ST37-3

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St37-3 · Q/BQB 130-2003

Chemical composition source verified; this does not verify every standard clause, actual supply or measured heat results

Material category: Carbon steel
Subcategory: Slab steels
Material form: Rough-rolled slabs for rerolling
Original record status: Original standard verified
Standard edition: Q/BQB 130—2003
Table / clause: 4.1.1, Table 3 and notes 1–3
PDF page references: 2、4
Unit: Mass fraction (wt%)
Analysis type: Heat analysis

Source document

Carbon-equivalent reference

Estimates are presented separately for each applicable composition condition. Match the actual ordering conditions; ranges must not be combined.

A deoxidation method; Applies to finished plate thickness <4 mm; Al is total aluminum Al_t

IIW / CEV：0.0733–0.2467 Known-item contribution, not a complete value; missing Cr, Mo, V, Ni, Cu CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; an engineering estimate of welding cold-cracking susceptibility for carbon and low-alloy steels.

Pcm（Ito–Bessyo）：0.0500–0.1677 Known-item contribution, not a complete value; missing Cu, Cr, Ni, Mo, V, B Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B; mainly used for low-carbon low-alloy steels, particularly modern low-carbon pipeline steels; more relevant when C is approximately no higher than 0.11%.

CET：0.0600–0.2000 Known-item contribution, not a complete value; missing Mo, Cr, Cu, Ni CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40; used in welding preheat assessment for ferritic steels, subject to the applicability conditions of EN 1011-2.

A deoxidation method; applicable finished plate thickness 4–<7 mm; Al is total aluminium Al_t

IIW / CEV：0.1067–0.2800 Known-item contribution, not a complete value; missing Cr, Mo, V, Ni, Cu CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; an engineering estimate of welding cold-cracking susceptibility for carbon and low-alloy steels.

Pcm（Ito–Bessyo）：0.0600–0.1777 Known-item contribution, not a complete value; missing Cu, Cr, Ni, Mo, V, B Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B; mainly used for low-carbon low-alloy steels, particularly modern low-carbon pipeline steels; more relevant when C is approximately no higher than 0.11%.

CET：0.0800–0.2200 Known-item contribution, not a complete value; missing Mo, Cr, Cu, Ni CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40; used in welding preheat assessment for ferritic steels, subject to the applicability conditions of EN 1011-2.

A deoxidation method; applicable finished plate thickness 7–<13 mm; Al is total aluminium Al_t

IIW / CEV：0.1400–0.3133 Known-item contribution, not a complete value; missing Cr, Mo, V, Ni, Cu CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; an engineering estimate of welding cold-cracking susceptibility for carbon and low-alloy steels.

Pcm（Ito–Bessyo）：0.0700–0.1890 Known-item contribution, not a complete value; missing Cu, Cr, Ni, Mo, V, B Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B; mainly used for low-carbon low-alloy steels, particularly modern low-carbon pipeline steels; more relevant when C is approximately no higher than 0.11%.

CET：0.1000–0.2400 Known-item contribution, not a complete value; missing Mo, Cr, Cu, Ni CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40; used in welding preheat assessment for ferritic steels, subject to the applicability conditions of EN 1011-2.

A deoxidation method; applicable finished plate thickness 13–<18 mm; Al is total aluminium Al_t

IIW / CEV：0.1800–0.3533 Known-item contribution, not a complete value; missing Cr, Mo, V, Ni, Cu CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; an engineering estimate of welding cold-cracking susceptibility for carbon and low-alloy steels.

Pcm（Ito–Bessyo）：0.1100–0.2290 Known-item contribution, not a complete value; missing Cu, Cr, Ni, Mo, V, B Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B; mainly used for low-carbon low-alloy steels, particularly modern low-carbon pipeline steels; more relevant when C is approximately no higher than 0.11%.

CET：0.1400–0.2800 Known-item contribution, not a complete value; missing Mo, Cr, Cu, Ni CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40; used in welding preheat assessment for ferritic steels, subject to the applicability conditions of EN 1011-2.

A deoxidation method; applicable finished plate thickness 18–25.4 mm; Al is total aluminium Al_t

IIW / CEV：0.2133–0.3867 Known-item contribution, not a complete value; missing Cr, Mo, V, Ni, Cu CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15; an engineering estimate of welding cold-cracking susceptibility for carbon and low-alloy steels.

Pcm（Ito–Bessyo）：0.1200–0.2390 Known-item contribution, not a complete value; missing Cu, Cr, Ni, Mo, V, B Pcm = C + Si/30 + (Mn + Cu + Cr)/20 + Ni/60 + Mo/15 + V/10 + 5B; mainly used for low-carbon low-alloy steels, particularly modern low-carbon pipeline steels; more relevant when C is approximately no higher than 0.11%.

CET：0.1600–0.3000 Known-item contribution, not a complete value; missing Mo, Cr, Cu, Ni CET = C + (Mn + Mo)/10 + (Cr + Cu)/20 + Ni/40; used in welding preheat assessment for ferritic steels, subject to the applicability conditions of EN 1011-2.

Composition record (conditional branches apply; this is not an unconditional requirement)

Element	Composition requirement
C	0.04 ～ 0.13
Si	≤ 0.08 (lower limit not stated)
Mn	0.2 ～ 0.7
P	≤ 0.035 (lower limit not stated)
S	≤ 0.03 (lower limit not stated)
Al	≥ 0.01 (upper limit not stated)

Applicability and limitations

Q/BQB 130—2003 is a standard for slabs produced by initial rolling for subsequent rerolling. The finished plate thickness in Table 3 means the plate thickness after rerolling the slab, not slab thickness or wire diameter. Table 3 gives ladle analysis in mass fraction wt%; C = capped steel, A = aluminium-killed steel, G = aluminium-silicon-killed steel, K = silicon-killed steel. Read the applicable condition row; unlisted elements are not assumed to be zero. Note 3 to Table 3 requires slabs for thick plate (finished thickness ≥15 mm) to use G aluminium-silicon-killed steel; buyer and supplier must verify applicability of rows involving other deoxidation methods. Product-analysis tolerances for killed steel are separately governed by GB/T 222 and must not be mixed with Table 3 ladle-analysis values.