JPH0355231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a process for gas-shielded arc welding of hydrogen-resistant induced steel.

Although it is known that the addition of rare earth elements (hereinafter referred to as "RE") and/or calcium (hereinafter referred to as "Ca") is effective as a countermeasure against hydrogen-induced corrosion, there are problems with weldability during gas-shielded arc welding. be.

The object of the present invention is to improve weldability under such localized conditions.

With the increase in energy demand in recent years, the demand for high-quality pipes has increased further in order to safely and efficiently transport oil or gas resources extracted from extremely cold regions or the deep seabed. The most serious problem for pipe manufacturers and pipe users is pipe breakage during use. Coupled with recent advances in non-destructive testing technology, it has become possible to almost completely eliminate internal defects during pipe manufacturing that can cause fractures. HIC (hereinafter abbreviated as HIC) is extremely difficult to prevent.

Steel materials used not only in pipes but also in environments with many hydrogen sources such as hydrogen sulfide are at risk of HIC due to environmental embrittlement.

On the other hand, in order to prevent such HIC, steel manufacturers have based on various studies that HIC is caused by the bonding of expanded manganese sulfide (MnS) and hydrogen in steel sheets, and that RE and/or Ca It has been discovered that adding S and combining with S to prevent the formation of MnS is effective as a countermeasure against HIC, and has already reached the stage of practical use, and demand for this type of HIC-resistant steel will increase in the future. is expected to continue to increase.

By the way, steel plates are almost always formed into steel structures by welding, and as a result of advances in automatic welding technology, gas-shielded arc welding is now used more frequently than manual welding. A similar example can be found in the case of circumferential welding that connects.

As a result of the inventors' study on the gas-shielded arc weldability of HIC-resistant steel, which is a new steel type as mentioned above, RE and/or Ca were added based on the parameters found by the inventors. However, this adverse effect has different characteristics depending on the form of droplet transfer from the wire, which depends on the welding current.The wire composition and shielding gas composition should be comprehensively selected appropriately for each. It has been found that good gas-shielded arc welding can be performed by this method.

The shielding gas in gas-shielded arc welding is generally CO ₂ alone or a mixture of CO ₂ and an inert gas such as Ar, and the welding wire is made of C, Si, Mn or other gases as necessary. It contains Ni, Cr, Mo, B, etc. as alloy components, and in addition to unavoidably containing P and S, it often contains Al and Ti as deoxidizing agents.

It has been qualitatively known for a long time that RE and Ca in the welding wire composition affect arc characteristics, but in the past these elements were not actively added to wires or steel plates. Since there is no such thing and there is no need for it, the actual situation is completely unknown regarding their adverse effects on shielded gas arc weldability. In addition, in the steel plate
Although there are some reports regarding the influence of RE on arc weldability, in many cases it is essential to add Ca at the same time as RE as a countermeasure against HIC, unless these influences are taken into consideration, gas shielding of HIC-resistant steel It is not suitable for arc welding.

In other words, in the case of conventionally known technology, the specific details of the individual or combined behavior of RE and Ca with respect to arc instability in shielding gas welding, arc instability during welding related to welding conditions, wire composition, and shielding gas composition Not only were the details of the situation not understood, but at the same time, no concrete, quantitative method had been found to deal with it.

As a result of various studies aimed at stabilizing the arc in gas shield welding of HIC-resistant steel, the inventors discovered a special relationship between the above and established a method that makes it possible to simultaneously be.

As a result of studying the gas-shielded arc characteristics of HIC-resistant steel, the inventors found that there is the following relationship between the amount of RE and/or Ca added in a steel sheet and welding workability.

(1) When the shielding gas composition is 100% CO ₂ ,
The influence of RE and Ca is additive according to the component parameter (A) of RE and Ca shown by the following formula, and when the value of parameter (A) exceeds 0.10, the arc becomes disordered and welding becomes extremely unstable. Become.

(A) = ([RE]/0.14) + ([Ca]/0.04) In the formula, [ ] is the indicated component content (wt%) (2) The welding instability phenomenon also depends on the droplet transfer form. The situation is different, and in the case of the following DC reverse polarity, spatter loss occurs abnormally, especially in the so-called globular transition region where the welding current I exceeds about 230A and reaches 600A.

In addition to intense arc generation from RE oxide, Ca oxide, or RE-Ca composite oxide that is formed when parameter (A) is 0.10 or more as described above, the Ti content in the welding wire is 0.03 If it is less than wt%, the tendency of insufficient deoxidation by Ti will combine to cause irregular migration of droplets and explosion of CO gas bubbles.

Therefore, the cause of such arc instability is that the content of RE and/or Ca in the steel sheet is (A) 0.10 according to the parameter shown in the above formula, and the shielding gas is mainly CO ₂ . The overall effects of the oxidizing atmosphere and the amount of Ti in the wire are important points for arc stabilization, which should result in smooth globular transfer of droplets.

Figure 1 comprehensively shows the influence of parameter (A), sputter loss, shielding gas composition, and Ti amount in the wire in the globular transition region.
When the shielding gas composition is CO ₂ 100vol% and the Ti content in the wire is less than 0.03wt% (

Claims (1)

[Scope of Claims] 1. Hydrogen-resistant steel containing rare earth elements and/or calcium as hydrogen-induced inhibiting components in an amount such that the value of parameter (A) according to the following formula according to the amount of these components is 0.10 or more. As a welding base material,
When performing shield gas welding using carbon dioxide gas with DC reverse polarity at a welding current exceeding 230A and up to 600A, welding wire with a titanium content of 0.03~
Gas-shielded arc welding method for hydrogen-resistant induced steel, characterized by applying globular transition zone arc stabilization means of selecting 0.20wt%. (A) = ([RE]/0.14) + ([Ca]/0.04) In the formula, [ ] is the indicated component content (wt%)