Melting and casting technologies for the production of tool steels Dr. Harald Holzgruber, CEO DI Alexander Scheriau, CSO

Transcription

1 Tool 2016, Bratislava, October 5 th 2016 Melting and casting technologies for the production of tool steels Dr. Harald Holzgruber, CEO DI Alexander Scheriau, CSO

2 Global Alloy Tool Steel Products 2015 [ 000 metric tonnes] TOTAL Total World: 1,930 NAFTA: 250 Other America: 60 Europe: 600 Asia: 900 Others: 120 Total ATS Total HSS Total World: 1,780 Total World: 150 TOTAL BARS Other Products TOTAL 1,320 TOTAL 460 Forged Bars* 690 Flat Products 300 Hot Rolled Bars 210 Others 160 Cold Finished Bars 420 *incl. die blocks Picture credits: Böhler Edelstahl GmbH & Co KG Picture credits: Böhler Bleche GmbH & Co KG Picture credits: Deutsche Edelstahlwerke Data provided by

3 Alloy Tool Steel Structure 2015 Europe Rest of the World PM 42% HSS 7% PM 38% HSS 9% CW 24% HW 27% CW 26% HW 27% Data provided by Tool steel grades: Hot work steel (HW) Cold work steel (CW) Plastic mould steel (PM) High speed steel (HSS)

4 [ 000 tonnes] TOP 20 tool steel producers High Speed Steel Alloy Tool Steel * excluding trade volumes (externally sourced) Data provided by

5 Properties and influence factors Chemistry Heat/surface treatment Forging Hardness Red hardness Wear resistance Polishability Low levels of inclusion Cleanliness Hot toughness Retention of hardness Hot strength Thermal shock resistance Thermal conductivity Melting Refining Remelting Casting

6 Typical process route for tool steels

7 Typical process route for tool steels

8 EAF Electric Arc Furnace

9 EAF Main tasks and trend Primary melting unit in alloy steel making process Melting of various kinds of scraps and ferro-alloys Dephosphorisation and decarburisation using oxygen and lime Trend towards Improved productivity Decreased energy consumption Increased flexibility

10 EAF Melting optimisation The EAF Melting Process requires the combination of 2 main energy sources: CHEMICAL ENERGY (burners, oxygen lances, carbon injectors) ELECTRICAL ENERGY (electric arc) PROCESS TOOLS AUTOMATION TOOLS The optimum control of the two power input together with all the activities needed for process and turnaround is the KEY for EAF process optimization

11 EAF Melting optimisation Case study of 55t EAF for Tool Steels: Upgrade of existing EAF to decrease energy consumption and tap-to-tap-time Installation of SwingDoor and chemical energy Package

12 Power On Time (min) Specific Electric Energy (kwh/t) EAF Achived savings 700 Specific Electric Energy Consumption OLD; Target; Average; Electric energy reduction: - 94 kwh/t (-16.2 %) Power ON Time (all heats) - power OFF < 62 min OLD; 74.0 August September October November December January February Heats 60 Average; 64.0 Target; 64.0 Specific Electric Energy (LS) Target Average OLD 10 per. Mov. Avg. (Specific Electric Energy (LS)) Power ON reduction: - 10 min (-13.5 %) Heats Power ON Target Average OLD 10 per. Mov. Avg. (Power ON)

13 EAF Telescopic Furnace Increased yield due to low oxidation Increased productivity due to one scrap bucket charging High flexibility (one bucket is one steel grade)

14 Typical process route for tool steels

15 Refining - Typical units Ladle Furnace Heating Trimming Desulphurisation VD/VOD Degassing Decarburisation

16 Refining - Tasks Final adjustment of chemical composition Decreasing gas content in the melt Improved steel cleanliness

17 Refining - Challenges Many steelgrades with challenging target values Various combination of different process units requires clever process modelling

18 Level 2 Process model Metallurgical Order Management Models Temperature Mass and Chemical Composition of Steel Bath Mass and Chemical Composition of Slag The integrated metallurgical models dynamically (cyclic) calculate the temperature, the mass and the chemical composition of the steel bath and the slag along the whole process route.

19 Typical results of degassing model Hydrogen content Results presented at AISTech2016 together with

20 Typical process route for tool steels

21 Casting

22 Casting - Trends Bottom pouring is still the dominant process Two major trends can be observed: 1. Mechanisation / automation of ingot casting 2. Continuous casting

23 ATS advanced teeming system

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25 Segment Casting Tool steels usually cannot be cast on a bow typecaster. Vertical CC have enourmous investment cost. Therefore new plant concepts have to be developed. Features Semi-continuous vertical casting process Combination of advantages of vertical ingot casting with continuous casting Casting steel grades that cannot be cast on a conventional bow-type caster (i.e. alloyed and special steels) Suited for all casting shapes (round, square, rectangular, slab) Up to 1200 mm diameter

26 Segment Casting Client (Europe)

27 Typical process route for tool steels

28 ESR

29 Why remelting? Cleanliness Level Ingot Structure Forging Operation Reduced content of nonmetallic inclusions Lower size of remaining inclusions Close control of chemical analysis from bottom to top Slow directional solidification Minimization of segregations Minimization of pores Higher Yield Lower forging ratio Cylindrical Ingot with uniform diameter Less Forging Steps Higher ductility, less anisotropy Improved mechanical properties

30 Ingot structure of ESR material Comparison: left: conventional cast ingot right: remelted condition Microstructure evolution in the annealed condition: Above: conventionally cast ingot Below: ESR remelted ingot

31 Comparison NMI conventional route VS remelted material Source: G. Reiter (Böhler special steel), LMPC 2013, Austin Texas

32 Typical Melt Trend in ESR One main objective in ESR is a constant stable remelting rate (given in orange) in order to achieve consistent product quality

33 Surface quality ESR ø1000mm ESR ingot

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35 tons remelted

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37 Typical process route for tool steels

38 World Market This document contains INTECO proprietary information and may not be used or disclosed to others without the expressed written permission of INTECO. Data provided by

39 HSS Powder Production - History Traditional Method 1st Generation 2nd Generation 3rd Generation In the traditional method, pre- The 1st generation is a The 2nd generation is applied The 3rd generation is applied alloyed metal is poured into a development of the traditional for the ERASTEEL ASP and for the BÖHLER UDDEHOLM funnel, acting as a fairly small method to produce powder in DvalinTM process, where a microclean process, where a tundish; no temperature control an atomizing chamber utilizing larger tundish (7 t and 14 t) is larger tundish (approx. 8 t) in and high risks of entrainment of a tundish (approx. 1 t), requiring utilized in combination with combination with INTECO s slag. frequent refilling which leads to Argon stirring and INTECO s ESH and electromagnetic entrainment of slag. electro-slag heating (ESH) stirring system is used, leading system, leading to higher to extremely high powder powder cleanliness with cleanliness, optimized atomi- reduced slag entrainment. zation and closed powder handling.

40 HSS Powder Production - Today MicroClean Process 8 t Tundish & Electromagnetic Stirring & ESH INTECO IHEC Source: Böhler Edelstahl

41 Source: ERASTEEL HSS Powder Production - Today Dvalin TM Process 14 t Tundish & Argon Stirring & ESH with ESH

42 Outlook: General trends in tool steel melting and casting Productivity & yield C C Production costs Automation & mechanisation Product quality Introduce completely new alloy concepts

43 THANK YOU