Free Opening of Ladle Gates

IMF 3/21/07

Paul Woods – Vesuvius

Reasons for Importance of Free

Opening of Ladles

• Steel Quality

• Refractories destroyed by lancing

• Safety • Safety

• Delays resulting from non- free opening.

Note on a caster this can cause a

turnaround.

Sand Types

• Chrome Silica

– Normally a high free open rate

– Causes high wear of well refractories

– Low price compared to zircon– Low price compared to zircon

• Chrome Silica Zircon

– Good for free opening

– Reduces wear to well refractories compared to Chrome Silica sand

– Price mid range between chrome silica and zircon.

• Zircon

– Some shops see less boiling in molds

– Can build up in well

Sand Types Cont.

• Carbon Additions

– Usually 0.5 - 2%

– Assists on flow of sand – lubrication– Assists on flow of sand – lubrication

Amount of Sand in Well

• Normally sand should be mounded by 3-4

inches above the ladle bottom.

• Too little sand can cause metal to stay • Too little sand can cause metal to stay

frozen in well area resulting in non free

open.

• More sand may be required as well and well

nozzle wear.

A

WELL BLOCK AREA

C

B A. Sintered layer of nozzleB. Granular nozzle sandC. Well blockD. NozzleE. Upper slide-gate PLAF

Figure 1

Configuration of nozzle sand in sliding-gate system before teeming.

D

E

E. Upper slide-gate PLAFF. Lower slide-gate PLAFG. Collector nozzle

Installation of Sand

• Methods of sanding ladles:

– Bucket dumping

– Throw in whole bag– Throw in whole bag

– Manual Funnel

– Funnel on Jib Crane

– Auto bucket lowered on Jib

– Auto Dumping into ladle

Sander from bottom

Sander on jib

• Many different methods are used for distributing the sand into the well.

– Dump in buckets

– Throw in whole bags

– Manual Funnel

– Crane held funnels

– Crane held auto discharge in ladle bottom

– Auto top dump into ladle

Automatic Ladle Well Sanders

• Pre – measure sand with dial in weight.

• Air operated valve opens and closes when

the desired amount of sand has been the desired amount of sand has been

delivered.

• Cameras to see and to record the well

condition and amount of sand.

• Reduces chance for operator error.

Preheating of Sand

• Keeps moisture out of sand to prevent

caking of sand.

• Normally preheat to 150 – 200 F is • Normally preheat to 150 – 200 F is

sufficient.

• Some sand dried and does not need

preheated if well packed in bags.

• Zircon sand should be preheated

Well Bore Geometry

• Many different well bores. The theory is

that the sand should drain and allow any

crust to loose support and collapse.crust to loose support and collapse.

– Wide bore well block taper to nozzle bore

– Wide bore well block and nozzle tapered

– Straight bore well block and nozzle

Over Sizing of Slidegate Plates

• Some customers over size slidegate plate

bores to help on free opening.

• Downside is additional throttling decreases • Downside is additional throttling decreases

slidegate plate life.

• In general shops with larger bore are easier

to free open.

Fast Movement of Slidegate

Opening

• In most circumstances would recommend a

two speed hydraulic and pendant.

– Normally 2- 3 seconds full stroke time for fast – Normally 2- 3 seconds full stroke time for fast

speed to allow fast opening and jogging of gate

if the sand does not fall.

– 6-9 seconds full stroke time for slow speed to

allow for better control which helps in control

of rate of rise.

Shop Practices that Influence

Free Opening Rates

• Free Opening Rates Very Widely 50% -99+%

• Much has to do with Shop Practices• Much has to do with Shop Practices

• Long ladle hold Times – Can have a wide range and over 1.5 hours can be significant drops in free opening

• Tapping stream hitting or very close to Slidegate well.

Shop Practices that Influence

Free Opening Rates Cont.

• Ladle Last Stir to Open Times – Greater than 20 minutes start to see an effect.

– One customer reduced from average 25 minutes to ten minutes for a test and saw a 15% increase to ten minutes for a test and saw a 15% increase in free opening.

Ladle Preheat temperatures –Poor preheat can cause skull which will prevent free opening, New ladle temperatures are critical.

Shop Practices that Influence

Free Opening Rates Cont.• Cleaning of Ladle Bore

• Cleaning slag line to prevent debris from falling into well bore.into well bore.

• Sand just before tap.

• Cameras in ladle makeup and sanding areas can help solve when there is a problem with free opening. Also Cameras make some workers make more of an effort in doing their jobs.

Summary

• Every Shop is different and preferences on sand type and practices vary widely from shop to shop.

• Trial and Error seems to be most common method for what works best with regards to free opening for what works best with regards to free opening in each shop.

• Attention to detail in practices (cleaning bore, cleaning ladle, sand in well, ladle preheat, ladle position during tap, dry sand, ladle hold time, off stir to open time, etc.) results in highest free open rates in any shop.

Summary Cont.

• Some shops are making grades and have

layouts that make high free open rates

extremely difficult to achieve.extremely difficult to achieve.

– Tap stream near slidegate

– Extremely long ladle hold times

– Long off stir to open times