JPS6188999A - Coated electrode for stainless steel - Google Patents

Abstract

PURPOSE:To make possible the formation of a satisfactory penetration bead in all welding attitudes by adding a specific ratio each of Cr, Ni and N to a core wire, adding an adequate ratio of a deoxidizing agent such as Si or Al thereto and controlling the compsn. limit value of the carbonate, metallic fluoride, etc. in a coating material. CONSTITUTION:The core wire incorporated therein with 18-30wt% Cr, 4-13% Ni and 0.07-0.20% N is used for the core wire of a coated electrode for high- nitrogen Cr-Ni 2-phase stainless steel. On other hand, 40-65wt% carbonate, 2.0-9.5% metallic fluoride, <=8% (TiO2+ZrO2) and 8-16% SiO2 are incorporated into the coating material. Also, 1.0-2.2% Si and 0.1-2.0% (Ti+Al) are incorporated as the deoxidizing agent therein in terms of the weight ratio of the wire with respect to the total of the core wire and coating material and 1.0-3% Mn and 2.0-5.0 Mo are incorporated therein as the alloy elements for adjusting mechanical properties, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high nitrogen Cr--Ni two-phase stainless steel coated arc welding cup.

[Conventional technology]

Duplex stainless steel with a mixture of ferrite and austenite phases suffers from pitting corrosion and corrosion in an environment containing C1- ions.
Conventional Cr has better resistance to crevice corrosion, stress corrosion cracking, etc.
-Ni is attracting attention and being put into practical use because it is superior to austenitic stainless steel.

When welding pipes etc. using duplex stainless steel,
Since it is made of stainless steel, the electrical resistance of the core wire is high, causing a so-called stick burn phenomenon, which causes the problem that good uranami welding cannot be performed. The rod burn phenomenon is a phenomenon in which the Joule heat generated by the resistance causes the coating material to rise in temperature, and the protective tube at the arc generation point exceeds the fire resistance limit, making it impossible to form a sufficient protective tube.As a result, the arc This is a phenomenon in which concentration and droplet transferability deteriorate. Prevent this stick burn phenomenon.

A high-nitrogen Cr-
Ni phase stainless steel Tagawa coated arc welding rods are desired.

That is, duplex stainless steel is 1. : eV It is necessary to be able to easily perform uranami welding of pipes, etc., but as shown in Japanese Patent Publication No. 59-20435, lime titania type or low hydrogen lime type welding rods have satisfactory uranami welding properties. Welding workability is extremely poor, especially in Uranami welding in an upright or upward welding position, and when used in such a position, the repair rate becomes extremely high, which is a significant problem. Therefore, in order to deal with this, we have no choice but to rely on TrG welding, but TIG
Welding methods not only have low welding efficiency, but also have drawbacks such as being extremely weak against It had a fatal drawback that it could not be used for pipeline construction work.

[Problem that the invention seeks to solve]

The inventors of the present invention have conducted various studies on ways to improve the weldability of welding rods for Cr-N+2-phase stainless steel, including the weldability of the welding rods. By adding Cr, Ni, and N and appropriate denitrification agents, and by regulating the compositional limit of the Yarn agent, the formation of a bead in contact with Uranami is good in all welding positions.

We have also developed a high nitrogen Cr-Ni dual phase stainless steel coated arc welding rod which also has good normal weldability.

The object of the present invention is to provide such a welding rod.

[Means for solving problems]

In the present invention, the core wire contains 18 to 30% Cr (hereinafter referred to as weight%).
(simply referred to as %), Ni4-13%, N0007-0.
20%, and one or both of the core and the coating material contains Si1. O~2.2%, Ti and A
The total value is O, 1-2.0%, M n 1, O-3.0
% and Mo2.0 to 5.0%, and 40 to 65% carbon salt resistance based on the total weight of the coating material, 2 to 9.5% metal fluoride, and a total of TiO2 and ZrO2 of 8% or less, 5
This is a high-altitude JCr-Ni dual-phase stainless steel coated arc welding rod characterized by being coated with a coating material containing 16% of i028-16%.

The present invention will be explained in detail below.

First of all, the alloying elements and deoxidizing agents necessary to ensure the mechanical properties and corrosion resistance of the weld metal of the two-phase stainless steel weld metal containing austenite and ferrite phases obtained by the welding rod of the present invention are There is not much difference whether it is added to the core wire or to the coating material, but in order to obtain a good weld metal with little segregation, at least most of the main components C0r and NI should be added to the core wire. ,
The metals added to the coating should be adjusted to the extent necessary to obtain the desired chemical composition of the weld metal using the core wire.

Therefore, in the present invention, 18% or more of Cr and 4% of Ni are contained in the core wire in order to obtain a stable two-phase stainless steel structure of the weld metal, taking into account the alloying elements of the adjusted values to be added to the coating material. However, if Cr exceeds 30%, the ferrite structure becomes too large and sufficient corrosion resistance cannot be obtained.
If the initial content exceeds 13%, the austenite JlIII& will be too large, causing on-field corrosion, and sufficient corrosion resistance will not be obtained.

Therefore, the amount of Cr is limited to 18-30%, and the Ni%j is limited to 4-13%.

N is a strong austenite-forming element in Cr-Ni steel, and for its performance such as corrosion resistance! t11'
Although it is an element that provides a beneficial effect, if N is added only to the coating material, the nitrogen and abrasive grain transferred to the weld metal will not be stable, so in the present invention, most of the nitrogen is added to the core wire. If Nli in the core wire is less than 0.07%, sufficient effects on the above-mentioned performance cannot be obtained.

Moreover, if it exceeds 0.20%, the tendency for blowholes to occur in the Uranami weld will increase. Therefore, N-% of the core wire is 0.07
Limit to ~0.20%.

Next, the carbon in the coating material can maintain a stable arc column atmosphere due to the Co2 scum produced by decomposition, improve the blowhole resistance of the weld metal, and make the welding slag basic so that the welding slag is not involved. It reduces welding defects and slag inclusions, prevents welding defects, and improves mechanical properties. For this purpose, 40% or more carbonate is added to the RP agent as a main component. However, if it exceeds 65%, welding workability deteriorates. Therefore, it is limited to 40-65%.

The carbonates mentioned here include charcoal lime, barium carbonate,
Refers to lithium carbonate or composite additives thereof.

Next, as a result of various studies regarding metal fluorides, we found that reducing the metal fluoride results in finer droplet transfer due to the surface tension of the metal fluoride, and that by increasing the relative carbonate content,
By making the droplet transfer finer and further protecting the welding rod, i! It has become clear that the tube is made more solid and has improved rod burn resistance, which is advantageous for improving Uranami welding performance. Generally, metal fluoride is added to coating materials as a main component to improve the wettability of the weld metal to the base metal, but if it is less than 2.0%, the wettability is insufficient and the weld bead shape becomes poor. .0
% or more. However, if it is added in excess of 9.5%, the wettability improves, but the transferred molten grains during welding become larger.
In addition, the arc blowing force becomes weak and a sufficient Uranami beat cannot be formed. Therefore, it is limited to 20 to 9.5%. The metal fluoride referred to herein refers to fluorite, cryolite, magnesium fluoride, aluminum fluoride, sodium fluoride, potassium fluoride, lithium fluoride, or composite additives thereof.

TiO2 and ZrO2 have the same effect and are used as a slag forming agent and a slag viscosity modifier. If either or both of TiO2 and ZrO2 exceeds 8%, the slag will become too viscous and the welding workability will deteriorate, so the upper limit is 8%. Note that TiO2 here refers to the TiO2 content of rutile, illuminite, and titanium oxide, and ZrO2 refers to the ZrO2 content of zirconia and zircon sand.

5i02 is used for the same purpose as TiO2; if it is less than 8%, the slag viscosity is insufficient and a good welding bead cannot be formed, and if it exceeds 16%, the slag viscosity increases too much and welding workability is poor, especially in upward welding. Become. Therefore 8-16
%. In addition, 5i02 mentioned here is silica sand, &
Refers to the SiO2 content of silicon-resistant compounds such as stone, silica lime, sericite, mica, and kaolin A.

Furthermore, AM, Ti, Si, and Mn are used as deoxidizing agents.

Mg, Zr, etc. are used, but Si is one of the most effective deoxidizing agents, and if Si is less than 1.0% compared to the core wire type, the deoxidizing power is insufficient and pores are generated. Bad, and if it exceeds 2.2%, too much Si will remain in the weld metal, which will not only disrupt the balance of the ferrite amount, but also
It is unsuitable because hot cracking occurs. Therefore 1.0
Limit to ~2.2%.

If the total content of one or both of Ti and Al is less than 0.1% by weight of the core wire, the deoxidizing power will be insufficient and pores will be generated, so it is not suitable, and if it exceeds 2.0%, the cracking resistance of the weld metal will deteriorate. These are limited to 0.1 to 2.0% since they deteriorate. Here, Ti and A may be added to the coating material in the form of a single alloy of each of them.

Since the coating material is basic, Mn has a weak deoxidizing ability, so it is used as an austenite-forming element and for adjusting mechanical properties rather than as a deoxidizing agent. Core line I]! If the M ratio is less than 1.0%, the 151 constant austenite kl cannot be achieved, and if the M ratio is less than 3.0%, the ductility and toughness of the diseased metal will deteriorate. Therefore, it is limited to 1.0 to 3.0%.

Mo is the heart line! I! If the amount ratio is less than 2.0%, the corrosion resistance will not be good, and if it exceeds 5.0%, the corrosion resistance will deteriorate, so it is limited to 2.0 to 5.0%.

Moisture in the coating material is related to the occurrence of blowholes, and 250
After drying the welding rod at ℃, the moisture content (including bound water) is 1
．． If it is in the range of 0% or less, good blowhole resistance is exhibited, so it is preferable to keep it in the range of 1.0% or less.

As described above, according to the present invention, most of the Cr and Ni
By adding N and N, adjusting the appropriate proportions and amounts of carbonates and metal fluorides in the coating material, and adding an appropriate amount of alloy or deoxidizing agent.

2 with excellent uranami weldability in all position welding and excellent corrosion resistance.
It is clear that a phase stainless steel coated arc welding rod is obtained.

Next, a method for manufacturing a welding rod will be described. The Cr-Ni core wire and wave Ya composition powder are kneaded with a binder of hydraulic lath (potassium 11 acid, + 1M sorter + lithium 1 acid L solution), and then turned into a core wire. coated, 25
Dry for 1 hour at 0°C to obtain a coated welding rod.

〔Example〕

Table 1 shows the chemical components of the sample cores. Of these, symbol A is a 20% Cr-10% Ni stainless steel core wire with an N content of 0.04% and is a wire other than Kibatsu 1.

The welding rod had a core wire diameter of 3.2 mm, a length of 350 mm, a coating diameter of 5.2 mm, a potash of silicate, and the welding rod was dried at 250° C. for 1 hour. Regarding moisture, the coating material raw material was also taken into consideration, so the moisture content after drying was 1% or less in all welding rods.

Tables 2 and 3 show welding rod compositions based on combinations of these and coating materials.

Table 4 lists the chemical composition of the total weld metal of these welding rods, the welding workability test results for pipe circumference welding, especially including the Uranami weld bead, and the corrosion resistance test results of the weld metal. Using each of these welding rods, perform stack welding of 5 or more layers on 2-phase stealth m+, starting from the final layer side 3X2
5 x 50 mm of weld metal J1 was collected and polished.

The test was conducted by immersing the sample in a 10% FeCQ3 aqueous solution at 30° C. for 24 hours and determining the level of pitting corrosion. At this time, those in which significant pitting corrosion occurred were judged to be defective, and those in which there was little pitting corrosion were judged to be good.

From the above results, the symbols of the welding rods of the present invention are 3, 4, 5゜6.8,
It is clear that good results can be obtained for Nos. 9, 10, 11, 12. In any welding position, such as circumferential welding, it has excellent arc concentration, welding and welding properties, and can form a good underwave bead.

Claims (1)

[Claims] 1. The core wire contains 18 to 30% by weight of Cr, 4 to 13% by weight of Ni, and 0.07 to 0.20% by weight of N, and the total of the core wire and coating material is converted to a core wire weight ratio. Si, Si
is 1.0 to 2.2%, and the total of Ti and Al is 0.1 to 2.2%.
2.0%, Mn 1.0-3% and Mo 2.0-5
．． 0% carbonate content and 40% carbonate content based on the total weight of the coating material.
~65% by weight, 2.0-9.5% by weight of metal fluoride, T
A high nitrogen Cr-Ni dual phase stainless steel coated arc welding rod characterized in that it is coated with a coating material in which the total of iO_2 and ZrO_2 is 8% by weight or less and SiO_2 is 8 to 16% by weight.