JPS60121278A - Surface treatment of thick steel member - Google Patents

Abstract

PURPOSE:To form a surface layer having excellent resistance to corrosion and erosion by placing an amorphous alloy foil on the surface of the runner of a water turbine, a guide vane, etc., irradiating a laser beam, and then quenching. CONSTITUTION:The runner of a water turbine or a guide vane 1 is manufactured with ferritic or austenitic stainless steel. A film of an amorphous alloy 2 having 10-50mum thickness and contg. 8-11atom% Cr, 10-15atom% P, 5- 11atom% C, and the remaining part of Fe is formed on the surface. A laser beam 5 from a laser beam oscillator 3 is converted with an amplifier 4 into a beam 7 having 0.1-10cm width which is reflected by a prism 6 and irradiated on the whole surface of the amorphous metallic coil 2 all over at 30-300/sec velocity or by scanning with spotting. The amorphous alloy is deposited 8, and then quenched with cooling water to increase the resistance of the surface layer to corrosion and erosion.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field Recommended by the Invention] The present invention relates to a surface treatment method for heavy-duty steel members such as water wheel runners and guide vanes of hydraulic machines.

[Prior art and its problems]

Generally, water turbine launches and guide vanes are corroded by corrosive substances contained in river water or eroded by sand erosion. For this purpose, the surfaces of these parts must be corrosion and erosion resistant.

In particular, water turbine launches and guide vanes that are exposed to highly corrosive river water are generally made of ferritic stainless steel (for example, 130R steel) or austenitic stainless steel, which have excellent corrosion resistance. However, these 4J fees are I[
The lh rating is extremely high, and it is often difficult to select delivery conditions. Particularly in the case of rough shapes such as waterwheels, defects are unavoidable and repairs are required.
The company is forced to compensate for the numerous deficiencies.

In addition, the parts affected by heat due to this welding have to be heat treated because their corrosion resistance is reduced and large residual stress is generated.

For water turbine launches and guide vanes that are exposed to river water mixed with earth and sand, surface hardening must be applied to the areas that are most heavily hit by water to prevent sand erosion. In this case, the surface hardening treatment includes building up hard alloys by welding, or coating hard alloys or ceramics by gas or plasma spraying. However, in the former case, problems such as hardening of the weld heat-affected zone, weld cracking, and generation of residual stress occur, and work such as heat treatment and surface finishing is required to ensure reliability of material quality. It is difficult to do, takes a lot of man-hours and is expensive to wear. In the latter case, the adhesion between the water turbine launch and the coating layer may not always be sufficient, and the coating layer may peel off during operation of the water turbine, resulting in unexpected erosion. Furthermore, coating by bath welding and thermal spraying both create a harsh and inhospitable working environment, pose problems in terms of occupational hygiene, and both methods require skilled workers as they are mostly manual labor.

[Objective of the Invention] The object of the present invention is to eliminate the drawbacks of the above-mentioned conventional methods, and to improve the production of single-walled iron M parts such as water turbine launcher guide vanes under a favorable I/L industry environment. The object of this invention is to reliably form a surface layer with excellent corrosion resistance and erosion resistance without locally exerting an excessive thermal influence.

[According to the point of invention This is achieved by irradiating the bath with a laser beam and welding it to the thick steel part side.

[Practice of the Invention 1] Next, a detailed explanation 1 of the present invention will be provided based on the drawings (not shown) and embodiments.

■ [Figure (Here, 1 is a part of Jr. 4, such as a water wheel/suya kite vane, which is hereinafter referred to as a workpiece. A metal that easily becomes amorphous due to the metal; It is determined in consideration of economic efficiency and consistency with Work 1.

This gold@yam 2 is welded to the work lK by irradiating a laser beam based on the present invention. In the figure, 3 is a laser oscillator for this purpose, 4 is a widening device that gives a width to the laser beam 5 excavated from this laser oscillator 3, and 6 is a widening beam 7 from this widening device 4 to irradiate the workpiece 1. It is a refracting prism.

When the workpiece 1 is irradiated with the wide beam 7, the workpiece 1 or the refracting prism 6 is moved back and forth and left and right, so that the width beam 7 is spread over the entire surface of the metal beam 62.

When the metal foil 2 is irradiated with the laser beam in this way, the metal foil 2 and the workpiece 1 are instantly melted at the touch surface.
However, since the workpiece 1 is made of meat and has large hot spots, it is rapidly cooled and an amorphous surface layer 8 with good adhesion is formed. Since this amorphous surface layer 8 is not crystallized,
Since there are no grain boundaries or crystal orientation, and the crystals are completely uniform, the corrosion resistance is extremely high. Since amorphous alloys generally contain metalloid atoms with large atomic diameters that suppress the movement of atoms, they have extremely high hardness and excellent erosion resistance.

Gold + g? Ii 2 id especially Fe-(8-11 at%
) Cr-(10~]5 at%) P-(5~11 at%
) Amorphous alloys of composition C are preferred. It has excellent corrosion resistance and erosion resistance, has good compatibility with launch materials such as water wheel launches and guide vanes 7, and can be reliably welded to workpieces by laser beam irradiation. To explain this in more detail, the content i of Or
If it exceeds about 8 atoms, the corrosion resistance will decrease.
The corrosion rate in fL is less than 50 μm/year, and when it reaches about 9 atoms, the corrosion rate becomes so small that it cannot be measured. However, if the Or content plate is too small, corrosion resistance cannot be expected, and if it is too large, the cooling rate required to make it amorphous becomes too slow, and even if it is rapidly cooled with the large heat capacity of the workpiece 1, it will become amorphous. It becomes a pawn. P and C are metalloid elements and have the effect of promoting amorphization, but have little effect on corrosion resistance. If there is too much of these, it becomes too hard and cracks, and if there is too little, it becomes difficult to become amorphous. In addition, where P and C are more than the above range, bubbles may appear when melted with a laser, or bubbles may be observed after solidification. When line diffraction was performed, a slight crystalline peak was observed. Cr is 8 to 11 atoms.

An amorphous surface layer can be obtained by changing the amount of laser heat and the thickness of the metal foil within the range of P in the range of 10 to 15 atoms and C in the range of 5 to 11 atoms.

Note that the Or content plate is determined by which 8 degrees of cooling rate can be obtained after laser melting. Although this cooling rate cannot be measured in practice, the approximate cooling rate R (0C/
S) can be estimated.

R=2πλ(V)(θ−θ.)2 l and λ are thermal conductivity (Cal, μC・℃), e.g. is laser scanning speed (cm, /8), and q is heat input it < (!
al/4), θ is the surface temperature reached <°C>, θ. is the temperature of the workpiece (°C).

If the cooling rate is 5 x 10 °C/S or more, amorphization will be LT.
The thickness of the gold PA foil 2 is 15 to 50 μm.
If the width of the laser beam is selected to be in the range of 0.1 to 0.0 m, and the scanning speed is selected to be in the range of 30 to 300 on, /5, the cooling rate will exceed this value and amorphous state will be obtained. For example, the thickness of the metal foil is "lQttm", the width of the laser beam is 0.5
tyn and one scanning bed intersection is I U Ocm/6, the cooling degree is approximately 1.5 x 1.06°C 15, which is a rate at which amorphization is possible. In order to further increase the cooling rate, there is no choice but to reduce the heat input fiq or increase the scanning speed V, but it is also necessary to make the metal foil thinner or to reduce the width of the laser beam.

It is not preferable to make the metal foil thinner from the viewpoint of corrosion resistance and erosion resistance.

Actually Fe-9 atomic% Or -13 atomic% P-7 atomic%
Using a metal with a thickness of 20 μm and a composition of C, the width of the laser beam is 0.5, and the scanning speed is 1 (J Ocrn/'
When the method of this invention was applied to a carbon steel workpiece with a thickness of 30 mm under the condition of a laser energy of 1.51 W, an amorphous surface layer was obtained. The hardness of this amorphous surface layer is 800)
It is very hard with IV to 1400HV and can significantly improve erosion resistance. Incidentally, even cobalt-based alloy (stellite), which is considered to be the hardest of conventional weld overlay metals, has a hardness of 400 to 700 HV.

In addition to these metal foils, metals with the composition Fe-(more than 35 atoms, 10 atoms, or more) Or-20 atoms %PC/) can be considered, but even these metals have excellent corrosion resistance and mechanical resistance. It can be a highly promising amorphous alloy. However, the F
e-9 atomic % Or -1, 3 atomic % P-7 atomic % c also contains a large amount of Or, so the range in which it becomes amorphous is narrow.

Surface treatment fd1 based on the present invention, over the entire circumference of the workpiece'
It can be applied over the area or locally in areas most susceptible to corrosive erosion. If the erosion is so severe that a single thin layer of amorphous metal foil cannot provide sufficient service life, the surface treatment of the present invention can be repeated two to three times to achieve several layers of amorphous foil. A textured surface layer can also be formed.

It is still desirable to scan the laser beam over the entire surface of the metal foil, but if corrosion resistance is the main objective and the adhesion may be slightly weaker, then the scanning line shown in Figure 2 (1) may be used. It is sufficient to irradiate the laser pointwise as shown by trace 9. In this case, an amorphous metal foil must be used.

As mentioned above, the gold melted by laser beam irradiation is rapidly cooled by a large workpiece with a #l container, but cooling water can be blown out after laser beam irradiation to aid cooling. It is also possible to obtain a better quality amorphous surface layer.

Although the surface treatment of water turbine launches and guide vanes has been described above, the method of the present invention can also be applied to valves, shafts, and general structures that require corrosion resistance and wear resistance. Note that it is also possible to use an electron beam instead of a laser beam, but in this case it must be carried out in a vacuum and is subject to limitations on the shape of the structure.

〔Effect of the invention〕

(1) A surface layer with excellent corrosion resistance and erosion resistance can be formed on the surface of thick-walled iron parts.
For example, for water turbine runners and guide vanes that are exposed to highly corrosive river water or river water mixed with sediment, carbon steel, low alloy steel, and stainless steel, which are inexpensive and do not require severe casting conditions, can be used.

(2) Less heat input from laser beam irradiation;
There is no risk of hardening of the workpiece or residual stress. For this reason, the surface treatment according to the invention can be carried out after machining the workpiece, without the need for reprocessing or reworking.

(3) 41 required to irradiate the laser beam! The machine has no vibration or noise, and in some cases, metal foil is pasted in advance using a two-ring adhesive, so work can be done at each station, and metal powder is not scattered around, creating a good working environment. Can be surface treated. It also requires no skill and can be automated in some cases.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of the equipment for carrying out the surface treatment power gamma stone based on the present invention, and Fig. 2 is an explanatory diagram showing the scanning method of irradiating the metal foil with a laser beam in a dotted manner. . 11 Nork (waterwheel launch and guide vane), 2... Metal foil, 3 Ray-ray oscillator, 4 Width camera, 5... Laser beam, 6 Bend 11-teprism, 7... Width beam,
8...Amorphous It surface layer. Figure 1 [

Claims (1)

[Claims] 1) A metal 26 that easily becomes amorphous or an amorphous metal 1i is added to the surface of the thick steel part 1 to be surface-treated! i? ]l-
By irradiating this metal with a laser beam and then rapidly cooling it, the surface treatment of the J-Ning Nikutetsu 11111 steel is characterized by making the metal coat thick and thick. Method. 2. In the method according to claim 1, the metal is Fθ-(8 to J1 atomic %) Cr-(10 to J5
Table 1hj treatment method for thick-walled steel members, characterized in that fσ is an alloy having a composition of (at.%) P-(5 to 11 at.%)C. 3) In the method of 61 cases in the first or second range of requirements, the thickness of the metal cutter is 15 to 50 μm, and the width of the laser beam is 0.5 μm. A surface treatment method for thick-walled steel members whose running speed is 30 to 300 on/sea. 4) A method for surface treatment of a thick-walled steel member according to any one of claims 1fA to a3, characterized in that the entire surface is scanned and irradiated with a laser beam. 5) A method for surface treatment of a thick steel member according to any one of claims 1 to 3, characterized in that the entire surface is irradiated with a laser beam in a dot-scanned manner. 6) Any one of claims 1 to 5
In the method described above, a method for surface treatment of a thick-walled steel member includes quenching using the heat capacity of the thick-walled steel member itself. 7) A method for surface treatment of the Atsunai steel part side, in the method according to any one of claims 1 to 5, characterized in that cooling water is sprayed after irradiation with a laser beam.