Nástrojová ocel 9SiCr

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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

C	Si	Mn	Cr	P	S
0.85 – 0.95	1.20 – 1.60	0.30 – 0.60	0.95 – 1.25	≤0,030	≤0,030

2. Physical Properties of 9SiCr Steel

2.1 Critical Point Temperatures

Kritický bod	Ac1	Acₑₘ	Ar₁	paní
Temperature (approx. value) / °C	770	870	730	160

2.2 Other Physical Properties

Density / (g/cm³)	Coercivity / (A/m)	Saturation Magnetic Induction / T
7.80	795.8	1.78 – 1.82

3. Forging Process of 9SiCr Steel

Forging Process Specification

Položka	Teplota ohřevu / °C	Initial Forging Temperature / °C	Final Forging Temperature / °C	Chlazení
Ocelový ingot	1150 – 1200	1100 – 1150	880 – 800	Slow cooling (in sand or pit)
Ocelový předvalek	1100 – 1150	1050 – 1100	850 – 800	Slow cooling (in sand or pit)

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4. Heat Treatment of 9SiCr Steel

4.1 Předehřívání

Preliminary Heat Treatment Plan	Procesní parametry
Post-forging Annealing	Heating 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 Annealing	Heating 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 Tempering	Heating 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.
Normalizace	Heating temperature 900 – 920°C, air cool. Hardness: 321 – 415 HBW. Used to refine the grains of overheated steel and eliminate network carbides.
Kalení a temperování	Heating 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/mm				Phase Composition (Mass Fraction, %)			Microstructure
Before Annealing		After Annealing		Ferrite	Carbide	Carbide Form	Before Annealing	After Annealing
Indentation Diameter/mm	HBW	Indentation Diameter / mm	HBW
3.0 – 3.4	415 – 321	3.9 – 4.3	241 – 197	87.3 – 85.8	12.7 – 14.2	Fe₃C	Troostite + Sorbite	Spheroidite

4.2 Kalení

Plan	Quenching Temp. / °C	Chlazení				Tvrdost HRC
Plan	Quenching Temp. / °C	Coolant	Coolant Temp. / °C	Duration	Cool to room temp	Tvrdost HRC
já	860 – 880	Olej	20 – 40	To oil temperature	Vzduch	62 – 65
II	860 – 880	Olej	80 – 140	To 150 – 200°C	Vzduch	62 – 65
III	860 – 880	Molten nitrate salt or alkali	150 – 200	3 – 5 min	Vzduch	61 – 63
IV	860 – 880	Molten nitrate salt or alkali	150 – 200	30 – 60 min	Vzduch	59 – 62

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

4.3 Cold Treatment Specification

Quenching Plan	Cooling Temperature / °C	Účel	Hardness Increase HRC
I – III	-70	High-precision tools, dimensional stabilization of molds	0 – 1

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

5. Temperování

5.1 Tempering process specifications

Plan	Účel temperování	Teplota ohřevu / °C	Heating Medium	Tvrdost HRC
já	Stress relief, stabilize microstructure	140 – 160	Oil, saltpeter, alkali	62 – 65
		160 – 180		61 – 63
		180 – 200		60 – 62
		200 – 220		58 – 62
II	Stress relief, reduce hardness	Per hardness requirement	Saltpeter, alkali, air furnace	Per the hardness requirement

Notes:

For high-precision (1-2μm) workpieces, tempering (aging) should be performed after rough grinding.
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/°C	100	150	200	250	300	350	400	450	500	600
Tvrdost HRC	64	63	62	60	59	58	55	51	47	40

Poznámka: 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

Teplota	Napětí				Compression	Torsion			Rázová houževnatost	Tvrdost
(°C)	R_eL	R_m	A (%)	Z (%)	Compressive Strength (MPa)	T (N·m)	φ (°)	l (%)	a_KV / （J/ cm 2 ）	HBW
20	456	805	26.2	54.2	3610	155	435	7.7	40	243
200	330	722	21.9	47.7	2660	141	396	6.9	90	218
400	335	635	32	63.4	1830	144	332	6.6	100	213
600	176	207	51.5	76.8	1900	64	1990	32.9	90	172
700	85	100	58	77.2		27	2270	39.5	150	53
750	73	102	59.3	68.4	223				370	44.6
800	67	87	70.6	62.5	265	12	3300	57.4	360	29.3
850	46	67	51	48.3	230				320	33.6
900	42	52	39.7	30.2	265	11.5	2250	39.2	280	22.7
1000	24	30	22	26.7		7.5	935	16.3	222	19
1100	15	20	41.5	53		4	1390	24.2	158	7.4
1200	6	11	87	100					106	4.2
1250	7	9.7	56.5	100					77
1300	6	7	46.5	87

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:

Ražba umírá
Hand reamers
Stříhací čepele
Desky na válcování závitů
Cold rolling rolls
Straightening rolls
Závitové válcovací nástroje
Kreslení umírá
Lisování zemře
Studená hlava umírá

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