Study on post-solidification

intensive riser cooling for

heavy steel castings

Jinwu KANG, Xiaokun Hao, Gang Nie, Haimin Long,

Tianjiao Wang, Baicheng Liu and Chengchun Zhang

School of Materials Science and Engineering

Tsinghua University, Beijing,

Harbin Electric Machinery Co., LTD，Harbin, China

2017-03-16

1. Introduction

2. Intensive riser cooling of a casting

after solidification

3. Application into a turbine blade

4. Results and analysis

5. Conclusions

Outline

1. Introduction Risers are used for feeding during solidification to

get rid of shrinkage in castings.

Shrinkage in a castingCasting with risers

Riser is the biggest hot spot, its

cooling is the slowest

Risers take long time to cool down

Risers cools too slow after solidification, they result

into nonuniform temperature distribution, then result

into stress and deformation.

riser

Casting bottomTem

pera

ture

Time

Shakeout temp.

For heavy castings, methods to quicken up cooling:

mould loosing, water spraying on mould, air/water

pipes in mould.

Ablation of the mold during casting

process [J. Grassi, et al., 2009]Cooling pipes in mold [Zhang

jixun,1980]

2. Intensive riser cooling of a

casting after solidification

Spray of water

fog or forced airHeat

extracting

Nozzles

Riser

T2

Casting

Q

T1

T3

Riser

T2

Casting

Q

T1

T3

T1> T2>T3 T1< T2<T3

functions of riser during solidification (a) and afterwards with PSIRC (b) for a

turbine blade casting

3. Application into a turbine blade

B2

B1

Electromagnetic valve

Nozzles

Control board

Riser

Sand mold

Temperature

Temperature

Air/ spray

source

ZG0Cr13Ni4Mo， martensitic stainless steel

1460mm×1210mm×850mm

0.9t. C Si Mn P S Ni Cr Mo Cu

0.03 0.46 0.52

-

0.55

0.01

1

0.01

2-

0.02

5

4.25 13.5

-

13.6

0.60

-

0.65

0.08

-

0.09

(a) thermocouples embedded during molding (b) pouring

(b) Onsite experiment of the turbine blade

Sand mold

risernotzzle

(a) Riser top (b) Infrared image of the riser top

Forced cooling of riser of the hydro turbine blade

4. Results and analysis

Comparison of the cooling curves of B1 with and

without PSIRC

DT= TB1 - T B2 vs time

Start of PSIRC

B1

B2 TB1

TB2

DT= TB1 - T B2

Cooling curves of the points in the sand mold

-2

0

2

4

6

8

0 10 20 30 40

Tem

pe

ratu

re d

iffe

ren

ce /

oC

Time /h

No PSIRC

PSIRC

A

A 95

A-A

Temperature difference between the center and surface

(a) 0.25h (b) 17.8h before the adding of PSIRC

Heat flow during the casting process

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

10 15 20 25 30 35

Re

lati

ve h

eig

ht

Time /h

start of PSIRC

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

10 15 20 25 30 35

Ral

ativ

e h

eig

ht

Time /h

start of PSIRC

middle of riser

near casting

bottom

Location of the hot spot during cooling

process

(c) 30h with PSIRC

Residual stress

without PSIRC 151.4 MPa

with PSIRC 26.3 MPa

B2

B1

Riser

Sand mold

To improve the PSIRC

A

A

1

2

3

4

5

6

7

8

A-A

DT=237oC

DT=85oC

Cooling curves of the points on section A-A

during intermittent PSIRCIntermittent cooling schedule of PSIRC

5. Conclusions

1) Post solidification intensive riser cooling method

(PSIRC) was proposed for heavy steel castings to

realize fast and uniform cooling, in which risers were

cooled by forced air after the solidification of a

casting, turning risers into cooling passages during

the cooling process of castings in contrast to

feeding passages during the solidification process. It

may improve production efficiency and reduce

residual stress and deformation.

5. Conclusions

2) One day was saved for a hydro turbine blade

casting of 0.9 ton melt before shakeout under PSIRC,

its residual stress was greatly reduced. The hot spot

was pushed almost to the casting bottom and at the

middle height, inside out cooling was achieved. To

further improve the effect of PSIRC, intermittent

cooling can make more uniform cooling.

Thanks !