What is S7 Tool Steel?

 

In tool steel standard ASTM A681, shock-resisting tool steels are designated as group S steels according to the AISI classification system. S1, S2, S5, S6, and S7 are the types of shock-resisting tool steels. AISI S7 tool steel is a shock-resistant air hardening steel. AISI S7 steel has exceptional impact properties plus the highest hardenability of shock resisting grades of tool steel. Steel S7 also possesses good softening resistance at high temperatures which gives it hot work capabilities. Since S7 steel hardens in air, it is also safe and stable in heat treatment.

Understanding S7 Tool Steel

This document provides an overview of S7 tool steel, a type of shock-resistant tool steel recognized for its unique properties and applications. It discusses the classification, characteristics, and uses of AISI S7 steel, as well as information on sourcing this material.

What is S7 Tool Steel?

In the realm of tool steels, S7 is classified under the ASTM A681 standard as a shock-resisting tool steel, falling into the group S category according to the AISI classification system. The S group includes various types of shock-resisting tool steels, specifically S1, S2, S5, S6, and S7. AISI S7 tool steel is particularly notable for being a shock-resistant air hardening steel.

Properties of AISI S7 Tool Steel

AISI S7 steel is distinguished by its exceptional impact properties and the highest hardenability among the shock-resisting grades of tool steel. This steel also exhibits good softening resistance at elevated temperatures, which enhances its hot work capabilities. One of the key advantages of S7 steel is that it hardens in air, making it a safe and stable option during heat treatment processes.

Applications of S7 Tool Steel

The unique combination of properties found in AISI S7 tool steel makes it suitable for a wide range of tool and die applications. It is particularly valuable in situations where shock-resistance, medium hot-work properties, and ease of machining and heat-treatment are critical factors. This versatility allows S7 steel to be utilized in various industries, including manufacturing and metalworking.

Sourcing S7 Tool Steel

Otai Special Steel is a professional supplier of S7 tool steel materials, offering a variety of products that meet specific technical requirements. The range includes AISI S7 Round Bar, S7 Drill Rod, S7 Rectangular Bar, S7 Flat Bar, S7 Square Bar, and S7 Plate. For more information or to request a quick quote, interested parties are encouraged to reach out at any time.

In conclusion, AISI S7 tool steel stands out for its remarkable properties and adaptability, making it an essential material for many industrial applications.

 

 

 1. Supply Range of AISI S7 Tool Steel

S7 Steel Round Bar: diameter 8mm – 1000mm
S7 Steel Plate: thickness 2mm –600mm x width 200mm – 2200mm
Other sizes of S7 steel per customer’s requirements
Surface Finish: Black, Rough Machined, Turned or as per given requirements.
Process: Hot rolled, Forged, Cold drawn etc.

2. Relevant Steel Specification for S7 Tool Steel

Country	USA	German
Standard	ASTM A681	DIN EN ISO 4957
Grades	S7/T41907	1.2355/50CrMoV13-15

3. AISI S7 Steel Chemical Composition and Steel Equivalents

ASTM A681-2008	C		Si		Mn		P	S	Cr		V		Mo
S7/T41907	0.45	0.55	0.20	1.00	0.20	0.90	0.03	0.03	3.00	3.50	–	0.35	1.30	1.80
DIN ISO 4957	C		Si		Mn		P	S	Cr		V		Mo
1.2355/50CrMoV13-15	0.45	0.55	0.20	0.80	0.50	0.90	0.03	0.02	3.00	3.50	0.15	0.35	1.30	1.70

4. S7 Tool Steel Mechanical Properties

S7 Steels Mechanical Properties

Properties	Metric
Hardness, Rockwell C (air cooled from 941°C, 649°C temper temperature)	41
Hardness, Rockwell C (air cooled from 941°C, 449°C temper temperature)	53
Hardness, Rockwell C (air cooled from 941°C, 149°C temper temperature)	57
Modulus of elasticity	207 GPa
Charpy impact (V-notch; air cooled from 941°C; 425°C temper temperature)	13.6 J
Charpy impact (V-notch; air cooled from 941°C; 649°C temper temperature)	16.3 J
Charpy impact (V-notch; air cooled from 941°C; 200°C temper temperature)	16.9 J
Machinability (1% carbon steel)	70.0 – 75.0%
Poisson’s ratio	0.27-0.30

Tool Steel S7 Physical Properties

Elastic Modulus	207GPa
Density	7.83 g/cm³
Thermal Conductivity	W/m- °K	Cal/cm-s-°C
at 95°C	28.5	0.068
Thermal Properties
Critical Temperature:	800c
CTE, linear 20°C	12.59µm/m- °C
CTE, linear 250°C	13.33µm/m- °C
CTE,linear 500°C	14.27µm/m- °C
Transformation Temperature	785 °C

5. Forging of AISI Steel S7

Preheat 1200°F( 648.9°C ) -1300°F( 704°C ). Forge at 2000°F ( 1093°C ) - 2050°F (1121°C ). Stop at 1700°F and cool slowly.

°C=(°F−32)​/1.8

=(1200F -32 ) /1.8=648.9 ° C

=(1300F -32 ) /1.8=704 ° C

6-AISI S7 Tool Steel Heat Treatment

This document provides a comprehensive overview of the heat treatment processes for AISI S7 tool steel, including annealing, stress relief, hardening, and tempering. Understanding these processes is crucial for achieving optimal mechanical properties and performance in various applications. The following sections detail the specific temperatures, times, and methods required for effective heat treatment of S7 tool steel.

Annealing

To anneal AISI S7 tool steel, follow these steps:

1. Protective Atmosphere: Ensure that the annealing process is conducted in a protective atmosphere to prevent oxidation.

2. Heating: Heat the steel rapidly to a temperature range of 1500°F to 1550°F.

3. Holding Time: Maintain this temperature for one and one-half hours for each inch of the greatest thickness of the material.

4. Cooling: For optimal machining properties, cool the steel slowly to 1000°F, and then allow it to air-cool. This annealing procedure should yield a maximum hardness of Brinell 197.

Stress Relief

When it is necessary to relieve the strains from machining, perform the following:

1. Heating: Heat the S7 steel slowly to a temperature between 1050°F and 1250°F.

2. Equalization: Allow the material to equalize at this temperature.

3. Cooling: Cool the steel in air.

Hardening

The hardening process for AISI S7 tool steel involves several key steps:

1. Preheat: Warm the S7 steel slightly before charging it into the preheat furnace, aiming for a temperature of 1200°F to 1300°F.

2. Harden: Heat the steel to 1750°F.

   • For cross sections of 2-1/2 inches or smaller, quench the steel in still air.

   • For sections between 2-1/2 inches and 6 inches, oil quench to black (1000°F) and then air cool to 150°F.

   • For larger cross sections, oil quench to 150°F.

3. Quenching: Quench in still air or use a dry air blast for cooling.

4. Tempering: S7 tool steel is typically tempered for one hour per inch of section thickness, with a desired heating rate of 2 hours per inch. Cool the steel in air to room temperature between the two tempering processes.

Tempering Temperatures

The tempering temperature will vary based on the intended application:

• Cold-working and Similar Applications: Recommended tempering temperature is between 400°F and 500°F.

• Hot Working Applications: Apply a tempering temperature of 900°F to 1000°F.

• Minimum Tempering Temperature: Never temper at temperatures lower than 400°F.

By adhering to these guidelines, the heat treatment of AISI S7 tool steel can be effectively managed to achieve the desired mechanical properties for various applications.

7. Machinability of Tool Steel S7

When S7 steel annealed to Brinell 197 max, steel S7 is rated at 95, as compared to a rating of 100 for a 1.00 pct carbon tool steel.

8. Applications of ASTM A681 S7 Tool Steel

Because of its unusual combination of properties, S7 tool steel is suitable and versatile for a wide range of tool and die applications. AISI S7 Steel can be used for hot and cold shock applications, medium hot-work dies and medium-run cold work tools and dies.

Other uses include: Bull Riveters, Concrete Breakers (Moll Points), Riveting Dies, Powder Metal Dies, Notching Dies, Dowels, Drills, Drill Plates, Hubs, Plastic Mold Dies, Cold Forming Dies, Blanking Dies, Bending Dies, engraving dies, machined cavities for plastic molding dies, die-casting dies, shear blades and Master Hobs.

Otai special steel offers good price and quality AISI S7 tool steel materials. And we will have S7 steel price promotion sometimes, sign up our price list newsletter to have the latest price of S7 steels.