DIEVAR UDDEHOLM DIEVAR

Transcription

1 UDDEHOLM

2 REFERENCE STANDARD AISI WNr. JIS ASSAB DF-2 ARNE O1 ( (SKS 3 ASSAB DF-3 O1 ( (SKS 3 ASSAB XW-5 SVERKER 3 D6 (D3 ( (SKD 2 ASSAB XW-10 RIGOR A SKD 12 ASSAB XW-41 SVERKER 21 D SKD 11 ASSAB XW-42 D SKD 11 CARMO CARMO CALMAX CALMAX CALDIE ASSAB 88 CALDIE SLEIPNER ASSAB PM 23 SUPERCLEAN VANADIS 23 SUPERCLEAN (M3: SKH 53 ASSAB PM 30 SUPERCLEAN VANADIS 30 SUPERCLEAN (M3:2 + Co SKH 40 ASSAB PM 60 SUPERCLEAN VANADIS 60 SUPERCLEAN ( VANADIS 4 EXTRA SUPERCLEAN VANADIS 6 SUPERCLEAN VANADIS 10 SUPERCLEAN VANCRON 40 SUPERCLEAN ELMAX SUPERCLEAN VANADIS 4 EXTRA SUPERCLEAN VANADIS 6 SUPERCLEAN VANADIS 10 SUPERCLEAN VANCRON 40 SUPERCLEAN ELMAX SUPERCLEAN ASSAB 518 P ASSAB 618 P20 Mod ASSAB 618 HH P20 Mod ASSAB 618 T P20 Mod Mod. ASSAB 718 SUPREME IMPAX SUPREME P20 Mod ASSAB 718 HH IMPAX HH P20 Mod NIMAX NIMAX MIRRAX 40 MIRRAX Mod. VIDAR 1 ESR VIDAR 1 ESR H SKD 6 UNIMAX CORRAX UNIMAX CORRAX ASSAB SUS 420J2 STAVAX ESR STAVAX ESR 420 Mod ESR SUS 420J2 MIRRAX ESR MIRRAX ESR 420 Mod. POLMAX POLMAX RAMAX HH RAMAX HH 420 F Mod. ROYALLOY ROYALLOY PRODAX ASSAB MM40 ALVAR 14 ALVAR SKT 4 ASSAB SKT 4 ASSAB M ORVAR 2M H SKD 61 ASSAB 8407 SUPREME ORVAR SUPREME H13 Premium ESR SKD 61 HOTVAR QRO 90 SUPREME HOTVAR QRO 90 SUPREME ASSAB SNCM8 ASSAB SCM4 ASSAB S50C ASSAB is a trademark of ASSAB Pacific Pte Ltd. The information contained herein is based on our present state of knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as a warranty of specific properties of the products described or a warranty for fitness for a particular purpose. Each user of ASSAB products is responsible for making its own determination as to the suitability of ASSAB products and services. Edition D

3 Dievar is a hot work die steel specially developed by Uddeholm Tooling, our steel mill in Sweden, to provide the best possible performance. The chemical composition and the very latest in production technique make the property profile outstanding. Dievar possesses a combination of excellent toughness and very good hot strength, resulting in a superior hot work die steel that have excellent resistance to heat checking and gross cracking. Dievar is suitable for high demand hot work applications like die casting, extrusion and forging. The property profile also makes it a suitable choice in other applications such as plastic moulding (e.g., to solve chipping/ cracking and High Performance Steel. Dievar offers the potential for significant improvements in die life, thereby improving the tooling economy. 3

4 General Dievar is a high performance chromium-molybdenumvanadium alloyed hot work tool steel which offers a very good resistance to heat checking, gross cracking, hot wear and plastic deformation. Dievar is characterised by: DIE CASTING Excellent toughness and ductility in all directions Good temper resistance Good high-temperature strength Excellent hardenability Good dimensional stability throughout heat treatment and coating operations Type Cr-Mo-V alloyed hot work tool steel Standard specification None Part Aluminium / Magnesium alloys Delivery condition Soft annealed to approx. 160 HB Dies HRC Colour code Yellow / Grey EXTRUSION Dievar is a premium hot work tool steel developed by Uddeholm. It is manufactured utilising the very latest in production and refining techniques. The Dievar development has yielded a die steel with the ultimate resistance to heat checking, gross cracking, hot wear and plastic deformation. The unique properties profile of Dievar makes it the best choice for die casting, forging and extrusion. Applications Part Copper alloys Aluminium / Magnesium alloys Dies HRC Heat checking is one of the most common failure mechanisms, e.g., in die casting and nowadays also in forging applications. Dievar s superior ductility yields the highest possible level of heat checking resistance. With Dievar s outstanding toughness and hardenability, its resistance to heat checking will be further improved. If gross cracking is not a factor, then a higher working hardness can be utilised (+2 HRC. Regardless of the dominant failure mechanism (e.g., heat checking, gross cracking, hot wear or plastic deformation, Dievar offers the potential for significant improvements in die life as well as tooling economy. Dievar is the material of choice for the high demand die casting, forging and extrusion industries. Liners, dummy blocks, stems HOT FORGING Part Inserts HRC HRC Steel / Aluminium HRC 4

5 Properties The reported properties are representative of samples which have been taken from the centre of a 610 x 203 mm bar. Unless otherwise indicated, all specimens were hardened at 1025 C, quenched in oil and tempered hours at 615 C to 45±1 HRC. PHYSICAL PROPERTIES Hardened and tempered to HRC. Temperature 20 C 400 C 600 C Density kg/m At a hardness of approximately 45 HRC, the minimum average unnotched impact ductility is 300 J in the short transverse direction. Charpy V-notch impact toughness at elevated temperatures Short transverse direction. Impact energy, J HRC Modulus of elasticity MPa HRC Coefficient of thermal expansion per C from 20 C x x Thermal conductivity W/m C HRC C Testing temperature MECHANICAL PROPERTIES Approximate tensile properties at room temperature, tested in the short transverse direction. Hardness 44 HRC 48 HRC 52 HRC Temper resistance The specimens have been hardened and tempered to 45 HRC, and then held at different temperatures from 1 to 100 hours. Tensile strength, R m 1480 MPa 1640 MPa 1900 MPa Yield strength, R P MPa 1380 MPa 1560 MPa Elongation, A 5 13 % 13 % 12.5 % Hardness, HRC C 500 C Reduction of area, Z 55 % 55 % 52 % 40 Approximate tensile properties at elevated temperatures Short transverse direction, 45±1 HRC C 600 C Rm, Rp0.2 MPa Z A5, Z % Time, h Rm Rp A ºC Testing temperature 5

6 Heat treatment SOFT ANNEALING Protect the steel and heat through to 850 C. Then cool in the furnace at 10 C per hour to 650 C, then freely in air. STRESS RELIEVING After rough machining, the tool should be heated through to 650 C, holding time 2 hours. Cool slowly to 500 C, then freely in air. HARDENING Preheating temperature: C. Normally a minimum of two preheats, the first in the C range, and the second in the C range. When three preheats are used, the second is carried out at 820 C, and the third at 900 C. Austenitising temperature: C QUENCHING As a general rule, quench rates should be as rapid as possible. Accelerated quench rates are required to optimise tool properties specifically with regards to toughness and resistance to gross cracking. However, risk of excessive distortion and cracking must be considered. The quenching media should be capable of creating a fully hardened microstructure. Different quench rates for Dievar are defined by the CCT graph as shown in page 7. High speed gas/circulating atmosphere Vacuum (high speed gas with sufficient positive pressure. An interrupted quench at C is recommended for distortion control, or when quench cracking is a concern. Martempering bath, salt bath or fluidised bed at C Martempering bath, salt bath or fluidised bed at approx C Warm oil, approx. 80 C Note: Temper the tool as soon as its temperature reaches C. Temperature C Soaking time minutes Hardness before tempering ±2 HRC ±2 HRC Soaking time = time at hardening temperature after the tool is fully heated through. Protect the tool against decarburisation and oxidation during austenitising. Hardness, grain size and retained austenite as functions of austenitising temperature Grain size ASTM Hardness, HRC Retained austenite % Grain size 8 58 TEMPERING Choose the tempering temperature according to the hardness required by reference to the tempering graph below. Temper at least three times for die casting dies, and two times for forging and extrusion tools. The tool should be cooled to room temperature between the tempers. The minimum holding time at tempering temperature is 2 hours. Tempering in the range of C is normally not recommended, and it will result in a lower toughness. Tempering graph Hardness, HRC Retained austenite, % 60 Austenitising temperature 1025 C C Temper 6 56 Hardness Retained austenite 2 30 Retained austenite C Austenitising temperture C Tempering temperature (2 + 2h 6

7 Effect of tempering temperature on room temperature Charpy V-notch impact energy Short transverse direction. Impact strength Temper brittleness zone Hardness HRC DIMENSIONAL CHANGES DURING HARDENING AND TEMPERING During hardening and tempering, the tool is exposed to both thermal and transformation stresses. These stresses will result in distortion. Insufficient levels of machine stock may result in slower than recommended quench rates during heat treatment. To reduce the level of distortion, a stress relief is always recommended bewteen rough and semi-finish machining, prior to hardening. For a stress relieved Dievar tool, a minimum machining allowance of 0.3% is recommended to correct for distortion during heat treatment with a rapid quench C Tempering temperature (2h + 2h CCT graph Austenitising temperature 1025 C. Holding time 30 minutes. C Austenitising temperature 1025ºC Holding time 30 minutes 900 A C1f = 890ºC Carbides Pearlite A C1s = 820ºC Cooling Hardness Curve No. HV 10 T (sec M S Martensite M f Bainite Seconds Minutes Hours Air cooling of bars, Ømm 7

8 Machining recommendations The cutting data below are to be considered as guiding values and as starting points for developing your own best practice. MILLING Face and square shoulder milling Condition: Soft annealed condition ~160 HB TURNING Cutting data parameters Rough milling Milling with carbide Fine milling Cutting data parameters Cutting speed (v c Feed (f mm/r Depth of cut (a p mm Turning with cabide Rough turning Fine turning Turning with HSS Fine turning Cutting speed (v c Feed (f z mm/tooth Depth of cut (a p mm Carbide designation ISO P20 - P40 Coated carbide P10 Coated carbide or cermet Carbide designation ISO P20 - P30 Coated carbide P10 Coated carbide or cermet - End milling High speed steel DRILLING High speed steel twist drill Drill diameter mm Cutting speed (v c Feed (f mm/r * Cutting data parameters Cutting speed (v c Feed (f mm/tooth Solid carbide Type of milling Carbide indexable insert High speed steel * * * Carbide designation ISO 1 For coated HSS end mill, v c ~ P20 - P30 - * For coated HSS drill, v c ~ GRINDING Carbide drill Wheel recommendation Cutting data parameters Cutting speed (v c Indexable insert Type of drill Solid carbide Brazed carbide Type of grinding Face grinding straight wheel Face grinding segments Cylindrical grinding Grinding wheel designation A 46 HV A 24 GV A 46 LV Feed (f mm/r 1 Drill with replaceable or brazed carbide tip 2 Depending on drill diameter Internal grinding Profile grinding A 46 JV A 100 LV 8

9 Machining recommendations The cutting data below are to be considered as guiding values and as starting points for developing your own best practice. MILLING Face and square shoulder milling Condition: Hardened and tempered to 45±1 HRC TURNING Cutting data parameters Rough milling Milling with carbide Fine milling Cutting data parameters Rough turning Turning with carbide Fine turning Cutting speed (v c Cutting speed (v c Feed (f z mm/tooth Feed (f mm/r Depth of cut (a p mm Depth of cut (a p mm Carbide designation ISO P20 - P30 Coated carbide P10 Coated carbide or cermet Carbide designation ISO P20 - P40 Coated carbide P10 Coated carbide or cermet End milling Type of milling DRILLING High speed steel twist drill (TiCN coated Cutting data parameters Solid carbide Carbide indexable insert High speed steel TiCN coated Drill diameter mm Cutting speed (v c Feed (f mm/r Cutting speed (v c Feed (f mm/tooth Carbide designation ISO P10 - P20-1 Depending on radial depth of cut and cutter diameter GRINDING Carbide drill Wheel recommendation Cutting data parameters Indexable insert Type of drill Solid carbide Brazed carbide 1 Type of grinding Face grinding straight wheel Grinding wheel designation A 46 HV Cutting speed (v c Face grinding segments Cylindrical grinding A 36 GV A 60 KV Feed (f mm/r 1 Drill with replaceable or brazed carbide tip 2 Depending on drill diameter Internal grinding Profile grinding A 60 IV A 120 JV 9

10 Surface treatment NITRIDING AND NITROCARBURISING Nitriding and nitrocarburising result in a hard surface layer which has the potential to improve resistance to wear and soldering, as well as resistance to premature heat checking. Dievar can be nitrided using gas or plasma. It can also be nitrocarburised via gas or salt bath process. The nitriding and nitrocarburising temperature should be at least C below the highest previous tempering temperature, depending upon the process time and temperature. Otherwise, a permanent loss of core hardness, strength, and/or dimensional tolerances may be experienced. During nitriding and nitrocarburising, a brittle compound layer, known as the white layer, may be generated. The white layer is very brittle and may result in cracking or spalling when exposed to heavy mechanical or thermal loads. As a general rule, the white layer formation must be avoided. Depth of nitriding Process Gas nitriding at 510 C Plasma nitriding at 480 C Nitrocarburising in gas at 580 C in salt bath at 580 C Time h Surface hardness HV Depth* mm * Depth of case = distance from surface where hardness is 50 HV 0.2 over base hardness Electrical discharge machining Following the EDM process, the applicable die surfaces are covered with a resolidified layer (white layer and a rehardened and untempered layer, both of which are very brittle and hence detrimental to die performance. If EDM is used, the white layer must be completely removed by grinding or stoning. After finish machining, the tool should be given an additional temper at approx. 25 C below the highest previous tempering temperature. Nitriding in ammonia gas at 510 C, or plasma nitriding at 480 C, both result in a surface hardness of approx HV 0.2. In general, plasma nitriding is the preferred method because of better control over nitrogen potential. However, careful gas nitriding can give perfectly acceptable results. The surface hardness after nitrocarburising in either gas or salt bath at 580 C is approx HV

11 Welding Welding of die components can be performed, with acceptable results, as long as proper precautions are taken during the preparation of the joint, the filler material selection, the preheating of the die, the controlled cooling of the die and the post weld heat treatment processes. The following guidelines summarise the most important welding process parameters. Further information For further information, i.e., steel selection, heat treatment, application and availability, please contact our ASSAB office nearest to you. Welding method TIG MMA Working temp ºC ºC Filler material QRO 90 TIG-WELD TIG-WELD QRO 90 WELD Maximum interpass 475 C 475 C temp. 2 Cooling rate 20-40ºC/h for the first 2 to 3 hours and then freely in air Hardness after welding HRC HRC Heat treatment after welding Hardened condition Soft annealed condition Temper at 25 C below the original tempering temperature. Soft anneal the material at 850 C in protected atmosphere. Then cool in the furnace at 10 C per hour to 600 C, then freely in air. 1 Preheating temperature must be established throughout the die and must be maintained for the entire welding process, to prevent weld cracking 2 The temperature of the tool in the weld area immediately before the second and subsequent pass of a multiple pass weld. When exceeded, there is a risk of distortion of the tool or soft zones around the weld. 11

12 Relative comparison of ASSAB hot work die steels QUALITATIVE COMPARISON OF CRITICAL DIE STEEL PROPERTIES ASSAB grade Temper resistance Hot yield strength Creep strength Coefficient of thermal expansion Heat conductivity Ductility ALVAR 14 ASSAB M ASSAB 8407 SUPREME HOTVAR QRO 90 SUPREME QUALITATIVE COMPARISON OF RESISTANCE TO DIFFERENT DIE FAILURES ASSAB grade Heat checking Gross cracking Hot wear / Erosion Plastic deformation Corrosion (Al ALVAR 14 ASSAB M ASSAB 8407 SUPREME HOTVAR QRO 90 SUPREME 12

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14 Case study RESISTANCE TO HEAT CHECKING Product : Automotive housing Work material : A380 Aluminium alloy Work temp. : 690 C Tooling size : 406 x 508 x 508 mm Die material : Premium H13 at HRC vs HRC Background : Severe heat checking begins on Premium H13 at approximately 20,000 shots. The customer wanted better die life. Premium H13 Comparison of Premium H13 and after 42,000 shots. Premium H13 14

15 Ningbo ASSAB Tooling Technology (Ningbo Co., Ltd. Tel : Fax: info.ningbo@assab.com Cikarang* PT. ASSAB Steels Indonesia Tel : Fax: / info.cikarang@assab.com MALAYSIA Kuala Lumpur - Head Office ASSAB Steels (Malaysia Sdn. Bhd. Tel : Fax: /55 info.kualalumpur@assab.com Tel : Jiangxi* ASSAB Tooling (Dong Guan Co, Ltd., Jiangxi Branch Tel : Fax : info.jiangxi@assab.com 15

16 Choosing the right steel is of vital importance. ASSAB engineers and metallurgists are always ready to assist you in your choice of the optimum steel grade and the best treatment for each application. ASSAB not only supplies steel products with superior quality, we offer state-of-the-art machining, heat treatment and surface treatment services to enhance steel properties to meet your requirement in the shortest lead time. Using holistic approach as a one-stop solution provider, we are more than just another tool steel supplier. ASSAB and Uddeholm are present on every continent. This ensures you that high-quality tool steels and local support are available wherever you are. Together we secure our position as the world's leading supplier of tooling materials. For more information, please visit