JPS59153585A - Production of welded article of stabilized stainless steel having low delta-ferrite content - Google Patents

Abstract

PURPOSE:To produce welded articles of stabilized stainless steel of low delta-ferrite content by adjusting the content of delta-ferrite in the welding stage and performing solution treatment at a fixed temp. CONSTITUTION:In the welding of an austenitic stainless steel article, a stainless steel article having a compsn. of type 321 or 347 is welded in such a way that the content of delta-ferrite in the weld part becomes 5-12% using a metal having a compsn. corresponding to the compsn. of type 347. Then, a solution treatment as >=1,000 deg.C for 5-60min is performed to reduce the content of delta-ferrite at the weld part to <=3%. By this way, the production cost is reduced remarkably and welded articles of stabilized stainless steel having low delta-ferrite is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing stabilized stainless steel welded products with a small amount of δ-ferrite, and more specifically, when welding austenite 1-stainless steel products, the present invention relates to a method for producing stabilized stainless steel welded products with a small amount of δ-ferrite. By adjusting the ferrite l-ffi and performing solid solution treatment at a constant temperature, δ is prevented from becoming brittle due to use over time, and the manufacturing cost is significantly reduced compared to when seamless steel is used. - A method for manufacturing stabilized stainless steel welded products with low ferrite content.

Conventionally, we have been manufacturing J5 L:J columns, piping, piping parts, etc. for various chemical equipment that processes high-temperature and highly corrosive fluids such as hydrocrackers and hydrodesulfurization equipment, especially the production of piping and piping parts such as elbows. Stabilized stainless steels such as Type 321 and Type 347 specified in ASTM A 358 (J'IS
G3459 5US321J'3 and 5US347) seamless materials were used. however,
Since seamless materials are expensive, it is desired from an economic point of view to manufacture these members from seam materials instead.

However, the austenitic stainless steel used for these parts is generally prone to high-temperature cracking during welding, so in order to prevent this cracking, a few percent or more of δ-ferrite structure is usually added to the weld metal. Use welding material that contains

On the other hand, if these parts contain a large amount of δ-futalite structure, it may be absorbed into the inner material in hydrogen at high temperatures such as the environment around the reactor of a hydrocracker. Hydrogen embrittlement due to hydrogen or material changes due to long-term use ψ
If the content is large, it may not be able to withstand long-term use under harsh conditions. A problem arises.

The present invention improves the integrity of stainless steel products made of Type 321 J'-3 and Type 347 during welding, that is, prevents hot cracking, and at the same time improves long-term use in harsh environmental conditions. (The purpose is to provide a method for manufacturing stainless steel welded products that can be used in a variety of ways, and as a result, to provide stainless steel welded products that are economically advantageous compared to existing Type 321 and Type 347 seamless materials.) It is now possible to use various chemicals that process corrosive fluids, such as hydrocrackers and hydrodesulfurization equipment.
Suitable for use in W=@ piping, elbows, teeth, soy tins such as redecozer, towers and tanks, etc.

The purpose of this defense is to reduce the δ-ferrite content to a certain level or less by heat treatment after welding, including the suspended δ-ferrite structure necessary during welding, and to improve the chemical composition and heat treatment of the weld metal. This is achieved by combining conditions within a specific range.

However, in the present invention, a stainless steel m product having a composition of type 321 or type 347 is made by using a metal having a composition corresponding to type 347 so that the welded part has a ferrite content of 5 to 12%. welded to 1, then 1
Stabilized stainless steel welding with low δ-]-r light t-m characterized by performing solid solution treatment at 000°C or higher for 5 to 60 minutes to reduce the amount of δ-ferrite in the welded portion to 3% or less. It's in the manufacturing method of the product.

The stainless steel of the present invention having a composition of Type 321 A3 to Type 347 is usually used in various chemical equipment.
It is usually used as a monthly interest rate for 5-digit '75 ffl, room arrangement, piping parts, etc. For example, for piping, △
STM △ 358, and J
In addition, stainless steel welded products include pipes, elbows, teeth, -Fittings such as lilies, towers and tanks, etc. In order to weld these stainless steel products, it is preferable to weld with welding materials (welding rods) of the same composition. Type 347 welding material is used because there is no welding material available.

In the present invention, the content of δ-ferrite in the weld metal during welding must be 5% or more in order to prevent hot cracking during welding. On the other hand, in the environment in which stainless steel products are used, it is desirable that the structure content of δ-ferrite 1 in the material is 3% or more F, which is considered to be able to exhibit stable performance over a long period of time. When a large amount of δ-ferrite structure is generated in the austenitic stainless steel weld metal, it develops into a thick network, and it is difficult to reduce the structure to below a certain level by heat treatment.

That is, when attempting to reduce the content of δ-ferrite by heat treatment after welding, if the amount of δ-ferrite in the welding material exceeds 1 to 12%, for example, 105
Even if a solid solution treatment is performed at 0° C. for 30 minutes and a stabilization treatment is performed at 900° C. for 2 hours, it is practically difficult to keep the amount of ferrite to less than 3%. Therefore, in the present invention, the content of δ-ferrite during welding of the weld metal is 5 to 5.
It is necessary to set it as 12%, preferably in the range of 6-8%. Note that the δ-ferrite content in the weld metal can be set within a desirable range depending on the amount of δ-ferrite contained in the welding material for welding stainless steel products.

Invention I = 331 solid solution treatment time is 5 to 60 minutes,
Preferably it is 20 to 4 minutes. If the solution time exceeds 60 minutes, even if the amount of δ-71 light in the weld metal is 3% or less, adverse effects such as changes in crystal grains in the base metal occur, which is not preferable. The solid solution temperature is 1000°C or higher, preferably t L<111000 to 1100
``G, more preferably (is selected from the temperature range of 1030 to 1070'C).

If the solution temperature is below 1000° C., it is difficult to reduce the amount of δ-ferrite i to a desired range in a short time.

As described above, in the present invention, welding 11, high temperature υ
A sound welded part is produced without any cracking, and the toughness (1, .

Hereinafter, the present invention will be broadly explained based on Examples and Comparative Examples.

Examples 1 to 4 A test piece containing a weld metal whose δ-ferrite suspension was adjusted under various welding conditions was prepared using a welded part 1'EI whose composition was not shown in Table 1, and the test piece was Maximum 90 at 1050℃
The weld metal was held for up to 10 minutes, and the δ-ferrite+-m in the weld metal was measured at each time.

The results are shown in Figure 1. d3, δ-715 during welding
41m is 5.3% in Example 1 and 6.3% in Example 2.
7%, Example 3 9.1% and Example 4 11. '1
%Met. Note that the δ-ferrite suspension was measured by setting a fixed point on the weld metal surface using a ferrite scope.

In addition, Table 2 shows the chemical composition of the weld metal obtained by solid solution treatment at 1050'C for 130 minutes and stabilization at 900°C for 1 hour according to Example 2.
Table 3 shows the tensile property values of the welded parts using JIS No. 14A test pieces.
Table 4 shows the absorbed energy values of the weld metal part and heat affected zone of the welded part at Uon, which were conducted using a No. 4 Charpy impact test piece.

Table 1 No. 2 Fire brother 3
Table 4 From Table 1, Examples 1 to 4 in which the δ-Funi [light suspension was in the range of 51 to 12%]
-) Ding light is reduced to 3% or less.

Example 1 where the amount of δ-ferrite is relatively small especially during welding
In cases 3 to 3, 30 minutes of solid solution treatment reduces the amount of tails to δ-ferrite 1 to 3% or less. J3, weld metal with a δ-ferrite content of more than 12% can also be treated with a long-term solution treatment to reduce the δ-ferrite 1~
If the amount is less than 3% F or the solution time is prolonged, it is not preferable because adverse effects such as changes in the crystal grain size within the matrix occur.

In addition, as shown in Tables 3 and 4, Example 2
The tensile properties of the weld metal at air temperature and 450°C, as well as the absorbed energy value in the PLJ impact test at air temperature, all showed sufficient values.

Comparative Examples 1 to 2 Using welding materials having the compositions shown in Table 1, test pieces containing weld metals in which the δ-ferrite l-1 was adjusted using various weld strips 1 were prepared. up to 120 °C
The sample was held for up to 1 minute, and the amount of δ-ferryl at each time was measured at the lowest temperature. The results are shown in FIG. Note that the amount of δ-ferrite during welding was 6.7% in Comparative Example 2 and 9.1% in Comparative Example 3.

As shown in Figure 2, in Comparative Examples 1 and 2, the amount of δ-ferrite after 120 minutes of heat treatment was not less than 3%, but was 4.1% and 7.1%, respectively. there were.

Comparative Example 3 Using a welding mill with the composition shown in Table 1 and having a composition of 1050°CX 30 minutes)
Although the amount of δ-ferrite decreased by each heat treatment of and stabilization (900° C. x 2 hours), the final amount of δ-ferrite was 7% or more.

[Brief explanation of the drawing]

Figure 1 shows the δ-ferrite 1 of Examples 1 to 3 and Comparative Example 1.
A graph showing the relationship between the amount of ~ and holding time at 1050°C, and Figure 2 show the relationship between the amount of δ-ferrite and the holding time at 1050°C in Comparative Examples 2 and 3.
2 is a graph showing the relationship between retention times. Patent applicant JGC Corporation

Claims (1)

[Claims] 1. Using a stainless steel product having a composition of type 321 or type 347, using a metal having a composition corresponding to type 347, and using δ-ferrite 1 to 5 to 1 of the C welding part.
Welding is carried out so that the δ-
δ-ferrite 1 characterized by a ferrite content of 3% or less - stabilized stainless steel welded product 1 with less ferrite
31! 1 construction method. 2. The above stainless steel 1!1 products, piping, fittings iJ3 J, Hito4? ! 1) The manufacturing method according to claim 1, which is in category i.