ALTA 7Cr7Mo2V2Si/LD Cold Work Tool Steel (improved strength-toughness)

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Cold work tool steel

ALTA 7Cr7Mo2V2Si(LD) Tool Steel Specification

Steel properties

ALTA 7Cr7Mo2V2Si/LD is a new developed type of cold working die steel. While by ensuring a good wear resistance, the steels strength and toughness are greatly improved than normally used High Carbon-High Chromium steels. Its strength, toughness, fatigue fracture resistance, etc. are all better than Cr12MoV, W18Cr4V/1.3355 steels. This steel has good cold and hot processing performance, with a wide heat treatment temperature range and small deformation.

7Cr7Mo2V2Si/LD is suitable for manufacturing difficult-to-deform forming molds or have complex shapes, especially when the molds needs to withstand large impact and bending loads, its premium performance stand out.

Applications

² Large and medium-sized punching dies

² Heavy-duty cold heading dies

² Cold extrusion dies

Chemical composition

Chemical Composition per %

	C	Si	Mn	P	S	Cr	Mo	V	Ni	Cu
Min.	0.70	0.85				6.50	2.05	1.72
Max.	0.80	1.05	0.50	0.030	0.020	7.50	2.50	2.20	0.25	0.25

Basic melting process :

IM/EAF + LF + VD+(ESR)

Hardness :	Max 230 HB (annealed)
Reduction ratio :	5 : 1 minimum or required
Grain size :	≥ 6.0 per ASTM E112
Non-metallic inclusion :	≤ 1.0 (thick), ≤ 1.5 (thin) per ASTM E45 method A (more pure by ESR route)
Ultrasonic Test	SEP1921, EN 10308, ASTM A388 or agreed methods
Macro-structure	As per ASTM E381
Straightness / flatness	≤ 1.5 mm / m (machined), ≤ 2.5 mm / m (black)
Tolerance	Per discussed
Size range (round bars)	Ø 12 - 500 mm
Size range (flats, plates)	8 - 400 mm in thickness max. 1100 mm in width

Heat treatment

Annealing	Temperature(°C)	Hardness
Annealing	840 - 870	max. 230 HB

Hot-forming	Temperature(°C)
	850 - 1150

Hardening and tempering	Quenching temperature(°C)	Quenching medium	Frequently-used tempering temperature(°C)
Hardening and tempering	1100 - 1180	Oil	510 - 620

Ac1	Accm	Ar1	Arcm	Ms
876	925	725	815	105

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

Temperature °C	20~100	20~200	20~300	20~400	20~500	20~625	20~700
Αx 10-6	8.2	10.2	11.3	11.8	12.4	12.7	12.9

Mechanical properties of 7Cr7Mo2V2Si/LD steel after different heat treatments :

Temperature °C	Tempering °C and rounds	Tensile strength (Mpa)	Compressive strength (Mpa)	Bending strength (Mpa)	Deflection δ(mm)	Impact toughness J/cm2
1100	510 x 1h x 3	2354	2658	4599	6.7	32.36
	530 x 1h x 3	2432	2765	5413	8.9	71.59
	550 x 1h x 3	2530	2501	5325	16.5	113.76
	570 x 1h x 3	2452	2295	4894	16.5	101.99
	590 x 1h x 3	-	2040	4295	16.5	47.07
1150	510 x 1h x 3	1432	2667	3501	3.7	-
	530 x 1h x 3	2314	2864	4580	4.7	43.15
	550 x 1h x 3	2628	2810	5482	12.7	96.04
	570 x 1h x 3	2628	2609	5090	8.3	101.92
	590 x 1h x 3	2295	2187	4697	9.8	80.36
1180	510 x 1h x 3	1236	2550	2824	4.6	-
	530 x 1h x 3	1491	3168	2854	3.5	28.42
	550 x 1h x 3	2716	2756	4982	5.7	71.54
	570 x 1h x 3	2560	2648	4639	6.5	44.10
	590 x 1h x 3	2422	2442	4786	7.1	41.16

**Generally
1. Quenching 1150°C, Oil, tempering 550°C x 3 rounds, the strength is the highest
2. Quenching 1100°C, Oil, tempering 550°C x 3 rounds, the toughness is the highest.
But the comprehensive Performance of No.1 processing is better.

Performance Comparison of LD, Cr12MoV, W18Cr4V/~1.3355, W6Mo5Cr4V2/~1.3343 :

Material	Heat treatment		Bending strength (N/mm2)	Impact toughness (J/cm2)	Fracture toughness (N•MM1/2)	Hardness (HRC)
Material	Quenching °C	Tempering °C	Bending strength (N/mm2)	Impact toughness (J/cm2)	Fracture toughness (N•MM1/2)	Hardness (HRC)
Cr12MoV	970 Oil	200 x 2	3110	50	646	58.5
Cr12MoV	1080 Oil	200 x 2	2670	48	686	61.5
W18Cr4V	1260 Oil	560 x 3	2880	24.6	489	65.5
W6Mo5Cr4V2	1190 Oil	560 x 3	3210	26.7	494	66.5
7Cr7Mo2V2Si/LD	1100 Oil	550 x 3	5325	114	610	61.1
	1100 Oil	570 x 3	4894	102	629	59.7
	1150 Oil	550 x 3	5482	96	640	62.1
	1150 Oil	570 x 3	5090	102	675	60.7

(x2, x3 means the tempering rounds)
** It can shows that the most standout performance of 7Cr7Mo2V2Si/LD steel is the Strength and toughness. It also have a high hardness and good wear resistance.

Recommended quenching + tempering processing for different applications :

Applications	Pre-heating	Quenching	Medium	1st Tempering	2nd Tempering	Hardness (HRC)
Punching dies	850±10 °C, 30s/mm	1140±10 °C， 25~30s/mm	Oil	600 °C x 1h	550 °C x 2h x 2 rounds	57 ~ 60
Cold heading, cold extrusion dies	850±10 °C, 30s/mm	1140±10 °C， 25~30s/mm	Oil	550 °C x 1h x 3 rounds	-	60 ~ 63

** It must go through “Pre-heating” processing before quenching (staged preheating is also recommendedd, the first preheating is 600~620°C, the second preheating is 840~860°C), generally preheating time is twice than quenching time and depends on the shape and size of the mold parts.
** Quenching temperature chose from 1100 to 1150°C, the quenching heating coefficient is 25~30s/mm, and it is advisable to use a salt bath furnace to avoid decarburization.

Downloads

2024-06-12 Alta 7Cr7Mo2V2Si(LD) (011 - S6 - T2).pdf

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Product images

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Features

² High strength and toughness

² Good wear resistance

² Good cold and hot processing performance

² Good dimensional stability

2024-06-12 Alta 7Cr7Mo2V2Si(LD) (011 - S6 - T2).pdf