Stainless steel valve rust causes and solutions

Stainless steel valve rust causes and solutions

This standard specifies the chemical composition, mechanical properties, technical requirements, testing and inspection of stainless steel castings for general purpose valves. This standard applies to stainless steel castings such as pressure valves, flanges and pipe fittings used in high temperature and corrosive environment. The casting producer shall make a chemical composition analysis at each furnace to determine the specified element content. In the analysis, the test blocks poured in the same furnace shall be used. When drilling cuttings are sampled, they should be taken from at least 6.5mrr: below the surface. The analysis results shall comply with the requirements of Table 1 and be reported to the Demander or its **.
1 Range
This standard specifies the chemical composition, mechanical properties, technical requirements, testing and inspection of stainless steel castings for general purpose valves. This standard applies to stainless steel castings such as pressure valves, flanges and pipe fittings used in high temperature and corrosive environment.
2 Normative reference documents
The terms in the following documents become terms of this Standard by reference to this Standard. For dated citations, all subsequent amendments (excluding errata) or amendments are not applicable to this Standard, however, parties to agreements under this Standard are encouraged to explore the use of versions of these documents. For undated references, their versions are applicable to this standard.
Sample sampling method for chemical analysis of GB/T 222 steel and permissible deviation of finished chemical composition
GB/T 223 (all parts) steel. And chemical analysis method of alloy
GB/T 228 Metallic materials — Tensile test method at room temperature (GB/T 228-2002,cqv ISO 6892:199R)
GB/T 2100 Corrosion-resistant Steel Castings for General Purpose (GB/T 2100-2002,eqv ISO11972:1998)
GB/T 1334 (all parts) Corrosion test methods for stainless steel
GB/T 5613 cast steel grade. Method of representation
GB/T 5677 Cast steel — Method for Classification of radiographs and negatives (GB/T 56771985, neq JCSS G2)
Dimensional tolerances and Machining allowances for Castings (GB/T 6414-1999,eqv ISO 8062:1994)
Standard for ultrasonic flaw detection and quality rating of steel castings GB/T7233 — a 1987.neq BS 6208:1982)
GB/T 9443 steel castings – Grading method for penetration testing and defect showing marks
GB/T 9452 heat treatment furnace — determination of effective heating zone
GB/T 11351 casting weight tolerance
GB/T 13927 General valve pressure test (GB/T 13927-1 1992,neq ISO 5208 1982)
GB/T 15169 steel fusion welding welder skill assessment periodic (GB/T 15169-2003,ISO/DIS 9606-1.>
Welding process evaluation of JB/T 4708 steel pressure vessel
JB/T 7927 valve steel castings appearance quality requirements
ASTM A351/A351M:2000 Specification for Austenitic, Austenitic Ferritic (Biphasic) Steel Cast for Bearing Parts
3 Technical Requirements
3.1 Casting
The steel shall be smelted by electric arc furnace, induction furnace or other secondary refining methods, which shall be determined by the casting producer.
3.2 Casting steel type and chemical composition
3.2.1 The chemical composition of the casting shall comply with the provisions of Table 1.
3.2.2 Chemical analysis
3.2.2.1 Smelting Furnace sub-analysis Casting producers should make chemical composition analysis for each sub-furnace to determine the specified element content. In the analysis, the test blocks poured in the same furnace should be used. When drilling cuttings are sampled, they should be taken from at least 6.5mrr: below the surface. The analysis results shall comply with the requirements of Table 1 and be reported to the Demander or its **.
3.2.2.2 Analysis of Finished products Analysis of finished products can be made by the demander itself, from each furnace, each batch or each casting sample of its perfect. When drilling cuttings are sampled, they should generally be taken from at least 6.5mm below the surface, and when the thickness of the casting is less than 12mm, the central part should be taken. The analysis results shall comply with the provisions of Table 1, and the allowable deviation of the analysis shall comply with the provisions of GB/T222. The permissible deviation of finished product analysis can not be used as the acceptance basis of casting factory.
3.2.2.3 Arbitration Analysis
The sampling method of chemical analysis shall follow the regulations of (}B/T 222, and the arbitration analysis of chemical composition shall follow the regulations of GB/T 223.
3.3 Mechanical Properties
The mechanical properties of the castings shall conform to the stipulations in Table 2.
3.4 Heat Treatment
Heat treatment should meet the requirements of Table 2, heat treatment furnace with high temperature instrument, according to the provisions of GB/T 9452 effectively control the furnace temperature.
3.5 Quality Requirements
3.5.1 Casting size
Castings shall conform to the requirements of shape, size and deviation of drawings and models provided by demander. If the drawing is not indicated. The size deviation requirements shall conform to the requirements of the corresponding casting accuracy grade of GB/T 6414; The casting weight tolerance shall comply with GB/T 11351.
3.5.2 Casting surface
The surface of castings shall be inspected in accordance with JB/T 7927 and the requirements of the order contract. There shall be no surface defects such as sand, oxide skin and cracks.
3.5.3 Welding repair
3.5.3.1 Welders of welding repair castings shall pass the examination according to the requirements of (GB/T 15169) and have corresponding qualification certificates. Welding process assessment shall be carried out according to the requirements of JB 4708.
3.5.3.2 Casting with any of the following defects is not allowed to be repaired:
a) Defects that are not allowed to be repaired according to the drawings or the order contract;
b) Those with honeycomb pores;
c) Pressure test leakage of finished products and the quality cannot be guaranteed after welding repair;
d) The welding repair times of the same part shall not exceed 2 times.
1 2 next page stainless steel valve rust causes and solutions
One, stainless steel valve rust reasons
Research whether the stainless steel valve can rust, you can first place the same valve in a different environment to verify the comparison, generally speaking, if the stainless steel valve is placed in a relatively dry environment, after a long time, the valve is not only good as new, but also no rust, but if the valve is placed in the seawater containing a lot of salt, not a few days will rust, It can be seen that the corrosion resistance and rust resistance of stainless steel valves also need to be limited by the use of environment. In addition, from the characteristics of the stainless steel valve itself, it is not rust because there is a layer of chromium-rich oxide film on the surface to prevent the external oxygen atoms and other particles caused by the invasion of damage to the object, so that it has the characteristics of rust, but when the film is damaged by environmental factors, as oxygen atoms into the free iron ions, stainless steel valve will produce rust.
There are many reasons for the destruction of stainless steel valve surface film, resulting in rust, some film and other metal element particles or dust electrochemical reaction, at the same time with the moist air as a medium, the formation of a micro battery cycle, making stainless steel surface rust, can also be stainless steel surface film directly in contact with acid, alkali and other corrosive liquids, caused by corrosion, etc. Therefore, in order to stainless steel valve rust, in daily use should also pay attention to the cleaning of objects, keep the valve surface clean.
Two, stainless steel valve rust solution
So how do you make sure the surface of the metal is always bright and not corroded? Sanjing Valve Manufacturing Co., LTD. Professional and technical personnel suggestions:
1. It is necessary to clean and scrub the decorative stainless steel surface frequently, remove attachments and eliminate external factors that cause modification.
2. The seaside area should use 316 stainless steel, 316 material can resist seawater corrosion.
3. The chemical composition of some stainless steel tubes on the market can not meet the corresponding national standards, up to 304 material requirements. Therefore, it will also cause rust, which requires the user to carefully choose the product construction of reputable manufacturers and construction points of attention in order to prevent the construction of scratches and pollutants attached, stainless steel construction under the state of film. But with the extension of time, the residual paste liquid in accordance with the service life of the film, after the construction of the film should be removed when the surface washing, and the use of stainless steel tools, and general steel cleaning public tools, in order not to let the iron chips stick should be cleaned. Attention should be paid to prevent the highly corrosive magnetic and stone luxury cleaning drugs from coming into contact with the stainless steel surface, if contact should be immediately washed. After the construction, neutral detergent and water should be used to wash the cement, powder and ash attached to the surface.