JPS5865596A - Welding electrode for padding of ferritic stainless steel - Google Patents

Abstract

PURPOSE:To obtain a welding electrode for padding which yields deposited metal consisting of perfect ferritic structure of fine crystal grains by containing specific contents of C, Si, Mn, Cr, Nb, V, Ti, Al in said electrode. CONSTITUTION:An electrode for padding of ferritic stainless steel is contained, by weight %, with <0.12 C, <1 Si, <2 Mn, 11-20 Cr, 0.4-1.1 Nb, 0.2-0.9 V, 0.2-2 Ti, 0.2-1 Al. If the welding electrode for padding added with Al, V other than Nb, Ti in this way is used, the deposited metal consisting perfect ferritic structure of fine crystal grains is easily obtained in excellent welding workability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a welding electrode for overlaying ferritic stainless steel, and relates to a welding electrode for overlaying ferritic stainless steel. This paper attempts to propose a welding electrode for overlay that is suitable for use in manufacturing.

In general, stainless steel has excellent corrosion resistance over a wide range of areas, so it is also used as a cladding material for clad steel.
-360/.

Among these, austenitic stainless steel laminated materials exhibit extremely stable corrosion resistance due to the interaction of chromium (Or) and nickel (N1), and are suitable for a wide range of applications, but are fatal in areas where they are susceptible to stress corrosion cracking. Despite considerable efforts to address these drawbacks, no practical solution has yet been reached.

On the other hand, although ferritic stainless steel laminated materials are slightly inferior to austenitic stainless steel in terms of overall corrosion resistance, their crystal structure makes them less susceptible to stress corrosion cracking, so comparisons of overall corrosion resistance are used in oil refining, petrochemical plants, etc. Suitable for those with a looser focus.

However, conventional ferritic stainless clad steels are mainly produced by rolling or explosion bonding using SUS 1101 (/XJr-0, Coml) and SUB 400 (17cj"r) laminates. However, if we use overlay welding instead, the manufacturing process could be much simpler, but attempts to put it into practical use have not been successful because of the following problems: (1) The same components as the steel plate Part or all of the composition of the deposited metal of the system is a martensitic structure.

(2) Submerged arc welding, electroslag welding, other plasma welding, or automated welding such as MIG welding generally involves a large heat input, which tends to coarsen the weld metal crystal grains.

For example, as a coated arc welding rod for ferritic stainless steel, In/(7Nb or D$J) is added with niobium (Nk) to obtain a heptite structure.
OWb etc. are commercially available, but when electroslag welding or submerged arc welding is carried out with the same composition system as these, due to the large heat input, the problem of coarsening of crystal grains mentioned in (2) above occurs. In addition, the slag peeling deteriorates so much that it cannot be put to practical use.Thus, despite the strong demand for ferritic stainless steel clad steel produced by overlay welding with high reliability and efficiency, the above-mentioned problems still exist. In view of the above circumstances, the inventors had no choice but to rely on inefficient rolling or explosive bonding methods, and as a result of various studies, the inventors discovered an electrode composition that could solve the problems of the prior art all at once.

That is, the object of the present invention is to provide a welding electrode for ferritic stainless steel that allows a weld metal consisting of a completely ferritic structure with fine grains to be obtained with excellent welding workability. be.

The above-mentioned welding electrode for overlay of this invention has a carbon content of o, l co m%.
Including F1 silicon up to 80% by weight, manganese up to 2.0% by weight, chromium 11-g in the weight range, O, da~/,/excluding niobium and 0.2-0.9% by weight vanadium. % Oa-~2.0 weight of titanium Oa
The gist of the solution to the above object is to have a composition containing aluminum in an amount of 0.02 to 0.0% by weight.

Now, the weld metal produced by conventional ferrite-based stainless steel coated arc welding rod has a martensitic structure.
By adding appropriate amounts of niobium (Nk) and titanium (T1), which are strong carbide-forming elements and grain refining elements, to (SUS 4410) or 770r (SUS 4IJO) wires with a ferrite structure, the structure can be improved. It was completely ferrite.

However, with this method, when the welding heat input is particularly large, such as in submerged arc welding or electroslag welding, the structure becomes 7-elite, but the grains cannot be refined, and the welding process also contains Nb. As a result, the slag removability is extremely degraded, making it unsuitable for practical use.

On the other hand, the inventors believe that W
b. It has been found that the above problem can be advantageously solved by using an electrode to which aluminum (Al) and vanadium (V) are added in addition to Ti.

In other words, it is characterized by the addition of mulch in addition to Nb and Ti in order to refine the crystal grains of the weld metal, and by substituting a part of the Nb with V to improve the slag removability.

Next, we will discuss the influence of each constituent element on the material and workability of the weld metal and the reasons for each limitation.

Carbon (0) is a necessary component to increase the strength of the molten metal. However, if it is contained in a large amount, it will significantly promote the formation of martensitic structure and reduce toughness and corrosion resistance. Therefore C
The amount is 0. 2% by weight or less (simply an arc).

Silicon <si) is an important component as a deoxidizing element for weld metal, but excessive inclusion coarsens the ferrite structure and -
Since this would impair the properties and ductility, the upper limit was set to /, 0%.

Manganese (Mnl) improves strength and removes sulfur (
It is a component that combines with S) to reduce the harmful effects of S, but if it is added in large amounts, the weld metal will harden and become brittle. Therefore, it was set at 2.0% or less.

Note that lower limits are not particularly specified for the above O, Si, and Mn, but in order to prevent strength reduction,
It is desirable to contain it to the extent that it is contained in 30R stainless steel. That is, 0≧0.02%, S1≧O, OS%,
Mn≧0.3% However, if strength is not a particular issue, this 1g! Therefore, no lower limit is specified.

In order to ensure corrosion resistance, the rumen (Or) is l/%~〃-
And so. If it is less than 11%, the corrosion resistance as stainless steel cannot be maintained, and if it exceeds 7%, sigma phase (σ phase) tends to form.1. It impairs not only corrosion resistance but also ductility.

Now, Nb and V are components added to make the structure 7-elite without deteriorating welding workability, and V in particular is one of the essential components in this invention. Conventionally, only Nb was added, but as mentioned above, when welding with a large heat input such as overlay welding, there is a point where the slag removability deteriorates significantly, and as a result of various studies on this point. It has been found that by substituting a part of Nb with V, the slag peelability can be significantly improved without impairing the ferritization effect at all. If the total amount of Nb and V is less than 0.4%, it is difficult to completely form a slag, and/or if it exceeds 3%, the peelability of the slag deteriorates no matter how much V is adjusted. If Nb is less than 0.0%, it is difficult to completely convert the structure to ferrite even if V is added in an amount greater than 0.0%, and if it exceeds 7%, slag exfoliation cannot be improved even by the effect of V. Also, for V it is 0
．． If it is less than 2%, no effect of improving slag peeling property is observed, and if it is reduced by 5%, the mechanical quality, especially the creep property, deteriorates.

Ti is added to refine the crystal grains, but if it is less than 0.2%, there is no refinement effect even if you add mulch, which will be described below.On the other hand, if it exceeds 2.0%, the effect of V mentioned above will not be obtained. , and the slag removal performance deteriorates.

Al, together with the above-mentioned V, is a key component in this invention. It is difficult to refine the crystal grains with T1 alone in welded metal that has been welded with high heat input, and this is the reason why IjjIs1 welding of 7-elite stainless clad steel has not been put into practical use. However, the inventors along with Ti! It has been found that by adding a combination of , it is possible to refine the crystal grains even in large heat inputs such as overlay welding. The lower limit is 0.2%, and if it exceeds 80%, spatter will increase during welding and the toughness will deteriorate.

Next, the effects of this invention will be made clearer with reference to examples.

Example 1 In each composition shown in Table 1, s0t! j ring electrode and commercially available 5in2-0aO-muj,O,-OaF, system 7
Two layers of copass welding were performed using LAX, and the slag removability and microscopic structure were examined while welding. Also, the toughness is 49
The samples that had been heat treated at 0°C for a period of time were investigated.

In addition, the welding base material here used f3E3f/ shown in Table #I2 ◇ Table 2 The welding conditions in Tables 1 and 2 are JrJOA X JJ'V
x/jell/min, and the test results are shown in Table 3.
O shown in Table 4 From Tables 3 and 4, it is clear that the effectiveness of M1 on microstructure refinement during high heat input welding and V on slag' peelability is clear. In addition, for samples with insufficiently refined structures, 716
2,166 and A? As shown in Table 4, the example of the present invention has a very poor impact value, but on the other hand, the example of the present invention, in which the addition of (muj+Ti) has been sufficiently refined, exhibits a good impact value.

○: Good Δ: Slightly good ×: Defective cylinder 4 For the surface sample layers 1 and 19, Mu1 did not affect the crystal grain size, and the effects are compared and shown in FIG.

In the above examples, the results were shown when carbon steel was used as the base material, but the present invention can be applied to any base material such as low alloy steel, austenitic stainless steel, and non-ferrous steel.

As mentioned above, the welding electrode of this invention is the first to be successfully put to practical use in the production of 7-elite stainless clad steel by intuitive welding, and it achieves microstructural refinement without deteriorating slag removal properties. However, it is possible to obtain ferritic stainless clad steel, which is widely used in oil refining, petrochemical plants, etc., without worrying about stress corrosion cracking, and is especially advantageous in terms of reliability and efficiency.

[Brief explanation of the drawing]

FIG. 1 <al, <bl are micrographs comparing the structure of the weld metal deposited by the overlay welding electrode in terms of the influence of mulch on the crystal grain size.

Claims (1)

[Claims] L carbon 0.12 weight below, silicon /, 0 weight or less, manganese J, O weight or less, chromium //~〃including heavy weight, and O0 reference~/, /weight≦niobium and 0
．． A 7-elite system characterized by having a composition containing vanadium of J~0.9 weight, together with titanium ram of 00 JN, O weight≦, and aluminum of O, Co~/,0 weight arc. Stainless steel sensual welding electrode/