Cylinder for molding machine, and its production method

Patent metadata

Field	Value
Publication number	US-11389869-B2
Application number	US-201816632670-A
Country	US
Kind code	B2
Filing date	Aug 31, 2018
Priority date	Aug 31, 2017
Publication date	Jul 19, 2022
Grant date	Jul 19, 2022

Abstract

A cylinder for a molding machine comprising a HIP-sintered lining layer on an inner surface of a cylindrical steel body, the lining layer comprising 38-70% by volume of tungsten carbide particles having a median diameter d50 of 1-7 μm and a matrix composed of an Ni-based alloy, and the maximum length of the matrix in an arbitrary cross section being 12 μm or less.

First claim

What is claimed is:

1. A cylinder for a molding machine comprising a HIP-sintered lining layer on an inner surface of a cylindrical steel body;
said lining layer comprising 38-70% by volume of tungsten carbide particles having a median diameter d 50 of 1-7 μm and a matrix composed of an Ni-based alloy;
said lining layer having a structure in which the tungsten carbide particles are uniformly dispersed in the matrix composed of the Ni-based alloy; and
the maximum length of said matrix in an arbitrary cross section being 12 μm or less,
wherein the maximum length of said matrix is determined by drawing two diagonal lines on a SEM photograph taken at a magnification of about 1000 times, measuring the lengths of line segments of each diagonal line crossing matrix regions composed of the Ni-based alloy with no tungsten carbide particles and no boundary phases, and averaging the maximum lengths in 10 fields, wherein the SEM photograph has a field area of 127 μm×94 μm and is obtained by using an acceleration voltage of 10.0 kV, and
wherein said matrix composed of an Ni-based alloy comprises by mass 1-7% of Si, 5-20% of Cr, 1-4% of B, 0.5-1.5% of Mn, 12% or less of Co, and inevitable impurities.

2. The cylinder for a molding machine according to claim 1 , wherein said tungsten carbide particles have d 10 of 0.5-3 μm and d 90 of 5-15 μm, wherein d 10 and d 90 are particle sizes at cumulative volumes corresponding to 10% and 90%, respectively, of the total volume, in a curve expressing the relation between the particle size and cumulative volume of said tungsten carbide particles,
wherein the cumulative volume is obtained by accumulating the volume of particles having sizes up to a particular size.

3. The cylinder for a molding machine according to claim 1 , wherein said lining layer contains 45-60% by volume of said tungsten carbide particles.

4. A method for producing the cylinder for a molding machine recited in claim 1 , comprising the steps of
arranging a steel mandrel inside a cylindrical steel body to form a space between an inner surface of said cylindrical body and said mandrel;
filling said space with a powdery mixture comprising tungsten carbide powder and Ni-based alloy powder at a volume ratio of 38/62 to 70/30;
evacuating and sealing said space containing said powdery mixture, and then subjecting said powdery mixture to HIP to obtain a composite cylinder whose cylindrical body is lined with a Ni-based alloy containing tungsten carbide particles; and
machining said composite cylinder;
said tungsten carbide powder having a median diameter d 50 of 1-7 μm, and d 50 /(d 90 -d 10 ) of 0.4 or more; and
said Ni-based alloy powder having a median diameter d 50 of 2-8 μm, and d 50 /(d 90 -d 10 ) of 0.6 or more.

Assignees

• Hitachi Metals Ltd

Inventors

• Segawa Takayuki
• Furushima Kiyoshi

Classifications

• B22F5/007

  of moulds · CPC title

• B29C45/62

  Barrels or cylinders · CPC title

• C22C29/067

  comprising a particular metallic binder · CPC title

• B29C33/38

  characterised by the material or the manufacturing process (B29C33/44 takes precedence) · CPC title

• C23C24/085

  Coating with metallic material, i.e. metals or metal alloys, optionally comprising hard particles, e.g. oxides, carbides or nitrides · CPC title