概述
Q345A市場價格比Q345B,C,D,E要低Q345是一種鋼材的材質。它是低合金鋼，廣泛套用於橋樑、車輛、船舶、建築、壓力容器等。Q代表的是這種材質的屈服，後面的345，就是指這種材質的屈服值，在345MPa左右。並會隨著材質的厚度的增加而使其屈服值減小。
參考標準：GB/T1591-2008《低合金高強度結構鋼》
註：Q345最新標準GB/T1591-2008相對於老標準，最明顯的一個變化就是Mn元素含量的變化，從原來的1.0-1.60更正為≤1.70，取消了最小值的限定。
隨著現代工業的發現，科技的不斷進步，各種微量元素在鋼板中的套用也更加廣泛，Mn含量不再是影響鋼材強度和機械性能的唯一因素。所以中華人民共和國國家質量監督檢驗檢疫總局和中國國家標準化管理委員會聯合發布實施的低合金高強度結構鋼標準，取消Mn含量區間的限定，只規定最大值。
對於Q345鋼材的檢測，一方面是鋼材的元素含量是否達到國標要求，最重要的一方面是通過專業機構檢測鋼材的機械性能（屈服強度、拉伸試驗）是否達到標準。
規格尺寸
| Q345A | 規格厚度*寬度*長度（mm） | 重量（噸）定軋 |
| Q345A | 8*1500-2550*9200-12500 | 186.188T |
| Q345A | 9*1850-2600*9200-12450 | 136.537T |
| Q345A | 10*2650-3000*8000-10000 | 221.381T |
| Q345A | 12*1800-2550*9000-11000M | 235.377T |
| Q345A | 14*1850-2500*7600-10000M | 165.027T |
| Q345A | 15*2000-3000*6800-14000M | 238.839T |
| Q345A | 16*2050-3000*8000-12100 | 199.406T |
| Q345A | 17*2200-2900*7600-11350M | 116.154T |
| Q345A | 18*1700-2200*9300-15900M | 168.481T |
| Q345A | 20*2200-3400*8800-10500 | 164.316T |
| Q345A | 22*2600-3100*8150-10100M | 187.631T |
| Q345A | 24*1900-2360*8770-13700M | 148.956T |
| Q345A | 25*2000-2950*8000-11000M | 175.095T |
| Q345A | 26*2000-2950*9700-13000 | 144.577T |
| Q345A | 28*1800-2450*7800-10000 | 89.771T |
| Q345A | 30*1820-2450*9450-10800M | 145.525T |
| Q345A | 32*1800-3200*8000-11200M | 180.433T |
| Q345A | 34*1950-2850*8600-10200M | 125.526T |
| Q345A | 35*1800-2700*7800-11800 | 152.484T |
| Q345A | 36*1950-2400*7800-11000 | 132.29T |
| Q345A | 38*2420-3200*9200-14000M | 120.093T |
| Q345A | 40*1900-2800*8150-12000M | 164.953T |
| Q345A | 44*1800-2400*8500-12000 | 252.222T |
| Q345A | 45*1800-2470*8350-10200 | 174.363T |
| Q345A | 46*1800-2340*8000-10900M | 225.464T |
| Q345A | 48*1950-2850*9500-14000M | 156.281T |
| Q345A | 50*1900-2800*9300-12500 | 164.282T |
| Q345A | 52*2100-2600*8800-12000 | 113.544T |
| Q345A | 55*1820-2300*8000-11800M | 318.904T |
| Q345A | 56*2510-3200*9500-15400M | 132.992T |
| Q345A | 59*2400-3100*8200-11400 | 218.115T |
| Q345A | 60*2220-2950*8500-12000 | 220.604T |
| Q345A | 64*2250-2850*8600-13150M | 368.781T |
| Q345A | 65*1800-2500*8400-12000M | 288.327T |
| Q345A | 70*2200-2900*9300-13000 | 175.707T |
| Q345A | 72*2250-2950*6000-9500 | 130.14T |
| Q345A | 74*2240-2980*8200-12000M | 227.67T |
| Q345A | 75*1700-2800*7590-11500M | 181.904T |
| Q345A | 76*2600-3100*3800-5600 | 178.348T |
| Q345A | 78*2320-2850*4500-9500 | 129.489T |
| Q345A | 80*2300-2900*9300-12000M | 215.319T |
| Q345A | 82*2340-3100*5600-9500M | 226.585T |
| Q345A | 85*2200-2500*9300-10350 | 196.931T |
| Q345A | 88*2130-2850*7400-10000 | 208.962T |
| Q345A | 90*2300-3600*9400-11000M | 250.461T |
| Q345A | 92*2100-2900*6800-9800M | 326.431T |
| Q345A | 95*2150-2680*9300-10850 | 136.106T |
| Q345A | 96*2150-2650*8050-11500 | 126.043T |
| Q345A | 98*1710-2470*9200-12400M | 281.438T |
| Q345A | 100*1800-2500*8700-10500 | 220.305T |
| Q345A | 102*1900-2500*7950-10500 | 330.139T |
| Q345A | 105*2200-2950*6900-12300 | 268.934T |
| Q345A | 106*2600-3200*8750-11200M | 363.93T |
| Q345A | 110*1700-2400*8000-11800 | 220.523T |
| Q345A | 112*1750-2400*6250-9600 | 161.157T |
| Q345A | 115*2200-2900*8500-11000M | 561.688T |
| Q345A | 116*2400-3000*7200-10000M | 313.735T |
| Q345A | 120*2000-2900*7000-10000 | 320.042T |
| Q345A | 125*1760-2560*8400-10400 | 81.306T |
| Q345A | 126*1760-2360*7800-12000M | 302.561T |
| Q345A | 130*2600-3350*8500-10560M | 160.102T |
| Q345A | 132*2030*2650*8500-12300 | 360.88T |
| Q345A | 135*2200-2900*9600-11500 | 150.374T |
| Q345A | 140*1700-2400*8100-12100M | 192.386T |
| Q345A | 150*2100-2600*7200-11250M | 320.507T |
| Q345A | 160*1960-2460*7600-12250 | 320.062T |
| Q345A | 180*1800-2300*7350-11250 | 152.358T |
| Q345A | 190*2210-2610*8400-12000M | 198.966T |
| Q345A | 195*2200-2800*6600-9600M | 46.226T |
| Q345A | 200*1720-3060*7000-12000 | 69.408T |
| Q345A | 202*2200-2900*4400-8500 | 88.35T |
| Q345A | 210*1500-2200*5900-9500M | 68.589T |
| Q345A | 215*1500-2500*8500-12000M | 96.563T |
| Q345A | 220*2170-2670*6000-9000 | 58.866T |
| Q345A | 230*1800-2300*6700-10000 | 200.911T |
| Q345A | 232*1800-2600*6200-11400M | 80.161T |
| Q345A | 240*2000-2500*5000-10000M | 64.89T |
| Q345A | 250*2100-2900*8500-12000 | 86.599T |
| Q345A | 260*1900-2500*6200-10000 | 110.459T |
| Q345A | 260*1970-2470*7500-11500M | 100.459T |
| Q345A | 270*2000-2600*6000-11500M | 120.744T |
| Q345A | 272*2070-2650*5000-9500 | 69.994T |
| Q345A | 280*2390-3100*7500-12000 | 90.836T |
| Q345A | 290*1940-2600*6600-13000M | 79.177T |
| Q345A | 300*2390-3200*6500-10000M | 56.675T |
| Q345A | 320*2630-3500*9500-15000M | 261.823T |
| Q345A | 其它規格協商定軋 |
化學成分
| 牌號 | C | Si | Mn | P | S | V | Nb | Al | Ti |
| Q345A | 0.20 | ≤0.55 | ≤1.70 | ≤0.045 | ≤0.045 | 0.02-0.15 | 0.015-0.060 | - | 0.02-0.20 |
| Q345B | ≤0.20 | ≤0.55 | ≤1.70 | ≤0.040 | 0.040 | 0.02-0.15 | 0.015-0.060 | - | 0.02-0.20 |
| Q345C | ≤0.20 | ≤0.55 | ≤1.70 | ≤0.035 | ≤0.035 | 0.02-0.15 | 0.015-0.060 | ≥0.015 | 0.02-0.20 |
| Q345D | 0.18 | ≤0.55 | ≤1.80 | ≤0.030 | ≤0.030 | 0.02-0.15 | 0.015-0.060 | ≥0.015 | 0.02-0.20 |
| Q345E | ≤0.18 | ≤0.55 | ≤1.80 | ≤0.025 | ≤0.025 | 0.02-0.15 | 0.015-0.060 | ≥0.015 | 0.02-0.20 |
定義
Q345A度鋅角鋼②必要時鋼號後面可標出表示質量等級和脫氧方法的符號。質量等級符號分別為A、B、C、D。脫氧方法符號：F表示沸騰鋼；b表示半鎮靜鋼：Z表示鎮靜鋼；TZ表示特殊鎮靜鋼，鎮靜鋼可不標符號，即Z和TZ都可不標。例如Q235-AF表示A級沸騰鋼。
③專門用途的碳素鋼，例如橋樑鋼、船用鋼等，基本上採用碳素結構鋼的表示方法，但在鋼號最後附加表示用途的字母。
Q345A的機械性能是什麼:
壁厚mm≤16,伸長率δ5≥（%）21,屈服強度δs(MPa≥)345,試驗溫度℃不需,抗拉強度σb(MPa≥)（470-630）。
