阅读说明：本技术 一种lng储罐高锰低温钢用无缝药芯焊丝及制备方法 (Seamless flux-cored wire for high-manganese low-temperature steel of LNG storage tank and preparation method ) 是由 王亚彬 亢天佑 叶凡 于 2019-10-29 设计创作，主要内容包括：本发明涉及一种LNG储罐高锰低温钢用无缝药芯焊丝,包括质量百分数为60-70%的低碳钢带外皮和质量百分数为30-40%药芯；按照质量百分比计,所述药芯包括电解金属锰65%-75%、镍粉8%-14%、硅粉1.0%以下、纯碱1.0%以下、高碳铬铁2%-8%、烧结粉体4%-8%,其余为铁粉；所述烧结粉体包括新型钛酸钾25%-30%、氧化铝20%-25%、石墨10%-15%、镁砂25%-30%,其余为粘结剂。该焊丝可用于LNG储罐的建造,在超低温下具有良好的冲击韧性及与母材匹配的强度；且该焊丝具有良好的焊接工艺性,可适用于多种位置焊接,同时具有与母材相匹配的化学成分,与母材之间平滑过渡、无裂纹。(The invention relates to a seamless flux-cored wire for high-manganese low-temperature steel of an LNG storage tank, which comprises a low-carbon steel belt sheath and a flux core, wherein the low-carbon steel belt sheath is 60-70% by mass, and the flux core is 30-40% by mass; according to the mass percentage, the flux core comprises 65-75% of electrolytic manganese metal, 8-14% of nickel powder, less than 1.0% of silicon powder, less than 1.0% of soda ash, 2-8% of high-carbon ferrochrome, 4-8% of sintered powder and the balance of iron powder; the sintering powder comprises 25-30% of novel potassium titanate, 20-25% of alumina, 10-15% of graphite, 25-30% of magnesia and the balance of a binder. The welding wire can be used for building an LNG storage tank, and has good impact toughness and strength matched with a base metal at ultralow temperature; the welding wire has good welding manufacturability, is suitable for welding at various positions, has chemical components matched with the base metal, and is in smooth transition with the base metal without cracks.)

1. The utility model provides a LNG storage tank high manganese low temperature is seamless flux cored wire for steel which characterized in that: comprises 60 to 70 mass percent of low carbon steel belt sheath and 30 to 40 mass percent of flux core;

according to the mass percentage, the flux core comprises 65-75% of electrolytic manganese metal, 8-14% of nickel powder, less than 1.0% of silicon powder, less than 1.0% of soda ash, 2-8% of high-carbon ferrochrome, 4-8% of sintered powder and the balance of iron powder;

according to the mass percentage, the sintering powder comprises 25-30% of novel potassium titanate, 20-25% of alumina, 10-15% of graphite, 25-30% of magnesia and the balance of binder.

2. The seamless flux-cored wire for the high-manganese low-temperature steel of the LNG storage tank as claimed in claim 1, wherein: the granularity of the electrolytic manganese metal, the nickel powder and the high-carbon ferrochrome is controlled to be 80-120 meshes.

3. The seamless flux-cored wire for the high-manganese low-temperature steel of the LNG storage tank as claimed in claim 1, wherein: the outer skin of the low-carbon steel strip is made of an SPHC steel strip.

4. The method for preparing the seamless flux-cored wire for the high-manganese low-temperature steel of the LNG storage tank as claimed in claim 1, wherein the method comprises the following steps: the method comprises the following steps:

the method comprises the following steps: weighing the raw materials according to the mass percentage for later use;

step two, preparing sintered powder, uniformly mixing the powder by a V-shaped mixer, and adding a binder to obtain wet powder; placing the wet powder in a crucible for sintering treatment; crushing the sintered powder, and controlling the particle size of the powder at 100-320 meshes to obtain sintered powder;

and step three, uniformly mixing the sintered powder obtained in the step two with other raw materials according to a ratio to obtain the flux-cored powder, synchronously adding the flux-cored powder on the outer steel belt on line, forming and welding the outer steel belt added with the flux-cored powder by a roller, and annealing and reducing the diameter of the outer steel belt into a seamless flux-cored wire with the diameter of 1.2 mm.

5. The method of claim 4, wherein: and step two, the binder comprises water glass accounting for 4-12% of the weight of the sintered powder and water accounting for 2-8% of the weight of the sintered powder.

6. The method of claim 4, wherein: the filling rate of the medicine core powder is 32-37%.

Technical Field

The invention belongs to the technical field of welding materials, and particularly relates to a seamless flux-cored wire.

Background

With the rapid development of global economy and environmental protection in various countries, demand for LNG (liquefied natural gas) is increasing. As a country with large energy consumption, China mainly depends on sea transportation import, and the demand of facilities for LNG storage is huge. The construction of LNG carriers and LNG receiving stations is urgent.

LNG is generally stored and transported at-163 ℃, and aluminum alloy, nickel alloy steel (9% Ni), stainless steel, and the like have been mainly used as main materials of LNG storage tanks. However, these materials generally have low strength and low workability, and thus are limited in application. In addition, the Ni content of the product which is expensive is high, and the product cost is greatly increased. The high manganese steel for extremely low temperature is produced by adding a certain amount of Mn element to steel and subjecting the steel to appropriate heat treatment. Manganese metal has small price fluctuation in the international raw material market, and high manganese steel can maintain ideal performance even under extremely low temperature conditions, and has attracted attention as a new material for the second-generation LNG storage tanks.

As a matched welding material of high manganese steel, the flux-cored wire has the characteristics of high automation degree, high welding speed, capability of performing all-position welding, attractive weld joint forming and the like. At present, the flux-cored wire which is applied more in the market is a seamed flux-cored wire. Compared with the traditional seamed flux-cored wire, the seamless flux-cored wire has the following advantages: the crack incidence rate of the weld metal is effectively reduced, and the gas hole resistance is high; the moisture absorption resistance is strong, and the product does not need to be dried again after being stored in a humid environment for a long time; the surface of the welding wire can be plated with copper, so that the rust resistance of the welding wire is improved; the outer skin steel band has no clearance, and the wire feeding performance and the welding wire alignment performance are excellent, and the electric arc is more stable.

Disclosure of Invention

In order to solve the problem of wire breakage in the drawing and reducing process of the seamless flux-cored wire under the condition of high filling rate, the invention aims to provide the seamless flux-cored wire for the LNG storage tank high-manganese low-temperature steel, and aims to provide a method for preparing the seamless flux-cored wire. The welding wire can be used for building an LNG storage tank, and has good impact toughness and strength matched with a base material at ultralow temperature (-196 ℃); the welding wire has good welding manufacturability, is suitable for welding at various positions, has chemical components matched with the base metal, and is in smooth transition with the base metal without cracks.

In order to achieve the purpose, the invention adopts the specific scheme that:

a seamless flux-cored wire for high-manganese low-temperature steel of an LNG storage tank comprises a low-carbon steel belt sheath accounting for 60-70% by mass and a flux core accounting for 30-40% by mass;

according to the mass percentage, the flux core comprises 65-75% of electrolytic manganese metal, 8-14% of nickel powder, less than 1.0% of silicon powder, less than 1.0% of soda ash, 2-8% of high-carbon ferrochrome, 4-8% of sintered powder and the balance of iron powder;

according to the mass percentage, the sintering powder comprises 25-30% of novel potassium titanate, 20-25% of alumina, 10-15% of graphite, 25-30% of magnesia and the balance of binder.

As a further optimization of the scheme, the granularity of the electrolytic manganese metal, the nickel powder and the high-carbon ferrochrome is controlled to be 80-120 meshes.

As a further optimization of the scheme, the low-carbon steel belt outer skin is made of an SPHC steel belt.

The invention also provides a method for preparing the seamless flux-cored wire, which comprises the following steps:

the method comprises the following steps: weighing the raw materials according to the mass percentage for later use;

step two, preparing sintered powder, uniformly mixing the powder by a V-shaped mixer, and adding a binder to obtain wet powder; placing the wet powder in a crucible for sintering treatment; crushing the sintered powder, and controlling the particle size of the powder at 100-320 meshes to obtain sintered powder;

and step three, uniformly mixing the sintered powder obtained in the step two with other raw materials according to a ratio to obtain the flux-cored powder, synchronously adding the flux-cored powder on the steel strip on line, forming and welding the outer skin steel strip added with the flux-cored powder by a roller, and annealing and reducing the diameter of the outer skin steel strip into a seamless flux-cored wire with the diameter of 1.2 mm.

As a further optimization of the scheme, the binder in the second step comprises water glass accounting for 4% -12% of the weight of the sintered powder and water accounting for 2% -8% of the weight of the sintered powder.

As a further optimization of the scheme, the filling rate of the medicine core powder is 32-37%.

The reasons for the component types and the required ranges of each component of the seamless flux-cored wire are as follows:

the seamless flux-cored wire for the high manganese steel of the LNG storage tank is a metal powder-cored flux-cored wire. The metal powder core type flux-cored wire is superior to a slagging type flux-cored wire in crack resistance and deposition efficiency and superior to a solid wire in welding manufacturability.

The powder of the invention contains 65-75% of electrolytic manganese metal, which is determined by the components of the high manganese steel plate. The manganese content in the high manganese steel plate is 20-28%, the weld components are matched with the steel plate components, and the optimal addition amount of manganese is 65-75% according to the transition coefficient of manganese in the alloy system. On the other hand, in terms of structure, when the manganese content is lower than 20%, the martensite content in the weld joint is increased, and the plasticity is obviously reduced; when the manganese content is too high, higher than 28%, weld structure segregation is easily caused. Impurities such as S, P in the weld joint are enriched near the grain boundary or are segregated to form inclusions at the grain boundary, so that the low-temperature toughness of the weld joint is damaged. Because the content of impurities such as S, P and the like in the electrolytic manganese metal is low, the Mn is added in the form of the electrolytic manganese metal.

Nickel is an austenite forming element and can improve the impact toughness of the welding seam, and a small amount of nickel can be used as a solid solution strengthening element to improve the yield strength and the tensile strength of the welding seam. The nickel element is added in the form of nickel powder, and the optimal addition amount is 8-14%.

A small amount of Si is used as a strengthening alloy element in a welding seam, the strength of the welding seam can be improved, and excessive Si can cause the reduction of the impact toughness of the welding seam. In order to ensure the purity of the welding line, the Si is added in the form of silicon powder.

Cr is mainly used for improving the corrosion resistance of a welding seam in high-manganese austenitic steel. Secondly, the low-temperature impact work of the welding line can be obviously increased by adding a small amount of Cr into the welding line, the Cr content is continuously increased, and the low-temperature impact work is not obviously improved. The Cr is added into the high-carbon ferrochrome in an optimal amount of 2-8%.

In high manganese austenite, Al has obvious effects of stabilizing austenite and inhibiting martensite transformation, corrosion resistance can be improved by adding a small amount of Al, and the Al is combined with N to form small mass points to play a role in refining grains. The Al is added in the form of alumina in the present invention.

The potassium in the potassium titanate can stabilize electric arcs, reduce splashing and optimize welding manufacturability. The content of potassium titanate added into the powder of the flux core is less, and the welding wire cannotExcellent welding manufacturability is obtained; but potassium titanate is easy to absorb moisture, and the gas hole tendency of the welding wire is increased because more potassium titanate is added into the flux-cored powder. Potassium titanate K in potassium titanate is required in the present invention₂The content of O is more than 30 percent.

The magnesite is used as an alkaline oxide, so that the welding seam can be purified, the content of S, P and other impurities in the welding seam is reduced, the risk of cracks is reduced, the oxygen content is reduced, and the impact power of the welding seam metal is improved; the excessive addition of the magnesia is combined with the acid oxide to reduce the melting point of the welding slag and increase the fluidity of the welding slag, thereby causing incomplete welding seam coverage and falling of a vertical welding bead.

C is an austenite forming element and can stabilize an austenite phase and improve impact toughness in a larger range, when the content of C is higher than 1%, the strength of a welding seam is increased and the toughness is rapidly reduced, and gases such as CO, CO2 and the like are formed in the welding process of C, and welding spatter is increased due to the excessively high content of C. The addition form of C in the invention is high-carbon ferrochrome and graphite.

In order to ensure that the powder of the medicine core is evenly distributed in the filling process and the medicine core powder has good fluidity in the drawing and reducing process of the welding wire: (1) the invention has clear requirements on the granularity of the medicine core powder. The granularity of electrolytic manganese metal, nickel powder and high-carbon ferrochrome is controlled to be 80-120 meshes, the granularity of sintering powder is controlled to be-60 meshes (namely all the sintering powder passes through 60 meshes), and the proportion of-300 meshes is not higher than 10%. (2) Introducing soda ash. The sodium carbonate has a lubricating effect, is distributed around the metal powder, reduces friction among powder materials in the wire drawing process, increases the fluidity among the powder materials, and optimizes the wire drawing process of the welding wire.

Has the advantages that:

(1) the seamless flux-cored wire for the high manganese steel of the LNG storage tank has high impact toughness and strength matched with a base metal at low temperature, and good yield ratio, and the impact energy of deposited metal of the welding wire can reach 80J in a low-temperature environment of-196 ℃; the welding wire has good welding manufacturability, is suitable for welding at various positions, has chemical components matched with the base metal, is in smooth transition with the base metal, has no cracks, and can be applied to welding of high manganese steel of the LNG storage tank.

(2) The main component of the flux-cored wire powder is electrolytic manganese metal, so that the cost of using the nickel-based welding material at the low temperature of 196 ℃ below zero in the past is greatly reduced.

(3) The seamless flux-cored wire manufacturing method reduces the air hole sensitivity of the welding wire and avoids the problem that the welding wire absorbs moisture again after being placed in a use environment for a long time.

(4) The granularity of several sintered powders is small, so that the flowability is poor, the loose loading ratio is too low, and the process of the welding wire manufacturing process is influenced. And the powder is easy to absorb moisture, and the direct addition of the powder can cause the air hole sensitivity of the welding wire to be larger. Therefore, the powder is uniformly mixed and then intensively sintered, and the raw material with proper granularity is obtained by adding the binder and then sintering, so that the flowability of the powder is improved, and the loose packing ratio of the powder of the medicine core is improved.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention.