JPH0288390A - Anticorrosion high strength propeller for ship - Google Patents

Abstract

PURPOSE:To provide a marine propeller excellent in high corrosion fatigue strength and impact value by assembling and welding respective propeller blades made of marine propeller material having specified components of anticorrosion property and high strength and divided at the boss portion from each other to be welded to each other at the boss portions with a welding material having same chemical components as the propeller material. CONSTITUTION:Respective marine propeller blades A-D containing 0.08% or less C, 0.1-1.5% B1, 0.1-3% Mn, 16-19% Cr, 4.5-7.5% Ni, 0.5-2% Mo, 0.05-0.5% Al and the remainder substantially consisting of Fo by weight% and divided from each other at the boss portion 1 are assembled and welded to each other with a welding material containing same chemical components as the propeller material at the boss portion 1 to constitute a marine propeller having anticorrosive property and high strength. As a result, since the welds 2 of the divided blades A-D is constituted of the propeller material, i.e., welding material having high corrosion fatigue strength, they are excellent in the anticorrosive property, compared with propellers welded by the use of other welding materials.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a marine propeller used in seawater, and in particular has a corrosion fatigue strength higher than that of currently used steel alloy (mainly nickel/aluminum bronze) propellers. has
The present invention also relates to a marine propeller having a high impact value.

[Conventional technology]

Currently, marine propeller materials include steel alloy materials and nickel.
Aluminum bronze, etc.) are often used because of their relatively excellent seawater resistance and workability. However, steel alloy materials are marine propeller materials with an acid level of 4. ii
The required corrosion fatigue strength in seawater is 18 kl for the cut specimen.
There is a strong desire to develop a marine propeller material that has only about f/d (repetition rate 2 x 10? times) and has higher corrosion fatigue strength.

In addition, the corrosion fatigue strength of current marine propeller materials is significantly reduced due to the mass effect, and for propellers with a diameter of 6 m or more and a weight of 6 tons or more, the corrosion fatigue strength of the propeller body (blade root) in seawater is higher than that of nickel/aluminum bronze. If , about 1
It decreases from 0 to 11 at 9f/dC repetition rate 2X10')t. Therefore, it is desired to develop a propeller material with less reduction in corrosion fatigue strength due to mass effect.

Furthermore, during voyage, marine propellers may collide with foreign objects such as wood, causing their blades to break. In this case, # zero value of steel alloy propeller material (Charpy 2-v notch, room temperature)
/fi5 kgfm/ less than 1, for example 2~a kgt
It's just m/d.

[Il Zhao that the invention attempts to solve]

In view of the above-mentioned state of the art, the present invention aims to provide a marine propeller that has high corrosion fatigue strength and excellent impact value, which were not available with conventional copper alloy propellers.

[Means to solve the problem]

The present invention has a heavy weight of O: 1108 or less, Si: 1lL1
~L5 Sorry, Mn: 111~S%, Or: 16~1
9 sounds, Ni: 45-7.5%, Mo: (
L5~2ts, Mut: 6 propeller blades made in parts at the boss part from a corrosion-resistant high-strength marine propeller material consisting of α05~α5s and the remainder being substantially KF. This is a corrosion-resistant, high-strength marine propeller that is assembled by welding using welded materials.

[Effect] 0. ) Since a propeller material having a specific component (the reason for limiting the components will be described later) O alloy composition is used, the obtained marine propeller is endowed with high corrosion fatigue strength and a dredged impact value.

(2) By manufacturing (casting) the propeller by dividing it into six blades, the casting weight of the six blades is reduced compared to the conventional method.

(By using the same material as the welding material for the 33-split blade when assembling the 33-split blade, high corrosion fatigue strength and 4tI impact value can be obtained at the welded part, and potential difference corrosion of the welded part can be prevented.

[Reasons for limiting the composition of propeller materials and welding materials] O: This substance forms chromium carbide and is an important element that influences the corrosion resistance and corrosion fatigue strength of propeller materials. But 108
If the weight exceeds 1% by weight, chromium carbide will precipitate, reducing corrosion resistance and impairing corrosion fatigue strength, so the upper limit is set at 8 seconds per mouth.

Sl: Ko4. It is necessary to add o as a deoxidizing agent during melting (L11), but if the amount added exceeds t5%, it will become brittle, so the upper limit is set to LSI.

Mn: Similar to this-81, it is necessary to add α1s or more as a deoxidizing agent, but if it exceeds 5%, it will become brittle, so the upper limit is set at 3.

Or=This element is necessary to maintain corrosion resistance and obtain high corrosion fatigue strength, and a minimum of 169I is required. However, since Or is a ferrite-forming element, it is necessary to limit the amount of ferrite to 30% or less.If Cr exceeds 19%, the corrosion fatigue strength decreases, so the upper limit is set at 19%.

11: When the amount of Or added is 16 to 19, Ml
In order to obtain a martensitic structure at room temperature by adding Ml and maintain corrosion resistance, Ml of a minimum tS is required. On the other hand, if the amount of 11 is 7.5, the amount of austenite will be large and the yield strength will decrease, so the upper limit is set to 7.5.
51.

Mo: This element is effective in corrosion resistance and prevention of pitting corrosion, and the addition of Lsso is necessary at the minimum. However, if it exceeds 2s, it becomes brittle and reduces corrosion resistance, so the upper limit t
-2%.

Mut: This substance functions as a deoxidizing agent like Si and Mn, but has a more effective deoxidizing effect and contributes to improving corrosion fatigue strength. If it is less than α05, the effect is small, and if it exceeds α5s, the amount of ferrite increases and the impact value decreases, so the upper limit is set at αSS.

[Implementation row]

Table 1 shows the chemical compositions of the propeller material of the marine propeller of the present invention (hereinafter referred to as the propeller material of the present invention) and comparative materials,
Table 2 shows the chemical composition of current propeller materials. Sample NI&
1 to -4 are materials of the present invention, 5) and 10 are comparative materials, and -11 is a currently used propeller material. Their mechanical properties and corrosion fatigue strength are shown in Table 3.

Comparative materials (-5 to 10) whose chemical components are outside the range specified in the present invention have corrosion fatigue strength in seawater of 25 kgf/-(
Number of repetitions 2x10? ) or less, and the present invention material (-1 to N
This is significantly lower than a4)'s 28-50 kgf/-. The corrosion fatigue test was carried out using a Cuellar rotary bending tester (rotation speed 4450 r, p, m,
The test was conducted at 30°C.

Table 1 The marine propeller of the present invention is cast after being divided into six blades at the propeller boss, and then assembled by welding the boss portions again. The situation is shown in Figure 1. MutBMO in Figure 1,
The four blades are divided by the Dri boss part 1, and after being cast and produced, they are assembled by welding at the boss part 1.

2 indicates a welded part.

Since marine propellers are used in seawater for many years, the boss weld 2 needs to have good corrosion resistance. Therefore, welding materials are required to have good properties such as corrosion resistance, mechanical properties, corrosion fatigue strength in seawater, and weldability. Furthermore, even if the properties of the welding material itself are good, if the potential difference between the base material and the propeller boss 1 in seawater is large, potential difference corrosion will occur at the weld boundary. From the above viewpoint, the welding material used in the present invention has the same chemical composition as the propeller material.

Table 4 shows the chemical components of the welding material used in the present invention (hereinafter referred to as the welding material of the present invention), comparative materials, and commercially available welding materials. Samples -12 to -14 are welding materials of the present invention, N111
5 to Na17 are comparative materials, and -18 and Na19 are commercially available stainless steel welding rods. In addition, welded joint strength tests were conducted using these welding materials and the results are shown in Table 5. The base material of the welded test piece used in the welded joint test was the propeller material of the present invention (rod 1 in Table 1), and its shape was 250 cm long, 200 cm wide, and 25-1 thick with a 60 degree V-opening. Bath welding was previously done by arc welding.

The corrosion fatigue strength of the welded joint in seawater is outside the range of the welding materials of the present invention. Comparative materials -15 to Na17 are below 20 Yuf/- (repetition number 2X10'), and commercially available Na180.3U
831dL), Na1? (8σ8309) is 24 kl
iJf/-. On the other hand, the joint obtained using the welding material of the present invention has a diameter of 29 to 50 yf, which is about the same as the base metal.
/-Darashi is noticeably soaked.

In this way, the marine propeller of the present invention is constructed of propeller materials and welded materials that have high corrosion fatigue strength for both the split blades and welded parts, so compared to propellers welded using other welded materials. Excellent in corrosion resistance etc.

If the diameter of the propeller exceeds 10 m, the weight of the propeller will exceed 40 tons, and the cooling rate will be slow and the mechanical properties will deteriorate due to the mass effect. In recent years, the use of low-speed, large-diameter propellers has increased in order to improve propulsion efficiency. In view of this situation, the marine propeller of the present invention is manufactured by dividing the propeller into six blades at the boss part and casting them so that the mechanical properties and corrosion fatigue strength do not deteriorate due to the mass effect even if the propeller has a large diameter (large weight). As a result, it has become possible to provide a highly efficient propeller with a thinner wall compared to conventional integrated propellers.

These split propellers, Tanikaze, were heated to 900~900 to improve corrosion resistance and seawater corrosion fatigue strength before assembly.
The propeller is solution-treated at 1000°C and rapidly cooled, and the assembled propeller after welding is heat-treated at 650-900°C to remove residual stress caused by welding at the welded portion. This is because even in the propeller material of the present invention, carbides precipitate at the cooling rate during casting of a large propeller, resulting in a decrease in corrosion fatigue strength in seawater and a deterioration in corrosion resistance.

〔Effect of the invention〕

The marine propeller of the present invention has a mechanical tensile strength of 90 kgf/- or more and a corrosion fatigue strength of 29 kli) f/- or more in seawater for both the split blades and the welded parts, and
The propeller material must also have superior cavitation erosion resistance compared to conventional nickel-aluminum bronze propellers. In addition, the propeller material of the present invention has better mechanical properties and corrosion fatigue strength than conventional mono-alloy materials, so the marine propeller of the present invention manufactured and welded with this material has better mechanical properties and corrosion fatigue strength than conventional single-alloy materials. This makes it possible to manufacture lighter, more efficient propellers by reducing the thickness of the blades. Therefore, by using the marine propeller of the present invention, the propulsion efficiency of a marine vessel can be improved compared to the conventional one, and it can greatly contribute to the energy saving of the vessel, that is, the reduction of fuel costs.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining the structure of the marine propeller of the present invention and a part of its manufacturing process.

Claims (1)

[Claims] C: 0.08% or less, Si: 0.1 to 1.5% by weight
, Mn: 0.1-3%, Cr: 16-19%, Ni: 4
．． 5-7.5%, Mo: 0.5-2%, Al: 0.05
Propeller blades made separately at the boss part using a corrosion-resistant high-strength marine propeller material consisting of ~0.5% Fe and the remainder being substantially Fe are welded at the boss part with welding material having the same chemical composition as the propeller material. A corrosion-resistant, high-strength propeller that can be assembled.