the groove to be welded, as shown in Figure 2.

Width of heating

Monitoring thermocouple

Temperature-controlling thermocouple

No.1 thermocouple

No.2 thermocouple

Figure 2 Figure on width of heating and layout of measuring points

c) Generally, if the pipe outer diameter is no more than 273mm during the post-heating and

post-weld heating treatment, a thermocouplecan be used at the center of the weld seam;more than two thermocouples could be arranged along the circle, but must ensure

even interval and one arranged at thecenter of the weld seam and the others arranged

where it is one time the thicknessaway from the weld seam and no more than 50mm, with

the temperature controlled by the thermocouple at the weld seam, as shown in Figure 3.

Width of heating

Width of thermal insulation

Weld seam

Monitoring thermocouple

Temperature-controlling thermocouple


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No.1 temperature area

No.2 temperature area

Figure 3 Figure on temperature-controlling area and layout of thermocouple

for post -heating and post-weld heating t reatment

d) It shall be noted that the different may lead to the uneven temperature in the heating

area. For the pipe with outer diameter larger than 273mm, if this effect is obvious,

select applicable temperature-controlling to install thermocouple in accordance with

actual condition of heating area.

e) For the post-heating and post-weld heating treatment of special-shaped welding piece

(such as Tee and tube seat), appropriate measures shall be taken to make the actual

maximum heated temperate on the heated weld seam. There shall be at least three

thermocouples, one on the weld seam (for temperature-controlling) and two on

the same line on the outer wall of the same bus line of the pipe 20mm away fromthe edge of weld seam.

7.2.3 Fixation of thermocouple

a) The thermocouple should be fixed by stored-energy welding, and other methods

which can ensurethat the hot side is well contacted with the welding pieces.


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b) When the thermocouple is fixed by welding, it should be polished and cleaned upafter

the heat treatment.

7.2.4 Precautions of installing thermocouple:

a) The thermocouple shall be arranged on representative welded joint at time of treating

many welding pieces in the same stove in order to ensure the individual accuracy of

temperature-measuring.

b) If percussion welder is adopted for welding the thermocouple, the interval between

welded joints of two thermocouple wires shall be no more than 6mm and two

thermodes and welding pieces shall be insulated.

c) If electromagnetism induction is adopted for heating, the elicitation direction of

thermocouple shall be vertical to induction coil

dCompensation wire shall be used for elicitation.

7.2.5 Use of compensation wire:

a) KCA, KCB type compensation wire matching K indexing thermocouple shall be usedand its quality shall be in agreement with requirements of GB/T 4989

bAt time of connecting compensation wire and thermocouple, the same polarity shall

connect and the connection shall be firm.

c) After using the compensation wire, cold end temperature compensation measures shall

be adopted if the cold end temperature is not stable.

7.3 Temperature measurement requi rements of other methods

7.3.1 Scratch temperature measurement pen:

a) Scratch temperature measurement pen shall be selected with proper combination

according to heating temperature and precision of temperature measurement

b) At time of using scratch temperature measurement pen, change of scratch color shall

be observed promptly to prevent the temperature beyond specified scope.

7.3.2 Portable infrared thermometer:

a) Portable infrared thermometer shall be selected according to scope of measurement

temperature

b) Temperature shall be measured according to instructions of instrument.

8. Post-weld heating t reatment technology measures

8.1 Heating area8.1.1 The heating width of general pipeline butt joints shall be selected in accordance with

heating methods and the ratio between external diameter D and wall thickness . The

minimum width shall no less than 100mm. The heating center shall be located at

center of the welding joint. Measures shall be taken to decrease the temperature

difference between external and radial.

8.1.2 For electromagnetic induction heating, the heating width shall be calculated from the

center of the welding joint. Each side width shall no less than 3 times of the wall

thickness of the pipeline.

8.1.3 For flexible ceramic resistor heating and far infrared radiation heating, the heating

width is determined by the following methods:


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a) D/ 7.5: each side heating width from the welding joint shall be no less than 4 times

of the wall thickness;

b) 7.5 < D/ 7.5 each side heating width from the welding joint shall be no less than 5

times of the wall thickness;

c) 10 < D/ 15 each side heating width from the welding joint shall be no less than 6

times of the wall thickness;

d) D/ > 7.5each side heating width from the welding joint shall be no less than 7

times of the wall thickness.

8.1.4 For the heating on tube seat, it should adopt the circle or annular heating method.

The heating width between the main pipe and the receiving pipe should be not

smaller than two times of the bigger thickness.

8.1.5 For the special-shaped welding piece (such as reducer, tube seat and Tee), more

heating devices controlled by the separate area shall be arranged at the side the metal

materials are larger in size, and the heating power is adjusted according to the actual

condition and temperature distribution of the welding piece.

8.2 Erection of heating device

8.2.1 For the erection of the flexible ceramic resistance heating device and far infrared

radiation heating device, the following provisions shall be reached:

a) When erecting the heating device, the overlap, slag, spatter on the welding pieces

should be cleaned up. Make the heater closely touch the surface of the weldingpieces. If necessary, special tools should be made.

b) For the post-weld heating treatment on the horizontally arranged pipes (whose

diameter is larger than 273mm) and the big size components, the temperature

-controlling in separate areas is applicable as per actual condition.

c) If several welding joints heating are controlled by one temperature-measuring

point, the arrange manner of the welding joint heater should be same, and the width and

thickness of the insulation layer should be same as far as possible.

Note: When take the preheating on the pipe with the cord-type heater, the heater should

be symmetrically arranged on the two ends of the groove. The twining coils numbers

and density should be same as far as possible. The twining direction should be

opposite.


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8.2.2 The installation of induction coil shall comply with the following requirements:

a) When the working frequency induction heating is used, the space between the induction

coil and the working piece is 10~50mm; for the induction heating at the intermediate

frequency or above, the space is 10~80mm.

b) For the installation of induction coil, the short circuit shall be avoided between circles.

c) No magnetic medium shall be left on the welding piece.

8.3 Temperature-difference control and thermal insulation

8.3.1 During the constant-temperature procedure of the welding heat treatment, for the

bearing-pipes (which is within the heating scope), the temperature-difference

between any two points should be smaller than 50.

8.3.2 The insulation width of the welding heat treatment should be calculated from the

edge of the welding seam groove, it should be no smaller than two times than pipe

thickness on each side, and more than 100mm.

8.3.3 The insulation layer thickness of welding heat treatment should be 40mm~60mm,

which can be reduced during induction heating. The temperature-difference of the

pipes can be reduced by changing the thickness of insulation layer.

9. Quality inspection

9.1.1 Quality inspection items

9.1.1 Following inspections should be taken before the heating treatment workers raise

the temperature, so as to confirm that it complies with the requirements of operation

instruction or process card:

a) Heating and temperature-measuring device, tools and wiring.

b) Heating device arrangement and temperature control area.

c) Heating area should satisfy the requirements of code and standard. The width and

thickness of the insulation layer should be suitable.

d) The erection method, location and quantity of the temperature-measuring points.

e) The stated heating temperature, holding time, temperature rising or reducing speed.

f) The site safety requirements.

9.1.2 The heat treatment workers shall keep the site operation record during the

welding heat treatment (in the form as shown in Appendix B), the requirements ofthe self-check after the work which has been confirmed by the heat treatment

technicians are as following:

a) The technology parameters are within the controlling scope, with the automatic

recording curve.

b) Thermocouple should be without damage and displacement.

c) The welding heat treatment curve should be same with the process card.

9.1.3 Welding heat treatment technicians or welding engineers shall selectively check not

less than 20%(same steel welding piece containing 9%-12% of Cr shall be no less than

50%) of the same welding piece on the basis of qualification of self-checking by heat

treatment workers. They shall check relevant records and appearance of welding piece


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which has been conducted with post-weld treatment and evaluate the quality. The

contents are seen in the Appendix E and evaluating items contain all inspection items in

the table for quality evaluation of post-weld heat treatment.

9.2 Quality requirements o f post-weld heat treatment

9.2.1 The quality of post-weld heat treatment shall be controlled by process control. If the

welding piece has been checked and in agreement with requirements according to the

provisions of 9.1.1 and 9.1.2, the quality of post-weld heat treatment shall be confirmed

as qualified. Otherwise, it shall be confirmed as unqualified.

9.2.2 If the heat treatment workers find unqualified items according to 9.1.1, they shall

immediately rectify and make them qualified; if they find unqualified items according to

9.1.2 or have doubts at time of selective examination according to 9.1.3, welding heat

treatment technicians or welding engineers shall jointly organize evaluation with quality

inspection personnel to find out reasons and formulate further qualify assurance

measures. In the meanwhile, weld hardness test or on-site metallographical test shall

be directly conducted.

9.2.3 Leeb hardness tester can be adopted to test the hardness according to provisions

of GB/T 17394 converted Brinell hardness value of weld joint shall be no more than 40%

of hardness value of original materials or 90% of harness value of original metal. If

hardness value of weld joint is too low or too high, on-site metallographical test shall be

conducted according to provisions of DL/T 884.

9.2.4 Welded joint the weld joint hardness of which is checked to be qualified shall be

judged to be in agreement with post-weld heat treatment.

9.2.5 In terms of welded joint with dissimilar steel which has been conducted with

post-weld heat treatment, the requirements of hardness inspection shall be performed

according to relevant provisions of DL/T 752.

9.3 Treatment of unqualified qualit y of post-weld heat treatment

9.3.1 If hardness value of weld joint is higher than welded joint of specified value caused

by insufficient temperature or time of post-weld heat treatment or on-site

metallographical test judges post-weld heat treatment to be insufficient, post-weld heat

treatment shall be conducted again.


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9.3.2 If the hardness value is 80% lower than specified value, for constant temperature of

post-weld heat treatment is above standard or constant temperature of post-weld heat

treatment is overlong, or on-site metallographical test judges the weld joint of weld

metal is too hot, unless normalizing and tempering heat treatment can be implemented

on the site, the welded joint shall be cut off and welding shall be conducted again.

9.3.3 Weld joint the time of post-weld heat treatment of which is over 30% of specified

value of instructor on post-weld heat treatment technique and the hardness of which is

checked to be qualified shall be recorded.

10. Technical documents

10.1 Construction of welding heat treatment shall own instructor on on-site heat treatment

job or process card in agreement with evaluation parameters of welding technique and

also own operation records of on-site welding heat treatment, statistical table on the

job of welding heat treatment (the format is shown in Appendix B) and table for quality

evaluation of post-weld heat treatment.10.2 Technical data of welding heat treatment in the technical data of welding turned over

after the completion of the project shall include:

a) Welding heat treatment curve of automatic recording;

b) Statistical table on the job of welding heat treatment;

c) Table for quality evaluation of post-weld heat treatment;

d) Relevant test and detection reports.


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DL/T 819 2010

Appendix A

(Normative Appendix)

Technical conditions for flexible ceramic resistive heater

A.1Flexible ceramic resistive heater is generally composed of resistance wire, ceramic

bushing (chip), outgoing line and accessories, and it may be rope-shaped heater,

crawler flake heater, finger heater, clamp heater, with not more than 1000 of

operating temperature.

A.2 Resistance wire should be made up of Cr20Ni80 alloy material with appropriate single

strand diameter of 0.35mm to 0.4mm, and its quality meets requirements of GB/T 1234.

Stranding No. of piles is preferably 37 to 42, and no joint and broken wire is allowed

when stranding resistance wire.

A.3Ceramic bushing (chip) should be made up of oxide and composite oxide ceramic,

with high thermal emissivity required. Its softening point temperature should be more

than 1200, and dielectric strength more than 20Kv/mm. Requirement for thermal

shock resistance is being indehiscent for three times in 750 when quenched in water

of 25.

A.4Connection of heater outgoing line and resistance wire preferably adopts stainless

steel conduit to connect and suppress, checking whether stainless steel conduit is

burr-free or not before pressure welding; it may also adopt low-resistance alloy welding

material to weld to ensure the quality of joints. Length of each nickel-chromiumresistance wire outgoing line should be not less than 400mm, and length of cooper wire

outgoing line not less than 200mm, sectional area of cooper wire not less than 10mm.

Connector of heater should adopt socket and spigot joint.

A.5Pressure-resistant property of heater should be no breakdown in 1min under 2000V of

alternating current, insulation resistance not less than 100M (below 400), and high

temperature leakage value not more than 0.5Ma/kW (in 750).

A.6Dimension error of effective heating part: rope-shaped heater and finger heater, not

more than 1%; flake heater, not more than 3%.

A.7Cold resistance should be adopted to calculate power of heater in acceptance. The

error between calculated power and rated power should be not more than 5%.

A.8For rope-shaped heater, under operating condition of 750 and 3h, the elongation of

resistance wire after being used for three times should be not more than 0.5%. For

crawler-type heater, select vitrolite of appropriate size according to specification of

heater: both ends of heater should be positioned with appropriate No. of ceramic pieces

with connecting hole, and the location of two ends should be the same. Ends of clamp

heater should have good sealing with heating elements, able to implement requirement

of partition temperature control as required.

A.9 With product qualification and quality certificate, quality certificate should at least

include but not limited to the following contents:a) Filament diameter, No. of piles and quality certificate of resistance wire.


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b) Effective size of heater.

c) Rated operational voltage.

d) Rated power.

e) Cold resistance design.


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DL/T 819 2010

Appendix B

(Informative Appendix)

Operation card for welding heat treatment, operating record for welding

heat treatment, operation statistical table for welding heat treatment

For operation card for welding heat treatment, operating record for welding heat treatment,

operation statistical table for welding heat treatment, refer to Table B.1 ~ B.3.

Table B.1 Operation card for welding heat treatment

Project name No.

Component

nameMaterial

Specification Welded junction No.

Preheat

Heating means Warming rate /h

Preheat

temperature

Bottoming:

Preheating:

Interpass temperature

Temperature

measurement

methods

Heating

measures

Insulation

measures

Postheat

Heating

temperature

Constant temperature

time h

Other

requirements

Post-welding heat treatmentHeating means Warming rate /h Cooling rate /h

Heating width mmInsulation layer

widthmm

Constant

temperature

Constant

temperature timeh

Thermocouple

modelQuantity

Process graph: Notes:

Formation Date Approval Date


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DL/T 819 2010

Page___of____

Table B.2 Operating record for welding heat treatment

Project name: Date: Weather: Ambient temperature:

Component

nameJoint No. Material Specification Heating means

Warming and

cooling rate

/h

Constant

Temperature

Constant

temperature time

h

Process card

No.

Time

h

Temperature

Time

h

Temperature

Record requirements:

1).Operate strictly according to heat

treatment operation instruction or heat

treatment process card.

2). Record carefully, fill in clearly and

completely.

3) Record every other 0.5h.4) Go to the heat treatment site to

inspect at least every other 0.5h.

5) Record ambient temperature every

other 0.3h when continuous operating

hours is longer.

Shift record Abnormal situation

record:Recorder

Successor

Start time

End time


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Table B.3 Table of operation statistics for welding heat treatment

Page

Project name Component name

Serial

No.

Welded

joint No. Material Specification

Heating

means

Heat

treatmentdate

Automatic

recording No.

Heat

treatcategory

Remark

Notes:

(1) The table is counted as per components and in heat treatment date order.

(2) Heating means are expressed as codes: DRelectric heater; GRinduction heating; HRflame heating;

LRfurnace heating.

(3) Heat treatment categories are expressed as codes: PWHTpost-welding heat treatment; POHpostheat;PRHpreheat

Approved by: Counted by:

Date Date


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DL/T 819 2010

Appendix C


Preheating temperature for common steel

Preheating temperature for common steel is shown in table C.1.

Table C.1 Preheating temperature for common steel

Steel specification

Pipe material Plate material

Thickness

mm

Preheat

temperature

Thick

mm

Preheat

temperature

Carbon steel and casting

(carbon content 0.35%)

26 100~200 34

100~150C-Mn (Q345)15 150~200

30

Mn-V (Q390) 28

1.5Mn-0.5Mo-V (14MnMoV,

18MnMoNbg)

15 150~200 15 150~2000.5Cr-0.5Mo (12CrMo)

1Cr-0.5Mo (15CrMo,

ZG20CrMo)

1Cr-0.5Mo-V (12Cr1MoV)

1.5Cr-1Mo-V (15Cr1Mo1V,

ZG15Cr1Mo1V)

2Cr-0.5Mo-W-V

(12Cr2MoWVB)

1.75Cr-0.5Mo-V, 2.25Cr-1Mo

(12Cr2Mo)

3Cr-1Mo-V-Ti

(12Cr3MoVSiTiB), 10CrMo910

6 200~300 8 200~300

15NiCuMoNb5 (WB36),

15MnNbMoR

20 150~200 20 150~200

07Cr2MoW2VNbB (T/P23) 13 150~200 13 150~200

1Cr5Mo, 15Cr13 (1Cr13) Arbitrary 250~300 Arbitrary 250~300

9Cr-1Mo (T/P9), 12Cr-1Mo-V Arbitrary 300~350 Arbitrary 300~350

10Cr9Mo1VNbN (T/P91) Arbitrary 200~250 Arbitrary 200~250

10Cr9MoW2VNbBN (T/P92) Arbitrary 200~250 Arbitrary 200~250

10Cr11MoW2VNbCu1BN

(T/P122)

Arbitrary 200~250 Arbitrary 200~250


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Note 1: The temperature (which is indicated in the table) is the confirmed minimum reheating

temperature according to the wall thickness. When take the backing with the argon arc

welding, the preheating can be taken on the temperature which is 50 lower than the

low limited temperature.

Note 2: For the low-content-alloy pipes and pipe fittings (which thickness is greater than or equal

to 6mm), the large-thickness plates should be welded below 0and it should be 20

~40 higher than the lowest preheating temperature. For the low-content-alloy pipes

(which thickness is smaller than 6mm) and the carbon steel (which thickness is larger than

15mm), it should be welded below 0 and proper preheating should be taken.

Note 3: When welding the bearing components and non-bearing components, preheating should

be taken as the bearing components. When welding the sleeves and main pipe,

preheating should be taken as the main pipe.

Note 4: Upper limit value of preheating temperature in the table also can be understood as upper

limit of welding layer temperature


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Appendix D


Post-welding heat treatment temperature and time for common steelRefer to Table D.1 for post-welding heat treatment temperature and time for common

steel

Table D.1

Post-welding heat treatment temperature and time for common steel

Steel specificationTemperature

Welding piece thickness (mm)

12.5 12.5~25 25~37.5375

~50

50~7

575~100

100~12

5

Constant-temperature time (h)

C0.35% 20, ZG25

C-Mn (Q345)580~620

Not necessaryfor heat

treatment

1.5 2 2.25 2.5 2.75

15NiCuMoNb5 (WB36)

15MnNiMoR580~620 1 2 2.5 3 4 5

0.5Cr-0.5Mo (12CrMo) 650~700 0.5 1 1.5 2 2.25 2.5 275

1Cr-0.5Mo (15CrMo,

ZG20CrMo)670~700 0.5 1 1.5 2 2.25 2.5 2.75

07Cr2MoW2VNbB

(T/P23)

720~740 0.5 1 1.5 2 3 4 5

1Cr-0.5Mo-V

(12Cr1MoV,

ZG20CrMoV)

1.5Cr-1Mo-V

(ZG15Cr1Mo1V)

1.75Cr-0.5Mo-V

2.25Cr-1Mo

720~750 0.5 1 1.5 2 3 4 5

1Cr5Mo, 15Cr13 (1Cr13) 720~750 1 2 3 4

2Cr-0.5Mo-WV(12CrMoWVTiB)

3Cr-1Mo-V-Ti

(12Cr3MoVSiTiB)750~770

0.75 1.25 2.5 4

9Cr-1Mo (T/P9)

12Cr-1Mo (X20)1 2 3 4 5

10Cr9Mo1VNbN (T/P91) 750~770 1 2 3 4~5 5~6 6~7 8

10Cr9MoW2VNbBN

(T/P92)750~770 1.5 2 4 5~6 6~7 8~9 10

10Cr11MoW2VNbCu1BN(T/P122)

740~760 2 4 5~6 6~7 8~9 10


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a. For tube socket or re-welding pieces, the constant temperature time is decided by nominal thickness of

welding pieces instead of welding pieces thickness, but should not be less than 0.5h. See 6.4.3 for

computing method.

b. For that without marked constant temperature time, calculate according to computing method specified in

6.4.3.


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