This part of GB/T 16508 specifies material designation and its standard, basic technical requirements (including steel plate, steel tube, steel forging, steel casting, iron casting, suspender and tension brace, fastener and welding material), application scope (temperature and pressure) and permissible stress allowed to be used for pressure part of shell boiler, as well as material designation and its standard allowed to be used for non-pressure part of shell boiler.
This part is applicable for selection and application of materials for pressure parts and non-pressure parts of the shell boiler as defined in GB/T 16508.1
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated reference, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
3.1.1 During material selection, operating conditions (temperature, pressure and environment etc.), material property (mechanical property, process property, chemical property and physical property etc.), fabrication process and economic rationality shall be taken into consideration.
3.1.2 Material specified in this part shall be selected as pressure parts, and material meeting the requirements of GB/T 16507.2 may also be selected, with its application scope of temperature and pressure meeting the requirements of this part and its property meeting the specified standard requirements.
3.1.3 Where material not specified in this part is selected as pressure part, material listed in national and professional standard is allowed to be used, but its property shall not be lower than the requirement of this part or that for material with near designation listed in the material standard of this part.
3.1.4 Foreign designation material selected as pressure part shall be the material applied maturely for pressure equipment at home and abroad, besides, it shall be in accordance with the relevant requirements of "Boiler Safety Technical Supervision Administration Regulation" (TSG G0001).
3.1.5 Where non-pressure part (lifting lug, fin and baffle etc.) and pressure part are welded together, the material selected shall be matched with the material to be connected.
3.2 Material substitution
Selection for boiler substitute material shall meet the requirements of 3.1. Material substitution shall meet the requirements of strength, structure and technology of original design and shall be agreed by the technical departments (including design and technology departments) of the material substitution organization.
3.3 Quality certificate
Steel for pressure part shall be accompanied with material quality certificate of material fabrication organization. The material quality certificate shall meet the following requirements:
a) The material fabrication organization shall provide the user with the original quality certificate as specified in the material standard and the order contract; and shall provide distinct and firm steel stamp or other marking on the obvious part of material. The material quality certificate shall be complete and distinct in contents and shall be stamped with the quality inspection seal of the material fabrication organization;
b) Where the boiler material is not directly supplied by the material fabrication organization, the supplier shall provide the original material quality certificate or its copies with its official seal and signature of its operator.
3.4 Material acceptance
The boiler fabrication organization shall carry out acceptance according to material quality certificate, and the material may only be used after being regarded as acceptable. Foreign designation material shall be accepted according to the technical standards and technical conditions specified in order contract, the lacking inspection item in boiler material standard in China shall be redone where necessary, and it may only be used after being regarded as acceptable.
Physicochemical and corresponding non-destructive testing and re-inspection may be omitted for the material under any of the following conditions:
a) The acceptance personnel of the material using organization carries out acceptance at the material fabrication organization’s according to the procurement technical requirements and make a witnessed signature on the inspection report for confirmation;
b) The carbon steel plate, tube and welding material for boiler under pressure below 3.8MPa shall be provided with distinct and complete physical mark and material quality certificate in accordance with the specified requirements. In addition, the quality certificate shall conform to the physical object.
3.5 Basic requirements
3.5.1 Steel for pressure part and steel for non-pressure part welded to pressure part shall be killed steel.
3.5.2 For the steel plate, steel tube, steel forging and round steel for suspender etc. for pressure part, where they are made by rolling and forging with steel billet casting (including ingot casting and continuous casting billet), their compression ratio shall not be less than 3.
3.5.3 After tensile test is carried out on standard specimen of steel (steel plate, steel tube, steel forging and its welded joints etc.) for pressure part, the post-fracture percentage elongation (A) of the steel shall not be less than 18%; impact absorbed energy value Kv2 obtained from V-shaped Charpy impact test shall not be lower than 27J.
3.5.4 Permissible stress of steel for pressure part is determined according to the principle of GB/T 16508.1. Permissible stress value between two adjacent calculating temperatures listed in permissible stress table may be determined through arithmetic interpolation method, and its value is rounded off as an integer.
3.5.5 Under use conditions, welding material shall be provided with enough strength, plasticity, toughness and favorable anti-fatigue property and corrosion resistance property.
3.5.6 See Appendix B for non-proportional elongation strength value (Rp0.2) of steel at high temperature, mean value of 105h endurance strength, elasticity modulus and mean linear expansion coefficient, etc.
4 Steel Plate
4.1 Application Scope for common steel plate is in accordance with those specified in Table 1.
4.2 Permissible stress of the steel plate material is in accordance with those specified in Table 2.
4.3 Where heat treatment like normalizing and normalizing plus tempering are needed to be carried out on steel plate material during boiler fabrication, steel plate fabrication organization may deliver steel plate with its delivery state different from the heat treatment specified in Table 2. Where the steel plate fabrication organization and the boiler fabrication organization carry out delivery inspection and receiving acceptance for mechanical property of steel plate respectively, rough specimen after heat treatment is used for the test.
4.4 For 20 steel plate purchased according to GB/T 711, the lower yield strength value (ReL) specified in its material quality certificate or after receiving re-inspection for tensile test shall not be less than 245MPa.
4.5 13MnNiMoR steel plate above 36mm in thickness may additionally be subject to drop-weight test according to GB/T 6803 and the acceptable index of nil-ductility transition temperature (NDT) is specified in the design document .
4.6 For steel plate with the design calculating temperature above 300℃, an high-temperature tensile test at the design calculating temperature may be additionally required in the design document and shall comply with GB/T 4338; see Appendix B for the specified value of non-proportional elongation strength at high temperature Rp0.2.
4.7 The steel plate for boiler shell, boiler furnace and header end cover shall be subject to ultrasonic testing piece by piece according to JB/T 4730.3. Quality grade: for Q245R and Q345R steel plates, where the thickness>30~36mm, it is not lower than Grade III; where the thickness>36mm, it not less than Grade II; for other steel plate(s), it is not less than Grade II.
Foreword I 1 Scope 2 Normative References 3 General Requirements 4 Steel Plate 5 Steel Tube 6 Steel Forging 7 Steel Casting 8 Iron Casting 9 Suspender and Tension Brace 10 Fastener 11 Welding Material Appendix A (Informative) Metallographic Inspection for Steel forging Appendix B (Informative) High-temperature Property of the Common Material
