JPS5837162A - Pump and its manufacture - Google Patents

Abstract

PURPOSE:To enhance the cavitation erosion resistance of a pump by coating the surface layer of a part of the pump liable to cause cavitation erosion with a Cr-Ni stainless steel contg. a specified amount of Mn by build-up welding. CONSTITUTION:The surface of a part of a pump causing cavitation erosion wear is coated with a Cr-Ni stainless steel consisting of <0.2% C, <2.0% Si, 10-20% Cr, 0.5-10% Ni, 2-20% Mn, <2% Mo and the balance Fe or further contg. at least one of 0.02-0.3% N, 0.01-0.1% Nb and 0.5-5% Co by build- up welding. The build-up welded layer contains no soft ferrite phase, is composed of an epsilon phase and an austenite phase, and has superior cavitation erosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pump with excellent cavitation, heat and erosion resistance, and a method for manufacturing the same.

Pumps are widely used for agricultural purposes such as irrigation and drainage, for civil engineering work, and for urban water and sewage systems, but they are also used for circulating water in steam turbine condensate equipment, recirculation equipment in paper and chemical factories, and in other applications. It is used for pumping seawater.

In general, when an axial flow pump is operated with a suction head higher than a certain level, cavitation occurs (normally, the back surface near the impeller inlet becomes a strangely low pressure, and the impact pressure generated when the cavity collapses in this part of the pump) Cavity erosion occurs, which impairs efficiency and causes spongy erosion of the blade back surface and the inner surface of the fuselage. In addition, in a spiral pump, when the static pressure in the spiral pump flow path drops to around the steam saturation pressure corresponding to the temperature of the pumped liquid, cavitation occurs, causing a sudden drop in head, power, efficiency, etc. The collapse causes cavitation erosion.

Cavitation erosion also occurs in oil pumps. In other words, oil has a high viscosity and is difficult to flow, resulting in a large pressure drop in the pump suction pipe9. Therefore, cavitation damage is likely to occur at the pump inlet. In oil pumps, cavitation erosion occurs in the widening gap immediately after passing the high-pressure part due to meshing of gears.

Conventionally, the materials used for pumps have been cast iron, cast steel, various heat-resistant alloys, austenitic stainless steel, chromium-molybdenum steel, high chromium steel, steel alloys, etc., although they differ depending on the purpose. As efficiency increases, it has become difficult to avoid cavitation/erosion with conventional materials.In addition, even materials with excellent cavitation/erosion resistance are not as easy to process and cost as Stellite. There are problems with this, and it may not be possible to use it as a material for pumps.
There is a growing demand for products that have / characteristics.

The present invention was made in view of such a need, and an object of the present invention is to provide a tapump with excellent cavitation and corrosion resistance, and a method for manufacturing the same.

The present invention contains a predetermined amount of manganese in the nickel-based stainless steel of the pump as the surface layer of at least the cavities worn out by erosion, and the epsilon phase or austenite phase is formed without forming a ferrite phase in the structure. Formed, cavitation resistant,
It has improved eroticism.

i.e. 10 to 209 chromium in weight percent, 0.5
It consists mainly of nickel of ~104J, manganese of more than 2 and less than 20, carbon of less than 0.21G, silicon of less than 21, molybdenum of less than 211, and the balance is iron, and contains no ferrite phase. This is a pump in which steel containing a phase or austenite phase is provided as at least 88 layers of the cavitation/erosion wear area, and the plated steel further contains an epsilon phase or an austenite phase without containing an epsilon phase or an austenite phase. The present invention is a pump in which steel is provided as a surface layer at least in cavitation/erosion wear areas, and in a pump in which the surface layer is a welding layer for overlay welding.

In addition, at least the cavitation/erosion wear area of the pump is overlaid by welding to reduce the weight by 0.2% by weight.
- less than carbon, less than 2 silicon, 10 to 201 chromium, 0.5 to 10 nickel, more than 2% w% manganese, less than 2% molybdenum/.

This is a method for manufacturing a pump in which a surface layer is formed with the remainder being iron, and the surface layer is 0.2-0.2% by weight by overlay welding.
Carbon below, silicon below 21, chromium between 10 and 20, nickel between 0.5 and 10, manganese above sl and below 2, molybdenum below 2, the balance being substantially iron or zero. .02-0.3% nitrogen.

This is a method for manufacturing a pump in which a surface layer is formed that includes one or more of niobium with a concentration of 0.0, 0.0, 0.02N, and cobalt of 0.5 to 5.0. In this case, if a ferrite phase coexists in the surface layer according to the present invention, cavitation resistance and erosion resistance will be significantly deteriorated, so it is essential that the 1 m deposited layer does not substantially contain a ferrite phase. In addition, carbon forms an austenite phase in the epsilon phase together with manganese and nickel, thereby improving the carbon retention and erosion resistance.

That is, when the carbon content of martensitic stainless steel within the composition range of the present invention is increased, epsilon phase and austenite phase are formed in the base structure, which improves cavitation resistance and corrosion resistance.
Erosion resistance is significantly improved.Furthermore, when niobium or cobalt is added, cavitation resistance and erosion resistance are further improved.

By the way, sensuous welding material Kl! One of the characteristics required is
One example is the small residual strain caused by heat shrinkage after welding. If the thermal expansion coefficients of the base material and weld layer are different, stress will be generated at the interface between the base material and the weld layer during thermal contraction after welding, resulting in residual strain and causing cracking and deformation. This tendency is remarkable when martensitic stainless steel is used as the base material, and large strains occur during martensitic transformation. One method for alleviating this strain is to reduce the yield strength of the weld layer and to alleviate the stress generated by layerwise deformation of the weld layer. According to this method, the lower the yield strength of the bath deposit layer, the more effective it is in alleviating strain, and therefore the prevention of cracking and deformation after welding. This allows stress to be relaxed.

The steel according to the present invention forms an epsilon phase and an austenite phase in the structure to improve cavitation resistance and erosion resistance, and at the same time has a yield strength of usually 20 kg/- or less, which is 8U8304, which is an austenitic stainless steel.
etc.) and is excellent in preventing cracking and deformation, making it particularly suitable for use as a molten layer in sensual welding.

As described above, the pump of the present invention has excellent cavitation resistance/erosion resistance, and has little cracking or deformation due to sensual welding, making it extremely excellent as a pump used, for example, under high head and high efficiency conditions. It has characteristics.

In the pump of the present invention, mosquito steel is provided at least in the worn part of the cavity plate due to erosion, and the overlay welding part is, for example, the vane (2) in the pump as shown in FIG.
) and the inner surface of the fuselage (1). In addition, the welding of the cough steel to the pump is covered arc welding, TIG
This can be easily carried out by ordinary #l welding methods such as @ welding and MIG welding.The reasons for limiting the composition of the overlay welding material used in the pump button of the present invention will be described below.

Carbon (C): Carbon forms an epsilon phase and an austenite phase and has the effect of improving cavitation and erosion resistance, but since excessive addition impairs toughness, the upper limit is set at 0.2-. .

Silicon (silicon): Silicon improves the flowability during steel melting,
It also has the effect of improving weldability, but excessive addition of silicon impairs toughness, so the upper limit is set at 2%, but it is more preferably set at 0.2 to 1.0% for practical purposes.

Chromium (Cr); Chromium improves corrosion resistance, so K
Although it is necessary to add IO- or more, excessive addition will generate a 7-elite phase in the welded layer and reduce the resistance to capitation and erosion, so the upper limit is set at 20III. It is desirable to set it to 11-15%.

Nickel (Ni): Nickel is added with O, S to improve cavitation resistance, erosion resistance, and toughness.
*Although it is necessary to add more than 1,000,000 yen, the effect is not great even if added in large amounts, and the cost will increase, so the upper limit is set at 101, but it is more desirable for practical use to be between 2 and 811i.〇Manganese (Mn) ); Manganese is a particularly superimposed element in order to form an austenite phase in the epsilon phase and improve cavitation attack and erosion resistance, but 2I
If the amount is less than 2, the effect will not be sufficient and it will be necessary to add more than 2. However, since excessive addition impairs the flowability of the metal, the upper limit is set at 20-20, but in practical terms it is 4-15.
It is desirable to set it as %.

Molybdenum (Mo): Molybdenum has the effect of improving cavitation resistance, erosion resistance, and corrosion resistance.
Since excessive addition impairs toughness, the upper limit is set at 2%, but from a practical point of view it is desirable to set it at 0.5 to 1.5%.

Nitrogen <N>: Nitrogen is a necessary element to improve capitation, erosion and corrosion resistance, but if it is less than 0.021, the effect will not be sufficient, and excessive addition will cause pinholes, The upper limit is set at 0.3% because it causes blowholes, but in practical terms it is 0.02%.
It is desirable to set it to ~0.2-.

Niobium (Nb): Niobium makes the crystal grains of the welding layer finer and improves cavitation and erosion resistance, so it is necessary to add 0.01 or more in the rounding process, but excessive addition will cause the welding layer to contain niobium. Cavity-resistant seal by generating ferrite phase/
・The upper limit is set to 0.1 because it reduces eroticism.
1, but in practical terms it is preferably 0.01 to 0.05-.

Subaru) (Co) ; In order to improve cavitation resistance and gastric erosion resistance, it is necessary to add cobalt in an amount of 0.5 or more. Even if added in a large amount, the effect will not be large and the cost will increase, so the upper limit is set to 5. Although it is excellent.

Further, in practical terms, it is desirable to set it to 0.5 to 3-.

Structure: The cavitation resistance and corrosion resistance of the steel having the composition described in the claims is more effective when the structure contains an epsilon phase or an austenite phase. is essentially epsilon,
phase or austenite phase.

In this case, if a ferrite phase is mixed in the structure, the cavitation resistance and corrosion resistance will be significantly deteriorated, so it is necessary that the structure does not contain a ferrite phase.

Hereinafter, a pump according to the present invention will be explained in detail using an example.

Samples of chemical groups shown in Table 111 were melted using a high frequency melting furnace. Comparative Example 1 is commercially available 808304, which corresponds to 18-8 stainless steel. Comparative Example 23 is a 13 thichrome steel whose composition is equivalent to that used in water turbine launches, etc., and its thermal history is 650"Q after solution treatment at 1050°C for 2 hours.

It was tempered for 2 hours.

In addition, the samples of Examples 1 to 11 and Comparative Example 1 were drawn until the diameter became 2" mm, and
The surface of a pump vane model cast from Kokurofu steel (corresponding to Comparative Example 2) was welded by TIG@contact. The characteristics of each sample thus obtained were investigated and the results are shown in Table 2.

The cavity erosion test was conducted using the electrostrictive vibration method at a frequency of 6.5 KHz, an amplitude of 100 μtn,
The process was carried out in pure water at 25°C for 120 minutes, and the number of cavitation expansion and erosion expansion 1fj (C, E, I) was determined by the following formula.
t” seeking meta.

Below are C and E-1 after margin zone heat treatment. As is clear from the above results, C and E of Example 1-11
・■・ is smaller than 5U8304 (relative example 1), which is conventionally considered to have excellent cavitation resistance and erosion resistance, and the pump according to the present invention has excellent cavitation resistance and erosion resistance. have.

Furthermore, even when welded to 13% chromium steel (corresponding to Comparative Example 2) which undergoes martensitic transformation, no weld cracking occurs, indicating that the material has resistance to weld cracking.

As explained above, since the pump according to the present invention has excellent cavitation and erosion resistance, it can be said to be extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a gear pump. 1...Inner surface of the casing (body), 2...Blade, 3...Rotating shaft. Agent Patent Attorney Noriyuki Chika (1 other person)

Claims (1)

[Claims] (1) Jlt where the surface layer of at least the cavity/erosion wear area is 0.2 inches or less in weight percent.
li, 2 or less silicon, 10 to 10% chromium, 0.
The steel must consist of 5 to 10% nickel, more than 2%, manganese less than t20Is, molybdenum less than 2%, the balance being iron, and contains epsilon phase or austenite phase without substantially containing ferrite phase. A pump featuring: <21? At least the surface layer of Cavity M7/Erosion damaged area has carbon of 0.216 or less, silicon of 2 or less, 10~Mountain ridge, 0.5~
nickel of lO-, manganese of more than 2 and less than 2091, molybdenum of less than 2%, and nitrogen of 0.02 to 0.3, niobium of 0.01 to o, is, covert of 0.5 to 5%. 1. A pump characterized in that the remainder of the encapsulation is made of iron, and the pump is made of steel that does not substantially contain a ferrite phase but contains an epsilon phase or an austenite phase. (3) At least the cavities and erosion of the pump should be sensually welded to the damaged area of the pump, and the weight bar should be 0.2 in.
carbon less than fi, silicon less than 2, chromium from lO to 'JJ, nickel rumored to be 0.5 to 10, manganese more than 2- and less than ka, molypde less than 29g, where the "am" part is substantially iron. A method for manufacturing a pump characterized by forming a surface layer consisting of:
carbon less than or equal to 2, silicon less than or equal to 10, nickel less than 0.5 to 10, more than 256t20
Manganese below 1, molybdenum below 2, and 0.
02-0.316 nitrogen, 0.01-0.1 arrogance17)
= #fu. A method for manufacturing a pump, characterized in that it contains one or more types of cobalt of 0.5 to 5-5, and the remainder substantially consists of iron.