Technological method for surfacing stainless steel on sealing surface of valve body of nodular cast iron butterfly valve

Abstract

The invention relates to the technical field of valve manufacturing, and discloses a process method for surfacing stainless steel on a sealing surface of a nodular cast iron butterfly valve body, which solves the problems in the background art, a valve body sealing ring is cancelled, the sealing surface of the nodular cast iron butterfly valve body is obtained in a surfacing manner, the base material of the valve body is QT450-10, and the surface of the valve body is made of stainless steel. The sealing face is made of austenitic stainless steel or duplex stainless steel, the welding method is flux-cored wire gas shielded welding, a traditional sealing ring is omitted, the sealing face is directly overlaid on the valve body, the structure is simplified, and the sealing performance and reliability are improved. The structure is more reliable, the service life is prolonged, the production process is simplified, quality consistency is ensured through semi-automatic welding, manual intervention errors are reduced, and the market competitiveness of products is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of valve manufacturing, and specifically relates to a process method for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body. Background Technique

[0002] Ductile iron butterfly valves are generally widely used in the water supply industry, thermal power plants, nuclear power plants, and petrochemical industries, and are usually used to control the on-off of fluids or control the flow rate. For the production of ductile iron butterfly valves, which are widely used in the field of fluid control, the traditional production process uses a mechanical connection method (bolting the valve body sealing ring) to form the sealing surface.

[0003] However, this method has the following defects: complex process: the valve body and the sealing ring need to be processed separately, and then combined through processes such as matching turning, drilling, and assembly; long production cycle and material waste: a large amount of machining allowance needs to be reserved for the sealing ring, and the use of stainless steel materials is costly; insufficient reliability: bolt connection is prone to seal failure due to the attenuation of the pre-tightening force and requires frequent maintenance. Therefore, we propose a process method for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body. Summary of the Invention

[0004] In order to solve the problems raised in the background technique, the present invention provides the following technical solution: a process method for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body, which cancels the valve body sealing ring and obtains the sealing surface of the ductile iron butterfly valve body by surfacing. The valve body base material is QT450-10, and the sealing surface material is made of austenitic stainless steel or duplex stainless steel. The welding method is flux-cored wire gas shielded welding. By canceling the traditional sealing ring and directly surfacing the sealing surface on the valve body, the structure is simplified, and the sealing performance and reliability are improved.

[0005] Preferably, the welding consumables used are GFS-309L austenitic flux-cored stainless steel wire (φ1.2mm) or GFS-2209 duplex steel flux-cored stainless steel wire (φ1.2mm), ensuring the stability of welding quality and process.

[0006] Preferably, the shielding gas during welding is 100% CO2, the preheating is at room temperature without preheating, and the interpass temperature ≤ 250°C. By controlling the shielding gas, preheating conditions, and interpass temperature, the welding process is further optimized, ensuring the welding quality and the performance of the sealing surface.

[0007] Preferably, the post-weld treatment is slow cooling of the surfacing layer covered with asbestos. The surfacing thickness is 4mm, and finally 2mm thickness is reserved for machining. By specific post-weld treatment and control of the surfacing thickness, the quality and performance of the surfacing layer are ensured, and problems such as cracks caused by welding stress are avoided.

[0008] Preferably, the welding equipment includes a positioner, a cross manipulator and a gas shielded welding machine to achieve semi-automatic welding. By using specific welding equipment and achieving semi-automatic welding, the production efficiency and the stability of welding quality are improved, and the errors caused by manual operation are reduced.

[0009] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0010] In the above solution, the method of combining flux-cored wire gas shielded welding with a manipulator is used to achieve semi-automatic surfacing. The welding amount is minimized to reduce the stress caused by welding, thereby avoiding the generation of cracks. The final machined thickness of the surfaced sealing surface is reserved at 2 mm, ensuring that only one layer of surfacing is used during surfacing, thus avoiding cracks caused by stress due to excessive welding amount. The workpiece is not preheated before surfacing. Under the actual working conditions of this project, the workpiece needs to be placed on the positioner for semi-automatic welding later. If preheating is carried out first, it will face two major problems: it is difficult to effectively maintain the preheated temperature and the heat distribution on the positioner is difficult to be uniform. This is likely to cause problems such as stress concentration due to temperature differences during subsequent welding. These adverse factors not only cannot improve the welding quality, but are very likely to have a negative impact on the welding effect. Using flux-cored wire for surfacing has the characteristics of good processability, strong adaptability, stable quality, low heat input, high production efficiency, etc. It can meet the requirements of cast iron surfacing to the greatest extent under the existing welding conditions of the company. By using the method of combining a manipulator with a positioner to achieve semi-automatic surfacing, after the workpiece is manually clamped, the welding parameters are set and then automatic surfacing can be carried out, avoiding the instability of product quality caused by parameter fluctuations and quality differences caused by manual operation. The traditional mechanical connection sealing ring is cancelled, and the sealing surface is directly formed by surfacing, making the structure more reliable, the service life extended, the production process simplified, the semi-automatic welding ensures quality consistency, reduces manual intervention errors, and enhances the market competitiveness of the product. Description of the Drawings

[0011] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0012] Figure 1 is a schematic structural diagram of the prior art;

[0013] Figure 2 is a schematic structural diagram of the present invention;

[0014] In the figure: 1, valve body; 2, valve body sealing ring; 3, surfaced sealing surface. Detailed Embodiments

[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0016] As Figure 1-2 shown, the present invention cancels the valve body sealing ring and obtains the sealing surface of the ductile iron butterfly valve body by surfacing. The valve body base material is QT450-10, the sealing surface material is made of austenitic stainless steel or duplex stainless steel, and the welding method is flux-cored wire gas shielded welding. The traditional sealing ring is cancelled, and the sealing surface is directly surfaced on the valve body, which simplifies the structure and improves the sealing performance and reliability.

[0017] The welding consumables used are GFS-309L austenitic flux-cored stainless steel wire (φ1.2mm) or GFS-2209 duplex steel flux-cored stainless steel wire (φ1.2mm), ensuring the stability of welding quality and process.

[0018] During welding, the shielding gas is 100% CO2, the preheating is at room temperature without preheating, and the interpass temperature ≤ 250°C. By controlling the shielding gas, preheating conditions and interpass temperature, the welding process is further optimized, ensuring the welding quality and the performance of the sealing surface.

[0019] The post-weld treatment is to cover the surfacing layer with asbestos for slow cooling. The surfacing thickness is 4mm, and finally 2mm thickness is reserved for machining. Through specific post-weld treatment and surfacing thickness control, the quality and performance of the surfacing layer are ensured, avoiding problems such as cracks caused by welding stress.

[0020] The welding equipment includes a positioner, a cross manipulator and a gas shielded welding machine to achieve semi-automatic welding. By using specific welding equipment and achieving semi-automatic welding, the production efficiency and the stability of welding quality are improved, and the errors caused by manual operation are reduced.

[0021] Working principle: In the above solution, the semi-automatic surfacing is realized by combining the flux-cored wire gas shielded welding with the manipulator, minimizing the welding amount to reduce the stress caused by welding, thereby avoiding the generation of cracks. The final machined thickness of the surfacing sealing surface is reserved at 2 mm, ensuring that only one layer of surfacing is used during surfacing, thus avoiding cracks caused by stress due to excessive welding amount. The workpiece is not preheated before surfacing. Under the actual working conditions of this project, the workpiece needs to be placed on the positioner for semi-automatic welding later. If preheating is carried out first, there will be two major problems: it is difficult to effectively maintain the preheated temperature and it is difficult to make the heat distribution uniform on the positioner. This is likely to cause problems such as stress concentration due to temperature differences during subsequent welding. These adverse factors not only cannot improve the welding quality but are very likely to have a negative impact on the welding effect. Surfacing with flux-cored wire has the characteristics of good processability, strong adaptability, stable quality, low heat input, and high production efficiency. It can meet the requirements of cast iron surfacing to the greatest extent under the existing welding conditions of the company. By combining the manipulator with the positioner, semi-automatic surfacing is achieved. After the workpiece is manually clamped, the welding parameters are set and then automatic surfacing can be carried out, avoiding the instability of product quality caused by parameter fluctuations and quality differences due to manual operation. The traditional mechanical connection sealing ring is cancelled, and the sealing surface is directly formed by surfacing, making the structure more reliable, extending the service life, simplifying the production process, ensuring quality consistency in semi-automatic welding, reducing manual intervention errors, and enhancing the market competitiveness of the product.

[0022] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device.

[0023] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A process for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body, characterized in that: The valve body sealing ring is eliminated, and the sealing surface of the ductile iron butterfly valve body is obtained by surfacing welding. The valve body base material is QT450-10, the sealing surface material is made of austenitic stainless steel or duplex stainless steel, and the welding method is flux-cored gas shielded welding.

2. The process for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body according to claim 1 is characterized in that: The welding material used in the welding is GFS-309L austenitic flux-cored stainless steel welding wire (φ1.2mm) or GFS-2209 duplex steel flux-cored stainless steel welding wire (φ1.2mm).

3. The process for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body according to claim 2 is characterized in that: The protective gas during welding is 100% CO2, the preheating is at room temperature, and without preheating, the interlayer temperature is ≤250°C.

4. The process for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body according to claim 3 is characterized in that: The post-weld treatment is asbestos covered cladding layer and slow cooling, the cladding thickness is 4 mm, and the final processing retains a thickness of 2 mm.

5. The process for surfacing stainless steel on the sealing surface of a ductile iron butterfly valve body according to claim 4 is characterized in that: The welding equipment includes positioner, cross manipulator and gas shielded welding machine to realize semi-automatic welding.

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