JPS597483A - One side welding method of high purity ferritic stainless clad steel - Google Patents

Abstract

PURPOSE:To obtain a welded joint which is excellent in a mechanical property, corrosion resistance and a thermal stress property, by welding a clad material part of clad steel by the same metal, and thereafter executing one side butt welding of the first layer of a base metal part and its following part by dead-low carbon steel and the same metal as the base metal, respectively, from the base metal side. CONSTITUTION:When executing one side butt welding from the base metal face side, as to a clad steel plate whose cladding material is high purity ferritic stainless steel containing 16-21wt% Cr and 0.75-3.5% Mo, the cladding material part is brought to the same metal welding by use of a welding rod having the same composition as the cladding material, subsequently, the first layer of the base metal part or that which includes the second layer is welded by use of a dead-low carbon steel welding rod consisting of <=0.02% C, <=0.50% Si, <=1.00% Mn, and the balance iron and inevitable impurities, and the second layer or the third layer through the final layer are welded by the same metal by use of a welding rod having the same composition as the base material. Also, a part or the whole of welding of said base material part can be executed by a ferritic stainless steel welding rod.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to C
r amount 16-21 wt%, Mo amount 0.75-3.5 vt
% of high purity ferritic stainless clad steel.

Traditionally, austenitic stainless steels such as 5US304.81J8316 have been mainly used as corrosion-resistant materials for equipment in the petroleum and chemical industries, but these are prone to stress corrosion cracking in environments containing chlorides, etc. There was a drawback. In order to eliminate such drawbacks, 5U8
A high-purity ferritic stainless steel has been developed that has almost the same corrosion resistance and workability as 304.5US316, is also the same price, and has low stress corrosion cracking susceptibility. Purity ferritic stainless steel) has been standardized by JIS.

Therefore, high-purity ferritic stainless steel is replacing austenitic stainless steel as a corrosion-resistant material for equipment in the petroleum and chemical industries.
However, its use has been limited to relatively thin-walled storage tanks, heat exchangers, pressure vessels, etc.

Establishment of a welding method for clad steel made of high-purity ferritic stainless steel is expected to be used in the field of thick-walled large storage tanks and pressure vessels, and also for natural gas gearing lines where stress corrosion cracking is a particular problem. Due to its price, it is also expected to be used as piping components in industrial and chemical plants.

An example of a method for welding clad steel using high-purity ferritic stainless steel as a mating material is disclosed in JP-A-56-56797. In other words, one-side butt welding is performed with the cladding material made of high-purity ferritic stainless steel as the first layer side, the first layer or up to the second layer is welded using a welding rod of the same composition as the cladding material, and the second layer or A method of welding from the third layer to the final layer using a welding rod having the same composition as the base metal, an austenitic stainless steel welding rod, or an Inconel welding rod has been disclosed. Can be mentioned.

1. When the base metal is welded with a welding rod having the same composition as the base metal, a hardened region is formed in the boundary layer between the welded joint and the base metal, and this hardened region is It does not easily soften during post-weld heat treatment in the temperature range below 100 mL.

2. If the base metal is welded with an austenitic stainless steel welding rod or an Inconel welding rod, the above-mentioned hardened area will not be formed, but the welding material is expensive, and the non-welded and welded areas may be separated. Due to the difference in the coefficient of thermal expansion, distortion and thermal stress may occur when used in high temperature ranges.

The present invention has been made in view of the above circumstances.
, 16 to 21 vt% Cr and 0.75 to B, represented by 19Cr-2Mo high-purity ferritic stainless steel,
A welded joint with excellent mechanical properties, corrosion resistance, and thermal stress resistance of clad steel made of high-purity ferritic stainless steel containing 5 wt% Mo (hereinafter simply referred to as high-purity ferritic stainless steel). The purpose is to provide a welding method that obtains.

A single-sided welding method for high-purity ferritic stainless steel according to the present invention will be described with reference to the drawings.

As shown in FIGS. 1(a) and 1(b), a υ groove (&) or a V groove (b) with an opening on the base material 2 side is provided, and the laminate material 1.
1, but at this time, in order to prevent an increase in the amount of carbon ((i)) in the weld metal due to penetration of the carburized layer at the boundary, the mating materials 1 and 1 are For example, a trench depth h of approximately O, S■ is performed.As the groove, either the U groove (a) or the %Vtl'! tip (b) may be used.

Using a U-shaped opening (1) as shown in Fig. 1 (a), welding rods of the same composition as the laminate material 1 are applied to the protruding part of the laminate material 1.1 as shown in Fig. 2 (a). Welding is performed to obtain a welded metal 3 for the first layer on the side of the laminate. At this time, in order to avoid deterioration of the corrosion resistance and mechanical properties of the weld metal 3, it is necessary to prevent penetration of the base metal 2 and ensure sufficient wall thickness. If the thickness is not sufficient, additional welding material is applied overlay. After welding of the laminate material 1 is completed, welding is performed on the base material 2 side. In this case, the first layer on the base material side is made of silicon (Sl) with a carbon content of 0.02 wt% or less.
Amount 0.5 vrt% or less, Manganese (M,,) amount 1.
An intermediate weld metal 4 is formed by welding using an ultra-low carbon steel welding rod containing no more than Owt% and other unavoidable impurities. Next, the remaining portion is overlay-welded with the base metal weld metal 5 of the second and subsequent layers on the base metal side using a welding rod having the same composition as the base metal. Welding the first layer on the base metal side, which is the intermediate weld metal 4, using an ultra-low carbon steel welding rod as described above is because welding with a carbon steel rod will result in a welding of the cladding weld metal 3 or Cr +
Martensite is produced by diluting Mo and C in the base metal, but under normal welding conditions, the amount of C in the welding rod is reduced to 0.
This is because it has been found that martensite with excellent ductility can be obtained by suppressing the content to 0.02 vt% or less. S19
Mn is necessary as a deoxidizing agent, but excessive addition inhibits ductility and toughness, so it should be added at 0.5 vrt% or less, 1,
Owt% or less.

Next, another welding method for intermediate weld metal will be explained.

Using the U groove (a) shown in Fig. 1 (a), first use a welding rod with the same composition as that of the laminate 1 on the protruding part of the laminate 1°1 as shown in Fig. 2 (a). After welding the welding metal 3 of the first layer on the side of the welding material 1 or the welding metal welding metal 1 of the second layer on the side of the welding material, weld the intermediate weld metal 4', the base metal side tube, on which is the same as the base metal. The base metal weld metal 5 of the second and subsequent layers on the base metal side is overlay-welded using a welding rod of the same composition. This reduces the infiltration of Cr and Mo into the subsequent base material weld metal 5 by forming an intermediate weld metal 4' with a low Cr content and Mo content. This is to obtain a welded joint with good mechanical properties. Cr
The reason for setting the amount to 11 to 16 wt% is that if it is less than 11 wt%, the intermediate weld metal 4' will become martensite and its mechanical properties will be poor, and if it is more than 16 wt%, C will be absorbed into the base weld metal 5.
This is because the effect of reducing the penetration of r is weakened.

Next, a method for obtaining a joint weld with good mechanical properties without forming an intermediate weld metal will be described.

Using a V-shaped opening (b) as shown in Fig. 1 (b), weld a welding rod with the same composition as the laminate material 1 on the protruding part of the tip mating material 1.1 as shown in Fig. 2 (b). After overlaying the first layer weld metal 3 on the laminate 1 side or the weld metal 3' on the second layer using Cr, the gold layer on the base metal 2 side is
Overlay welding was carried out using a ferritic stainless steel welding rod containing 11 to 20 vt% of the welding material, thereby obtaining a joint welded portion without a hardened layer as the base metal weld metal. Cr amount 11-20
The reason for setting it as vt% is that if it is less than 1 lvt%, a hard martensitic layer will be formed, and if it is more than 20 wt%, a hardened layer will not be formed but the ductility will decrease.

By welding high-purity ferritic stainless clad steel according to the above-described single-sided welding method according to the present invention, there is no intrusion of C into the weld metal of the cladding material, and there is no deterioration in bendability or hydrogen cracking. Welding of high-purity ferritic stainless steel with excellent corrosion resistance and mechanical properties, with no hardened layer and no stress or distortion caused by significant differences in thermal expansion coefficients when used in high-temperature ranges. Below, 5US444 with a plate thickness of 3 mm (C amount o, oo
An example of single-sided welding of a clad steel plate made of 8B42 with a thickness of 11 sheets as the base material using 8B42 as the base material is shown below.

Example 1 The U groove (1) in Figure 1 (a) was used, and the cladding part was welded together with a welding rod having the same composition as the cladding material (8U8444) under the welding conditions shown in Table 1. Then, the first layer on the base metal side, which is the intermediate weld metal 4, has a C content of 0. O2 wt% or less, S1 amount 0.5
Welding is carried out using a welding rod of ultra-low carbon steel composition consisting of 0 wt% or less, Mn content of 1.004J or less, and the balance is iron and unavoidable impurities, and welding from the second layer to the final layer has the same composition as the base metal. Overlay welding was performed using a rod.

Table 1 Welding conditions Figure 3 shows a photograph of the cross-sectional structure of the obtained joint weld, Figure 4 shows the Vickers hardness distribution, and Table 2 shows the mechanical properties. In FIG. 4, range A indicates the base weld metal 5, range B indicates the intermediate weld metal 4, and range C indicates the range of the weld metal 3.

Table 2 Mechanical properties of joint welds All exhibit good performance. The amount of C in the weld metal 3 is 0. At O05wt%, no immersion of C was observed at all.

Example 2 With the V groove (b) in Figure 1 (b), the laminate part was welded with a welding rod having the same composition as the laminate material (8tTS 444) under the welding conditions shown in Table 3, and then and then weld the second
The layers from layer to final layer were overlay welded using a welding rod having the same composition as the base metal.

Table 3 Welding conditions Table 4 shows the mechanical properties of the joint welds obtained. Figure 5 shows the distribution of Vickers hardness.

In FIG. 5, range A indicates the base weld metal 5, range B' indicates the intermediate weld metal 4', and range C indicates the range of the weld metals s and f for the cladding materials.

Table 4 Mechanical properties of joint welds All of the results were good, and the corrosion test of the welded joints showed corrosion resistance equivalent to that of the raw material of clad steel.

Example 3 The U groove (a) in Figure 1 (a) was used, and the cladding part was welded with a welding rod having the same composition as the cladding material (SUS 444'') under the welding conditions shown in Table G5. Then, Table 6 shows the mechanical properties of the nine joint welds obtained under the welding conditions in Table 5.The Vickers hardness distribution is shown in FIG.

In Fig. 6, the A' range is the base metal weld metal, and the C range is the expansion material weld metal 3. Indicates the range of

Table 6 Mechanical properties of joint welds Good results were obtained in all cases.

[Brief explanation of the drawing]

Figures 1 (a) and (b) are diagrams showing the groove used in the single-sided welding method for high-purity ferritic stainless clad steel according to the present invention, and Figures 2 (a) and (b) are respectively An explanatory diagram of the welding method according to the present invention, FIG. 3 is a photograph of the cross-sectional structure of the joint welded part obtained in Example 1, and FIG.
Figure 5 shows the hardness distribution diagram of the joint weld obtained in Example 2.
The hardness distribution map of the joint weld obtained in Figure 6 is Example 3.
It is a hardness distribution map of the joint weld obtained in the above. 1: Laminating material, 2: Base metal, 3, 3': Laminating material weld metal (common metal), 4: Intermediate weld metal (ultra-low carbon steel), 4': Intermediate weld metal (Cr content of 11 to 16 vt%) 5: Base metal weld metal (common metal); DA: Base metal weld metal (ferritic stainless steel with a Cr content of 11 to 20 vt%). Agent Patent Attorney Mae 1) Interest 2 1st f! 1 Figure 2 3rl! i Figure 4 Figure 5

Claims (1)

[Claims] 1, 16-21vt% Cr and 0.75-B, 5w
In a welding method for clad steel plates using high-purity ferritic stainless steel containing t% of Mo as the laminate, one-sided butt welding is performed from the base metal side, and the cladding part is welded using a welding rod with the same composition as the laminate. Then, the base metal part up to the first layer or the second layer is welded using CJllo, 0.02 wt% or less, 81 amount of 0.50 wt% or less, Mn amount of 1. OOwt
% or less, the balance is iron and unavoidable impurities. A single-sided welding method for 19Cr-2Mo-based high-purity ferritic stainless clad steel, characterized by gold welding. 2. 16-21wt% Cr and 0.75-3.5w
In a welding method for clad steel sheets using high-purity ferritic stainless steel containing t% of Mo as the laminate, one-sided butt welding is performed from the base metal side, and the cladding part is welded using a welding rod with the same composition as the laminate. Crfkl 1 to l 6 w
Welding is performed using a ferritic stainless steel copper welding rod containing t%, and welding is carried out using a welding rod having the same composition as the base metal from the second layer to the third layer to the final layer. A single-sided welding method for 19Cr-2Mo high-purity ferritic stainless clad steel. 3. 16-21wt% Cr and 0.75-3.5w
In a welding method for clad steel sheets using high-purity ferritic stainless steel containing t% of Mo as the laminate, one-sided butt welding is performed from the base metal side, and the cladding part is welded using a welding rod with the same composition as the laminate. Then welded the base material from the first layer to the final layer with a Cr i of 11 to 20 wt%.
A single-sided welding method for 19Cr-2Mo-based high-purity ferritic stainless steel and clad steel, the method comprising welding using a ferritic stainless steel welding rod containing 19Cr-2Mo.