Issue 61

E. Entezari et alii, Frattura ed Integrità Strutturale, 61 (2022) 20-45; DOI: 10.3221/IGF-ESIS.61.02

Heat treatment temperature range (°C)

Melting temperature (°C)

Operating temperature range (°C)

Heat treatment types

Bath components

Composition (Wt.%)

KNO 3 NaNO 2 NaNO 3 NaNO 2 KNO 3 NaNO 3 KNO 3 NaNO 3 KNO 3 NaNO 2 NaNO 3 NaNO 2 KNO 3 NaNO 3

50-60 40-50 50-60 40-50 50-60 40-50 50-60 40-50 50-60 40-50 50-60 40-50 10-15 20-30 40-50 15-20 45-55 45-55 100 100

135

160-550

145

150-500

Austempering

200-400

225

250-600

337 370 135

350-500 400-600 160-550

Martempering

Above Ms

145

150-500

225

250-600

NaCl KCl BaCl 2 CaCl 2

400

500-800

NaCO 3 KCl

450

550-900

Hardening

760-1260

BaCl 2 KCl2 NaCl BaCl 2 NaCl

50 30 20

40

570-900

70-96 4-30

600-800

700-1250

Quenching between M s and M f & partitioning above Ms

Quenching - partitioning

KOH NaOH

60-75 25-40

130-160

150-350

Table 2: Types of heat treatment applied for the manufacturing of high-strength steels with the chemical composition and melting temperature of salt baths.

API- 5XL Steel grades

Finish Rolling Temperature (°C)

Finish Cooling Temperature (°C)

Cooling rate ( ° °C/S)

Ref

X70

750-850

450-600

16-23

[45,46]

X80

810-890

500-550

20-40

[47-49]

X100

800-830

250-530

30-38

[50-53]

X120

800-840

300-450

33-35

[54-56]

Table 3: The overview of a balanced combination of main temperatures parameters in TMCP.

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