9SiCr Tool Steel

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9SiCr Tool Steel is a low-alloy tool steel, and its key characteristics come from silicon (Si) and chromium (Cr) being the main alloying elements. The typical chemical composition, by weight percentage (wt%), generally falls within these ranges, although you’ll see slight variations between different standards. The equivalents for 9SiCr steel are DIN 1.2109 / 90SiCr5 in the German standard and AISI L3 in the American standard.

1. Chemical Composition (GB / T 1299—2000) of 9SiCr Steel

CSiMnCrPS
0.85 – 0.951.20 – 1.600.30 – 0.600.95 – 1.25≤0.030≤0.030

2. Physical Properties of 9SiCr Steel

2.1 Critical Point Temperatures

Critical PointAc₁AcₑₘAr₁Ms
Temperature (approx. value) / °C770870730160

2.2 Other Physical Properties

Density / (g/cm³)Coercivity / (A/m)Saturation Magnetic Induction / T
7.80795.81.78 – 1.82

3. Forging Process of 9SiCr Steel

Forging Process Specification

ItemHeating Temperature / °CInitial Forging Temperature / °CFinal Forging Temperature / °CCooling
Steel Ingot1150 – 12001100 – 1150880 – 800Slow cooling (in sand or pit)
Steel Billet1100 – 11501050 – 1100850 – 800Slow cooling (in sand or pit)
9SiCr
9SiCr tool steel

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4. Heat Treatment of 9SiCr Steel

4.1 Preheating

Preliminary Heat Treatment PlanProcess Parameters
Post-forging AnnealingHeating temperature 790 – 810°C, hold for 1-2h; furnace cool to below 550°C then air cool. Hardness after annealing: 197 – 241 HBW.
Post-forging Isothermal AnnealingHeating temperature 790 – 810°C, hold for 1-2h; isothermal temperature 700 – 720°C, furnace cool to below 550°C then air cool. Hardness: 197 – 241 HBW.
High-temperature TemperingHeating temperature 600 – 700°C, hold for 2-4h; furnace cool or air cool. Hardness: 197 – 241 HBW. Used to eliminate work hardening from cold deformation.
NormalizingHeating temperature 900 – 920°C, air cool. Hardness: 321 – 415 HBW. Used to refine the grains of overheated steel and eliminate network carbides.
Quenching and TemperingHeating temperature 880 – 900°C, tempering temperature 680 – 700°C, hold for 2-4h; furnace cool or air cool. Hardness: 197 – 241 HBW.

Hardness and Microstructure Before and After Annealing

Indentation Diameter/mmPhase Composition (Mass Fraction, %)Microstructure
Before AnnealingAfter AnnealingFerriteCarbideCarbide FormBefore AnnealingAfter Annealing
Indentation Diameter/mmHBWIndentation Diameter / mmHBW
3.0 – 3.4415 – 3213.9 – 4.3241 – 19787.3 – 85.812.7 – 14.2Fe₃CTroostite + SorbiteSpheroidite

4.2 Quenching

PlanQuenching Temp. / °CCoolingHardness HRC
CoolantCoolant Temp. / °CDurationCool to room temp
I860 – 880Oil20 – 40To oil temperatureAir62 – 65
II860 – 880Oil80 – 140To 150 – 200°CAir62 – 65
III860 – 880Molten nitrate salt or alkali150 – 2003 – 5 minAir61 – 63
IV860 – 880Molten nitrate salt or alkali150 – 20030 – 60 minAir59 – 62

Note: For workpieces with complex shapes and small deformation requirements, use plans III and IV.

4.3 Cold Treatment Specification

Quenching PlanCooling Temperature / °CPurposeHardness Increase HRC
I – III-70High-precision tools, dimensional stabilization of molds0 – 1

Note: Cold treatment should be carried out within 1 hour after quenching.

5. Tempering

5.1 Tempering process specifications

PlanPurpose of TemperingHeating Temperature / °CHeating MediumHardness HRC
IStress relief, stabilize microstructure140 – 160Oil, saltpeter, alkali62 – 65
160 – 18061 – 63
180 – 20060 – 62
200 – 22058 – 62
IIStress relief, reduce hardnessPer hardness requirementSaltpeter, alkali, air furnacePer the hardness requirement

Notes:

  1. For high-precision (1-2μm) workpieces, tempering (aging) should be performed after rough grinding.
  2. For tempering above 250°C, the dimensional stability of the workpiece can be guaranteed without cold treatment.

5.2 Relationship between tempering temperature and hardness

Tempering Temperature/°C100150200250300350400450500600
Hardness HRC64636260595855514740

Note: 870°C oil quenching, tempering for 2h.

6. Mechanical Properties

9SiCr steel contains Si and Cr elements, giving it high hardenability, quenching hardness, and high resistance to tempering. This is beneficial for improving wear resistance and resistance to plastic deformation. When tempered at 300-400°C, the hardness can be maintained at around 60 HRC, exhibiting good wear resistance and toughness. However, this steel is prone to decarburization, and measures should be taken to prevent oxidative decarburization during quench heating.

Mechanical Properties of 9SiCr Steel at Different Temperatures

TemperatureTensionCompressionTorsionImpact ToughnessHardness
(°C)ReLRmA (%)Z (%)Compressive Strength (MPa)T (N·m)φ (°)l (%)aKV
/ （J/ cm
2
）		HBW
2045680526.254.236101554357.740243
20033072221.947.726601413966.990218
4003356353263.418301443326.6100213
60017620751.576.8190064199032.990172
700851005877.227227039.515053
7507310259.368.422337044.6
800678770.662.526512330057.436029.3
85046675148.323032033.6
900425239.730.226511.5225039.228022.7
100024302226.77.593516.322219
1100152041.5534139024.21587.4
1200611871001064.2
125079.756.510077
13006746.587

7. Applications

9SiCr steel is a low-alloy tool steel. It has high hardenability and tempering resistance, and is suitable for martempering or austempering. It is commonly used to manufacture high-speed cutting tools with high wear resistance requirements and cold work dies with complex shapes, small deformation requirements, and high wear resistance, such as:

  • Coining dies
  • Hand reamers
  • Shear blades
  • Thread rolling plates
  • Cold rolling rolls
  • Straightening rolls
  • Thread rolling dies
  • Drawing dies
  • Stamping dies
  • Cold heading dies

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