ST50-2

1 source records. Standards, editions and conditions are presented separately; matching grade names do not establish interchangeability.

Refer to each source for mass fractions and analysis type. Missing values are not treated as 0. Manufacturer typical values, standard guarantees and measured heat results must remain separate. Use the material selector for calculations and condition selection.

Open condition selection, comparison and carbon-equivalent tools for ST50-2 →

St50-2 · 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.

K deoxidation method; Applies to finished plate thickness <10 mm

IIW / CEV：0.2850–0.4583 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）：0.2365–0.3592 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：0.2550–0.3950 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	0.21 ～ 0.3
Si	0.12 ～ 0.35
Mn	0.45 ～ 0.95
P	≤ 0.035 (lower limit not stated)
S	≤ 0.035 (lower 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.

Original condition-branch records

K deoxidation method; Applies to finished plate thickness <10 mm

Element	Composition requirement
C	0.21 ～ 0.3
Si	0.12 ～ 0.35
Mn	0.45 ～ 0.95
P	≤ 0.035 (lower limit not stated)
S	≤ 0.035 (lower limit not stated)

Combined limits

PDF page references in the source

Source table row number

A condition branch must be selected

Yes

Verification notes

Baosteel original Table 3, merged cells and notes checked row by row; select conditions by deoxidation method and finished-product thickness.