Specifications and Dimensions of Bulb Flat Bar

Aug 28, 2026
Tags: Bulb Flat Bar

Accurate specification selection is the foundation for the safe and proper use of bulb flat bar. The production and application of bulb flat bar comply with unified international standards such as ASTM A131, EN 10067, and GB/T 9945, which provide a comprehensive set of specifications covering dimensions, steel grades, mechanical properties, and dimensional tolerances, and meet the inspection and certification requirements of major classification societies such as ABS, LR, BV, DNV, and CCS.

1. Specifications and Dimensions

Dimensions of Bulb Flat Bar

The specifications for spherical flat bars are denoted as “height (mm) × web thickness (mm),” where “height” refers to the total external dimension, including the protrusion of the spherical head.

Common mainstream specifications are listed in the table below and cover most shipbuilding and offshore engineering applications.

Model	Nominal Dimensions (mm)					Sectional Area (cm²)	Weight (kg/m)
Model	b	d	h	r1	r	Sectional Area (cm²)	Weight (kg/m)
80 × 5	80	5	19	4	≤ 1.5	5.41	4.25
80 × 6	80	6	20	4	≤ 2	6.21	4.88
100 × 7	100	7	22.5	4.5	≤ 2	8.74	6.86
100 × 8	100	8	23.5	4.5	≤ 2	9.74	7.65
120 × 6	120	6	23	5	≤ 2	9.32	7.32
120 × 7	120	7	24	5	≤ 2	10.52	8.26
120 × 8	120	8	25	5	≤ 2	11.72	9.20
140 × 7	140	7	26	5.5	≤ 2	14.43	9.75
140 × 8	140	8	27	5.5	≤ 2	12.83	10.85
140 × 9	140	9	28	5.5	≤ 2	15.20	11.93
140 × 10	140	10	29	5.5	≤ 3	16.63	13.05
160 × 7	160	7	29	6	≤ 2	14.60	11.46
160 × 8	160	8	30	6	≤ 2	16.20	12.72
160 × 9	160	9	31	6	≤ 2	17.80	13.97
160 × 11	160	11	33	6	≤ 3	21.00	16.49
180 × 8	180	8	33	7	≤ 2	18.86	14.80
180 × 9	180	9	34	7	≤ 2	20.66	16.22
180 × 10	180	10	35	7	≤ 3	22.46	17.63
180 × 11	180	11	36	7	≤ 3	24.26	19.04
200 × 9	200	9	37	8	≤ 2	23.66	18.57
200 × 10	200	10	38	8	≤ 3	25.66	20.14
200 × 11	200	11	39	8	≤ 3	27.66	21.71
200 × 12	200	12	40	8	≤ 3	29.66	23.28
220 × 10	220	10	41	9	≤ 3	29.00	22.77
220 × 11	220	11	42	9	≤ 3	31.20	24.50
220 × 12	220	12	43	9	≤ 3	33.40	26.22
240 × 10	240	10	44	10	≤ 3	32.49	25.50
240 × 11	240	11	45	10	≤ 3	34.89	27.39
240 × 12	240	12	46	10	≤ 3	37.29	29.27
260 × 10	260	10	47	11	≤ 3	36.11	28.35
260 × 11	260	11	48	11	≤ 3	38.71	30.39
206 × 12	260	12	49	11	≤ 3	41.31	32.43
260 × 13	260	13	50	11	≤ 3	43.85	34.43
280 × 11	280	11	51	12	≤ 3	42.68	33.50
280 × 12	280	12	52	12	≤ 3	45.48	35.70
280 × 13	280	13	53	12	≤ 3	48.28	37.90
300 × 11	300	11	54	13	≤ 3	46.78	36.70
300 × 12	300	12	55	13	≤ 3	49.79	39.09
300 × 13	300	13	56	13	≤ 3	52.79	41.44
320 × 12	320	12	58	14	≤ 3	54.25	42.60
320 × 13	320	13	59	14	≤ 3	57.25	45.09
320 × 14	320	14	60	14	≤ 4	60.85	47.60
340 × 12	340	12	61	15	≤ 3	58.84	46.20
340 × 13	340	13	62	15	≤ 3	62.24	48.86
340 × 14	340	14	63	15	≤ 4	65.54	51.50
370 × 13	370	13	66.5	16.5	≤ 3	69.70	54.70
370 × 14	370	14	67.5	16.5	≤ 4	73.40	57.60
370 × 15	370	15	68.5	16.5	≤ 4	77.10	60.50
400 × 14	400	14	72	18	≤ 4	81.48	63.96
400 × 15	400	15	73	18	≤ 4	85.48	67.10
400 × 16	400	16	74	18	≤ 4	89.48	70.20
430 × 14	430	14	76.5	19.5	≤ 4	89.70	70.60
430 × 15	430	15	77.5	19.5	≤ 4	94.19	73.90
430 × 17	430	17	79.5	19.5	≤ 4	102.79	80.70
430 × 19	430	19	81.5	19.5	≤ 4	111.39	87.40
430 × 20	430	20	82.5	19.5	≤ 4	115.00	90.80

* Length：6m / 9m / 12m / custom

2. Steel Grade Classification

Bulb flat bar is classified into two strength grades: standard strength and high strength:

Ordinary-strength grades: A, B, D, E, which offer good low-temperature toughness and weldability;

High-strength grades: AH32, AH36, AH40, DH32, DH36, DH40, EH32, EH36, EH40, suitable for large ocean-going vessels, deep-sea platforms, and high-load-bearing structures.

Different grades correspond to different yield strengths, tensile strengths, and low-temperature impact properties; they must be selected and matched strictly in accordance with engineering design standards.

3. Dimensional Tolerance Standards

Dimensional tolerances are a key indicator of the quality of bulb flat bar. Hot-rolled bulb flat bar is subject to strict tolerance standards:

Height tolerance: ±2 – 3 mm

Thickness tolerance: ≤ ±0.5 mm

Straightness: Complies with standard requirements

All qualified products come with a factory test report and a classification society certification mark, ensuring full compliance with international engineering acceptance standards.

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