1、Q235的屈服強度下限為235MPa,Q345的屈服強度下限為345MPa(Q的意義為漢字的"屈"字，后面的數(shù)值代表屈服強度下限)

2、二者合金含量不同：Q235為普通碳鋼，Q345為低合金鋼

　　Q235是碳素結構鋼,與舊標準GB700-79牌號對照A3、C3

　　Q345是低合金結構鋼，與舊標準1591-88牌號對照12MnV、16Mn 16MnRE、18Nb、14MnNb

　　Q235--金屬結構件，心部強度要求不高的滲碳或零件，拉桿、連桿、吊鉤、車鉤、螺栓螺母、套筒、軸及焊接件

無縫管q235尺寸規(guī)格     規(guī)格	現(xiàn)貨/噸	規(guī)格	數(shù)量/噸
10×2	18	95×4.5-6-8-10-12-14-16-20	50
12×2	18	102×4.5-5-6-7-8-10-12-14-16-20	80
14×2-2.5-3	20	108×4.5-5-6-7-8-10-12-14-18-20-22	75
16×2-2.5-4	30	114×4.5-5-6-7-8-10-12-14-18-20	100
18×2.3-4-5	20	121×4.5-5-6-7-8-10-12-14-16-20	102
20×2.5-3-5	17	127×4.5-5-6-7-8-10-12-14-16-20	95
24×2.5-3-4-5-6	25	133×4.5-6-8-12-14-16-18-20-25-30	120
25×2.5-3-4-5-6	28	140×5-6-7-8-9-10-12-14-16-20-22	50
28×3-3.5-4-5-6	30	146×4.5-6-8-12-14-16-18-20-25-30	60
32×3.5-4-5-6-8	40	152×4.5-6-8-12-14-16-18-20-25-30	60
34×4-5-6-8	35	159×4.5-6-10-12-14	80
36×3.5-5-6-8	30	159×16-18-20-22-25-30	30
38×4-5-6-7-8-9-10	33	168×8-10-12-14-20-25-30-35	130
39×3.5-5-8-10	30	180×8-12-16-25-30	105
42×3.5-4-5-6-7-8-9-10	35	180×32-34-38-40-45-50	102
45×3.5-4-5-6-7-8-9	40	194×6-8-12-16-20-25-30-40-45-50	140
48×3.5-4-5-6-7-8-9-10	24	203×6-7-10-15-20-25-30	90
51×3.5-4-5-6-7-8-9-10	60	203×32-36-40-45-50	70
56×3.5-4-5-6-7-8-9-10	58	219×6-8-12-16-18-20-25	110
57×3.5-5-6-7-8-9-10-12	50	219×30-40-45-50-55	65
60×3.5-4.5-5-6-7-8-9-12-14	60	219×55-58-60-65-70	80
63×3.5-4.5-5-6-7-8-9-10-12-14	40	245×8-10-14-17-20-22	105
68×4-4.5-5-6-7-8-9-10-12-14-16	35	245×25-28-30-34-40	84
70×4-4.5-5-6-7-8-9-10-12-15-16	40	273×7-9-12-15-18-20-25	100
73×4-4.5-5-6-7-8-9-10-12-15	50	273×30-35-38-40-45-50	50
76×4-4.5-5-6-7-8-9-10-12-14	60	299×8-12-16-20-24-28	60
83×4.5-5-10-12-14-16-18-20	30	299×30-32-36-38-40-45	70
89×4.5-8-10-12-14-16-18-20	40	325×8-12-14-18-38-42	120