Use of the hot work tool steels is ideal when the surface temperature of the tool is very high, approximately 350 to 700°C, while cold work tool steel is ideal for low temperatures (Approximately 200C to 400C).
Cold Work Tool Steel
Cold work steel contains higher carbon content. It contains alloys like manganese, tungsten, molybdenum and chromium. The function of the added alloys is to increase the hardness of the steel. Compared to the W Series of quenching oil distortion is less in this type of tool steel is because of the presence of the alloys. This steel is known for its wear resistance properties. Main applications of this steel are fixtures, gauges, blanking and forming dies. It has approximately (1.45% to 2.30%) carbon content which is responsible for its higher wear resistance and hardness properties. According to ASTM steel standards, “W” for Water hardening (grades – W1, W2, W5), “O” for oil hardening (grades – O1, O2, O6, O7), “A” for medium alloy air hardening (grades – A2, A4, A6, A7, A, A9, A10, A11), “D” for high carbon, high chromium tool steel series (grades – D2,D3, D4,D5,D7).
Hot Work Tool Steel
Hot work tool steel is used for manufacturing extrusion and forging, pipe and glass manufacturing, pressure die casting. In the ASTM standards, hot work tool steel are H10, H11, H12, H13, H14, H19, H21, H22, H23, H24, H25, H26, H42 Steel.
This steel can be classified into different categories as per their chemical composition.
Chromium hot work tool steel
Steel grades H10 to H19 falls into this category. It has carbon content of around 0.34 to 0.40 and working hardness is measured around 400~600 HV. Normal working temperature is below 540C.
Tungsten hot work tool steel
Steel Grade from H21 to H26 falls into this category. Its hardness is measured round 450-600 HV.
Molybdenum Tungsten Hot Work Tool Steels.
Steel Grades from H41 to H43 falls into this category. This steel has high molybdenum and low carbon content.
How to select the right steel for the application?
Which tool steel is right for the application? Hot work tool steel or cold work tool steel? It depends on the material which needs to be broken or cut. The selection criteria depends on many parameters like the precision, work environment, cost etc. Tool steel suppliers can guide you to select the right steel for your application.
Hot work tool steel is ideal for the processes which involves pressure, heat and abrasion. This steel is known for properties like heat resistance, shock resistance, deformation resistance at high temperature, and good machinability. Disadvantages of this steel are that high temperature for manufacturing tools and if the quality of steel is not good wear and tear may occur.
Cold work tool steel is ideal for the applications where the surface temperature of the tool is not exceeding 260C. It is also ideal for the processes where there are no problems of high abrasion or wear. This steel can be categorised as air hardening, oil hardening and high carbon high chromium steel. It is relatively low cost steel. Disadvantage of this steel is that it is not ideal for the tools that have to face high abrasiveness.