CN104400239A - Method for welding two parts with significant difference of material characteristics - Google Patents

Abstract

The present invention relates to a method for welding two parts having significantly different material properties, comprising the following steps in sequence: Step 10: overlay welding on the first part; The surfacing on the first part is heat treated for 140 to 220 minutes; step 30: the surfacing of the first part and the second part are cut into bevels to make bevels on their outer circumferences; step 40: at 250 ° C to Preheating the first part and the second part at a temperature between 350°C; step 50: assembling the first part and the second part; step 60: welding the first part to the second part through the weld joint in the bevel; step 70 : Heat treatment of the welded joint at a temperature between 680°C and 700°C for 10 to 14 hours. The method of the invention enables direct and reliable welding of one part to another part having significantly different material properties.

Description

Method for welding two parts with significantly different material properties

technical field

The present invention mainly relates to a method for welding two parts having significantly different material properties, in particular a method for welding two parts having significantly different material properties in a steam turbine.

Background technique

Steam turbines can be used to power generators, compressors, pumps and other equipment, and can be used in power plants, chemical plants, sugar factories, textile mills, steel mills, paper mills or mines, etc. Related systems generally include: a steam generator that turns water into steam by heating (for example, by coal, natural gas, or fuel oil); and a steam turbine that converts energy contained in steam into kinetic energy to drive various devices. There are stationary blades on the cylinder block and moving blades on the rotor in the steam turbine. When the steam turbine is running, the expanded high-pressure steam passes through several stages arranged alternately by the stationary blades and the moving blades to turn the rotor. The pressure in the steam turbine decreases continuously as the steam passes through successive turbine stages. Different applications also require turbines with various steam flow configurations, such as condensing or non-condensing exhaust, direct or controlled extraction, or controlled inlet.

Many parts of the steam turbine described above require welding to each other. When the parts are directly welded and the material properties differ significantly from each other, defects such as cracks often develop shortly after the welding is completed.

Contents of the invention

The object of the present invention is to provide a method for welding two parts having significantly different material properties, comprising the following steps in sequence:

Step 10: Surfacing welding on the first component;

Step 20: heat-treating the weld overlay on the first part at a temperature between 740°C and 745°C for 140 to 220 minutes;

Step 30: Beveling said weld overlay of said first part and said second part to create bevels on their outer circumferences;

Step 40: Preheating said first part and said second part at a temperature between 250°C and 350°C;

Step 50: assembling the first component and the second component;

Step 60: Welding the first part to the second part through the weld joint in the ramp;

Step 70: Heat treating the welded joint at a temperature between 680°C and 700°C for 10 to 14 hours.

The inventive method for welding two parts having significantly different material properties enables direct and reliable welding of one part to another part having significantly different material properties.

According to one aspect of the present invention, after step 20 and before step 30, further include: step 23: naturally cooling the first component and the second component to ambient temperature.

According to another aspect of the present invention, after step 60 and before step 70, there is also: step 67: inspecting the welded joint by non-destructive testing.

According to still another aspect of the present invention, after step 70, there is also: step 75: inspecting the welded joint through non-destructive testing.

According to a further aspect of the invention, said first part is made of a material of type ENISO 6.4 according to the European material standard, and said second part is made of a material of the type ENISO 5.1 according to the European material standard production.

According to yet another aspect of the invention, the first part is made of GX12CrMoVNbN91 and the second part is made of GX17CrMoV5-10.

According to still another aspect of the present invention, the thickness of the surfacing welding is 20mm.

According to yet another aspect of the present invention, the material of the surfacing welding is a type of material numbered ENI ISO 6.4 according to the European material standard.

According to yet another aspect of the invention, the temperature rate is at most 60° C./hour for every two steps and for all steps.

According to other aspects of the invention, the rate of temperature change between each two steps and within each step is 50° C./hour.

Description of drawings

The following drawings are only intended to illustrate and explain the present invention schematically, and do not limit the scope of the present invention. in,

Fig. 1 is a flowchart according to a first embodiment of the present invention;

Fig. 2 is a flowchart according to a second embodiment of the present invention;

Fig. 3 is a flowchart according to a third embodiment of the present invention;

Fig. 4 is a flowchart according to a fourth embodiment of the present invention.

Detailed ways

In order to have a clearer understanding of the technical features, purposes and effects of the invention, the specific implementation manners of the present invention will now be described with reference to the accompanying drawings, in which the same reference numerals represent the same parts.

In this article, "schematic" means "serving as an example, example or illustration", and any illustration or implementation described as "schematic" should not be interpreted as a more preferred or more advantageous Technical solutions.

In order to make the drawing concise, each drawing only schematically shows the parts related to the present invention, and they do not represent the actual structure of the product. In addition, to make the drawings concise and easy to understand, in some drawings, only one of the components having the same structure or function is schematically shown, or only one of them is marked.

Herein, "a" not only means "only one", but also means "more than one".

As shown in Figure 1, a method for welding two parts with significantly different material properties consists of the following steps in sequence:

Step 10 (S10): performing surfacing welding on the first component;

Step 20 (S20): heat treating the surfacing on the first part at a temperature between 740°C and 745°C for 140 to 220 minutes;

Step 30 (S30): beveling said surfacing of said first part and said second part to create bevels on their outer circumferences;

Step 40 (S40): preheating the first part and the second part at a temperature between 250°C and 350°C;

Step 50 (S50): assembling the first component and the second component;

Step 60 (S60): welding said first part to said second part through a weld joint in said slope;

Step 70 (S70): performing heat treatment on the welded joint at a temperature between 680°C and 700°C for 10 to 14 hours.

For those skilled in the art, the above-mentioned first part can be a flange or a pipe, etc., and is made of a material according to the European material standard number EN ISO6.4, especially GX12CrMoVNbN91. The second part can be a flange, a housing or a pipe etc. and is made of a material according to the European material standard number EN ISO5.1, in particular GX17CrMoV5-10. The thickness of the surfacing welding is 20mm, and the material of the surfacing welding is a kind of material according to the European material standard number EN ISO6.4. The method of the invention enables direct and reliable welding of one part to another part having significantly different material properties. By using overlay welding, an expensive intermediate part between the two parts as in the prior art and two welded joints at both ends of the intermediate part are saved. In addition, the rate of temperature change between each two steps and within each step is at most 60°C/hour, preferably 50°C/hour.

As shown in FIG. 2 , after step 20 ( S20 ) and before step 30 ( S30 ), there is also: step 23 ( S23 ): naturally cooling the first component and the second component to ambient temperature.

As shown in FIG. 3 , after step 60 ( S60 ) and before step 70 ( S70 ), there is also: step 67 ( S67 ): inspecting the welded joint through non-destructive testing.

As shown in FIG. 4 , after step 70 ( S70 ), there is also: step 75 ( S75 ): inspecting the welded joint through non-destructive testing.

What has been described above should be considered as exemplary embodiments of the present invention. Other modifications of this invention should be apparent to those skilled in the art from the teachings herein, and, therefore, all such modifications are intended to be protected under this invention so long as they come within the true spirit and scope of this invention. within the scope of protection of the invention.

Claims (10)

1. A method for welding two parts having a significant difference in material properties, comprising the steps of, in order:

step 10 (S10): overlaying the first component;

step 20 (S20): heat treating the weld deposit on the first component at a temperature between 740 ℃ and 745 ℃ for 140 to 220 minutes;

step 30 (S30): beveling the weld overlay and the second component of the first component to produce a bevel on their outer circumference;

step 40 (S40): preheating the first part and the second part at a temperature between 250 ℃ and 350 ℃;

step 50 (S50): assembling the first component and the second component;

step 60 (S60): welding the first component to the second component through a weld joint in the bevel;

step 70 (S70): the soldered joint is heat-treated at a temperature of between 680 ℃ and 700 ℃ for 10 to 14 hours.

2. The welding method according to claim 1, wherein after step 20(S20) and before step 30(S30) there is further provided:

step 23 (S23): naturally cooling the first and second components to ambient temperature.

3. The welding method according to claim 2, wherein after step 60(S60) and before step 70(S70) there is further provided:

step 67 (S67): the weld joint is inspected by a non-destructive test.

4. The welding method according to claim 2, wherein there is further provided, after step 70 (S70):

step 75 (S75): the weld joint is inspected by a non-destructive test.

5. The welding method according to any one of claims 1 to 4, wherein the first part is made of a type of material according to European Material Standard No. EN ISO6.4 and the second part is made of a type of material according to European Material Standard No. EN ISO 5.1.

6. The welding method of claim 5, wherein the first component is made of GX12CrMoVNbN91 and the second component is made of GX17CrMoV 5-10.

7. The welding method according to any one of claims 1 to 4, wherein the thickness of the weld deposit is 20 mm.

8. A welding method according to any one of claims 1 to 4 wherein the material of the weld deposit is of the type having a European Material Standard number EN ISO 6.4.

9. The welding method of any one of claims 1 to 4 wherein the rate of temperature change between each two steps and within each step is at most 60 ℃/hour.

10. The welding method of claim 9, wherein the rate of temperature change between each two steps and within each step is 50 ℃/hour.