KR20130036895A - Method for welding using wire for shielded metal arc welding - Google Patents

Abstract

PURPOSE: A welding method using a wire for coated arc welding is provided to minimize reconstruction and to ensure quality stability by satisfying target properties such as intensity and hardness after post-annealing and welding. CONSTITUTION: A welding method using a wire for coated arc welding welds the outer face of a welded part with a gas tungsten arc welding method in the root part of a welding joint through a shielded metal arc welding method. The welding wire used in the coated arc welding method contains 0.1wt% or less of carbon, 1.25-1.75wt% of manganese, 0.08wt% or less of silicon, 0.025wt% or less of sulfur, 0.025wt% or less of phosphorus, and 0.25-0.45wt% of molybdenum. The heat input amount of the welding wire is 10-15kJ/cm. [Reference numerals] (AA) Heat treatment effect; (BB) Tensile strength MPa; (CC) Hardness;

Description

Welding Method for Clad Arc Welding {Method for Welding using Wire for Shielded Metal Arc Welding}

The present invention relates to a coated arc welding wire and a welding method using the same, and more particularly, to a welding method using a coated arc welding wire that can satisfy a target property even after post-heat treatment.

For joining steel materials, a welding method for melting and joining a base metal or a wire is widely used.

In particular, the welding method is widely used when drying a plant or a ship in which a large amount of steel is used.

For example, welding is performed for joining AISI 4130 steel used for drilling system pipe of a drill ship having an excavation function, and FIG. 1 is a view showing a portion where two steels are welded together.

When welding pipes, if foreign matters such as slugs occur inside the pipes, it may be difficult to remove them later. Therefore, gas tungsten arc welding (GTAW), in which the slug does not occur in the root part of the pipes, may occur. After welding 1 ~ 3 times by the method, the outer face part is welded by Shielded Metal Arc Welding (SMAW) method.

The wire used for the GTAW welding or the SMAW welding basically applies a wire that exhibits higher physical properties than that of the base metal. The chemical composition of the wire currently used for welding the AISI 4130 steel is as shown in Table 1 below.

Welding method element carbon
C manganese
Mn silicon
Si sulfur
S sign
P chrome
Cr nickel
Ni molybdenum
Mo Copper
Cu GTAW at least 0.07 1.60 0.50 - - - - 0.40 - maximum 0.12 2.10 0.80 0.025 0.025 - 0.15 0.60 0.4 SMAW at least 0.07 1.65 0.20 - - - - 0.25 - maximum 0.15 2.00 0.60 0.025 0.025 - 0.90 0.45 -

On the other hand, when welding as described above, residual stress is generated in the welded area. In order to remove such residual stress, post-heat treatment (PWHT) is performed, and in general, post-heat treatment at about 690 ° C. for about 1 hour. Do

On the other hand, the welded part must satisfy the original physical properties of the base metal even after the post-heat treatment process. For example, after welding, AISI 4130 steel should satisfy tensile strength greater than 724 MPa, impact toughness greater than 0.38 mm at -45 ° C, and hardness less than 22 based on Rockwell hardness (HRC).

By the way, the properties of each base material and wire before welding satisfy the above criteria, but the hardness value of the face part welded by SMAW welding method after welding and post-heat treatment process frequently exceeds HRC 22, which is the reference value. When the hardness value is adjusted to the reference value, the strength of the root portion welded by the GTAW welding method is lowered, which makes it difficult to approve construction.

An object of the present invention is to provide a welding method using a coated arc welding wire that can satisfy physical properties such as strength and hardness even after undergoing welding and post-heat treatment.

In order to solve the above problems, according to an embodiment of the present invention, the coating arc welding method (SMAW) in the face portion of the outer side of the welded portion of the weld joint by gas tungsten arc welding (GTAW) : When welding by shielded metal arc welding, the welding wire used for the coated arc welding method has carbon (C) of 0.1% by weight or less, manganese (Mn) of 1.25-1.75% by weight, and silicon (Si) of 0.08% by weight. Use the coated arc welding wire containing less than or equal to 0.025% by weight of sulfur (S), less than 0.025% by weight of phosphorus (P) and 0.25 to 0.45% by weight of molybdenum (Mo). When performing coating arc welding, a welding method using a coated arc welding wire having a heat input amount of 10 KJ / cm to 15 kJ / cm is provided.

The coated arc welding wire may further contain 0.15 wt% of chromium (Cr), 0.15 wt% of nickel (Ni), and 0.05 wt% of copper (Cu).

In addition, the heat treatment effect of the post-heat treatment conditions of the post-heat treatment process performed after the coating arc welding may be 17000 to 17300.

In addition, the post-heat treatment condition of the post-heat treatment process performed after the coating arc welding may be performed at a temperature of 600 ° C. for 70 to 80 minutes.

According to the welding method using the coated arc welding wire of the present invention, the strength, hardness and impact toughness values can be satisfied even after the welding and post-heating process when welding the AISI 4130 grade steel, so that the integrity of the welded portion is considered. In addition, it is possible to secure quality safety and minimize rework, thus eliminating air delays and reducing city park prices.

1 is a cross-sectional view showing a portion where two steels are welded together;
Figure 2 is a graph showing the change in hardness value and tensile strength value of the welded portion according to the heat input and heat treatment influence.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In describing the present embodiment, the same designations and the same reference numerals are used for the same components, and further description thereof will be omitted.

1 is a cross-sectional view showing a portion in which two steels are joined by welding, and when explaining the welding method using the coated arc welding wire of this embodiment, the joined steel (base metal) is made of AISI 4130 grade steel. An example of welding a pipe made of a material will be described.

In addition, the piping inner part of the part joined by welding is called a root part, and the part which faces outward from the said root part is called a face part. In addition, a portion of the wire which is not a base metal is melted during welding is referred to as W / M (Weld Metal), and an interface where the base material and the wire are melted is referred to as F / L (Fusion Line). In addition, the portion of the base material affected by the heat generated during welding will be referred to as a heat attacted zone (HAZ).

As shown in Figure 1, when welding the pipe, if a foreign material such as slug (slag) in the pipe may be difficult to remove later, the gas tungsten arc that does not generate a slug in the root portion of the pipe After welding 1 to 3 times by GTAW (Gas Tungsten Arc Welding) method, the outer face part is welded by Shielded Metal Arc Welding (SMAW) method.

At this time, the chemical composition of the wire used for gas tungsten arc welding (GTAW) is shown in Table 2 below.

Welding method element carbon
C manganese
Mn silicon
Si sulfur
S sign
P chrome
Cr nickel
Ni molybdenum
Mo Copper
Cu standard GTAW at least 0.07 1.60 0.50 - - - - 0.40 - AWS A5.28 maximum 0.12 2.10 0.80 0.025 0.025 - 0.15 0.60 0.4

That is, carbon (C) is 0.07 to 0.12 weight percent, manganese (Mn) is 1.60 to 2.10 weight percent, silicon (Si) is 0.50 to 0.80 weight percent, sulfur (S) is 0.025 weight percent or less, and phosphorus (P) is Welding wires of less than 0.025 weight percent, nickel (Ni) 0.15 weight percent, molybdenum (Mo) 0.40 to 0.60 weight percent, and copper (Cu) 0.4 weight percent or less can be used.

Applicant tested using a welding wire having an element content of the above described in Table 3 below.

C Mn Si S P Cr Ni Mo Cu 0.10 1.9 0.6 0.005 0.01 - 0.05 0.5 0.1

In addition, the chemical composition of the wire used for coating arc welding (SMAW) is shown in Table 4 below.

Welding method element carbon
C manganese
Mn silicon
Si sulfur
S sign
P chrome
Cr nickel
Ni molybdenum
Mo Copper
Cu standard SMAW at least - 1.25 - - - - - 0.25 - AWS A5.5 maximum 0.10 1.75 0.80 0.025 0.025 - - 0.45 -

That is, carbon (C) is 0.1 weight percent or less, manganese (Mn) 1.25-1.75 weight percent, silicon (Si) 0.08 weight percent or less, sulfur (S) 0.025 weight percent or less, phosphorus (P) 0.025 weight Molybdenum (Mo) may be used in welding wires of AWS A5.5 specifications containing 0.25 to 0.45 weight percent.

The present application was tested using a welding wire having an element content of the above described in Table 5 below.

C Mn Si S P Cr Ni Mo Cu 0.07 1.5 0.4 0.01 0.015 0.15 0.15 0.35 0.05

As disclosed in Table 5, carbon (C) and manganese (Mn), silicon (Si) and sulfur (S), phosphorus (P) and molybdenum (Mo) have elemental content within the ranges shown in Table 4, and AWS Additional chromium (Cr), nickel (Ni) and copper (Cu) content were not included in the A5.5 specification.

In performing the coating arc welding (SMAW) as described above, the heat input condition is such that the heat input amount is between 10 KJ / cm and 15 KJ / cm, and the heat input conditions when the applicant experiments are as shown in Table 6 below. .

Current (A) Voltage (V) Speed (cm / min) Heat input amount (kJ / cm) 1 ^st 105 22 12.9 10.8 2 ^nd 105 22 13.3 10.6

Here, the heat input amount can be calculated by multiplying the current A, the voltage V, and the traveling speed (minutes / cm) of the wire.

In addition, the Applicant conducted the experiment twice at different speeds for the accuracy of the experiment.

In addition, the heat input conditions of the gas tungsten arc welding (GTAW) may also be the same as the coated arc welding (SMAW). Of course, the heat input conditions of the gas tungsten arc welding (GTAW) may be set differently from the heat input conditions in the coating arc welding (SMAW).

After the welding is completed with the wire and the heat input conditions as described above, the post heat treatment should be performed, wherein the post heat treatment conditions are as shown in Table 7 below. In addition, the applicant carried out the experiment twice in the post-heat treatment conditions having different holding time for the accuracy of the experiment.

Temperature (℃) Retention time (minutes) Heat treatment effect 1st 600 70 17082 2nd 600 80 17133

Here, the heat treatment effect (Tempering effect) can be calculated by the following equation.

Here, T is a temperature (K absolute temperature unit) applied during the post-heat treatment, and t is a unit of time or seconds as the holding time.

In addition, C is a material constant, the material constant can be calculated as follows.

or,

On the other hand, Table 8 shows the results of testing the physical properties of the parts subjected to gas tungsten arc welding (GTAW) and coated arc welding (SMAW) under the above heat input conditions and post heat treatment conditions.

Test Type location unit result 1st 2nd The tensile strength MPa 725 724 726 731 729 731 Impact toughness W / M mm 0.50 0.48 0.69 0.58 0.62 0.64 F / L 0.98 0.88 1.09 1.02 1.05 1.10 F / L + 2mm 1.53 1.63 1.81 1.81 1.75 1.84 F / L + 5mm 1.88 2.08 1.74 1.99 2.10 1.89 Hardness FACE W / M <HRC 22 20.5 20.7 21.3 22.0 21.3 21.9 ROOT W / M 10.6 13.8 16.3 16.2 16.7 16.8 FCAE HAZ 21.5 20.8 20.5 19.9 20.1 19.7 ROOT HAZ <20.0 (-15) <20.0 (-14) <20.0 (-15) <20.0 (-17) <20.0 (-12) <20.0 (-15)

Here, W / M refers to the part where the wire is melted, not the base material, when welding. F / L refers to the interface where the base material and the wire are melted. F / L + 5mm is a part 5mm away from F / L to the base material side.

In addition, FACE W / M is W / M of a face part, ROOT W / M is W / M of a root part. FCAE HAZ is a heat affected portion of the face portion, and ROOT HAZ is a heat affected portion of the root portion.

For example, after welding, AISI 4130 grade steel should satisfy tensile strength greater than 724MPa, impact toughness should be greater than 0.38mm at -45 ℃, and hardness should be less than 22 based on Rockwell hardness (HRC).

As shown in Table 8, after welding of the AISI 4130 grade steel at all positions of the welded portion by gas tungsten arc welding (GTAW) and the welded portion by shielded metal arc welding (SMAW). It can be seen that the satisfaction condition is satisfied.

Figure 2 is a graph showing the change in hardness value and tensile strength value of the welded portion according to the heat input and heat treatment influence.

As can be seen from the graph, the area between the line of tensile strength value and the line of hardness value is the area that satisfies the post-welding condition of AISI 4130 grade steel. It can be seen that / cm, heat treatment influence is in the region of 17000 ~ 17300.

It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the spirit or scope of the invention as defined in the appended claims. It is obvious to them. Therefore, the above-described embodiments should be regarded as illustrative rather than restrictive, and thus, the present invention is not limited to the above description and may be modified within the scope of the appended claims and their equivalents.

GTAW: Gas Tungsten Arc Welding: Gas Tungsten Arc Welding
SMAW: Shielded Metal Arc Welding: Clad Arc Welding
FACE: outer surface of weld
ROOT: inner root of weld
W / M: Weld Metal: Molten metal part during welding
F / L: Fusion Line: Interface where the base metal and wire are melted
HAZ: Heat Attacted Zone: Heat Affected Zone

Claims (4)

When welding to the face of the outside of the part welded by gas tungsten arc welding (GTAW) at the root part of the weld joint by shielded metal arc welding (SMAW),
The welding wire used for the coated arc welding method,
Less than 0.1 weight percent carbon,
Manganese (Mn) is 1.25-1.75 weight percent,
Si (Si) is 0.08 weight percent or less,
Sulfur (S) is 0.025 weight percent or less,
Phosphorus (P) is 0.025 weight percent or less and
Molybdenum (Mo) 0.25 to 0.45 weight percent
Use coated arc welding wire,
When performing coating arc welding using the said covering arc wire,
Welding method using coated arc welding wire whose heat input is 10KJ / cm ~ 15kJ / cm. The method of claim 1,
The welding arc welding wire,
Chromium (Cr) is 0.15% by weight,
Nickel (Ni) is 0.15% by weight and
Copper (Cu) is 0.05% by weight
Welding method using a coated arc welding wire containing more. The method of claim 1,
A welding method using a coated arc welding wire having a heat treatment effect of 17000 to 17300 in post-heat treatment conditions performed after the coated arc welding. The method of claim 1,
The post-heat treatment conditions of the post-heat treatment process performed after the coating arc welding,
Welding method using a coated arc welding wire that is performed for 70 to 80 minutes at a temperature of 600 ℃.

Images