Studying phenomenon in a factory - a simple approach

7/31/2019 Studying phenomenon in a factory - a simple approach

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My study sheet

Hypothesis :

The temperature for Hi Cr 15% may have been kept higher because 8 Nos molds were poured

The castings quality may be different from 1st

to 8th

casting, with possible more defects in the First

casting and not so many in the 8th

casting

Data:

Heat no B5311/311 Dtd : 14-02-2012 Time : 14:45 Hrs

Tap temperature 1421 deg C Tap LM : 1475 Kg Poured : 1275 Kg

Charge : Foundry returns 100 Kg Carbon steel Mix scrap : 1000 Other additions

Lip pouring

Knocked out after 24 Hrs 15-02-2012 at 17:00 Hrs

1st

Mold 8th

Mold


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Observations :

The fluidity of the metals is still good even after 8 moulds pouring ( fins is an indication of that ( Not

to mention the improvement required to reduce the fins in the match plate MS plates that are

screwed to the Pattern mounting plate

Since Knocking is in warm condition ( Hand touch) 45-50 deg c, the sand is still sticking on to the

casting

There is a slight dip in the castings of 8th

Mold near the Gating area, so the liquid metal solidificationin the fin area has preceded that of the gating area.


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Riser area not cleanly knocked off

Metal flow indicated by risers, Temperature is

high

Sand fusion with metal

Characteristics : Blow holes on top of casting ( Look like Hemispheres )

Tap temperature 1488-1489 deg C

QA proposed as follows: after which the casting was OK, but still the problem of sand fusion

continued

Earlier (13-02-12) Later (01-03-12)

Mn Scrap + FR Y Y

HC Fe Cr Y Y

Ca Si - 2 kg ( in 1480 Kg of Metal)Al - 1 Kg

Fe Ti - 2 Kg

Graphite Iron - 5 Kg

After change in deoxidation practise

However Sand fusion still continues

Nitrogen level in WCB Castings due to addition of foundry returns


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Heat No Bath Nitrogen

during sample

Addition of

Foundry

returns ( Kg)

Batch nitrogen

after FR

addition

Nitrogen level

of FR

Remarks

C 4108 0.0082%

(82 ppm)

~200 0.0096%

(96 ppm)

0.0187%

(187 ppm)

Bath 1500 kg

assumed

C 4109 0.0082% ~200 0.0096% 0.0187% Bath 1500 kgassumed

A 6042 0.0082% ~200 0.0087%

(87 ppm)

0.0132%

(132 ppm)

Bath 2000 kg

assumed

A 6043 0.0119 % ~200 0.0120%

(120 ppm)

0.0129%

(129 ppm)

Bath 2000 kg

assumed

Data by MP Yadav (8-3-12)

The difference between the C & A furnace seems to also stem for the time taken to melt a heat

load, even though the melt is low the time is higher

Found out using the nitrogen mass balance

e.g C Fce Melt 1500 Kg; Sample at 1300 Kg , Nitrogen in 1300 Kg + 200 kg X x% = 1500 Kg X final

nitrogen %

Ref paper : Effect of Nirogen in steels ( Key to metals)

Crust formation in High Chrome Steels ( 24-03-2012)

A thin crust forms on the casting of High Chrome. Comes off quite easily. It is about 0.5 mm thick

and has a sometimes clean or a blotted finish. The blotted finish possibly because of coating


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Reverse sids notice the small pockmarks,

possibly showing the variation in coating

thickness and permeability of mold

The thickness of crust is about 0.5 mm or about

500 microns and is very brittle nature

Cracks in Ni Hard 4 castings

Material Ni Hard 4 Item Gulf Cobla Ball Joint

Liner

SAP Material Number S084 C02587 Application Dredge Yard

First Lot See Below Additional Operations Machining of Face/

Top & Bottom steps

Symptom Castings in March 17/3

20/3 4 castings

cracksSpecs A 532M Cl 1; Ni Hard 4

(Type D)

Abrasion Resistant

Cast Irons


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Process check sheet

Chemistry C (2.6-3.2); Si (1.8-2.0); Mn (0.4-0.6); S (0.1 max); P (0.0-0.06 max); Ni (4.5-

6.5); Cr (8.0-9.0); Mo (0.0-0.4)* ( in special cases); Material specs of Liner

varies based on the impact it is subjected to

Melting IF B was used for all the lots

Temperature prior to pouring varied from 1420 to 145 deg C for all

campaigns

11-2

(1400 Kg)

(1450 deg C/ B 299

20-2

(400 Kg)

(1435

deg, B/12)

15-3

(1300 Kg)

(1420

deg)

B/82

18-3

(1100 Kg)

(1432)

B/87

Heat Treatment 550-600 BHN ( 53-54 Rc); Heat to 800 deg C and furnace cool

`

Welding possibility exists which need to be done with the same electrode as that of the parent

metal. Preheat at 350 deg. It is quite hard and has to be handled carefully.

Liner withstands the impact from the sand which is being dredged, hence made to withstand

abrasion wear


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9/12

Red pen showing the location of longitudinal

crack

Cracks are almost opposite to Risers on the far

end

May be the core was very hot ( Largest portion). Cooled the last and poor collapsibility so cracked .

Fluidity may not be an issue as there are fins. In fact the temperature may be more than the desired.

More info on dredgers (http://www.dredgers.nl/)

Hypothesis : New sand has a better finish as compared to blended sand in the facing area ( 40:60)

The part studied was Zwick disk which was moulded in New / Blended sand. A comparison of theproperties is shown.
http://www.dredgers.nl/http://www.dredgers.nl/http://www.dredgers.nl/http://www.dredgers.nl/


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Seeing this it appears that there may not be a significant difference in the casting quality between

new and blended sand usage. In future we can take surface roughness a measure also. The black

color will go away in the Heat treatment

New Blended

Blackishness is higherFinning is same as New sand

Fusion of sand is almost the same


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Does ISO-Propyl alcohol have a significant effect on mold surface quality?

Iso-propyl alcohol is used as a carrier for the mold coatings. If purity is better(?) the burn out will be

faster and longer leading to proper drying and possibly superior quality

Hypothesis :Use of recycled sand to produce Mn Steel castings doesnt give a significant difference

in casting surface quality

With Recycled sand With New sand


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End of document

Started 15th

Feb 2012

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Studying phenomenon in a factory - a simple approach