440C Tool Steel | 1.4125 | X105CrMo17

440C Stainless Steel | 1.4125 | X105CrMo17 Product Introduction

440C Stainless Steel (American Standard AISI/SAE)

The chemical composition of 440C is carbon (0.95%-1.20%), chromium (16.00%-18.00%), and molybdenum (≤0.75%), supplemented by the limiting elements silicon (≤1.00%) and manganese (≤1.00%). After quenching (1010-1070°C oil-cooled) and low-temperature tempering (100-300°C), the hardness can reach HRC 58-62, tensile strength 560-1000 MPa, elongation 15%-18%.
The metallographic organisation of the material is typical martensite, with magnetic properties and moderate corrosion resistance, stable in mild corrosive environments, but prone to pitting corrosion in chloride or strong acid environments. Its high temperature dimensional stability is good, but it is weak to withstand dynamic loads.

1.4125 Stainless Steel (DIN)

The chemical composition of 1.4125 is identical to that of 440C: carbon (0.95%-1.10%), chromium (16.00%-18.00%). Physical parameters include a density of 7.7-7.78 g/cm³, a modulus of elasticity of 200-215 GPa, and a coefficient of thermal expansion (20-100°C) of 10.2-11.6×10-⁶/K. Heat treatment is subject to 980 -1070°C oil quenching and 200-300°C tempering, the hardness can be increased to HRC 55-60, yield strength ≥ 440 MPa, tensile strength ≥ 690 MPa.
material shows high wear resistance and martensitic phase transition properties, corrosion resistance in oxidising media (e.g. dilute nitric acid) The corrosion resistance is good in oxidising media (e.g. dilute nitric acid) (corrosion rate <0.1 mm/a), but decreases significantly in reducing acids (e.g. hydrochloric acid) (>10.0 mm/a). Its hardness in the annealed state is ≤225 HBS, and after quenching it is necessary to avoid welding to prevent cracking.

X105CrMo17 Stainless Steel (EN)

X105CrMo17 has a composition of carbon (0.95%-1.10%) and chromium (16.00%-18.00%), which is highly overlapping with 440C and 1.4125, with only a slightly higher upper limit of carbon content. Heat treatment is 1070°C oil quenching + 200-300°C tempering, hardness up to HRC 54-60, bending fatigue strength at 961 N stress of 6.3 × 10⁴-8.4 × 10⁴ times cycles.
The material has a martensitic organisation reinforced with high-carbon chromium-molybdenum, and its corrosion resistance is stable (corrosion depth <1.0 mm/a) in nitric acid (concentration ≤20%), but deteriorates sharply with increasing concentration and temperature in acetic or phosphoric acid environments. Its thermal stability remains good up to 400°C, but there is no significant increase in thermal conductivity at high temperatures.

440C Stainless Steel | 1.4125 | X105CrMo17 Types and Options

The table below shows the size range, surface condition and tolerance details for 1.4125,X105CrMo17, 440C Stainless Steel:

Shape	Pocess	Size range	Surface	Tolerance
Flat Bar	Hot Rolled	Thickness: 10-400mm Width: 200-800mm Length: 3000-5800mm	Black; Sandblasted	Thickness :0-+2MM Width:0-+5MM/0-+10MM
	Hot Forged	Thickness: 50-500mm Width: 50-1500mm Length: 3000-5800mm	Black	Thickness:+2-+5MM Width:0-+5MM/0-+10MM
			Turned/Machined/Milled/Bright	Thickness :0-+2MM Width:0-+5MM/0-+10MM
Round Bar	Hot Rolled	Diameter:10-65mm Length:3000-5800mm	Black	0-+2MM
			Turned/Machined	0-+2MM
	Hot Forged	Diameter:70-700mm Length:3000-5800mm	Grinded	0-+5MM/+2-+5MM
			Turned/Machined/Milled/Bright	0-+2MM

440C Stainless Steel | 1.4125 | X105CrMo17 Customized Options

1. Customized chemical composition: GB, DIN, ASTM, JIS and other standard grades can be produced. Chemical composition can be customized individually.
2. Customized specifications: round steel (diameter), plate (thickness, width) can be customized production.
3. Specialized packaging for long term storage or extreme transportation conditions: includes spraying black paint all around, wrapping plastic film, spraying anti-rust oil, and shipping in wooden crates.
4. Customized production based on samples or technical agreements.
5. 440C,1.4125,X105CrMo17 Stainless Steel Electroslag Remelting (ESR): premium option with higher purity and isotropic properties for critical applications.

440C Stainless Steel | 1.4125 | X105CrMo17 Chemical Composition

Standard/Steel Grade		Chemical Composition(%)
		C	Si	Mn	Cr	Mo	V
ASTM	440C	0.95~1.20	≤1.00	≤1.00	16.00~18.00	≤0.75	-
GB	9Cr18Mo	0.95~1.10	≤0.80	≤0.80	16.00~18.00	-	0.40~0.70

440C Stainless Steel | 1.4125 | X105CrMo17 Heat Treatment Process

1.Annealing

Purpose: to eliminate internal stresses generated during forging or rolling, reduce hardness, improve cutting performance, and prepare for subsequent processing and heat treatment.
Process parameters:
Heating temperature: 800-850 ℃, holding time 2-4 hours, with the furnace cooling to below 500 ℃, and then air-cooled.
Hardness after annealing: ≤ 225 HBS.

2.Quenching

Purpose: to make the tool steel to obtain martensitic organization, improve hardness and wear resistance.
Process parameters:
Heating temperature: 1000-1050 ℃ (commonly used 1020-1040 ℃), holding time according to the size of the workpiece to determine, generally 30-60 minutes.
Cooling: oil cooling or air cooling (for small size or simple shape of the workpiece), large workpieces can be graded quenching (in the 260-300 ℃ salt bath cooling for a period of time and then air-cooled), in order to reduce the quenching stress, to prevent deformation and cracking.

3.Tempering

Purpose: to eliminate quenching stress, adjust the hardness and toughness, stable organization and size.
Process parameters:
low-temperature tempering: 150-250 ℃, insulation 2-3 hours, air-cooled, tempered hardness of 58-62HRC, for molds requiring high hardness and wear resistance.
Medium temperature tempering: 300-500 ℃, insulation 2-3 hours, air-cooled, tempered hardness of 50-58HRC, can improve the toughness, suitable for molds subject to impact load.
High-temperature tempering: 500 ℃ or more, insulation 2-3 hours, air-cooled, tempered hardness 45-50HRC, mainly for the need for higher toughness of the occasion.

4.Precautions

Heating process should control the rate of heating to avoid too rapid a rise in temperature leading to workpiece surface oxidation and decarburization. Protective atmosphere heating can be used or placed in the furnace charcoal and other anti-decarburization agent.
When quenching and cooling, choose the appropriate cooling medium and cooling method according to the shape and size of the workpiece to ensure the quenching effect while reducing the risk of deformation and cracking.
Tempering must be sufficient to ensure the elimination of internal stresses to avoid mold failure due to stress release during use. For large molds or workpieces with complex shapes, multiple tempering can be used.

440C Stainless Steel | 1.4125 | X105CrMo17 Quality Inspection

1.Surface Condition Inspection

FCS factory has a very strict quality inspection team, we will carefully check the surface condition of each piece of tool steel to ensure that the steel surface is free from cracks, folds, knots, oxidized skin, pitting, scratches and other defects.

2.Chemical Composition Testing

To verify whether the content of alloying elements meets the standard requirements and to safeguard the basis of the mechanical properties of the material. We will let the staff use full-spectrum direct reading spectrometer to analyze multiple elements at the same time. Sampling needs to remove the surface oxidation layer, using a block specimen to stimulate the test.

3.Dimension and Tolerance Inspection

FCS factory will use professional measuring tools to inspect the dimensions and tolerances of the steel to ensure compliance with the customer's contract requirements. Corresponding gauges will be selected according to the dimensional accuracy requirements, including tape measure, high-precision vernier calipers (0.02mm), micrometers (0.001mm), and special inspection gauges. Inspection items cover: diameter, thickness, width, length, hole diameter, chamfering dimensions, etc., to ensure that the tolerances and dimensions meet the contract requirements.

4.Hardness test

Our FCS factory will use professional hardness tester to test the hardness of steel to ensure that it meets the customer's contract requirements.

5.Ultrasonic Testing

Ultrasonic Testing Standard (UT Test Standard) is: Sep 1921-84 Class3 D/d,E/e.
FCS factory uses ultrasonic testing equipment to detect macro defects inside the material (such as cracks, shrinkage holes, inclusions, white spots, etc.), and every piece of round steel and plate will be examined by a second flaw detection test before shipment to ensure that the quality is qualified before shipment.

6.Microstructure Inspection

(1) Metallographic Analysis

FCS factory will use metallographic analysis instrument to detect the microstructure state after heat treatment, including carbide distribution, martensite morphology, residual austenite content, etc.

 (2) Grain size rating

FCS factory will use the comparative method to determine the austenite grain size by comparing the microstructure of the specimen with the standard rating chart, to ensure that it meets the customer's requirements.

440C Tool Steel | 1.4125 | X105CrMo17 Technical Specifications

Property	Value for 440C/1.4125/X105CrMo17	Unit / Standard
Density	7.65	g/cm³
Melting Point	1421-1510	°C
Thermal Conductivity	24.2	W/(m·K)
Specific Heat Capacity	460	J/(kg·K)
Electrical Resistivity	0.60	μΩ·m
Magnetic Permeability	Ferromagnetic	-
Elastic Modulus	200	GPa
Tensile Strength (Annealed)	760	MPa
Tensile Strength (Hardened)	1900-2200	MPa
Yield Strength (Hardened)	1650-1900	MPa
Elongation at Break	2-3	%
Reduction of Area	5-10	%
Impact Toughness	14-20	J

440C Tool Steel | 1.4125 | X105CrMo17 Product Applications

Key usage scenarios

Aerospace Precision Ball Bearings

Our 440C stainless steel is the material of choice for critical aerospace bearings where reliability is essential. In high-altitude environmental conditions, conventional bearing materials often fail prematurely due to accelerated corrosion. 440C's unique combination of hardness and corrosion resistance allows bearing designs to maintain precision tolerances over thousands of hours of fluctuating temperature and humidity conditions. These bearings typically last 30-45% longer than standard chrome steel bearings in the same applications.

Surgical Instruments and Medical Devices

Medical device manufacturers rely on our 1.4125 stainless steel for high-end surgical instruments that require superior edge retention and corrosion resistance. The material's ability to maintain a sharp cutting edge while withstanding repeated sterilisation cycles makes it ideal for precision surgical tools. Our specially machined medical-grade variants undergo additional testing to ensure biocompatibility and meet stringent cleanliness requirements, allowing surgeons to rely on these instruments to maintain consistent performance over hundreds of surgeries.

High-performance valve components

Industrial valve systems operating in harsh environments benefit from the wear and corrosion resistance of X105CrMo17 components. Seats, balls and stems made from our material maintain sealing integrity when handling abrasive media or corrosive chemicals. Case studies have shown that upgrading from standard stainless steel parts to our high-carbon martensitic stainless steel options results in maintenance intervals being extended by 40-60%, directly reducing downtime and maintenance costs in critical industrial processes.

Precision Cutting Tools and Inserts

Our 440C grade material is widely used in high performance industrial cutting tools and inserts where edge retention is critical. The combination of high hardness and reasonable toughness makes it suitable for slitting blades, industrial shears and precision cutting instruments. Manufacturers report sharpening or replacement intervals that are 3-5 times longer than lower-grade stainless steel options, significantly increasing productivity and reducing operating costs.

Industry-Specific Applications

1. Aerospace: control mechanism components: landing gear bearings and bushings; hydraulic system valve components; fasteners for critical structural applications; instrumentation components.
2. Medical & Pharmaceutical: Surgical cutting instruments; endoscopic equipment; dental instruments; medical implant parts (temporary); laboratory test equipment;
3. Food Processing: Highly abrasion-resistant cutting blades; industrial mixer components; abrasive media pump components; nozzles and sprays; precision measuring instruments.
4. Oil & Gas: Downhole Tool Parts; Valve Seats & Stems; Sensor Housings; Pump Plungers & Components; Throttle Parts
   Automotive Transportation: Fuel Injection Parts; ABS System Parts; Bearing Rings & Balls; Valve Train Parts; Specialty Fasteners.

440C Tool Steel | 1.4125 | X105CrMo17 Competitive Advantage Comparison

Performance	440C/1.4125 Steel from FCS Factory	Standard Martensitic Stainless Steel	Carbon Tool Steel	Description
Corrosion Resistance	Excellent	Good	Poor	Better protection in humid environments
Edge Retention	Excellent	Good	Excellent	Maintains cutting edge 3-4 times longer than standard stainless steel
Dimensional Stability	Very Good	Good	Excellent	Minimal distortion after heat treatment
Wear Resistance	Excellent	Good	Excellent	Significantly longer service life than standard stainless steel under abrasive conditions
Toughness	Medium	Medium-Good	Poor-Medium	Balanced performance with a wide range of applications
Material Consistency	Excellent	Unstable	Unstable	Strict quality control ensures consistency between batches
Heat Treatment Response	Excellent	Good	Excellent	Hardening characteristics are predictable and repeatable
Machinability (Annealed State)	45%	50-55%	30-40%	Good balance between machinability and performance

440C Tool Steel | 1.4125 | X105CrMo17 Customer Success Stories

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440C Tool Steel | 1.4125 | X105CrMo17 Pricing Structure Information

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440C Tool Steel | 1.4125 | X105CrMo17 Frequently Asked Questions

Q: How does 440C/1.4125/X105CrMo17 compare to other martensitic stainless steels such as 420 or 431?
A: 440C has a significantly higher carbon content (0.95-1.20 per cent compared to 0.15-0.40 per cent for 420), which results in higher hardness and wear resistance after heat treatment. The higher chromium content also provides better corrosion resistance than 420. Compared to 431, 440C offers superior wear resistance and slightly better corrosion resistance, but is slightly less tough.

Q: How does 440C compare to D2 tool steel in cutting applications?
A: 440C offers approximately 80-85% of the wear resistance of D2 tool steel while providing significantly better corrosion resistance. For applications where both properties are required, 440C generally provides a better balance. When the only consideration is maximum wear resistance, D2 may be preferred.

Q: What heat treatment is recommended to obtain maximum hardness?
A: Optimum heat treatments include austenitising at 1010-1065°C (1850-1950°F), quenching in oil, and then tempering at 150-180°C (300-350°F). For maximum dimensional stability, a triple tempering process is recommended, usually with deep cooling between the first and second tempering cycles.

Q: Is this material magnetic?
A: Yes, 440C/1.4125/X105CrMo17 is ferromagnetic in both the annealed and hardened states and is suitable for applications where magnetism is required.