Armour-plate and process for its manufacture

A process for forming an armour plate which comprises the steps of:

• (a) forming a first layer of steel containing (in percent by weight)
• ______________________________________ 0.30 to 0.80% carbon 0.10 to 0.80% silicon 0.40 to 1.20% manganese up to 0.015% phosphorus up to 0.015% sulfur 0.20 to 2.80% chromium 0.05 to 1.00% molybdenum 0.01 to 0.05% aluminum up to 0.40% nickel ______________________________________
• remainder iron including unavoidable impurities;
• (b) forming a second layer containing (in percent by weight)
• ______________________________________ 0.17 to 0.40% carbon 0.10 to 0.80% silicon 0.40 to 2.00% manganese up to 0.025% phosphorus up to 0.025% sulfur 0.10 to 1.50% chromium 0.05 to 1.50% molybdenum 0.01 to 0.05% aluminum ______________________________________
• remainder iron including unavoidable impurities,
• (c) disposing said first layer over said second layer so that said first layer constitutes an upper layer and said second layer constitutes a base layer;
• (d) cladding said upper layer to said base layer by:
• (1) cladding to end thickness by rolling or
• (2) explosive cladding with subsequent hot rolling to end thickness;
• subsequently heating said clad steel to a temperature within the range from 880.degree. to 980.degree. C., maintaining the so heated clad steel at such temperature and thereafter, cooling the same down so as to convert into martensite all of said upper layer and at least about 75% of said base layer such that the hardness of said base layer is at least 380 HB and wherein the difference in the hardness between said upper layer and said base layer is at least 130 HB, but not greater than 300 HB.