Steel properties

ALTA 7CrSiMnMoV/CH1 steel is also called as "Flame hardening cold work tool steel". This steel has a good hardenability, wide quenching temperature range (840~1000℃), and low overheat sensitivity. It can be oil-cooled or air-cooled, and has small deformation after quenching (air quenching >=60HRC).

For cold working molds that require higher strength and toughness, CH1/7CrSiMnMoV steel is a good choice to replace T10A, 9Mn2V/1.2842, GCr15/52100, CrWMn/1.2419, Cr12MoV, D3/1.2080 steels, which can increase the molds life by more than 1 times.

Applications

² It can be used to manufacture blanking dies, punching dies, trimming dies, bending dies, pressing dies, drawing dies, cold extrusion dies, cold heading dies and other cold working dies

² It can also be used to manufacture non-metal forming dies such as plastic molds, rubber molds, bakelite molds, clay molds, etc

Chemical composition

Chemical Composition per %

Heat treatment

CH1/7CrSiMnMoV steel can obtain a hardness of over HRC60 after flame quenching, and is usually used without tempering. This is because there is a large residual compressive stress in the surface of the hardened layer, which can improve fatigue strength. For non-large flame quenched parts, that is overall quenching, various hardnesses can be obtained through tempering. For example:

1. Cold punching dies

Tempering at 180℃ can obtain HRC58~62.

2. Plastic molds

Tempering at 400~450℃ can obtain HRC50~54.

CH1/7CrSiMnMoV steel has good tempering resistance, and it is best to temper it in one time. If required, it can also be tempered in two times.

Coefficient of linear expansion : α(mm/(mm·°C))

Effect of quenching temperature and cooling method on hardness :

Effect Of heating time on hardness :

The grade of martensite after quenching at heating temperatures :

Quenching TEmperature and austenite content :

The effects between quenching temperature, holding time coefficient and austenite grain size :

Recommended flame Quenching process :

The wear resistance of 7CrSiMnMoV steel is poor. When it's used to manufacture the main working parts of cold pressing dies such as concave and convex molds, it must be surface treated in advance, otherwise it will easily be scrapped due to excessive wear. The surface treatment is quenched with acetylene flame, so 7CrSiMnMoV steel is called flame quenched steel. The nozzles used for quenching are divided into single nozzle and double nozzle. Before quenching, the materials must be preheated at a temperature of about 180~200℃ for 2h, and then quenched with acetylene flame. The process parameters, hard layer depth and range are:

1).  Single nozzle heating temperature 900~1000℃, heating rate 200~260mm／min, hardened layer depth 2.5~3mm, hardened zone width 12~15mm;

2).  Double nozzle temperature 900~1000℃, heating rate 180~220mm／min, hardened layer depth 6.5~7.5mm, hardened zone width 14~16mm.

Whether it is a single nozzle or a double nozzle, the hardness after quenching is above 60HRC, and the deformation is very small, generally 0.020%~0.05%.

In addition, since as flame quenching is only performed on the surface of the workpiece, the matrix hardness below the hardened layer is lower, which is similar to that of a gear (the tooth surface of a gear is harder and the tooth center is tougher). In this way, during the working process, the cutting edge is not likely to break or collapse. After quenching, the wear resistance of the steel increases, and the working parts processed with this steel are not likely to wear, thereby increasing the service life of the mold.

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Features

² High hardness after quenching

² Good hardenability

² Good strength

² Good toughness

² Heat treatment processing is simple and cost-effective