KR20180078098A - Welding method of pre-swirl stator for stern of ship - Google Patents

Abstract

Provided is a method for welding the pre-swirl stator of a ship stern part, comprising: a step of preparing a pre-swirl stator (PSS) having a predetermined thickness and having a double bevel angle, which includes a first groove defined by a first inclination surface formed at a first bevel angle and a second groove defined by a second inclination surface formed at a second bevel angle smaller than the first bevel angle; a step of performing root pass welding the root part of the pre-swirl stator with a predetermined root gap and a root surface with respect to the stern part boss of the ship; a step of performing regular welding for the pre-swirl stator and the stern part boss; and a step of performing heat treatment after the regular welding. In this configuration, welding quality can be ensured by securing the view of a welding part, the notch stress can be reduced by minimizing the discontinuous section of the welding part, and sound welding can be formed through post-heat treatment.

Description

[0001] WELDING METHOD OF PRE-SWIRL STATOR FOR STERN OF SHIP [0002]

The present invention relates to a method for welding a pre-swirl stator to a front portion of a stern propeller of a ship.

A technique for saving fuel by installing a pre-swirl stator in front of the stern propeller is known

The current-stabilizing wing is attached to the front part of the propeller with four fixed wings, which serves to uniformly flow the water flowing into the propeller from the stern section.

As a result, the ship showed about 3 ~ 5% of fuel saving effect compared with the existing ship, and the same fuel showed a speed increase of about 0.24 knots.

In the case of container ships equipped with large-sized engines, the energy saving effect is more effective than that of a small-sized engine because the exhaust gas temperature is high and the amount of exhaust gas is large.

According to the prior art, a current-carrying blade is welded to the stern boss with a plate portion additionally connected to the stern boss. That is, according to the prior art, the current-carrying wing is welded to the stern boss through welding via a plate to the part connected to the stern part boss after being cast by casting.

One end of the plate is first welded to one side of the current holding blade, and the other end of the plate is welded to the stern part boss. According to the conventional technique, welding is performed through a narrow welding space due to having such a welding structure, so that the weldability is very poor and the welded portion is geometrically discrete and has a problem of being poor in fatigue strength .

Korean Patent Publication No. 10-2015-0012786 Korean Patent Publication No. 10-2004-0017342

It is an object of the present invention to improve the welding structure of the electric current stabilizing blades so that the welding can be easily carried out in the open space, so that the probability of welding defects is much less, the excellent welding quality can be ensured, The present invention provides a method of welding a current stator blade at a stern of a ship which is easy to fatigue strength by reducing notch stress.

According to an aspect of the present invention, there is provided a method of manufacturing a semiconductor device, the method comprising: forming a first groove defined by a first inclined surface formed at a first inclination angle and a second inclined surface formed by a second inclination angle smaller than the first angle, Preparing a current stabilizing blade (PSS) having a double angle of refraction made of a second groove; A step of performing a multi-layer welding with the root portion of the current holding vane being a predetermined root gap and a root surface with respect to the stern portion boss of the ship; Performing the main welding on the current fixing blade and the stern boss; And performing the post-welding heat treatment. The present invention also provides a method of welding a current stator blade of a ship stern section.

The root portion may be formed at a position offset from the center line of the thickness of the current fixing vane, and the current fixing vane may be defined by a thick thickness side and a thin thickness side on the root portion.

The root portion may be located at one-third of the thickness direction of the current fixing vane.

And the superficial layer may be formed on the thick-thickness portion side of the current fixing blade.

The step of performing the main welding includes: forming a primary intermediate layer on the sublayer; Forming a backside intermediate layer and a backside surface layer on the back surface of the sublayer; And forming a secondary intermediate layer and a surface layer on the primary intermediate layer.

The method may further include a gouging step of processing the back surface of the sublayer between the step of forming the primary intermediate layer on the sublayer and the step of forming the back surface intermediate layer and the surface layer on the back surface of the sublayer.

The super-layer welding and the main welding can be performed by a fluxed core arc welding method.

The heat input amount of the super-layer welding may be larger than the heat input amount of the main welding.

The heat input amount of the super-layer welding is 25 to 40 KJ / cm 2, and the heat input amount of the main welding is 25 to 40 KJ / cm 2.

The thickness of the current fixing blade may be 130 to 410 mm.

In the post-welding heat treatment step, the holding time may be 1.2 Hr / in, and the holding temperature may be 610 ± 10 ° C.

In the gouging step, at least one of carbon arc welding and grinding can be performed.

A preheating step of a minimum preheating temperature of 80 캜 is performed and a maximum interlayer temperature of 250 캜.

The super-layer welding and the main welding can be performed in a vertical upright posture. The welding layer of the first groove may be formed of a straight bead, and the welding layer of the second groove may be formed of a weaving bead.

According to the present invention, there is an advantage that the current fixing vane is formed as a complete casting product having a double angle of improvement so that all welds can proceed from the outside, thereby ensuring the quality of the welded portion and securing the quality.

According to the present invention, the current-stabilizing vane is formed into a complete casting with a double angle of improvement, and the arrangement structure of the superstructure and the main welding layer is improved so that an unexpected behavior So that welding deformation can be prevented.

According to the present invention, it is possible to form a sound weld by removing the residual stress that contributes to fatigue crack through post-heat treatment.

According to the present invention, notch stress can be reduced by minimizing the discontinuous portion of the welded portion.

FIG. 1 is a view illustrating a state where a current fixing blade is welded to a stern boss according to an embodiment of the present invention.
2 is a cross-sectional view taken along the line Π-Π in FIG.
3 is a view for explaining a welding state of the stern part boss according to the present invention.
FIG. 4 is a flowchart illustrating a process of welding the current fixing wing to the stern boss according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be apparent to those skilled in the art that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, It is provided to let you know.

FIG. 1 is a view showing a state where a current fixing blade is welded to a stern boss according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along a line Π-Π in FIG.

Referring to FIGS. 1 and 2, a pre-swirler stator (PSS) 30 is welded to a stern boss 10 of a ship. The stern boss 10 is made of a casting product and the current holding vane 30 is also made of a full casting product.

The current fixing vane 30 has a predetermined thickness T1 and is formed at one end with a first inclined surface 36 having a first improved angle b ° with respect to the welding surface 11 of the stern part boss 10, ) Having a second groove (35) defined by a first groove (33) defined by a first angle (?) And a second angle (? Respectively. The first improvement angle b ° may be, for example, 0 to 40 °, and the second improvement angle a ° may be 55 to 80 °.

The first groove 33 formed by the first inclined face 36 having the relatively large first inclination angle b ° has a sufficient space for the torch 1a of the welding apparatus 1 to be sufficiently inserted It is possible. The second groove 35 formed by the second inclined surface 37 having the second improvement angle (? °) has a relatively small welding space to prevent the welding portion from being increased.

That is, when the first inclined surface 36 is formed along the thickness direction and the longitudinal direction of the PSS 30, the inner volume of the groove is increased to form a relatively large number of weld layers, . In consideration of this point, the present invention proposes a current stabilizing blade (30) having a double improvement angle structure.

The current fixing vane 30 is formed with the root portion 31 protruding from the welding face 11 of the stern boss 10 by such double angle improving structure.

The root portions 31 are arranged asymmetrically along the thickness direction of the current holding vane 30. [ That is, the root portion 31 is disposed at a position eccentric to one side from the center axis C on the thickness side of the current fixing vane 30. [ That is, the thick portion of the current holding vane 30 (T2, hereinafter referred to as "first thickness portion side") and the thick thickness portion side (T3, "second thickness portion side Quot;). ≪ / RTI > The root portion 31 may be located at a position 1/3 along the thickness direction from one side of the current holding vane 30.

The eccentric arrangement of the root portion 31 as described above facilitates the deformation control of the welded portion. Deformation control during welding of the current-stabilizing vane (30) is very important. If a load is applied to the current-carrying vane (30) in the state of welding deformation, unpredictable behavior due to anomalous external force may occur, which is a very threatening factor to the welded structure. In case of abnormal behavior, there is a high possibility that the flow of the welding fluid is expected to be out and the welding deformation is likely to occur.

Therefore, the present invention is characterized in that the root portion 31 is eccentrically disposed on one side of the center axis C on the thickness side of the current holding vane 30, and the superstructure L1 (described later) (L2 to L4, to be described later), the deformation control during the welding of the current fixing vane 30 is effectively performed.

The total thickness T1 of the current fixing vane 30 may be in the range of approximately 130 to 405 mm. The total thickness T1 of the current fixing vane 30 may be 137.5? T1? 405 mm.

For example, the current holding vane 30 can be cast to about 275 mm in thickness using C480UW of material.

As a welding apparatus to which the present invention is applied, for example, a semi-automatic Flux Cored Arc Welding (FCAW) apparatus 1 may be used. FCAW uses flux cored wire with the flux inside the wire used for welding.

FCAW welding is a process of melting molten metal by arc heat by supplying filler (wire) continuously to the base metal, shielding it by flux or flux embedded in the wire, and using shielding gas or not.

According to one embodiment of the present invention, the protective gas is not used, the wire protrusion length of the FCAW is approximately 20 to 25 mm, and the gas flow rate is 25 to 45 l / min. The welding material, ie the wire, may be used A5.20 E71T-9C / -12C / -J.

According to one embodiment of the present invention, the welding posture can be a vertical upside. That is, according to the present invention, the weld line of the welded electric current fixing vane 30 is fixed to the jig of the work platform so as to be in a vertical posture, the nozzle of the welding apparatus 1 is brought into contact with the lower end of the electric current fixing vane 30, The welding can be proceeded.

Hereinafter, a welding method of the current fixing vane 30 having the double angle of refraction configured as described above will be described.

FIG. 3 is a view for explaining a welding state of the stern part boss according to the present invention, and FIG. 4 is a flowchart for explaining a process of welding the current fixing wing of the present invention to the stern part boss.

2 to 4, the welding method includes a step S10 of preparing a current fixing blade 30 having a double angle of improvement, a second layer welding step S30, a main welding step S40, Step S50.

The current stabilizing vane 30 preparation step 10 having a double improvement angle may be formed by a casting method in which the material is heated at a temperature higher than the melting point to make a liquid and poured into a mold of the current fixing vane 30 have. The electric current stabilizing vane 30 has a full casting water shape in which the whole is integrally formed.

In the super-layer welding step S30, the welding wire of the current fixing blade 30 and the stern boss 10 are fixed through a separate fixing jig so as to be vertical. Here, the current fixing vane 30 and the stern boss 10 can be brought into the usable contact state by the usable contact step S20. The root portion 31 of the current holding vane 30 may have a root distance r of 1 to 5 mm and a root face f of 1 to 4 mm, for example.

In this state, the welding apparatus 1, for example, the torch 1a of the flux cored arc welding apparatus 1 is positioned on the lower end side of the current holding vane 30 and the stern boss 10, 1 a). That is, the superstructure L1 is welded in the vertical upward position.

The sublayer L1 may be formed in one pass or more. In the drawing, it is shown that the layer L1 is formed by one pass. In the L1 welding, the current-stabilizing vane 30 is welded to the torch (not shown) of the welding apparatus 1 via the first groove 33 defined by the first inclined surface 36 having the first angle of reflections b & 1a can be easily inserted, so that a smooth welding operation can be performed.

As the first groove 33 forms a narrow space, the superstructure L1 is formed in a linear bead shape. The layer L1 is formed on the thick portion, that is, on the side of the second thickness T3, with the root portion 31 as the center.

Layer L1 welding can be carried out under the following conditions.

(1) Welding method: Flux cored arc welding (FCAW)

(2) Welding rod (wire) Diameter: 1.4 mm

(3) Polarity: DCEP

(4) Current: 190 ~ 250A

(5) Voltage: 20 ~ 27V

(6) Traveling speed: 9 ~ 11cm / min

(7) Heat input: 25 ~ 40KJ / cm

The available fingers performed in the above-described allowable welding step S20 may be performed at least 50 mm or more in the super-layer L1 welding condition.

The welding step S40 includes a step S41 of forming a primary intermediate layer L2 on the welded superstructure L1 and a step S2 of forming a thin first thickness side T2 of the superstructure L1 (S43) of forming a back surface intermediate layer and a back surface layer (L3) on the intermediate layer (L2) and forming a secondary intermediate layer and a surface layer (L4) on the primary intermediate layer (L2).

This unprecedented behavior due to an abnormal external force can be prevented by applying a load to the current holding vane 30 according to the present welding sequence.

That is, according to the present invention, the root portion 31 of the current holding vane 30 is disposed eccentrically from the center axis C on the thickness side of the current holding vane 30, 31 are formed on the thick second thickness side T3 and the welded layers L2, L3, L4 are formed by the main welding procedure as described above, the deformation control during welding can be effectively performed .

This welding can be carried out under the following conditions.

(1) Welding method: Flux cored arc welding (FCAW)

(2) Welding rod (wire) Diameter: 1.4 mm

(3) Polarity: DCEP

(4) Current: 200 ~ 280A

(5) Voltage: 20 ~ 27V

(6) Moving speed: 10 ~ 12cm / min

(7) Heat input: 25 ~ 40KJ / cm

This weld has a smaller amount of heat input than the superstructure (L1) welding. This heat input can be achieved through changes in current and travel speed as compared to superstructure (L1) welding. That is, the welding method, the diameter of the electrode (wire), the polarity, and the voltage are substantially the same.

The welding current mainly relates to the melting amount of the wire and the penetration of the base material, and the wire melting rate almost increases in proportion to the current. For example, when welding is performed at the same speed, if the welding current is increased, the welding amount increases and the bead width becomes larger and the bead height becomes higher.

The amount of heat input to the weld is the amount of heat supplied to the weld during welding and is the amount of heat applied per 1 cm of weld bead. If the amount of heat input is large, the cooling rate is slow, and there is a large amount of time to diffuse due to unevenness in concentration, and the temperature gradient on the base material side due to the sub-cooling of the gneiss is low, thereby facilitating the growth of dendrites and celluloses. As the heat input increases, the cooling rate becomes slower and the ductility increases and the hardness value decreases. On the other hand, as the amount of heat input decreases, martensite is generated, the hardness value increases, and the embrittlement becomes stronger.

According to the present invention, the amount of heat input at the time of welding the superstructure (L1) is controlled to be larger than the amount of heat input at the time of welding in accordance with the relationship of the heat input amount. As a result, it is possible to increase the welding amount between the root gaps when the superstructure L1 is welded, thereby improving the welding effect.

As the second groove 35 having a relatively small internal volume is formed by the second inclined surface 37 having the second angle of refraction a ° in the main welding step S40, L3, and L4) can be reduced, so that the number of welders and the amount of welding can be reduced.

Most of the welding layers L2, L3 and L4 formed in the present welding step S40 have weaving beads. However, the layers of the welding layers L2 and L3 which are close to the sublayer L1 may have straight beads. In this way, the welded layers adjacent to the layer L1 can substantially belong to the first grit portion 35. In this case, it is not easy to form the weaving beads by shaking the end of the wire from side to side. For example, two to four passes after the superstructure L1 may be formed as straight beads.

A step S41 of forming a primary intermediate layer L2 on the welded superstructure L1 and a step of forming a superficial intermediate layer and a backside superficial layer on the surface of the superficial layer L1, that is, The back gouging step S42 of the layer L1 may be further included during the step S43 of forming the layer L3. Carbon arc gouging and / or grinding may be performed in the back gouging step (S42).

When the root gap (r) is less than 3 mm, grinding and carbon arc gouging or a combination thereof can be gouged and the minimum grinding and gouging depth can be 6 mm.

In the post-heat treatment step (S50), the holding time is 1.2Hr / in and the holding temperature is 610 占 0 占 폚. According to the present invention, the post-heat treatment is more important since the current fixing vane 30 is formed of the complete casting including the welded portion, the welded portion is relatively increased.

That is, as the thickness of the welded portion becomes thicker, welding residual stress is generated. Post-heat treatment is performed to eliminate residual stress, alleviate stress concentration, and stabilize the structure.

In addition to the above-mentioned configuration, according to the present invention, the minimum preheating temperature can be set at 80 캜 and the maximum interlayer temperature can be set at 250 캜.

That is, the welding surfaces of the base material surfaces, that is, the stern part bosses 10 and the current fixing vanes 30, before the super-layer welding (S30), super-layer welding (S30), or main welding (S40) It is possible to prevent cracking of the welded portion and its heat affected portion by heating.

The interlaminar temperature refers to the base metal temperature of the welded portion welded by the pass welding heat immediately before the arc is generated in the multi-pass welding. In the present invention, the maximum interlaminar temperature is 250 캜 and the welding efficiency can be improved.

Although the present invention has been described with reference to the accompanying drawings and the preferred embodiments described above, the present invention is not limited thereto but is limited by the following claims. Accordingly, those skilled in the art will appreciate that various modifications and changes may be made thereto without departing from the spirit of the following claims.

1: welding device 1a: torch
10: stern part boss 30: current fixing wing
31: Root part b °: 1st improvement angle
36: First inclined plane a °: Second improved angle
37: second inclined surface

Claims (15)

And a second groove defined by a second groove defined by a first groove defined by a first inclined surface formed at a first angle of inclination and a second inclined surface formed by a second inclined angle smaller than the first inclined angle, (PSS) having a first end and a second end;
A step of performing a multi-layer welding with the root portion of the current holding vane being a predetermined root gap and a root surface with respect to the stern portion boss of the ship;
Performing the main welding on the current fixing blade and the stern boss; And
And performing the post-welding post-welding heat treatment. [2] The apparatus according to claim 1, wherein the root portion is formed at a position offset to one side from a thickness center line of the current fixing vane, wherein the current fixing vane has a thick thickness portion and a thin thickness portion side around the root portion, Way. 3. The method according to claim 2, wherein the root portion is located at one-third point along the thickness direction at one side of the current fixing vane. The method according to claim 2, wherein the superstructure is formed on the side of the thick-thickness portion of the current fixing blade. 5. The method of claim 4, wherein the step of performing the main welding comprises: forming a primary intermediate layer on the sublayer;
Forming a backside intermediate layer and a backside surface layer on the back surface of the sublayer; And
And forming a secondary intermediate layer and a surface layer on the primary intermediate layer. 6. The method according to claim 5, further comprising the step of forming the first intermediate layer on the superstructure layer and the gouging step of treating the back surface of the superstructure layer between the step of forming the backside intermediate layer and the surface layer on the back surface of the superstructure layer, Welding method of current - holding wing. The method according to claim 5, wherein the super-layer welding and the main welding are a flux-cored arc welding method. 8. The welding method according to claim 7, wherein the amount of heat of the super-layer welding is larger than the amount of heat of the main welding. The method according to claim 8, wherein the heat input amount of the super-layer welding is 25 to 40 KJ / cm and the heat input amount of the main welding is 25 to 40 KJ / cm. The method as claimed in claim 8, wherein the thickness of the current fixing blade is 130 to 410 mm. The method according to claim 10, wherein the holding time is 1.2 hr / in and the holding temperature is 610 占 0 占 폚 in the post-welding heat treatment step. The method according to claim 6, wherein at least one of carbon arc welding and grinding is performed in the gouging step. The method according to claim 1, wherein the minimum preheating temperature is 80 占 폚 in addition to the welding preheating step, and the maximum interlaminar temperature is 250 占 폚. The welding method according to claim 1, wherein the super-layer welding and the main welding are carried out in a vertical upright posture. The method of claim 1, wherein the weld layer of the first groove is formed as a straight bead,
Wherein the welding layer of the second groove is formed of a weaving bead.

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