Corrosion-resistant large high-pressure flange of same kind of stainless steel and overlaying method thereof

Abstract

This invention discloses a corrosion-resistant large high-pressure flange with a uniform stainless steel weld overlay, comprising a flange body. Both the lower and inner surfaces of the flange body are provided with weld overlay structures. Specifically: a first weld overlay transition layer is provided on the lower surface of the flange body, and a first weld overlay layer of the same material as the flange is provided above the first weld overlay transition layer; a second weld overlay transition layer is provided on the inner surface of the flange body, and a second weld overlay layer of the same material as the flange is provided above the second weld overlay transition layer; the first weld overlay transition layer and the second weld overlay transition layer are connected, and the first weld overlay layer and the second weld overlay layer are also connected. This invention, by providing a uniform material weld overlay layer on the flange sealing surface, eliminates the need for a weld transition layer, which helps to ensure the overall mechanical properties and corrosion resistance of the flange, effectively prevents stress corrosion, and makes quality more controllable.

Description

Technical Field

[0001] This invention patent belongs to the field of flanges, specifically relating to a method for welding the same type of stainless steel onto a corrosion-resistant large high-pressure flange. Background Technology

[0002] A flange, also called a flange plate or flange, is a part used to connect shafts to each other, and is used for connecting pipe ends. There are also flanges used on equipment inlets and outlets for connecting two pieces of equipment, such as speed reducer flanges. A flange connection or flange joint refers to a detachable connection consisting of a flange, gasket, and bolts connected together as a combined sealing structure. Pipe flanges refer to flanges used for piping in pipeline installations, while those used on equipment refer to the inlet and outlet flanges of the equipment. Flanges have holes, bolts are used to tightly connect two flanges, and a gasket is used to seal between the flanges. Flanges are divided into threaded flanges, welded flanges, and clamp flanges.

[0003] The preservation of the crystalline structure of large high-pressure flanges relies on heat treatment, which often results in poor quality and excessively coarse internal crystalline structures. After machining the sealing groove, these coarse structures are exposed to corrosive media, and the flange sealing surface experiences significant stress. When stress concentration leads to small cracks, the corrosive media erodes the matrix, causing crack propagation and ultimately failure.

[0004] The sealing groove of the inlet flange of the existing residual oil hydrotreating reactor is subjected to the pressure of the gasket, and its contact with hydrogen creates conditions for hydrogen embrittlement. Hydrogen residue in the steel will cause embrittlement. After hydrogen atoms penetrate the steel, the grain bonding force of the steel decreases, resulting in a decrease in the elongation and reduction of area of ​​the steel or delayed failure, which leads to cracking of the inlet flange and reactor leakage.

[0005] CN208535373U discloses a stainless steel weld overlay on the upper surface of a connecting flange. This stainless steel weld overlay includes a transition layer and a corrosion-resistant layer, with the transition layer located between the connecting flange and the corrosion-resistant layer. Its base material is a carbon steel layer, and dissimilar materials are used for weld overlay. The alloy element content of the transition layer welding material is required to be higher than that of the corrosion-resistant layer welding material. Moreover, the inner surface of the connecting flange has a stainless steel pipe. The flange structure is complex, and although stainless steel is used for corrosion protection, the stress corrosion problem mentioned above cannot be avoided.

[0006] Therefore, it is necessary to find a way to ensure the overall mechanical and corrosion resistance of large high-pressure flanges.

[0007] Invention Patent Content

[0008] This invention provides a corrosion-resistant large high-pressure flange with the same type of stainless steel overlay welding, which solves the above-mentioned technical problems.

[0009] The solution proposed in this invention to the above-mentioned technical problems is as follows:

[0010] In a first aspect, the present invention provides a corrosion-resistant large high-pressure flange with the same type of stainless steel overlay, comprising a flange body, wherein the lower surface and the inner surface of the flange body are provided with overlay structures, wherein: a first overlay transition layer is provided on the lower surface of the flange body, and a first overlay layer of the same material as the flange is provided above the first overlay transition layer; a second overlay transition layer is provided on the inner surface of the flange body, and a second overlay layer of the same material as the flange is provided above the second overlay transition layer; the first overlay transition layer is connected to the second overlay transition layer, and the first overlay layer is connected to the second overlay layer.

[0011] Optionally, the first and second weld overlay transition layers are welded before heat treatment, and the first and second weld overlay layers are welded after heat treatment.

[0012] Optionally, the thickness of the first weld overlay transition layer, the second weld overlay transition layer, the first weld overlay layer, and the second weld overlay layer is not less than 3 mm.

[0013] Optionally, the sealing surface of the flange has a hardness greater than 170HB.

[0014] Optionally, both the first and second weld overlay transition layers are welded using E309L stainless steel welding rods, and both the first and second weld overlay layers are welded using E347 stainless steel welding rods.

[0015] Optionally, the lower surface of the flange body is provided with at least one annular groove to accommodate the first weld overlay transition layer and the first weld overlay layer, so as to increase its structural strength and sealing performance.

[0016] Optionally, the flange body is manufactured using a forging process to ensure its overall structural strength and corrosion resistance.

[0017] Optionally, the flange body undergoes rigorous surface cleaning and degreasing treatment before welding to ensure the quality and bonding strength of the welded structure.

[0018] Secondly, the present invention provides a method for preparing the aforementioned corrosion-resistant large high-pressure flange, comprising the following steps:

[0019] S1, the first and second weld overlay transition layers are respectively welded on the lower and inner surfaces of the flange body;

[0020] S2, After the transition layer is completed by welding, the flange is heat treated;

[0021] S3, after heat treatment, perform welding of the first and second weld overlay layers.

[0022] The welding process can be selected as either submerged arc welding or electroslag welding, depending on the requirements.

[0023] The beneficial effects of this invention are as follows: Using the same material as the weld overlay results in a dense weld layer structure, preventing stress pits and stress corrosion cracking, thus facilitating stress corrosion protection. Furthermore, the specific weld overlay structure of this invention helps ensure the overall mechanical properties of the flange, reinforcing the flange body. Simultaneously, by setting the weld overlay sequence and thickness before and after heat treatment, the performance and service life of the flange are further improved. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a corrosion-resistant large high-pressure flange structure with the same type of stainless steel overlay welding as in Example 1.

[0025] Figure 2 for Figure 1 An enlarged schematic diagram of the indicator area in section A. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1:

[0028] Please see Figure 1 2. A corrosion-resistant large high-pressure flange with weld overlay of the same stainless steel, comprising a flange body 11, wherein the lower surface and inner surface of the flange body 11 are provided with weld overlay structures, wherein: a first weld overlay transition layer 12 is provided on the lower surface of the flange body 11, and a first weld overlay layer 13 of the same material as the flange is provided above the first weld overlay transition layer 12; a second weld overlay transition layer 14 is provided on the inner surface of the flange body 11, and a second weld overlay layer 15 of the same material as the flange is provided above the second weld overlay transition layer 14; the first weld overlay transition layer 12 is connected to the second weld overlay transition layer 14, and the first weld overlay layer 13 is connected to the second weld overlay layer 15.

[0029] The first and second weld overlay transition layers are welded together before heat treatment, and the first and second weld overlay layers are welded together after heat treatment. The following is a specific weld overlay method, including the following steps:

[0030] S1, a first and a second weld overlay transition layer are respectively welded onto the lower and inner surfaces of the flange body. The main purpose of these two transition layers is to improve the bonding strength between the weld overlay layer and the substrate and to reduce welding stress.

[0031] S2. After the transition layer is completed with weld overlay, the flange undergoes heat treatment. The purpose of heat treatment is to eliminate welding stress, improve the material's microstructure and properties, and enhance the flange's corrosion resistance and mechanical strength. The appropriate heat treatment temperature and time are selected based on the flange's material and thickness. Generally, the heat treatment temperature should be higher than the material's phase transformation temperature but not exceed its melting temperature.

[0032] S3, after heat treatment, perform welding of the first and second weld overlay layers.

[0033] The welding process can be selected from either submerged arc welding (SAW) or electroslag welding (ESW) depending on actual needs. SAW is currently more widely used, while ESW offers better performance and is more advanced. To further improve the flange's performance and service life, the thicknesses of the first weld overlay transition layer, the second weld overlay transition layer, the first weld overlay layer, and the second weld overlay layer are all not less than 3 mm. In one specific embodiment, the total weld overlay thickness is 6 mm, with an effective surface layer thickness greater than 3 mm.

[0034] Specifically, the flange material can be E347. The welding materials for both the first weld overlay transition layer 12 and the second weld overlay transition layer 14 are E309L stainless steel welding rods, and the welding materials for both the first and second weld overlay layers are E347 stainless steel welding rods. The sealing surface hardness of the flange is greater than 170HB. The first and second weld overlay transition layers are welded using E309L stainless steel welding rods to ensure a good transition with the flange body material; the first and second weld overlay layers are welded using E347 stainless steel welding rods to ensure the homogeneity of the weld overlay layers with the flange body material, thereby improving the overall corrosion resistance and structural strength of the flange.

[0035] Specifically, the lower surface of the flange body 11 is provided with at least one annular groove, for example, an annular groove is provided in the A-section indicating area, to accommodate the first weld overlay transition layer 12 and the first weld overlay layer 13, so as to increase its structural strength and sealing performance.

[0036] Optionally, the flange body 11 is made by forging to ensure its overall structural strength and corrosion resistance.

[0037] Optionally, the flange body 11 undergoes rigorous surface cleaning and degreasing treatment before welding to ensure the quality and bonding strength of the welded structure.

Claims

1. A corrosion-resistant large high-pressure flange with the same type of stainless steel overlay welding, characterized in that, The flange includes a flange body, the lower surface and the inner surface of which are provided with a weld overlay structure, wherein: a first weld overlay transition layer is provided on the lower surface of the flange body, and a first weld overlay layer of the same material as the flange is provided above the first weld overlay transition layer; a second weld overlay transition layer is provided on the inner surface of the flange body, and a second weld overlay layer of the same material as the flange is provided above the second weld overlay transition layer; the first weld overlay transition layer and the second weld overlay transition layer are connected, and the first weld overlay layer and the second weld overlay layer are connected.

2. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The first and second weld overlay transition layers are welded together before heat treatment, and the first and second weld overlay layers are welded together after heat treatment.

3. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The thickness of the first weld overlay transition layer, the second weld overlay transition layer, the first weld overlay layer, and the second weld overlay layer is not less than 3 mm.

4. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The sealing surface of the flange has a hardness greater than 170HB.

5. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The first and second weld overlay transition layers are both welded using E309L stainless steel welding rods, and the first and second weld overlay layers are both welded using E347 stainless steel welding rods.

6. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The lower surface of the flange body is provided with at least one annular groove to accommodate the first weld overlay transition layer and the first weld overlay layer, so as to increase its structural strength and sealing performance.

7. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The flange body is made by forging to ensure its overall structural strength and corrosion resistance.

8. The corrosion-resistant large high-pressure flange according to claim 1, characterized in that, The flange body undergoes rigorous surface cleaning and degreasing treatment before welding to ensure the quality and bonding strength of the welded structure.

9. The method for preparing the corrosion-resistant large high-pressure flange according to any one of claims 1 to 8, characterized in that, Includes the following steps: S1, the first and second weld overlay transition layers are respectively welded on the lower and inner surfaces of the flange body; S2, After the transition layer is completed by welding, the flange is heat treated; S3, after heat treatment, perform welding of the first and second weld overlay layers.

10. The preparation method according to claim 9, characterized in that, The aforementioned welding process is either submerged arc welding or electroslag welding.

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