This standard specifies the requirements for plasma surfacing of valve sealing surfaces on welders, surfacing materials, commonly used base materials, surfacing processes, quality inspection, defect repair, etc. This standard is applicable to the manufacturing and inspection of plasma arc surfacing cobalt-based, nickel-based, iron-based alloy powder materials for carbon steel, alloy steel, stainless steel and other general, power station, and petrochemical valve sealing surfaces. JB/T 6438-1992 Technical requirements for plasma arc surfacing of valve sealing surfaces JB/T6438-1992 Standard download and decompression password: www.bzxz.net

Mechanical Industry Standard of the People's Republic of China
Plasma arc cladding of valve sealing surface
Technical requirements
Subject content and scope of application
JB/T 6438-92
This standard specifies the requirements for welders, cladding materials, common base materials, cladding technology, quality inspection, defect repair, etc. for plasma arc cladding of valve sealing surface.
This standard is applicable to the manufacture and inspection of plasma arc cladding-based, nickel-based, and iron-based alloy powder materials for general-purpose, power station, and petrochemical valve sealing surfaces such as carbon steel, alloy steel, and stainless steel. 2 Reference standards
JI3 3168
Technical conditions for spray-welded alloy powders
Determination of hardness and particle size of spray-welded alloy powders
JB 3169
Chemical composition analysis method of spray welding alloy powder JB3170
3 Welders
Welders should pass the basic knowledge part of the "Boiler Pressure Vessel Welder Examination Rules" formulated by the Ministry of Labor of the People's Republic of China and pass the professional training and examination of plasma arc welding. 4 Welding materials
4.1 The chemical composition, hardness of the cladding layer, particle size, etc. of the cladding alloy powder (hereinafter referred to as powder) material shall comply with the relevant provisions in JB3158.
4.2 The selection of powder materials other than JB3168 shall be determined by negotiation between the supply and demand parties. However, its inspection method shall be in accordance with the provisions of JB3168 and 1331G9. 4.3 The quality of the powder material shall comply with the requirements of the relevant technical documents and be accompanied by a quality certificate issued by the inspection department of the powder manufacturer. 4.4 Each batch of powder shall be subjected to process tests and chemical composition re-inspections before use. The chemical composition analysis method shall be in accordance with the provisions of J33170. 4.5 Powder The powder should be dried before use, and the thickness of the powder should be less than or equal to 5mm during drying. The drying temperature is as specified in Table 1. Powder type Cobalt-based Nickel-based Iron-based Drying temperature, (150-250 °C 120-250 °C Holding time, h 0.5-1.5 °C 4.6 The dried powder is placed in air If it is placed in the water for more than 4 hours before use, it should be re-dried. The drying frequency should not exceed twice. 5 Commonly used matrix materials
25, 35, 40
WCB.ZG1Cr18Ni9Ti, ZG1Cr18Ni9, ZGCr5Mo, ZG20CrMoV Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on July 20, 1992 146
Implemented on January 1, 1993
JB/T 6438—92
1Cr5Mo,12CrMo,15CrMo,12Cr1MoV,15Cr1MoV,WC6,WC91Cr13,2Cr13,1Cr18Ni9,1Cr18Ni9Ti.1Cr18Ni12Mo2Ti6 Surfacing process
6.1 Size of surfacing base surface (process platform)
6.1.1 According to the different requirements of the valve sealing surface, the surfacing base surface can be processed into any of the three shapes shown in Figure 1 (it can also be a plane). The size is shown in Table 2.
Convex
Design width of sealing surface B
mm
10
>10
Note: α can also be 90°
Tai
mm
B+(35)
B+(3～6)
Guo
Slot
Figure 1
Shape and size of cladding surface
Table 2
mm
1.5～2
30°~~45°
6.1.2 The cladding surface shall be machined by mechanical cutting method, and all transitions shall be rounded and smooth. 6.2 Requirements for weldments
6.2.1 There shall be no defects such as cracks, pores, shrinkage cavities, looseness, etc. 6.2.2 Oil, burrs, rust and other debris must be removed. 6.3 Preheating before welding
6.3.1 When the selected powder type and base material have preheating requirements, preheating is required for cladding iron-based powder. Limit
Angle
mm
1. 5 -- 2
..
6.3.2 Preheating of diamond-based and nickel-based powders is required except for carbon steel weldments with a nominal diameter less than or equal to 25mm (excluding deep hole small diameter weldments).
6.3.3 The preheating temperature is determined by the chemical composition of the material. Parts for batch cladding should be preheated in the furnace. The preheating temperature of commonly used base materials is shown in Table 3. The preheating temperature of workpieces with large structural rigidity shall be taken as the upper limit. 6.3.4 The preheating and heat preservation time shall be determined according to the size and shape of the workpiece. 6.4 The protective device shall be checked before welding to ensure that the operation can be carried out only when it is safe and reliable. 6.5 Process evaluation test
The process evaluation test shall be organized and carried out by the responsible process engineer and operated by the welder who meets the requirements of Chapter 3. The quality inspection department shall participate in the evaluation. 6.5.1
6.5.2
a.
b.
c.
Whenever any of the following situations occurs, a process evaluation test must be carried out: the first use of powder varieties;
the first use of base materials;
new product specifications and structural types.
The process evaluation test... shall generally be carried out on the product. When the powder is used for process evaluation, 6.5.3 can be carried out on the corresponding test block.
117
25
35
40
WCB
Matrix material
ZGCt5Mo
ZG20Cr5MoV
ZGICr318Ni9
ZG1Cr18Ni9Ti
12CrMo
l5CrMo
1Cr5Mn
12CrMo, wc6
15Cr1MoV,WC9
10r13
20113
1Cr18Ni9
ICr18Ni9Ti
ICr18Ni2Ma2Ti
6.5.4
a.
b.
c.
.
e .
6.5.5
b.
Preheating temperature before welding, C
Coal-based Nickel-based
250-~300
310-350
250~350
400~500
100~550
300~-400
Iron-based
JB/T 6438-92
Table 3
Post-weld heat treatment temperature, C
!Cobalt-basedNickel-based
600-650
Iron-based
300-350
650-700
600~700
350~400
350450
250--350
400～500
350~400
40:0- 500
400-~500 :350~450
740-760
700~790
860~880
680~710
700--740
720~760
710~750 / 700-~740
700-750
300~350250~300
300～400
250~~350
700--760
860~880
860880
1 050~1 100
Post-weld heat treatment
Hot-holding time
h=7/25
Cooling method
Furnace cooling (small parts
Shanghai asbestos cooling)
Where.-Hot-holding time h;
Base material thickness.
mrm
Can internal slow-down
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Through the process evaluation test and the factory production conditions, the following optimal process parameters are determined: cladding specification;
Pre-weld heat treatment temperature and its hot-holding time: minimum thickness of the cladding layer, minimum thickness of the transition layer; post-weld heat treatment temperature, hot-holding time and cooling curve; if necessary, correct the shape and size of the cladding base surface. The qualified quality standard of the process evaluation test is: it should meet the requirements of Sections 7.2, 7.3, 7.4; dissect the test piece and inspect the welding section. There should be no incomplete penetration on the entire section. The process evaluation test report and its qualified conclusion should be documented and filed, and the process card of the production site should be formulated or revised based on it. 6.5.6
6.6 Overlay welding transition layer
6.6.1 When the base material is CrMo alloy steel, the transition layer can be overlaid when the nominal diameter is greater than or equal to 150mm. 6.6.2 The transition layer material should be selected from 18-8 type and 25-20 type stainless steel welding materials to prevent cracks and improve joint performance. 6.6.3 The thickness of the transition layer after machining should be greater than or equal to 2mm. 6.7 Overlay welding process
6.7, 1 Strictly follow the process specifications proposed by the qualified process evaluation test 6.7.2
6.7.3
6. 7. 4
Overlay welding should avoid being carried out in an environment with severe dust and humidity greater than or equal to 84%. During the cladding process, the interlayer temperature of the weldment shall not be lower than the lower limit of the preheating temperature. If necessary, the interlayer needs to be heated again. The cladding height and width should ensure that the sealing surface meets the design requirements after work. The value should comply with the provisions of Table 4. Table 4
Nominal diameter IDN
150
150
Note: H. Design height B
148
Design width.
Height of sealing surface welding
H+(1-~2)
211+(1. 5~2.5)
Width of sealing welding
2h+(3-~5)
2B--(3. 5~~6)
mm
6.8 Heat treatment after welding
JB/T 6438—92
6.8.1 After welding, the workpiece should be immediately put into the furnace for heat treatment according to the provisions of Table 3. 6.8.2 When the selected powder and base material require post-weld heat treatment, heat treatment is required. 6.8.3 When using cobalt-based and nickel-based powders for welding carbon steel workpieces with a nominal diameter less than or equal to 25mm (excluding deep hole small-diameter weldments), heat treatment is not required.
7 Quality Inspection
7.1 Appearance Inspection
7.1.1 Check visually or with a 5~~10x magnifying glass. The surface of the cladding layer shall not have defects such as cracks, pores, shrinkage, and looseness. There shall be no incomplete penetration on the side of the cladding layer.
7.1.2 The weldment must ensure geometric dimensions, deformation within the allowable range, and sufficient processing allowance. 7.2 After machining, the cladding surface shall be inspected by color flaw detection method. There shall be no defects such as cracks, pores, looseness, slag inclusions, and incomplete penetration. -Generally, the inspection quantity of each batch of valves 1 is 3%, but not less than 10. If one of the samples is unqualified, double sampling inspection shall be carried out. Valves with high quality requirements shall be inspected 100%.
7.3 Hardness test can be carried out on the circumference of the annular sealing surface using products or standard samples according to JB3169. The hardness value shall meet the requirements of the powder technical conditions and product drawings
7.4 The thickness of the cladding layer after fine processing of the cladding workpiece shall not be less than 2mm. 8 Defect repair
8.1 Defects can be repaired, and the same defect can be repaired twice at most. 8.2 Defects such as pores, slag inclusions, loose joints and shrinkage cavities can be removed. Cracks and unfinished parts must be removed until the parent metal is exposed. After removal, the bottom should be an appropriate round arc shape. Its dimensions are shown in Figure 2. Porosity
90
R
Shrinkage. Loose
>90°-
R
Crack
>90°
Weld cladding layer
Base material
R
Figure 2 Defect removal requirements size
8.3 When removing defects, strong impact force shall not be directly applied to the cladding part. Welding repair can only be carried out after confirming that the defects have been completely removed by the color flaw detection method.
8.4 If the defects are numerous, continuously distributed and over a large area, the weld overlay should be removed and re-welded. 8.5 Welding repair can be carried out by manual arc welding, oxyacetylene welding or inert gas shielded welding. 8.6 Welding repair shall be performed by welders who have passed the examination and shall be carried out in accordance with the welding repair process code. 8.7 After welding repair, it shall be inspected in accordance with the relevant provisions in Chapter 7 of this standard. Additional notes:
This standard was proposed and coordinated by the Hefei General Machinery Research Institute of the Ministry of Machinery and Electronics Industry. This standard was drafted by the Hefei General Machinery Research Institute of the Ministry of Machinery and Electronics Industry, and the main drafter of this standard was Xu Fenglan.
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7 After welding repair, inspection shall be carried out according to the relevant provisions in Chapter 7 of this standard. Additional notes:
This standard is proposed and administered by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronics Industry. This standard is drafted by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronic Industry. The main drafter of this standard is Xu Fenglan.
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7 After welding repair, inspection shall be carried out according to the relevant provisions in Chapter 7 of this standard. Additional notes:
This standard is proposed and administered by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronics Industry. This standard is drafted by the Hefei General Machinery Research Institute of the Ministry of Mechanical and Electronic Industry. The main drafter of this standard is Xu Fenglan.
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