CN102168221A - Process for casting high-nickel austenitic nodular cast iron valve-stem nut - Google Patents

Abstract

The invention provides a new and advanced cast process, which is characterized by comprising the following eight steps of: 1, molding, and manufacturing a core; 2, smelting; 3, spheroidizing; 4, inoculating; 5, detecting before melting; 6, pouring; 7, detecting after the melting; and 8, cleaning and performing rough machining. The process has the advantages that: the balling rate of a high-nickel austenitic nodular cast iron valve-stem nut cast by the eight steps is high; and the high-nickel austenitic nodular cast iron valve-stem nut is suitable to be used as valve accessories of sea water pumps, heat discharging pipelines, exhaust pipelines and the like under the severe condition completely, and has the excellent performance of heat resistance and corrosion resistance.

Description

The casting technique of high-nickel austenite nodular cast iron valve-stem nut

Technical field

The invention belongs to valve and make the field, relating in particular to a kind of high-nickel austenite nodular cast iron is raw-material valve stem nut casting technique.

Background technology

Valve stem nut is used for valve opening and cuts out, it is the critical valves part that plays compound action with component such as valve rods, the valve stem nut that uses plain cast iron, ferrous materials to make, because of this defective on performance such as against corrosion, anti-oxidant, heat-resisting of its material, the rust that valve rod and nut take place easily is dead, thereby valve can't normally be used, until scrapping.High-nickel austenite nodular cast iron, it is heat-resisting, corrosion resistance nature is good, suit under abominable Working environment, to use, this material nickel content height, wherein the D2 type trade mark is nickeliferous up to 18-22%.Matrix all is an austenite.Because carbon content height, its globular graphite is distributed in matrix after spheroidizing, again because graphite is spherical, promptly improved the mechanical property of cast iron, can play lubricated cushioning effect again, therefore, in casting high-nickel austenite nodular cast iron valve-stem nut process, how guaranteeing higher nodularization rate, is the key point of this casting technique.

Summary of the invention

In sum, the invention provides a kind of brand-new, advanced casting technique, its feature is divided into following eight steps in factory:

1, moulding, coremaking;

2, melting;

3, spheroidizing;

4, inoculation;

5, the stokehold is detected;

6, cast;

7, detect behind the stove;

8, cleaning and roughing.

Usefulness of the present invention is, high-nickel austenite nodular cast iron valve-stem nut according to above-mentioned eight steps casting, have higher nodularization rate, be applicable to as the valve fittings under the bad working environments such as sea-water pump, heat extraction, gas exhaust duct and use to possess good heat-resisting, corrosion resistance nature fully.

Embodiment

Below, according to the foregoing invention content, specifically carefully state this working of an invention mode.

1, molding and core making:

Mix the system clay with the casting of 20-70 purpose with roughing sand and be used to make external form, be coated with behind the graphite paint, the drying room about 400 ℃ is dried, and core adopts tung oil sand to make oven dry.

2, melting:

With the magnesium iron pig iron is major ingredient, wherein: carbon 〉=4.0, silicon≤1.0, phosphorus≤0.05, sulphur≤0.03, manganese≤0.3, alloy material adopts sheet nickel, contain manganese 80% mid-carbon fe-mn, contain content shown in the high carbon ferro-chrome according to the form below of chromium more than 60% and add the melting smelting temperature, tapping temperature 〉=1470 ℃ to 1480-1500 ℃.

3, spheroidizing

Nodulizing agent is selected RE-Mg-ferrosilicon alloy for use, and add-on is 1.2-2.0, adopts pit to pour method.

4. inoculation

Select the nucleating agent that contains strontium for use, add-on is 0.8-1.0%, makes late inoculation respectively and handle in the nodularization process and after the nodularization.

5, the stokehold is detected

1. adopt thermal analyzer to detect carbon, the silicone content of solution, and tentatively judge its nodularization rate.

2. adopt the chill block assay method to judge its nodularization effect.

3. get metallographic specimen and make, and determine its nodularization rate in order to carrying out metallographic behind the stove.

6, cast

After nodularization, inoculation finish, to skim at once, teeming temperature is controlled at 1400-1440 ℃, and pours into a mould in 10 minutes and finish.

7, detect behind the stove

Carry out chemical analysis behind the stove and detect, guarantee that various alloying elements are all within the scope of defined.

To the metallographic specimen polishing, under full phase microscope, observe, judge its nodularization rate, should guarantee more than II level nodularization rate.

8, cleaning and roughing

The high-nickel austenite nodular cast iron valve-stem nut foundry goods of casting successful is carried out roughing, find that in time outward appearance casting flaws such as knockout, big slag, core shift, shrinkage cavity are to guarantee that product is qualified.

Its nodularization rate of valve stem nut with above-mentioned cast is good.

Claims (7)

1. a high-nickel austenite nodular cast iron valve-stem nut casting technique is characterized in that, is divided into following eight steps:

1, moulding, coremaking, 2, melting, 3, spheroidizing, 4, inoculation, 5, the stokehold detects, 6, cast, 7, detect behind the stove, 8, cleaning and roughing.

2. according to the described a kind of high-nickel austenite nodular cast iron valve-stem nut casting technique of claim 1, it is characterized in that, described molding and core making, be to mix the system clay with the casting of 20 1 70 purposes with roughing sand to be used to make external form, be coated with behind the graphite paint, drying room about 400 ℃ is dried, and core adopts tung oil sand to make oven dry.

3. according to the described a kind of high-nickel austenite nodular cast iron valve-stem nut casting technique of claim 1, it is characterized in that, described melting: be to be major ingredient, wherein: carbon 〉=4.0, silicon≤1.0 with the magnesium iron pig iron, phosphorus≤0.05, sulphur≤0.03, manganese≤0.3, alloy material adopts sheet nickel, contain manganese 80% mid-carbon fe-mn, contain content shown in the high carbon ferro-chrome according to the form below of chromium more than 60% and add the melting smelting temperature, tapping temperature 〉=1470 ℃ to 1480-1500 ℃.

.

4. according to the described a kind of high-nickel austenite nodular cast iron valve-stem nut casting technique of claim 1, it is characterized in that described spheroidizing is that nodulizing agent is selected RE-Mg-ferrosilicon alloy for use, add-on is 1.2-2.0, adopts pit to pour method.

5. according to the described a kind of high-nickel austenite nodular cast iron valve-stem nut casting technique of claim 1, it is characterized in that described inoculation is to select the nucleating agent that contains strontium for use, add-on is 0.8-1.0%, makes late inoculation respectively and handle in the nodularization process and after the nodularization.

6. according to the described a kind of high-nickel austenite nodular cast iron valve-stem nut casting technique of claim 1, it is characterized in that described stokehold is detected:

1. adopt thermal analyzer to detect carbon, the silicone content of solution, and tentatively judge its nodularization rate.

2. adopt the chill block assay method to judge its nodularization effect.

3. get metallographic specimen and make, and determine its nodularization rate in order to carrying out metallographic behind the stove.

7. according to the described a kind of high-nickel austenite nodular cast iron valve-stem nut casting technique of claim 1, it is characterized in that described cast, be after nodularization, inoculation finish, skim, teeming temperature is controlled at 1400-1440 ℃ at once, and pours into a mould in 10 minutes and finish.