CASE STUDY: SITHERM S353R Hot Work Steel in Shotblock Applications

SITHERM S353R outperforms commonly used hot work tool steels in every parameter

iTherm® Shot block

Introduction

This case study compares the performance of the premium hot work tool steel SITHERM S353R with a commonly used H13 / 1.2344 steel, in the iTherm® conformally cooled shot block application.

Shotblocks are exposed to high mechanical pressure and are essential in high-pressure die casting, serving as a critical component that distributes the molten alloy into the die. Steel selection is essential for conformally cooled shot blocks, since the channels are positioned as close to the working surface as possible, and engineered for extreme temperature oscillations and high thermal gradients.

Shot blocks endure extreme heat and pressure during the casting process, facing temperatures from 300°C to 550°C and pressures up to 2.000 bar. Therefore steels like H13 / 1.2344 or 1.2367 are used for shot blocks due to their high thermal conductivity, wear resistance, and toughness. These materials maintain dimensional stability and prevent deformation or cracking under harsh conditions, ensuring accurate and durable casting tooling.

 

Steel shotblock

Choosing the right tool steel for shotblocks is very important due to the high, oscillating temperature, which significantly impacts the lifespan of the shotblock.

Material comparison

 

 

Material

Description

Conductivity*
(at 400°C)

Solidification time [s]*

Tensile strenght 
@ 5HRc, Rm

Toughness* 

1.2344

Standard hot work steel

27 W/mK

11.9

1420 MPa

17 J

 

S353R

Premium hot work steel

31 W/mK

11.2

1490 MPa J

≥ 23 J

*Thermal conductivity at high temperatures is crucial for predicting how a material behaves under the thermal loads typical in die casting processes.
*Solidification time directly impacts the efficiency and quality of the casting process, including cycle time, final product material properties, defects, etc.
 *Toughness measures the material's ability to absorb energy and plastically deform without fracturing, essential for withstanding the thermal shocks and mechanical stress during casting.

 

Chemical composition 
 

W. Nr.

C

Si

Mn

Cr

Mo

V

1.2344

1.2344

0.40

1.05

0.40

5.15

1.35

1.00

S353R

~1.2367

0.36  

0.30  

0.30  

5.00  

2.30  

0.60 

 

PERFORMANCE COMPARISON

The comparison focuses on crack initiation timing, thermal performance and key factors that influence the reliability and efficiency of the shotblock.

1. Crack initiation 

Shotblock made from SITHERM S353R steel performs 3.200 shots before the first signs of thermal cracking appear, while 1,2344 starts to crack at 720 shots.

Crack initiation timing is an essential factor in evaluating a material's resistance to heat checking, a common form of wear in die casting tools caused by thermal cycling.


IMAGE: Comparative analysis highlighting the number of cycles each material can withstand before showing first signs of cracking.

2. Thermal performance 

The SITHERM S353R demonstrates superior thermal performance with both maximum and average temperatures after spraying being significantly lower than H13 made shotblock.

Temperature after spraying shows how well a material handles and cools down from the heat during casting. Lower temperatures mean better cooling, less stress, and longer tool life.

This indicates its enhanced ability to dissipate heat, ensuring that shotblocks made from SITHERM S353R are less susceptible to thermal fatigue.

3. Cycle time improvement  

S353R-made shotblock enables 0.7 seconds faster tablet solidification, than H13, resulting in shorter cycle times.

After 250,000 shots, the shot block made with S353R saves 17,000 seconds, or 48 hours, compared to shotblock made using the 1.2344 steel. 

Conclusion

 

The SITHERM S353R premium hot work tool steel demonstrates superior performance across several critical metrics: 
- thermal performance, 
- resistance to crack initiation, and 
- thermal conductivity.

 

Its ability to maintain lower temperatures after spraying and its higher thermal conductivity at elevated temperatures make it an ideal choice for applications requiring resilience and durability.

Combined with its enhanced toughness, these properties ensure that components made from SITHERM S353R can withstand the aggressive conditions of die casting processes better than those made from traditional H11 or H 13 steels.

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