2. Chapter 7

3. §7.2 The Basic Knowledge Smelt process of steels and effects on the quality of them  smelt principles  effects of furnace and deoxygenate degree Classification  by chemical component  by quality  by structure uses

4. Put the fused molten iron or coke and iron ore to the oven for fining to make char and other impurities volatilization through oxidation or change them into oxide to become slag. All these can reduce the impurity. Smelt principles Smelt process of steels and effects on the quality of them

5. Process coke ironstone pig iron blast furnace melt pig iron smelt oxidizedeoxidize steel Cast ingot ingot steel ingot constructionsteel Fig.7.2.1 Smelt process of steel

6. Effects of furnace and deoxygenate degree Effect of furnace and deoxidation degree are listed in Tab.7.2.1 and Tab.7.2.2

7. Effect of Furnace Tab.7.2.1 Effect of Furnace Furnace model Material Inbreat he gas Smelt time Steel quality CostUses Oxygen converter Melt molten iron Pure oxygen 15- 30min HighLow High quality carbon steel and alloy steel Even furnace Pig iron, ironstone Air5-12hrHighHigh The same above and especial steel Electric cooker Electric cooker Steel waste,pig iron Airshort Excelle nt High The same above

8. The process of deoxidation will get rid of the impurities Some of the iron will inevitably be oxidized advances the occurrence of large quantities of air bubbles affects the quality of the steel In order to deoxidize FeO and Fe 2 O 3 into iron, we must add deoxidant in the later period. Deoxidation degree

9. Tab.7.2.2 Deoxidation degree and steels quality Types of steel Deoxidation degree Cooling circs Steels quality Boiling steel Low Large amounts of CO floating while pouring Unqualified Half sedation steel MediumExcellent Sedation steel High No CO floating in the air while cooled still Dense tissue,well- distribution,excelle nt mechanical property Special sedation steel ThoroughPerfect

10. 1.Carbon Steel Low Carbon Steel C<0.25% √ Medium Carbon Steel C=0.3 ～ 0.55% High Carbon Steel C>0.6% 2.Alloy steel Low Alloy Steel <5% √ Medium Alloy Steel = 5 ～ 10% High Alloy Steel >10% by chemical Component

11. Tab.7.2.3 Chemical component of carbon steel （ GB700—88 ） coden ames gra de chemical component % oxigenate method CMn SiSP ≤ Q1950.06~0.120.300.0500.045 F、b、ZF、b、ZF、b、ZF、b、Z Q215 A 0.09~0.150.25~0.550.300.0500.0450.045 F、b、ZF、b、ZF、b、ZF、b、Z B Q235 A0.14~0.220.30~0.65 0.30 0.050 0.045 F、b、ZF、b、ZF、b、ZF、b、Z B0.12~0.200.30~0.700.045 C≤0.180.35-0.800.0400.040Z D ≤0.17 0.0350.035TZ Q255 A 0.18~0.280.40~0.700.30 0.050 0.045Z B0.045 Q2750.20~0.380.50~0.800.350.0500.045Z

12. by quality Common Steel P ≯ 0.045%,S ≯ 0.055% High Quality Steel P ≯ 0.035-0.04%,S ≯ 0.04% Advanced High Quality Steel P ≯ 0.025%,S ≯ 0.025%

13. by structure use Structure Steel Low-carbon steel, medium-carbon steel, kinds of engineering components and mechanical parts Tool Steel tools, mould Special steel stainless steel, heat-resistant steel, wear- resistant steel