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1.Application

These standards regulates high speed tool steels (hereafter steels) made through either hot rolling or forging.

2.Types

There are 13 types of steel and their symbols are as shown in table 1.

*[table1]


Types	Symbols
1 Types 2 Types 3 Types 4 Types 5 Types 6 Types 7 Types	STC 1 STC 2 STC 3 STC 4 STC 5 STC 6 STC 7

3.Production method

- Steel is produced from Killed steel.
- The steel, unless specifically designated, must be rolled or forged at the temper rate of over 4S.
However, for cases where the rate is below 4S. upsetting forging can make up for the lower rate.
- The steel, unless specifically designated must be annealed. however, steel plates and steel beams should remain as they are unless specifically mentioned.

4.Chemical component

Chemical component of steel is defined by ladle analysis. in accordance to table2.

*[table 2]


Symbols	Chemical component%					Reference Usage
Symbols	C	Si	Mn	P	S	Reference Usage
STC1	1.30~1.50	0.35 under	0.50 under	0.030 under	0.030 under	files
STC2	1.10~1.30	0.35 under	0.50 under	0.030 under	0.030 under	drill,metal work file, small puncher, razor blade, windup spring, metal saw
STC3	1.00~1.10	0.35 under	0.50 under	0.030 under	0.030 under	Dies for making screws, metal saw, press mould, gauge, windup spring, chisel
STC4	0.90~1.00	0.35 under	0.50 under	0.030 under	0.030 under	Windup spring, woodwork drill, ax,chisel, needles, razor blade, woodwork belt saw,pen tip, press mould, gauge
STC5	0.80~0.90	0.35 under	0.50 under	0.030 under	0.030 under	Marking press, press mould, windup spring, belt saw, round saw, pen tip,gile, gauge
STC6	0.70~0.80	0.35 under	0.50 under	0.030 under	0.030 under	Marking press, snap, round saw, windup spring, press mould, file
STC7	0.60~0.70	0.35 under	0.50 under	0.030 under	0.030 under	Marking press, snap, press mould, knife
Note : For steel that are not annealed, annealing in table3 will take place, followed by hardened tempering.

5. Annealing hardness

Annealing hardness of steel is as seen in table3. But for cases where it is difficult to use .
Brinnel hardness, it is possible to use Rockwell B hardness or Vickers hardness,
depending on the agreement by the manufacturer and the buyer.

*[table 3]


Symbols for types	Annealing temperature C	Annealing hardness HB
STC 1 STC 2 STC 3 STC 4 STC 5 STC 6 STC 7	750~780 slow cooling 750~780 slow cooling 750~780 slow cooling 740~760 slow cooling 730~760 slow cooling 730~760 slow cooling 730~760 slow cooling	217 under 212 under 212 under 207 under 207 under 201 under 201 under

6. hardening tempering hardness

For the tests that represents hardening and tempering hardness, the hardness of tempering and hardening after taking an appropriate temperature given in table 4, the hardness of hardening and tempering will be as seen in table4.

*[table 4] Tested hardening tempering hardness


symbol	Heat treatment °C		Hardening, tempering hardnessHRC
	Hardening	Tempering
STC 1 STC 2 STC 3 STC 4 STC 5 STC 6 STC 7	760~820 water-cooled 760~820 water-cooled 760~820 water-cooled 760~820 water-cooled 760~820 water-cooled 760~820 water-cooled 760~820 water-cooled	150~200 air-cooled 150~200 air-cooled 150~200 air-cooled 150~200 air-cooled 150~200 air-cooled 150~200 air-cooled 150~200 air-cooled	63 over 63 over 63 over 61 over 59 over 57 over 56 over
Note: For steel that are not annealed, annealing should be done as seen in table3, followed by hardening tempering.

7. Appearance, shape, size and their allowance

1 Hot rolled rounded steel
- In appearance, hot rolled rounded steel should have good finishing and must have
no hazard for use.


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