Method of producing electrical resistor

• US 3,964,943 A
• Filed: 11/29/1974
• Issued: 06/22/1976
• Est. Priority Date: 02/12/1974
• Status: Expired due to Term

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Andersen, Niels Lervad
• Primary Examiner(s): Powell, William A.
• Application Number:
  US05/528,076
• Time in Patent Office: 571 Days
• Field of Search: 264/42-44, 264/61, 264/344, 13/25, 156/7, 156/6, 156/77, 156/8, 156/17, 156/153, 156/154, 75/20 F, 75/204, 75/222, 338/322, 338/326, 338/328, 338/330, 338/333, 427/101, 427/243, 427/247, 29/610, 29/611
• US Class Current: 216/16
• CPC Class Codes: F23Q 7/22 Details
• CPC Class Codes: H01C 7/048 Carbon or carbides
• CPC Class Codes: H05B 3/64 using ribbon, rod, or wire heater
• CPC Class Codes: Y10T 29/49082 Resistor making

Abstract

The invention relates to an electrical resistor with a SiC body, particularly for ignition or heating purposes, and to a method of producing such electrical resistor.

Claims

1. A method of producing a silicon carbide electrical resistor which comprises forming under pressure a dense and substantially nonporous body consisting essentially of silicon carbide and free silicon, and etching a middle portion of said body with acid to remove essentially all the free silicon therefrom to thereby obtain a middle portion consisting essentially of a porous matrix of silicon carbide free of silicon and two end portions consisting essentially of silicon carbide and free silicon.

2. A method according to claim 1 wherein a metal is applied to said end portions which forms a eutectic with free silicon in said end portions.

3. A method according to claim 2 wherein said body consists of silicon carbide and carbon, the amount of carbon being less than stoichiometric with respect to the amount of silicon diffused into the body, and wherein the body is subsequently sintered to cause the reaction in situ of said carbon and said silicon to provide said body consisting essentially of silicon carbide and free silicon.

4. A method according to claim 3 wherein before impregnation with silicon the body is treated with SiO at least in the region of said two end portions.

5. A method according to claim 1 wherein, before etching, the cross-sectional area of middle portion of the body is reduced relative to the cross-sectional area of the end portions by grinding.