Uncoated Plain Carbon Steels Steel Production

Lesson Objectives When you finish this lesson you will understand: The principles of basic steel making and casting The principles of steel rolling Factors effecting steel properties Learning Activities 1.Look up Keywords 2.View Slides; 3.Read Notes, 4.Listen to lecture 5.Do on-line workbook 6.Do homework Keywords Hot Rolling, Cold Rolling, Interstitial Free Steels, Mild Steel, Rephosphorized Steel, High Strength Low Alloy Steels, Transformation Hardened Steels, Recovery Annealed Steels, Basic Oxygen Steel Making, Casting, Continuous Casting, Vacuum Arc Remelting, Dynamic Recrystallization, Grain Refinement, Tempering

Classification of Sheet Steels Steel Type Interstitial-Free Steel Mild Steel Rephosphorized Steel PPN Hardened/Grain Refined Steel (HSLA) Transformation Hardened Steel Chemistry C < 0.01% Boron & Ti additions C: % Mn: 0.3% P: 0.07% Cb & V: 0.02% C: % Mn: % + Si TS. < 30 ksi Elongation: 50% TS. < 40 ksi Elongation: 30% TS. > 40 ksi Elongation > 20% TS.: ksi TS.: ksi Mechanical Properties Hot Rolled Cold Rolled Recovery Annealed

Steel Melting and Casting Making, Shaping & Treating of Steel, USS, 1964 C+O=CO 2 Alloy Additions

A Few Melting Practice Problems Which Can Result in Weld Problems Porosity Loss of Intended Alloy Addition Intermetallic Inclusions Stringers or Banded Material Poor Ingot Surface Carried Over to Strip

Steel refining - IF Steels Making, Shaping & Treating of Steel, USS, 1964

Classification of Sheet Steels Steel Type Interstitial-Free Steel Mild Steel Rephosphorized Steel PPN Hardened/Grain Refined Steel (HSLA) Transformation Hardened Steel Chemistry C < 0.01% Boron & Ti additions C: % Mn: 0.3% P: 0.07% Cb & V: 0.02% C: % Mn: % + Si TS. < 30 ksi Elongation: 50% TS. < 40 ksi Elongation: 30% TS. > 40 ksi Elongation > 20% TS.: ksi TS.: ksi Mechanical Properties Hot Rolled Cold Rolled Recovery Annealed

Hot Rolling of Strip Dynamic Recrystallization Followed by Grain Growth Large Grain Austenite Large Grain Austenite Transforms Ferrite/Pearlite Fine = Higher Strength Coarse = Lower Strength CQ, DQ & IF Steels Rephosphorized Steel

Controlled Hot Rolled Strip Processing Dynamic Recrystallization Pinned Grain Boundaries ppt Grain Refinement HSLA Steels SolidSolution(Rephos) HSLA Steel Dual Phase Steel TRIP Steel

Turn to the person sitting next to you and discuss (1 min.): The particles that pin the grain boundaries during hot rolling are carbides and carbonitrides of niobium, vanadium and titanium. These each have their own dissolution temperature where they go back into solution in the steel. What happens if the temperature of the strip is just below this dissolution temperature (I.e. the particle have precipitated and are available for pinning grains) just before the strip goes through a hot rolling mill? Why might steel makers select a combination of these elements for their chemistry formulation?

Classification of Sheet Steels Steel Type Interstitial-Free Steel Mild Steel Rephosphorized Steel PPN Hardened/Grain Refined Steel (HSLA) Transformation Hardened Steel Chemistry C < 0.01% Boron & Ti additions C: % Mn: 0.3% P: 0.07% Cb & V: 0.02% C: % Mn: % + Si TS. < 30 ksi Elongation: 50% TS. < 40 ksi Elongation: 30% TS. > 40 ksi Elongation > 20% TS.: ksi TS.: ksi Mechanical Properties Hot Rolled Cold Rolled Recovery Annealed

Cold Rolling and Annealing Recovery Recrystallization Cold Worked Structure

Classification of Sheet Steels Steel Type Interstitial-Free Steel Mild Steel Rephosphorized Steel PPN Hardened/Grain Refined Steel (HSLA) Transformation Hardened Steel Chemistry C < 0.01% Boron & Ti additions C: % Mn: 0.3% P: 0.07% Cb & V: 0.02% C: % Mn: % + Si TS. < 30 ksi Elongation: 50% TS. < 40 ksi Elongation: 30% TS. > 40 ksi Elongation > 20% TS.: ksi TS.: ksi Mechanical Properties Hot Rolled Cold Rolled Recovery Annealed

Transformation Hardened Steels H2OH2O H2OH2O Martensitic Structure

Tempering

Spot Weldability (Production of Welds Fit for Service) Process Variables (Things Manufacturers Control) Material Variables (Things Steel Makers Control) Module 3Module 4

Assignment 2