The invention relates to an iron-based alloymaterial whichcontainsCr-Ni-Mo for the manufacture of steel pipe piercing plug.

At present, the piercing plug material used for carbon steel and alloy steel pipe can be divided into two categories of alloy tool steel and alloy structural steel, alloy tool steel category: such as 3cr2w3v, H13, 5crnimo, etc., this type of alloy tool steel high temperature strength, good wear resistance is a traditional piercing plug materialbe used large quantities, Alloy tool steel plugdivided into inset molybdenum and not inset molybdenum; This kind of high alloy steel toughness is poor, resistance of fatigue performance is not good, very easy to cause the plugs surface cracking and shorten its lifein the rapid cold and hot piercing conditions. In addition, because of the high alloy content, the cost is very expensive.

In order to make up for the poor toughness of alloy tool steel plugs, many manufacturers use better toughness of carbon steel and alloy structural steel materials to manufacture plugs, such as 20 # steel, 45 # steel, 30cini3, 20crnisiw, 35crmo, etc., although these materials high temperature strength is lower than high-alloy tool steel, but because of its toughness is better, which also used in large quantities because of its better toughness and cost than alloy tool steel. These materials generally need to undergo special oxidation treatment to make the surface of the plugs generating dense, good adhesion, a certain thickness of oxide layer to play the role of lubrication and insulation. For the purpose of solving the surface easy to soften and produce plastic deformation, shortening the service life, the technology of nitriding oxidation treatment on the plugs surface emerged. Using nitriding treatment to improve the hardness of the plugs surface to make up for the lack of hardness of the plugs surface of alloy structural steel. For example, Japanese patent application 59-143079 discloses a "method of manufacturing tool material for rolling pipes", which material composition (wt%) is: C0.20 ~ 0.60, Si 0.10 ~ 0.20, Mn 0.30 - 2.0, Cr 1.0 - 6.0, Ni 0.50 - 6.0, in addition, containing 0.02-20 Nb or 0.02 - 2.0 v, the rest is Fe and unavoidable impurities. After smelting and casting, processed according to the requested shape, then nitriding at 50-1100 ℃, the depth of nitriding layer is more than 10μm, following oxidation treatment at 900-1250 ℃. When the above treatment is carried out on the plugs, the solubility of nitrogen in iron decreases during high temperature oxidation treatment, and nitrogen ions escape from the surface of the plugs losing the effect of nitriding; if oxidation treatment is carried out first and then nitriding treatment good to the surface hardness increases but the hardness of the whole plugs outside the nitriding layer will be reduced, which affects the service life of the plugs.