A method of manufacturing a weldment made of ductile iron

 

(57) Abstract:

Usage: for arc welding products from high-strength nodular cast iron in the oil and gas industry, power engineering, shipbuilding, utilities. The inventive welding carry out TIG method non-consumable electrode with additional filler wires. And for welding the root pass of the wire has a composition, wt.%: iron is 1.0-10.0; manganese 0,5-9,0; Nickel else, when the Nickel content of at least 90 wt.%, and for subsequent welding seams use a wire of the following composition, wt. %: Nickel 40,0-55,0; iron 30,0-45,0; chromium of 0.1-7.0 and manganese else. As a result of implementing the proposed method of welding weld withstands pressure up to 10-25 MPa. 2 C.p. f-crystals, 2 Il.

The invention relates to welding, in particular for arc welding products from high-strength cast iron, and can find application in the oil and gas industry, power engineering, shipbuilding, utilities.

There is a method of mechanized cold arc welding of cast iron, which are consumable electrode, mild steel and weld pool serves a filler rod of alertsa of the conditions are good welding weld metal with cast iron body parts. This method does not provide high-quality welds and is not applicable for non-welding joints.

There is a method of welding with non-consumable electrode of nodular cast iron with pre-heating and subsequent heat treatment [2]

However, this method does not provide high quality welding curved joints in the manufacture of shaped articles from high-strength cast iron.

This method is the closest to the claimed and accepted as a prototype.

The purpose of the invention, the quality of the welding seam in arc welding of articles made of ductile iron, providing the possibility of making shaped articles from high-strength cast iron.

This objective is achieved in that in the method of manufacturing a weldment of high-strength nodular cast iron, including preparation of edges for welding, preheating to a temperature of 250-500oC, welding in argon non-consumable electrode and the weld heat treatment, characterized in that the welding of the root pass are using filler wire of the following composition, wt.

Iron is 1.0-10.0

Manganese 0,5-9,0

Nickel OS the following chemical composition, wt.

Nickel 40,0-55,0

Iron 30,0-45,0

Chromium is 0.1-7,0

Manganese Else

Heat treatment after welding by heating the welded connection at speeds of no more than 20oC/C to 950-970oC, cooling in air to a temperature of 700-720oWith, re-heating at a rate not exceeding 20oC/C to a temperature of 950-970oC and subsequent cooling in air to ambient temperature. When the heat treatment in the furnace welded joint is heated to temperature 950-970oWith speeds of no more than 20oWith a/C, maintained at that temperature for 8-12 min, then cooled to a temperature 730-740oC, maintained at that temperature for at least 8 min and cooled in air to ambient temperature.

Novelty and inventive step of the claimed technical solution is confirmed by the fact that only by using this method it is possible to manufacture welded fittings made of ductile iron, having a minimum burst pressure of 10-25 MPa.

In Fig. 1 shows an example of cutting welding joint; Fig. 2 is a graph of the temperature of the weld by heat treatment.

The proposed method for the manufacture of welded products RUB cleaned from oil, dirt, rust, moisture and other contaminants. Then on the ends of the edges of the chamfer angle 273oto the end surface, after which obtochuyut the inner surface of the billet width not less than 7 mm from the welded end and a depth of not less than 0.7 mm, the Outer surfaces of the workpieces stitch width not less than 10 mm from the welded end and a depth of not less than 0.1 mm, an Inner surface abutting the ends of the blanks be ground to the same diameter. Fit-up welding is no gap between the blade edges. Pets local gap width of not more than 0.6 mm for a length of not more than 1/3 of the circumference. Allowable offset edges relative to each other is not more than 0.8 mm on the site no more than 1/3 of the circumference. The Assembly of the welding joint, it is desirable to produce the lairs, the alignment - regulating pricedoc under lairs. Preheating is carried out by a gas flame. Possible induction heating with a heating rate of not more than 20oWith a/C. the Width of the heated portion is not less than 80 mm and heating at full depth. Preheating temperature of 250-500oC. After warming up, perform the welding of the root pass of a consumable electrode in argon using a filler wire is Oka composition, wt. Ni 52; Fe 36; Cr 7; Mn 5.

Post-weld heat treatment of welded site is produced as follows. In field conditions, the heating of the weld to produce an oxygen-propane torch. For pipes with a diameter of 150 mm is required at least two burners. Heating is carried out to a temperature of 950-970o, Then cooled to 700-720oWith and heated to 950-970oWith subsequent cooling in air. The heating rate and cooling is maintained equal to the 20oWith/s

In workshop conditions the heat produced in the furnace. The product is placed in an oven with a temperature of 1000oC until the welded Assembly is heated, the temperature in the furnace drops to 960oSince, at this temperature, incubated 10 min, after which the welded Assembly is transferred into a furnace with a temperature 730-740oC and incubated for 9 minutes and Then the product is removed from the furnace and cooled in air to the shop temperature.

Produced by the proposed method welded joints of pipes and fittings made of high-strength nodular cast iron has stood the test of high pressure. Thus, the welded connection of pipes with a diameter of 100 mm with wall thickness of 6.1 mm withstood the pressure of 15 MPa. According to the claimed method provides welding natvig is S="ptx2">

1. Method of making welded articles from high-strength nodular cast iron, including preparation of edges for welding, preheating to 250 To 500°C, welding in argon non-consumable electrode and the weld heat treatment, characterized in that the welding of the root pass are using filler wire of the following composition, wt.

Iron 1 10

Manganese 0,5-9,0

Nickel Else

when the Nickel content of at least 90% and for subsequent welding seam filler wire take the following composition, wt.

Nickel 40 55

Iron 30 45

Chromium is 0.1-7,0

Manganese Else.

2. The method according to p. 1, characterized in that the heat treatment of the weld is produced by heating the welded connection at a speed of not more than 20 deg./with up to 950 970°C, cooling in air to 700 720°C, re-heating at a rate of not more than 20 deg./with up to 950 970oC and subsequent cooling in air to ambient temperature.

3. The method according to p. 1, characterized in that the heat treatment of the weld is produced by heating the welded connection to 950 970°C at a rate of not more than 20 deg. /s isothermal holding at this temperature for 8 to 12 min, ohlazhdeniya air to ambient temperature.

 

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